endocrinology

Question 1

3 connective tissues around testes

Answer 1

tunica vasculosa => has BVs

tunica albuginea => forms septa to separate lobules

tunica vaginalis => covers testes + epidydimis

Question 2

seminal fluid composition

Answer 2

fructose
citric acid nutrient
bicarbonate (neutralise vaginal acidity)
fibrinogen (thickener)
fibrinolytic enzymes

Question 3

testes lobules

Answer 3

each lobule = 1-4 coiled seminiferous tubules which have closed loops (meiosis of sperm)

drain into the rete testis → epidydimis for storage → vas deferens

Question 4

seminiferous tubule structure

Answer 4

surrounded by tunica propria (BM)

cells become more differentiated closer to lumen

spermatogonia (round nuclei) => primary spermatocytes => secondary => sprematids

Question 5

primary vs secondary spermocytes

Answer 5

primary:
larger nuclei - round + filled with dense chromosomes
in extended prophase of first mitotic division

secondary:
rarely seen
almost immediately undergo second meiotic division to become spermatids

Question 6

sertoli cells

Answer 6

in sn-tubules - just above spermatogonia

large, pale, irregular nuclei w/prominent nucleolous

Question 7

functions of sertoli cells

Answer 7

support development of sperm
assist sperm movement to centre
transfer nutrients from capillaries to sperm
phagocytosis of damaged sperm
hormone synthesis (AMH, ABP, inhibinB, acitivin)

Question 8

leydig cells

Answer 8

between seminiferous tubules

pale cytoplasm

hormone synthesis: cholesterol used to make testosterone/androsterone/dihydroepiandrosterone when stimulate by LH

Question 9

oocyte development through life

Answer 9

2nd trimenster: oogonia → primary oocytes → enter the 1st meiotic division (prophase)
granulosa cells surround oocyte to form primordial follicles

menarche: some primordial follicles recommence growth partly dependent on FSH → secondary oocytes released

secondary oocyte + sperm → calcium influx → stimulates 2nd meiotic division → ova (ovum) – the functional gamete

Question 10

follicle layers (in->out)

Answer 10

ovum
follicular fluid
granulosa cells
theca cells

Question 11

theca cell function

Answer 11

support folliculogenesis
hormone synthesis (LH stimulates androgen synthesis)

final cell type to die in atresia

if ovulate: hormone-dependent differentiation into luteinized thecal cells of corpus luteum

Question 12

granulosa cells

Answer 12

hormone synthesis

turn into granulosa lutein cells that produce relacin + progesterone after ovulation

Question 13

Hyperprolactinaemia

Answer 13

prolactin binds prolactin receptors on kisspeptin neurones

inhibits kisspeptin release

decreases all downstream hormones as master regulator (kisspeptin) is switched off

Question 14

side effects of hyperprolactinaemia

Answer 14

Oligomenorrhoea (in females - infrequent periods)
low libido
infertility
osteoporosis (loss of bone mineral density)

Question 15

semen formation + voyage

Answer 15

in efferent ducts of testes:
tubular fluid reabsorbed
increased conc of semen
induced by oestrogen

epidydimis:
nutrients + glycoproteins secreted into epidydimal fluid
induced by androgens

Question 16

how is oestrogen formed in males

Answer 16

testosterone => oestrogen by aromatase

Question 17

Aromatase deficiency

Answer 17

raises testosterone levels

lack of oestrogen

reduced bone mineral density + osteoporosis, taller (oestrogen needed for closure of growth plates in long bones)

Question 18

Capacitation

Answer 18

process by which sperm achieve fertilising capability
only occurs in the female reproductive tract

loss of GP coat => new surface characteristics => whiplash movements develop

Question 19

why capacitation only in female tract

Answer 19

ionic & proteolytic environment
Oestrogen and Ca2+ dependent

Question 20

Acrosome

Answer 20

sperm organelle containing enzymes and can bind to the Zona Pellucida

Question 21

acrosome reaction

Answer 21

sperm => ZP3 on ovum

Ca2+ influx into the sperm stimulated by progesterone

release of hyaluronidase (breaks down polysaccharides) & proteolytic enzymes from the acrosome

spermatozoon penetrates the Zona Pellucida

Question 22

what happens in fertilisation

Answer 22

cortical reaction triggered => ZP degradation by molecules from cortical granule

stops other sperm binding

diploid zygote forms
apoptosis + expulsion of second polar body

Question 23

Polar body

Answer 23

small haploid cell as oocyte cytoplasm does not divide evenly - undergoes apoptosis

Question 24

attachment phase of implantation

Answer 24

outer trophoblast cells contact uterine surface epithelium => involves Leukaemia inhibitory factor, Interleukin-11

Question 25

decidualisation phase of implantation

Answer 25

endometrial changes due to progesterone
glandular epithelial secretion
glycoprotein accumulation in stromal cell cytoplasm
capillary growth
increased vascular permeability

Question 26

Gonadarche

Answer 26

activation of gonads by HPG axis

Question 27

Thelarche

Answer 27

breast development

Question 28

menarche

Answer 28

development of menstrual cycles

Question 29

spermarche

Answer 29

Spermatogenesis

Question 30

Adrenarche

Answer 30

adrenal androgen production (starts ~2yrs before gonadarche)

Question 31

Pubarche

Answer 31

pubic hair

Question 32

Mini puberty (what is it, what happens in it, lack)

Answer 32

activation of the HPG axis during late pregnancy/early neonatal life

GnRH → testicle descent, penile length, Sertoli cell maturation and behaviour

lack = Cryptorchidism (failure of testicles to descend), responding to treatments, gender preferences

Question 33

Amenorrhoea

Answer 33

Absence of Periods

primary = not started after 16 years

secondary = start but then stop for at least 3-6 months e.g. pregnancy/PCOS

Question 34

Hypogonadism

Answer 34

decreased function of the gonads

decreased oestrogen in a woman/testosterone in a man

primary = issue with gonads, secondary = - decreased function of hypothalamus or pituitary gland

Question 35

what is menopause

Answer 35

Primary hypogonadism

reduced function of ovaries → reduced -ve feedback on hypothalamus and pituitary gland → high LH/FSH → decreased oestogen

Question 36

Early Menopause

Answer 36

Premature Ovarian Insufficiency (POI)
same symptoms as menopause

due to: utoimmunity, genetics (Fragile X Syndrome/Turner’s Syndrome (one X chromosome)), previous cancer therapy

Question 37

Menopause Hormone Therapy (MHT)

Answer 37

oestrogen replacement: oestrogen stimulates endometrium to proliferate

add progesterone: (if endometrium is intact) to prevent risk of Endometrial Hyperplasia/Cancer

Question 38

Andropause

Answer 38

Testosterone levels decrease slightly with age

Question 39

Free hormone hypothesis for andropause

Answer 39

majority of testosterone in blood strongly bound to SHBG (sex hormone binding globulin) - transports testosterone in blood
binds so strongly that its inactive + unavailable

albumin also binds large proportion => bioavailable

free testosterone = very small proportion - unbound + shows effect

Question 40

testosterone in prostate/scalp

Answer 40

5-alpha-reductase converts testosterone to di-hydro-testosterone (DHT)

binds androgen receptor strongly

prostate cancer: 5-alpha-reductase inhibitors would prevent increase in DHT → prevents growth of cancer

Question 41

testosterone in fat tissue

Answer 41

aromatase converts androgens into oestrogen (testosterone → oestradiol, or androstenedione → oestrone)

Breast cancer: aromatase inhibitor ensures they don’t convert their testosterone into oestrogens → prevents growth of cancer