Repro 1.2 Spermatogenesis And Oogenesis Flashcards
What is the difference between spermatogenesis and spermiogenesis?
Spermatogenesis- the formation of spermatozoa from the germ cells.
Spermiogenesis- the maturation of spermatids into spermatozoa which are fully mobile. This stage is finished by the epididymis.
What is the first stage of spermatogenesis?
The division of the diploid germ cell into Ap and Ad cells.
Ap is the primordial spermatocyte.
Ad is what maintains the stock of the germ cells.
What is spermiation?
The release of the spermatids into the seminiferous tubules.
It is the first step in spermiogenesis
What happens in spermiogenesis?
- spermiation
- remodelling of the sperm through the duct system
- gaining of motility within the epididymis
What are the 4 components of ejaculate?
- sperm cells
- seminal vesicles producing 70% of volume, including fructose, amino acids, citrate and prostaglandins
- prostate gland- proteolytic enzymes
- bulbourethral glands- produce mucoproteins which help to lubricate (aiding sperm movement) and to neutralise any acidic urine in the distal urethra.
What is the final stage of sperm maturation and where does it occur?
Capacitation
The female reproductive tract
What happens during capacitation?
The female reproductive tract conditions cause the following:
- removal of cholesterol and prostaglandins from the head of the sperm
- activation of sperm signalling
- allows the sperm to bind to zona pellucida to initiate the acrosome reaction.
What’s important about the medium used in IVF?
It has to stimulate that of the female reproductive tract to allow th final stage of maturation of sperm.
How much sperm do males produce?
Around 7 million per day.
How many eggs do females produce?
Around 400 that reach full maturation, enough for one a month for around 35-40 years
The first step is mitosis of the oocytes to amplify the number, but some enter meiosis. What stage do they arrest at?
Prophase 1.
By mid gastrulation there are may oocytes, how are they arranged?
In clusters,
Surrounded by a single layer of flat epithelial cells
By birth, many of the oocytes have undergone atresia, of the ones that are left, what stage are they at?
They have all entered meiosis 1 and arrested in prophase 1. They all have a thin epithelial surrounding.
Describe the primordial follicle.
One single oocyte (not a cluster) surrounded by a single layer of follicular cells.
Describe what happens in the preantral stage.
The simple squamous folliclaur cells become stratified cuboidal, forming granulosa cells.
The granuloma cells secrete glycoprotein to form the zone pellucida around the oocyte.
What happens in the Antal stage?
The granulosa cells secrete fluid, which forms and Antrum.
How may oocytes reach the antral stage per menstrual cycle
Only 1-2.
The others undergo atresia.
What happens in the preovulatory stage?
Meiosis 1 is complete.
This causes the production of 2 haploid cells.
Only one takes the cytoplasm, the other becomes a polar body.
The oocyte enters meiosis 2 and stops metaphase. Meiosis 2 will only be completed if fertilisation occurs.
What is the mature follicle known as?
Graafian follicle
Describe ovulation.
LH surge causes prostaglandin release an smooth muscular contraction of the ovary
This causes the expulsion of the oocyte from the ovary
Once the oocyte has been extruded from the ovary, where does it go?
It is released into the peritoneum, but the fimbriae of the uterine tubes sweep it into the uterine tubes.
How is the oocyte transported to the uterus from the ovaries?
The fimbriae sweep the oocyte into the uterine tube.
Mucus aids movement of the oocyte.
Muscular contractions help it move along, as well as cilia embedded within the mucus,
What is the function of the corpus leuteum?
It continues to produce progesterone and oestrogen, to maintain the endometrium whilst waiting to see if the oocyte has been fertilised
What happens to the corpus leuteum if the oocyte isn’t fertilised?
It will degenerate after 14 days.
No progesterone production leads to the beginning of menstruation.
What happens to the corpus leuteum if the oocyte is fertilised?
The syncitiotrophoblast of the embryo will produce human chorionic gonadotropin, this maintains the corpus leuteum and stops it from degenerating,
It continues to produce progesterone until the placenta is big enough to take over.
How long does the oocyte last after ovulation?
It is viable for 1 day.
After this, It will degenerate and can no longer be fertilised.
What do the sertolli cells secrete?
Inhibin
Androgen binding globulin
Mullerian inhibitin hormone
What is the function of androgen binding hormone?
It binds to the testosterone produced by the leydig cells.
How is the blood testes barrier formed?
What’s it’s purpose?
Tight junctions between the sertolli cells, which prevents communication between the sperm and the blood.
This prevents antibodies being made against the sperm
What is the spermatogenic wave?
The distance between the same 2 stages of spermatogenesis along a tubule.
What is the spermatic cycle?
What’s average?
The time it takes for the reappearance of the same stage of spermatogenesis in the same part of the tubule.
This is usually around 16 days in humans.
