MIDTERM Flashcards
What is a hormone?
Signalling molecules that modulate the activity of a target tissue.
When is sex determined during development?
At time of fertilization based on presence of Y chromosome.
What are the stages of early embryogenesis?
Oocyte is fertilized to form zygote that undergoes rounds of division - @ 16 cells = formation of blastocyst (1st round of cell differentiation).
What are the components to a blastocyst and what do they do?
Trophectoderm – will form placental cells
Inner Cell Mass – will form embryonic cells.
What cells are totipotent? Multipotent? Pluripotent?
Totipotent – cells of zygote: can differentiate into any type of cell Multipotent – trophectoderm: can differentiate into any cells within a cell lineage
Pluripotent – ICM: differentiate into any cells in embryo.
What is gastrulation?
ICM differentiate to form the 3 germ layers from epiblast and hypoblast: Mesoderm, Ectoderm, Endoderm.
What does the Mesoderm make up?
Muscle, Skeleton, Cardiovascular, Reproductive, Urinary.
What does the Ectoderm make up?
Skin, nervous system, hair, external parts of reproductive tract.
What does the endoderm make up?
Digestive system, lungs, endocrine system.
What are primordial germ cells?
Founder cells for the germline in animals.
Explain the process of the formation of primitive sex cords.
PGCs migrate to the gonadal ridge where they colonize and form the primitive sex cords based on interaction with the gonadal somatic cells (spermatogonial stem cells or oogonia).
Explain the steps to sexual differentiation of the male.
Presence of SRY gene = production of testes determining factor = testes develop = Sertoli cells secrete AMH = degeneration of paramesonephric ducts and differentiation of Leydig cells = production of testosterone = development of male reproductive organs.
Explain the steps to sexual differentiation of the female.
No SRY = No TDF = ovaries develop = No AMH = paramesonephric ducts become cranial reproductive organs.
How are spermatogonial stem cells formed?
Factors secreted by testis induce the differentiation of PGCs to SSCs that develop into sperm.
What are the steps to testicular descent?
Fusion of the gubernaculum and peritoneum; Gubernaculum grows, pulling testis through inguinal ring; Gubernaculum begins to digress, pulling the testis further.
What is the development and regression of the gubernaculum dependent on?
Dependent on secretion of insulin like-3 from Leydig cells.
What are the two abnormalities that can occur during testicular descent?
Cryptorchidism – failure of testis to descent; Inguinal herniation – intestines pass through inguinal canal.
What are the changes in embryo during female sexual differentiation?
Mesonephric ducts (epididymis in male) regress, paramesonephric ducts stay; Paramesonephric ducts form oviduct and uterus – fuse to form cervix and uterine body; Urogenital sinus becomes cranial vagina.
What are the major events of embryogenesis occurring in each trimester?
1st – migration of PGCs and development of sex cords; 2nd – development of female or male ducts and testes/ovaries – formation of broad ligament in females; 3rd – testicular descent.
How does the pituitary change with sexual differentiation?
Similar in male and female fetuses, seems to only change post-natal only.
Outline the steps of sexual differentiation of the hypothalamus.
Female = fetal ovary produces E2 that cannot pass through blood-brain-barrier which causes the development of the surge center; Male = fetal testis produces T that enters brain where it is converted to E2 causing the defeminisation (nondevelopment) of the surge center.
How are Freemartin cows formed?
Twin calves where one is male and other is female – chorions fuse and share blood supply – T from male affects brain of female = female hypothalamus defeminizes and internal reproductive structures do not form.
What are the two main functions of the male reproductive tract?
Manufacture and deliver sperm; Androgen production.
What is the function of the spermatic cord, ductus deferens and cremaster muscle?
Suspends testis in scrotum via inguinal canal, pathway for nerves, blood, lymph, contributes to regulation of testis temperature; Ductus for sperm transport; Muscle supports testes, aid blood flow by pumping action on pampiniform plexus.
