reproductive physiology

Question 1

identify the parts of the male reproductive tract *

Answer 1

teh ductal system goes from the testes and connects to the same tract as urine

both the urine and seminal fluid/ejaculate come out of the urethra

Question 2

describe the endocrine regulation of the male reproductive tract *

Answer 2

GnRH is released from the hypothalamus - pulsitile

it acts on the anterior pituitory - ant pit produces LH and FSH which work together to cause the production of testosterone from the testes

LH acts on the leidig cells only - the leidig cells make testosterone

testosterone enters the seminiferous tubule and helps with the production of sperm (testosterone has other effects too)

FSH acts on the sertoli cell in the seminiferous tubule - they produce antigen binding protein (ABP)

ABP binds testosterone and regulates the function of sertoli cells and enhances the production of sperm

sertoli cells release inhibin which inhibits LH and FSH release

testosterone also has -ve feedback effect on LH/FSH

Question 3

describe spermatogenesis *

Answer 3

happens in the seminiferous tubule

germ cell becomes sperm cell through mitosis to keep up the numbers, and meiosis to form haploid cells

• diploid spermatogonium (germ cells) are near the basement membrane
• undergo mitotic division = primary spermatocyte
• 1st meiotic divison = secondary spermatocytes (haploid)
• 2nd meiotic division
• spermatids
• spermatazoa
• released into the lumen of the seminiferous tubule
• journey along the epididymis, vas deferens and urethra

Question 4

summarise the male reproductive function *

Answer 4

starts at puberty

functions continually

continues throughout life normally

sperm quality and quantity decrease with age

LH stimulates testosterone

FSH and testosterone sustain sertoli cell function

sertoli cells support spermatogenesis

Question 5

problem with the rate of production of sperm *

Answer 5

it is a very rapid process

likely to be a lot of msitakes

only 4% sperm are ‘normal’ this is enough because so many are produced

Question 6

summarise the female reproductive function *

Answer 6

starts at puberty

functions cyclically - 28-30 days

normally operates until 45yrs - varies

egg quality decreases with age - more likely to have abnormalities eg chromosomal abnormalities

FSH stimlates (some) development of ovarian follicles and 17B-oestadiol synthesis

LH stimulates progesterone production

these steroids regulate uterine endometrium

Question 7

summarise the hyopothalamo-pituitary-gonodal axis for females *

Answer 7

LHRH (also called GnRH) released from hypothalamus

acts on ant pit = production of LH and FSH

LH and FSH act in ovaries

ovaries produce progesterone and oestrogen that act in the uterus

prog and oest provide -ve feedback on hyp and pit

Question 8

what are the 3 phases of the ovarian cycle and the hypothalamus-pituitary axis in them *

Answer 8

follicular - oestrogen provides -ve feedback - shuts down the reproductive axis

midcycle - oestrogen upregulates production of GnRH and LH FSH because the hyp and pit’s sensitivity to oestrogen has changed = further production of oestrogen - it is a feedforward loop

luteal phase - after ovulation progesterone is the main hormone - this provides -ve feedback

Question 9

describe the levels of hormones through the ovarian cycle *

Answer 9

peak of oestrogen just before midcycle, blip of progesterone

peak of LH and FSH at midcycle - accelarates the growth of the main follicle and release of egg

both progesterone and oestrogen high in luteal phase - progesterone is higher

combination of oestrogen and progesterone regulates the menstrual cycle and uterine function

key hormones in the release of the egg

Question 10

describe the menstrual cycle *

Answer 10

under the control of steroids

oestrogen causes early growth

in the 1st 2 weeks the follicule develops and produces oestrogen - causes thickening in 1st phase - proliferative/follicular phase

then there is ovulation making the egg

corpus luteum is left behind - this makes progesterone and oestrogen

uterine wall is thick for implantation by progesterone and oestrogen in 2nd phase - secretory/luteal phase - 7-16cm

the sharp fall of progesterone at the end of the luteal phase is what causes bleeding over 3-4days go back to 2-4cm

Question 11

describe oogenesis *

Answer 11

go from primordal germ cell to oogonium to primary oocyte in utero

then from primary oocyte to secondary producing polar bodies at puberty

this is a reason why quality decreases as women age as there is a longer gap from the start of the process makling primary oocyte to end of the process

Question 12

describe folliculogenesis *

Answer 12

primordal follicle (containing a primary oocyte), primary follicle, growing follicle, antral follicle (has antrum in it), ruptured follicle - ovulation and a secondary oocyte, corpus luteum, degenerating corpus luteum

in last stages of development before ovulation the follicle produces oestrogen

corpus luteum produces progesterone and oestrogen

Question 13

describe the time frame of folliculogenesis *

Answer 13

initiation phase - the resting oocyte is present more than 2 cycles before the egg is ovulated

basal growth - follicle becomes pre-antral, then early antral

towards end of the 2nd cycle the follicle is recruitable and then is selected for rapid growth at early 3rd cycle

Question 14

what is ovulation *

Answer 14

release of mature egg from the ovary at midpoint of the menstrual cycle - approx day 14

Question 15

what is the state of the oocyte at ovulation *

Answer 15

2n - it is in meiotic arrest at metaphase II

it then enters the fallopian tube

Question 16

describe fertilisation *

Answer 16

occurs in fallopian tube

needs to happen within 24hrs otherwise the egg degenerates after this and sperm dont last long outside the male either

sperm is deposited at cervix - mucus of cervix is normally hostile to the sperm, mucus changes midcycle allowing sperm to enter the uterus

capicitation occurs in uterus

sperm passes into fallopian tube - go to ampulla

acrosome is a package of enzymes to digest the zona pollida and make way through cells left from follicle - allows DNA to enter the egg - chromosomes decondense into the male pronucleus

Ca flux

the meiotic arrest is removed and meiosis of the female egg continues - becomes haploid (23 chromatids) - get female pronucleus and 2nd polar body

change in the ZP to stop other sperm entering - this is the cortical reaction - other sperm and cumulus cells are present but dont contribute anymore

the chromatids in both pronuclei are duplicated and align on the mitotic spindle - metaphase plate is formed

the spindle pulls the chromosomes apart

each cluster of chromosomes forms a nucleus - this is now an embryo with 2 identical daughter cells

mitotic divisions

Question 17

what is the difference between post-ovulation and post-fertilisation time frames *

Answer 17

24hrs

fertilisation has to happen within 24hrs of ovulation

Question 18

main functions of the male reproductive system

Answer 18

to make mature sperm

provide andrognes to initiate and sustain the male phenotype

Question 19

describe testes *

Answer 19

they contain seminiferous tubules which produce sperm, and leydig cells (interstitial cells) which produce testosterone and other androgens

Question 20

describe the epididymis *

Answer 20

there is one in each scrotal sac - they connect the testes top the vas deferens

sperm are released from the testes and stored here prior to ejaculation

Question 21

describe the pathway of sperm *

Answer 21

released form the testes

stored in the epididymis

at ejaculation the sperm pass through the 2 vas deferens (which are contractile) and are mixxed with fluid from seminal vesicles

the fluid then leaves the ejaculatory duct and passes into the urethra where it mxes with secretions from the prostate gland

Question 22

role of the female reproductive system *

Answer 22

produce steroids (progesterone and oestrogen) to maintain female phenotype and produce oocytes - this happens in ovaries

uterus involved in reproduction

Question 23

describe teh fallopian tube *

Answer 23

it is how the oocyte reaches the uterus

provides an appropriate env for an oocyte or conceptus

Question 24

do all follicles develop to ovulation *

Answer 24

no - atesia is common

Question 25

what are the thecal cells

Answer 25

they are part of the follicles

responsible for the production of oestrogens

Question 26

what do the granulosa-luteal cells produce *

Answer 26

oestrogens and progesterones during the 2nd half of the ovarian cycle

Question 27

how does the length of the menstrual cycle vary through life *

Answer 27

when young, shortly after menache - may be 45 days

just before menopause can get shorter/longer, may miss a couple and resume

Question 28

describe the connections between the ovarian and endometrial cycle *

Answer 28

Question 29

phases of the endometrial cycle *

Answer 29

menstrual phase - 5days

• shed blood - remaining basal endometrium is very thin

repair and proliferative phase - 9 days

• stimulation of endometrial proliferation
• increase in thickness, number and length of glands, length of arteries

secretory phase - 13days

• production of nutrients and other factors
• epi glands widen, endometrium thickens, increased coiling of spiral arteries

Question 30

when does the body temperature rise in the menstrual cycle *

Answer 30

ovulation

Question 31

describe oogenesis including the time frames of the divisions *

Answer 31

• oogonia (diploid)
• mitotic division = primary oocytes
• 1st meiotic division during formation of the secondary follicle = secondary oocyte and 1st polar body - diploid - there is a pause in this meiosis at the siplotene stage of prophase 1 until puberty
• 2nd meiotic division - stops in metaphase 2 until fertilisation

time taken to go from primordal follicle to secondary oocyte >1month

ovaries contain many follicles at various stages at any 1 time - the dominant follicle enters the later stages to form the secondary (Graafian)

ovaries usually alternate between release of a follicle

human ovaries contain 2million primordial follicles at birth, only 400 will be released at ovulation during a reproductive lifetime

Question 32

most important role of sex

Answer 32

ensure fertilisation of a mature oocyte by a mature sperm

Question 33

define sexual reproduction *

Answer 33

produces offspring that differ genetically from both parents

Question 34

define sexula intercourse *

Answer 34

required for sexual reproduction (usually), activity, pleasure and human bonding

Question 35

define biological sex *

Answer 35

identifies gender, results from the chromosomes, depends on the production of gametes

Question 36

describe the links in the brain between parenting, fertility, reward and pleasure *

Answer 36

human bonding is linked to reproduction and parenting

the nigrostriatal tract controls movement

the mesolimbic dopaminergic system is involved in pathways for reward and pleasure

activation of the pleasure pathway encourages intercourse and so the continuation of human race

Question 37

describe the brains contriol of erection *

Answer 37

via the spinal cord and efferent nervous system

(tactile stimulus of the penis can activate the affernet system [pudendal nerve] = more direct interaction between the spinal cord and the penis)

there is increased PNS activity to sm of pudendal artery = increase in NO sythase = increase in NO

NO increases cGMP = dilation of arterial sm - thsi counteracts the sympathetic mediated myogenic tone = incleased blood flow into the corpus cavernosum = compression of the dorsal vein - restricting outflow of blood

the urethra is protected from the increasing pressure by the corpus spongiosum

cGMP is inhibited by phosphodiesterase (viagra inhibits phosphodiesterase)

Question 38

describe the brains control of the cliteris *

Answer 38

same process as the penis = increased size