Embryology Flashcards
Embryology of testicular descent
o Starts after 3rd month of pregnancy and continues to birth
o Gubernaculum testis arises 7th week, attaches from lower part of testicle to genital swelling (future scrotum)
o Arise from urogenital ridge at 5-6th week of gestation and descends through abdo cavity to the scrotum
o Testis takes layers of abdominal wall during descent
▪ Peritoneal lining forms tunical vaginalis
▪ Remains connected to peritoneal cavity by processus vaginalis which atrophies and closes with time (1st year or life)
Embroylogy of breast
o 4th week of gestation
▪ Paired ectodermal thickenings form mammary ridge (milk line) from axilla to medial thigh
• Supramammary nipples or glands can form on these lines
• All disappear in humans except for 4th ICS
o 5th week
▪ Proliferation of endoderm to form the primary mammary bud
o 10th week
▪ Primary bud begins branching
▪ Branches to secondary buds by the 12th week, eventually forms mammary lobules
▪ Mesodermal reaction to supply stromal elements
o 20th week
▪ Lumina coalesce to form lactiferous ducts (under hormonal influence from placenta)
o Lobules form under influence of progesterone/estrogen at puberty
