Reproduction in humans

Question 1

What are the 3 parts of the structure of the reproductive system?

Answer 1

• gonads (testes and ovaries)
• internal genitalia
• external genitalia

Question 2

What are the 3 levels where sex is defined?

Answer 2

Genetic sex > gonadal sex > phenotypic sex

Question 3

How does genetic sex determines gonad sex?

Answer 3

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

Question 4

What is the role of SOX9?

Answer 4

directly regulates the expression of many target genes in Sertoli cells that have important functions during sex determination and differentiation

Question 5

What does RSPO1 do?

Answer 5

Drives ovary development

Question 6

What determines the phenotypic sex?

Answer 6

The testes

Question 7

What are the disorders of chromosomal sex?

Answer 7

• 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

Question 8

What are the disorders of phenotypic sex due to endocrine disorders?

Answer 8

1. Defect in androgen or its receptor
   - testes fail to secrete androgens
   - tesicular feminisation syndrome: defect in androgen receptor gene
2. Genetic deficiency in 5 alpha-reductase > failure in development of male genitalia
3. Adrenal androgen hyper secretion (congenital adrenal hyperplasia) > genital ambiguity in female infant

Question 9

What are the male accessory sex glands?

Answer 9

seminal vesicles, prostate gland and bulbourethral glands

Question 10

What is the function of seminal vesicles?

Answer 10

• 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

Question 11

What is the function of the prostate gland?

Answer 11

• Secrete alkaline fluid to neutralize acidic vaginal secretion
• Provide clotting enzymes to ‘clot’ semen and fibrinolysis to degrade the ‘clot’

Question 12

What is the function of the bulbourethral glands?

Answer 12

Secrete mucus for lubrication

Question 13

What is the testes made up of?

Answer 13

1. Seminiferous tubules
   - contains germinal cells and Sertoli cells
   - site of spermatogenesis
2. Interstitial cells (Leydig cells): secrete testosterone

Question 14

What are the functions of the Sertoli cells?

Answer 14

• 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)

Question 15

What is semen made of?

Answer 15

• 10% sperm and testicular fluid
• 30% prostate secretions
• 60% seminal vesicle secretions

Question 16

What are the functions of androgens (1)?

Answer 16

1. Sexual differentiation
   - induce development of male reproductive tract and external genitalia
   - promote descending of testes into scrotum
2. Spermatogenesis
3. Growth and maturation of the reproductive system; maintain function of male reproductive tract

Question 17

What are the functions of androgens (2)?

Answer 17

1. Development of secondary sexual characteristics
2. Male-pattern behaviour
3. Non-reproductive function
   - signal protein anabolism and muscle development
   - stimulate bone growth and closure of epiphyseal plate

Question 18

What are anabolic steroids?

Answer 18

• Synthetic steroids similar to testosterone in function
• Target androgen receptor
• Used for hormone replacement therapy
• Abused for performance enhancement

Question 19

What are the negative effects of anabolic steroids?

Answer 19

Short term effects:
- males: premature baldness; testicular degeneration; impotence
- females: menstrual irregularities; irreversible masculinising

Long term effects: cardiovascular diseas; increased risk of liver cancer

Question 20

What are prostaglandins?

Answer 20

• Chemical messengers produced in virtually all tissues
• 20-carbon fatty acid derivatives from arachidonic acid
• Act locally and inactivated rapidly after action

Question 21

What are the functions of prostaglandins?

Answer 21

• stimulate reproductive tract contraction
• facilitates sperm transport
• associated with painful menstruation
• involved in uterine contrast during labour
• important for ovulation

Question 22

What happens when there is a duplication of RSPO1 gene in XY individual?

Answer 22

Individual had male-to-female sex reversal

Question 23

What is the structure of the ovaries?

Answer 23

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

Question 24

What are ovarian follicles?

Answer 24

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

Question 25

What are the two cyclic changes during menstrual cycle?

Answer 25

ovarian cycle and uterine cycle

Question 26

what happens during the ovarian cycle?

Answer 26

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

Question 27

What is the structure of the uterus?

Answer 27

endometrium: made up of stratified epithelium, stroma and glands

myometrium: smooth muscle

perimetrium: connective tissue covered by simple squamous epithelium

Question 28

What are the 3 phases of the uterine cycle?

Answer 28

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

Question 29

What are the 5 placenta hormones?

Answer 29

human chorionic gonadotropin (hCG)

estrogen

progesterone

placental lactogen

CRH

Question 30

function of estrogen

Answer 30

stimulates endometrial growth and enlargement of uterus

inhibit prolactin secretion

stimulates growth of mammary ducts

bone and cardiovascular health

Question 31

function of progesterone

Answer 31

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

Question 32

function of placental lactogen

Answer 32

maternal growth hormone of pregnancy

metabolic effect in mother: lipolysis, decrease of glucose utilisation

prepare mammary gland for lactation