M2 S2

Question 1

when will the testes descend into the scrotum in most males?

Answer 1

in the last months of fetal life (does not occur in some cases)

Question 2

what is cryptorchidism (2)

Answer 2

• occurs if the testes stay inside the body and don’t descend into the scrotum during adulthood
• can lead to infertility

Question 3

why is the location of the testes physiologically important? (4)

Answer 3

• important for spermatogenesis:
• temp within the scrotum averages several degrees Celsius less than normal body (core) temperature
• Descent of the testes into this cooler environment is essential, because spermatogenesis is temperature sensitive and cannot occur at normal body temperature.
• Therefore, an individual with cryptorchidism is unable to produce viable sperm.

Question 4

what happens when the testes are too cold for spermatogenesis?

Answer 4

the scrotal muscles (the cremaster muscle and the dartos muscle) contract to bring the testes closer to the body to gain heat.

Question 5

what happens when the testes are too hot for spermatogenesis?

Answer 5

the scrotal muscles relax to move the testes away from the body

Question 6

what does the majority of the testes consist of?

Answer 6

coiled seminiferous tubules in which sperm are produced

Question 7

what are Leydig cells? (2)

Answer 7

• produce and secrete testosterone
• also known as interstitial cells

Question 8

where the leydig cells found?

Answer 8

within the connective tissues between the seminiferous tubules

Question 9

what happens once testosterone is secreted by Leydig cells? (2)

Answer 9

• some testosterone enters the bloodstream and circulates to distant target cells.
• However, most of the testosterone enters the lumen of the seminiferous tubules where it supports sperm production

Question 10

testosterone effects before birth (2)

Answer 10

• causes masculinization of the reproductive tract and external genitalia
• causes the descent of the testes into the scrotum.

Question 11

testosterone effects on sex-specific tissues after birth (3)

Answer 11

(1) maintains the reproductive tract throughout adulthood
(2) promotes spermatogenesis
(3) promotes maturation of the reproductive system at puberty.

Question 12

testosterone other reproductive effects (2)

Answer 12

• Develops sex drive at puberty
• controls the secretion of gonadotropin hormone.

Question 13

testosterone effects on secondary sexual characteristics (3)

Answer 13

• Causes voice to deepen
• development of male pattern of body hair
• promotion of muscle growth (protein anabolism).

Question 14

testosterone non-reproductive actions (3)

Answer 14

• Promotes bone growth at puberty
• plays a role in the closing of the epiphyseal plates.
• May also induce aggressive behaviour.

Question 15

the majority of the seminiferous tubules are composed of two cell types:

Answer 15

germ cells and Sertoli cells

Question 16

what is spermatogenesis?

Answer 16

the process in which diploid (46 chromosomes) primordial germ cells are converted into motile sperm cells with a haploid (23 chromosomes) set of chromosomes

Question 17

what are primordial germ cells called and where are they located?

Answer 17

called spermatogonia and they are located in the outermost layer of the seminiferous tubule

Question 18

spermatogenesis: mitotic proliferation (4)

Answer 18

• spermatogonia divide by mitosis to create more spermatogonia.
• After each division, one of the new cells stays in the outer layer, while the other moves toward the center of the tubule.
• This cell that moves inward will divide two more times, creating four identical primary spermatocytes.
• These spermatocytes then enter a resting phase, getting ready for the next step, which is meiosis I, where they will begin to develop into sperm

Question 19

spermatogenesis: meiosis (4)

Answer 19

• Each primary spermatocyte divides into two secondary spermatocytes, each with 23 double-stranded chromosomes.
• Then, during meiosis II, each secondary spermatocyte divides into two spermatids, each with 23 single-stranded chromosomes.
• At this stage, no more divisions occur.
• So, from each spermatogonium, a total of 16 spermatids can be produced after all the divisions are complete

Question 20

spermatogenesis: packaging

Answer 20

During this phase, the cells are stripped down of all non-essentials such as the cytosol and most organelles

Question 21

4 parts of a mature spermatozoa

Answer 21

1. head
2. acrosome
3. midpiece
4. tail (flagellum)

Question 22

head

Answer 22

Consists of the nucleus

Question 23

acrosome

Answer 23

Enzyme-packed vesicle at the tip of the head that is needed to penetrate the ovum

Question 24

midpiece

Answer 24

Packed full of mitochondria to provide energy for locomotion

Question 25

tail (flagellum)

Answer 25

Movement of this provides propulsion ( requires lots of ATP).

Question 26

sertoli cells (3)

Answer 26

- A single layer of Sertoli cells makes up the walls of the seminiferous tubules - Although they are connected to their neighbours by tight junctions, during the process of spermatogenesis, developing sperm cells pass between them as they migrate towards the lumen. - Developing sperm cells are essentially engulfed in the Sertoli cells as they migrate towards the lumen where the sperm head remains embedded until it is mature

Question 27

6 functions of sertoli cells for spermatogenesis

Answer 27

1. Blood-testes barrier: The tight junctions between Sertoli cells form a barrier that controls what substances can reach the developing sperm. 2. nourish sperm cells (supporting growth and maturation) 3. help absorb the extra cytoplasm from developing sperm cells and remove any defective germ cells 4. secrete fluid into the seminiferous tubules that helps flush sperm into the epididymis, where they are stored 5. Secrete androgen-binding protein that helps to concentrate testosterone in the lumen 6. the site where testosterone and FSH act to regulate spermatogenesis

Question 28

what are the testes under control of?

Answer 28

LH and FSH

Question 29

LH

Answer 29

stimulates the Leydig cells to secrete testosterone

Question 30

FSH

Answer 30

acts on the Sertoli cells to stimulate spermatogenesis and to secrete inhibin

Question 31

negative-feedback pathway of testosterone (2)

Answer 31

- at the level of the hypothalamus to decrease GnRH release and at the anterior pituitary to decrease LH and FSH release. - the inhibin released by the Sertoli cells feeds back to the anterior pituitary to decrease F S H release

Question 32

male reproductive tract consists of: (2)

Answer 32

1. Epididymis and Ductus Deferens 2. Male Accessory Sex Glands

Question 33

Epididymis and Ductus Deferens (4)

Answer 33

- After sperm are made in the seminiferous tubules, they move into the epididymis, a long, tightly coiled tube that's about 5 meters long. - At first, sperm in the epididymis can't move because the environment there has a low pH. - The epididymis connects to the ductus deferens, a tube that carries sperm from each testis to the urethra. - Sperm can be stored in the epididymis for several months.

Question 34

3 main accessory sex glands that produce secretions making up most of semen:

Answer 34

1. seminal vesicles 2. prostate gland 3. bulbourethral glands

Question 35

what are the seminal vesicles?

Answer 35

The seminal vesicles are two glands, one connected to each ductus deferens just before the urethra

Question 36

functions of the seminal vesicles (4)

Answer 36

1. Produce the bulk of semen (They secrete the majority of the fluid that makes up semen) 2. Supply fructose: This sugar provides energy for sperm, helping them swim and survive 3. Secrete prostaglandins: These chemicals cause smooth muscle contractions in both the male and female reproductive tracts, aiding sperm movement. 4. Secrete fibrinogen: This protein helps semen to become more solid or gel-like after ejaculation, which can help the sperm stay in place in the female reproductive tract

Question 37

what is the prostate gland?

Answer 37

a large gland that surrounds the ejaculatory ducts and urethra

Question 38

2 functions of the prostate gland (2)

Answer 38

1. To secrete an alkaline fluid to neutralize the acidic environment of the vagina 2. Secretes clotting enzymes: These enzymes act on the fibrinogen from the seminal vesicles to produce fibrin. The fibrin helps clot the semen, keeping it inside the female reproductive tract longer

Question 39

what are the bulbourethral glands? (2)

Answer 39

- also known as Cowper's glands - a pair of glands located on either side of the urethra, just before it enters the penis

Question 40

function of the bulbourethral glands

Answer 40

They secrete a clear substance during sexual arousal and this fluid helps to lubricate the urethra for sperm to pass through