Gamete formation

Question 1

Where are germ cells found in the male?

Answer 1

They colonise the sex cords in the primordial gonad – will develop into the testes

Question 2

What will the sex cords become?

Answer 2

They will hollow out at puberty to form the seminiferous tubules which the spermatagonia clustering around the periphery of the lumen

Question 3

Where do you find the seminiferous tubules?

Answer 3

The tubules are found circling the outer edge of the testes, with the open end of the blind ended tube draining into the rete testes. There are about 250-750 tubules per testis.

Question 4

What do the seminiferous tubules drain into?

Answer 4

The rete testis which then drain into the ducti efferentes, to the epididymis and then to the vas deferens

Question 5

How do the numbers of spermatagonia remain the same?

Answer 5

They are maintained by mitosis which produces a population of self-regenerating stem cells. After each division, two identical daughter cells are produced.

Question 6

What are the two types of stem cells which are produced from spermatogenesis?

Answer 6

Type A and Type B cells

Question 7

What are the difference between Type A and Type B cells?

Answer 7

Type A cells will replace the stem cells and Type B cells will go on to produce spermatozoa.

Question 8

What does a single type B spermatozoa produce?

Answer 8

It undergoes a series of mitotic divisions to produce (usually 64) primary spermatocytes which are linked together by cytoplasmic bridges

Question 9

What happens to the connected spermatocytes?

Answer 9

They move in from the periphery of the tubules towards the lumen and being the meiotic process, initially producing two haploid secondary spermatocytes and then four spermatids.

Question 10

What happens once the spermatozoa have been produced?

Answer 10

The cytoplasmic bridges break down and the sperm are released into the lumen to be washed down to the rete testis and onwards, by the fluid secreted from sertoli cells.

Question 11

What is spermatogenesis?

Answer 11

The remodelling process of spermatagonia to from spermatozoa.

Question 12

How long does spermatogenesis take?

Answer 12

70 days in total. – new groups of A1 apermatagonia arise every 16 days, so there are four processes occuring at once.

Question 13

Why are there multiple stages of spermatogenesis occuring at once?

Answer 13

The process begins at different times in different parts of the tubules.

Question 14

When are sperm fully matured?

Answer 14

As they pass through the epididymis– it is also the main storage area for sperm

Question 15

What happens during copulation?

Answer 15

The vas deferns contracts and causes sperm to be mixed with the other components of semen. This is known as emission.

Question 16

What are the components of semen?

Answer 16

– secretions of seminal vesicles (60% of volume)– secretions of prostate (20% of volume)– sperm– secretions of bulbo-urethral glands

Question 17

What is the spermatogenic cycle?

Answer 17

The development of a A1 Spermatogonia through to 256 sperms. The amount of time it takes for reappearance of the same stage of the cycle within a given segment of the tube.

Question 18

What is the spermatogenic wave?

Answer 18

Different parts of the tube begin the spermatogenic cycle at different times, in a ‘wave’, so the production of sperm is constant. The distance on the tube between parts that are in the same stage is the spermatogenic wave.

Question 19

What reproductive hormones are produced by the hypothalamus?

Answer 19

– Gonadotrophin Releasing Hormone (GnRH)– Prolactin Releasing Hormone (PRH)– Prolactin Inhibiting Hormone (PIH)

Question 20

What reproductive hormones are produced by the posterior pituitary gland?

Answer 20

Oxytocin

Question 21

What reproductive hormones are produced by the anterior pituitary gland?

Answer 21

– Follicle Stimulating Hormone (FSH)– Luteinising Hormone (LH)– Prolactin

Question 22

What reproductive hormones are produced by the testes?

Answer 22

– Testosterone– Inhibin– Mullerian Inhibiting Hormone (MIH)

Question 23

What reproductive hormones are produced by the ovaries?

Answer 23

– Oestrogen– Progesterone– Inhibin

Question 24

What reproductive hormones are produced by the placenta?

Answer 24

– Human Chorionic Gonadotrophin (hCG)– Human Placental Lactogen (hPL)– Oestrogen– Progesterone

Question 25

Describe the structure of the testes

Answer 25

Are male gonads which are paired, ovoid structures– produce spermatozoa and male hormones– are suspended in the scrotum by the spermatic cords

Question 26

Describe the tunica vaginalis

Answer 26

Have two layer of tunica vaginalis which cover the surface– visceral layer attaches everywhere except the epididymis and where the spermatic cord attaches to the testes– parietal layer lines the internal spermatic fascia and it extends onto the distal part of the spermatic cord. – have fluid between the two layers allowing for movement of the testes in the scrotum

Question 27

Describe the outer layer of the testes

Answer 27

Is tough and fibrousIs known as the tunica albuginea– thickens into a ridge on posterior lateral side known as the mediastinum of the testis– fibrous septums extend form this ridge in between the seminiferous tubules

Question 28

What are sertoli cells?

Answer 28

Are found in the seminiferous tubules and this is where spermatozoa development takes place.

Question 29

What are Leydig/interstitial cells?

Answer 29

Cells which are found in the interstitial tissue which secrete testosterone.

Question 30

Describe the vas deferens

Answer 30

Is a continuation of the epididymis and it has quite thick muscular walls and a small lumen. These muscles in the wall contract during copulation which forces sperm along the tube, mixing it with the other components of ejaculate.

Question 31

Describe seminal vesicles

Answer 31

Secrete the thick alkaline fluid which is rich in fructose and a coagulating agent. It makes up 60% of the volume of semen. The duct of the seminal gland joins the ductus deferens to form the ejaculatory duct.

Question 32

What are the bulbourethral glands?

Answer 32

Two pea sized glands which lie posterior and laterally to the intermediate part of the urethra. They are mostly embedded in the external urethral sphincter. The ducts of these glands open into the proximal part of the spongy urethra in the bulb of the penis.

Question 33

What do the bulbourethral glands secrete?

Answer 33

They secrete a mucus like substance which enter the urethra during sexual arousal.