Lecture 3+4 Flashcards
When does the midgut begin? end?
begins inferior to the major duodenal papilla and ends at the junction junction between the 2/3 and 1/3 distal transverse colon
arterial supply, venous drainage, and lymph of midgut?
artery: superior mesenteric A.
vein: superior mesenteric V.
lymph: superior mesenteric nodes
The midgut loop..
midgut loop has a cranial and caudal limbs
cranial limbs grows rapidly and gives rise to the distal part of the duodenum, jejunum, and part of the ileum
the caudal limb gives rise to the rest of the ileum, cecum, appendix, ascending colon, and proximal 2/3 of the transverse colon
non-rotation of the mid-gut
caudal limb returns first
small intestine lies to the right, generally asymptomatic
reversed rotation of the midgut
midgut loop rotates in a clockwise direction
duodenum lies anterior to transverse colon posterior
subhepatic cecum and appendix abnormality
cecum gets adhered to the liver
does not descend to the iliac fossa
may cause difficulty in diagnosis of appendicitis
Mixed rotation and volvulus abnormality
cecum lies anterior to the pylorus and is fixed to the posterior abdominal wall
may lead to duodenal obstruction (did not complete the final 90 degree turn)
development of the cecum and vermiform appendix
cecal diverticulum
omphalocele
persistence of the abdominal herniation (embryological defect)
in contrast to umbilical hernia it is covered by fetal membranes
umbilical hernia
incomplete closure of the umbilical ring
will appear as a soft swelling covered by skin
it protrudes during crying, coughing, and strain
it can contain omentum and small portions of small intestines’
Gastroschisis
Near the median plane of the abdominal wall.
viscera protrudes into the amniotic fluid
this occurs due to incomplete closure of the lateral folds during week 4
Meckel’s diverticulum
a finger-like projection from the ileum representing retention of the embryonic omphaloenteric duct
close to the ileocecal junction
it contains two kinds of secretory tissue (gastric and pancreatic)
it can mimic appendicitis and/or peptic ulcer
can produce periumbilical pain and internal bleeding
umbilical fistula
omphaloenteric duct remains patent forming a communication between the umbilicus and intestinal tract
fecal discharge from umbilicus
infection of the umbilicus
when does the hindgut begin? end?
begins at the junction between the proximal 2/3 and distal 1/3 of the transverse colon
ends half way through anal canal
arterial, venous, and lymph of hindgut?
artery: inferior mesenteric A.
vein: inferior mesenteric V.
lymph: inferior mesenteric nodes
anal stenosis
narrowing of the anal canal
most likely due to slight dorsal deviation of the urorectal septum as it grows caudally
membranous atresia
thin layer of tissue separates the anal canal from the exterior
due to failure of the epithelial plug to perforate at the end of week 8
anorectal agenesis with fistula
the rectum ends blindly.. but connects to the bladder or urethra in males and vagina or vestibule in females
the result of incomplete separation of the cloaca from the urogenital sinus by the urorectal septum
rectal atresia
the anal canal and rectum are present, but they are not connected
may be due to abnormal recanalization or defective blood supply
Hirschsprung disease (congenital megacolon)
absence of automatic ganglia in the myenteric plexus of the narrow segment
failure of migration of neural crest cells (weeks 5-7)
most common cause of neonatal intestinal obstruction
aganglionic segment has no peristalsis
becomes very dilated!
how is pyruvate transported into the mitochondria after glycolysis?
pyruvate translocase transporter
how to pyruvate converted into acetyl-coA
By oxidative decarboxylation
occurs due to the PDH complex
this reaction is irreversible
the NADH released by the reaction can be used for ATP production
what are the three domains of the PDH complex?
pyruvate decarboxylase (E1) dihydrolipoyl transacetylase (E2) dihydrolipoyl dehydrogenase (E3)
how is PDH activated
PDH kinase and PDH phosphatase
PDH phosphatase dephosphorylates the serine residues on E1
PDH phosphatase is stimulated by calcium (from skeletal muscles), insulin, and catecholamines (cardiac muscle)
How is PDH inhibited?
inhibited by reaction products: acetyl coA and NADH
PDH will be phosphorylated by PDH kinases
kinases are inhibited by pyruvate
kinases are activated by ATP, acetyl coA, and NADH
what are the 5 cofactors of the PDH complex?
tender loving care for Nancy
TPP (B1) lipoic acid (from octanoic acid) FAD (from B2) coenzyme A (from B5) NAD (from B3)
Wernicke-korsakoff syndrome
Due to thiamine deficiency leading to low PDH activity
alcoholics are at risk and those who are malnourished
symptoms:
ataxia, memory loss, Ophthalmolplagia, cerebral hemorrhage, confabulation
Beriberi wet and dry
wet and dry are based on if edema is present
due to B1 deficiency (low PDH activity)
wet: heart failure, decreased ATP, increased CO
dry: muscle wasting and polyneuritis
pyruvate dehydrogenase deficiency
increase in pyruvate and lactic acid levels and alanine
decreased acetyl co-A and ATP
clinical:
lactic acidosis in blood and CSF
neurological defects
usually fatal at early age
therapy:
dichloroacetate inhibits PDH kinase, so it is as active as possible
supplementation
high fat, low carb diet
regulation of the TCA cycle?? how?
citrate synthase:
irreversible reaction
inhibited by product
activated by substrate availability
isocitrate dehydrogenase:
irreversible reaction
allosterically regulated by ADP and Ca
inhibited by ATP and NADH
alpha- KG dehydrogenase:
5 co-enzymes required (same as PDH)
activated by Ca
inhibited by NADH and succinyl CoA
mechanism of fluoroacetate
substrate for citrate synthase, which is converted into fluoroacetate which then inhibits aconitase
malonate
competitive inhibitor to succinate dehydrogenase due to similarity of structure to succinate
