Organogenesis of the reproductive system (lec 5+6) Flashcards
In the Mesoderm, what important structures are developed in the Reproductive system?
- Gonads (male and female)
- Uterus, cervix, part of vagina
- Epididymis, vas deferens
- Accessory sex glands
How many layers are in the inner cell mass of a embryo and what regions do they give raise to in an embryo?
- Endoderm = digestive system, lungs, endocrine system
- Mesoderm= muscle, skeleton, cardiovascular and reproductive system
- Ectoderm = nervous system, skin and hair
In the ectoderm, what important structures of developed in the nervous system and reproductive system?
NS = Hypothalamus, posterior pituitary, anterior pituitary
RS = portions of the vagina and vestibule, penis, clitoris
In the Endoderm, what important structures of specifically developed for reproduction?
Primordial germ cells from the yolk sac
How is embryogenesis of the pituitary developed?
Pituitary glands Control reproductive endocrinology
They are formed from 1. Infundibulum and 2. Rathke’s Pouch
When these tissues come together by the infundibulum extending down from brain, and rathkes pouch meets. They come together and connect, the infundibulum becomes posterior pituitary (extension from brain floor - requires neural communication with hypothalamus) and Rathke’s Puch becomes anterior pituitary (extension from mouth of embryo - requires blood supply to communicate to hypothalamus)
sphnoid bond developing at base
What is the relationship of the hypothalamus with anterior or posterior pituitary and what hormones do they release?
Formed by different embryologic tissues - difference is reflected in what they do and how they communicate with the hypothalamus.
Anterior Pituitary connects with hypothalamus by blood supply - GNrH is released by hypothalamus travels by blood supply to Anterior Pituitary where it will release LH and FSH.
The posterior Pituitary has relationship with hypothalamus by paraventricular nucleus, (neural communication) but produces oxytocin by blood supply1
What are the main embryological events in development of the reproductive system in the first trimester?
Fertilisation occurs, can embryo develops
1. Migration of primordial germ cells from yolk sac to the mesentery via amoeboid movement to the gonadal ridge (next to the mesonephros.
2. Sex cords develop in gonad, paramesonephric ducts develop
3. Sex evident from structures
4. Development of male ducts and testes OR female ducts and ovaries
How are primitive sex cords formed?
- Primordial germ cells are found in the egg yolk, they then migrate to hind gut and eventually to the gonadal ridge where the mesonphros is located close by.
- The primitive cells in the Gonadal ridge stimulate cells to
Proliferate, forming compact strands of tissue called primitive sex cords. - The enlargement of these tissues cause the gonadal ridges to push a towards the mesonephros (embryonic kidney)
- Close relationship between gonad and mesonephros, at same time, a duct called paramesonephric and mesonephros duct will develop.
- Metanephros (adult kidneys) move cranially, and true future ureter forms.
How is the sex of the embryo developed?
Sexual differentiation is controlled by a single substance direct by a gene on the male Y chromosome - SRY gene make the SRY protein
When SRY is synthesized by the sex cords within primitive gonad a male reproductive system develops (formation of testis) hormones MIS (anti-mullerian hormone - makes the paramesonephric duct degrenterate), testosterone, Insl3 (insulin-like growth factor 3)
if SRY is absent, results in a female, ovary develops - no male hormones.
How are the male ducts and testes developed?
SRY gene has been detected, proteins have been produced and male hormones.
- Presence of primordial germ cells in sex cords - turn into seminiferous tubules. The rete tubules connect seminiferous tubules to the epididymis
- mesonephric duct will be epididymis - vas deferens
- paramesonephric duct is degenerating - completely gone
How do testes decent?
Step 1. Occurs in the 3rd trimester the fetus, testes is held in body cavity in peritoneal layer, and body cavity . The gubernaculum (attachment ligament) fuses to the distal pole of the tests, at the base of the body wall is an inguinal ring. Binds the peritoneum to the gubernaculum - which allows for vaginal process to form as the gubernaculum grows.
The gubernaculum penetrates the inguinal ring due to the viseral growth / internal growth of the animal, this growth of the gubernaculum pulls down the testes into the scrotal sac.
Descendes into scrotal sac, layer of peritoneal tissue called visceral vaginal tunic, vaginal canal and parietal vaginal tunic.
What are s0me abdomailites due to teses decent?
- Cryptorchidism - failure of teses to descend into scrotum. Body temperature = neoplasia/cancer
- crypt - hidden; orchid -testis = inflammation of the tesis
- Bilateral cryptorchidism - sterility due to temperaute
- inguinal hernia 0 if inguinal ring doesn’t close up
How does the female reproductive tract form? Need to get better understanding.
gondal ridge
germ cells in sex cords, but no SRY gene/protein and no anti mullerian hormone.
- differentiation of paramesonephric duct
- distinct infundibulum (ovary duct)
- thinning of ovary duct
- inside gonad, break down of mesonephric duct and break down of sex cords
- regression of epithelial cords
- ovarian medulla
- cortex for primordial follicles
- thicken duct of paramesonephric duct
- Reproductive tract continues to develop, the mullerian ducts come together, paramesonpheric duct making its way down to rectum/opening of vagina and bladder. The vagina region is making its way up from the outside of the animal to the migrating reproductive tract. Two tissues coming together - one is ectoderm and mesoderm. join and bud forming the full reproductive tract
- fusion of paramesonephric ducts (two uterine horns form - future cervix, and uterine body) and bud from urogenital sinus
- more differentiation - final shape of uterus, production of cervix (cartilaginous rings), development of vagina and bladder
What gives raise to the final arrangement of the reproductive tract in marsupial, monotremes and eutherian mammals?
the uterus and vagina result from fusion of the paramesonephric ducts - the degree of fusion will give raise to the final arrangement
- marsupial = Because of the way the ureters migrate, or develop (they develop on the inside of the paramesonephric ducts) as a consequence they’re passing through the closure of the two ducts = therefore two vaginas
- monotreme = the 2 paramesonephric ducts never come together, empty into urogenital sinus.
- Eutherian mammals = ureters pass to the outside which allows fusion of the paramesonephric ducts
What hormone is responsible for differentiating External genitalia, female and male?
embryonic tissue that gives raise to the vulva, clitoris, and penis - same tissue
Dihydrotestosterone produce male genitalia, not present = female vulva clit
