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3A week 2 - lower GI tract > anatomy and physiology of small bowel > Flashcards

anatomy and physiology of small bowel Flashcards

1
Q

where is the small intestine located and what marks the beginning and end of it (anatomically)

A

located in the abdominopelvic cavity; beginning: pylorus of the stomach
ends: ileocecal junction

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2
Q

what are the 3 main parts of the small intestine

A
  1. duodenum
  2. jejenum
  3. ileum
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3
Q

what does retroperitoneal mean

A

abdominal structures that are only partially covered by peritoneum and lie posterior or behind the abdominal peritoneum e.g. distal duodenum (parts 2-4)

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4
Q

what does intraperitoneal mean

A

structures that have invaginated and are completely covered by the visceral peritoneum e.g. jejenum, proximal duodenum and ileum

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5
Q

what are the 4 parts of the duodenum

A
  1. superior part;
  2. descending part;
  3. inferior part;
  4. ascending part
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6
Q

at what vertebral level does the duodenum begin

A

L1

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7
Q

what are the attachments to the superior duodenum (2)

A
  1. hepatoduodenal ligament - part of the lesser omentum
  2. greater omentum
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8
Q

what is the ampulla/duodenal cap?

A

The proximal 2cm of the superior part - it is more dilated and freely mobile as it is intraperitoneal

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9
Q

what 2 organs lie over the top and which 3 lie posteriorly to the proximal duodenum

A

anterior: liver and gall bladder
posterior: Inferior vena cava, bile duct and gastroduodenal artery posterior

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10
Q

what vertebrae does the descending part of the duodenum run between

A

L1 - L3 -> It curves downward around the head of the pancreas which is medial, and runs inferiorly from the L1 to the L3

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11
Q

what 2 organs lie over the top and which 2 lie posteriorly to the descending duodenum

A

anterior: transverse colon and the convolutions of the small intestine;
posterior: the hilum of the right kidney and its vessels, and the ureter

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12
Q

what is the major duodenal papilla

A

a rounded projection in the duodenum into which the common bile duct and pancreatic duct drain -> forms a hepatopancreatic ampulla

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13
Q

what is the function of the major duodenal papilla

A

to carry the pancreatic juices and bile to the duodenum

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14
Q

what are 2 other names for the major duodenal papilla

A

papilla of vater and ampulla of vater

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15
Q

what is the minor duodenal papilla

A

where the accessory pancreatic duct opens - not always present

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16
Q

at what vertebral level does the inferior duodenum travel

A

L3

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17
Q

what organs lie posteriorly to the inferior duodenum (4)

A
  1. inferior vena cava
  2. the aorta
  3. the proximal parts of the inferior mesenteric vessels
  4. body of the L3 vertebra
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18
Q

what lies anteriorly to the inferior duodenum (3)

A
  1. superior mesenteric artery
  2. the superior mesenteric vein
  3. parts of the jejunum
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19
Q

what is the name for the point of connection between the duodenumand jejenum, and at what vertebral level does this occur

A

duodenojejunal flexure/junction - occurs at L2

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20
Q

from what ligament does the duodenojejunal flexure hang

A

ligament of Treitz - made out of the skeletal muscles from the diaphragm and the smooth muscles of the duodenum

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21
Q

what is the duodenal main arterial supply (2)

A
  1. celiac trunk
  2. superior mesenteric artery
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22
Q

what are the different branches of the celiac trunk and what do they supply

A
  1. the common hepatic arterywhich gives rise to the supraduodenal and gastroduodenal arteries
  2. supraduodenal artery - supplies portions of the first and second duodenal parts
  3. gastroduodenal artery - has a branch called the superior pancreaticoduodenal artery, that supplies the first two parts of the duodenum up until the major duodenal papilla
23
Q

what is the branch of the superior mesenteric artery and what part of the duodenum does it supply

A

the inferior pancreaticoduodenal artery, which supplies the other two parts of the duodenum, distal to the major duodenal papilla.

24
Q

what is the venous drainage of the duodenum

A
  1. splenic
  2. superior mesenteric vein
    both eventually drain into the hepatic portal vein
25
Q

what lymph node does the duodenal lymphatic system ultimately drain into

A

celiac node

26
Q

what is the innervation for the duodenum

A

celiac and superior mesenteric plexuses - both parasymp and symp neurons reside here -> the sympathetic fibers synapse in prevertebral ganglia such as the celiac and superior mesenteric ganglia, and send their postsynaptic sympathetic fibers through the periarterial plexuses;
The parasympathetic fibers, on the other hand just pass through the celiac and superior mesenteric plexuses as well as the periarterial plexuses and eventually synapse in the intrinsic ganglia found in the walls of the duodenum

27
Q

what abdominal quadrant is the jejenum mostly situated in

A

left upper quadrant

28
Q

what abdominal quadrant is the ileum mostly situated in

A

right lower quadrant

29
Q

what is the mesentry

A

a fold of membrane (visceral peritoneum) that attaches the intestine to the wall around the stomach area and holds it in place

30
Q

what lies within the folds of the mesentry (4)

A

1.the superior mesenteric vessels
2. lymphatic vessels
3. nerves that supply the small intestine
4. fat tissue

31
Q

what is ther srterial blood supply for the ilium and jejenum

A

superior mesenteric artery

32
Q

what are the branches off the SMA in the mesentery known as

A

arterial arcades (arterial loops) which give rise to many straight arteries known as the vasa recta

33
Q

jejenum vs ilieum arteries

A

jejenum: fewer arcades with larger loops and longer vasa recta;
ileum: more arcades with shorter loops and shorter vasa recta

34
Q

what are the lymphatic vessels of the jejenum and ilieum known as

A

lacteals (arise in the intestinal villi)

35
Q

where is the main lymph node for drainage of teh jejenum and iliuem

A

superior mesenteric lymphnode

36
Q

effect of sympathetic stimulation on the small intestine

A

reduces peristaltic and secretory activity to stop digestion

37
Q

along side what kind of nerve fibres do visceral sensory afferent travel

A

alongside parasympathetic fibres

38
Q

what sympathetic nerves innervate the small intestine

A

the greater and lesser splanchnic nerves

39
Q

what is the approximate length of the small intestine of adults

A

around 6m

40
Q

how long is the jejenum and ilieum

A

jejenum - 2.5m
ilium - 3.5m

41
Q

what are the 4 main layers of the small intestine wall

A
  1. mucosa
  2. submucosa
  3. muscularis propria
  4. serosa
42
Q

what are the differences in villi between the different parts of the small intestine

A

duodenum and jejunum: very tall and slender villi;
ileum: significantly shorter, broader, and their tips are flat

43
Q

what are the villi of the entire small intestine lined with

A

enterocytes (simple columnar cells with microvilli)

44
Q

what are the components of the villi in the duodenum and jejenum (5)

A
  1. enterocytes
  2. lamina propria - loose connective tissue that supports the enterocytes and forms the middle or core of each villus
  3. The crypts of Lieberkühn - glands that contain stemcells
  4. goblet cells - secrete mucous for lubrication and protection
  5. muscularis mucosa - a thin supporting layer of smooth muscle
45
Q

how do new cells reach the tops of the villi

A

arising from stem cells located within the crypt, differentiated cells move up the villi as new cells are continually formed underneath them, and within a week, the cells will reach the tip of the villi where they’re shed into the lumen

46
Q

what are paneth cells

A

small, eosinophilic cells that help provide an innate immune defense against intestinal pathogens

47
Q

what are peyer’s patches

A

masses of lymphoid tissue within the lamina propria that are only seen in the ileum

48
Q

what unique components does the mucosa of the ileum contain (3)

A
  1. shorter, borader villi
  2. Peyer’s patches
  3. lacteals (white spaces of lymphatic capilaries seen in the villi that absorbe dietary fats)
49
Q

how can the duodenal submucoa be distinguished from the others

A

the presence of brunner’s glands - thick layer of coiled, tubular glands lying just beneath the muscularis mucosa

50
Q

where are bunners glands found

A

oesophagus and duodenum

51
Q

function of brunner’s glands

A

they secrete alkaline mucus into the lumen of the small intestine in order to reduce the acidity of the gastric juices and partially digested food coming from the stomach -> occasionally pass through the muscularis mucosa so that secretions can be released into crypts

52
Q

how are the muscles in the muscularis externa (propria) arranged

A

two main layers of smooth muscle arranged in different directions:
1. The inner layer has a circular or circumferential arrangement around the wall of the small intestine
2. The muscle cells of the outer layershave a longitudinal arrangement that runs parallel to the length of the small intestine - they have a rounder appearance compared to the inner layer on cross section

53
Q

what is between the two layers of the muscularis propria

A

a network of nerves - called the myenteric plexus or Auerbach’s Plexus

54
Q

function of the serosa

A

a thin layer of loose connective tissue that allows the small intestine to move more freely within the abdomen and contains blood vessels,nerves, and lymphatic vessels as well

3A week 2 - lower GI tract (8 decks)

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