Repro 1.2 Spermatogenesis And Oogenesis

Question 1

What is the difference between spermatogenesis and spermiogenesis?

Answer 1

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.

Question 2

What is the first stage of spermatogenesis?

Answer 2

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.

Question 3

What is spermiation?

Answer 3

The release of the spermatids into the seminiferous tubules.
It is the first step in spermiogenesis

Question 4

What happens in spermiogenesis?

Answer 4

• spermiation
• remodelling of the sperm through the duct system
• gaining of motility within the epididymis

Question 5

What are the 4 components of ejaculate?

Answer 5

• 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.

Question 6

What is the final stage of sperm maturation and where does it occur?

Answer 6

Capacitation

The female reproductive tract

Question 7

What happens during capacitation?

Answer 7

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.

Question 8

What’s important about the medium used in IVF?

Answer 8

It has to stimulate that of the female reproductive tract to allow th final stage of maturation of sperm.

Question 9

How much sperm do males produce?

Answer 9

Around 7 million per day.

Question 10

How many eggs do females produce?

Answer 10

Around 400 that reach full maturation, enough for one a month for around 35-40 years

Question 11

The first step is mitosis of the oocytes to amplify the number, but some enter meiosis. What stage do they arrest at?

Answer 11

Prophase 1.

Question 12

By mid gastrulation there are may oocytes, how are they arranged?

Answer 12

In clusters,

Surrounded by a single layer of flat epithelial cells

Question 13

By birth, many of the oocytes have undergone atresia, of the ones that are left, what stage are they at?

Answer 13

They have all entered meiosis 1 and arrested in prophase 1. They all have a thin epithelial surrounding.

Question 14

Describe the primordial follicle.

Answer 14

One single oocyte (not a cluster) surrounded by a single layer of follicular cells.

Question 15

Describe what happens in the preantral stage.

Answer 15

The simple squamous folliclaur cells become stratified cuboidal, forming granulosa cells.
The granuloma cells secrete glycoprotein to form the zone pellucida around the oocyte.

Question 16

What happens in the Antal stage?

Answer 16

The granulosa cells secrete fluid, which forms and Antrum.

Question 17

How may oocytes reach the antral stage per menstrual cycle

Answer 17

Only 1-2.

The others undergo atresia.

Question 18

What happens in the preovulatory stage?

Answer 18

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.

Question 19

What is the mature follicle known as?

Answer 19

Graafian follicle

Question 20

Describe ovulation.

Answer 20

LH surge causes prostaglandin release an smooth muscular contraction of the ovary
This causes the expulsion of the oocyte from the ovary

Question 21

Once the oocyte has been extruded from the ovary, where does it go?

Answer 21

It is released into the peritoneum, but the fimbriae of the uterine tubes sweep it into the uterine tubes.

Question 22

How is the oocyte transported to the uterus from the ovaries?

Answer 22

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,

Question 23

What is the function of the corpus leuteum?

Answer 23

It continues to produce progesterone and oestrogen, to maintain the endometrium whilst waiting to see if the oocyte has been fertilised

Question 24

What happens to the corpus leuteum if the oocyte isn’t fertilised?

Answer 24

It will degenerate after 14 days.

No progesterone production leads to the beginning of menstruation.

Question 25

What happens to the corpus leuteum if the oocyte is fertilised?

Answer 25

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.

Question 26

How long does the oocyte last after ovulation?

Answer 26

It is viable for 1 day.

After this, It will degenerate and can no longer be fertilised.

Question 27

What do the sertolli cells secrete?

Answer 27

Inhibin

Androgen binding globulin

Mullerian inhibitin hormone

Question 28

What is the function of androgen binding hormone?

Answer 28

It binds to the testosterone produced by the leydig cells.

Question 29

How is the blood testes barrier formed?

What’s it’s purpose?

Answer 29

Tight junctions between the sertolli cells, which prevents communication between the sperm and the blood.

This prevents antibodies being made against the sperm

Question 30

What is the spermatogenic wave?

Answer 30

The distance between the same 2 stages of spermatogenesis along a tubule.

Question 31

What is the spermatic cycle?

What’s average?

Answer 31

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.