Embryology Flashcards
Endoderm
gut, liver, lungs, thyroid, tonsils, parathyroid glands
Mesoderm
skeleton, muscle, kidney, heart, blood, gonads, cartilage, dermis, circulatory system body cavity
ectoderm
skin, nervous system
Hydatidiform Mole
formed from trophoblast (outer layer)
Appearance of grape like clusters
Defect in paternal genome (genomic imprinting)
secrete high levels of hcg - syncytiotrophoblast
may become invasive (choriocarcinoma)
hydatidiform mole may become
choriocarcinoma
teratoma
mass from remnants of primitive streak usually in sacral region
multiple tissue types- ectoderm, endoderm, mesoderm
3x more common in female fetuses
Ectopic pregnancy- most common site
ampulla of tube
tubal implantation
ectopic pregnancy most commonly seen in women who
have had endometriosis, prior surgery, pelvic inflammatory disease
skin layers
epidermis: ectoderm
dermis: mesoderm-somatopleure and dermatome
melanocytes: neural crest cells
langerhans cells: mesoderm
Waardenburg syndrome
disrupted differentiation of neural crest cells- cause hearing loss and changes in coloring (pigmentation) of hair, skin, eyes
- eyes are pale blue or different colored
- patch of white hair
Piebaldism
rare autosomal dominant disorder of melanocyte development characterized by congenital white forelock and multiple symmetrical hypopigmented or depigmented macules
RET proto oncogene
expressed by neural crest cells and encodes tyrosine kinase- provides instructions for producing signaling protein which is essential for normal development of several inds of neurons (including those in intestine) and autonomic control of functionss uch as heart rate, normal renal development and spermatogenesis
Most common cause congenital hydrocephalus
aqueductal stenosis- dilated lateral ventricles, normal 4th ventricle.
dilated 4th ventricle and normal 3rd and laterl ventricles- dandy walker syndrome or obstruction of foramina of luschka and Magendie
Hydrocephalus CF
enlarged cerebral ventricles, mental retardation, spastic paraparesis, adducted thumbs
may occur as chromosomal abnormality, prenatal infection, non-genetic structural anomaly
craniopharyngiomas
derived from oral ectoderm (rathke’s pouch)
impinge upon pituitary stalk resulting in absence of ADH and diabetes insipidus
Can also cause bitemporal hemianopia (loss of visual field on the same side
Cerebellar cortical development
external granule layer is proliferative zone from which cells migrate inwards (away from surface)
cerebral cortical development
pyramidal neurons radially migrate toward superficial layer
(inside out pattern of formation)
earliest neurons formed are placed in deepest layers
early part- multi polar neurons with many neurites which then change to bipolar neurons
cerebellum function
coordinate timing and force of muscular contractions so that skilled, voluntary movements are appropriate
integrates information into execution of movement
Spinal bifida meningocele
contains meninges with csf
spina bifida meningomyelocele
meninges and spinal cord
spina bifida myeloschisis or rachischisis
neural tube has not closed, severe sensory and motor deficits
spina bifida occulta
defect in vertebral arch without a cyst
tuft of hair on back
Anencephaly
crania bifida- neural folds do not fuse in the cranial region of neural tube (failure of cranial neuropore to close)
skull never forms, brain tissue degenerates while in contact with amniotic fluid
most likely site of detachment of retina
between pigmented epithelial layer and rods and cones
connexin 26 mutation
Connexin proteins are gap-junction proteins that are necessary for cells to communicate with eachother- without sufficient levels of connexin 26, potassium flow from hair cells in cochlea is disrupted, resulting in high levels of K in organ of corti–> profound sensorineural hearing loss
Ectodermal dysplasia
teeth do not develop properly because they arise from ectoderm of oral cavity as do hair follicles
inability to tolerate heat due to lack of sweat glands
foregut contents
celiac artery
stomach, liver, gall bladder, first 1/2 of duodenum, pancreas
(spleen is the exception because it’s mesoderm derived)
midgut contents
superior mesenteric artery
second 1/2 of duodenum, SI, proximal large intestine
hindgut contents
inferior mesenteric artery
distal large intestine, sigmoid colon, rectum/anorectal canal
duodenal atresia and stenosis due to
incomplete recanalization or by vascular accidents- gut strangulations from malrotation, volvulus, omphalocele
atresia- parts 2 and 3 of duodenum
stenosis- parts 3 and 4
vomit bile upon overfilling of duodenum with bile because no place for bile to pass distally
blood supply to duodenum is
dual
first half- celiac artery
second half- sma
apple peel atresia
10% of all atresias
in proximal jejunum, intestine is short, with portion distal to lesion coiled around mesenteric remnant
annular pancreas
bilobed ventral pancreatic bud is formed, buds migrate around duodenum in opposite directions strangulating duodenum which can lead to duodenual stresia/stenosis
malrotation of gut
gut did not rotate normally
can be in varying degrees of strangulation, resulting in varying degrees of vascular compromise
increased change of tissue necrosis occurring with increasing severity
mecke’s diverticulum/fistula/cyst
stalk of yolk sac remains attached to body wall and can be patent or not or cyst like
generally- ileal but can be gastric/pancreatic/colonic
positioinal anomalies
complete/ partial situs inversus
gastroschisis
failure of ventral body wall to close properly
loops herniate directly through abdominal wall into abdominal cavity
omphalocele
failure of part of developing gut to return to abdominal cavity following its normal herniation into umbilical cord- defect is covered by reflection of amnion by umbilical cord
congenial megacolon- hirschsprung disease
anomaly in craniocaudal migration of neural crest cells
mutations in RET protooncogene involved sometimes
lack of ganglion cells in myenteric and submucosal plexuses in sigmoid colon or rectum
segment becomes constricted, causing normal, proximal section of bowel to distend with feces
malrotation with midgut volvulus
bilious emesis, abdominal distention, high pitched bowel sounds-> obstruction
severely dilated sigmoid colon with “coffee bean” shape is very suggestive of volvulus
hypertrophic pyloric stenosis
non-bilious emesis presenting 4-6 weeks after birth
distended stomach
caterpillar sign
gastric outlet obstruction that results from congenital thickening of muscle of pylorus - results in narrowing of lumen of pylorus and outlet to the duodenum
fluid restriction followed by pyloromyotomy is curative tx
respiratory system
respiratory diverticulum is outgrowth of endodermal tube (foregut)
epithelium is derived from endoderm
cartilaginous, muscular, connective tissue components of trachea and lung are derived from splanchnic mesoderm
tracheoesophageal septum
responsible for separating tracheal primodrium from esophageal primordium
oligohydramnios
less urine output= less fluid
1) commonly due to early leaking of amniotic fluid due to premature rupture of membranes–> thoracic wall movement occuring with fetal breathing may be restricted- bad for lung development
2) also due to fetal rectal anomalies- amniotic fluids produced my fetal kidneys- polycystic kidneys, hydronephrosis, renal agenesis can cause oligohydramnios and are commonly associated with lung hypoplasia and limb malformations
polyhydramnios
less swallowing=more fluid
tracheoesophageal fistulae associated with polyhydramnios- blind esophagus is most common (proximal esophageal atresia with distal TEF)
TEF complications
polyhydramnios
pneumonitis
pneumonia
Potter sequence/syndrome
bilateral renal agenesis oligohydramnios lung hypoplasia clubbed feet, bowing of legs potter's facies- prominent infraorbital folds, flattened nose, parrot beak nose, recessed chin, skin crease, hypertelorism (inc distance between two organs like two eyes) growth retardation brachycephaly (shorter head)
diaphragm develops from
septum transversum, pleuroperitoneal membranes, dorsal mesentery of esophagus, and lateral body walls
muscle derived from 3, 4, 5th cervical somites
motor innervation from C3, 4, 5 via phrenic nerve so is sensory
most common congenital defect of diaphragm
congenital diaphragmatic hernia
-defective formation and fusion of pleuroperitoneal membranes with other parts of diaphragm (usually on one side)- part of gut can pass through thorax, can cause hypoplastic development of lung
left side of diaphragm involved 4-8 times more frequently probably because left pericardioperitoneal canal is larger and closes later
can be corrected at birth and in utero, but severe pulmonary hypoplasia and insufficiency may be fatal
diminished braeth sounds- usually at left side, heart sounds heart louder in right chest because mediastinum is displaced, abdomen is often scaphoid because abd contents are displaced into chest
