Reproductive physiology Flashcards
Where GnRH, LH, FSH and Testosterone released
Gonadotrophin releasing hormone (GnRH)
Hypothalamus
Luteinising hormone (LH) Anterior pituitary
Follicle stimulating hormone (FSH)
Anterior pituitary
Testosterone (T)
Testis
Where do inhibin and testosterone negatively feedback
Inhibin from sertoli cells (in response to FSH) feed back on ant. pituitary to reduced FSH
Testosterone from Leydig cells (in response to LH) feed back on hypothalamus and anterior pituitary to reduce LH
Outline the chromosome number in each of the following cells from spermatogenesis:
Primordial germ cell
Spermatogonium
Primary spermatocyte
Secondary spermatocyte
Spermatids
Mature sperm
all 46 until secondary spermatocyte
secndary spermatocyte onwards has 23
What are spermatogonium
The spermatogonium come from mitotic division of primordial germ cells
Testes are the source of what
Sperm
Testosterone
Function of human male reproductive tract
When is testosterone important
Ihe two main functions are the provision of androgens (primarily testosterone) to initiate and sustain the necessary male phenotype,
and the production of mature sperm.
Testosterone importnat for IU growth of males but not importnat until age 12 for puberty
Does the name of the hormones affecting male reproductive tract (FSH and LH) reflect its action
In the testes there are no follicles. The hormone names are derived from information obtained on the female reproductive system
Waht is the pattenr of LH and FSH release
Pulsatile (more pulsatile for LH)
Where are the leydig cells
In the interstitium
What is the release of teststerone like
Cyclic
It acts locally at the site of production in the testes then is released into the circulation, from where it can affect the whole body.
What is sertoli cell funtion based on
FSH and testosterone (both required)
ABP (androgen binding protein very important)
Compartments of the testes
Seminiferous tubles
Interstitial
Where are the mature sperm in the seminiferous tubles
In the lumen
The lumen leads to epidiymis
Outline the divisions taking place in sperm cell division
Mitotic division first (to create a large enough pool)
Then late stages meiotic division to develop 4 haploid cells
When does male reproductive function start
When does it function
Starts at puberty
Functions continually
and throughout the rest of life
Does sperm quality or quantity decrease with age?
Sperm quantity and quality generally decreases with increasing age
Differentiate the function of males and female reproducitve system
Male functions continuously
Female functions CYCLICALLY
Does egg quality decrease with age>
Yes
Function of FSH and LH in women
FSH stimulates (some) development of ovarian follicles &; 17b-estradiol synthesis
LH stimulates progesterone production
What is difference between LHRH and GnRH
Same thing
GnRH is very pulsatile LH release is matched to this
But FSH less pulsatile
Function of steroids in females
Act on reproductive tract
And act on the uterus too
What happens with GnRH, FSH and LH and oestradiol effect in folluclar phase, midcyle and luteal phase
In follicula rphase, estradoil is reducing GnRH release from hypothalamus and FSH/LH from the ant pit.
In the midcycle, oestradiol is then positively feedbacking on hypothalamus and ant pit to increase GnRH and FSH/LH
In the luteal phase, same as follicular phase BUT the main steroid being produced by ovary is progesterone not estradiol
T/f only progesterone is present in the luteal phase
F…. also moderately high oestrogen production.
For implantation, progesterone dominance in the presence of oestrogen required
What is the average menstrual cycle length
28 days
on average… stress can change things
If the menstrual cycle changes in length, which part does this
The luteal phase increases in length (follicular phase constant)
What is the thickness of endometrium at minimum (ie. after menses) to maximum (high progesterone)
2-4mm at min.
7-16mm at max
What hormones are important for which stage of the menstrual cycle (uterus)
ESTROGEN –> proliferative stage
PROGESTERONE DOMINANCE with oestrogen –> secretory phase
How long does corpus luteum make steroids for
Arond a week to ten days following ovulation
GnRH falls towards the end of the cycle, and so will LH. So progesterone also falls towards end of secretory phase
How are eggs developed
Primordial follicle (developed during intrauterine life…. born with millions)
MINORITY mature into:
Primary follicle
t/f primordial follicle and primary follice both contain primary oocyte
True…
Structure of follice
It has an antrum (fluid filled space) with the primary oocyte in the middle and the luteal cells around the side
T/f the development of follicles occurs over 1 month period
F…. actually 3 months
Differentiate the development of oogonia nad spermatogonia
SPERMATOGONIA DEVELOPED BY MITOSIS DURING LIFE
OOGONIA LAID DOWN IN INTRAUTERINE LIFE AND NO MORE PRODUCED THROUGHOUT LIFE
Outline folliculogenesis
Over 3 months,
so various stages of follicle development at any time
Dominant follicle selected
What is metaphase II arrest
Ovulation = release of mature oocyte (egg) from the ovary
Oocyte is 2n at this stage, in meiotic arrest (metaphase II)
How long do eggs last and when can fertilisation occur
Enters the Fallopian tube
Needs to be fertilised within 24 hours, as it degenerates after this
(luckily sperm can surivive for 3 days so intervourse near time of fertilisation is sufficient for pregnancy)
Outline fertilisation
Egg is chemoattractant for sperm
Sperm release enzyme to break down zona peluida
What happens to chromosomes in the sperm after fertilisation
Develop into the male pronucleus
DNA decondense (was packed into the sperm)
What happens to male and female pronuclei
The nuclei approach each other (approximation)
As soon as pronuclei are near each other, the nuclear membrane breaks down and spindle fibres immediately form so that a division immediately takes place to form 2 identical cells
I.E. THERE IS NO FUSION OF MALE AND FEMALE PRONUCLEUS
What happens to DNA in the pro-nuclear stage
replication of the haploid DNA occurs
There is no diploid nucleus formed by combination of the two pronuclei…… replication occurs and then division happens
Chromatids in both pronuclei are duplicated
They align on the mitotic spindle, and are separated into 2 identical ‘daughter’ cells (1st cleavage division of the embryo).
What occurs in maternal chromosomes after fertilisation
Meosis of maternal chromosomes resumes, forming female pronucleus (23 chromatids), and 2nd polar body.
Then there is replication of the DNA
How frequenty are eggs released from each ovary
Supposed to be alternating (left ovary one month and right ovary the next)
BUT
if ovary is removed then it will take place every month from one egg
What is epididymis function.
One within each scrotal sac. Sperm are released from the testis and stored here prior to ejaculation.
Journey of sperm at ejaculatin
From epidiymis, At ejaculation sperm pass through the two Vas Deferens (which are contractile), and are mixed with fluid from the seminal vesicles. The fluid then leaves the ejaculatory duct, and passes into the urethra where it mixes with secretions from the prostate gland.
How many sperm produced per day
The overall production of sperm from both testes is estimated to up to 200 million sperm per day.
Which cells are there within a follicle
Oocyte (middle)
Around the outside:
thecal cells and granulosa-luteal
what are thecal cells and granulosa-luteal cells responsible for
thecal cells of the developing follicles are responsible for the production of estrogens, and the granulosa-luteal cells produce estrogens and progesterone during the second half of the ovarian cycle.
Differentiate the proliferative and secretory phase of the endometrial cycle and the days at which is occurs
Menstrual phase is until day 5
Proliferative- day 9
- Stimulation of endometrial proliferation
- increase in thickness
- number of glands, and length of arteries increases
Secretory- day 13
- production of nutrients and other factors
- epothelial glands widen, endometrium thickens and increased coiling of spiral arteries
What cuases proliferative stage and what causes secreotry phase
Proliferative: E2
Secretory: progesterone dominnce with presence of E2
When exactly does oestrogen act as postive feedback and when does it act as negative feedback on the hypothalamus and pituitary
Negative feedback in early & mid follicular phase, as well as luteal phase (E2 &P)
Positive feedback in the late follicular phase
When does oestrogen peak
A few dyas before ovulation (so a few days before day 14)
When does basal body temperature change during mesntual cycle
the basal body temperature rises slightly (about 0.5°C) around the time of ovulation
What stimulates the oocyte to complete meiosis 1.
When does meiosis II occur
The first meiotic division is completed during the formation of the secondary follicle, linked to the LH surge. Meiosis I starts during embryonic development, but halts at the diplotene stage of prophase I (primary follicle); this persists until puberty when meiosis resumes as secondary follicles develop
Meiosis II follows immediately after this, but pauses in metaphase II
What causes completiiton of meiosis II
Fertilisation
T/f babies are already born having had lots of their oocytes died
T
Contain ~6 million primordial follicles at ~20 weeks of development.
By delivery of the infant, this has fallen to ~1 million per ovary.
How many follicles ovulate during reroductive life
400ish
What is sexual reproduction
Produces offspring that differ genetically from both parents.
Which other brain pathways involved in reproduction
Nigrostriatal tract
Mesolimbic dopaminergic system (pathway for reward and pleasure)
Control of penile erection
Brain (limbic system) –> spinal cord –> efferent
Or tacile system can activate afferent system via pudendal nerve. Still involves spinal cord
Explain how erection occurs
Increased PNS to smooth muscle of pudendal artery
Increases NOS, more NO.
Increases cGMP, causing arterial SM dilation , counteracting SNS myogenic tone
Increased blood flow in corpus cavernosum
Compresses dorsal vein, restricting outflow of blood.
Why is the urehtera protected from the high presures of the corpus cavernosum during penil erection
The urethra is protected from increased pressure by surrounding corpus spongiosum (less turgid)
What is the mechanism of action of viagra
Cyclic GMP is normally de-activated by a phosphodiesterase enzyme (so reverses erectin)
Viagra inhibits the phosphodiesterase, thus potentiating the effects of cyclic GMP.
What equivalent tissue in females is erectile
Clitorus, using same cGMP mecahnism
What changes occur to cervical mucosa mid-cycle
Cervical mucus is normally hostile to sperm
This forms a physical barrier to sperm
Cervical mucus changes at mid-cycle
This change permits sperm to enter uterus
What happens once sperm has entered th uterus
Passage of sperm through uterus
Passage of sperm into Fallopian tube
Swim from there to Fallopian tube ampulla
What is capacitation
Capacitation is essential preparation before the sperm meet the oocyte (see endo)
What happens to the egg when the sperm enters
Rapid membrane depolarisation
Cortical reaction, leads to hardening of zona pelucida and exclusin of other sperm and inactivation of ZP3 receptors
t/f the cumuls cells are surrounding the oocyte and are within the zona pellucida
F…. they are outside the zona pellucia
figure 2.13
What must occur before formation of pronucleus
Maternal chromosomes separate and form 2nd polar body and female pronucleus
There are now 2 pronuclei (one from sperm one from egg) whihc are both haploid
In order for the now fertilised egg to divide to start forming embryo, the now diploid cell must divide. Outline how this occurs
So there was haploid pronuclei –> 23 chromosomes in each (and these are not replicated)
Now the two pronuclei are in the same cell, so there are 46 chromosomes, unreplicated.
We now need 2 daughter cells.
Note that there is no formation of a diploid nucleus in the egg.
Simply, before mitosis, the 23 chromosome from each pronucleus divides, dissolves plasma membrane, and then mitosis occurs.
All the replicated chromosomes will line up in one line as is customary in mitosis, and so each daughter cell will receive all the maternal and all the paternal chromosomes
When do the maternal and paternal chromosomes mix for the first time
Maternal and paternal chromosomes mix for the first time, as the metaphase plate of the first cleavage division is formed
