reproductive systems Flashcards
function of the reproductive system
Not essential to the life of the individual - ensures species survival Produce haploid gametes (gametogenesis)
Store, nourish and transport haploid gametes for fertilisation
how is sex determined
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
female reproductive organs
internal:
Shares the pelvic cavity with the bladder and rectum
Covered superiorly by peritoneum
follicle development-stage 1
Primordial follicles
Primary oocyte, enclosed by a single layer flattened follicular/granulosa cells and basal lamina
At puberty primordial follicles are stimulated
follicle development-stage 2
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
follicle development-stage 3
Secondary Follicle
Spaces develop containing follicular fluid = coalesce to form a cavity
Production of oestrogen by granulosa cells
follicle development-stage 4
Graafian (tertiary) follicle
Antrum-Large fluid filled cavity
Surrounded by corona radiata = ‘glowing crown’; nutrition
ovulation
Proteolytic
activity stimulated by gonadotropin (LH)
Oocyte expelled into entrance of the uterine tube
cell types produced:
Corpus Luteum and corpus Albicans
Corpus Luteum = ‘yellow body’
Endocrine function follicular cells release
progesterone and oestrogen
Corpus Albicans = ‘white body’
Cells replaced by collagen ‘scar’
uterine tube structure
fimbiae-‘fringe’
infundibulum-‘funnel’
ampulla
ovaries
isthmus
intramural
ampulla=wide, convoluted,
muscular tube for peristalsis, site of fertilisation
epithelium of uterine tube
2 types of cells: secretory(peg)-watery secretion for gamete nourishment
Ciliated-cilia beat rate increases in response to oestrogen
uterus structure and uterine wall structure:
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)
external anatomy(vulva)
glans clitoris
vestibule(region)
mons pubis
labia majora
labia minora
vaginal opening
ovaries as the primary female reproductive organ-oestrogen+progesterone
*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
menstrual cycle: follicular development
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
female sexual development
●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)
menstrual cycle-follicular phase, luteal phase
- 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)
hormones during follicular phase
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)
luteal surge+ovulation
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
hormones during luteal phase:
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
endometrium development phases: menstrual phase(first 4 days)
- 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
endometrium development phases: Proliferative phase
- Oestrogen secreted by developing follicle leads to growth and thickening of the endometrium
- Uterine glands develop in endometrium but do not produce anything yet
endometrium development phases: Secretory (progestational) phase
- 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
endometrium development phases: New menstrual phase
- 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)
