SDR Flashcards
When does differentiation begin?
6-8wks
What does the presence of testis-determining factor cause and where is it located? (+SRY)
- Gonads develop into a testis
- Located on the Y chromosome
What does the absence of testis-determining factor cause? (-SRY)
-Gonad differentiates into an ovary
What are the different but related ducts that form beside the undifferentiated gonads?
Wolfian Ducts
Mullerian ducts
Explain what happens in the presence of SRY (+SRY)
- The Y chromosome carries the SRY gene
- Gonads differentiate into testes
- The presence of testosterone causes the wolfian ducts to develop into the internal male structures
- The presence of anti-mullerian hormone causes degeneration and atrophy of mullerian ducts
What are the internal male structures that develop?
Epididymis
Vas deferens
Seminal vesicles
Ejaculatory ducts
Explain what happens in the absence of SRY (-SRY)
- Gonads differentiate into ovaries
- The absence of testosterone causes degeneration and atrophy of the wolfian duct
- The absence of the anti-mullerian hormone allows for mullerian ducts to develop into the internal female structures
What are the internal female structures that develop?
Uterus
Fallopian tubes
Upper part of the vagina
Describe the process of puberty:
-Pulsatile release of GnRH followed by an increase in LH and FSH ->Results in episodic peaks of estradiol and testosterone-> Initiates secondary sexual maturation in girls and boys
Delayed puberty:
- No secondary sex characteristics; in females by 13 and males by 14
- Etiology: undernutrition, athletics, HPG defects, stress, environmental exposures
- 95% of the time: normal hormone levels, HPG axis intact, maturation just slow.
- Often familial
Precocious puberty:
- Sexual maturation before ages 6-7 in females and 9 in boys
- Central: GnRH-dependent-short stature d/t premature closing of the epiphysis
- Peripheral: GnRH independent- gonadal tumors, testotoxicosis, exposure to exogenous sex steroids
What are the male sex hormones (4) and what do they do?
- GnRH- released from hypothalmus, stimulates the anterior pituitary to secrete FSH and LH
- FSH- stimulates spermatogenesis (Sertoli cells)
- LH- stimulates the secretion of testosterone (Leydig cells)
- Testosterone- stimulates spermatogenesis, stimulates the development of male secondary sex characteristics
Describe hormonal regulation of the hypothalmus-pituitary-testes axis (?)
The hypothalamus releases GhRH which stimulates the anterior to release FSH and LH. LH stimulates the Leydig cells to secrete testosterone which stimulates spermatogenesis and secondary sex characteristics. FSH (and testosterone) stimulate the Sertoli cell which leads to spermatogenesis.
- *Testosterone provides negative feedback to hypothalamus= if too high will not produces more GnRH.
- *Inhibin works to inhibit FSH release from the ant. pit
Outline the Uterine Cycle (aka Menstrual Cycle)
- Menstrual phase: bleeding. Day 1 to day 3-5; function layer of the endometrial lining and blood leave the uterus through the vagina
- Proliferative phase (follicular)- Begins at end of menstruation; repair and growth of inner endometrial lining
- Secretory phase (luteal)- Due to secretion of progesterone by the corpus luteum= causes endometrial lining to thicken (forming nutritious environment awaiting the arrival of a fertilized ovum)
What hormone is the follicular phase dominated by?
Estrogen
Hypothalamus secretes GnRH->gonadotropin release by ant pit gland-> FSH and small amounts of LH stimulate growth and maturation of the ovarian follicle-> maturing ovarian follicle secretes large amounts of estrogen-> estrogen aids in maturation of follicle and builds lining -> ends with sharp rise of LH which causes ovulation.