-
extraembryonic coelom
- coalescence of coelomic spaces in the extraembyronic mesoderm during 2nd week of development
- subdivides lateral mesoderm into somatic mesoderm (associated with chorion/amniotic cavity) and splanchnic mesoderm (associated with endoderm around the yolk sac)
-
somatic mesoderm
- outer layer of lateral mesoderm associated with chorion/amniotic cavity
- forms parietal layers (parietal pleura, parietal pericardium & parietal peritoneum)
-
splanchnic mesoderm
- layers of lateral mesoderm associated with endoderm around yolk sac
- forms visceral layers (visceral pleura, visceral pericardium, & visceral peritoneum)
-
divisions of somatic mesoderm (3rd week)
paraxial, intermediate, lateral
-
intraembyronic coelom
- coalescence of small coelomic spaces appearing in lateral mesoderm
- divides lateral mesoderm into somatopleure (superficial ectoderm + somatic mesoderm) and splanchnopleure (endoderm + splanchnic mesoderm)
-
splanchnopleure
- endoderm + splanchnic mesoderm
- forms gut & viscera (organs)
-
somatopleure
- superficial ectoderm + somatic mesoderm
- forms body wall & parietal layers
-
divisions of intraembryonic coelom
- anterior curve: pericardial cavity
- limbs of curve: pleural/peritoneal cavities (2)
-
pericardial cavity
- rostral/anterior curve of intraembryonic coelom
- surrounds developing heart
-
pericardioperitoneal canals
- connect pericardial cavity with pleural/peritoneal cavity
- dorsal to septum transversum
- lateral to developing gut
-
diaphragm
- separates the pericardial & pleural cavities from the peritoneal cavity
- formed from septum transversum (central tendon), pleuroperitoneal membranes (small dorsal portion), dorsal mesentery of esophagus (crura), body wall (peripheral edges)
-
partitions of intraembryonic coelom
- septum transversum
- pleuro-pericardial membranes (2)
- pleuro-peritoneal membranes (2)
-
fate of dorsal mesentery
suspends entired gut from posterior abdominal wall
-
fate of ventral mesentery
disappears except at most caudal region of foregut to form falciform ligament of liver
-
source of falciform ligament of liver
ventral mesentery
-
formation of primitive mediastinum
- pleuropericardial membranes fuse with mesodermal mesenchyme ventral to esophagus
- separates pericardial cavity from pleural cavities
-
development of diaphragm
- septum transversum: central tendon
- pleuroperitoneal membranes: small dorsal portion
- dorsal mesentery of esophagus: crura of diaphragm
- body wall: peripheral edhes (muscular ingrowth mostly on dorsal aspect)
-
costodiaphragmatic recess
expansion of the pleural cavities into the lateral body wall causing portion of the body wall to form peripheral parts of the diaphragm
-
pectus excavatum
- sunken/funnel chest
- results from short central tendon of the diaphragm which pulls on the inferior portion of the xiphoid portion of the sterum creating a depression of the sternum & anterior chest and flaring of the costal cartilages of ribs 7-10
-
congenital diaphragmatic hernia
- results from failure of fusion of pleuroperitoneal membranes creating a hole (foramen of Bochdalek) posterolaterally (usually on left)
- Morgani hernia: failure of fusion between septum transversum & lateral body wall
- hiatal hernia: delay in descend of stomach
- Bochdalek hernia: posterolateral defect due to failure of fusion of pleuroperitoneal membranes
- abdominal contents in thoracic cavity, patient presents with "flat abdomen"
- negatively affects lung development
-
Morgani hernia
failure of fusion between septum transversum & lateral body wall
-
hiatal hernia
delay in descent of stomach (keeping hiatus larger)
-
Bochdalek hernia
posterolateral defect due to failure of fusion of pleuroperitoneal membranes
-
innervation of diaphragm
- central portion: phrenic n (C3,4,5)
- peripheral portions: lower intercostal nn
-
embryonic layers involved in primitive gut formation
- endoderm: gives rise to epithelium & glands
- splanchnic mesoderm: gives rise to muscular & fibrous elements of gut tube
-
3 embryonic folds
- head fold: involves mouth (stomodeum)
- tail fold: involves anus (proctodeum)
- lateral fold: pinches off dorsal aspect of yolk sac
-
foregut derivatives
pharynx, esophagus, stomach, proximal duodenum (proximal to bile duct), liver, pancreas, gallbladder
-
arterial supply of foregut
celiac trunk
-
arterial supply of midgut
superior mesenteric artery
-
arterial supply of hindgut
inferior mesenteric artery
-
midgut derivatives
small intestines (including duodenum after common bile duct), cecum, appendix, ascending colon, proximal 2/3 of transverse colon
-
hindgut derivatives
distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum, upper part of anal canal
-
tracheoesophageal fold
fusion of two sides forms tracheoesophageal septum dividing esophagus & laryngotracheal tube
-
esophageal atresia
- defect in esophageal development due to malformation of tracheoesophageal septum resulting in a blind end esophagus
- causes polyhydramnios (baby can't swallow)
-
tracheoesophageal fistula
malformation of the esophagus; communication between the esophagus & the respiratory tract
-
esophageal stenosis
- defect of esophageal development in which there is a narrowing of the esophagus
- can lead to short esophagus & congenital hiatal hernias
-
development of stomach
- caudal part of foregut rotates 90* clockwise
- dorsal border forms greater curvature (moves to left)
- ventral border forms lesser curvature (moves to right)
- original left side - ventral
- original right side - dorsal
- left vagus n: anterior vagal trunk
- right vagus n: posterior vagal trunk
-
pyloric stenosis
muscular hypertrophy of gastric pylorus causes constriction of pyloric region of stomach & leads to non-bilious projectile vomiting
-
dorsal mesogastrium
- dorsal mesentery of the stomach
- elongates to form greater omentum
-
omental bursa
- lesser sac of peritoneum
- begins as a series of clefts in dorsal mesogastrium which coalesce forming a single cavity
-
dorsal mesogastrium derivatives
- greater omentum (gastrosplenic ligament, gastrophrenic ligament, gastrocolic ligament)
- mesentery proper
- lienorenal ligament
- transverse mesocolon
- mesoappendix
- mesocecum
- sigmoid mesocolon
- phrenicolic ligament
-
ventral mesogastrium derivatives
- lesser omentum (hepatogastric & hepatoduodenal ligaments)
- falciform ligament & ligamentum teres hepatis
-
source of duodenum
foregut & midgut
-
arterial supply of duodenum
celiac trunk & superior mesenteric artery
-
duodenal stenosis
partial recanalization of duodenum (parts 3 & 4) causing bilious vomit (stenosis below ampulla of Vater)
-
duodenal atresia
- no recanalization of duodenum
- bilious vomit (atresia below ampulla of Vater)
- double bubble sign: fluid building up in stomach & duodenal bulb
-
hepatic diverticulum
- liver bud of endoderm that grows ventrally from distal end of foregut & invades the septum transversum
- cranial portion: liver
- caudal portion: gallbladder
- stalk: cystic duct & common bile duct
-
when does liver start producing bile
12 weeks
-
meconium
first few bowel movements of an infant; contain a large amount of bile (dark green)
-
development of pancreas
- ventral bud: uncinate process & inferior head of pancreas
- ventral bud + distal dorsal bud: main pancreatic duct
- proximal dorsal bud: accessory pancreatic duct
-
annular pancreas
defect caused when the ventral pancreatic bud surrounds the descending duodenum upon rotation & causes obstruction of the duodenum
-
stages of midgut development
herniation, return, fixation
-
midgut development: herniation
when the cranial and caudal limbs do a 90* clockwise rotation around the superior mesenteric artery
-
midgut development: return
- regression of mesonephros
- reduced growth of liver
- relatively small abdominal cavity
-
midgut development: fixation
- leads to fusion of layers of the greater omentum & fusion of greater omentum with transverse mesocolon
- establishes secondarily retroperitoneal structures
-
secondarily retroperitoneal structures
- 2,3,4 parts of duodenum
- pancreas
- ascending colon
- descending colon
-
abnormalities of midgut rotation
- Ileal (Meckel's) diverticulum: incomplete obliteration of vitelline duct
- umbilicoilieal fistula
- omphaloceoele
- gastroschisis
-
urogenital septum
- fuses with cloacal membrane
- divides cloaca into urogenital sinus & anorectal canal
- perineal body: in between
-
pectinate line
divides upper 2/3 of anal canal from lower 1/3
-
urogenital ridge
longitudinal ridge of intermediate mesoderm that runs along dorsal aorta; pushes out from the body wall into the coelom
-
nephrogenic cord
part of urogenital ridge that runs the entire length of the embryo & gives rise to the urinary system
-
pronephros
first kidney which begins development at beginning of 4th weeks but degenerates by the end of the 4th week
-
mesonephros
middle kidney which begins to form at end of 4th week
-
metanephros
- definitive kidney; appears as small projection off mesonephric duct in 5th week
- develops from ureteric bud (metanephric diverticulum) & metanephrogenic blastema (metanephric mass)
-
mesonephric tubules
- connect to mesonephric duct
- in females: degenerate (remnants - epoophoron & paroophoron)
- in males: develop into efferent ductules (remnant - paradidymis)
-
mesonephric duct
- AKA Wolffian duct
- empties into cloaca
- in females: degenerates (remnants - appendix vesiculosa, duct of Gartner)
- in males: forms vas deferens, epididymis, seminal vesicles & ejaculatory duct (remnant - appendix epididymis)
-
metanephrogenic blastema origin
intermediate mesoderm
-
progression of blood supply to kidney
external iliac branches - abdominal aorta branches - renal arteries
-
supranumery renal arteries
multiple renal arteries can exist if arteries do not degenerate properly; can lead to hydronephrosis
-
allantois
connects to cloaca; constricts proximal end to form urachus
-
urachus
extends from the apex of the bladder to the umbilicus (median umbilical fold)
-
cloachal membrane
invagination of ectoderm that fuses with urorectal septum dividing area into urogenital membrane (anteriorly) & anal membrane (posteriorly)
-
perineal body
point where urorectal septumĀ pushes through cloaca & makes contact w/ skin
-
urorecal septum
mesenchyme that pushes through & divides the cloaca into urogenial sinus & anorectal canal
-
UG sinus derivatives
- vesical part: forms majority of urinary bladder (both sexes)
- pelvic part: forms entire female urethra; forms prostatic & membranous male urethra
- penile part: forms penile (spongy) male urethra
-
trigone of bladder
represents portion of bladder where mesonephric ducts were incorporated; becomes overgrown by endoderm
-
renal agenesis
- abscence of kidney due to failure of ureteric bud to form
- unilateral: other kidney will undergo compensatory hypertrophy
- bilateral: incompatible with life
-
polycystic kidneys
kidneys are filled with cysts & nonfunctional
-
pelvic kidney
kidney fails to undergo ascent & remains functional
-
horseshoer kidney
inferior mesenteric artery causes midline obstruction; blocks complete ascent of fused kidneys
-
ectopic ureters
ureters end in places other than bladder (vagina, prostate, urethra)
-
urachal abnormalities
- cysts: improper closure of allantois in region of umbilicus
- sinus: discharge of clear cyst fluid near umbilius
- fistula: constant discharge of urine & cyst fluid from bladder & cyst
-
extrophy of bladder
incomplete closure of musculature of the abdominal wall that causes exposure & erosion of anterior wall of bladder; urine is constantly secreted
-
development of suprarenal glands
- cortex: mesoderm
- medulla: ectoderm + NCC invasion
-
chromaffin cells
develop in medulla of suprarenal glands from NCCs
-
congenital adrenal hyperplasia
abnormal increase in testosterone production by adrenal glands
-
indifferent gonads
- undergo similar development in both male & female
- external cortex & internal medulla
- stage occurs in development of gonads, ducts & external genitalia
-
paramesonephric duct
Mullerian duct; forms alongside mesonephric duct (gonads develop medial to both ducts)
-
AMH
- antimullerian hormone
- AKA mullerian inhibiting substance
- secreted by Sertoli cells to inhibit development of paramesonephric duct, driving it to apoptosis in males
-
TDF
testes determining factor: present on the Y chromosome driving development in male direction
-
Leydig cells
interstitial cells that develop in the mesenchyme outside of primary sex cords; responsible for secretion of testosterone by the 8th week of development
-
primary sex cords
- inward proliferation of mesothelium into mesnchyme; colonized by PCGS
- males: become seminiferous cords
- females: obliterated & replaced by secondary sex cords
-
processus vaginalis
projection of the peritoneum that pusches down the muscle & fascia into future scrotum
-
tunica vaginalis
peritoneal layers that remain with testis in adult after processus vaginalis has been obliterated
-
congenital inguinal hernia
herniation of gut into scrotum through patent processus vaginalis (indirect hernia)
-
cryptorchidism
failure of testes to descend; spermatogenesis may be affected
-
hydrocele
presence of excess fluid in persistant process vaginalis
-
hematocele
presence of blood in persistant processus vaginalis; collection of blood in tunica vaginalis
-
varicocele
veins of pampiniform plexus are elongated & dilates (usually on left)
-
congenitally acquired indirect hiatal hernia
hernia occuring as an adult due to maintained connection between peritoneal cavity & tunica vaginalis (patent processus vaginalis)
-
derivatives of indifferent gonads
- male: testes, seminiferous tubules, rete testis, sertoli cells, leydig cells
- female: ovary, primordial follicles, rete ovarii
-
derivatives of gubernaculum
- male: gubernaculum testis (testicular ligament)
- female: round ligament of the uterus, ovarian ligament
-
derivatives of mesonephric tubules
- male: efferent ductules, paradidymis
- female: epoophoron, paroophoron
-
derivatives of mesonephric ducts
- males: appendix epipdidymis, epididymis, ductus deferens, seminal vesicles, ejaculatory duct
- females: appendix vesiculosa, duct of Gartner
- both: ureter, pelvis, calices & collecting tubules
-
derivatives of paramesonephric duct
- male: appendix testes
- female: uterine tubes, uterus, cervix, superior 1/3 of vagina, hydatid of Morgani
-
derivatives of UG sinus
- male: bladder, prostate gland, prostatic urethra, prostatic utricle, membranous urethra, bulbourethral glands, penile urethra
- female: inferior 2/3 vagina, bladder, urethra, urethral & paraurethral glands, greater vestibular glands
-
derivatives of sinus tubercle
- male: seminal colliculus
- female: hymen
-
derivatives of genital tubercle
- male: glans & body of penis
- female: clitoris
-
derivatives of urogenital folds
- male: ventral aspect of penis
- female: labia minora
-
derivatives of labioscrotal swellings
- male: scrotum
- female: labia majora & mons pubis
|
|