Embryonic Development of the Reproductive System Flashcards
Know the different factors/stages in sexual differentiation
-Genetic,
-gonadal,
-internal genitalia,
-external genitalia,
-hypothalamic,
-secondary sex traits,
-psychological,
-behavioral
Know the genetic sex for mammals including the terms heterogametic and
Homogametic
-Males- XY, heterogametic
-Females- XX, homogametic
Know what the SRY gene is and what it does
-SRY gene is the gene that is responsible for male sexual development
-SRY gene is responsible for the production of Testes determining factor (TDF) or SRY protein
-SRY protein causes indifferent gonads to be organized as the testes
Know the steps in the development of the male reproductive tracts including the hormones/factors involved and how the structures evolve (develop/regress)
1) Undifferentiated sex cords begin to align with small rete tubules. Mesonephric tubules haven’t connected with rete tubules. Undifferentiated gonads are covered by tunica albuginea. Paramesonephric duct is present but has no purpose
2) Rete and mesonephric tubules interconnect. Undifferentiated sex cords developing into epithelial cords (epithelial cords will become seminiferous tubules). Paramesonephric duct regressing (due to AMH from Sertoli cells of developing testes)
3) Seminiferous tubules are formed. Rete testis and efferent ducts are fused. Mesonephric duct is becoming epididymis. Paramesonephric duct has regressed
Know the steps in the development of the female reproductive tracts including the hormones/factors involved and how the structures evolve (develop/regress)
- Both ducts are intact. Remnants of mesonephric tubules don’t fuse with rete tubules
- Rete testis are gone. Paramesonephric duct continues to develop and enlarge. Sex cords regress while PGCs don’t
- Primordial follicles begin to develop. Paramesonephric ducts develop while mesonephric ducts regress
- Clusters of follicles surrounded by a layer of tissue develop at the periphery of the ovary. Sex cords are gone. Ovary now has a distinct cortex and medulla. Mesonephric tubules have regressed completely
Know what the bipotential gonad is and how germ cells get to it
-Bipotential gonad: Undifferentiated gonad that can develop into either testis or ovaries and forms from the genital ridge
-Germ cells wander from the primary ectoderm, into the yolk sack wall, and collect near the base of the allantois and hindgut
-Germ cells move to the genital ridge by ameboid movement (aided by telopheron which is a chemotactic agent)
Know characteristics of primordial germ cells
-PGCs are larger than somatic cells
-Have large, round nuclei with prominent nucleoli
-Exhibit pseudopodia
-Secrete lytic enzymes
Know which sex is the phenotypic “default” and why.
-Female as the SRY gene must be present to produce SRY protein
-SRY protein is required for the testes to develop
Know how and when testicular descent occurs and why this process is important
-Transabdominal phase
-Inguinal-scrotal phase
-Testicular descent is important for sperm survival as body temperature is too high for them
Transabdominal phase
-Testis are retroperitoneal and caudally attached to the gubernaculum.
-Peritoneum and gubernaculum cells fuse to form a junction that allows the vaginal process to form
Inguinal-scrotal phase
-The gubernaculum rapidly grows when it reaches the inguinal ring.
-The force of this growth moves the testes into the inguinal canal.
-The gubernaculum shrinks and allows the testes to move through the inguinal opening. –As the gubernaculum shrinks, the testes move further into the scrotum.
-When the testes are fully descended, the gubernaculum shrinks
Know when testicular descent occurs in the bull and ram
halfway through gestation
Know when testicular descent occurs in the boar
last quarter of gestation
Know when testicular descent occurs in the stallion
right before or right after birth
Know when testicular descent occurs in the human
seven months of gestation
