Embyology Flashcards
Early genital ridges consist of..
Coelomic epithelium
Mesonephric ridge
Describe the path of germ cell migration
Found on endodermal wall of yolk sac. Migrate to newly formed genital ridges (ventromedial surface of mesonephric ridge) During migration they increase in number.
Describe differentiation of ovary
Absence of sry gene.
Primitive germ cells divide to form oogonia. Eventually these begin meiosis forming oocytes (stop in prophase of M1)
The primitive sex cords are thought to form the follicle cells that are associated with oocytes.
Held in place by suspensory, round and broad lugs derived from mesonephros
Development of uterine tubes
No sry gene. Therefore, no Mullerian inhibiting substance. Mesonephric duct regresses. Fusion of paramesonephric ducts prior to joining urogenital sinus = uterus. Which will be suspended in position by the broad ligament.
Three basic components of external genitalia
Genital tubercle -> clitoris
Genital folds -> labia minora
Genital swellings -> labia majora
Development of vagina
Paramesonephric ducts fuse above urogenital sinus. Inbetween the two forms a sinovaginal bulb which grows and undergoes canalisation. The lower 2/3 comes from sinovaginal bulb. Upper 1/3 from paramesonephric ducts. The closed caudal end forms part of the vaginal vestibule (hymen)
Effect of teratogen on Pre embryo, embryo, fetus
Pre embryo - death of blastocyst and resorption
Embryo - impacts organogenesis and size
Fetus - impacts growth and development
Why fetus not rejected
Fetal tissue doesn’t present Ag
Maternal immune system downregulated
Decidual barrier
Fetal cells inactivate T cells
Functions of placenta
Synthesis: glycogen, cholesterol, FAs
Hormone production
Transport of substances (maternal Abs, waste products, all nutrients, hormones etc.)
Describe the development of pancreas
Dorsal bud - outgrowth of duodenal endoderm
Ventral bud - outgrowth of endoderm of hepatic diverticulum
Rotation of duodenum (stomach enlarges)
Buds join
Connection forms between two ductal systems
Nerve supply = sympathetic and vagus
