Anatomy to Histology Flashcards
What vitamin cofactor is involved in delta-aminolevulinic acid formation? What process is this?
Vitamin B6 (pyroxidine, converted to the pyridoxal phosphate cofactor)
Heme synthesis
1st step is B6 co-factor assisted conversion of:
[glycine and succinyl-CoA] to [delta-aminolevulinic acid]
Mushroom ingestion and severe hepatotoxicity – toxin and mechanism?
alpha-amantin (Amanita phalloides/death cap mushrooms)
inhibits RNA Pol II
What causes duodenal atresia? What causes intestinal atresia distal to the duodenum (jejunal, ileal, and colonic atresia)? What is the classic finding?
Duodenal atresia due to failure to recanalize (associated with trisomy 21).
Jejunal, ileal, colonic atresia due to vascular accidents in utero (they are NOT cause by abnormal fetal development and thus not congenital malformations).
- Diminished intestinal perfusion leads to ischemia of a segment of bowel, with subsequent narrowing or obliteration of the lumen (ileum most often affected).
- If a major vessel is occluded (such as the SMA), the area of intestinal wall necrosis is large. A blind-ending proximal jejunum is formed with dissolution of a long length of small bowel and absence of associated dorsal mesentary. Terminal ileum distal to atresia assumes a spiral configuration around an ileocolic vessel to form the “apple-peel deformity”.
What is apple-peel atresia due to? What else is seen?
small bowel distal to atresia (due to vascular accident/occlusion/ischemia) assumes a spiral configuration around an ileocolic vessel
occurs in atresia distal to the duodenum (jejunal, ileal, colonic atresia)
also see blind-ended proximal jejunum with dissolution of long length of small bowel and absence of associated dorsal mesentery.
What part of the duodenum is associated with the ampulla of Vater (site where pancreatic and common bile ducts merge)? What part of the duodenum is associated with the uncinate process of the pancreas and SMA?
2nd part of duodenum (descending part): ampulla of Vater
3rd part of duodenum (transverse/horizontal): uncinate process and SMA/SMV
What does the ventral pancreatic bud form? What does the dorsal pancreatic bud form?
Ventral:
uncinate process, inferior portion of head, and main pancreatic duct of the pancreas
Dorsal: most of head (superior), body, tail, and accessory pancreatic duct
What is pancreas divisum?
ventral and dorsal pancreatic buds fail to fuse at 8 weeks
pancreatic ductal systems remain separate, with the accessory duct draining the majority of the pancreas (usually clinically silent, but may predispose to recurrent pancreatitis)
Normally the proximal part of the accessory pancreatic duct degenerates (or can persist as a lesser duct) and the distal portion fuses with the ventral/main duct to become the main pancreatic duct.
Name the structures that are retroperitoneal.
SAD PUCKER
Suprarenal / adrenal glands Aorta and IVC Duodenum (2nd to 4th parts) Pancreas (except for tail) Ureters Colon (descending and ascending) Kidneys Esophagus Rectum (partially)
Male infant fails to pass meconium - dimple instead of anal opening found? Association?
Imperforate anus - spectrum of disorders associated with abnormal development of anorectal structures (most often associated with fistulas, could present with meconium discharged from urethra or vagina)
Pts most often have other congenital malformations, most commonly urogenital tract anomalies.
Mutation in Lynch syndrome? Inheritance? Portion of colon affected? Other associations?
mutation of DNA nucleotide mismatch repair genes
autosomal dominant
affects the proximal colon / right-sided
Lynch syndrome pts also have an increased risk for ovarian and endometrial carcinoma (in addition to colorectal carcinoma)
What is SMA syndrome?
transverse (3rd) part of the duodenum become entrapped between the SMA and aorta, causing symptoms of intestinal obstruction
occurs when angle between aorta and SMA critically decreases, secondary to diminished mesenteric fat (e.g., loss in body weight), pronounced lordosis, or surgical correction of scoliosis
What is posterior to the pancreas? Is it peritoneal or retroperitoneal?
left kidney, aorta, and IVC posterior
tail is peritoneal
rest is retroperitoneal
What portion of the GI tract is affected by Hirschprung’s? Genetic associations?
rectum is ALWAYS involved (neural crest cells migrate caudally)
sigmoid colon involved in 75% of cases
associated with mutations in the RET gene
associated with Down syndrome
What is the omphalomesenteric duct? Conditions associated with abnormalities and common features?
Vitelline duct that connects the midgut lumen with the yolk sac in early embryo – involutes by the 7th week, but failure to involute could lead to:
- persistent duct
- Meckel diverticulum (true diverticulum)
- vitelline sinus
- vitelline duct cyst
common features of the above are connections to the ileum and umbilicus by a fibrous band
How is the lac operon suppressed in the presence of glucose? How is it activated in the presence of lactose?
glucose decreases cAMP levels; without cAMP, CAP cannot bind positive regulatory site upstream of promotor
(high cAMP levels are needed to bind CAP – cAMP-CAP binds a region upstream of promotor to positively regulate lac operon transcription)
Lactose binds the repressor protein, which can no longer bind the operator and block transcription of lac operon genes
