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Digestive MBChB 2 > Lecture 11: Intestine microanatomy > Flashcards

Lecture 11: Intestine microanatomy Flashcards

1
Q

What is the name of the folds in the digestive tract?

A

Plicae circularis

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2
Q

What increases the SA of the digestive tract?

A

Plicae circularis, Villi and microvilli

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3
Q

Describe an isolated villus

A

Can be divided into villus and intestinal glands/crypts of leiberkhan

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4
Q

Whats the function of smooth muscle found in the villus?

A
  • Increased squeeze of lacteal - Increased localised movement
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5
Q

What are some conditions that impacts the villus?

A

1) Decreased blood flow in elderly can lead to malabsorption 2) Celiacs disease = villous atrophy and malabsorption IBS, Crohns etc too

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6
Q

What is the epithelium of the villus like?

A

Columnar epithelium with brush border

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7
Q

How are fats transported in the lacteals?

A

No smooth muscle, therefore rely on contractions of the muscularis mucosae. Eventually drain into venous system.

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8
Q

Whats transported in the submucosae venules of the digestive tract?

A

CHO, Proteins, Water and electrolytes. Venules in the submucosa are tributaries of the hepatic portal vein

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9
Q

What cells are found in the mucosa of the SI?

A

Columnar absorptive cells (Enterocytes) Goblet cells Enteroendocrine cells Undifferentiated cells (Stem cells for epithelium, up/down movement) Paneth cells EGEUP (Every Gut Enjoys Unique Poops)

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10
Q

What is the function of enterocytes?

A
  • Absorbs small molecules from digestion (membrane studded with enzymes i.e Enterokinase (actives gut enzymes) and Glycosidases (breakdown CHO)
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11
Q

What is found on enterocytes?

A

Brush border, microvilli that increase SA and are connected to an actin cytoskeleton for localised movement (stirring of luminal contents) Also, a glycocalyx biofilm is found on top of the brush border. Attracts/protects desired/unwanted molecules.

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12
Q

What is the function of goblet cells?

A

Found in the squamous epithelium No brush border Contains mucinogen granules Secretes mucus

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13
Q

What is the function of enteroendocrine cells?

A

Secretes hormones through basal lamina into capillaries of lamina propria.

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14
Q

Give some examples of enteroendocrine cells and their hormones

A

Specific entero-endocrine cells;

  • I cells; Detect FA/AA release CCK
  • S cells; Detect pH release Secretin
  • Enterochromaffin cells; Senses food/irritation Release serotinin (Gut motility or vomiting)

Consult lecture 19 for more specificity

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15
Q

Describe CCK function;

A

CCK stimulates pancreatic enzyme release

CCK stimulates bile release

CCK inhibits gastric emptying

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16
Q

Describe secretin function;

A

Increase pH-Enteroentocytes = Secretin,

Increase HCO3 release from pancreas.

Increase HCO3 release from brunners glands

Inhibits gastric acid release. (Somatosatin, Inhibts gastrin)

17
Q

Describe the function of serotonin;

A

Increased smooth muscle contraction and peristalsis

18
Q

Describe somatostatin function;

A

-ive feedback, inhibits gastrin release

19
Q

What is the function of the paneth cells?

A

TNF-alpha (inflam response to bacteria and parasites) Lysozyme (Bacteriacidal, destroys bac. mem.) Defensins (Increases ion channels in cell membranes of invading microbes, thus, increased permiability)

20
Q

Describe the regional specialisation of the duodenum;

A

Contains brunners glands (unique to first part of duodenum) HCO3 rich mucous to neutralise the acid in the chyme coming from the stomach

21
Q

What else is present in the duodenum to aid acidity neutralisation?

A

Enterocytes- stimulate Bile enzymes and HCO3 production

22
Q

What are unique about the jejenum villi?

A

No specialisations

23
Q

Whats unique about the ilium?

A

Contains peyers patches, Lymphatic patches, macroscopically visible.

24
Q

Difference between cilia and microvilli?

A

Cilia = Motile Microvilli = Not motile

25
Q

Give a brief overview of the large intestine;

A

Soft muscular tube, ~1.5m long, minor digestive, major absorptive role

26
Q

Describe the ceacum;

A

Expanded pouch, beginning of compaction process. Ilioceacal valve. Appendix off end. Lymphoid nodules.

27
Q

What unique features are found on the large intestine?

A

Haustra Tenae coli

28
Q

Describe the gross features of the large intestine?

A

Ceacum Ascending colon Right clonic (heaptic) flecture Transverese colon Left clonic (splenic) flecture Descending colon Sigmoid colon

29
Q

Describe the mucosa of the large intestine;

A

Smooth; No plicae or villi Mucosal glands (crypts of leiberkhan) are numerous.

30
Q

What are the cells in the mucosa of the large intestine?

A

Two cell types predominate; Columnar absorptive cells (like enterocytes in SI) - Absorb water and electrolytes - Absorbs vitamins produced by bacteria (B and K) Goblet cells; - Secretes mucous for lubrication (Increases towards end) Enteroendocrine cells; not visible on routine sections Undifferentiated cells; Base of glands.

31
Q

What are the specialisations of the lamina propria in the large intestine?

A
  • Dense collagen immediately beneath epithelium, numerous lymphatic nodules extending down to sub-mucosa. No lymphatic vessels till muscularis mucosae (thus some large intestine metastasis take ages to spread)
32
Q

What are the specialisations of the muscularis externa in the large intestine?

A

Circular and longitudinal muscle layers. Outer longitudinal forms three distinct strips/bands running along the colon (teniae coli) = Allows independent segment contraction. These contractions form little pouches (haustra coli).

33
Q

What is the large intestine covered by externally?

A

Adventitia occurs on the post./ surface of the large intestine. Elsewhere is serosa (refer to peritoneum for guidance)

34
Q

Describe the structure of the anus;

A

Final portion; Anal canal (mucosa contains long. folds called anal columns) Distal margins; Transverse folds (Marks boundary between columnar epithelium -> stratified squamous. Anal spincters; Internal = (smooth muscle) and external (skeletal muscle) End = ANUS

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Digestive MBChB 2 (31 decks)

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