Reproduction 1 Flashcards
Presence of the Y chromosome leads to male gonad development due to the presence of what gene? The non-functional X chromosome condenses to form nuclear mass known as what in females?
SRY gene
Barr body- lyonisation
Both female and male gonads are derived from what? Up until what week are primordial gonads are undifferentiated? The undifferentiated reproductive tract includes what?
The urogenital ridge
6th week
A double genital duct system: Wolffian ducts, Mullerian ducts
What ducts persist and regress in the male? The Sertoli cells of the testes produce what protein hormone? What gene induces the expression of MIF? Testosterone from Leydig cells causes what to happen?
Wolffian ducts persist and Mullerian ducts regress
Mullerian-inhibiting factor- MIF
SRY gene–> Mullerian duct degenerates
Wolffian duct–> epididymis, vas deferens, ejaculatory ducts and seminal vesicles
Externally, under the influence of what does the penis form and tissue near it fuse to form the scrotum? What does testosterone also stimulate?
Dihydrotestosterone (DHT) produced from testosterone
The testes to descend into the scrotum
In the female, the Mullerian system develops into what? What structure does not play a role in developmental processes? What are germ cells? Where do they originate from?
Fallopian tubes and a uterus
The ovaries
Specialised that develop into sperm and ova
The yolk sac of the hind gut
When does mitosis in germ cells occur in males? In females?
Some in embryonic testes to form primary spermatocytes present at birth- begins during male puberty and continues throughout birth
During fetal development–> primary oocytes
What are the results of the first meiotic divisions in males? In females? The second cell is what in females?
Secondary spermatocytes
Secondary oocyte
The first polar body which has no function
When does the second meiotic division occur in males? In females? This results in what?
Continuously after puberty with spermatids and mature sperm cells produced
Not until after fertilisation of secondary oocyte by a sperm
A zygote and the second polar body which also has no function
What is semen? % which is seminal vesicle fluid, prostatic and sperm? Included in prostate and seminal vesicle secretions?
Fluid and sperm cells together
60% seminal vesicle fluid, 30% prostatic and 10% sperm
Buffers to protect sperm against acidic vaginal secretions, chemicals to increase sperm motility e.g. fructose, prostaglandins to stimulate female peristaltic contractions
Mnemonic to remember path of sperm to outside?
SREEVEN UP
Seminiferous tubules, rete testis, efferent ducts, epididymis, vas deferens, ejaculatory duct, nothing, urethra, penile urethra.
What is each seminiferous tubule bounded by? How are Sertoli cells located in the testes?
A basement membrane
Each extends from the membrane to the lumen in the centre and is joined to adjacent ones by tight junctions
Two compartments tight junctions divide the tubule into?
Basal compartment- between membrane and tight junctions and central compartment- beginning at tight junctions and including the lumen
What does the arrangement of Sertoli cells allow (blood-testes barrier)?
Prevents chemical moving from blood into lumen of seminiferous tubule, ensures proper conditions for germ cell development and differentiation within the tubules, permits different stages of spermatogenesis to take place in different compartments and thus different environments
What are undifferentiated germ cells called? When they begin to divide? They produce what types of daughter cells? Type A and Type B daughter cell do what?
Spermatogonia
At puberty
Type A- remain outside blood-testes barrier and produce daughter cells until death
Type B- differentiated into primary spermatocytes (in basal compartment)
Where must primary spermatocytes pass through to to gain entry into the central compartment? What then happens? In Meiosis 2, the secondary spermatocytes differentiated into what?
The blood-testis barrier through tight junctions of Sertoli cells
They undergo meiosis 1–> 2 secondary spermatocytes
4 spermatids
How do spermatids become spermatozoa? What is this also known as? What happens when sperm formation is complete?
They grow a tail and discard their cytoplasm to become lighter
Spermiogenesis
The cytoplasm of the Sertoli cells around the sperm retracts and the sperm are released into the lumen to be bathed in luminal fluid
What is the tip of the nucleus covered by? Mitochondria form what section of the sperm?
The acrosome- a protein-filled vesicle containing enzymes to penetrate the egg
The midpiece- provide energy for movement
GnRH secreting neuroendocrine cells of the hypothalamus fire a brief burst of action potentials how often? GnRH travels where to stimulate the release of what 2 hormones?
Every 90 minutes- secrete GnRH
The anterior pituitary via the hypothalamo-hypophyseal portal vessels- release LH and FSH
In males, FSH acts on what cells to stimulate the secretion of what? LH acts on what cells to stimulate what secretion? Testosterone travels where and does what?
The Sertoli cells to stimulate the secretion of paracrine agents to initiate spermatogenesis
Leydig cells- stimulate testosterone secretion
Diffuses from interstitial spaces into seminiferous tubules–> Sertoli cells where it facilitates spermatogenesis
What hormone does testosterone inhibit the secretion of? In what 2 ways does it do this?
LH
1) Acts on hypothalamus to decrease amplitude of GnRH burst 2) Acts on anterior pituitary to decrease LH response to GnRH
Sertoli cells release what hormone which acts on anterior pituitary to inhibit the release of FSH? Around what month of gestation do the fetal oogonia stop dividing? During fetal life, how many oogonia turn into primary oocytes?
Inhibin
7th month
All oogonia differentiate into primary oocytes
When does Meiosis I begin in females? When is meiosis then arrested at metaphase 1 until? Known as? Only what eggs will complete meiosis 1? What occurs during Meiosis 2?
In-utero before 12 weeks Until puberty Meiotic arrest Eggs destined for ovulation The secondary oocyte develops into the ovum
When is Meiosis 2 arrested until in females? Before puberty. low level of what hormones? What happens at puberty? What is normal puberty influenced by?
Until fertilisation
GnRH and GHRH from hypothalamus, anterior pituitary; FSH, LH, GH and gonadal sex steroids
Increase in GnRH and GHRH, FSH, LH, GH and sex steroids
Nutrition, insulin, genetic factors and exercise
Male changes in puberty? Female changes in puberty?
Testicular enlargement, pubic, axillary and facial hair growth, growth spurt, spermatogenesis begins, acne, body odour and mood changes
Breast development, pubic and axillary hair growth. growth spurt, menarche, acne, body odour and mood changes
When is the follicular phase? Follicles begin as what? What does this consist of? What do granulosa cells secrete?
Day 1-13
Primordial follicles
Primary oocyte surrounded single layer of cells called granulosa cells
Oestrogen, small amounts of progesterone before ovulation, inhibin
Primordial follicle develops into what? What happens then? What passes through these gap junctions?
Primary follicle
Oocyte increases in size, it becomes separated from inner granulosa cells by zona pellucida secreted by outer follicular cells, inner granulosa cells stay in contact with oocyte via cytoplasmic processes and form gap junctions
Nutrients and chemical messengers to the oocyte
Primary follicle develops into what? What happens then? Theca and granulosa cells function together to form what?
Preantral follicle
Follicle grows larger through mitosis of granulosa cells, connective tissue cells around granulosa cells forms layer cells known as the ‘theca’
Oestrogen
Preantral follicle develops into what? What happens then? Majority of follicles in ovaries are what?
Early antral follicle- primary oocyte reaches full size. fluid-filled space called antrum forms in midst of granulosa cells due to fluid they secrete
Still primordial, constant numbers of preantral and early antral follicles
At start of period, how many preantral and early antral follicles–> larger antral follicles? 1 week in, only what continues to develop? Selected based on what? Non-dominant follicles undergo what process instead?
10-25
Dominant follicle- condition of oocyte and on oestrogen production
Atresia- form of cell death
As the time for ovulation approaches, what happens to primary oocyte? Due to surge in what? What follicle becomes so large, it balloons out on surface of the ovary? When does ovulation occur?
It emerges from meiotic arrest- due to LH–> secondary oocyte
Graafian follicle
When thin walls of follicle and ovary rupture at site where they are joined due to enzymatic digestion
What occurs during ovulation? When does this happen?
Secondary oocyte is carried out of the ovary and onto the ovarian surface by antral fluid= day 14
When is the luteal phase? What happens then and what structure forms? This structure secretes what 3 hormones? It reaches maximum development within how many days? Degenerates by what process?
Day 14-28 Follicle discharged antral fluid and egg, it collapses, granulosa cells enlarge greatly--> corpus luteum forms Oestrogen, progesterone and inhibin 10 days Apoptosis- this triggers menstruation
Oestrogen produced by what? Progesterone made and released by what cells and when? Sequence of menstrual phase depends on levels of what?
Granulosa cells mainly during follicular phase, then by corpus luteum after ovulation
By granulosa and theca cells just before ovulation, then by corpus luteum
GnRH- change over 24 hours over menstrual cycle
What is FSH needed for? Why does this increase as one cycle ends and next begins? It stimulates what in the first week?
Follicle development beyond preantral and early antral
Progesterone, oestrogen and inhibin decrease- remove -ve feedback on hypothalamus and anterior pituitary
The granulosa cells to multiply and produce oestrogen and antrum to enlarge
What does oestrogen act as within the follicle? As the dominant follicle matures, FSH induces what to appear on the granulosa cells? Why does FSH decrease more than LH?
A paracrine/ autocrine agent- stimulates proliferation of granulosa cells- further increases oestrogen production
LH receptors
Granulosa cells secrete inhibin which inhibits mainly FSH secretion
When is the ‘LH surge’? Followed by what? LH acts on theca cells in the first week to do what? Where do these androgens then diffuse into and do?
Around 18 hours before ovulation
Rapid decrease and then a further slow decline during the luteal phase
To proliferate and to make androgens- granulosa cells and converted to oestrogen by aromatase
When does oestrogen levels increase rapidly? Decreases before what has peaked? Followed by what? Ends with what?
Low and stable in 1st week–> increases rapidly during second week and dominant ovarian follicle grows and secretes more oestrogen
Before LH peak–> a second increase due to secretion by corpus luteum
Rapid decrease during last days of cycle
When are very small amounts of progesterone released by the ovaries? Why large increase? When does inhibin increase?
During the follicular phase until just before ovulation
Due to corpus luteum- the rapid decrease during last days of cycle
During late follicular phase–> high during luteal phase and decreases until corpus luteum degenerates
Large oestrogen amounts during luteal phase act on anterior pituitary to do what? Leads to what? Why does LH surge start to decline?
Increase sensitivity of LH-releasing cells to GnRH (from hypothalamus)= +ve feedback mechanism
LH surge and ovulation–> act upon granulosa cells induce ovulation
Due to small increase in progesterone from corpus luteum inducing -ve feedback on anterior pituitary and hypothalamus
Corpus luteum degrades within how many weeks if no pregnancy? Day 1 of period known as what? Epithelia lining uterus known as what degenerates?
2 weeks
The Menstrual phase- lasts 3-5 days
The endometrium–> menstrual flow
From 5 of menstrual cycle, known as what? What happens then?
The proliferative phase- around 10 days
Flow ceases, endometrium begins to thicken due to oestrogen–> growth of endometrium and myometrium (underlying smooth muscle), also synthesis of receptors for progesterone in endometrial cells
After the proliferative phase, what phase occurs? What happens then? What acts upon the oestrogen-primed endometrium to turn it into an actively secreting tissue?
The secretory phase- between ovulation and onset of next menstruation
Endometrium starts to secrete glycogen in glandular epithelium, then glycoproteins and mucopolysaccharides
Progesterone- makes endometrium a hospitable environment for implantation and nourishment of embryo
How does progesterone influence the myometrium?
Progesterone inhibits myometrial contractions- opposing stimulatory actions of oestrogen and prostaglandins (ensures fertilised egg can safely implant into uterus)
How does oestrogen affect the cervical mucus? most pronounced when? Progesterone influences cervical mucus how?
Makes it abundant, clear and watery
During ovulation to allow sperm to move easily on way to uterus and fallopian tubes
Thick and sticky- after ovulation (plug prevents bacteria from entering uterus via vagina)