12.9 Anatomy: Embryology 2 Flashcards
What does the endoerm form?
Epithelial lining, organ forms along with mesodermal tissue
What comprises the coelom?
What happens at one month?
Yolk sac, bilaminar disc, amniotic cavity
C-shaped tube
What gives rise to the body wall?
Somatic mesoderm
Ectoderm
What gives rise to the viscera?
Splanchnic mesoderm
Endoderm
How is the coelom formed?
Yolk sac separates from embryo (purse string)
Space that gets pinched off is gut lumen
When are mouth and anus formed?
After 3 weeks of age (ectoderm meets endoderm)
What divides rectum from urogenital tract?
Urorectal septum
Where does the allantois lie? What does it do? What does it give rise to?
Lies in the body stalk, stores nitrogenous waste in some species (not humans)
Gives rise to bladder an d urogenital tract
What do pharangyeal arches become?
Gill remnants (jaws, face)
What is the pharynx lined with?
What forms from it?
Endoderm
Four pouches
What are derivatives of the pharyngeal arches?
Ear canal, tonsils and thymus
How does the heart initially form?
Two endocardial tubes are brought together in the midline (fusion produces heart)
How common are congenital heart defects? What is the most dcommon?
1:200
25% are ventricular septal defects (L/R division)
How does the GIT form?
Rotation around axis of yolk stalk and SMA (large folds across small intestine)
What is omphalocele?
Failure of gut to retract back, GIT outside of body
1:25000
How do the trachea, lungs, liver and pancreas initially appear as?
Endodermal out-pocketings
What causes situs invertus? How common is it?
Cilia generating currents from R to L (primitive groove sets symmetry)
What first appears in development of kidneys and ureters?
Pronephros
What does the mesonephros consist of?
Kidney and ureters (connects to developing testes in males)
What does the penis for by?
Fusion of urogenital folds
What is hypospadiasis? How common is it?
Only partial fusion of urogential folds, urethral opening on base of penis
1:300
When do the ectoderm, mesoderm and endoderm form?
Week 2-3
When is major organogenesis complete by?
By 3 months (1st trimester)
