L35: Abdominal Cavity I Flashcards
(22 cards)
Contributions of embryologic germ layers to the abdominal cavity/contents
- Ectoderm: lining of anus (proctodeum) and mouth (stomodeum)
- Splanchnic mesoderm: muscle, bone, CT and other layers of gut and gut-derived abdominal organs
- Endoderm: lining of gut and gut-derived abdominal organs
What is recanalization of gut tube? Clinical relevance of failure of this to occur
- Gut tube is solid tube early in development. Process of recanalization is hollowing out of this tube.
- Failure/error in this process leads to atresia (blockage) or stenosis (narrowing) of gut tube
What embryologic germ layer gives rise to mesenteries?
- Splanchnic mesoderm
What are mesenteries? Two types?
- Double layer of peritoneum that connects organs to the body wall
- Two types of peritoneum: visceral (lines organs) and parietal (lines inside of body wall)
- Two types of mesenteries: ventral and dorsal
Remnants of ventral mesentery?
a. ) Falciform ligament (liver to ventral body wall)
b. ) Coronary ligament (liver to diaphragm)
c. ) Lesser omentum (liver to diaphragm and stomach)
3 relationships of organs to mesenteries
- ) Intraperitoneal: organs suspended in mesentery
- ) Primarily retroperitoneal: organs always external / behind peritoneum
- ) Secondarily retroperitoneal: organs developed in mesentery, but d/t fusing during development are now behind mesentery
Which organs are intraperitoneal?
- Stomach, spleen, transverse colon
Which organs are primarily retroperitoneal?
- Esophagus, rectum, anal canal, kidneys
Which organs are secondarily retroperitoneal?
- distal 2/3rds duodenum, ascending and descending colon
Which organs are retroperitoneal?
- SAD PUCKER
- S: suprarenal glands
- A: aorta, vena cava
- D: duodenum
- P: pancreas
- U: ureters
- C: colon – ascending/descending
- K: kidneys
- E: esophagus
- R: rectum
Describe divisions of the embryologic gut: note what structures are located in each division, the outpocketings/diverticula of each and major blood supply to each
- ) Foregut: pharynx, esophagus, stomach and proximal 1/3rd of duodenum. Outpocketings include pharyngeal pouches, lower resp system, liver, pancreas and GB. Blood supply = celiac trunk
- ) Midgut: small intestine (except proximal 1/3rd duodenum), cecum, appendix, ascending colon and proximal 2/3rd of transverse colon (to left colic flexure). Gives rise to yolk stalk. Blood supply = SMA.
- ) Hindgut: distal 1/3rd of transverse colon, descending colon, sigmoid colon, rectum and superior portion of anal canal. Outgrowths include urinary bladder and most of urethra. Blood supply = IMA
Describe development of stomach
- Dorsal border growth exceeds ventral border growth = lesser, greater curvatures result
- 90 degree clockwise rotation along longitudinal axis = lesser curvature to right, greater curvature to left = R vagus on dorsal surface and L vagus on ventral surface
From what germ layer does the spleen develop?
- Mesoderm
Describe development of intestines
- Midgut forms a U-shaped loop with SMA as axis and yolk stalk at apex
- Counter-clockwise rotation of intestines around SMA
- Cecum descends to lower right and caudal midgut typically elongates
- Rotation presses many organs against posterior body wall and peritoneum fuses to dorsal body wall causing secondarily retroperitoneal configuration of some organs
What is the cloaca? What does it form from? What occurs with this structure during development? Describe
- Cloaca = common sewer (urine and fecal matter deposits here)
- Derived from caudal hindgut
- During development urorectal septum divides allantois and yolk stalk separating cloaca into urogenital membrane and anal membrane.
- Anal membrane separates caudal hindgut from proctodeum
What is polyhydramnios?
- Excess accumulation of amniotic fluid in utero. Can result from various embryologic pathologies including a trachea-esophageal fistula/esophageal atresia, duodenal atresia etc. as the fetus consumes the amniotic fluid turning it over and over again, extruded via allantois
From what does the liver, GB and pancreas develop?
- Distal foregut. Pancreas forms from two outpocketings: ventral and dorsal buds
Describe anomalies from errors in pancreatic development
- ) Bilobed ventral pancreatic bud: splitting of ventral bud into two lobes and failure of buds to fuse
- ) Annular pancreas: fusion of ventral and dorsal buds occurs by wrapping of pancreatic tissue around duodenum causing constriction of gut
Describe anomalies from errors in duodenal development
- Duodenal stenosis
- Duodenal atresia
- Both result from errors in recanalization
Describe anomalies that result from developmental errors in midgut development
- Volvulus: piece of intestine folds around itself or other structures causing obstructions
- SMA compresses transverse colon
- Intestines develop inside mesenteries forming an internal hernia sac
What is the pectinate line?
- Line separating anal canal into that derived from hindgut (endoderm) and that derived from proctodeum (ectoderm)
- Pressure and stretch is detected above pectinate line (no pain)
- Pain detected below pectinate line
Describe anomalies resulting from errors in cloacal development
- Persistent anal membrane (non-perforate anus): anal membrane usually degenerates to ensure continuity between upper and lower parts of anal canal
- Anoperineal fistula: communication of rectum to area on perineum other than anal pit
- Rectourethral fistula: communication of rectum to urethra – feces comes out of urethra
- Rectovaginal fistula: communication of rectum to vagina – feces comes out of vagina
