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GI > Anatomy Of The Intestines > Flashcards

Anatomy Of The Intestines Flashcards

0
Q

What happens when the cells of the small intestine epithelium reproduce and where do they do it?

A

Reproduce in the villi
Migrate towards the tips, maturing as they go
-acquire capacity to absorb

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1
Q

Microscopic structure of the small intestine?

A

Mucosa folded into villi

Villi separated by crypts

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2
Q

What do the microvilli do?

A

Massively increase the surface area to form a brush border

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3
Q

What does the brush border form?

A

An unstirred layer where nutrients meet and react with enzymes secreted by enterocytes (epithelial cells), completing digestion prior to absorption.

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4
Q

What are the main layers of the small intestine?

A

Mucosa

  • epithelium
  • lamina propria
  • muscularis mucosae

Submucosa

  • connective tissue
  • with blood vessels, lymphatics and submucosal plexus

Muscularis externae

  • 2 smooth muscle layers, longitudinal and circular.
  • Myenteric plexus lies between them

Adventitia

  • loosely arranged fibroblasts
  • collagen
  • vessels and nerves pass through it

Covered by mesothelium, commonly called serosa

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5
Q

What are enterocytes?

A

Columnar cells which contain brush border enzymes for digestion

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6
Q

What are goblet cells?

A

Exocrine glands which secrete mucin

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7
Q

What cells do the crypts of Lieberkuhn contain?

A

Stem cells - produce new cells
Enteroendocrine cells - synthesise and secrete hormones
Paneth cells - secrete protective agents
Peyer’s patches (only in ileum)
Brunner’s glands - secrete alkaline fluid to neutralise chyme

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8
Q

What protective agents do Paneth cells secrete?

A

Defensins and lysosyme

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9
Q

What do Peyer’s patches do?

A

Contain MALT which house white blood cells and lymphocytes

Produce antibodies to protect from infection

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10
Q

Over all function of the large intestine?

A

Receives digested food from small intestine, from which it absorbs water and sodium to form faeces

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11
Q

Tell me about the cecum

A

First part of the colon
Blind ended sac
Slightly inferior to ileocecal junction
Can be palpated in right iliac fossa if enlarged due to poo/gas

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12
Q

Where is the appendix?

A

Attached to the posteriomedial end of caecum

Contains lymphoid tissue

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13
Q

What is the blood supply to the cecum?

A

Arterial: SMA -> ileocolic artery
Venous: ileocolic vein -> IMA

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14
Q

Where does the ascending colon extend from and to?

A

Cecum to right lobe of liver

Right colic flexure/hepatic flexure

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15
Q

Where does the transverse colon extend from and to?

A

Right colic flexure -> left colic flexure/splenic flexure

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16
Q

Where does the descending colon extend from and to?

A

Left colic flexure to the sigmoid colon

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17
Q

Where in relation to the left kidney is the descending colon?

A

Passes anteriorly to it over its lateral border

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18
Q

What marks the beginning of the sigmoid colon?

A

Where the descending colon turns medially

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19
Q

What structures are just posterior to the sigmoid colon?

A

Left ureter

Left common iliac artery

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20
Q

What is lateral to the ascending and descending colon? Function?

A

Left and right paracolic gutters

Drain any fluid that leaks from the colon

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21
Q

Clinical relevance of the paracolic gutters?

A

Allow any potentially infectious material to circulate around the peritoneal cavity which can cause further infection
This is how a ruptured appendix can cause peritonitis

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22
Q

Arterial and venous supplies to the ascending colon?

A

Arterial - ileocolic and right colic branches of SMA

Venous - ileocolic and right colic tributaries of SMV

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23
Q

Blood supply of the transverse colon?

A

Arterial - middle colic of SMA

Venous - SMV

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24
Q

Blood supply of descending colon?

A

Arterial: Left colic and superior sigmoid - branches of IMA

Venous - IMV

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25
Q

Blood supply of sigmoidal colon?

A

Arterial: sigmoid arteries - branches of IMA
Venous: IMV

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26
Q

Which artery forms an anastamosis between the superior and inferior mesenteric arteries?

A

Marginal artery

27
Q

Clinical relevance of the colonic blood supply?

A

It is collateral, so maintains blood supply in case of occlusion/stenosis of one of the major arteries.

28
Q

Where is the rectus located?

A

Begins at S3
Retroperitoneal
Immediately anterior to sacrum

29
Q

How does the extension of the peritoneal cavity in the pelvis differ between men and women?

A

Women: formed between posterior wall of uterus and colon - recto-uterine pouch / pouch of Douglas

Men: between posterior wall of bladder and the colon - retro-vesicle pouch

30
Q

What can an ulcer in the duodenal cap/ampulla erode into?

A

Gastroduodenal artery, causing massive blood loss

31
Q

What sections is the duodenum divided into? At which vertebral level is each?

A

Superior - L1
Descending - L1-L3
Inferior - L3
Ascending - L3-2

32
Q

Which part of the duodenum is connected to the liver and by what?

A

Superior

Hepatoduodenal ligament

33
Q

What are the first 2cm of the duodenum called?

A

The duodenal cap or ampulla

34
Q

Which part of the duodenum curves around the head of the pancreas?

A

Descending

35
Q

What structures does the inferior portion of the duodenum cross over?

A

Aorta and IVC

Posterior to SMA and SMV

36
Q

Which part of the duodenum is most susceptible to duodenal ulcers?

A

Superior part

37
Q

Where does the duodenum join the jejunum and what happens here?

A

Duodenojunal flexure

Suspensory muscle of the duodenum contracts which can widen the flexure

38
Q

What does the ileocecal valve do?

A

Prevents reflux of contents back into the ileum

39
Q

Features of the jejunum?

A 
Mainly in upper left quadrant
Thick intestinal wall
Longer vasa recta than ileum
Fewer arcades
Red in colour
40
Q

What are arcades?

A

Arterial loops

41
Q

What is between the layers of the mesentery of the small intestine?

A

Superior mesenteric vessels
Lymph nodes
Fat
Autonomic nerves

42
Q

Features of the ileum?

A 
Mainly in lower right quadrant
Thin intestinal wall
Shorter vasa recta
More arcades
Pink in colour
43
Q

Arterial blood supply to the small intestine?

A

Before the duodenal papilla
-gastroduodenal artery - branch of the celiac trunk

Distal to duodenal papilla
-inferior pancreaticoduodenal artery, branch of SMA

44
Q

What do the veins of the small intestine drain into?

A

Hepatic portal vein

they follow the major arteries

45
Q

At what level does the SMA arise from the abdominal aorta?

A

L1

46
Q

Blood supply of the jejunum and the ileum?

A

Jejunal and ileal arteries which are branches of the SMA

Split into many branches and form arcades, vasa recta arise from them

47
Q

Venous drainage of the jejunum and ileum?

A

Superior mesenteric vein

48
Q

Which two veins anastamose and where to form the hepatic portal vein?

A

Superior mesenteric vein and splenic vein

At the neck of the pancreas

49
Q

Which parts of the duodenum are retroperitoneal and intraperitoneal?

A

First segment is intra-peritoneal

Rest is secondarily peritoneal so jejunum and ileum are mobile

50
Q

Which has lumen is larger in diameter, small or large intestine?

A

Large has a larger diameter

51
Q

What lymphoid tissue the small and large intestines have?

A

Small - Peyer’s patches

Large - none

52
Q

What is the appendix? How long is it?

A

A blind intestinal diverticulum

6-10cm long

53
Q

Blood supply to the appendix?

A

Arterial:
Abdominal aorta -> ileocolic -> appendicular

Venous
Ileocolic -> SMV

54
Q

Arterial supply of the rectum?

A

Proximal rectum
IMA -> superior rectal -> right and left branches

Distal
Common iliac -> R and L internal iliac
-right and left middle rectal
-inferior pudendal -> right and left inferior rectal

55
Q

Venous drainage of the rectum?

A

Superior rectal vein -> IMV -> splenic -> portal

Middle and inferior rectal veins -> systemic system

56
Q

How do you know where the anal canal begins?

A

Where the rental ampulla narrows at the level of U-shaped sling formed by the puborectalis muscle

57
Q

How does the anal canal descend?

A

Posterioinferiorly

Between anococcygeal ligament and perineal body

58
Q

What is the superior half of the mucous membrane of the anus characterised by?

A

Mucous membranes

59
Q

Describe the anal columns

A

In the superior half of mucous membranes
Contain terminal branches of superior rectal artery and vein
Inferior ends are joined by anal valves
Superior to valves are anal sinuses

60
Q

What does passing faeces compressed when passing through the anal canal and what is the point?

A

Anal sinuses
Exude mucus
Aids in evacuation of faeces

61
Q

What forms the pectinate line?

A

Inferior comb-like shape of anal valves

62
Q

Vasculature of the anal canal above the pectinate line?

A

IMA -> superior rectal

63
Q

Arterial supply of the anal canal below the pectinate line?

A

Inferior rectal arteries and middle rectal arteries

Middle anastomose with superior and inferior arteries

64
Q

What is the inferior part of the anal canal derived from?

A

Endoderm

65
Q

Innervation of the anal canal?

A

Above pectinate line

  • visceral
  • visceral afferents travel with the parasympathetic nervous system to spinal sensory ganglia S2-S4 (referred pain)

Below pectinate line

  • somatic
  • inferior anal nerves
  • branches of pudendal nerve
66
Q

What sensation is the anus sensitive to?

A

Above p line
-stretching

Below p line
-pain
-touch
-temperature 
Well localised

GI (21 decks)

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