The Male Reproductive System

Male Reproductive System

Epididymis

The Testes (male gonads - Primary sex organs)

Produce sperms Produce sex hormones Found in a sac called the scrotum Suspended outside of the body cavity for temperature reduction Testes wall made of fibrous connective tissue (Divides the testes into lobules (Chambers) Inside the chambers are long tubules (70 cm) called the Seminiferous tubules,this is the actual site for spermatogenesis (manufacturing sperms). Interstitial cells secrete androgens “testosterone”

Diagram of a Testis

Testis Anatomy

Spermatogenesis –Sperm Developmenthttp://highered.mcgraw-hill.com/novella/MixQuizProcessingServlet

• Sperms cells are derived from undifferentiated cells called SPERMATOGONIA (sing. Spermatogonium), which lie just on the inside wall of a tubule and divide mitotically, always producing new spermatogonia.

• Some newly formed spermatogonia move away from the wall to increase in size and become primary spermatocytes, which divide by meiosis I (reduction division) to give 2 secondary spermatocytes, each with 23 chromosomes.

• Secondary spermatocytes divide by meiosis II to produce 4 spermatids, also with 23 chromosomes, but each only having one chromatid.

https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__how_meiosis_works.html

• Spermatids then differentiate into sperms (spermatozoa)

• Also present in the tubules are the Sertoli cells, which support, nourish and regulate the spermatogenic cells.

The Seminiferous Tubule

The Seminiferous Tubule

What is the main function of Spermatogonia? To produce sperms

What is the main function of Sertoli cells? To provide nurishment for the spermatids

(maturing sperms) Secrete inhibin to inhibit the production of

FSH

What is the main function of the interstitial cells of Leydig? To produce androgens (Testosterone)

Epididymuso Stores sperm as they mature

Seminal Vesicleso 65% of seminal fluid, fructose rich to provide energy to sperms.

Cowper’s Gland (aka: Bulbourethral gland)o Pea-sized organs, lie posterior to the prostate on either sides

of the urethra, produces alkaline fluid to neutralize urethral urine.

o Contributes to seminal fluid (2%)

Prostate Glando A single dough-nut shaped gland that surrounds the upper

portion of the urethra just below the bladder.

o Produce prostaglandins (hormones that cause the contractions of the vagina to help move sperms)

o Helps produce seminal fluid (30%)

Urethra

o Conducts sperm out of the body

Ductus Vas Deferens

o Conducts and stores sperms

Penis

o Serves as an organ of copulation (sexual intercourse)

Name the structure that is a common path for urine and semen? The Urethra

Which structure functions as a storage and maturation site for sperms? The epididymis

Name the acessory glands of the male reproductive system? The seminal vesicles (a pair) The bulbourethral (aka: Cowper's gl.) (a pair) The prostate (single doughnut shaped)

Path of Sperms

1. Formed in the seminiferous tubules of the testes

2. Mature and store in the epididymus

3. Store in the Vas Deferens as well

4. Enter the urethra just prior to ejaculation

5. Accessory glands (prostate, Cowper’s gland, and seminal vesicle) add secretions to semen.

6. Semen including sperms exit through the penis.

Put the following structures in the appropriate order according to the path of sperms:

Seminiferous tubulesEpididymisDuctus deferensUrethra

1.

2.

3.

4.

Seminal Fluid

SOURCES:

1. Seminal Vesicle

2. Prostate Gland

3. Cowper’s Gland

Semen composition

Seminal Fluid Functions:

1. Produce slightly basic pH 7.5 preferred pH of sperm (Basic) to counteract the acidity level of the vagina.

2. Provides fructose for energy for sperm

3. Contains prostaglandins – chemicals which cause the uterus to contract.

4. Aids in the movement of the sperm towards the egg.

5. Lubrication

Sperm Parts

Head:

o 23 chromosomeso Acrosome attached- type of Lysosome- Attached to nucleus- Contains hydrolytic enzymes- Digests a hole in outer layer of egg so sperm can penetrate.

Middle Piece:

o Contains mitochondria – for energy

Tail (Flagellum):

o 9 + 2 microtubules arrangement – Used for locomotion

Most flagella, like cilia, have a characteristic “9+2” microtubule structure, i.e., two central singlet microtubules are encircled by nine outer doublet microtubules.

Crossection of a flagellum

1. Spermatogenesis occurs in the

A) epididymis.

B) seminiferous tubules.

C) prostate gland.

D) vas deferens.

E) seminal vesicle.

2.Which of the following is a correct sequence of cells in spermatogenesis?

A) spermatogonium -> primary spermatocyte -> secondary spermatocyte

B) spermatogonium -> secondary spermatocyte -> primary spermatocyte

C) primary spermatocyte -> secondary spermatocyte

-> spermatogonium

D) primary spermatocyte -> spermatogonium -> secondary spermatocyte

E) none of the above

3.During spermatogenesis, which of the following cells is the first to become haploid?

A) primary spermatocyte

B) secondary spermatocyte

C) sperm cells

D) spermatid

E) spermatogonium

4.Meiosis II of spermatogenesis results in the formation of secondary spermatocytes.

A) True

B) False

5.During spermatogenesis, spermatids differentiate into spermatozoa....

A) True

B) False

The correct answer for each question is indicated by a This is the correct answer..

1 Spermatogenesis occurs in the

A) epididymis.

B) seminiferous tubules. This is the correct answer.

C) prostate gland.

D) vas deferens.

E) seminal vesicle.

2 Which of the following is a correct sequence of cells in spermatogenesis?

A) spermatogonium -> primary spermatocyte -> secondary spermatocyte This is the correct answer.

B) spermatogonium -> secondary spermatocyte -> primary spermatocyte

C) primary spermatocyte -> secondary spermatocyte -> spermatogonium

D) primary spermatocyte -> spermatogonium -> secondary spermatocyte

E) none of the above

3 During spermatogenesis, which of the following cells is the first to become haploid?

A) primary spermatocyte

B) secondary spermatocyte This is the correct answer.

C) sperm cells

D) spermatid

E) spermatogonium

4 Meiosis II of spermatogenesis results in the formation of secondary spermatocytes.

A) True

B) False This is the correct answer.

5 During spermatogenesis, spermatids differentiate into spermatozoa.

A) True This is the correct answer.

B) False

Functions of Testosterone

1. Essential for development of primary sex organs.2. Essential for the development of sperms- Spermatogenic cells take up testosterone which stimulate their activity.3. Increase testosterone concentration at puberty causes maturation of Penis and testes.4. Secondary Sex Characteristicso facial hairo larynx expands (voice changes)o armpit hairo Increase muscular strengtho pubic hairo aggressiono oil and sweat glands secretions (=Stink)o sex driveNOTE: Side effect is baldness if genetically predisposed.

Hormonal Control of Testosterone

Hypothalamus releases GnRH (Gonadotropic releasing hormone)GnRH causes anterior pituitary to release 2 gonadotropic hormones:

o FSH (Follicle stimulating hormone)- Promotes spermatogenesis in the siminiferous tubules

o LH (Leutenizing Hormone)- Promotes production of testosterone in interstitial cells.

Hormonal Control of Testosterone

NEGATIVE FEEDBACK

o Increase testosterone concentration in the blood causes the anterior pituitaryto make less LH, therefore less testosterone is produced.

o Decrease testosterone concentration in the blood causes the anteriorpituitary to make more LH and therefore more testosterone is produced.

o Increase concentration of stored sperm causes an increase in production of inhibin (from Sertoli cells) and decreases production of FSH, therefore production of sperm decreases.

o Decrease concentration of stored sperm causes a decrease in production of inhibin and more FSH, therefore more sperm is produced.