Session 1 - Part II Flashcards
Which part of the gonad will XX germ cells colonise?
The cortex
Which part of the gonad will XY germ cells colonise?
The medulla
What do female germ cells become when they colonise the gonadal cortex?
Oogonia (Diploid cells)
What do Oogonia do?
Proliferate rapidly by mitosis
When is the maximum number of Oogonia reached?
Mid gestation. However, most will die
When do Oogonia enter the first first phase of the 1st meiosis division?
Before birth. They are then suspended at this stage
Now called Primary Oocytes
What surrounds the Primary oocyte?
A single layer of granulosa cells of gonadal origin. Called primoridal follicle
When do the primordial follicles begin to develop further?
At puberty.
Most developing die, but one or two complete development and are released - ovulation
How long is the fertility period?
36 hours
What stage of the cycle precedes ovulation?
Preparation period
What happens in the Preparation period?
The ovum develops (Follicles developing)
The reproductive tract prepares for sperm transport and implantation (Uterus lining thickens)
The rest of the body undergoes changes to maximise chances of conception
What are the stages of the Menstrual cycle?
Preparatory phase (Follicular/proliferative phase)
Ovulation
Waiting phase (Leuteal/secretory phase)
It is timed from the onset of bleeding
What days in the menstrual cycle is the preparatory phase ?
0-12
What days in the menstrual cycle is the ovulation?
12-14
What days in the menstrual cycle is the waiting phase?
14-28
Why is there a waiting phase in the Menstrual cycle?
Because when the ovum is first fertilised it is too small to indicate its presence.
What happens in the waiting phase of the Menstrual cycle?
Further production of gametes is suspended until pregnancy can be confirmed by secretion of placental hormone
What is the first stage in follicular development?
The primordial follicles develop to pre antral follicles (Aka secondary oocytes)
This is independent of hormones
What are the cellular changes in the first stage in follicular development?
A zona pellucida develops
The single layer of granulosa develops into multiple
Theca interna & externa develop (Gonadal origin)
What is the role of the Theca interna?
It is vascular and secretes hormones (eg oestrogen proportionally to size of the follicle. This is important for control)
What is the role of the Theca interna?
It is thick and supports the follicle
What triggers the pre ovulatory follicle to rupture and release the ovum?
Leuteinizing hormone
When does meiosis restart in the ovum?
Just before ovulation
How are polar bodies developed?
The first division of meiosis is completed, but the division is unequal which results in all the cytoplasm going to the oocyte and the extra DNA is disposed in a polar body.
When is the second division of meiosis?
After fertilisation
What is a corpus luteum?
A solid body of cells
What happens to the follicle after ovulation?
It forms a corpus luteum
Grows under the influence of leuteinizing hormone
Secretes oestrogen & progesterone
Will die after 14 days if no ovum detected*
Why does the follicle secrete oestrogen & progesterone after ovulation?
It makes the system wait
Where do the XY germ cells colonise?
The sex cords which are in the testis
Do the germ cells proliferate before birth in male embryos?
Yes via mitosis. Called spermatogonia
Do spermatogonia stay in the testis for life?
Yes. It allows the male to have raw material to create sperm for his whole life
What happens to the sex cords at puberty?
They hollow out forming seminiferous tubules (Blind ended tubules that end in the rete testis)
What happens to spermatogonia at puberty?
They cluster around the periphery of the newly formed seminiferous tubules
How are primary spermatocytes formed?
The spermatogonia divide by mitosis (A fixed number of times) to form a clone of cells all linked by cytoplasm (Remain diploid)
How do primary spermatocytes form spermatids?
Meiosis begins and each spermatocyte forms 4 haploid spermatids. It moves towards the lumen as it does this.
Meiosis will be finished by the time it reaches the lumen
When does the remodelling of spermatids to spermatozoa occur?
As they pass down the spermatic tubule through the rete testis, ductus efferentes and epididymus.
How does a spermatozoa reach the urethra from the epididymus?
Via the vas deferens
What constitutes semen?
Secretions of the seminal vesicle = 60%
Secretions of the prostate = 20%
Sperm (Via the vas deferens)
Secretions of the bulbo-urethral gland
What controls the emission (Mixing) of semen?
The sympathetic branch of the ANS as it causes contraction of the smooth muscle in the walls of the tubules
What controls the ejaculation of semen?
The parasympathetic branch of the ANS
