Bio100(Male reproductive system~A)

What is the primary function of the reproductive system?

The continuation of species.

What are the primary reproductive organs that produce the gametes?

Gonads.

What are the male gonads, and what do they produce?

Testes (singular = testis); they produce sperms.

What are the female gonads, and what do they produce?

A pair of ovaries; they produce ovum.

What is the condition called where both sexes are present in the same organism, such as in earthworms and snails?

Hermaphroditism.

In humans and most higher animals, how does reproduction occur?

Sexually, i.e., by mating.

What is a notable exception in the animal kingdom where organisms can produce offspring without mating?

Some species like insects.

The reproductive organs are broadly classified into what two categories?

1. Primary sex organs 2. Accessory sex organs.

What are the primary sex organs in males?

The testes (or gonads).

Name the four accessory sex organs in males.

1. Seminal vesicles 2. Prostate gland 3. Urethra 4. Penis.

The reproductive organs are anatomically classified into what two categories based on location?

External and Internal Genitalia.

What structures constitute the external genitalia in males?

The scrotum, penis, and urethra.

What structures constitute the internal genitalia in males?

The remaining sex organs (testes, epididymis, vas deferens, seminal vesicles, prostate, ejaculatory ducts).

What is the shape of the testes?

Oval or walnut-shaped bodies.

Where are the testes located?

Suspended in a sac-like structure called the scrotum.

What is the normal weight range of each testis?

15 to 19 g.

What are the approximate physical dimensions of a testis?

5 x 3 cm.

Each testis is made up of about how many coiled tubules?

About 900.

What are the coiled tubules inside the testis called, and what is their function?

Seminiferous tubules; they produce sperms.

The seminiferous tubules continue as what structure, which then forms the epididymis?

Vas efferens.

The epididymis continues as what structure?

The vas deferens.

What are three alternative names for the vas deferens?

Ductus deferens, spermatic deferens, or sperm duct.

Through what canal does the vas deferens extend into the abdominal cavity?

The inguinal canal.

What is the terminal portion of the vas deferens called?

The ampulla.

How is the ejaculatory duct formed?

The ampulla of the vas deferens joins the duct of the seminal vesicle of the same side.

Where does the ejaculatory duct open/empty into?

The prostatic part of the single urethra.

Name the three coverings that enclose each testis.

1. Tunica vasculosa 2. Tunica albuginea 3. Tunica vaginalis.

Describe the tunica vasculosa.

It is the innermost covering, made up of connective tissue, and is rich in blood vessels.

Describe the tunica albuginea.

It is the middle covering; a dense fibrous capsule.

Describe the tunica vaginalis.

It is the outermost closed cleft-like covering, formed by mesothelial cells.

What two layers make up the tunica vaginalis?

Visceral and parietal layers.

What allows the free movement of the testes within the tunica vaginalis?

The visceral and parietal layers glide on one another.

Which structure does the visceral layer of the tunica vaginalis adhere to?

The tunica albuginea.

Which structure does the parietal layer of the tunica vaginalis line?

The inner surface of the scrotum.

Which surfaces of the testes are covered by all three layers?

The anterior and lateral surfaces.

Which surface of the testis is covered by the tunica albuginea only?

The posterior surface.

What is the mediastinum of the testis?

A thickening of the tunica albuginea on the posterior surface of the testis.

What are the septula testis?

Connective tissue septa that radiate from the mediastinum and bind with the tunica albuginea at various points.

What is the function of the septula testis?

They divide the testis into a number of pyramidal lobules.

Where do the bases of the pyramidal lobules direct towards?

Towards the periphery.

Where do the apices of the pyramidal lobules direct towards?

Towards the mediastinum.

Do the septula testis form complete partitions between lobules?

No, the lobules anastomose with one another at many places.

Each testis has about how many lobules?

200 to 300 lobules.

Each lobule of the testis contains how many seminiferous tubules?

1 to 4 coiled tubules.

What surrounds the seminiferous tubules within the lobules?

Interlobular connective tissue.

What is the shape of the blind end of a seminiferous tubule?

It forms a single, double, or triple arch (it does not end bluntly).

The wall of the seminiferous tubule is formed by what three layers?

1. Outer capsule (tunica propria) 2. Thin homogeneous basement membrane 3. Complex stratified epithelium.

What tissue forms the outer capsule (tunica propria) of the seminiferous tubule?

Fibro-elastic connective tissue.

The complex stratified epithelium of the seminiferous tubule consists of what two types of cells?

i. Spermatogenic cells (germ cells) ii. Sertoli cells (supporting cells).

What are spermatogenic cells?

Precursor cells of spermatozoa.

Where are spermatogenic cells located?

In between Sertoli cells, arranged in an orderly manner in 4 to 8 layers.

What is the primitive stage of spermatogenic cells found in children called?

Spermatogonia.

When do spermatogonia begin to develop into sperms through different stages?

With the onset of puberty.

List the 4 stages of spermatogenic cells seen from the periphery to the lumen of the seminiferous tubules.

1. Spermatogonium 2. Primary spermatocyte 3. Secondary spermatocyte 4. Spermatid.

What is the rete testis?

A network of thin-walled channels present in the mediastinum.

What structures open into the rete testis?

All the seminiferous tubules.

What are the vas efferens?

8 to 15 tubules that arise from the rete testis.

What structure is formed by the vas efferens joining together?

The head of the epididymis.

Describe the epididymis.

An enormously convoluted tubule, with a length of about 4 meters.

Where does the epididymis begin?

At the head, where it receives vas efferens.

Where does the epididymis turn sharply upon itself to continue as the vas deferens?

At the caudal pole of the testis.

What are the interstitial cells of Leydig?

Hormone secreting cells of the testis, lying in between the seminiferous tubules.

What is the approximate length of each seminiferous tubule?

30 to 70 cm long.

What is the approximate diameter of a seminiferous tubule?

150 to 300 μ.

What are two alternative names for Sertoli cells?

Supporting cells or nurse cells.

Describe the structure of Sertoli cells.

Large and tall irregular columnar cells, extending from the basement membrane to the lumen of the seminiferous tubule.

How are germ cells attached to Sertoli cells?

By means of cytoplasmic connection.

Where are matured spermatozoa released?

Into the lumen of the seminiferous tubules.

What are the 3 general functions of Sertoli cells for the spermatogenic cells?

Support, protection, and nourishment.

List the 8 specific functions of Sertoli cells.

1. Support and nourish spermatogenic cells. 2. Secrete aromatase. 3. Secrete androgen-binding protein (ABP). 4. Secrete estrogen. 5. Secrete inhibin. 6. Secrete activin. 7. Secrete müllerian regression factor (MRF). 8. Form the blood-testes barrier.

What is the function of the enzyme aromatase secreted by Sertoli cells?

It converts androgens into estrogen.

What is the function of androgen-binding protein (ABP)?

It is essential for testosterone activity, especially during spermatogenesis.

What is the function of the estrogen secreted by Sertoli cells?

It is essential for spermatogenesis.

What is the function of inhibin?

It inhibits FSH release from the anterior pituitary.

What is the function of activin?

It increases FSH release (opposite action of inhibin).

What is the function of müllerian regression factor (MRF) in the fetus?

Responsible for the regression of the müllerian duct during sex differentiation.

What is another name for müllerian regression factor (MRF)?

Müllerian inhibiting substance (MIS).

What is the blood-testes barrier?

A mechanical barrier that separates blood from seminiferous tubules of the testes.

How is the blood-testes barrier formed?

By tight junctions between the adjacent Sertoli cells, near the basal membrane of the seminiferous tubule.

What are the two main functions of the blood-testes barrier?

1. Protection of seminiferous tubules 2. Prevention of autoimmune disorders.

How does the blood-testes barrier protect the seminiferous tubules?

By preventing the entry of toxic substances from the blood and fluid of the surrounding tissues into the lumen of the seminiferous tubules.

What types of substances are prevented from crossing the blood-testes barrier?

Large molecules including proteins, polysaccharides, cytotoxic substances, and medium-sized molecules like galactose.

What types of substances are permitted to cross the blood-testes barrier?

Nutritive substances essential for spermatogenesis, hormones necessary for spermatogenesis, and water.

How does the blood-testes barrier prevent autoimmune disorders?

It prevents the immune system of the body from recognizing the antigenic products of spermatogenesis from the testis into the blood.

What can cause damage to the blood-testes barrier?

Trauma or viral infections like mumps.

What is the consequence of a damaged blood-testes barrier?

The immune system is activated, resulting in the production of autoantibodies against sperms, leading to consequent sterility.

What are the two primary functions of the testes?

1. Gametogenic function (Spermatogenesis) 2. Endocrine function (Secretion of hormones).

Define spermatogenesis.

The process by which the male gametes called spermatozoa (sperms) are formed from the primitive spermatogenic cells (spermatogonia) in the testis.

How many days does it take for the formation of sperm from a primitive germ cell?

74 days.

Spermatogenesis occurs in what four stages?

1. Stage of proliferation 2. Stage of growth 3. Stage of maturation 4. Stage of transformation.

During the stage of proliferation, what is the chromosome number in each spermatogonium?

Diploid number (23 pairs or 46 chromosomes).

Of the 23 pairs of chromosomes in a spermatogonium, how many are autosomal and how many are sex chromosomes?

22 pairs are autosomal chromosomes and one pair are sex chromosomes (one X and one Y).

By what type of cell division do spermatogonia divide during the stage of proliferation?

Mitosis.

The last generation of spermatogonia enters the stage of growth as what specific cell type?

Primary spermatocyte.

During the stage of growth, what happens to the spermatogonia?

It migrates along with Sertoli cells towards the lumen and grows into a large cell (primary spermatocyte).

Is there a change in the number of chromosomes during the stage of growth?

No.

When does the stage of maturation begin?

After reaching the full size, each primary spermatocyte quickly undergoes meiotic or maturation division.

During the first phase of maturation, the primary spermatocyte divides into what?

Two secondary spermatocytes.

What type of division occurs in the first phase of maturation?

First meiotic division.

What is the significance of the first meiotic division in spermatogenesis?

Each secondary spermatocyte receives only the haploid or half the number of chromosomes (23 chromosomes).