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Anatomy 2LL3 > 15 - GI: Intestines > Flashcards

15 - GI: Intestines Flashcards

1
Q

Divisions of the intestines

A

small intestine:
- duodenum
- jejunum
- ileum

large intestine:
- caecum
- colon (4 subsections)
- rectum
- anal canal

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2
Q

Colon subsections

A
  • ascending (R)
  • transverse (horizontal)
  • descending (L)
  • sigmoid (L)
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3
Q

Blood supply to intestines

quiz with GN

A

compare to GN
- celiac:
- duodenum
- superior mesenteric:
- most of small intestine
- proximal 1/3 of large intestine
- inferior mesenteric:
- distal 2/3 of large intestine

opposite drainage proportions from veins

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4
Q

Venous drainage of intestines

quiz with GN diagram (in L14 notes)

A

compare to diagram
- superior mesenteric:
- small intestine
- proximal 2/3 of large intestine
- inferior mesenteric:
- distal 1/3 of large intestine

opposite drainage proportions from arteries

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5
Q

Layers of small intestine

how it differs from the general layers of the GI tract (GN)

A

Mucosa: increase surface area
- plicae circularis
- villi
- microvilli
- simple columnar epithelium

no other changes

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6
Q

Villus histology

key differentiating features

A
  • many capillaries
  • lacteals (special lymphatic vessels)
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7
Q

what is absorbed in lacteals?

A

chylomicrons
(breakdown products of fats combined with proteins)

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8
Q

Features of the duodenum

comparisons GN

A

name: duode- 12”
nutrient absorption: major site of Ca2+ and Fe absorption
plicae circularis: most dense
lumen: largest of the small intestines

  • submucosal/brunner’s glands in first 10cm
  • hepatopancreatic ampulla connects at 10cm
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9
Q

Brunner’s Glands role

A

secretes bicarb-rich mucus in the first 10cm of the duodenum
(stops at hepatopancreatic duct because pancreas will provide bicarb-rich mucus from there)

submucosal glands

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10
Q

Features of the jejunum

comparisons GN

A

name: means ‘empty’
nutrient absorption: glucose, amino acids, water
plicae circularis: prominent (less than duodenum)
lumen: smaller than duodenum

  • 40% of small intestine
  • long vasa recta
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11
Q

Features of the ileum

comparisons GN

A

name: means ‘twisted’
nutrient absorption: Vitamin B12 and fats
plicae circularis: fewest, less pronounced
lumen: smallest of small intestine

  • Payer’s patches (lymphoid nodules)
    • protect against bacteria that leaks in from large I.
  • most prominent lacteals
  • ends at ileocaecal valve
  • short vasa recta
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12
Q

Gastroileal reflex

A

stomach signals ileum to increase peristalsis and push food through the ileocaecal valve to the large intestine

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13
Q

Regulation of digestion in intestines

neural & hormonal GN

A
  1. cephalic & gastric
    • vagus n.: release pancreatic juice
  2. chyme in duodenum
    • enteroendocrine cells: release secretin & CCK
  3. hormones reach pancreas
    • CCK: enzyme rich secretions
    • secretin: bicarbonate rich secretions
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14
Q

Intestinal contraction patterns

GN

A

Fed pattern (segmentation):
- mass of food enters intestine
- irregular, random contractions mix food with juices

Fasting pattern (!MMC):
- peristalsis begins at duodenum
- propels residual material into colon
- helps prevent bacterial growth

!migrating motor complex

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15
Q

Carbohydrate Digestion

GN

enzyme source locations are most important

A

Enzymes from:
- salivary glands (parotid & submandibular)
- pancreas
- intenstinal absorbative cells

breaks into:
- starch & disaccharides
- disaccharides & oligosaccharides
- lactose, maltose, sucrose
- galactose, glucose, fructose

end products in italic

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16
Q

Fat Digestion

GN

A
17
Q

Protein Digestion

GN

A

Enzymes from:
- stomach
- pancreas
- intenstinal absorbative cells

breaks into:
- large polypeptides
- small polypeptides & peptides
- amino acids

18
Q

Nucleic acids: digestive enzymes

GN

A

Enzymes from:
- pancreas
- intenstinal absorbative cells

breaks into:
- pentose sugars, N-containing bases, phosphate ions

19
Q

Pancreatic proteases

names, facts

A

releases inactive enzymes that digest proteins (so it doesn’t digest itself)
activated by trypsin

  • trypsinogen
  • membrane bound enteropeptidase reacts to produce
  • trypsin
  • chymotrypsinogen, precarboxypeptidase… activated by trypsin
20
Q

Fat digestion

steps, mechanisms GN

A

Primarily in small intestines (mostly absorbed in ileum)
- fat globule
- duodenum: emulsified (physically broken down) by bile salts (from liver)
- digestion by lipase (from pancreas) to produce fatty acids and monoglycerides
- micelles formed from FA and MG and bile salts
- transported to intestinal mucosa
- FA and MG leave micelles, difuse into epithelial cells
- repackaged with proteins to form chylomicrons
- extruded by exocytosis and enter the lacteals (carried by lymph)
- …left thoracic duct to liver

21
Q

Absorption in the small intestine

name of types

A

active transport: use ATP
secondary active transport: use ATP and another ion to facilitate
facilitated diffusion: through protein channel
diffusion: lipid soluble- through bilayer

all through absorptive intestinal epithelial cells

22
Q

Absorption in small intestine

glucose, amino acids, fats

A

glucose: secondary active transport, facilitated diffusion, blood
- uses Na+ gradient, 2Na and glucose enter epithelial cell

amino acids: secondary (or not) active transport, diffusion, blood
- uses Na+ gradient, Na and AA enter epithelial cell
- will use active transport if necessary

short chain fatty acid: diffusion, diffusion, blood

long chain FA or monoglyceride: pathway on another card

23
Q

Absorption in small intestine

A
24
Q

vitamin absorption

A

fat soluble (vit A, D, E, K): absorbed via micelles

water soluble: diffusion, diffusion, blood

25
Q

Water balance in intestines

average amounts produced and recycled

A

9.3L in and 0.1L out (meaning 9.2 recycled)
Secreted/produced (L):
- 1: saliva
- 2.3: ingestion
- 2: gastric juice
- 1: bile
- 2: pancreatic juice
- 1: intestinal juice

Absorbed (L):
- 8.3: small intestine
- 0.9: large intestine

26
Q

electrolyte balance in intestines

A

electrolytes help absorb water (they want to be absorbed surrounded by water)

27
Q

Stool classification

types

A

1: pellets - very constipated
2: lumpy sausage - slightly constipated
3: sausage with cracks - normal
4: smooth sausage - normal
5: blobs with clear edges - lacking fibre
6: mushy with ragged edges - inflammation
7: liquid, no solids - inflammation

28
Q

Layers of the large intestine

how it differs from the general layers of the GI tract (GN)

A

Mucosa: smooth

Muscularis: thinner
- teniae coli thicker rings of the longitudinal layer
- haustra pouches formed by TC

29
Q

Anatomy of the large intestine

GN

A
  • cecum
  • colon
    • ascending
    • transverse
    • descending
    • sigmoid
  • rectum
  • anal canal
30
Q

Histology of the large intestine

A

glands secreting mucous

31
Q

Colonic movements

facts, average values

A

motility is slow: haustral contractions every 30 mins
peristalsis: begins when food enters stomach 3-12 contractions/min) Gastrocolic reflex

32
Q

Anal canal features

A

anal columns: longitudinal folds
internal anal sphincter: involuntary control
external anal sphincter: voluntary control

33
Q

hemorrhoids

A

dilation of vascular sinoids: vessels dilate and protrude from the anus

34
Q

Defecation reflex

innervation + steps

A
  • gastrocolic reflex stretches rectal wall (sensory fibers detect)
  • contract rectal wall and relax internal sphincter (parasympathetic reflex)
  • voluntary motor control to external sphincter (motor neurons)
35
Q

hemorrhoids

A

dilation of vascular sinoids: vessels dilate and protrude from the anus

36
Q

role of bacteria in digestion

A
  • help with digestion of complex starches and sugars in dietary fiber
  • synthesis of vitamin K
  • synthesis of some B vitamins

Anatomy 2LL3 (25 decks)

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