Physiology Flashcards
What are the 2 main structures of internal reproductive organs
Mullerian ducts
most important in female
inhibited in the male by AMH
Wolffian ducts
most important in the male stimulated by testosterone
lack of stimulation by testosterone means regression in female
What is DHT role and what does it do
Testosterone inverted in the genital skin to the more potent androgen DHT (dihydrotestosterone) by 5-a-reductase.
DHT also binds to the testosterone receptor, but is more potent than testosterone.
DHT causes differentiation of the male external genitalia:
Clitoral area enlarges into penis
Labia fuse and become ruggated to form scrotum
Prostate forms
Gonadal dysgenesis
Sexual differentiation is incomplete. Usually missing SRY in male, or partial or complete deletion of second X in female. Also used as a general description of abnormal development of the gonads.
What is sex reversal
Phenotype does not match genotype, ie may be male genotypically but externally look like a female.
What is intersex
Patients prefer to be known as someone with a ‘disorder of sexual differentiation’ or DSD.
Terms such as ‘pseudohermaphrodite’ and, ‘testicular feminisation’ are now obsolete
What is androgen insensitivity syndrome
Testosterone is made but has no effect
Describe complete AIS
Complete AIS - incidence 1:20,000
Appear completely female at birth and assigned female gender despite being XY.
Have undescended testes.
Describe partial AIS
Partial AIS - incidence unknown as is probably a spectrum
Present with varying degrees of penile and scrotal development from ambiguous genitalia to large clitoris.
Surgery was universal but now fortunately considered optional or at least best delayed. Decisions made on potential. Very difficult for parents.
What is 5-a-reductase deficiency
Incidence varies enormously as autosomal recessive and can depend on inter-related marriage.
Testes form, AMH acts, testosterone acts.
Internal structures form.
External structures do not develop.
May appear mainly female or may have ambiguous genitalia
The degree of the enzyme block varies and so therefore does the presentation.
What is Turner syndrome
Turner syndrome: 1:3000
XO have failure of ovarian function.
‘Streak’ ovaries = ovarian dysgenesis - illustrates that we need 2 X’s for ovarian development.
Uterus and tubes are present but small, other defects in growth and development.
May be fertile…many have mosaicism.
Hormone support of bones and uterus
What is CAH
Completeness of the block varies.
If enzyme absent then children may be wrongly gender assigned at birth…or may have ambiguous genitalia.
Also in CAH need to be aware of possibility of ‘salt-wasting’ due to lack of aldosterone, this can be lethal.
Need treatment with glucocorticoids to correct feedback
What is the first different stage of becoming male and female in sexual differentiation
It is when the primitive sex cords express SRY to turn into either Sertoli cells in males or if they don’t express SRY they will become grandkids cells in females
What is follicle initiation
Where a cohort of early follicles leave the resting pool and grow continuously
What is called follicle recruitment
When follicles willl not continue to grow unless they reach the size at whic they respond to changes in FSH that occur in the menstrual cycle
what are the hormones of HPG axis
Hypothalamus (RH)- Gonadotrophin Releasing Hormone (GnRH), (kisspeptin)
Pituitary (SH)- Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH)
Gonad- (F) Oestradiol (E2), Progesterone (P4), (M) Testosterone, (Inhibin and activin).
what type of hormone is kisspeptin
peptide hormone
what are the gonadotrophin hormones?
LH and FSH
Describe the secretion of LH and FSH
Kisspeptin released from hypothalamus which coordinates the synthesis and secretion of GnRH. GnRH is released into primary plexus, into hypophyseal portal circulation, where it goes to anterior pituitary, binds to its receptor that is localised to gonadotroph cells to coordinate synthesis and secretion of LH and FSH.
describe the 2 therapeutic exploitation of GnRH
Synthetic GnRH- same structure as endogenous GnRH
-same GnRH but produced from cell culture
-pulsatile administration, so is stimulatory. It allows people with puberty disorders to undergo puberty and can be used to stimulate fertility.
GnRH analogues-modified GnRH peptide structure
-based on primary sequence but changed
This means they have a longer half life, results in loss of pulsatility
-single bolus, long half life, loss of pulsatiility, inhibitory
can be agonists or antagonists
what is puberty
Transition from non-reproductive to reproductive state
what is adrenarche
change/increase in adrenal androgen secretin due to cellular remodelling of adrenal cortex through early years of development.
what is pubarche
it is the result of adrenarche, result of increase in adrenal androgen secretion.
what is precocious sexual development
Development of any secondary sexual characteristic
before the age of 8 in girls
before the age of 9-10 in boys
what makes up a primordial follicle
In the foetal ovary, the surrounding cells condense around the oocyte and differentiate into the granulosa cells
The granulosa cells then secrete an acellular layer called the basal lamina
The whole structure is called the primordial follicle
what are oogonia?
Egg precursors
what factors determine growth of follicle in beginning?
The factors controlling initiation of growth and the early stages are largely unknown
FSH drives most of folliculogenesis but early growth is independent of FSH i.e. driven by local factors
Apparent in FSH-deficient patients or those with mutations of FSHr
Also means that even when FSH is suppressed eg. on COCP, the follicles will still continue early growth but then die
what happens to oocyte as follicle grows/antral development?
As the follicle grows, the oocyte is displaced to one side
how long are the stages of follicle growth
basal growth is 65 days plus follicular phase of menstrual cycle (15 days). approximately altogether 90 days
what are primordial germ cells?
cells that will become eggs or sperm
what is the difference between oogenesis meiosis and somatic meiosis
unequal division of cytoplasm during cytokinesis
What are the testes
Produce sperm and store it
Produce hormones which regulate spermatogenesis lie in scrotum outside body cavity, optimum temp for sperm production is 1.5-2.5degrees below body
Overheating of testes reduces sperm count
Well vascularised, well innervated
Normal volume of testes is 15-25ml measured by orchidometer
What is the follicular phase of menstrual cycle
It is between 5-10 days
Where follicle recruitment occurs and the correct follicle is then chosen for ovulation
What cell is in close communication with the spermatogenesis?
Sertoli cells
describe the menstrual cycle
2 phases separated by ovulation
Cycle begins on day 1=first day of bleeding
Next 14 days are follicular phase i.e. growth of follicle
Ovulation occurs at end of follicular phase
Empty follicle becomes the corpus luteum
Next 14 days are luteal phase i.e dominated by corpus luteum
Menstruation occurs at the end
describe the hormones involved in menstrual cycle
Because it’s a cycle it doesn’t matter where we start……….at the end of the cycle, the corpus luteum which as we will come to see is the left-over follicle after ovulation, is dying and the progesterone that it was making falls. This high P was exerting negative feedback at level of hyp/pit, thereby keeping levels of LH/FSH low. As the levels fall, the brake on negative feedback is lost but in such a way that it causes FSH levels to increase preferentially. This stimulates follicles to grow and as they grow they make oestradiol. The E2 feeds back to hyp-pit and inhibits FSH release, so levels fall again. In the meanwhilst LH levels have been rising a little across the follicular phase and this allows a single follicle to grow and grow and become the dominant follicle. This DF which will makes massive amounts of E2. After 2 days of E2, which reach level of >300pmol, the negative feedback becomes positive and there is a huge release of LH which cause the egg to be released. The remaining follicle becomes the CL which makes prog. & this causes negative feedback again.
At the end of luteal phase, we have progesterone exerting neg feedback on hypothalamus and pituitary. Progesterone comes from CL.
If no preganancy, CL dies.
As CL dies, progesterone levels drop (decline). This removes that negative feedback. This allows the gonadotrophins to secrete again.
It allows for a selective release of fsh. This is known as the intercycle rise in FSH.
As FSH rises, it is going to pick up early antral follicles. Those early follicles, can respond to this increase in FSH and they start growing.
As they grow, oestrogen rises/ As oestrogen rises it will start exerting negative feedback again, causing FSH to drop.
As FSH drops, those follicles will start to die, because they are losing their stimulant to survive.
All except dominant follicle. As the dominant follicle survives, it grows at an exponential rate. It grows upto 20mm in size. It produces tonnes of oestrogen.
When oestrogen levels are sustained, over 300pmol, you then get the switch to positive feedback. This positive feedback triggers ovulation and a massive release of LH. This LH will trigger ovulation and formation and luteinisation of follicle which becomes corpus leuteum.
LH-lutenising hormone.
Cl prodces progesterone, which exerts negative feedback.
Describe follicular selection
Raised FSH present a “window” of opportunity
FSH threshold hypothesis
One follicle from the group of antral follicles in ovary is just at the right stage at the right time….
This becomes the dominant follicle which goes onto ovulate
Known as “selection”
Can be in either ovary
Oestradiol levels rise reinstating negative feedback at pituitary causing FSH levels to fall prevents further follicle growth
how does the dominant follicle survive the fall in FSH
Dominant follicle can be in either ovary. It may have increase number of receptors, to doesn’t need as much FSH to respond.
what is a special property of ejaculated sperm?
Ejaculated semen is coagulated
Prostatic and seminal vesicle secretions comprise seminal fluid which coagulates - prevents loss, later liquefies.
Movement through cervical mucus removes seminal fluid, abnormally morphological sperm and cellular debris.
How does a spermpass into cervix
Sperm passes into cervix
Cervical mucus is less viscous in the absence of progesterone allowing sperm to pass.
Sperm can inhabit cervical crypts which may form a reservoir. Some evidence of thermotaxis, but mechanism not yet elucidated.
Fertilisation typically within 24-48 hours but sperm have been recovered alive after 5 days.
what is the journey of the sperm to the egg?
Passage through uterus not well understood, currents set up by uterine or tubal cilia may have a role.
Chemoattractants released from the oocyte cumulus complex may attract the sperm.
Sperm become hyperactivactivated. Forceful tail beats with increased frequency and amplitude mediated by Ca2+ influx via CatSper channels.
what is acrosome reaction
Acrosome reaction occurs in contact with the zona –cumulus complex; the acrosomal membrane on the sperm head fuses releasing enzymes that cut through the complex.
Acrosin bound to the inner acrosomal membrane digests the zona pellucida so the sperm can enter.
what is capacitation
Capacitation is partly achieved by removing the sperm from the seminal fluid, also uterine or tubal fluid may contain factors which promote capacitation.
Biochemical rearrangement of the surface glycoprotein and changes in membrane composition must occur before the acrosome reaction can occur.
describe ovulation
LH spike causes resumption of meiosis and ovulation. Converts the primary oocyte to secondary oocyte plus 1st polar body.
Basement membrane breaks so blood pours into the middle.
Oocyte cumulus complex extruded out and caught by fimbrae of uterine tube.
Theca and granulosa become mixed and the empty follicle is known as the corpus luteum. It produces progesterone in the luteal phase.
how is cl maintained in pregnancy
CL rescued in pregnancy by hCG from embryo binding to its LH receptors. CL continues to produce progesterone and maintain endometrium.
name of CL after it shrinks
corpus albicans
describe sperm penetration to the egg
- The acrosome reaction occurs in contact with the zona-cumulus complex. Sperm penetrate cumulus and bind to ZP2. Sperm enzymes cut through ZP and sperm fuses with plasma membrane3. Sperm taken in by phagocytosis. Phospholipase Zeta activated by basal Ca2+ inside egg and causes further release of intracellular Ca2+ leading to large Ca2+ spike.4. Cortical reaction as wave of Ca2+ sweeps around egg…release of proteases, peroxides and hyaline prevents polyspermy.
describe effect of testosterone andFSH on sertoli cells
Leydig cells contain LH receptors and primarily convert cholesterol into androgens. Intra-testicular testosterone levels are 100x those in plasma.
Androgens cross over to and stimulate Sertoli cell function and thereby control spermatogenesis.
Sertoli cells contain FSH receptors and converts androgens to oestrogen.
FSH establishes a quantitatively normal Sertoli cell population, whereas androgen initiates and maintains sperm production.
Leydig cells contain LH receptors and primarily convert cholesterol into androgens. Intra-testicular testosterone levels are 100x those in plasma.
Androgens cross over to and stimulate Sertoli cell function and thereby control spermatogenesis.
Sertoli cells contain FSH receptors and converts androgens to oestrogen.
FSH establishes a quantitatively normal Sertoli cell population, whereas androgen initiates and maintains sperm production.
what is a normal ejaculation volume
1.5ml-6ml
describe passage of sperm
Bulbo-Urethral Gland
Produces a clear viscous secretion high in salt, known as pre-ejaculate. This fluid helps to lubricate the urethra for spermatozoa to pass through, neutralizing traces of acidic urine.
Seminal Vesicles
Secretions comprise 50-70% of the ejaculate. Contains proteins, enzymes, fructose, mucus, vitamin C and prostaglandins. High fructose concentrations provide energy source. High pH protects against acidic environment in vagina.
Prostate
Secretes milky or white fluid roughly 30% of the seminal fluid. Protein content is less than 1% and includes proteolytic enzymes, prostatic acid phosphatase and prostate-specific antigen which are involved in liquefaction. High zinc concentration 500–1,000 times that in the blood is antibacterial.
describe what you would expect to find in semen analysis
Volume 1.5 – 6.0 ml Sperm concentration >15million/ml Liquefaction <30 minutes Motility >40% Progressive motility >32% Vitality (live) >58% Morphology (normal forms) >4% pH >7.2 Leucocytes <1 million/ml
At what age does growth of follicles accelerate
Past age of 35-38 until u have depleted all your follicles
What are the two phases of the menstrual cycle
From first day of bleeding (first day of cycle) to ovulation is the follicular phase where there is growth of follicle and dominant follicle releases oestrogen.
Ovulation occurs at end of follicular phase
Then the empty follicle collapses and transforms into corpus leuteum. This is luteal phase where corpus leuteum releases progesterone
Menstruation occurs at end of the luteal phase
What two processes slow down the movement of sperm
Liquidefication of sperm
Cervical crypts
What is capacitation
Capacitation is partly achieved by removing the sperm from the seminal fluid, also uterine or tubal fluid may contain factors which promote capacitation.
It is the biochemical rearrangement of the surface glycoproteins and changes in membrane composition that must occur before the acrosome reaction can occur
in what cells is aromatase enzyme found?
Granulosa only
what factors does menstrual cycle depend on and why are they all involved in starting menstruation?
it is an important and calorific process that requires input from lots of other systems in the body detecting fitness to reproduce.
With puberty, you have to be at a certain weight to start menstuation cycle.
-other complications involved in menstrual cycle. We can see the menstrual cycle is very much effected by the environment of the body and this is because we have to be fit to reproduce and the environment must be right.
The body needs to know the woman can cope with the burden of carrying a baby.
what processes occur before ovulation
ovulation occurs via cascade of events:
blood flow to the follicle increases dramatically
increase in vascular permeability increases intra-follicular pressure
appearance of apex or stigma on ovary wall
Local release of proteases
Enzymatic breakdown of protein of the ovary wall
12-18 hrs after peak of LH, hole appears in follicle wall and ovulation occurs
Describe the endometrial proliferative phase
Proliferative phase is stimulated by estradiol from the dominant follicle
Stromal cell division, ciliated surface. Glands expand and become tortuous, increased vascularity, neangiogenesis maximal cell division by days 12-14
When endometrium > 4mm induction of progesterone receptors and small muscular contractions of the myometrium.
describe the demise of the CL
If fertilisation does not occur, CL has an inbuilt finite lifespan of 14 days.
Regression of CL essential to initiate new cycle.
Fall in CL-derived steroids causes inter-cycle rise in FSH.
Cell death occurs, vasculature breakdown, CL shrinks. Over time it becomes a corpus albicans.
CL rescued in pregnancy by hCG from embryo binding to its LH receptors. CL continues to produce progesterone and maintain endometrium.
what subunit of hcg do pregnancy sticks identify
B subunit
describe the process of syngamy
Syngamy is the fusion of two cells or their nuclei in reproduction and this is what occurs between the sperm and egg nuclei.
- After meiosis I the oocyte is haploid and contains 23 chromosomes, but each chromosome is bound to its identical sister chromatid.
- At fertilisation the sperm binds to the ZP, penetrates it and fuses with the oocyte plasma membrane. This causes the increase in Ca2+ via PLC-zeta that then triggers the cortical reaction and also the completion of meiosis II and the expulsion of the second polar body. So the oocyte is now truly haploid.
- The sperm nuclear membrane breaks down and the chromatin decondenses and the chromosomes separate (remember sperm is also haploid)
- 4-7 hours after fusion of sperm and egg, the two sets of haploid chromosomes become surrounded by distinct membranes forming pronuclei. Each haploid pronuclei starts to synthesise/replicate its DNA in preparation for the first mitotic division
- Then the two pronuclei fuse and the chromosomes become aligned on the mitotic metaphase spindle, the chromosomes move to their appropriate positions down the equator. So that each daughter cell will receive the chromosomes with their homologous pairs (i.e. so each has full 46, diploid number, 23 from dad, 23 from mum).
- Mitosis is then complete and the one cell zygote has become a two cell embryo
When the sperm enters into the oocyte it causes the spike in Ca2+ due to PLC-zeta, this triggers the cortical reaction to prevent polyspermy and also the completion of meiosis II and expulsion of the 2nd polar body.
The haploid nucleus of the sperm transforms into the male pronucleus and the haploid female pronucleus forms. They replicate their DNA ready for mitosis.
Then the two pronuclei come together, the membranes break down and there is alignment of chromosomes down the spindle.
Each daughter cell will get 46 chromosomes. This is mitosis.
Describe the endometrial proliferative phase
Proliferative phase is stimulated by estradiol from the dominant follicle.
Stromal cell division, ciliated surface.
Glands expand and become tortuous, increased vascularity, neangiogenesis maximal cell division by days 12-14
When the endometrium >4mm induction of progesterone receptors and small muscular contractions of the myometrium
Describe the endometrial secretory phase
Secretory phase (luteal phase of ovary) 2-3 days after ovulation,
The gradual rise in progesterone causes a reduction in cell division.
Glands increase in tortuosity, and distend…secretion of glycoproteins and lipids commences
Oedema, increased vascular permeability arterioles contract and grow tightly wound .
Myometrial cells enlarge and movement is suppressed and blood supply increases.
Describe menstruation
Prostaglandin released causes construction of spiral arterioles. Hypoxia causes necrosis.
Vessels then dilate and bleeding ensues
Proteolytic enzymes released from the dying tissue
Outer layer of endometrium shed, 50% lost in 24 hours, up to 80ml is considered normal. Bleeding normally lasts +4 days
Basal layer remains and is then covered by extension of glandular epithelium
Oestrogen from follicle in next follicular phase starts cycle off again
Why do we have so many cocps
Because they all have different combinations of amount of oestrogen and type of progesterone within them
What is used for induction of labour at term
Oxytocin
What is used for induction of labour/termination in early term
Prostaglandins (not oxytocin-no oxytocin receptors)
What is post partum bleeding
Prostaglandins oxytocin, ergots
What is used to prevent premature birth
B2 adrenoreceptor agonists
Calcium channel blockers, Mg sulfate
Oxytocin inhibitors
What does osteoclasts do
Eats away bone
What does osteoblast do
Forms new bone
Describe structure of testis
Testis produce soerm and store it
Produce hormones which regulate spermatogenesis
Optimum temp for soerm production is 1.5-2.5 below body
Overheating reduces sperm count
Well vascularised and innervater
Normal volume of testis is 15/25ml measured by orchidometer, which is a series of spheres where each sphere represents one volume
They have lobes which contain seminiferous tubules. The tubules lead to an area called rete.
Rete then leads to epididymis and vas deferens
Soerm are constantly being made and stored in epididymis
On outside of seminiferous tubules, you have the Leydig cell
Spaces between tubules are filled with blood, lymphatic vessels, leydig cells and interstitial fluid
Leydig cells are male equivalent of Theda cells, they make testosterone
Sertoli cells have testosterone receptors, need testosterone to produce male genitalia
Describe pathway of ejaculation
Vas deferens smooth muscle contract
Sperm move along vas deferens and meet at seminal vesicles gland (contribute some things)
Sperm then move to prostate gland and high contributes secretions into soerm
Then vas deferens meet at the urethra
Causes ejacukation
Corpus cavernous fills with blood to create hydrostatic pressure responsible for erection
Describe process of spermatogenesis
Sertoli cells lie along the inside of seminiferous tubules, and have tight junctions between them called adluminal compartments
Sertoli cells communicate with sperm
Sperm move down as being made along side Sertoli cells, then are released into lumen of seminiferous tubules
Sperm start on outer edge of seminiferous tubules as spermatogonia (diploid)
Soermatogonia reproduce by mitosis
Describe ejaculation
Sperm made in seminiferous tubules, move to rete, then into vas deferens. Vas deferens contract by smooth muscle contractions stimulated from sympathetic nervous system. Sperm then move into the seminal vesicle gland which contributes proteins, enzymes, fructose (50-70% ejaculate), then move into prostate gland which secretes milky, white fluid and inserts enzymes, proteins, and the vas deferens then meet the urethra.
Role of bulbo urethral gland
secretes pre ejaculate, which is high in salt and neutralises the urethra, makes the urethra ready for sperm. It lubricates the urethra.
Process of spermatogenesis
New cycle every 16 days.
Diploid germ cells divide mitotically, called spermatogonia. Some spermatogonia can then become primary spermatocytes where they are then committed to meiosis, and the rest can continue to divide mitotically (hence male have lifetime supply of sperm). Primary spermatocytes complete meiosis 1 and turn into seconary spermatocytes which are now haploid. Secondary spermatocytes can then undergo further meiotic division to produce spermatids, which are now truly haploid, as M2 is complete. Spermatids lose their cytoplasm, and undergo spermiogenesis which is where they develop a tail and acrosome. Each division of becoming sperm is incomplete, as the cells are connected by cytoplasmic bridges, forming a syncytium, allowing synchronous development. At the end the bridges are broken.
Spermatogenesis happens next to sertoli cells. Tight junctions between sertoli cells provide an enclosed and protective compartment called adluminal compartment to protect from blood supply, luminal system and toxic chemicals.
What are catsper channels
Voltage gated calcium channels on sperm surface
Respond to pH and other factors of egg
As sperm get closer to egg, environment becomes more alkaline, opens catsper channels
Calcium rushes in, sperm becomes hyper activated? Soerm get closer to egg and start to swim faster
Tails beat more forcefully with increased frequency and amplitude
WhT is acrosome reaction
Acrosome reaction happens when soerm hits coronal radiate cells
Sperm then becomes hyper activated by the catsper channels and they start fighting their way through the cells
Acrosome reaction happens, sperm enzymes then cut through zona pellucida
Adhesion molecules enable the zona pellucida and the sperm to bind together momentarily
There are several of these factors, a major one called ZP3
These adhesion molecules between sperm and pellucida are specifies specific
As sperm cut through zona pellucida, the soerm and egg lipid membrane then touch? Causing fusion
Acrosome reaction occurs in contact with zona cumulus complex-when acrosome last membrane on soerm head fused releasing enzymes that cut through the complex
Acrosin bound to the inner acrosome life membrane digests the zona pellucida so the sperm can enter the oocyte
Acrosin is a digestive enzyme bound on inner acrosin all membrane
What causes the LH surge
Sustained high oestrogen
Then LH surge causes meiosis 1 to complete and ovulation
First polar body extruded and you are left with the secondary oocyte (primary oocyte converted to secondary oocyte).
What is oocyte cumulus complex
It is oocyte about to ovulate with cumulus cells in antral follicle
Basement membrane breaks so blood pours into the middle
Oocyte cumulus complex extruded out and caught by fimbrae of uterine tube which picks up an egg.
Effect of progesterone to uterine tube and endometrium
Makes endometrium secretory and receptive to implantation
Suppressed cilia in uterine tubes once oocyte has already passed
Makes cervical mucus viscous again to prevent further sperm penetration
Cells differentiate
When progesterone falls, it causes differentiation of the endometrium making it receptive
When it eventually disappears, endometrium falls apart, becoming receptive
What does the menstrual cycle achieve
Selection of a single follicle and oocyte each month
Regular spontaneous ovulation
Ensures correct haploid number of chromosomes in the oocyte
Cyclical changes in the cervix and uterine tubes to enable egg transport and sperm access
Preparation of the endometrium of the uterus to receive the fertilised egg
Support of the implanting embryo and endometrium by corpus lutetium progesterone production
Initiating a new cycle in fertilisation
How does the sperm prevent other sperm from entering the egg after it has entered it?
2 things
Enzyme similar to phospholipiase C present in sperm membrane, becomes activated when soerm enters egg
It causes the egg to release its intra cellular calcium -produces IP3
Then wave of calcium sweeps through egg
WAve causes a corticol reaction
-release of corticol granules that release professes that remove/hydrolyse all receptors in zona pellucida so no more sperm can bind (block polyspermy).
Also they release peroxides and enzymes that cross link and harden zona pellucida so they become impenetrable to even sperm enzyme
What is syngamy
Sperm enters egg, causes calcium increase in egg and completion of M2.
this expels a second polar body so left with truly haploid egg and truly haploid sperm.
Sperm nuclear membrane then breaks down and the chromosomes all separate out.
After 4-7 hours after fusion, both the male chromosomes and female chromosomes become surrounded by distinct membranes, forming pro-nuclei, now there are 2 pro nuclei.
The 2 pro nuclei are 2 sets of haploid chromosomes. These haploid structures then begin to synthesise DNA in preparation for first mitotic division. The pronuclei fuse together, and the mitotic metaphase spindle forms with the chromosomes assuming their position at its equator. Pairs of chromosomes-male and female, line up and position themselves on mitotic spindle.
Mitosis then occurs, first division of cell.
Descrive IVF treatment
Sperm and eggs are mixed and left overnight in a nutrient medium. The next day, if you see the 2 pro-nuclei in the egg, this is the first sign of fertilisation. Some people argue this is actually the start of life.
After 3 days, developing embryo has 6-8 cells, called a morula. After 5 days of fertilisation ( 2 pro nuclei shown), there are approx 100 cells and embryo has started to differentiate.
Embryo now called a blastocyst has an inner cell mass, a fluid filled cavity called blastocoele, and the periphery is surrounded by trophoblast, that will become the placenta. Intercell mass will become everything else. They are totipotent stem cells.
When the egg turns into a blastocyst, then it will implant into endometrium.
what cells are found in uterine tubes?
ciliated cells and secretory cells
effect of oestrogen on cells of uterine tube
When oestrogen high, it causes differentiation in cells of uterine tube. Cells differentiate and grow taller, ciliated cells start to beat, secretory cells secrete growth factors By the time of ovulation, there is a nice environment, inside uterine tube, for fertilisation,
what is window of receptivity of the uterine tube
Uterine tube shuts off at the end of menstrual cycle.
Endometriosis
Cells from endometrium move to uterine tube and block it.
cells of endometrium implant somewhere in pelvis where they respond to oestrogen and progesterone, hence they proliferate and differentiate then shed. This can be an inflammatory response. They can block fallopian tube or block outside of it as they move to pelvis.
adhesions in uterine tube
Pelvic inflammatory disease, inflammation in uterine tube.
What can block uterine tube
endometriosis, adhesions, infections, STIs, SURGICAL PROCEDURES.
