Embryology Flashcards
What does the cephalic limb of primary intestinal loop form?
Duodenum Jejunum Ileum
What does the caudal limb of primary intestinal loop form?
Ileum Caecum Appendix Ascending colon Proximal 2/3 transverse colon
What happens when the abdomen cannot contain intestines anymore during development?
Physiological umbilical hernia forms, around 6 weeks
What happens to the midgut to form the small intestine loops?
270 degree counterclockwise rotation
How does the liver and gall bladder form?
End of 3rd week Is outgrowth of distal end of foregut Link narrows to form the bile duct The bile duct then gives rise to the gall bladder
How is the pancreas formed?
Forms from pancreatic buds
What is atresia?
Complete absence of a lumen
What happens to the cloacal membrane during development?
Divides into urogenital membrane and anal membrane
Anal membrane ruptures at week 9
Open anus forms
What are the 3 stages of kidney development?
Pronephors
Mesonephros
Metanephros
What happens to the mesonephric duct and metanephros during development?
Mesonephric duct = derives kidney around 28 days
Metanephros = persists as funcitoning kidney - forms metanephric blastema
What is the role of the ureteric bud during development?
Diltates to form primitive renal pelvis
Forms ureter, renal pelvis, major and minor calyces and millions of collecting tubes
What causes the ascent of kidneys during development?
Reduction of body curvature and body growth in lumbar and sacral regions
What happens during gonad development?
Germ cells migrate to ridges of gonads along dorsal mesentery
No gonad development if germ cells dont reach them
What happens during femal genitalia formation?
- Primitive sex cords disappear at week 6
- Epithelium proliferation in week 7 to form cortical cords
- Cortical cord splitting, forming cell clusters
- Clusters surround germ cells forming primary oocytes
- Surrounded by follicular cells
- Para and mesonephric duct form = anterolateral surface of urogenital ridge
- Paramesonephric duct intially separated by spetum, then fuse forming uterine canal and upper vagina
- Urogenital sinus forms lower part of vagina
What happens during male genitalia formation?
- Primitive sex cords continue proliferating into medulla
- Testes cords form
- Become separated from epithelium by tunica albuginea
- Mesonephric duct forms vas deferens
- Degeneration of paramesonephric duct
- Mesonephric duct forms main genital tract
- Urogenital mesentery attaches testes and mesonephros to posterior abdominal wall in 2nd month
- Testes descend through inguinal ring over pubic bone but bloody supply retained
What happens during femal external genitalia formation?
- Genital tubercle enlarges and elongates forming clitoris
- Urethral folds form labia minora
- Genital swellings enlarge forming labia majora
What happens during male external genitalia formation?
- Androgens cause elongation of genital tubercule tube
- Phallus forms, pulling urethral folds together, close to forms penile urethra
- 4th month forms complete canal and erithral outlet
- Scrotal swellings form
