Embryogenesis and Pituitary Gland

Embryogenesis

• Post-fertilization development

• Differentiaiton of single cell zygote

• Production of three distinct germ layers

• Germ layers: ectoderm, mesoderm, endoderm

Ectoderm

• skin, hair, nails, sweat glands

• nervous system: hypothalamus, both lobes of pituitary

• oral and nasal cavity

• repro tract:

Mesoderm

• muscle

• blood vessel

• reproductive system: gonads (male and female), uterus, cervix, part of vagina, epididymis, ductus deferens, accessory sex glands

• urinary and skeletal system

Endoderm

• digestive system (including liver and pancreas)

• respiratory system

• most glands

Adenohypophysis

anterior lobe

Neurohypophysis

posterior lobe

The reproductive system develops in close proximity to and at the same time as the renal system

SRY gene

Controls the pathway towards either male or female development, specifically on the

Y chromosome

Part of the male tract is derived from the mesonephros

• mesonephric tubules —> efferent ducts

• mesonephric ducts —> epididdymis and ductus deferens

The descent of testicles has three phases. They are:

• growth and elongation of the fetal body away from the testes (transabdominal)

• rapid growth of the extra abdominal gubernaculum (transabdominal)

• shrinkage of the gubernaculum within the scrotum (inguinal-scrotal)

Two common testicular descent abnormalities are:

• cryptorchidism

• inguinal herniation

The uterus and vagina result from a fusion of the paramesonephric ducts.

A freemartin is a heifer born twin to a bull. The heifer calf is sterile, but the bull calf is fertile.