UNIT 2: GI tract Flashcards

1
Q

what does the foregut contain and what is its arterial supply?

A

oesophagus to middle duodenum (includes stomach, liver and pancreas)
- supplied by coeliac trunk

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2
Q

what does the midgut contain and what is its arterial supply?

A

middle duodenum to proximal 2/3 of transverse colon (includes ascending colon/ caecum/ appendix/ jejunum/ ileum)
- supplied by superior mesentric artery

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3
Q

what does the hindgut contain and what is its arterial supply?

A

distal 1/3 of transverse colon to anal canal (includes descending colon, sigmoid colon and rectum)
- supplied by inferior mesentric artery

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4
Q

where does the coeliac trunk arise from?

A

abdominal aorta at level of T12 between crura of diaphragm

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5
Q

what are the three major branches of the coeliac trunk?

A
  • left gastric artery
  • splenic artery
  • common hepatic artery
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6
Q

what does the common hepatic artery divide into?

A
hepatic artery (proper) - branches into right and left as approaches porta hepatis of liver
gastroduodenal artery - ends as superior pancreaticoduodenal artery
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7
Q

where does the right gastric artery branch from and what does this form with the left gastric artery?

A

branches from hepatic proper artery

anastomose to form inner arcade - supplies stomach (sits on lesser curve)

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8
Q

what branches off the splenic artery?

A

posterior gastric artery - supplies the fundus and upper body of stomach
- left gastroepiploic (gastro-omental) artery

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9
Q

where does the right gastroepiploic artery branch from and what does this form with the left gastroepiploic artery?

A

branches from gastroduodenal artery

anastomose to from outer arcade supplying stomach sits on greater curve

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10
Q

what veins supply the stomach?

A

parallel to the arteries but arise from portal veins and drain into the hepatic portal venous system

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11
Q

what compose the outer/ inner layers of interior of stomach?

A

outer: smooth muscle
inner: muscosa - in fundus - smooth but in pylorus forms longitudinal folds

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12
Q

where does the esophagus pass ?

A

follows verterbral column (thoracic kyphosis) and passes through esophageal hiatus at level of T10 and terminates at esophagogastric junction at T11 (7th costal cartilage)

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13
Q

how would you describe the peritoneum on the oesophagus?

describe the external layer on superior/ middle/ inferior parts

A

retroperitoneal

  • voluntary striated muscle
  • both
  • smooth muscle
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14
Q

what innervates the oesophagus?

A

vagal trunks which form anterior/ posterior vagal nerves
thoracic sympathetic trunks via greater splanchnic nerves
periarterial plexus

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15
Q

describe the arterial supply and venous drainage of the oesophagus?

A

supplied by esophageal branches of the left gastric artery and left inferior phrenic artery
venous drainage - portal venous system through left gastric vein

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16
Q

describe the four parts of the duodenum

A

1) superior - anterolateral to L1
2) descending - sides of L2/3 around head of pancreas
3) inferior - anterior to IVC/ aorta and posterior to SMA/ SMV - level of L3
4) ascending - passes on left side of aorta from L3 to L2 -curves anteriorly to join jejunum at duodenojejunal flexure

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17
Q

what is the duodenojejunal flexure supported by?

A

suspensory muscle (ligament of Treitz) - slip of skeletal muscle from diaphragm and smooth muscle from 3rd/ 4th parts of duodenum

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18
Q

what are proportions of the jejunum to ileum?

A

jejunum -2/5 - upper left quadrant

ileum - 3/5 - lower left quadrant

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19
Q

compare jejunum to ileum

A

jejunum- thick intestinal wall/ longer vasa recta/ less arcades/ red in colour
ileum - thin intestinal wall/ shorter vasa recta/ more arcades/ pink in colour

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20
Q

what are the main branches of the superior mesentric artery?

A
inferior pancreaticoduodenal artery 
middle colic artery 
right colic artery 
ileocolic artery  
jejunal/ileal arteries
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21
Q

what arteries supply the duodenum?

A

1st/ 2nd - coeliac trunk- gastroduodenal and superior pancreaticoduodenal arteries
3rd/ 4th - superior mesentric arteries - inferior pancreaticoduodenal arteries

22
Q

what veins drain duodenum?

A

hepatic portal veins- drain directly or indirectly via splenic or superior mesentric veins

23
Q

what nerves innervate the duodenum?

A

vagus (parasympathetic)

greater/lesser splanchic nerves - coeliac/ mesentric plexuses (sympathetic)

24
Q

what structures form the large intestine?

A

cecum, appendix, colon, rectum and anal caal

25
Q

where is the cecum found? describe its features

A

blind pouch in right lower quadrant - right iliac fossa

  • inferior to ileocecal valve
  • no mesentery but entirely enveloped by peritoneum
26
Q

where is the appendix found?

A

extends from posteromedial aspect of cecum inferior to valve

  • base of appendix found at Mcburneys points- 1/3 of distance from the anterior iliac superior spine to umbilicus
  • has short mesentery = mesoappendix (posterior side of ileum)
27
Q

what arteries/veins supply the cecum and appendix?

A

cecum - ileocolic
appendix - appendicular
venous drainage for both by ilecolic vein

28
Q

give features of the colon

A

teniae coli - 3 longitudinal thickened bands of muscle fibres from base of appendix to rectosignoid junction and form continuous layer around the rectum
haustra - sacculations/ pouches - formed from teniae coli
smooth internally - no villi

29
Q

describe the attachment of the ascending and descending colon to the posterior abdominal wall

A

peritoneum covers anterior and lateral sides attaches them to wall - short mesentery

30
Q

describe the attachments of the transverse colon

A

attached to diaphragm by phrenicocolic ligament

- has transverse mesocolon lies along inferior border of pancreas

31
Q

where is the sigmoid colon located?

A

iliac fossa at level of S3 long mesentery = sigmoid mesocolon

32
Q

what are the three main branches of the inferior mesentric artery?

A

left colic artery
sigmoid arteries
superior rectal artery

33
Q

which arteries supply the parts of the colon?

A

ascending: ileocolic/ right colic artery
transverse: middle colic artery
descending: left colic
sigmoid: sigmoid arteries

34
Q

What is the function of the caecum?

A

reservoir for chyme - receives the ileum

35
Q

What is the name of the collateral supply of the colon?

A

marginal artery of Drummond - formed from anastomosis of terminal branches of SMA & IMA - vasa recta branch from this

36
Q

What is the venous drainage of the colon?

A

corresponding veins - empty into hepatic portal vein

37
Q

What is a volvulus? describe the clinical signs and treatment

A

where the intestine twists on itself
- colicky pain, abdominal distension, absolute constipation
Rx: decompression or resection if perforated

38
Q

What level does the rectum begin at?

A

level of S3

39
Q

Describe the two flexures of the rectum

A
  • sacral flexure: follows curve of the sacrum and coccyx

- anorectal flexure - formed from the tone of the puborectalis muscles - contributes to faecal continence

40
Q

Describe the ampulla of the rectum

A

last segment of the rectum - continous with the anal canal

- relaxes to accumulate & temporarily store faeces until defecation

41
Q

describe the peritoneal coverings of the rectum

A

superior 1/3 - anterior/ lateral sides
middle 1/3 - anterior only
posterior 1/3 - no peritoneum

42
Q

describe the reflections of the peritoneum in males and females

A
  • male: rectovesical pouch - reflection from rectum to posterior bladder wall
  • female: rectouterine pouch (pouch of Douglas) - reflection from rectum to posterior vagina & cervix
43
Q

describe the arterial supply of the rectum

A
  • superior rectal: IMA continuation
  • middle rectal: internal iliac branch
  • inferior rectal: internal pudendal
44
Q

describe the venous drainage of the rectum

A

corresponding veins but superior drains into the portal venous system and middle/ inferior drain into systemic venous system
- anastomosis between portal and systemic veins form site of portocaval anastomosis

45
Q

describe the innervation of the rectum

A
  • sympathetic: lumbar sphlanchnic + sup/ inf hypogastric plexus
  • parasympathetic: S2-4 (via pelvic splanchnic and inferior hypogastric plexus)
46
Q

describe the anal canal

A

it is located in the anal triangle and it is collapsed by internal and external anal sphincters to prevent passage of faecal material

47
Q

describe the two anal sphincters

A
  • internal anal sphincter: formed from thickening of involuntary circular smooth muscle in the bowel wall ( surrounds upper 2/3)
  • external anal sphincter: voluntary muscle overlaps the internal and blends with the puborectalis muscle (surrounds lower 2/3)
48
Q

where is the anorectal ring found?

A

junction of rectum & anal canal (fusion of sphincters & puborectalis)

49
Q

describe the histology of the anus

A
  • superior aspect - columnar epithelium
  • inside canal - longitudinal folds = anal columns joined at inferior ends by anal valves => form pectinate line which divides the anus into two parts
50
Q

what epithelium found below the pectinate line?

A

non-keratinised stratified smooth epithelium (anal pecta) this transitions into true skin at the level of the inter-sphincteric groove

51
Q

describe the vasculature of the rectum

A
  • above pectinate line: superior rectal artery/ vein

- below pectinate line: inferior rectal artery/ vein