Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

COT pt. 2 > Lecture & Lab: GI Anatomy and Organization > Flashcards

Lecture & Lab: GI Anatomy and Organization Flashcards

1
Q

Bolus

A

a lump of chewed and swallowed food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Chyme

A

bolus + stomach juices “a liquefied bolus”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Feces

A

undigested remnants of chyme (once chyme enters the colon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Foregut

A

Pharyngeal gut

Foregut proper – starts at esophagus, stomach, proximal duodenum
- Organs that bud off: Lung bud, liver, gallbladder, pancreas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Midgut

A

Duodenum after bile duct, jejunum, ileum, cecum, ascending colon, proximal (right) 2/3 transverse colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Hindgut

A

Distal (left) 1/3 transverse colon, descending colon, sigmoid colon, rectum, upper anal canal (to pectinate line/cloacal membrane)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the arterial supplies of the foregut, midgut, and hindgut?

A

They are divided based on the specific arterial supply

Foregut- celiac trunk
Midgut- superior mesenteric artery
Hindgut- inferior mesenteric artery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Mucosa

A
  • Protection (SSNK)
  • Absorption and/or secretion (SCE)
  • Movement of villi
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Submucosa

A
  • Surface area
  • Glands
  • Innervation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Muscularis Externa

A
  • Innervation
  • Peristalsis
  • Mechanical breakdown
  • Sphincters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Serosa/Adventitia

A
  • Protection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Mesentery

A

very thin double sheet of serosa, and in between it is the root for all of the blood vessels, lymphatic vessels, and nervous supply.

GI tube is not floating and not connected to the body wall.

  • A double-fold of visceral peritoneum
  • Connective tissue surrounded by a double layer of serous membrane (mesothelium!)
  • Contains blood vessels, nerves, and lymphatic vessels that travel in the peritoneal cavity from their branch-point to the GI tract
  • Peritonitis – inflammation of the peritoneum (can be caused from appendicitis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Adventitia or Serosa?
Esophagus, Stomach, Duodenum, Jejunum & ileum, Colon, Lower rectum and anal canal

A
  1. Esophagus: mostly adventitia
  2. Stomach: serosa
  3. Duodenum: mostly adventitia
  4. Jejunum & ileum: serosa
  5. Colon: varies
  6. Lower rectum and anal canal:
    adventitia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Enteric nervous system – the “gut brain”

A

Controls the following:

  • Stretch receptors
  • Secretion of digestive juices (stomach, liver, pancreas)
  • Peristalsis
  • Control of sphincters
  • Defecation
  • Local blood flow
  • Immune system interactions
  • Derived from neural crest cells
  • Postganglionic fibers of the sympathetic division of ANS
  • Cell bodies and fibers of postganglionic parasympathetic division
  • Fibers from local connections between cells (local reflexes exclude the CNS)
  • Regulates gut peristalsis, blood flow, glandular secretions, and hormonal secretions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Myenteric (Auerbach’s) Plexus

A

regulates peristalsis

sandwiched between the ICL and OLL of the musclaris externa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Submucosal (Meissner’s) Plexus

A

regulates glandular secretions and movement of villi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Enteroendocrine cells (EC)

A

epithelial endocrine cells of the gut

Has the ability to sense the presence of chyme and they release NTs (like 5HT/serotonin) which are sensed by the Myenteric and Submucosal Plexi.

Orchestrates local reflexes like peristalsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the two pathways that neural crest cells may take to populate the gut tube?

A

Vagal- towards the proximal gut tube towards the mouth
Lumbosaccral- distal gut tube towards the anus

They then migrate along the gut tube (Vagal migrates towards the anus and Lumbosaccral migrates towards the mouth), then meet in the middle (around the distal colon), then they overlap which is necessary because then there would be a region of the gut tube that never gets innervated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Accessory Digestive Organs

A

Parotid salivary gland, teeth, tongue, sublingual salivary gland, submandibular salivary gland, liver, pancreas, gallbladder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Gastrointestinal Tract (Digestive Organs)

A

Oral cavity, pharynx, esophagus, stomach, large intestine, small intestine, anal canal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Esophagus

A

25cm long, muscular tube

SSNK epithelium

Two types of glands:
- Esophageal cardiac glands in lamina propria (LP) of the mucosa. Only in the inferior portion of esophagus where it meets the stomach
- Esophageal submucosal glands (esophageal glands proper)

Both smooth and striated muscle in muscularis externa

Mostly surrounded by adventitia. Retroperitoneal

Two sphincters:
- Upper esophageal sphincter - anatomical. This happens if the ICL is thicker. It limits food passage
- Lower esophageal sphincter - physiological. More muscle tone in the ICL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Esophagus: Muscularis Externa and Outer Lining

A

Muscularis externa
* Inner circular layer and outer longitudinal layer
* Contains both smooth (sm) and striated (st) muscle

Adventitia/Serosa
* Has an adventitia until within the peritoneal cavity, then serosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Esophagus: Mucosa

A

SSNK Epithelium
* Basophilic basal layer (mitotic zone)
* Renewal of cells 14-21 days from birth to desquamation
* Apical cells accumulate glycogen
* Nuclei become pyknotic (visible on the apical surface)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Esophagus: Submucosal Glands

A
  • Mostly mucous cells, some serous cells
  • Function similar to salivary glands (acinar)
  • Stratified cuboidal duct epithelium
  • Seromucous secretions to lubricate the lumen of the esophagus to ease passage of bolus

Very basophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Esophagus: Cardiac Glands of the Mucosa

A
  • Located in the lamina propria and resemble cardiac glands of the stomach
  • Secrete pH – neutral mucin

Less basophilic
Located more at the esophagogastric junction in the transition from SSNK to SCE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Esophagogastric Junction

A

Transition zone:
* Abrupt change in epithelium SSNK to simple columnar epithelium at the Z-line
* Smooth to plicated mucosa
- Gastric pits and cardiac glands (not the same as the cardiac glands of the stomach)
* Change from 2 to 3 layers of muscularis externa (we need another layer of smooth muscle to constrict the bag structure of the stomach as opposed to the tube structure of the esophagus, added oblique layer)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Barrett’s Esophagus

A
  • An example of metaplasia at the Z-Line (can be due to chronic GERD)
  • SSNK becomes simple columnar epithelium
  • Can lead to dysplasia and esophageal adenocarcinoma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Gross Anatomy of the Stomach

A
  1. Cardia
    - Cardiac glands- short pits and glands (doesn’t go down very far)
    - Mucous secreting cells
  2. Fundus and body (2 gross anatomical regions, 1 histological appearance bc they have the same glands)
    - Gastric (principal/fundic) glands-long
    - Stem cells at isthmus (neck) of gastric pits
    -Mucous, parietal and chief cells. Diverse cell population
  3. Pylorus
    - Pyloric glands- short, BUT the pits are long
    - Mucous and enteroendocrine cells
    -Pyloric sphincter
29
Q

Rugae

A

Folds that are so deep that they are made of mucosa & submucosa

30
Q

Stomach: Cells of the Mucosa

A

Surface mucous cell: secretes alkaline fluid containing mucin

Mucous neck cell: secretes acidic fluid containing mucin

Parietal cell: secretes intrinsic factor and HCl. More EOSINOPHILIC

Chief cell: secretes pepsinogen and gastric lipase. More BASOPHILIC

G cell: enteroendocrine cells that secrete gastrin into the blood

31
Q

Stomach: Fundus and Body

A

Gastric pits
- Lined by luminal epithelium (surface mucous cells)
- More superficial than glands

Gastric glands
- Branch from gastric pits, deep into the mucosa, all the way to the muscularis mucosae (but are still made of epithelium)
- Contain a variety of cells (mucous, digestive, endocrine, stem)

Surface Mucous Cells
- Larger
- Line gastric lumen and pits
- Neutral to basic mucous secretion
Mucous Neck Cells
- Located deeper in pit, towards gland
- Acidic mucous secretion

(Hard to distinguish/identify these two)

32
Q

Chief cell

A
  • Apical zymogen granules
  • Basal euchromatic nucleus
  • Low columnar to cuboidal in shape
  • Lots of rough ER –> BASOPHILIC
  • Basophilic
  • Most abundant deep in body of gastric gland
33
Q

Parietal cell

A
  • Large, wedge-shaped or oval to rounded
  • Centrally located nucleus
  • Most abundant in the isthmus of gastric glands
  • Microvilli = abundant surface area for ion pumps (H+ and Cl-)
  • Secrete gastric acid and intrinsic factor
  • Eosinophilic due to abundant mitochondria
34
Q

Mucosa of the Fundic Stomach

A

Enteroendocrine Cells
-within the base and body of gland

Chief Cells
-deep in gastric gland
-basophilic

Parietal Cells
-distributed throughout glands
-eosinophilic
-bulge into CT compartment

Mucous Neck Cells
-smaller cells
-superficial glands

Surface Mucous Cells
-line lumen and gastric pits

35
Q

Mucosa of Pyloric Stomach

A
  • Glands are shallow
  • Lack parietal and chief cells
  • Secrete mostly mucous
  • Also contains enteroendocrine (G) cells (not distinguishable in H&E)
36
Q

Peptic (Gastric) Ulcer

A

may occur in the pyloric stomach

  • Acid and pepsin destroy mucosa cells (ulcer) and may even penetrate the wall of the stomach to make a fissure
  • Potential causes:
    Helicobacter pylori
    NSAIDs
    Alcohol
    Gastrinoma
37
Q

Stomach: Muscularis externa

A

Muscularis externa has a third (innermost oblique) layer

38
Q

Pyloric Sphincter at the Gastroduodenal Junction

A
  • Pyloric sphincter = thickening of inner circular layer of muscularis externa
  • Gradual change from gastric mucosa with gastric pits and glands to duodenal mucosa with villi and crypts
  • Villi can be up to 6mm long!
39
Q

Small intestine Gross Anatomy

A
  • Key region for absorption of
    nutrients
  • Lipids: lacteals
  • Amino acids and sugars: capillaries then hepatic portal vein
  • Duodenum
  • Jejunum
  • Ileum
    Surface area specializations
40
Q

Lacteals

A

large central lymphatic vessels that help to absorb lipids

41
Q

surface area specializations of the small intestine

A
  • Circular folds (plicae circulares): submucosal core
  • Villi: only mucosa
  • Microvilli (with glycocalyx): apical specializations of enterocytes
42
Q

Two major cell types of the small intestine

A

enterocytes and goblet cells

Progressive increase in number of goblet cells from duodenum -> jejunum -> ileum
bc we have already done the absorption
Proximal = more absorptive cells
Distal = more goblet cells

43
Q

Villi

A

evaginations, finger-like projections into the lumen

these epithelial cells contain
- Capillaries
- lacteal

44
Q

Crypts

A

invaginations, dips into the lamina propria

these epithelial cells contain
- Stem cells: migrate up towards the tip of the villus. Oldest cells are at the tip
- Paneth cells
- Enteroendocrine cells

45
Q

Epithelial Cells of Intestinal Villi

A
  1. Enterocytes – oldest at tips of villi
  2. Goblet cells – mucin
46
Q

Epithelial Cells of Crypts of Lieberkühn

A
  1. Enteroendocrine cells: basal red granules
  2. Paneth cells (important for immunity): apical red granules
  3. Stem cells
  4. Goblet cells
47
Q

Lamina Propria

A

Lacteals
Fenestrated capillaries (lots of them!)
Muscularis mucosae:
- Mixes into lamina propria

48
Q

Lipid Absorption

A
  • Enterocytes absorb digested lipid droplets that are concentrated in the smooth ER
  • Triglycerides synthesized in the smooth ER and packaged in the Golgi for export
  • Chylomicron exocytosis and absorption into lacteals (lymphatic capiillary)
49
Q

Hepatic Portal Circulation

A

usually capillaries drain into veins which then go back to the heart, but GI capillaries drain into veins which then drain into capillaries again in the liver so that the liver can process the nutrients

  • Capillaries of GI system -> portal vein -> capillary bed in the liver = hepatic portal system
  • Liver disease can cause portal hypertension
50
Q

Celiac Disease

A
  • Loss of intestinal villi
  • Increased immune cell presence in the lamina propria
  • Increased intraepithelial lymphocytes
  • Elongated crypts with increased stem cell activity (cells are trying to repopulate)
51
Q

Duodenum

A
  • Duodenum is about 25-30cm long
  • Circular folds less pronounced than jejunum
  • Long, club-shaped villi
  • Brunner Glands of submucosa (penetrate into mucosa): this is ONLY found in the duodenum and no other part of the small intestine
    • Tall cuboidal to columnar cells with flattened basal nuclei
    • Alkaline mucous (pH 9) secretion
52
Q

Jejunum

A
  • About 2.5m long
  • Plicae circulares (Circular folds)

No submucosal glands!
No GALT!

53
Q

Ileum

A
  • Ileum is about 3.5m long
  • Has the most goblet cells
  • Fewer folds
  • Peyer’s patches (GALT)
  • Ileocecal valve
54
Q

GALT

A
  • Gut-Associated Lymphoid Tissue
  • Payer’s patches in the ileum
  • Microfold cells (M cells): house the immune cells
    • Cuboidal
    • Transcytosis of antigens
    • Intraepithelial pockets house lymphocytes and dendritic cells
    • Helper T cells present antigens and stimulate B cells
    • Plasma cells make IgA to neutralize antigens in the gut

nestled just beneath the basement membrane
Basement membrane is very porous where it overlines the GALT
NO VILLI - bald region of flat boring epithelium. This is done to get immune cells as close as possible to potential pathogens in the gut

55
Q

Large Intestine

A

Ileocecal valve (prevents backward flow from the cecum to ileum of small intestine) to pectinate line
* Cecum: first part of LI
- Appendix: offshoots from cecum
* Ascending colon
* Transverse colon
* Descending colon
* Sigmoid colon
* Rectum

Special features
- Rich in GALT (appendix)
- Taut/toned muscluaris externa which gives a “bunched” appearance (haustra)
- Teniae coli & haustra

  • Absorptive cells line lumen
  • No villi; deep intestinal crypts
  • Increasing number of goblet cells
  • Enteroendocrine and stem cells
  • Serosa or adventitia depending on location
56
Q

Teniae Coli

A

Thickened OLL of muscularis externa

57
Q

Structure of the Appendix

A
  • Simple columnar epithelium
  • Lacks villi
  • Short crypts
  • Prominent GALT in submucosa and lamina propria. It’s around the whole thing, not just in one area
  • Serosa
58
Q

The Anorectal Junction

A
  • Pectinate line – change from simple columnar (endoderm-derived) to SSNK (ectoderm-derived)
  • Hemorrhoidal venous plexuses
  • Columns of Morgagni
  • Anal glands secrete mucous, and sinuses collect it
  • Internal sphincter is ICL and external sphincter is skeletal muscle
  • Adventitia
  • Superior hemorrhoidal plexus and inferior hemorrhoidal plexus have different arterial supplies
59
Q

Esophagus

A

(From lab manual)

Epithelium - is stratified squamous non-keratinized.

Muscularis mucosae - varies in thickness. It is an incomplete, even sparse layer in the upper esophagus, and a complete layer in the lower esophagus.

Muscularis externa - very unique, in that it can contain both skeletal and smooth muscle co-localized. The skeletal muscle aids in coughing and vomiting, and in humans is more prevalent in the upper esophagus. (In many animals, such as dogs and cats, skeletal muscle is present throughout the entire length of the esophagus.)

Submucosa - contains sparse, mucus secreting esophageal submucosal glands.

Serosa-adventitia - Over most of its length, the esophagus is adventitial to other structures. However, just before the junction with the stomach, it crosses the diaphragm and enters the abdominal cavity, attaining an outer serosa layer continuous with the diaphragm’s parietal peritoneum.

60
Q

Cardiac Stomach

A

(From lab manual)

Epithelium - thrown into grossly invaginated folds called gastric pits. Numerous glands empty into the base of each pit. The superfical epithelium is covered solely with surface mucous cells, whereas the base of the pit and the gland consists primarily of mucous neck cells. Occasional parietal and chief cells are seen (see below), but these are not numerous. Glands are relatively shallow, roughly equal in depth to the pits.

Muscularis externa - three cross-oriented layers. (Since the stomach is not tube-shaped, but rather bag-shaped, the orientation of the muscle in each of the three layers is more of an anatomic concern than histologic.) You may (or may not) be able to discern the three layers - remember that if two layers are both cut obliquely in a given section, their true orientations will not be clear to you.

61
Q

Fundic Stomach

A

(From lab manual)

Epithelium - gastric pits, and long, functionally important glands. Numerous spherical, eosinophilic parietal cells are present. Basophilic chief cells are located preferentially at the base of the glands.

62
Q

Pyloric Stomach

A

(From lab manual)

Epithelium - gastric pits, and shallower glands, similar in appearance to the cardiac stomach. Only surface mucous and mucous neck cells are present.

Muscularis externa - transitions back to a 2-layered structure at the pyloric sphincter, which is an anatomical dilation of the ICL.

63
Q

Duodenum

A

(From lab manual)

Epithelium - over the entirety of the small intestine, the epithelium is thrown into villi, evaginated worm-like structures rising from the surface. It is worthwhile to view some endoscopy images - whereas villi and crypts may be difficult to distinguish in a histological section, there is a clear distinction between them when viewed in situ. Knowing what they really look like will help you to visualize their appearance in slides.

Superficially, the epithelium of the intestines consists primarily of two cell types the enterocyte which has an absorptive function, and the goblet cell which secretes mucus. (Though your textbook refers to mucous cells in the respiratory system as “goblet cells” the term “goblet cell” should properly be reserved for the intestinal mucus-secreting cells.) The small intestine is dominated by enterocytes; goblet cells increase in ratio towards the anal canal.

The intestines also contain invaginated epithelial crypts, which are topologically similar to the pits of the stomach. These crypts are often called “intestinal glands” (including by Ross), but the term “crypt” more accurately represents their morphology. The only major cell type specific to the crypts is the Paneth cell, which is readily recognizable by its large eosinophilic secretion granules. It is found at the base of crypts throughout the small intestine. In the duodenum (only) Brunner’s (submucosal) glands drain into the base of the crypts. These are true glands with specialized secretory cells, and are easily recognizable since they are not contained within the mucosal layer.

Lamina propria - contains numerous immune cells. The core of the intestinal villi is the lamina propria layer. In the center of the villi, large lymphatic channels called central lacteals can sometimes be visualized, if they are dilated with absorbed lipids.

Muscularis mucosae - a thin layer, but important for establishing the position, for example of the Brunner’s glands.

Submucosa - contains Brunner’s glands. The common bile duct also transits at one point. Over the entirety of the small intestine, thickenings known as plicae circulares cause a folded appearance. The folds are primarily in the circumferential direction, and thus are best appreciated when the organ is sectioned longitudinally.

64
Q

Jejunum

A

(From lab manual)

Submucosa - the distinguishing feature of the jejunum is, quite literally, the lack of features that characterize the duodenum and ileum. The jejunum does not contain the Brunner’s glands of the duodenum, and it does not contain the Peyer’s patches (see below) of the ileum. Plicae circulares continue.

65
Q

Ileum

A

(From lab manual)

Submucosa - always contains Peyer’s patches, structures comprised of GALT that contains distinct lymphoid follicles. The bulk of these follicles are usually contained in the submucosal layer, though they often transit the lamina propria as well. They are always localized to one surface, covering approximately 1/3 of the organ’s cross section. Plicae circulares continue.

66
Q

Colon

A

(From lab manual)

Epithelium - unlike the small intestine, villi are absent. The proportion of goblet cells is noticeably increased near the rectum.

Submucosa - numerous permanent folds continue, though here they are usually not referred to as plicae circularis. The length of the colon is subdivided into pouches called haustra, though there is scant evidence of this organization on histology. Haustra are useful to distinguish the colon from the small intestine in X-rays or other radiologic images.

Muscularis externa - the OLL, over most of the colon, separates into distinct longitudinal bands, called taeniae coli. Usually 3 such bands are found, but some portions of the colon have fewer. Because of the taenia coli, at any given point around the circumference of the colon, the OLL may appear either thickened or absent.

Serosa - as one moves towards the rectum, a greater percentage of the outer surface becomes adventitial. The peritoneum is fully crossed by the rectum.

67
Q

Appendix

A

(From lab manual)

Epithelium - As the appendix is a diverticulum of the first portion of the colon, no villi are present.

Mucosa - Reliably contains GALT and lymphoid follicles, however unlike in the ileum, these are not seen to be localized to any given part of the organ.

Serosa - Does the appendix have a mesentery? (And do you expect it to have one?)
ANSWER: yes

68
Q

Anal Canal

A

(From lab manual)

Epithelium - transitions form simple columnar to stratified squamous non-keratinized, and quickly (over several millimeters) to the stratified squamous keratinized epithelium of the skin. The transition from simple columnar to stratified squamous non-keratinized is an anatomically visible structure known as the pectinate line.

Lamina propria - an extensive vascularization is often seen.

Muscularis mucosae - disappears near the pectinate line.

Submucosa - folds that are primarily longitudinal relative to the organ are called Columns of Morgagni.

Muscularis externa - ICL thickens to form the internal anal sphincter.

The external anal sphincter is comprised of skeletal muscle encircling the anal canal.

Adventitia - the rectum transits the peritoneal cavity, so the entirety of the anal canal lies anatomically apposed to pelvic floor and musculature, and thus has an adventitia layer.

69
Q

How to differentiate between villi and pits/crypts?

A

Villi are evaginations, i.e. upward projections. Pits or crypts are invaginations, i.e. downward projections, or epithelial lined “holes” in the surface.

When distinguishing villi from pits/crypts in a 2D section, it is helpful to visualize a section tangential to the surface. If you are looking at villi, the connective tissue will be in the center of the epithelial-lined “islands” and the apical surface will be towards the space, which is the lumen of the organ. If, on the other hand, you are looking at pits or crypts, the connective tissue will dominate, and be the “ground” of the image. The apical surface of the epithelium will point inwards towards the lumenal spaces.

COT pt. 2 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions