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Flashcards in Digestive Tract Deck (35)
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1
Q

Lamina Propria

A

CT between the epithelium and the muscularis mucosa

2
Q

Muscularis Externa

A

Circular and longitudinal smooth muscle.

3
Q

Serosa or Adventitia

A

Serosa= simple squamous epithelium (the visceral peritoneum) and its underlying CT found on the abluminal surface of most of the gut. When there is no serosa, there is adventitia comprised of loose CT.

4
Q

Esophagus

A

Non-Keratinized stratified squamous. Mucous glands in the sub mucosa for lubrication. Muscalaris externa is skeletal muscle in the proximal 1/3 transitioning to smooth muscle. In the thorax there is an adventitia circumferentially and only in the abdomen is there a serosa covering the anterior and lateral surfaces.

5
Q

Gastro-Esophageal Junction

A

Abrupt transition from non-keretinized stratified squamous to simple columnar.

6
Q

Stomach

A

Storage up to 1.5 liters without a change in intraluminal pressure. Mechanical mixing. Early enzymatic digestion. Epithelium specialized to produce HCl, enzymes, hormones, protraction from acid. Surface mucous cells produce an alkaline mucous protective layer. Thickened muscalaris externa and three layers for protection. Distal end of the stomach, the circular muscle layer is thickened to produce the pylorus.

7
Q

Parietal (oxyntic) cells

A

Red due to mitochondria. Intercellular canalicular system which serves to increase the SA where HCl and intrinsic factor (a glycoprotein necessary for vitamin B12 absorption in the ileum) are produced. These cells contain the enzyme carbonic anhydrase which combines CO2 and H2O to produce H2CO3, which rapidly dissociates into H+ and HCO3-. H+ is actively pumped out of the canaliculi.

8
Q

Chief (zymogenic) Cells

A

Proenzyme pepsinogen which is converted by the acidic medium in the gastric lumen into pepsin, a proteolytic enzyme which breaks down proteins into smaller peptides. They also secrete lipase and leptin. Basal= basophilic due to RER. Vesicle containing pepsinogen is eosinophilic in apical.

9
Q

Enteroendocrine Cells

A

Secrete the hormone gastrin as well as serotonin, VIP, somatostatin, and others into the blood at the basal surface of the cell. Gastrin is produced mainly in the antral (distal) portion of the stomach and stimulates acid secretion by the parietal cells in the body of the stomach.

10
Q

Mucous Neck Cells

A

Produce a unique mucous.

11
Q

Stem Cells

A

Replenish and differentiate.

12
Q

Surface Mucous Cells

A

Sticky mucous. Bicarbonate rich in the high pH environment.

13
Q

Small Intestine

A

Longest portion of GI. Duodenum, jejunum, and ileum. Terminates at the ileocecal valve, or the entrance to the colon. Muscalaris mucosa produces movement to mucosal villi while the muscalaris externa moves the intestinal contents not only distally, but in an alternating antegrade/retrograde fashion that prolongs contact and mixes.

14
Q

Duodenum

A

Begins just distal to the pyloris and ends at the duodenojejunal junction (marked by the ligament of Treitz. Receives secretions from the liver and gallbladder through the common bile duct. Chemical and enzymatic reactions occur to prepare the contents for digestion. Pancreas secretes alkaline secretions as do the submucosal glands of Brunner (identifying feature of the duodenum). Pancreas secretes enzymes that break down proteins and carbohydrates, while the bile emulsifies fats.

15
Q

Glands of Brunner

A

Distinctive feature of the duodenum. Secretes alkaline secretions.

16
Q

Plicae Circulares

A

Throw up the intestinal mucosa into grossly visible folds.

17
Q

Intestinal SA

A

Lots of folding, like plicae circulares. Villi projections of the mucosal epithelium. Further projections of the apical cell membrane of enterocytes into microvilli. 1500 fold increase in SA.

18
Q

Jejunum

A

Largest amount of absorption occurs in the proximal region. SA is maximized by plicae and villi and longer villi. Gradual change to the ileum. Absorption takes place on the apical surface with monosaccharides and amino acids entering the capillaries and fat products (mainly chylomicrons) entering the lymphatics.

19
Q

Villous Architecture

A

The villi are mucosal finger-like projections into the intestinal lumen. Epithelium consists of enterocytes with microvilli on their apical surface forming the brush border aka striated border with mucous filled goblet cells interspersed.

20
Q

Core of the Villi

A

Lamina Propria containing capillaies, lymphatics, nerves, smooth muscle cells, and typical CT cells (leukocytes, plasma cells, macrophages, etc).

21
Q

Crypts of Lieberkuhn

A

Intestinal glands burrowing into the lamina propria of the mucosa. The mitotic activity which replenishes the enterocytes occurs only in the depths of these glands. The cells then migrate towards the lumen reaching the tips of the villi where they are sloughed off, replacing the entire epithelium every 3-6 days.

22
Q

Paneth Cells

A

Located in the crypts and have granules containing lysozyme secreted to protect against bacterial infection.

23
Q

Ileum

A

Not distinctly different from the jejunum. Less need for absorptive SA and the plicae and villi decrease in frequency and length. Increase in lymphoid tissue signaling and immunological activity. Sometimes, collection of lymphoid tissue are visible to the naked eye “Peyer’s patches.” Microscopically, there are lymphoid follicles in the lamina propria and submucosa. Epithelium contain “M” cells. The absorption of vitamin B12 and the reabsorption of bile acids occur in the distal ileum.

24
Q

Peyer’s Patches

A

Collections of lymphoid tissue visible to the naked eye.

25
Q

“M” Cells

A

Endocytose intestinal antigens, transporting them via macrophages and lymphocytes to the lymph nodes to induce an antibody response (IgA) by plasma cells.

26
Q

Colon

A

Absorb water and electrolytes from liquid intestinal content that enters through the ileocecal valve. The most water absorption occurs in the small intestine but that which occurs in the colon is responsible for the consistency of a formed stool from a semi-liquid substance. Simple columnar epithelium. Microvilli but no villi. Glands with many goblet cells for lubrication. There are lymphoid nodules in the lamina propria and submucosa and a dramatic increase in lymphoid nodules in the vermiform appendix hinting at an immunological function.

27
Q

Taeniae coli

A

Three separated, segregated bands of longitudinal smooth muscle. Distinctive. Positive ID in surgery. Converge at the blind end of the cecum at the base of the appendix.

28
Q

Haustra

A

Between the taeniae the colonic walls bulge out forming sacculations.

29
Q

Rectum

A

Distal end of the colon. Longitudinal smooth muscle are once again circumferential (ie no taeniae). the rectum ends at the level of the pelvic diaphragm where the mucosa is thrown up into longitudinal folds.

30
Q

Digestive Epithelium

A

Simple columnar.

31
Q

Rectal Columns of Morgagni

A

Mucosa is thrown up into longitudinal folds.

32
Q

Anus

A

Terminal portion about 4 cm. Epithelium changes to stratified squamous. Then keratinized stratified squamous. Thickened circular smooth muscle fibers thickened to internal anal sphincter.

33
Q

Meissner’s Plexus

A

Neural cell bodies located in the submucosa.

34
Q

Auerbach’s plexus

A

Ganglia located between two layers of the muscularis externa.

35
Q

Somatostatin

A

Inhibition of other endocrine cells. Produced in the pulorus duodenum.