reproductive systems

Question 1

function of the reproductive system

Answer 1

Not essential to the life of the individual - ensures species survival Produce haploid gametes (gametogenesis)
Store, nourish and transport haploid gametes for fertilisation

Question 2

how is sex determined

Answer 2

Gonadal sex is determined by the sex chromosomes in mammals and birds, XY/ZZ for testes and XX/ZW for ovaries.
Androgen release in utero causes masculinisation of genitalia in mammals.
Oestrogen release in ovo causes feminisation of genitalia in birds
Other animals- not genetically determined (16-28°=testes and >32°=ovaries)
Intersex

Question 3

female reproductive organs

Answer 3

internal:
Shares the pelvic cavity with the bladder and rectum
Covered superiorly by peritoneum

Question 4

follicle development-stage 1

Answer 4

Primordial follicles
Primary oocyte, enclosed by a single layer flattened follicular/granulosa cells and basal lamina
At puberty primordial follicles are stimulated

Question 5

follicle development-stage 2

Answer 5

Primary follicle (uni- layered)
Oocyte enlarges and follicular/granulosa cells increase in size = cuboidal
Oocyte produces zona pellucida
- Glycoproteins
- Important in binding of spermatozoa

Primary follicle (multi-layered)
Follicular/granulosa cells increase in number; increase in thickness – stratified
Zona pellucida assembled

Question 6

follicle development-stage 3

Answer 6

Secondary Follicle
Spaces develop containing follicular fluid = coalesce to form a cavity
Production of oestrogen by granulosa cells

Question 7

follicle development-stage 4

Answer 7

Graafian (tertiary) follicle
Antrum-Large fluid filled cavity
Surrounded by corona radiata = ‘glowing crown’; nutrition

Question 8

ovulation

Answer 8

Proteolytic
activity stimulated by gonadotropin (LH)
Oocyte expelled into entrance of the uterine tube

Question 9

cell types produced:
Corpus Luteum and corpus Albicans

Answer 9

Corpus Luteum = ‘yellow body’
Endocrine function follicular cells release
progesterone and oestrogen

Corpus Albicans = ‘white body’
Cells replaced by collagen ‘scar’

Question 10

uterine tube structure

Answer 10

fimbiae-‘fringe’
infundibulum-‘funnel’
ampulla
ovaries
isthmus
intramural

ampulla=wide, convoluted,
muscular tube for peristalsis, site of fertilisation

Question 11

epithelium of uterine tube

Answer 11

2 types of cells: secretory(peg)-watery secretion for gamete nourishment
Ciliated-cilia beat rate increases in response to oestrogen

Question 12

uterus structure and uterine wall structure:

Answer 12

uterus:
fundus=top
body
cervix
(uterine tube+ovaries)

uterine wall:
para/perimetrium=visceral peritoneum

myometrium=interwoven smooth muscle/CT.
hormonal responce=hypertrophy/hyperplasia (childbirth)

endometrium=epithelial layer (menstrual cycle, zygote embeds itself)

Question 13

external anatomy(vulva)

Answer 13

glans clitoris
vestibule(region)
mons pubis
labia majora
labia minora
vaginal opening

Question 14

ovaries as the primary female reproductive organ-oestrogen+progesterone

Answer 14

*Produce ova (oogenesis)
*Secrete female sex hormones
Oestrogen
*Essential for ova maturation and release
*Establishment of female secondary sexual characteristics
*Essential for transport of sperm from vagina to fertilisation site(uterus)
*Contribute to breast development in anticipation of lactation
progesterone
*Regulates the development of the endometrium
*Important in preparing suitable environment for nourishing a developing embryo/foetus
*Contributes to breasts’ ability to produce milk

Question 15

menstrual cycle: follicular development

Answer 15

At birth, primordial follicles are present in the ovary (1-2 million)
*Unlike males, mitosis complete by the end of the first trimester
*Every day, small numbers begin to develop and grow, but most die (atresia). At puberty – approx. 200,000 remain
*To grow through to ovulation a follicle must receive correct levels of LH and FSH

follicle=protective layer around egg, egg breaks out in ovulation

Question 16

female sexual development

Answer 16

●Just prior to puberty GnRH pulse generation begins
●Luteinizing Hormone (LH) and Follicle Stimulating hormone (FSH) are released from the anterior pituitary
●This ‘awakens’ the ovary – start of follicular development
●Developing follicles release oestrogens
●Development of female secondary characteristics (eg fat deposition, growth of reproductive tract)
●Growth of auxillary hair, libido and pubertal growth spurt due to the rise in adrenal androgens
●When sufficient GnRH, LH and FSH are present = First period occurs (menarche)

Question 17

menstrual cycle-follicular phase, luteal phase

Answer 17

• Average cycle lasts 28 days in humans
• Normally interrupted only by pregnancy
• Finally terminated by menopause
• Consists of two alternating phases:

Follicular phase
*First half of the 28-day cycle
*Dominated by presence of maturing follicles
*Follicle produces oestrogens

Luteal phase
*Second half of the 28-day cycle
*Characterised by presence of corpus luteum
*Corpus luteum produces progesterone (& oestrogen)

Question 18

hormones during follicular phase

Answer 18

FSH and LH rise at the beginning of the cycle due to GnRH release

*Rising FSH and LH stimulate oestrogen release from the developing follicle

Rising oestrogen levels inhibit FSH, but not LH secretion
*Inhibin also inhibits FSH
*Oestrogen stimulates positive feedback on the follicle causing further oestrogen release; oestrogen levels significantly rise (autocrine signalling)

Question 19

luteal surge+ovulation

Answer 19

LH surge : High oestrogen levels stimulate the anterior pituitary to produce large amounts of LH
*Positive feedback
*Ovulation occurs due to LH surge

OVULATION: Released oocyte enters oviduct where it may or may not be fertilised
Corpus luteum produces progesterone

Question 20

hormones during luteal phase:

Answer 20

Ruptured follicle forms the corpus luteum

*Corpus luteum produces large amounts of progesterone (and oestrogen)

*Progesterone (and oestrogen) inhibit LH and FSH release from the anterior pituitary

After approximately 10 days the corpus luteum degenerates
*Progesterone and oestrogen levels significantly drop as corpus luteum degenerated
*FSH (and LH) rise as no longer inhibited by progesterone (and oestrogen)

Ruptured follicle forms the corpus luteum
-> releases large amounts of Progesterone & Oestrogen
Corpus luteum functions:
* Oestrogens responsible for endometrium thickening
* Progesterone responsible for endometrium development and maintenance
* Progesterone inhibits LH and FSH secretion

Question 21

endometrium development phases: menstrual phase(first 4 days)

Answer 21

• Endometrium lining of the uterus is disintegrating
• Bleeding occurs from ruptured blood vessels in endometrium
• Blood and disintegrating outer layers of endometrium expelled as menstrual fluid

Question 22

endometrium development phases: Proliferative phase

Answer 22

• Oestrogen secreted by developing follicle leads to growth and thickening of the endometrium
• Uterine glands develop in endometrium but do not produce anything yet

Question 23

endometrium development phases: Secretory (progestational) phase

Answer 23

• Corpus luteum formed (from day 14) secretes progesterone and oestradiol
• Progesterone stimulates the uterine glands to secrete “uterine milk”, which is high in protein and glycogen
• Provides correct environment should ovum fertilisation occur

Question 24

endometrium development phases: New menstrual phase

Answer 24

• If fertilisation does not occur, CL regresses and progesterone and oestrogen not produced
• Endometrium cannot be maintained and necrosis occurs
• Expelled with blood as menstrual fluid
• Menstruation usually lasts 3-5 days (20-200ml blood lost)

Question 25

fertilisation

Answer 25

*Sperm deposited in vagina travel through cervical canal, uterus and up to the upper third of the oviduct.
*Site of fertilisation: OVIDUCT (upper third)
*Must occur within 24-36 hours of ovulation
*Sperm usually survive about 48 hours but can survive up to 7 days in female reproductive tract

Question 26

implantation

Answer 26

• Fertilised ovum begins to divide and reaches uterus in 3-4 days
• Gives time for the endometrium to develop into a suitable state for implantation of developing blastocyst
• By day 9, the blastocyst/developing placenta produces human chorionic gonadotrophin (hCG) at high l

Question 27

egg development

Answer 27

Corpus Luteum continues to produce progesterone and oestrogen for 8 weeks before its function declines (due to decreased hCG levels)
This maintains the endometrium and survival of blastocyst until the placenta is developed
Placenta takes over production of oestrogen and progesterone

Question 28

partuition(childbirth)

Answer 28

1)High oestrogen:progesterone ratio that occurs towards the end of pregnancy upregulates oxytocin receptors in myometrium so circulating oxytocin can bind
2) Oxytocin stimulates muscle contraction
-2) Pressure of foetus against the cervix stimulates oxytocin secretion and causes contractions
->Contractions leads to more oxytocin production
->Positive-feedback cycle progressively increases until cervical dilation and delivery are complete

Question 29

lactation

Answer 29

During gestation
* Elevated placental oestrogen and progesterone promote development of ducts and alveoli in mammary glands
Prolactin
* Stimulates synthesis of enzymes essential for milk production by alveolar epithelial cells
* Withdrawal of placental steroids at birth initiates lactation
Sustained by suckling
* Triggers release of oxytocin and prolactin
* Oxytocin causes milk ejection
* Prolactin stimulates synthesis of more milk to replace milk ejected