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Ch. 4: Embryogenesis - Pituitary, Male and Female Repro Tracks - Coggle…
Ch. 4: Embryogenesis - Pituitary, Male and Female Repro Tracks
Differentiation: process whereby a group of unspecialized cells develop into recognizable groups of cells that have a common function
Endoderm: inner layer of cells
- Digestive system - liver and pancreas as well
- Respiratory system
- Most glands
Mesoderm: middle layer of cells
- Muscle
- Blood vessels
- Reproductive organs - gonads, uterus, cervix, part of vagina, epididymis, ductus deferens, accessory sex glands
- Urinary system
- Skeletal system
Ectoderm: outermost layer of cells
- Skin
- Hair
- Nervous System - hypothalamus and both lobes of pituitary
- Oral cavity
- Nasal Cavity
- Reproduction track
Pituitary Gland: originates from the brain and roof of the mouth
- Hypophysis = pituitary
- Adenohypophysis = anterior lobe
- Neurohypophysis = posterior lobe
Anterior Lobe: originates from tissue in the roof of the embryo's mouth called the stomodeal ectoderm
- Gives rise to Rathke's pouch, which grows dorsally from the roof of the mouth
- The cells of Rathke's pouch differentiate to form the adenohypophysis
Posterior Lobe:develops from the floor of the brain and grows ventrally toward's Rathke's pouch to form the infundibulum
- The infundibulum differentiates to form the neurohypophysis
Sphenoid Bone: begins to form around both the anterior and posterior pituitary
- Forms a protective structure known as the stella turcica
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Male Differentiation: the Y chromosome contains a sex determining regino (SRY) that controls the pathway towards male development
- Development is an active process
Mesonephros: part of where the male tract is derived from
- Mesonephric tubules will form efferent ducts
- Mesonephric ducts will form epididymis and ductus deferens
- Mesonephric tubules will male conenctions with primitive sex cords via the rete testis
- The rete testes will connect the seminiferous tubules to the efferent ducts
- The mesonephric duct will give rise to the epididymis and the ductus deferens
Testes Descent: involve two relatively unrelated phenomena
- A ligamentous structure called the gubernaculum moves testes from retroperitoneal position to the scrotum
- The visceral and parietal vaginal tunics cover the testes and travel with them; these two layers are separated by the vaginal cavity (continuous with peritoneal cavity
- There are three phases to descent:
Rapid growth of the extra abdominal gubernaculum
- Transabdominal
- Most important component of testicular descent
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Shrinkage of the gubernaculum within the scrotum
Growth and elongation of the fetal body away from the testes
Peritoneal Layers: vaginal process is continous with peritoneal cavity
- Visceral vaginal tunic - layer immediately adjacent to/on the testes
- Parietal vaginal tunic - layer away from the testes
- These two tunicae are slippery and allow free movement of testes
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Common Abnormalities:
- Cryptorchidism
- Inguinal Herniation
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Inguinal Herniation: when a portion of intestine passes through the inguinal canal into the vaginal cavity
Female Differentiation: when the SRY gene is absent female genes are expressed and male genes are inhibited
- Females have an X chromosome and lack the SRY gene
- Development is an active process, NOT by default in the absence of the SRY
- Gonad and duct system originates behind the peritoneum (retroperitoneal)
- Female track is sandwiched between the genital fold that will become the broad ligament
The epithelial cords (sex cords) fragment into cellular clusters
- Each encloses a rimitive germ cell
- Don't penetrate deeply intoovary - primordial follicles develop around outer surface of ovary
Female Follicles: develop throughout prenatal life and eventually the number of gametes will be maximize
- Female embryo is a pool of oocytes that will undergo folliculogenesis throughout the females reproductive lifetime
Paramesonephric Ducts: the oviducts, uterus, cervix, and cranial vagina develop from this
- These ducts will fuse together
- The degree of fusion determines the type of uterus the animal has
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Freemartinism: sterile female cow resulting from shared chorion and cotyledons and thus blood supply with a male twin