Embryology III Flashcards by Maggie Musso

What are the three parts of the gut tube?

Foregut
Midgut
Hindgut

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What are the parts of the foregut?

Esophagus, stomach, liver, gallbladder/bile ducts, pancreas, spleen, upper duodenum

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What are the parts of the midgut?

Lower duodenum, jejunum, ileum, cecum, appendix, ascending colon, proximal 2/3 of transverse colon

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What are the parts of the hindgut?

Distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum, upper anal canal

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What is recanalization?

Perforation of the gut tube

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What is stenosis?

A congenital malformation in which partial canalization occurs

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What is atresa? How does it present?

A congenital malformation in which no canalization occurs; cannot pass waste, presents with vomiting

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Which mesentery is found only in the foregut?

Ventral mesentery

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What are the two parts of the ventral mesentery?

Falciform ligament

2. Lesser omentum

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Describe the dorsal mesentery.

Forms the posterior wall of the gut tube, spans the entire length of the gut

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The left umbilical vein (there is only one umbilical vein) uses the ___ as a door to the liver. Later, this becomes obliterated to form ___.

Lower free edge of the falciform ligament; ligamentum teres (round ligament of liver)

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Describe the rotation of the stomach.

Stomach moves 90 degrees to the right (clockwise) on the longitudinal axis

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Describe the rotation of the midgut; how does this occur?

Midgut moves 270 degrees to the left (counterclockwise) using the SMA as an axis; physiological herniation

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When does physiological herniation occur?

Between weeks 6-10

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What is omphalocele?

Persistence of physiological herniation of abdominal contents into the umbilical cord (failure of return of intestine to abdominal cavity)

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The liver, gallbladder, and biliary duct system arise as a ventral outgrowth known as the ___ from the distal part of the foregut early in the fourth week.

Hepatic diverticulum

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What does the ventral pancreatic bud become?

Uncinate process, part of head and main pancreatic duct

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What does the dorsal pancreatic bud become?

Remaining pancreas

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What normally happens to the pancreatic buds?

They fuse.

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What is an annular pancreas? How does this present?

A congenital abnormality in which the pancreatic buds form a ring causing duodenal obstruction due to incomplete fusion; vomiting with bile

What is the cloaca?

Expanded terminal part of the hind gut

What divides the cloaca?

Urorectal septum

What are the two parts of the cloaca?

Urogenital sinus and anal canal

What does the urogenital sinus become?

Urinary bladder

What is the pectinate line?

Where endoderm of hind gut meets ectoderm; rupture of the cloacal (anal) membrane

What is found above the pectinate line?

1. Portal system (superior rectal vessels from IMA) | 2. GVA innervation (painless)

What is found below the pectinate line?

1. Caval system (inferior rectal vessels from internal pudendal) 2. GSA innervation (painful)

What is congenital megacolon (Hirschprung's)?

Failure to pass meconium in a full term baby due to failure of neural crest cell migration, leading to obstruction and colonic dilation (no peristalsis)

What are the 3 vessels and 2 ducts of the umbilical cord (connecting stalk)?

1-2. Umbilical arteries 3. Left umbilical vein 4. Allantois 5. Vitelline duct

What is the fibrous element of allantois?

Urachus

What does the obliterated urachus form?

MediaN umbilical ligament

What does the obliterated umbilical artery form?

Medial umbilical ligament

What is Meckel's diverticulum?

Remnant of the vitelline (omphaloenteric duct)

What is the rule of 2's for Meckel's diverticulum?

- 2" long - 2' from IC valve - 2% of population - 2% are symptomatic - 2 types of ectopic tissue - 2 years of age at clinical presentation - 2x more common in males

The intermediate mesoderm gives what two organs?

1. Kidney | 2. Gonads

What are the two parts of the mesonephros?

1. Mesonephric tubules | 2. Mesonephric ducts

What do the mesonephric tubules become?

Excretory organs - vas, epididymis, ejaculatory ducts in males

What do the mesonephric ducts become?

Uteric bud and trigone

What does the metanephros become?

Permanent kidney

The metanephros forms from 2 sources - what are they?

1. Ureteric bud | 2. Metanephrogenic blastema

What does the uretric bud form?

Ureter, renal pelvis, calices, collecting tubules

What does the metanephrogenic blastema form?

Nephrons

As the bladder enlarges, distal parts of the mesonephric ducts are incorporated into its dorsal wall - what does this form?

Trigone of the bladder

The bladder is all derived from ___ except for the ___ which is derived from the mesoderm.

Endoderm; trigone

The trigone is a triangular shaped area connecting the opening of ___ and the ___.

2 ureters; urethra

Two movements occur - the kidneys ___, the gonads ___.

Ascend; descend

What is a pelvic kidney?

Kidney stays in pelvis

What is a horse shoe kidney?

Lower poles of two kidneys unite, usually stops at the origin of IMA.