Lecture 3+4

Question 1

When does the midgut begin? end?

Answer 1

begins inferior to the major duodenal papilla and ends at the junction junction between the 2/3 and 1/3 distal transverse colon

Question 2

arterial supply, venous drainage, and lymph of midgut?

Answer 2

artery: superior mesenteric A.
vein: superior mesenteric V.
lymph: superior mesenteric nodes

Question 3

The midgut loop..

Answer 3

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

Question 4

non-rotation of the mid-gut

Answer 4

caudal limb returns first

small intestine lies to the right, generally asymptomatic

Question 5

reversed rotation of the midgut

Answer 5

midgut loop rotates in a clockwise direction

duodenum lies anterior to transverse colon posterior

Question 6

subhepatic cecum and appendix abnormality

Answer 6

cecum gets adhered to the liver

does not descend to the iliac fossa

may cause difficulty in diagnosis of appendicitis

Question 7

Mixed rotation and volvulus abnormality

Answer 7

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)

Question 8

development of the cecum and vermiform appendix

Answer 8

cecal diverticulum

Question 9

omphalocele

Answer 9

persistence of the abdominal herniation (embryological defect)

in contrast to umbilical hernia it is covered by fetal membranes

Question 10

umbilical hernia

Answer 10

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’

Question 11

Gastroschisis

Answer 11

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

Question 12

Meckel’s diverticulum

Answer 12

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

Question 13

umbilical fistula

Answer 13

omphaloenteric duct remains patent forming a communication between the umbilicus and intestinal tract

fecal discharge from umbilicus
infection of the umbilicus

Question 14

when does the hindgut begin? end?

Answer 14

begins at the junction between the proximal 2/3 and distal 1/3 of the transverse colon

ends half way through anal canal

Question 15

arterial, venous, and lymph of hindgut?

Answer 15

artery: inferior mesenteric A.
vein: inferior mesenteric V.
lymph: inferior mesenteric nodes

Question 16

anal stenosis

Answer 16

narrowing of the anal canal

most likely due to slight dorsal deviation of the urorectal septum as it grows caudally

Question 17

membranous atresia

Answer 17

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

Question 18

anorectal agenesis with fistula

Answer 18

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

Question 19

rectal atresia

Answer 19

the anal canal and rectum are present, but they are not connected

may be due to abnormal recanalization or defective blood supply

Question 20

Hirschsprung disease (congenital megacolon)

Answer 20

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!

Question 21

how is pyruvate transported into the mitochondria after glycolysis?

Answer 21

pyruvate translocase transporter

Question 22

how to pyruvate converted into acetyl-coA

Answer 22

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

Question 23

what are the three domains of the PDH complex?

Answer 23

pyruvate decarboxylase (E1) 
dihydrolipoyl transacetylase (E2) 
dihydrolipoyl dehydrogenase (E3)

Question 24

how is PDH activated

Answer 24

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)

Question 25

How is PDH inhibited?

Answer 25

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

Question 26

what are the 5 cofactors of the PDH complex?

tender loving care for Nancy

Answer 26

TPP (B1) 
lipoic acid (from octanoic acid)
FAD (from B2)  
coenzyme A (from B5) 
NAD (from B3)

Question 27

Wernicke-korsakoff syndrome

Answer 27

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

Question 28

Beriberi wet and dry

Answer 28

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

Question 29

pyruvate dehydrogenase deficiency

Answer 29

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

Question 30

regulation of the TCA cycle?? how?

Answer 30

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

Question 31

mechanism of fluoroacetate

Answer 31

substrate for citrate synthase, which is converted into fluoroacetate which then inhibits aconitase

Question 32

malonate

Answer 32

competitive inhibitor to succinate dehydrogenase due to similarity of structure to succinate