Block 2: Gray's Redo Clarifications Flashcards
Processus Vaginalis
what is it?
what happens to it?
parietal peritoneum that precedes the testes (or labia majora in women) as it migrates from a position in the upper wall to outside the abdomen
usually obliterates, leaving a distal portion that surrounds the testes as tunica vaginalis
Explain the relationship b/w the allontois, urachus, and urinary bladder
the urinary bladder is initially drained by the allantois.
this, however, is obliterated during fetal development and becomes a fibrous cord–the urachus.
remnants of the urachus can be found in adults
Where can you find the remnant of the urachus?
median umbilical ligament
What are the main congenital abnormalities of kidney formation?
obstructive uropathy renal agenesis renal hypoplasia multicystic dysplastic kidney double collecting system
Renal Hypoplasia
small kidneys are produced with a decreased number of nephrons
Describe the life outcomes for renal hypoplasia
unilatral: compatible with normal life if the other kidney is normal
bilateral: Potter’s Sequence
Potter’s Sequence
biateral renal hypoplasia that leads to oligohdyramnios, fetal compression and lung hypoplasia
The kidney originates from the
intermediate mesoderm
What are the stages of kidney development?
Pronephros
Mesonephros
Metanephrogenic Mesenchyme
What becomes the definitive kidney?
metanephros
Ureteric bud originates from
the mesonephric duct
What is derived from the ureteric bud (besides the definitive kidney)
collecting system (ureter, renal pelvis, major and minor calyces and collecting tubules)
What is derived from the metanephric blastema?
excretory system (tubules, the nephrons)
Initial function of the ureteric bud
to communicate with the metanephros to initiate and form the metanephric (permanent) kidneys
What would cause renal agenesis?
no ureteric bud
no mesenchyme
no interaction
In the urinary system, the cloaca gives rise to the
bladder and urethra
Cloaca
a hindgut s(x) that’s a common chamber for GI and urinary waste
Urogenital sinus division
upper part: forms the bladder
pelvic part: forms the urethra, some of the reprodutive tract in females and prostatic &* membranous urethra in males
phallic/caudal part: female reproductive tract; spongy urethra in males
What divides the cloaca in 2?
uro-rectal septum
What do the mesonephric ducts develop into?
men: ejaculatory ducts
women: degenerate due to lack of testicular androgens
Foregut contents
esophagus to 2nd part of duodenum; also liver and pancreas
Midgut contents
distal 1/3 duodenum to proximal 2/3 large intestine
Hindgut contents
distal 1/3 of transverse colon, descending colon, sigmoid colon
Stomach rotation
moves caudally and rotates 90 degrees clockwise
What is the result of stomach rotation?
left wall becomes the anterior wall, right side becomes the posterior wall
Describe midgut lengthening
happens with rotation or twisting of the gut tube (90 degree rotation) around the SMA
Midgut reduction
When does this happen? What happens?
Why?
when: Week 10
what: entire midgut length (loop) can be accommodated, so the gut reduces into the abdomen and continues its rotation by 180 degrees
Abdomen is large enough that
What is the result of midgut rotation?
cephalic limb on the L side of abdominal cavity; caudal limb on R lower portion of abdominal cavity
Cloaca is formed when
hindgut joins w/ allantois
Cloaca eventually divides into
urogenital sinus (ventral) and the rectum and anal canal (dorsal)
Mesentary derived from
splanchnic mesoderm
Ventral mesentary in development eventually forms
lesser sac and falciform ligament
Foregut blood supply
celiac artery
Midgut blood supply
SMA
hindgut blood supply
IMA
Pancreas develops from
dorsal and ventral pancreatic bud
Fusion of pancreatic buds
dorsal bud forms the body; ventral bud forms the head & ucinate process
What parts of the GI tract are retroperitoneal?
duodenum (except 1st part); ascending and descending colon
Omphalocele
intestinal loops fail to return from the umbilical cord into the abdominal cavity
Result of omphalocele
herniated loops cause large swelling in umbilical cord
Congenital umbilical hernia
layers of muscle or skin around umbilicus are absent or fail to close properly
some viscera can leave the abdominal cavity and enter the umbilical cored
Total primitive midgut rotation degrees
270 degrees
Left sided colon
rotation only completes to 90 degrees so the colon and cecum will be on L side of abdomen and later parts on the R side
Reversed rotation
midgut rotates clockwise instead of counterclockwise
Stenosis and Atresia of Intestines
due to incompletion or failure of intestinal recanalization
Meckel’s Diverticulum
finger like pouch that develops near the ileocecal junction
represents remaining part of ompalocele (yolk sac)
How is the perineum formed?
urorectal septum fuses w/ cloacal membrane
Hirchsprung’s Disease
what is it?
what causes it?
what: colon dilation (megacolon)
caused by: absence of autonomic innervation in that portion of the colon caused by failure of neural crest cells to properly migrate
Anal Agenesis (without a fistula)
anal canal ends blindly or ha an ectopic opening
Anal agenesis (w/ a fistula)
anal canal may end in a fistula, which opens into the perineum
Anal Stenosis
anal canal constricted and narrowed
What causes anal stenosis?
urorectal septum grows too far dorsally
Imperforate Anus
what is it?
what causes it?
what is it: anus exists in normal location but is covered by a thin layer of tissue
what causes it: failure of the anal membrane to rupture
Anorectal Agenesis
rectum ends blindly but ends in a fistula associated w/ bladder (rectovesicle fistula), urethra in males (rectourethral fistula) or the vagina in females (rectovaginal fistula)
Rectal Atresia
rectum and anus separated by a wedge of tissue
Hepatoduodenal Ligament
where:
significance
where: b/w duodenum and liver
significance: supports the portal triad
Portal Triad
hepartic artery
hepatic vein
bile duct
Caudate lobe location
b/w IVC and fossa of ligamentum venosum
Quadrate Lobe location
lower aspect of visceal surface, b/w gallbladder and a fossa produced by ligamentum teres
Ligamentum Teres
a remnant of the fetal umbilical vein (L)
What separates the caudate and quadrate lobes?
porta hepatis
Clinical significance of the hepatoduodenal ligament
can be clamped to stop profuse bleeding from the liver
Congenital Hydrocele
fluid accumulation in the scrotum
Malrotation
incomplete rotation & fixation of the midgut after passing from umbilical sac and returning to abdominal coelom
Describe how volvulus happens
if the duodenojefjunal flexure doesn’t end up in the right place the small bowel can twist around the axis of the SMA
Describe how volvulus happens
if the duodenojefjunal flexure doesn’t end up in the right place the small bowel can twist around the axis of the SMA
Congenital hydrocele
what is it?
what causes it?
what: collection of serous fluid within the tunica vaginalis
cause: failure of the processus vaginalis to close
Inguinal Hernia
abdominal cavity contents protrude into the scrotum