Fertility + Reproduction

what are the parts and roles of the female urinogenital system

• cervix - opens into uterus, holds pregnancy in place, protects fetus, secretes cervical mucus that thins in menstruation to allow entry of sperm

• ovary - produces oocytes, site of oogenesis, secretes oestrogen + progesterone, contains follicles

• fallopian tube - site of fertilisation + carries oocyte from ovaries to uterus

• uterus - where fertilised ovum gets implanted + embryo develops, has 3 linings

• vagina - birth canal, where penis penetrates

what are the 3 linings in the uterus

1. endometrium - lining sheds in menstruation + where embryo implants

2. myometrium - contracts in childbirth + forms placenta

3. perimetrium - outer protective layer

what are the parts and roles of the male urinogenital system

• epididymis - coiled tube that stores sperm/sperm maturation occurs

• penis - sex organ that penetrates vagina, made up of erectile tissue that undergoes vasodilation making penis erect

• scrotum - holds testes outside of body as opt. temp for sperm is below normal body temp (2oC)

• testes - produces sperm + testosterone

• prostate gland - secretes alkaline fluid that neutralises acidity of vagina to allow sperm motility, produces fructose for respiration

• seminal vesicle - secretes fluid that makes up most of sperm, fluid has proteins needed to nourish sperm to make it viable, fluid has lots of fructose

• urethra - where urine + sperm exit (longer in men)

• vas deferens - tube to allow sperm to exit the testes

What follicles are in ovaries?

1. primordial follicle - contains a primary oocyte

2. primary follicle - zona pellucida forms

3. secondary follicle - theca cells surround follicle

4. mature/graafian follicle - very big antrum (fluid filled space found in 2nd/graafian follicles)

5. corpus luteum - after secondary oocyte is released from secondary follicle, it collapses into this + secretes progesterone

what are other structures found in ovaries?

• antrum - fluid filled space found in 2nd/graafian follicles that nourishes the oocyte

• corona radiata - layer of granulosa cells that surrounds the zona pellucida

• zona pellucida - glycoprotein layer surrounding the oocyte that prevents polyspermy (multi sperm fertilisation)

internal structure of testes

• head - has acrosome that contains hydrolytic enzymes that digest the zona pellucida / has haploid nucleus to ensure diploid number of chromosomes is maintained

• midpiece - lots of mitochondria to provide energy needed for movement of flagellum

• flagellum - has microtubules that creates swimming action/whip-like movements

• plasma membrane - surrounds the flagellum

secondary oocyte

• zona pellucida - glycoprotein layer surrounding the oocyte that prevents polyspermy (multi sperm fertilisation)

• nucleus - 23 chromosomes

• cytoplasm - gives organelles to zygote

• cortical granules - has enzymes that get released at fertilisation + changes shape of zona pellucida to prevent polyspermy

• corona radiata - layer of granulosa cells that surrounds the zona pellucida + changes shape to prevent polyspermy

structures found in testes

• seminiferous tubules - site of spermatogenesis surrounded by a basement membrane

• sertoli cells - secrete fluid into lumen of seminiferous tubule + controls entry/exit of nutrients + hormones into tubules of testes

• germinal epithelium - contains cells at different stages of sperm development e.g spermatids/spermatozoa

what’s gametogenesis

• production of haploid gametes in the gonads (ovaries and testes)

what is oogenesis

production of female gametes from germinal cells that line the ovaries / formation of a secondary oocyte

when does oogenesis start + end

start: before birth
end: menopause

outline oogenesis

• primordial germ cells (2n) in the ovaries undergo mitosis to become oogonia in the mitotic/replication stage

• oogonia (2n) grows to becomes a primary oocyte (found in primary follicle) in the growth phase

• primary oocyte (n) undergo meiosis I but arrests at prophase I until puberty.

• in puberty, a few 1 oocytes resumes meiosis I to form secondary oocytes, whilst others forms the 1st polar body
  secondary oocytes (n), found in graafian follicle starts meiosis II but arrests at metaphase II until fertilisation

• at fertilisation, 2nd oocyte completes meiosis and a 2nd polar body is formed

• a zygote (2n) is formed that’s diploid due to fusing of nuclei pf ovum and sperm

when does spermatogenesis start + end

• starts at puberty and ends at death

outline spermatogenesis

• primordial germ cells (2n) undergo mitosis to form spermatogonium (2n) in replication stage

• spermatogonium grows to form primary spermatocytes (2n) in growth stage
  primary spermatocytes undergo meiosis I to form secondary spermatocytes (n)

• 2nd spermatocytes undergo mitosis II to form spermatids (n)

• spermatids undergo maturation and differentiation to form spermatozoa
  spermatozoa (sperm) (n)

what hormones are involved in spermatogenesis

• FSH

• GnRH

• LH

• testosterone

• inhibin

what hormones are involved in oogenesis

• FSH

• LH

• oestrogen

• progesterone

• GnRH - gonadotrophin releasing hormone

role of LH/GnRH in spermatogenesis

• 
  hypothalamus releases GnRH

• GnRH stimulates anterior pituitary gland to release LH

• LH binds to LEYDIG cells (next to seminiferous tubules that can produce/secrete hormones) and stimulates them to release testosterone

• this initiates spermatogenesis

• testosterone causes negative feedback by decreasing FSH and GnRH levels

role of FSH/testosterone in spermatogenesis

• FSH also released from anterior pituitary gland

• binds to sertoli cells + activates them causing INHIBIN to be secreted

• causes negative feedback as production of inhibin decreases FSH

• sertoli cells more receptive to testosterone which binds to sertoli cells + further initiates spermatogenesis

• testosterone inhibits LH

role of inhibin in spermatogenesis

• inhibits secretion of FSH

role of LH/GnRH in oogenesis

hypothalamus releases GnRH which stimulates anterior pituitary gland to release LH
- LH binds to follicle cells in ovaries which causes ovaries to mature and release oestrogen
- SURGE in LH causes 2nd oocyte to be released from graafian follicle
- LH stimulates development of corpus luteum

role of FSH in oogenesis

• released from anterior pituitary gland

• binds to follicle cells in ovary and stimulates maturation of follicles

• stimulates release of oestrogen

role of oestrogen in oogenesis

• increased oestrogen levels inhibits FSH

• stimualtes release of LH —> stimulates ovulation

role of progesterone in oogenesis

• released from corpus luteum

• inhibits FSH and LH

role of inhibin in oogenesis

• release stimulated by FSH

• released from granulosa cells of ovarian follicles

• inhibits FSH

what 2 cycles are in the menstrual cycle

1. ovarian - release of 2nd oocyte

2. uterine - development of endometrium

control of the menstrual cycle

• anterior pituitary gland secretes FSH into plasma

• FSH travels to ovaries and stimulates follicle maturation

• mature follicles releases oestrogen which inhibits FSH, stimulates LH production and thickens endometrium lining

• LH is released from anterior pituitary gland and SURGE in LH causes oestrogen —> release of 2nd oocyte from graafian follicle. LH also stimulates development of graafian to corpus luteum

• corpus lutuem releases progesterone which stimualtes development of blood vessels in endoemtrium + inhibits FSH/LH production

• decrease in LH means corpus luteum degenerates and doesn’t secrete as much progesterone.

• NO pregnancy, oestrogen/progesterone levels decrease so endometrium sheds and cycle repeats

what are the 4 stages of fertilisation

1. copulation

2. capacitation

3. acrosome reaction

4. cortical reaction

Outline copulation

• sexual intercourse

• release of semen into vagina which contains spermatozoa

• spermatozoa must travel from cervix —> uterus —> fallopian tube —> ovum

outline capacitation

• occurs in fallopian tube

• glycoproteins are removed from csm of sperm by proteases in hydrolysis reactions

• this makes csm more permeable to Ca2+ —> sperm more sensitive to signals from oocyte

• cholesterol levels decrease

• membrane more fluid —> increases motility of sperm —> can penetrate corona radiata easier

outline acrosome reaction

• acrosome swells and dissolves

• causes acrosome membrane to fuse with sperm csm

• hydrolytic enzymes released by exocytosis to digest corona radiata

outline the role of the antibodies in each region of the test strip

A = bind complimentary to the hCG hormone

B = bind to the hCG-bound antibodies

C = bind to any unbound antibodies

outline how pregnancy tests work

• dip dipstick into urine

• pregnant women have hormone hCH present in urine

• dipstick contains monoclonal antibodies that’s specific to hCG

• hCG moves via capillary action up the stick and binds complimentary to mAb that’s coupled with a blue latex particle in the antibody-antigen binding region

• at the test window, more hCG antibodies are present, + these bind to the hCG-antibody-latex complexes (produces a blue line)

• any unbound antibodies moves to the control window which contains anti-mouse antibodies

• these bind to the remaining unbound antibodies

what hormone does the placenta secrete in pregnant women

human chorionic gonadotrophin (hCG)

what are the different fertility treatments

• IVF - gamete intra-fallopian transfer (GIFT)

• IUI intrauterine insemination

• ICSI intracytoplasmic sperm injection

• surgical sperm retrieval (only 4 retrograde ejaculation)

• frozen embryo replacement

• donor sperm insemination

• ovulation induction

what is IVF

• female receives FSH + LH to encourage development of more follicles

• catheter used to collect follicles

• follicle added to culture mediums

• sperm collected + washed (sperm placed in culture medium + allowed to capacitate)

• sperm added to culture medium + petri dish placed into incubator to allow embryo development

RISK: multiple births, premature births, low birth rate

what is GIFT

sperm + secondary oocyte inserted directly into fallopian tube + fertilisation occurs naturally

what is IUI

• sperm are washed

• sperm inserted directly into uterus

what is ICSI

• sperm injected into secondary oocyte

• used when male has low sperm count/motility

what is SSR

• extract sperm from epididymis

what is FER

• freeze embryos from previous fertility treatments

• thaw them for later use

• don’t put in freezer due to risk of ice crystals forming

what is ovulation induction

• woman given anti-oestrogen during menstrual cycle

• more GnRH produced

• more LH and FSH

• encourage follicle development

what ethical reasons surround fertility treatments

• unused embryos are destroyed

• increased chance of offspring having medical issues

• higher risk of multiple pregnancies - affects women’s mental/physical health

• financial cost 4 parents - expensive

• genetic defects which stopped parents conceiving are passed down to kids

benefits of fertility treatments

• infertile couples can have kids

• unused embryos can be used in research

• unused embryos can provide stem cells for treatment/research

what issues can cause male infertility

• low sperm count

• abnormal sperm

• low sperm motility

• blocked vas deferens

• retrograde ejaculation

what issues can cause female infertility

• endometriosis - endometrium lining develops in wrong locations - risk of embryo implanting outside uterus

• anti-sperm antibodies - destroys sperm

• ovulatory disorders

• blocked fallopian tube