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Reproductive systems - a. Male reproductive system

35 important questions on Reproductive systems - a. Male reproductive system

What is a difference between the result of mitosis and meiosis, as regards to phenotypic consequences?

- The cells that result from mitosis are identical to each other and to the mother cell
- The cells that result from meiosis are not identical to each other and to the mother cell

How many steps are there in the production of germ cells?

Two rounds of cell division take place.

What occurs in the first steps, and what is the result of this?

Recombination, the result is 4 different copies of each chromosome.

What are the four ways in which genetic variation is increased in the zygote that eventually is made?

Fusion of maternal and paternal DNA in the gametes (each gamete contains 23 chromosomes)
Segregation and independent assortment
Recombination: crossing over during late prophase
Random fertilization

What does segregation and independent assortment refer to?

To the random distribution of the chromosomes from the stem cell and segregation to two daughter cells in meiosis I
The alleles on different pairs of chromosomes are again distributed independently in meiosis II.

What is the number of different types of gametes that a man can produce?

2ˆ23 = 8.5 million possibilities.

Where within the seminiferous tubule do the spermatogonia develop into spermatozoa ?

As they develop, they go from the outside ('wall') to the inside (lumen) of the tubule.

How does the development from spermatogonia into spermatozoa go?

Spermatogonia
↓
(division by mitosis, 1 goes into:)
primary spermatocytes
↓
(division by meiosis)
secondary spermatocytes
↓
spermatids
↓
spermatozoa

How is the development from spermatids into spermatozoa called?

Spermiogenesis (= physical maturation).

How is the whole process of sperm cell formation called?

Spermatogenesis.

What happens with the spermatozoa, after they have been produced?

They lose contact with the wall of the seminiferous tubule and enter the fluid in the lumen.

How is the acrosomal vesicle formed, and what will it eventually become?

- It is formed by the fusion of a peroxisome and the Golgi apparatus (which was initially present in the spermatid)
- It will become the acrosomal cap of the mature sperm cell.

What is the role of the sustentacular cells in the spermiogenesis?

They phagocytose the shed cytoplasm
They provide nutrients.

What does the mature spermatozoon lack?

ER
Golgi apparatus
Lysosomes
Peroxisomes
Inclusions

How does the spermatozoon get nutrients?

It absorbs nutrients (fructose) from the surrounding fluid

What does the acrosomal cap contain?

Enzymes essential for fertilization.

What does the tail consist of?

A fibrous sheeth of flagellum.

What are the 6 major functions of the sustentacular cells?

Remain blood-testis barrier
Support mitosis and meiosis
Support spermiogenesis
Secrete inhibin
Secrete androgen-binding protein
Secrete Müllerian-inhibiting factor

How can the sustentacular cells play a role in maintaining the blood-testis barrier?

They are joined by tight junctions.

What is the role of the hypothalamus in the male reproductive system?

It releases GnRH (Gonadotropin Releasing Hormone)

What does LH stimulate?

The interstitial cells (in the seminiferous tubule), which stimulate the secretion of testosterone.

What do the sustentacular cells do?

Stimulate synthesis of ABP (androgen-binding protein) and spermatogenesis and spermiogenesis
Stimulate synthesis of inhibin, which inhibits FSH secretion

What does androgen binding protein (ABP) do?

It binds androgens, mainly testosterone, in seminiferous tubule fluid, which elevates androgen levels in the seminiferous tubule and stimulates spermiogenesis.

What type of cells secrete Müllerian-Inhibiting Factor (MIF), and what does MIF do?

- MIF is secreted by sustentacular cells in developing testes
- MIF causes regression of the fetal Müllerian ducts.

To what does inadequate MIF production during fetal development lead?

Retention of ducts and failure of testes to descend into scrotum.

What is functional maturation?

The spermatozoa produced in the seminiferous tubules are not capable of fertilization, to become motile and functional they need to undergo capacitation.

When do spermatozoa become motile?

When they are mixed with the secretions of the seminal vesicles.

When do spermatozoa become capable of fertilization?

When they are exposed to the female reproductive tract, where they also become more motile.

Which two things are vital for capacitation in the female reproductive tract?

The Ca concentration has to be regulated
The membrane cholesterol of the sperm cells has to be lost

What are GPI-anchored proteins and what happens with them?

- They are inhibitors of sperm-egg binding
- They are lost from the membrane of the sperm cell during capacitation.

What cleaves the GPI-anchored proteins from the membranes?

ACE.

What are the four major functions of the male glands?

1. Activating spermatozoa
2. Providing nutrients spermatozoa need for motility
3. Propelling spermatozoa and fluids along reproductive tract (mainly by peristaltic contractions)
4. Producing buffers: to counteract acidity of urethral and vaginal environments.

What do the seminal vesicles secrete?

The secretions contain fructose, prostaglandins, and fibrinogen (60% of total volume of semen).

What does the prostate gland secrete?

Acidic prostate fluid.

What do the bulbourethral glands secrete?

Alkaline mucus with lubricating properties.

The question on the page originate from the summary of the following study material:

Lectures Human Development

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