Reproduction in humans Flashcards
What are the 3 parts of the structure of the reproductive system?
- gonads (testes and ovaries)
- internal genitalia
- external genitalia
What are the 3 levels where sex is defined?
Genetic sex > gonadal sex > phenotypic sex
How does genetic sex determines gonad sex?
Sex-determining region of the Y (SRY gene) encodes testes-determining factor (TDF) in bi-potential gonads > produce SOX9 > differentiation of primitive gonads into testes
What is the role of SOX9?
directly regulates the expression of many target genes in Sertoli cells that have important functions during sex determination and differentiation
What does RSPO1 do?
Drives ovary development
What determines the phenotypic sex?
The testes
What are the disorders of chromosomal sex?
- Turner’s syndrome: female only have one sex chromosome
- 45,X/46,XY mosaicism (some cells have XX, some XY)
- Triple X female
- Klinefelter syndrome: at least one extra X chromosome in males
- XYY, Jacobs syndrome
What are the disorders of phenotypic sex due to endocrine disorders?
- Defect in androgen or its receptor
- testes fail to secrete androgens
- tesicular feminisation syndrome: defect in androgen receptor gene - Genetic deficiency in 5 alpha-reductase > failure in development of male genitalia
- Adrenal androgen hyper secretion (congenital adrenal hyperplasia) > genital ambiguity in female infant
What are the male accessory sex glands?
seminal vesicles, prostate gland and bulbourethral glands
What is the function of seminal vesicles?
- Provide bulk of the semen
- Supply fructose to nourish sperm
- Secrete prostaglandins > stimulate contraction smooth muscles of the ‘tract’ to facilitate sperm transport
- Secrete fibrinogen to clot the semen
What is the function of the prostate gland?
- Secrete alkaline fluid to neutralize acidic vaginal secretion
- Provide clotting enzymes to ‘clot’ semen and fibrinolysis to degrade the ‘clot’
What is the function of the bulbourethral glands?
Secrete mucus for lubrication
What is the testes made up of?
- Seminiferous tubules
- contains germinal cells and Sertoli cells
- site of spermatogenesis - Interstitial cells (Leydig cells): secrete testosterone
What are the functions of the Sertoli cells?
- form tight junctions to provide testes-blood barrier > only selected substances can pass through
- produce chemicals and proteins to nourish spermatogenic cells
- establish stem cell niche to ensure renewal of sperm cell precursors
- produce androgen-binding protein (ABP) > binds to testosterone to increase concentration (x100) in tubules > can bind to androgen receptor
- secrete inhibin > inhibits FSH release
- secrete anti-mullerian hormone (AMH)
What is semen made of?
- 10% sperm and testicular fluid
- 30% prostate secretions
- 60% seminal vesicle secretions
What are the functions of androgens (1)?
- Sexual differentiation
- induce development of male reproductive tract and external genitalia
- promote descending of testes into scrotum - Spermatogenesis
- Growth and maturation of the reproductive system; maintain function of male reproductive tract
What are the functions of androgens (2)?
- Development of secondary sexual characteristics
- Male-pattern behaviour
- Non-reproductive function
- signal protein anabolism and muscle development
- stimulate bone growth and closure of epiphyseal plate
What are anabolic steroids?
- Synthetic steroids similar to testosterone in function
- Target androgen receptor
- Used for hormone replacement therapy
- Abused for performance enhancement
What are the negative effects of anabolic steroids?
Short term effects:
- males: premature baldness; testicular degeneration; impotence
- females: menstrual irregularities; irreversible masculinising
Long term effects: cardiovascular diseas; increased risk of liver cancer
What are prostaglandins?
- Chemical messengers produced in virtually all tissues
- 20-carbon fatty acid derivatives from arachidonic acid
- Act locally and inactivated rapidly after action
What are the functions of prostaglandins?
- stimulate reproductive tract contraction
- facilitates sperm transport
- associated with painful menstruation
- involved in uterine contrast during labour
- important for ovulation
What happens when there is a duplication of RSPO1 gene in XY individual?
Individual had male-to-female sex reversal
What is the structure of the ovaries?
contains millions of primordial follicles with ovum arrested in meiosis I at birth
consist of cortex and medulla:
- cortex contains ovarian follicles
- medulla contains major blood vessels and nerves
What are ovarian follicles?
consists of oocytes, surrounding follicular cells and stroma
follicular cells include granulose and thecal cells:
- work together to produce estrogen
- granulose cells produce zone pellucida to cover oocyte
- thecal cells are specialised connective tissue cells
What are the two cyclic changes during menstrual cycle?
ovarian cycle and uterine cycle
what happens during the ovarian cycle?
follicular phase:
- maturation of the oocyte and proliferation of granulose and thecal cells
ovulation:
- enlarged Graafian follicle bulge on surface of ovary and release mature oocyte
luteal phase:
- follicular cells converted into steroidogenic cells > form corpus luteum
- secretion of large quantity of progesterone and moderate amount of estrogen to prepare uterus for embryo implantation
What is the structure of the uterus?
endometrium: made up of stratified epithelium, stroma and glands
myometrium: smooth muscle
perimetrium: connective tissue covered by simple squamous epithelium
What are the 3 phases of the uterine cycle?
proliferative phase: estrogen stimulates growth of epithelial cells, glands and blood vessels
secretory phase: progesterone converts thickened endometrium to highly vascularised, glycogen-filled tissue
menstrual phase: sloughing of endometrium due to demise of corpus luteum
What are the 5 placenta hormones?
human chorionic gonadotropin (hCG)
estrogen
progesterone
placental lactogen
CRH
function of estrogen
stimulates endometrial growth and enlargement of uterus
inhibit prolactin secretion
stimulates growth of mammary ducts
bone and cardiovascular health
function of progesterone
inhibits estrogen induced endometrial growth
suppresses uterine contractions
stimulates decidualization and gland secretion
promote formation od mucus plug in cervix
stimulates development of mammary alveoli
function of placental lactogen
maternal growth hormone of pregnancy
metabolic effect in mother: lipolysis, decrease of glucose utilisation
prepare mammary gland for lactation
