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AnatomyGastroPart2 — Transcript

by Dr. Naveen Jalota, M.D. · 10,081 words · 1,750 segments · language en · Watch on YouTube

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0:00Hello and welcome.
0:02Let's start here today by talking about
0:06the pharynx and let's continue along
0:08from the second part of digestive.
0:11So here when we go through and we talk
0:14pharynx
0:15we can see the pharynx is going to be
0:17basically your throat. It's your throat.
0:21And the pharynx is a musculomembranous
0:25cavity. Here in this picture we can
0:26appreciate that pharynx in greater
0:29detail. So right back in here we can see
0:31is going to be the pharynx.
0:34So again it's a musculomembranous cavity
0:37that's going to be found located
0:40behind the nasal cavity
0:44behind the oral cavity
0:47and behind you can see the larynx.
0:52So dorsal to the nasal cavity, the oral
0:54cavity, and the larynx.
0:57Also communicating with them.
1:00So it is communicating with each of
1:02those cavities, the nasal cavity, the
1:03oral cavity, and the larynx.
1:06Along with those cavities it also is
1:09going to be communicating with them the
1:11esophagus below.
1:13So you could say the inferior
1:14continuation of the pharynx is going to
1:16be the esophagus.
1:21Now here when we go through and we talk
1:22functions, let's talk functions of this
1:24uh
1:26uh pharynx here. Now when we talk about
1:27the function of the pharynx, you'll see
1:29the function is going to be that it is
1:31going to behave as a passageway. It's
1:35going to function as a passageway
1:39for food and air.
1:42It will serve as a passageway for food
1:44and air
1:45routing both of them to their proper
1:47places.
1:49So its function
1:51is to
1:52allow for the passage of food, fluids,
1:55and air.
1:59This pharynx is going to get divided up
2:01into different parts. Here in this next
2:03picture you can actually see I've
2:05brought this from another area and you
2:07can see we've actually highlighted the
2:09pharynx.
2:11So here what we're going to do since
2:12we're talking digestive is we're going
2:14to talk about the oral pharynx and we're
2:16going to look at the laryngopharynx. We
2:17will leave the nasopharynx out for
2:19respiratory system because that's going
2:21to be involved with breathing. Right?
2:23Food and air
2:25uh are going to be basically food, air,
2:26and fluids passing through the pharynx.
2:28Air mostly through the nasopharynx and
2:31then food and fluids you can see right
2:33down in here. And then air obviously
2:34right down here as well. Now here when
2:36we go through and we talk let's talk
2:37oral pharynx. Oral pharynx is the
2:39pharynx the division of the pharynx
2:40dorsal to that oral cavity.
2:44Laryngopharynx dorsal to the larynx.
2:47Dorsal to the larynx posterior
2:49the larynx.
2:52Next thing we've got the inferior
2:53continuation of that pharynx we said is
2:54going to be the esophagus. When we talk
2:56about the esophagus the esophagus is a
2:58muscular tube. It's a muscular tube.
3:01It's about 10 in long. It's about 10 in
3:04long about 25 cm in length.
3:08It is collapsed. It's collapsed when it
3:12is not involved in propulsion.
3:15It's collapsed.
3:17Versus you'll see the trachea and the
3:20and the larynx that are just anterior to
3:23that esophagus they're going to be
3:24basically patent. They're going to be
3:26open and we have to maintain that open
3:28airway for breathing.
3:30Right? Esophagus is considered collapsed
3:33when it's not involved in propulsion.
3:35And this esophagus is going to run from
3:37the you'll see from this basically just
3:39inferior to that
3:42basically the throat area we'll say.
3:43It'll run from that throat area into you
3:46can see the thorax and from the thorax
3:48it'll make its way down into the
3:49abdomen.
3:52So running all the way down to the
3:53abdomen, where it will join the stomach.
3:57It joins the stomach at the cardiac
4:00orifice. It will join the stomach at the
4:02cardiac orifice.
4:06So, what is the function of the
4:06esophagus? The function of the esophagus
4:08is that it carries or it passes food.
4:11It's going to carry or it's going to
4:12pass food from the pharynx to the
4:15stomach.
4:16So, it carries or it passes food from
4:18the pharynx to the stomach, and it'll do
4:20this via peristalsis.
4:22Via peristalsis.
4:25When we talk about the esophagus then
4:27you can see peristalsis is going to be
4:30the means of
4:31propulsion here.
4:34So, here we've got also the epiglottis.
4:37Now, when we talk about the epiglottis
4:38here, you can appreciate that
4:39epiglottis. The epiglottis is a flexible
4:42spoon-shaped
4:44flap. It's a flexible, spoon-shaped
4:48flap.
4:49It's composed of
4:51elastic cartilage, if you recall.
4:54It's almost entirely covered. You'll see
4:57right up in here. It's almost entirely
4:59covered with taste bud containing
5:01mucosa.
5:07And we'll talk more about it when we get
5:09to the respiratory system.
5:11Because it's going to be
5:13allowing
5:14basically food to make its way to where
5:16it's supposed to go, and air then to
5:18make its way where it's supposed to go.
5:22Cardiac orifice then, let's check out
5:24the cardiac orifice. It's going to be
5:26found in the abdomen.
5:28It will be found in the abdomen. Here
5:30you can see this will be that cardiac
5:32orifice right inside of here. The
5:34initial segment of the stomach is known
5:36as the cardia, and then the orifice
5:38there into there is the opening
5:40basically. So, here was when we go
5:42through we talk about the cardiac
5:43orifice. So, it's going to be found in
5:44the abdominal cavity, and this is where
5:47the esophagus will join the stomach.
5:50Where the esophagus will join the
5:51stomach.
5:53And here we will have what we call the
5:55gastroesophageal
5:56sphincter.
5:58The gastroesophageal sphincter. Now, we
6:00talk gastroesophageal sphincter,
6:03you'll see what it is is a slight
6:04thickening.
6:05It's a slight thickening
6:07of the circular smooth muscle. It's a
6:10slight thickening of the circular smooth
6:12muscle.
6:15And uh just like the name says, it's a
6:17sphincter, so it's going to help
6:18regulate the passage of food from that
6:21esophagus down into the stomach, and
6:23it's going to help to keep stomach
6:25contents down inside the stomach as
6:27well. Not allowing the acid or uh
6:30basically the food to make its way up
6:31into the esophagus.
6:34So, here when we go through and we talk
6:36uh so, cardiac sphincter or
6:38gastroesophageal sphincter.
6:41Look here, or gastro uh gastroesophageal
6:43sphincter. Okay, think about that.
6:45Gastroesophageal, stomach and esophagus,
6:47you've got right inside the middle.
6:50Next then, let's look at the histology
6:52of this uh esophagus. When we look at
6:54the histology of the esophagus, here
6:56we're able to appreciate the different
6:57components, uh the different layers
6:59basically in relation to that esophagus.
7:01And we start with the mucosa, and get
7:04into the submucosa, then the muscularis
7:05externa, and then we've got the
7:06adventitia. So, here first we'll see
7:09it's uh going to contain all four basic
7:11alimentary canal layers.
7:14Now, first is the mucosa. When we talk
7:15mucosa, the mucosa we're going to find
7:17here is going to be non-keratinized
7:19stratified squamous epithelium. Right?
7:21Non-keratinized
7:22stratified squamous epithelium. We've
7:25We've been discussing that since the
7:26beginning of the semester.
7:29Then we talk submucosa. So, here you can
7:31see, again, we said non-
7:33uh non-keratinized, right? We keratin
7:35you again should remember
7:36uh why we needed here uh there versus
7:39here, why it's not needed. Okay, so
7:41non-keratinized and then stratified
7:43squamous
7:45you know it's protective and yada yada
7:47yada. And again, you can see all of that
7:49right inside of here, nice and
7:51beautifully.
7:52All right inside of there.
7:56Look at all the thick layers.
7:59Stratum basale right down inside of here
8:02and then you move it up and basically
8:04make your way up all the way up all the
8:06way up all the way up all the way up
8:08then to the corneum.
8:14You can see that nicely all the way
8:15around so so here you can see it's
8:15collapsed.
8:17Okay, it's collapsed. It's If it was
8:19actually involved in propulsion, you
8:21would see all of these layers here would
8:22be basically pushed in then.
8:25And this would be opened up widened out
8:26a bit more.
8:29So after then the mucosa,
8:31we can appreciate what we call the
8:33submucosa.
8:35Now right down inside of here, this is
8:37all submucosa.
8:40We talked submucosa. So submucosa,
8:42beneath the mucosa. Now submucosa is
8:45made up of areolar connective tissue
8:47number one, areolar connective tissue,
8:50and the submucosa is going to contain,
8:52you'll see your mucus secreting glands.
8:55The submucosa will contain mucus
8:57secreting
8:58esophageal glands.
9:02The food bolus as it passes through
9:04as the food bolus passes through, the
9:06food bolus is going to compress these
9:07glands. And when it compresses these
9:09glands, these glands are going to
9:10secrete mucus and that mucus is going to
9:13help to you can think lubricate or
9:15grease that esophageal that esophagus or
9:18the esophageal walls, allowing then that
9:20food bolus to make its way down.
9:24And that mucosa,
9:27submucosa,
9:30third then muscularis externa. Now
9:32muscularis externa, here when we talk
9:35muscularis externa,
9:38first thing I'd like you to know is uh
9:40when we talk muscular layer here,
9:42normally speaking we've seen smooth
9:43muscle everywhere. Here you're going to
9:44see you have skeletal muscle in the
9:46superior 1/3 of the esophagus.
9:49Skeletal muscle in the superior 1/3.
9:52Smooth muscle in the inferior 1/3.
9:57So skeletal in the upper 1/3. Smooth in
9:59the inferior 1/3. In the middle 1/3, a
10:02mixture of the two then. It's kind of
10:04phasing out of one and into the other.
10:06So skeletal muscle in the superior
10:08third, mixture of skeletal and smooth in
10:10the middle third, and then entirely
10:11smooth muscle in the inferior third.
10:16And then muscular layer, longitudinal
10:18and circular layers as we have seen
10:20there. And here you can appreciate those
10:21layers very very nicely.
10:25Right?
10:26Right inside here you can see the
10:27circular layer.
10:28All the fibers are running in a circular
10:29fashion.
10:31This is the longitudinal.
10:35Let's mark here too.
10:38Next up we've got the adventitia. So
10:40instead of serosa, we've got here
10:42adventitia. Adventitia is fibrous
10:44adventitia. It's composed entirely of
10:47connective tissue, fibrous connective
10:49tissue. Composed
10:52entirely of
10:54fibrous connective tissue.
10:58Let's move then down to the stomach.
11:00Next time we move down to the stomach.
11:02We talk stomach. So here you can see the
11:04food bolus
11:05is going to make its way from that oral
11:07cavity into the pharynx. Now here when
11:10it makes its way into the pharynx, you
11:11can see that's a one time we stop
11:13breathing.
11:14If we do start breathing or if we start
11:16talking, right? That opens up this
11:19passageway and that's going to cause
11:20then these components to make their way
11:22down the wrong tube we say, right?
11:24That's literally what's happening there.
11:29We don't We're We're supposed to have
11:30any of those food contents here. So if
11:32they do happen to make their way into
11:33here, it's causes to start coughing and
11:35that coughing is us expelling air. So,
11:37that expulsion of air is going to make
11:39its way up into here and help to remove
11:41whatever contents are going to be up in
11:42this area here.
11:46Next in here, let's move through then uh
11:47here you can see the food bolus then
11:49make its way down into the esophagus.
11:51Now, here you have also an upper
11:53esophageal sphincter you have to know
11:54about. So, here that upper esophageal
11:56sphincter is shut. Now, when this food
11:59bolus is going to be passed into that
12:01pharynx, here you can see that sphincter
12:04will relax and then this epiglottis is
12:06going to help to close off that entrance
12:09into the larynx while this larynx also
12:11does the same by rising.
12:13So, here you could see then the food
12:14bolus
12:15has no other way
12:17to pass because up here you got the
12:19uvula and then you got that soft palate
12:21helping to block off that entrance up
12:22into the nasopharynx. So, that's the
12:24only one pathway it could go and that's
12:26also because that upper esophageal
12:28sphincter is relaxed because if it
12:29doesn't relax, then that food bolus is
12:31going to struggle to make its way down.
12:32So, here once the food bolus does pass
12:34down,
12:35then you see it's
12:37going to contract. Now, you have to know
12:38about the pathology that you have here
12:40in relation to this upper esophageal
12:41sphincter not opening properly. This
12:44usually happens in the sixth after the
12:46sixth seventh decade of life and then
12:48this leads to that food bolus and food
12:51accumulation to start to take place
12:53within you'll see this area here leading
12:55to like a little pouch and halitosis and
12:58these other different signs and symptoms
13:00and that the patient will complain of.
13:03The signs obviously that you'll be able
13:04to see and symptoms that they'll
13:05complain of.
13:08So, here then once the food bolus passes
13:09down, it makes its way through the
13:11esophagus passing through when it makes
13:13its way to the lower half of the
13:15esophagus here then you can see the
13:16gastroesophageal sphincter is going to
13:18relax. When it relaxes, that's going to
13:19allow the food bolus to make its way
13:21down and then we talked about this
13:23peristalsis is the pathway that this
13:26food bolus is going to use to make its
13:27way down, right? The contraction and
13:30relaxation of these muscles, okay?
13:33So, here you're able to see
13:36we're going to see we've got these
13:37muscles. So, the the circular layer will
13:39be doing its basically contraction while
13:41the longitudinal layer it's kind of
13:43doing its contraction. So, you have this
13:44circular and a upward
13:46you know, downward kind of fashion
13:48happening and this is all going to be
13:49again helping to move this food forward.
13:52So, once our food bolus makes its way
13:53into the stomach then this this
13:55sphincter is going to
13:57contract not allowing the contents to
13:59make their way up. Once this food bolus
14:01makes its way down, you could see it
14:03contracts
14:04as well.
14:06So, here you can see it all in greater
14:08detail.
14:21So, let's talk stomach. When we talk
14:23stomach, the stomach is going to be
14:24found below the esophagus.
14:27The stomach is going to be
14:29the GI tract
14:32component that's
14:33expanded. It's the GI tract component
14:37that's actually expanded because the
14:40rest of the GI tract if you recall when
14:41I talked to you about the alimentary
14:42canal, you saw from that
14:45esophagus down it was just basically a
14:46slender tube. Even the small intestine
14:47is a slender tube. So, this is the one
14:49part of it where it actually widens out,
14:51you see.
14:54And then it goes back to being that
14:55small size.
14:57So, here when we talk about the stomach,
14:59the stomach is going to be about 6 to 10
15:02inches long. It's about 6 to 10 inches
15:04long.
15:05Its function is that it's a temporary
15:08storage tank. It is a temporary storage
15:10tank. And here is where
15:14the majority of chemical breakdown is
15:16Well, I actually won't say that.
15:19We're going because that's going to
15:20happen after this area here. Now, this
15:22is where I want to say we're going to
15:25have more chemical breakdown occur
15:27versus what we saw in the mouth is what
15:28I'm trying to say. In the mouth, we
15:30already had some chemical breakdown take
15:31place. Okay? So, we're not going to say
15:33it starts here because it started in the
15:35mouth. All right? We had a couple of
15:37enzymes that you're responsible for
15:38knowing about up there. Now, here in the
15:39stomach is where we're going to have a
15:42good amount take place, but then we're
15:44going to have way more chemical
15:45breakdown take place when this food is
15:47going to make its way into the duodenum
15:48and it comes into contact with
15:49pancreatic So, the stomach is going to
15:52be a storage tank. Its function is it's
15:54a temporary storage tank.
15:56And this is where chemical breakdown of
15:58proteins
16:00is going to begin.
16:01This is where chemical breakdown of
16:02proteins begins. All right? Because we
16:04saw starchy foods and we saw lipids take
16:07place inside the mouth. So, here now
16:10we're talking about breakdown of
16:11proteins begins.
16:13And also, food is going to get converted
16:16here into a creamy paste that we refer
16:20to as chyme.
16:23So, c h y m e chyme.
16:28So, here when we say that protein
16:30breakdown occurs, well, let's ponder.
16:33What do we mean by that?
16:36How are proteins being broken down here?
16:40What is it?
16:42First of all, you learned in bio
16:44uh you guys even did uh
16:47an experiment where you guys looked at
16:50the optimal pH's for your
16:53uh specific enzymes that you guys were
16:55using in bio 100 and bio 107.
16:58And you had to see whether that enzyme
16:59that you had worked better in a acidic,
17:02a basic, or a neutral pH.
17:04So, you see where we're getting to here?
17:07Acids. All right? You saw extreme uh
17:10basically acidic environment. And uh
17:14uh high temperatures are going to cause
17:19protein breakdown of carbohydrate. No,
17:20we won't say that cuz there's a proper
17:22term that we want to use there. What's
17:24that proper term that you want to use
17:25there?
17:27Very good. Very good. I knew you knew
17:31it. Very good.
17:33All right. So, here now when we go
17:34through So, that's going to be basically
17:36one way we'll see denaturation. Okay? Uh
17:40is how protein breakdown is going to
17:41occur through the acids, but then also
17:43we're going to see we're going to have a
17:45certain here as well.
17:47So, this enzyme is going to act on
17:49proteins also. So, couple of different
17:51ways that proteins are going to get
17:52broken down here. So, here now when we
17:54go through we talk regions. Let's go
17:56through and talk about the different
17:57regions of the stomach. So, the first
17:59region of the stomach that you have to
18:01know about, I told you is the cardia.
18:03So, when we talk about the cardia, the
18:04cardia is a small area.
18:06Okay, it's a small area. It surrounds
18:09the cardiac orifice.
18:11It surrounds the cardiac orifice through
18:15which food components are going to make
18:18their way in from the esophagus to the
18:21stomach.
18:23So, it surrounds
18:25the small area surrounds that cardiac
18:26orifice through which I told you before
18:29food enters the stomach from that
18:31esophagus.
18:33Next thing we've got the fundus. The
18:35fundus is going to be the dome-shaped
18:36part. It's the dome-shaped region.
18:40It's a dome-shaped part. It's the part
18:41that's tucked beneath the diaphragm.
18:43It's the part that is tucked beneath the
18:45diaphragm.
18:47It bulges superiorly.
18:50You can see there it bulges superiorly.
18:55It bulges superiorly
18:57in comparison to or you can say uh
19:02lateral from the cardia.
19:04Bulges superiorly
19:07just lateral to that cardia.
19:11Next thing we've got the body. We've got
19:12the body. The body is basically the mid
19:14portion.
19:16It's a mid portion.
19:18Leads us to the pyloric region.
19:22Leads us to the pyloric region. Here we
19:24can see the pyloric region. The pyloric
19:26region is this funnel-shaped region.
19:31Now, the pyloric region gets divided up
19:32into first you can see the pyloric
19:34antrum. The pyloric antrum is the wider
19:39more superior part or the more superior
19:42division
19:44of this pyloric region.
19:49Next thing we've got the pyloric canal.
19:51So, the pyloric canal you can appreciate
19:53now right inside of here. The pyloric
19:55canal then is the narrower part right
19:58after the antrum.
20:00The narrower part right after the
20:01antrum. Here you can appreciate the
20:03beautiful rugae, these longitudinal
20:05folds we're going to talk about.
20:09And then the last region here is going
20:11to be the pylorus, the end part, the
20:12pylorus.
20:15At this pylorus you can appreciate this
20:18pyloric sphincter.
20:20The pyloric sphincter now is not going
20:22to regulate the passage of food into the
20:24stomach as we saw up here, but it
20:26regulates the passage of food out of the
20:28stomach and into this
20:31small intestine, the duodenum.
20:35This pyloric sphincter can also have a
20:37pathology to it and this pathology
20:39usually affects the first male born
20:42child to the female and it's a genetic
20:46predisposition there. And here what
20:48happens is it causes this sphincter to
20:51basically
20:53uh
20:54to block off that passageway.
20:57It usually happens uh
20:59affects the baby the baby boy in uh the
21:02first month or second month of life.
21:04First month, I believe, or second month
21:06of life are more common fake times and
21:08the surgeon will go in then and uh
21:10obviously doctor will have to come in
21:11take a history and physical and confirm
21:13the diagnosis and
21:15then surgeon will come in and basically
21:18snip out some pieces and they goes back
21:20to basically working perfectly fine no
21:23problems and it's called hypertrophic
21:25pyloric stenosis.
21:27It's one of the names so make sure you
21:29get all the different names figured out
21:30there as well.
21:32It's another pathology here with the
21:33upper esophageal sphincter at the lower
21:34esophageal sphincter right?
21:35Gastroesophageal gastroesophageal reflux
21:38disease okay? Where we have food
21:40contents and these components making
21:41their way up into that esophagus.
21:45So you've got a pathology a different
21:47pathologies with every single one of
21:48these sphincters that you're going to be
21:49responsible for knowing about as well.
21:52Next then here we've got pyloric
21:55sphincter pyloric valve okay?
21:57So now let's talk about mesenteries in
21:59relation to the stomach. Let's talk
22:01mesenteries.
22:02Here you've got basically peritonea
22:05we've seen we've talked about peritonea
22:09there now different types of peritonea
22:11we have are mesenteries we're going to
22:12see here.
22:14We're going to talk we're going to talk
22:15we're going to check out mesenteries
22:16we're also going to look at you'll see
22:18greater and lesser omenta mesocolon as
22:21well. So here in relation to the stomach
22:22we're going to look at what's known as
22:24greater and lesser omenta. So here we
22:26can see we've got lesser omenta and then
22:30here we can appreciate greater omenta.
22:37Now greater omenta lesser omenta you can
22:39see here running from the stomach and to
22:42the stomach. So here first let's talk
22:44about lesser omenta. First let me tell
22:46you what these these mesenteries are
22:48doing. These mesenteries what they're
22:49doing is they're going to help tether
22:51the stomach to other digestive organs.
22:53They're going to help tether the stomach
22:55to other digestive organs. So lesser
22:58omenta you can see there is going to be
22:59running it runs from the liver makes its
23:02way from the liver, and it's going to
23:04come down to the lesser curvature of the
23:06stomach.
23:08The lesser curvature of the stomach. So,
23:09here when we're looking at the different
23:10parts of the stomach, right here you can
23:12appreciate the lesser curvature of the
23:14stomach. And here we can appreciate the
23:16greater curvature of the stomach.
23:20It's got a couple of curves, major
23:21curves to it.
23:26Lesser and greater curvature.
23:30So, you can appreciate now lesser omenta
23:31running from the liver, making its way
23:33down to we describe the lesser
23:36curvature, where it becomes continuous
23:38with the visceral peritoneum of the
23:41stomach.
23:43Where it'll become continuous with the
23:44visceral peritoneum.
23:46And here we can appreciate that greater
23:47omenta. Now, this greater omenta is
23:50going to run from the greater curvature.
23:51It it's going to drape inferiorly. It
23:54drapes inferiorly to cover the coils of
23:56that small intestine as you can see
23:58there. And then what it's going to do is
24:00it's going to make a U-turn. It's going
24:01to run now, let's go over to this
24:03picture here, you can see it drapes
24:05inferiorly over the
24:07it drapes inferiorly to cover the coils
24:09of the small intestine, makes a U-turn.
24:11So, it's going to run dorsally and
24:13superiorly. Runs dorsally and superiorly
24:17up to
24:19blending in with eventually, you can see
24:23that transverse mesocolon.
24:26To blend in with that transverse
24:27mesocolon.
24:29So, it's going to
24:30uh drape inferiorly to cover the coils
24:32of the small intestine, then it runs
24:33dorsally and superiorly,
24:36wrapping the spleen,
24:38wrapping the spleen and the transverse
24:41portion of the large intestine before
24:44blending in with the mesocolon.
24:46That transverse mesocolon.
24:48You can come back here and you can see
24:50it's riddled with fat.
24:53Riddled with fat,
24:55and it contains large collections of
24:57lymph nodes.
25:00You can see it here as well.
25:01A nice drawing of it.
25:08And in the cats,
25:10what you're going to do is you're going
25:12to
25:13remove this off the cats. Not now,
25:16obviously you guys aren't doing them.
25:18These are for you know, future students
25:19as well. So here what you'll do is
25:21you're going to remove this greater
25:23omenta off very nicely because it's
25:26going to end up being tucked underneath
25:28and coiled basically all in between the
25:31different coils of that small intestine.
25:33So you can't tear it.
25:35But those of you who are going to be
25:36dissecting looking at this, you've got
25:38to take it out very nicely and very
25:40gently. We want to see this. You don't
25:41want to tear it out because that could
25:43be a possible exam question. And then
25:45this one can also be another possible
25:47exam question.
25:49So greater omenta, lesser omenta. Next
25:51in here we're going to be able to
25:52appreciate the histology of the stomach.
25:55Let's talk about the histology of the
25:57stomach. So when we talk histology of
25:58the stomach, here we're going to be able
26:00to appreciate now
26:02basically these different parts.
26:05Now here we can see we've got mucosa.
26:07When we talk mucosa, mucosa here is
26:09simple columnar epithelium. And the
26:12simple columnar epithelium is composed
26:13entirely of mucus cells.
26:18Here when we go through and we talk we
26:20saw the rugae I told you about before.
26:22The rugae are going to be longitudinal
26:23folds. They're longitudinal folds of the
26:25mucosa and submucosa.
26:28Longitudinal large longitudinal folds
26:30composed of mucosa and submucosa.
26:35Then we have gastric pits. When we talk
26:37about gastric pits, these gastric pits,
26:40they're going to be found as basically
26:45little openings to the glands. And
26:47there's going to be millions of these
26:49gastric pits in quantity. So tiny
26:52openings that lead to the glands.
26:55Now, we talk gastric glands. Here we're
26:58able to appreciate now in specific
26:59detail the pit.
27:01And then here you've got the gland
27:03component. Now, we talk about the
27:04gastric glands. The gastric glands are
27:06tubular.
27:08They're tubular and they produce the
27:11stomach secretions that are called
27:13gastric juice.
27:15They produce stomach secretions that are
27:17called gastric juice. Now, when we look
27:19at these glands, they're made up of
27:20various types of cells. Now, uh the
27:24first type of cell that you have here
27:25are going to be your parietal cells. You
27:28can see you've got mucous neck cells,
27:31parietal cells, and we're going to also
27:32be able to appreciate, you can see in
27:34here, chief cells. So, they're all found
27:36in different areas you're responsible
27:38for knowing about as well. Now, when we
27:40talk about the parietal cells, the
27:41parietal cells are going to be found in
27:42the middle region. They're found in the
27:44middle region of the gland and they're
27:46scattered amongst the chief cells.
27:50They're scattered amongst the chief
27:51cells. And they will simultaneously
27:53secrete hydrochloric acid and intrinsic
27:56factor.
27:58They will simultaneously secrete
28:00hydrochloric acid and intrinsic factor.
28:03Now, the chief cells, the chief cells
28:05are going to occur mainly in
28:08the basal regions. So, you can see them
28:10here mainly in the basal regions.
28:14All right, of the gastric glands. And
28:15they're going to produce pepsinogen.
28:19Pepsinogen is going to be the inactive
28:22form of the protein digesting enzyme
28:25called pepsin.
28:31And then also, you can appreciate here
28:32enteroendocrine cells. I want you to go
28:35through and do a little research on
28:36those. So, mucous neck cells producing
28:39mucus, parietal cells I mentioned there
28:41to you guys, chief cells, and then get
28:43those enteroendocrine cells down as
28:45well.
28:46Then we'll move down into the submucosa.
28:48So moving back, here you can appreciate
28:51now the submucosa. Now between the
28:53submucosa and the basically you can see
28:57the upper part of that mucosa, you've
28:59got now this muscularis mucosae in there
29:02as well. This is a local layer
29:03of muscle there. It will allow for local
29:06movements of that small
29:08basically of that small area of the
29:10stomach. So right in here you can see
29:12that muscularis mucosae. So local
29:14movements basically right in that area.
29:17Next then you submucosa. We talked
29:18submucosa, submucosa contains your
29:20submucosal plexus.
29:23It contains your submucosal plexus.
29:28Then here we have the muscularis
29:30externa. When we talk muscularis
29:32externa, the muscularis externa is going
29:35to be made up of three layers here
29:36versus the two that we had before we've
29:39seen typically to everything. So the
29:41extra layer that you're going to have
29:43here is the oblique layer, the oblique
29:45layer.
29:47Also you're going to find here the
29:48myenteric plexus.
29:50The myenteric plexus is going to be
29:51found here as well.
29:55Then we move down to the serosa. When we
29:57talk serosa then serosa is going to be
29:59the deepest part.
30:00So here you can appreciate then the
30:02serosa.
30:05Next then we have what we call the
30:07mucosal barrier in relation to the
30:09stomach. The mucosal barrier now is
30:13going to be made up of three components
30:15that I'd like you to know about. Now
30:18basically this mucosal barrier is going
30:20to be providing protection to the
30:21stomach's wall. Now here when we go
30:24through and we talk about this mucosal
30:25barrier, the components making up the
30:27mucosal barrier are going to be number
30:28one that the stomach is going to contain
30:31a thick coating of bicarbonate.
30:34Thick coating of bicarbonate rich mucus.
30:37So stomach is going to contain a thick
30:39coating of bicarbonate rich
30:42mucus.
30:43That's going to help to battle the
30:44acidity that's going to be in there.
30:47Also, the epithelial cells the
30:49epithelial cells are going to have tight
30:51junctions in between each other.
30:53And this is one allow anything to seep
30:54through.
30:55Tight junctions.
30:58And then number three we have you'll see
31:00the damaged cells. When these damaged
31:02cells are damaged they get shed and
31:04they're replaced.
31:07So these three components of the mucosal
31:10barrier are going to help us to combat
31:11that acidic environment inside the
31:13stomach.
31:17Let's move then and let's move down and
31:20we'll move down then to the small
31:23intestine.
31:25Now when we move down to the small
31:26intestine, okay, we'll check out the
31:28various components there. So here let's
31:30focus on the gland and the gland in here
31:32you can appreciate those various cells.
31:35So make sure you have down exactly which
31:37one is doing what.
31:39You'll be responsible for all their
31:40functions.
31:43And then here we talked about
31:45the three components of
31:49the mucosal barrier that helped the
31:50stomach from
31:52being self-digested.
31:58So let's talk then small intestine. So
32:00here the small intestine is highlighted
32:02first component you can see there,
32:04second component we've got right down in
32:06here and then here we've got the third
32:07component. So when we go through we talk
32:09about the small intestine we'll check
32:10out the small intestine and the
32:11associated organs. So when we talk small
32:13intestine the small intestine is going
32:15to be the body's major digestive organ.
32:18It's the body's major digestive organ.
32:20Now here I'd like you to know that it's
32:22going to extend and it's going to extend
32:24from that pyloric sphincter all the way
32:26down to the ileocecal valve. All the way
32:30down to the ileocecal valve.
32:32The function of the small intestine is
32:34number one absorption.
32:36Absorption.
32:38Here we'll see
32:39where This is where our food The main
32:42function is going to be basically
32:44absorption, where food is going to make
32:45its way from this
32:47the lumen all the way into the blood.
32:50And also we're going to see digestion.
32:53Mechanical digestion already occurred.
32:55Chemical digestion is what we're going
32:57to see here. So, functions include
32:59absorption and digestion.
33:02You have to have digestion obviously
33:03first in order to have absorption.
33:09So, digestion then, which is going to be
33:12we said chemical.
33:16Now, we talk uh
33:18regions, so duodenum,
33:19jejunum, and ileum. All three different
33:23divisions. Duodenum, jejunum, and ileum.
33:28And then here you can see
33:31duodenum is about 10 in.
33:35Jejunum, anywhere from 1 to 1.7 m.
33:40And then ileum you can see anywhere from
33:421.6 to 2.7 m.
33:45So, here when we go through and we talk
33:46about the different divisions, the
33:48duodenum is the first part. The duodenum
33:49is immovable. It curves around the head
33:52of the pancreas. We saw that there. It's
33:54about 10 in long as we described.
33:57Here in relation to this
33:59duodenum, we're going to be able to
34:01appreciate. So, here you can see
34:03everything in order.
34:04So, we are right down inside of here.
34:06Here's that pancreas.
34:08Okay? So, here now what we can
34:10appreciate is the hepatopancreatic
34:13ampulla. This hepatopancreatic ampulla
34:16is a bulb-like point. It's a bulb-like
34:19point that opens into the duodenum.
34:23And it contains, you can see, the bile
34:25duct. It contains the bile duct, and it
34:29contains the main pancreatic duct.
34:34So, they're both going to
34:36allow secretions from
34:38these two organs and this organ to make
34:39their way into that
34:41small intestine, into the duodenum.
34:45So, here when we go through and we talk
34:47uh next segment, the next segment then
34:48is going to be jejunum. So, right here
34:50is where the jejunum picks up from. So,
34:52coming back here, you can see then the
34:54jejunum. Now, the jejunum is going to be
34:58about uh
34:598 ft long and it extends from the
35:01duodenum to the ileum.
35:04So, it's a part of the small intestine
35:05after the duodenum, extends from the
35:07duodenum to the ileum.
35:10Ileum then
35:11is about 12 ft in length. The ileum
35:14joins that large intestine now. It's
35:17going to join the large intestine right
35:19here at the ileocecal
35:22valve.
35:23Ileocecal valve, the next valve that
35:25you'll have to know about.
35:30So, let's look at the histology. The
35:31histology is highly adapted
35:35for nutrient absorption.
35:37It's highly adapted for nutrient
35:39absorption.
35:40So, when we talk about now the
35:41histology, you'll see here we've got
35:44mucosa and the mucosa, you've got
35:47epithelium. The epithelium is simple
35:48columnar absorptive cells.
35:53Simple columnar absorptive cells.
35:56Now, when we talk about
35:58the mucosa, we're going to be able to
35:59appreciate here circular folds. The
36:01circular folds are going to be these
36:04deep
36:05permanent folds of the mucosa and the
36:08submucosa.
36:10Also appreciated here are villi.
36:13You can see the villi.
36:16And these villi are going to be
36:19finger-like projections
36:22of the mucosa.
36:24They're usually over a millimeter in
36:27height.
36:28Usually about over a millimeter in
36:29height.
36:34And in relation to the
36:37villi, we've got what we call lacteals.
36:40You can appreciate the lacteals. The
36:42lacteals, they're going to be these wide
36:46lymph capillaries. They're wide lymph
36:49capillaries.
36:52And they're going to be responsible for
36:53absorbing fats.
36:56Next thing we have our intestinal
36:58crypts.
36:59The intestinal crypts, they're also
37:02known as the crypts of Lieberkühn.
37:05Also known as the crypts of Lieberkühn.
37:08They are basically tubular glands. They
37:11are tubular glands that are found
37:15on the mucosa. So, tubular glands found
37:18on the mucosa between the villi.
37:22In between the villi.
37:26Also appreciated here are going to be
37:28microvilli. So, we'll zoom in on one
37:31one aspect of the villi. And here we can
37:33appreciate microvilli. And we talk about
37:35microvilli, microvilli are going to be
37:37exceptionally long. They're densely
37:40packed
37:45and forming the brush border. They
37:47contain certain brush border enzymes.
37:55Then we move down to the submucosa. Now,
37:57we move down into the submucosa, you can
37:59appreciate now in the submucosa, first
38:02it's typical areolar connective tissue.
38:04It is typical areolar connective tissue.
38:08And here you can appreciate now the
38:10lymphoid follicles.
38:14We're going to find here lymphoid
38:15follicles. We're going to find here also
38:17certain glands. Depending again in which
38:19part of that small intestine we're at.
38:21So, if we're in the duodenum, we're
38:22going to find duodenal glands. Here you
38:24can see a nice example of a duodenal
38:26gland,
38:27aka Brunner's glands, aka Brunner's
38:30glands, and they produce an alkaline
38:33bicarbonate-rich
38:35mucus. They produce an alkaline or a
38:38bicarbonate-rich mucus, and what that
38:41does is it's going to help to neutralize
38:44that
38:45chyme that's coming that highly acidic
38:48chyme that's coming from the stomach.
38:52So, duodenal glands, Brunner's glands.
38:55And then we have Peyer's patches.
38:57Peyer's patches, they're also called
39:00aggregated lymphoid follicles.
39:03Also called aggregated lymphoid
39:05follicles.
39:06And they're going to be found in
39:09an increased abundance towards the end
39:12of the small intestine.
39:18So, lymphoid follicles,
39:21increased in abundance towards the end
39:23of the small intestine, because we're
39:25going to have a huge amount of bacteria
39:28that has to be prevented from entering
39:29the bloodstream there. And that's what
39:31again these lymphoid
39:33the lymphoid tissue and these lymphoid
39:34follicles are going to help to do.
39:38And then moving back out, you're going
39:39to be able to appreciate then
39:41we can see the muscularis.
39:43Muscularis is going to be typical
39:46bi-layered. So, circular layer,
39:48longitudinal layer. Typical bi-layered.
39:51And then we can appreciate the serosa.
39:53The serosa is going to be the visceral
39:55peritoneum, visceral peritoneum.
40:01Next, we can move over to the liver.
40:03We move over to the liver, then the
40:05liver is going to be an accessory organ.
40:08So, we've basically
40:11now we're stopping off from the small
40:12intestine, moving to the accessory
40:13organs, and we'll come back and we'll
40:15uh, take care of the large intestine,
40:16right? Instead of just going from the
40:17small intestine right to the large
40:18intestine. So, we'll take care of these
40:20organs which are found
40:21right near here. So, we'll get these
40:23here taken care of and then we'll take
40:25care of the rest of that
40:26uh,
40:27GI tract. So, the accessory organs
40:30first, the liver. We talk about the
40:32liver, the liver is going to be
40:33associated with the small intestine.
40:35It's function, it has many metabolic and
40:37regulatory roles. I want you to go
40:39through and read all about that liver
40:40and get a thorough understanding of what
40:42that liver does. It's a very important
40:44organ. Now, I'll tell you here just a
40:45couple of uh,
40:47just a couple of quick functions here,
40:49but again, you need to go through and
40:50read it and understand it fully. Here
40:52you'll see it has a lot of metabolic and
40:53regulatory roles. That's what I want you
40:54to understand. Also, it's going to
40:56produce bile. It will produce bile for
40:58export to the duodenum.
41:00What else it's going to do is it's going
41:02to filter. It's going to filter and it's
41:03going to process nutrient-rich blood
41:06that gets delivered to it. It's kind of
41:08like, um,
41:11customs.
41:13When we come in, they want to check your
41:14baggage. That's what this is going to
41:16do. Whatever comes into our body, okay,
41:18if it gets, basically absorbed through
41:20the digestive tract,
41:22metabolism, first-pass metabolism is
41:24going to be through the liver. You'll
41:26learn more about that when you get to
41:27pharmacology.
41:30So, here, in case you want to bypass
41:32that route, we give IV then.
41:34Okay?
41:35And another source of delivering
41:37medication is going to be inhalation.
41:39So, we've got a lot of different methods
41:40of getting things in. So, here when we
41:42talk liver, it's going to filter and
41:45process nutrient-rich blood that gets
41:46delivered to it. The liver is going to
41:48get divided up. It's going to get
41:49divided up into four different lobes.
41:51The first two main lobes you can
41:52appreciate right off the bat are going
41:53to be the right lobe. The right lobe is
41:55the largest lobe. It's visible from all
41:58different sides of that liver's view.
42:02And then here you can see the left lobe
42:05of the liver. It's smaller in size
42:07compared to the right lobe. And the two
42:09are separated from each other.
42:11We're going to see, thanks to this
42:13falciform ligament.
42:15But before we check that out, let's talk
42:16about the posterior aspect where where
42:19we are able to appreciate the next two
42:21lobes. So here you're able to appreciate
42:23the caudate lobe and the quadrate lobe.
42:27Caudate lobe and quadrate lobe, much
42:29smaller in size. Caudate, superior.
42:33Quadrate, on the inferior aspect.
42:37Right next to the gallbladder.
42:40Now going back to the interior aspect,
42:42you can see the falciform ligament. It's
42:44a mesentery.
42:46It separates the right and the left
42:47lobes anteriorly.
42:50And it suspends. It's going to suspend
42:53that liver. It's going to suspend the
42:55liver from the diaphragm, which is going
42:57to be right above it.
43:00And the anterior abdominal wall.
43:03And the anterior abdominal wall.
43:07Then here you can see the continuation
43:09of that falciform ligament is going to
43:11be the round ligament of the ligamentum
43:13teres.
43:14The round ligament of ligamentum teres
43:16is a fibrous remnant of the fetal
43:19umbilical vein.
43:21So I want you to go through, read about
43:22that, and make sure you understand that
43:24there as well.
43:27Because then you have to put it together
43:28when it comes to heart.
43:31So I'm telling you fetal
43:34umbilical vein remnant. So I want you to
43:36go through, read about it, and see what
43:37it's going to be doing. You could be
43:38asked that there as well.
43:43Very important during our embryonic
43:45development.
43:46Right when we breathe, we take our first
43:48breath, everything switches off.
43:51And basically when we're born, pressure
43:52changes and we take our first breath,
43:54right? A lot of changes take place.
43:58So next that we have the common hepatic
44:00duct. So let's do this. Let's look at
44:02this in better detail. So let's see
44:05here.
44:06Here we can see now we've got first our
44:08common hepatic duct. The common hepatic
44:10duct I like you to know is a large duct.
44:12It's a large duct that's going to be
44:14formed from several hepatic
44:17bile ducts, basically.
44:21Through which bile is going to pass
44:24and make its way out of the liver. So
44:26here you can see these right and left
44:27hepatic ducts.
44:29And they're going to come together and
44:30when they come together they're all
44:31going to give rise to this common
44:32hepatic duct.
44:34The common hepatic duct then collects
44:35all from all these various components.
44:38These various ducts that are all
44:41allowing the bile to make its way out.
44:43And this bile is going to accumulate
44:44into the common hepatic duct. The common
44:46hepatic duct then you can see is going
44:48to join it'll blend with that cystic
44:50duct and they're going to give rise to
44:51this bile duct.
44:55So it travels downward towards the
44:57duodenum.
44:59The common hepatic duct does. It fuses
45:01with the cystic duct.
45:04That's draining the gallbladder.
45:07To give rise to the bile duct. Then the
45:09bile duct is going to take all the bile
45:14and dump it off into
45:16the duodenum.
45:21Let's look at the histology here in
45:22relation to then our liver.
45:25So here when we look at the histology in
45:27relation to our liver, here we're able
45:29to appreciate basically the lobules. So
45:32here we can see the lobules. What we'll
45:34do is we'll move over to this view here.
45:36In this view here we're able to
45:38appreciate now the lobules in greater
45:40detail. Here what we'll do is we'll zoom
45:42in on the one lobule and we can
45:44appreciate that one lobule in fuller in
45:46full on great detail. Here we could zoom
45:48in on that then in
45:50even greater detail and have a full idea
45:52of what is happening. So here when we
45:54look at the lobules, these lobules are
45:56actually sesame seed sized
46:01structural and functional units of the
46:02liver.
46:04They're hexagonal in shape. You can see
46:06that there.
46:08And what they are made up of, they
46:10consist of basically plates of liver
46:14cells. And you can see that right in
46:15here.
46:19Stacks
46:20or plates
46:22of liver cells.
46:24And you can see space in between.
46:27Liver cells, liver cells, space, liver
46:29cells, liver cells, space, liver cells,
46:30liver cells, space, liver cells, liver
46:32cells, liver cells, space. So, you've
46:33got that pattern all running through.
46:36The liver cells are hepatocytes.
46:38Hepatocytes, your liver cells. And you
46:40can see they are organized like bricks.
46:45And then here we can appreciate the
46:46central vein. Central vein is found at
46:48the center of each
46:50of these lobules.
46:51Then central vein runs in the
46:53longitudinal axis of the lobule.
46:57This vein is going to collect basically
47:01blood. And it's going to drain this
47:03blood then.
47:05It's going to drain this blood, you can
47:06see, to the hepatic vein.
47:09To the hepatic vein.
47:15Then you have your portal triads. You
47:18can see here on the corners of the
47:20hexagonal sinusoi- uh the hexagonal uh
47:24uh lobules, you can appreciate basically
47:27these
47:28triads.
47:30So, here the triads when we talk, here
47:32we've got basically your portal triads.
47:34These triads are going to be presenting
47:36with three basic structures.
47:42And these three basic structures are
47:43going to include, number one, a branch
47:45of the hepatic artery.
47:47When we talk about the hepatic artery,
47:48it's going to be responsible for
47:49bringing in oxygen-rich blood. And that
47:53oxygen-rich blood is going to be used by
47:55all these hepatocytes so they can
47:57perform their functions.
47:59Then you are going to see you can
48:01appreciate here
48:05the a branch of the hepatic portal vein.
48:08A branch of the hepatic portal vein.
48:11Now, these veins, what they do is
48:12they're bringing in that nutrient-rich
48:14blood
48:15from the digestive tract. They bring
48:17this nutrient-rich blood in from the
48:18digestive tract, so we said that the
48:21liver can process it. And here is how
48:23then those hepatocytes are going to come
48:25into contact with it, so they could do
48:26what they need to do. They're kind of
48:28like a you can think customs
48:31department.
48:32All right, they need to inspect
48:33everything that comes into the body.
48:38Okay, these hepatocytes, so what's going
48:39to help bring everything in is going to
48:41be this pathway.
48:43The hepatic portal circulation we're
48:45going to see.
48:47So next in here we're going to be able
48:49to appreciate the bile duct. The bile
48:51duct then is going to be responsible for
48:54removing bile that gets made inside the
48:56liver. And so you can see here the blood
48:58we've talked about is going to be
48:59passing through this way.
49:01Bile is going to be moving in the
49:03opposite direction.
49:06Moving in the opposite direction.
49:10So here you can appreciate your
49:12sinusoids. These sinusoids
49:16they're all basically enlarged leaky
49:19plates you can think of. They are
49:21enlarged leaky plates in between the
49:23hepatocyte plates.
49:29And within these cells you can
49:30appreciate these Kupffer cells, your
49:34hepatic macrophages or your stellate
49:37cells, whatever you want to call them,
49:39same name for basically the same for
49:41this
49:42cell. They are basically spider-shaped
49:46hepatic macrophages.
49:49Spider-shaped hepatic macrophages, and
49:52they form part of the sinusoidal walls.
50:01And here we can appreciate the
50:02gallbladder.
50:04And we talk about the gallbladder.
50:06The gallbladder, you can see a nice view
50:08of that gallbladder right inside of
50:09here.
50:10The gallbladder is a thin-walled,
50:13green, muscular sac,
50:17about 4 in long.
50:21Its function is that it stores bile.
50:24It's going to store bile that's not
50:26immediately necessary for digestion.
50:34This bile gets concentrated here. So, it
50:36concentrates the bile
50:38by absorbing
50:40some of its water and ions.
50:44So, whenever digestion is not occurring,
50:47this hepatopancreatic ampulla and the
50:49sphincter are going to be basically
50:50shut. The bile gets produced by the
50:53liver. The bile is going to keep coming.
50:55The bile is going to keep getting
50:56produced because the liver is not going
50:58to stop producing it. So, it keeps
51:00getting produced, it keeps getting
51:01produced, it keeps getting produced, and
51:02it keeps getting produced, it keeps
51:03stacking up, it keeps stacking up, it
51:05keeps stacking up. And then, where is it
51:06going to go? It's going to start filling
51:08up into here. And that's how you're
51:10going to see your gallbladder is going
51:12to get filled with bile.
51:15And then, the bile is going to just keep
51:17filling up, keep filling up, keep
51:18filling up, and then it'll get used. And
51:20then, it'll empty it out, and then we
51:22start refilling again. How are we going
51:23to empty it out? We're going to get into
51:25that into physiology. You're going to
51:27see there's a hormone called CCK,
51:28cholecystokinin, that's going to come
51:29in, and it's going to cause gallbladder
51:31contractions to occur. While it causes
51:32gallbladder contraction to occur, it's
51:34going to cause other events to occur as
51:35well.
51:36So, when you see gastrointestinal
51:38physiology, there's going to be a lot of
51:39hormones you're going to have to
51:40understand, and basically all these
51:42different
51:44events that are going to be taking place
51:45in the different organs at the same
51:46exact time.
51:48Uh we're phenomenal. We're awesome. Our
51:49bodies are engineered very, very
51:52beautifully.
51:57So, let's move then. We took care of the
51:59cystic duct. We've already seen that.
52:00Nothing there draining the gallbladder.
52:03Let's move to the pancreas then. So,
52:04here you can appreciate this beautiful
52:05pancreas. I told you you have to know
52:07annular pancreas there as well.
52:09So, here when we talk pancreas, soft
52:11tadpole-shaped gland, mixed gland we
52:14talked about, extends across the
52:16abdomen.
52:21Extends across the abdomen.
52:24Abutting the spleen.
52:26They say the tail
52:28tickles the spleen, basically.
52:32So, the pancreas is encircled by the
52:35C-shaped
52:36duodenum of the small intestine.
52:40Most of this organ is retroperitoneal.
52:43It's going to be found located behind
52:45the peritoneum. Since it's
52:47retroperitoneal, if it elicits pain,
52:49it's going to elicit pain to the back.
52:51These patients, if they have uh
52:53pancreatic pain, they'll complain of
52:54back pain.
52:57And people will write them off as
52:58saying, "Oh, maybe they're here for uh
53:00you know, pain meds."
53:02And uh you've got to work them up.
53:04You've got to find out what's going on
53:05unless they actually uh you know, have a
53:06history, but you got to check it out and
53:08find out what uh you know, the problem
53:09is, especially with somebody coming in
53:11complaining of back pain. So, you've got
53:13to really work it up to see what you
53:15have going in there.
53:17So, uh most of it's retroperitoneal. And
53:19it's going to be lying deep to the
53:21greater curvature of the stomach. It'll
53:22be found lying deep to the greater
53:24curvature of the stomach because the
53:24stomach's greater curvature is going to
53:26be round about here.
53:29And the esophagus
53:30and lesser curvature will be like about
53:32in here.
53:36Next function. It's an It's It's an
53:38accessory digestive organ.
53:39It produces enzymes. So, we're talking
53:41digestive. Now, we already did
53:42endocrine, so you got to know all that
53:43already.
53:44It breaks down all categories of food
53:47stuff
53:49that are going to get delivered to the
53:50duodenum.
53:54So, when you talk functions, it's
53:56enzymes are going to behave like
53:57biological scissors.
53:59They're biological scissors. They go and
54:01chop up everything.
54:05So,
54:07endocrine and exocrine. Endocrine we've
54:09talked about glucose and we talked about
54:10insulin. Glucagon and insulin, so make
54:12sure you've got that down there. Here
54:13you're going to see amylase, lipase,
54:16and so forth. So, various enzymes such
54:19as these different aces.
54:20Now, here you can see the main
54:22pancreatic duct. The main pancreatic
54:23duct you can see is going to be
54:26centrally located. It is centrally
54:29located. And this main pancreatic duct
54:31is going to drain pancreatic juice.
54:33It'll drain pancreatic juice from that
54:35pancreas
54:37right into, you can see along with bile
54:39into that small intestine.
54:42So, it fuses with the bile duct just as
54:45it enters into the duodenum.
54:47And here you can see the accessory
54:50pancreatic duct. This is This accessory
54:51pancreatic duct is going to empty just
54:54proximal.
54:56It'll empty
54:58directly into the duodenum proximal to
55:01the main duct. Proximal to the main
55:03duct.
55:08So, let's throw this pancreas under the
55:10microscope.
55:11Here we can appreciate the acini.
55:15So, here we can see
55:16acinar cells.
55:18These acinar cells are within the
55:19pancreas. They're clusters of secretory
55:21cells. Basically, these acini are
55:23clusters of secretory cells, acinar
55:25cells.
55:26And these acinar cells are going to be
55:27found surrounding these ducts. Found
55:29surrounding these ducts.
55:33And they contain zymogen granules.
55:39They contain zymogen granules. These
55:41zymogen granules you can appreciate
55:42right inside of here are going to be
55:45containing digestive enzymes called
55:49zymogen,
55:51which they will manufacture.
55:54So, here you can see then into the ducts
55:56cuz this is the exocrine component.
55:59The secretions are going to make their
56:01way into this
56:03duodenum.
56:05And inside the duodenum we've got
56:06inactive enzymes
56:08that will eventually become active.
56:12And a lot of these enzymes you can see
56:14here, okay? They're inactive enzymes
56:17that are going to be coming from the
56:17pancreas. These inactive enzymes, what
56:19they do is they're going to come in
56:20here, they're going to activate
56:22further enzymes and assist basically
56:25with the rest of digestion.
56:28So, here when we go through and we talk
56:30uh
56:32acini, we've got main pancreatic duct,
56:34okay? So, here we can see then we're
56:36going to have amylase,
56:39okay? Lipases,
56:43okay? And other enzymes I want you to go
56:45through and know about coming from the
56:47pancreas.
56:49So, I want you to go through and get the
56:50rest of these enzymes down from the
56:52pancreas as well. So, to make physiology
56:54uh much easier for you, you already know
56:55them from anatomy and all you have to do
56:57is learn and see how they're going to
56:58actually function when you get to
56:59physio.
57:02Next, now let's move to the large
57:03intestine. Let's talk large intestine.
57:09So, we talk large intestine, couple of
57:12uh good views here, beginning and the
57:13end or basically the whole thing and
57:15then you can see the beginning in here
57:16very nicely and then the end you can see
57:18here nicely. Let's see here, same thing
57:20we can see now. We talk large intestine,
57:22it uh frames the small intestine on
57:26three sides.
57:30Large intestine extends from the
57:33ileocecal valve to the anus. Extends
57:35from the ileocecal valve to the anus.
57:38The function of the large intestine is
57:40to absorb most of the remaining water.
57:43It's to absorb most of the remaining
57:45water
57:46and form indigestible
57:49I'm sorry, its function is to absorb
57:52remaining water
57:55from any indigestible food residues.
57:59To absorb remaining water from these
58:01indigestible food residues.
58:03It's also going to store and it's going
58:06to store these residues temporarily.
58:10And then eliminate them from the body in
58:12the form of feces.
58:15Another function, large intestine is
58:17going to synthesize
58:19K and B vitamins.
58:26Regions, let's go to the different
58:28regions of the large intestine. So, the
58:30first region we have is going to be the
58:31cecum. The cecum is the sac-like
58:36the sac-like
58:39initial segment of the large intestine.
58:42It's found lying below the ileocecal
58:45valve.
58:50We're able to appreciate the vermiform
58:52appendix. The vermiform appendix
58:55shooting off of that cecum.
58:57And it's a blind worm-like
59:06blind worm-like structure
59:10that plays a role we believe in body
59:13immunity.
59:17You get Peyer's patches here and then
59:19here you can see this here, so it's all
59:21there to help benefit the massive
59:23quantity of bacteria that's going to be
59:25found in this area here.
59:29Next then is the colon.
59:31The colon
59:32is going to have several distinct
59:34regions we're going to go through and
59:36we're going to check out.
59:38So, we talk about the colon. The colon
59:39you can see here first the ascending
59:41colon.
59:42Ascending colon travels up the right
59:44side of the abdominal cavity
59:47towards the level of the right kidney.
59:51Towards the level of the right kidney.
59:53And then here you can see it'll turn and
59:56as we turn we encounter the right colic
59:59flexure, the hepatic flexure. This right
1:00:01colic flexure is this basically right
1:00:03angle turn. It's a right angle turn from
1:00:06the ascending to the transverse colon.
1:00:09Transverse colon
1:00:12name
1:00:13transverse colon because it's going to
1:00:16be found
1:00:17running transverse. It travels
1:00:19transverse across the abdomen.
1:00:26Becoming then the left colic flexure
1:00:28which leads us to the descending colon.
1:00:30So, left colic flexure the hepatic
1:00:32flexure
1:00:33is going to be
1:00:36the area where the transverse becomes
1:00:38the descending.
1:00:41The descending runs down the left
1:00:44side of the abdomen where the ascending
1:00:46was running up the right side up the
1:00:48uh
1:00:50This is all getting too much. So, the
1:00:51ascending we saw running up the right
1:00:53side of the abdomen.
1:00:55The descending running down the left
1:00:57side of the abdomen. Running down the
1:00:59left side of the abdomen.
1:01:01So, from the transverse left colic
1:01:04flexure
1:01:05Okay, the splenic flexure down to the
1:01:07descending colon which runs down the
1:01:09left side of the abdomen which then
1:01:11becomes sigmoid.
1:01:12Sigmoid anything S-shaped sigmoid.
1:01:16So, sigmoid colon
1:01:17leading us to the rectum which then
1:01:19leads us to the anal canal.
1:01:24S-shaped inferior part of the descending
1:01:26colon. This is where the colon enters
1:01:28into the pelvis then.
1:01:31This is where the colon enters into the
1:01:32pelvis.
1:01:34The rectum
1:01:36is in the pelvis. It's in the pelvis at
1:01:38the level of the third sacral vertebra.
1:01:41At the level of the third sacral
1:01:43vertebra.
1:01:46Inside of there we can appreciate the
1:01:47rectal valves. So, let's look at these
1:01:49rectal valves.
1:01:51So, here then we're able to appreciate
1:01:53those rectal valves.
1:01:56Oh.
1:02:04Let's see these rectal valves right
1:02:06inside of here.
1:02:08You can see here's one.
1:02:10Here's another and here's a third. So,
1:02:12we talk rectal valves, there's three.
1:02:14They're lateral curves or bends.
1:02:18And they're represented internally
1:02:21as transverse folds.
1:02:24They're represented internally as
1:02:26transverse folds.
1:02:29And what they do is they allow us to
1:02:30pass fecal material or they're going to
1:02:32allow us to pass gas without passing
1:02:35fecal material.
1:02:36They will allow us to pass gas without
1:02:39passing fecal material.
1:02:43So, moving back to the outside.
1:02:45Right inside of here.
1:02:48The rectum then leads us to the anal
1:02:49canal, the last segment of the large
1:02:52intestine.
1:02:53It's about 3 cm long, so it's very
1:02:56small. It's about 3 cm long.
1:02:58And inside here you're going to be able
1:02:59to appreciate the anal sphincters.
1:03:03Internal
1:03:04anal sphincter.
1:03:06Okay, we can see here and then the
1:03:07external anal sphincter there as well.
1:03:11And then here we've got the anus. The
1:03:13anus is going to be the opening
1:03:16to the body's exterior.
1:03:21Then moving back out, we can appreciate
1:03:22these other structures. Other structures
1:03:24you can appreciate here are going to
1:03:25include number one, taenia coli. You can
1:03:28see the taenia coli. Taenia coli, it's
1:03:31going to be basically bands of smooth
1:03:33muscle.
1:03:35They're bands of smooth muscle.
1:03:39You can see found on both sides of that
1:03:41uh intestine.
1:03:43And what this does, it helps to kind of
1:03:45uh create this uh nice tight
1:03:51kind of nice tight uh taut over that
1:03:54large intestine. And when it creates
1:03:56that nice tight uh
1:03:59uh taut over the uh large intestine, you
1:04:01can see what it creates is it creates
1:04:02these haustra, these uh these uh
1:04:05puckerings, these uh pocket-like sacs.
1:04:09So, these pocket-like sacs are caused by
1:04:11the tone of that taenia coli.
1:04:16And then we can appreciate here these
1:04:18epiploic appendages. These epiploic
1:04:22appendages, what they are, they're
1:04:24basically small fat-filled pouches.
1:04:28They're small fat-filled pouches of
1:04:31visceral peritonea
1:04:34that's going to hang from the surface of
1:04:36the large intestine.
1:04:43And then here we've got mesentery in
1:04:46relation to the large intestine, but
1:04:48here let's talk mesentery we can see in
1:04:50relation to the small intestine as well.
1:04:53So, coming back here,
1:04:57you're able to appreciate mesentery
1:05:00in relation to the small intestine. All
1:05:03tethering again, keeping everything
1:05:05tethered to the back wall. So, large
1:05:08intestine,
1:05:09we can appreciate here.
1:05:12Okay? We saw greater omenta, transverse
1:05:15mesocolon I mentioned to you guys there.
1:05:17And then here we're going to be able to
1:05:18see also
1:05:23sigmoid mesocolon.
1:05:26So, transverse mesocolon and then
1:05:28sigmoid mesocolon basically you can see
1:05:30all in here. All mesentery right inside
1:05:32of here as well.
1:05:33So, transverse mesocolon surrounding the
1:05:35transverse colon.
1:05:38All up in here.
1:05:40Sigmoid
1:05:41all around the sigmoid colon.
1:05:44And also want to mention to you
1:05:45bacterial flora inside of this large
1:05:46intestine.
1:05:48In the large intestine we have bacterial
1:05:49flora that's bacteria that's found in
1:05:52the GI. And what they do is they
1:05:54colonize the colon the bacteria does.
1:05:57And what it does it metabolizes
1:06:00some host derived molecules.
1:06:03And they'll metabolize some host derived
1:06:05molecules and ferment some of the
1:06:08indigestible carbohydrates.
1:06:13Bacteria is going to help synthesize B
1:06:14complex vitamins and vitamin K.

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