Small Intestine Flashcards

1
Q

What are the general functions of the small intestine?

A

digestion
absorb nutrients
produce intestinal hormones using DNES cells

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2
Q

What are the three surface adaptations of the small intestine that increase the surface area?

A

plicae circulares
villi
microvilli

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3
Q

What is plicae circulares?

A

permanent folds affecting the mucosa and submucosa

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4
Q

Where are the plicae circulares found?

A

duodenum, jejunum and proximal ileum

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5
Q

Where are microvilli found?

A

on the luminal cell surface

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6
Q

What is the surface epithelium of the mucosa of the small intestine?

A

simple columnar

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7
Q

What other types of cells are found in the mucosa of the intestine?

A

surface absorptive cells, goblet cells, DNES cells, regenerative cells, paneth cells, M cells

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8
Q

What is the function of surface absorptive cells of the mucosa of the small intestine? what do they contain?

A

absorb water and nutrients, terminal digestion in glycocalyx

contain microvilli

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9
Q

What is glycocalyx?

A

cell produce the enzymes and absorb the monosaccharides and peptides created

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10
Q

Where are goblet cells located?

A

most in ileum, least in duodenum

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11
Q

What types of DNES cells are found in the small intestine?

A

Type I, Type K and Type S

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12
Q

What do Type I DNES cells do?

A

produce CCK

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13
Q

What does CCK do?

A

stimulates gallbladder contraction and pancreatic secretion of enzymes from serous acini

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14
Q

What do type K DNES cells do?

A

produce Gastric Inhibitory peptide (GIP)

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15
Q

What does GIP do?

A

inhibits HCl release

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16
Q

What do type S DNES cells do?

A

produce secretin

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17
Q

What does secretin do?

A

stimulates pancreas secretion of bicarbonate from pancreatic ducts
also inhibit HCl release and movement of chyme into small intestines

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18
Q

What does bicarbonate do?

A

buffer’s chyme

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19
Q

Where are regenerative cells found?

A

crypts (intestinal glands)

20
Q

Where are paneth cells found?

A

base of crypts (intestinal glands)

21
Q

What is the function of paneth cells?

A

to produce lysozymes

22
Q

Where are M cells located?

A

ileum epithelium over Peyer’s patches

23
Q

What is the cellular structure of M cells?

A

they contain large intracellular pockets that are fairly open to LP
sample foreign antigens in gut lumen and transfer antigens to lymphocytes and dendritic cells that have entered the M cell pockets

24
Q

What do M cells do?

A

promote humoral immunity

maintain appropriate gut flora

25
Q

What is a result of humoral immunity from M cells?

A

causes plasma cells to produce IgA which is transferred to epithelial cells (enterocytes) and released into the gut lumen

26
Q

What makes up the lamina propria of the mucosa of the small intestine?

A

loose areolar CT

27
Q

Where is the LP found?

A

villus core and bordering the intestinal glands

28
Q

What is contained within the villus core?

A

lacteals, vascular components and some longitudinal smooth muscle

29
Q

What are lacteals? What do they do?

A

lymphatic capillaries

absorp most lipids

30
Q

Why is smooth muscle important in the lamina propria of the gut?

A

if it is irritated then the muscle contracts and the villi shorten, which can lead to nutrient deficiencies if this is prolonged

31
Q

Describe the muscularis mucosae of the mucosa of the small intestine.

A

thin but present; connects to the smooth muscle in the villi

32
Q

What makes up the submucosa of the small intestine?

A

dense fibroelastic CT and large blood vessels (very vascular)

33
Q

What is the significant structure found in the submucosa of the duodenum?

A

duodenal (brunner) glands

34
Q

What are Brunner glands?

A

seromucous glands that primarily produce alkaline mucus, but also produce urogastrone

35
Q

Why do Brunner glands produce alkaline mucus?

A

to neutralize chyme

36
Q

Why do Brunner glands produce some urogastrone?

A

to inhibit HCl secretion and increase mitosis of epithelial cells

37
Q

What are the significant structures of the jejunum?

A

there are none

38
Q

What are the significant structures of the ileum?

A

Peyer’s patches and submucosal (Meissner’s) plexus

39
Q

What are Peyer’s patches in the ileum?

A

groups of regularly occuring large lymph nodules

40
Q

What is the submucosal plexus there for? Where is it?

A

parasympathetic innervation to influence mucosa

located close to circular muscle in muscularis externa

41
Q

What is the pattern for the muscularis externa?

A

normal pattern (inner circular, outer longitudinal)

42
Q

Where is the Myenteric (Auerbach) plexus found?

A

in the muscularis externa between the circular and longitudinal muscle layers

43
Q

What is the function of the myenteric (Auerbach) plexus in the muscularis externa of the small intestine?

A

stimulate muscularis externa for peristalsis

44
Q

Where is serosa found?

A

all of jejunum and ileum as well as the first and last cm of the duodenum

45
Q

Where is adventita found?

A

vertical (descending) portion of the duodenum

46
Q

Where is the ileocecal valve found?

A

between ileum and cecum of colon

47
Q

Is the ileocecal valve an anatomical or physiological sphincter?

A

both