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GI anatomy II Flashcards

1
Q

The duodenum

A

• Longest part of the GI tract
•Narrow diameter
• Retroperitoreal - plastered to the posterior abdominal wall thus immobile
1st Part - duodenal cap
2nd Part- Opening of bile and pancreatic duct
• proximal to the opening of the bile duct is the foregut
• Distal to opening is midgut
3rd part - SMA and SMV pass anterior

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2
Q

The jejunum

A
  • Last two sections of small intestine
  • Mostly in upper left quadrant
  • Larger diameter and thicker wall
  • Prominent plicae circulares
  • short arterial arcades and longer vasa recta
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3
Q

The ileum

A
  • distal 3/5
  • lower right quadrant
  • Thinner walls
  • Longer arterial arcades and shorter vasa recta
  • Fewer and less plicae circulares
  • More mesenteric fat between
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4
Q

Barium swallow of jejunum and ileum

A

• The baruium swallow shows that the plicae circularis are more ovbious in jejunum than ileum

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5
Q

rotation of midgut

A

• Around 5th week
• midgut is suspended from dorsal abdominal wall by dorsal mesentery
• communicates with the yolk sac through vitelline duct
1. rapid growth and elongation of the mid gut and forms a loop
2. thus not enough space in the abdominal cavity
3. midgut herniates out in the extraembyonic cavity
4. During thr 10th week, the abdominal cavity increases in size and the intentise returns. When this occurs the mid gut loop rotates so that different parts acquire definitive position in cavity

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6
Q

Mid gut deriviatives

A
  1. Cranial limb ( first half) elongates to form the junum and 2/3 of ileum
  2. Caudal limb ( last half) - distal end of ileum, cecum , appendix, ascending colon, proximal 2/3 of
    Transverse colon
  3. Proximal part of the vitelline duct persists in 2% of indivisuals as Mecklel’s diverticulum
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7
Q

Malrotation

A
  • Congential anomaly of rotation of the midgut as it returns to the abdominal cavity
  • any rotation other than 270 anticlockwise
  • usually duodenum lies anterior to SMA and colon
  • compression and ischaemia of small intestine
  • persistent vomitting due to obstruction
  1. may cause occlusion of blood vessels if over rotated
  2. Pre disposed to volvulas and hernias
  • Complete absence of rotation
  • Incomplete rotation - jejunum, duodenum and ileum remian on right whees cecum etc remain on left
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8
Q

Meckel’s diverticulum

A

• Congential abnomality representing persistant vitellointentinal duct which connects the yolk sac to the midgut lumen

  • 2% of pop
  • present in first 2 years
  • 2ft from illeocecal
  • 2 inches in length
  • may posses gastric mucosa causing bleeding from gastric ulceration in its mucous membrane as its secreting acid
  • a fistula can form
  • small intenstine may wrap around it and cause obstruction

pain in umbilical region to right iliac fossa

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9
Q

Intestinal atresia

A

• most common site is the small intestine
• obstruction may occur at multiple sites
• failure of lumen to become recanalination / a culdesac rather than lumen at points
- may be caused by vascular damage associated with volvulus
- bile stained vomitting

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10
Q

Abdominal wall defects

OMPHALOCOELE

A

• Omphalocoele - defect in the development of musculature of the anterior abdominal wall, small bowel is herniated out

  • herniation is at the base of the umbilicus
  • large may be liver aswell
  • covered in peritoneal membrane and amnion
  • incidence of many other associated anomalies
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11
Q

Gastroschisis

A
  • herniation of bowel loops parallel to the abdominal wall defect
  • no surrounding membrane
  • compromise in vasculation to bowel or abdominal wall
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12
Q

Antenatal ultrasound

A
  • Omphaocoele - show herniated loops not free flowing

* Gastroschisis - show herniation to right of umbillicus, free floating and small fetal abdominal circumfrence

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13
Q

Large intestine

A
  • Cecum
  • On the base of the cecum is the appendix
  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon
  • rectum
  • anus
  • Tenae coli longitudinal bands of muscle at run along it
  • Haustra - pauches that give the colon a segmental appearance
  • Omental appendices - sacks of fat which hang from the surface of the bowel
  • retroperitoneal
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14
Q

Appendix

A

• mobile structure attatched to illiocecal junction
• small branch of SMA : appendicular artery supplies it
• variable locaction of appendix
• retrocecal - tucked up behind the cecum
Appendicitis is main pain in umbilical region, variable position changes the way in which the pain is localines

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15
Q

Paracolic gutters

A
  • depressions between the lateral margins of the colon and posterolateral abdominal wall
  • gutters through which material can pass from one area of peritoneal cavity to another
  • allows relatively blood- free mobilisation of ascending and descending colon by cutting the peritoneum along this
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16
Q

Hirschsprung disease

A

Agagnlionosis ( absence of ganglion cells) in the distal colon and rectum
• affects the enteric nervous system ( myenteric and submucosal plexuses) hence functional obstruction develops as a result of a spasm in the colon

Short segment - 75% ( rectum and distal colon)

Radiography will show bowel obstruction but biopsy is needed

17
Q

Anal canal

A

continuation of large intestine inferior to rectum
• passes through pelvic floor
• puborectalis pulls anteriorly to control defecation

  • Upper Mucosa
    • upper mucosa similar to rectum
    • longitudanal folds called anal columns ( unite inferiorly - anal valves, superiorly - anal sinus)
  • Lower Mucosa
    • below pectinate line is transition zone
    • non keratinised stratified squamous emithelium
    • developmentally - pectinate line represents hindgut-proctodeum junction
18
Q

Haemorrhoids

A
  • venous plexus around anal canal is enlarged
  • Internal haemorrhoids - not as painful due to innervation from hindgut, visceral peritoneum has autonomic nerves that are not sensitive to pain, only distention
  • external haemorrhoids - below pectinate line - somatic innervation, much more painful
19
Q

Perianal fistula

A 
• Anal abscess which is not drained correctly
• leads to fistula across anal sphincters
• usually inflammatory condition
Classified into 4 main
• intersphinteric
• transphinteric
• Extrasphinteric
• Suprasphinteric
20
Q

Anorectal malformations

A
  • wide spectrum of defects in the devlopment of the the lowest portion of the GI and UG tracts
  • may include imperforate anus - no external opening to anus
  • stenosis, agenesis,

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