Male Reproductive System

Structure and Functions of the Male Reproductive System

By the end of this session students are expected to be able to:

Define Male Reproductive System

• Explain the Composition of Male Reproductive System
• Describe Structure and Functions of the Male Reproductive System

Explain the Process of Spermatogenesis

Composition of Male Reproductive System

What is the composition of male reproductive system?

Male Reproductive System

Male reproductive system: Is the genital system, reproductive system organs and tissues involved in the production and maturation of gametes and in their union and subsequent development as offspring.

The male reproductive system consists of the testes and a series of ducts and glands.

Male Reproductive System

Sperm are produced in the testes by a process of spermatogenesis and are transported through the reproductive ducts: epididymis, ductus deferens, ejaculatory duct, and urethra

The reproductive glands produce secretions that become part of semen, the fluid that is ejaculated from the urethra.

These glands are the seminal vesicles, prostate gland, and bulbourethral glands.

Structures and Functions of Male Reproductive System

What are the structures and functions of the male reproductive system?

Structures of the male reproductive system

• Testes
• Epididymis
• Dactus deferens (vas deferens)

Ejaculatory ducts

Seminal vesicles

• Prostate gland
• Bulbourethral (Cowper‘s) glands

Urethra-penis

Functions of the male reproductive system

• Testes
• The testes are located in the scrotum, a sac of skin between the upper thighs.
• Internally is divided in to lobes

Each lobe contains several seminiferous tubules where spermatogenesis takes place.

Among the produced spermatogonia are Sertoli cells which produce inhibin hormone when stimulated by testosterone

Male Reproductive System

Between the loops of the seminiferous tubules are interstitial cells called Leydig cells which produce testosterone when stimulated by luteinizing hormone from anterior pituitary gland Testosterone is responsible for maturation of sperm and secondary male characteristics.

Epididymis

• It is a tube about 6m long that is coiled in the posterior surface of each testis.

Within it the sperm complete the maturation and their flagella become functional.

Smooth muscle of the wall of epididymis propels the sperm to dactus deferens

Dactus deferens (vas deferens)

Extends from the epididymis in the scrotum on its own side into the abdominal cavity through the inguinal canal

Male Reproductive System

Spermatic cord is a connective tissue sheath that contains the ductus deferens, testicular blood vessels (arteries+veins), and nerves

Inguinal canal is a natural weak spot where most of hernia is formed in men.

The smooth muscle layer of the ductus deferens contracts in waves of peristalsis as part of ejaculation

Ejaculatory ducts

Each of the two ejaculatory ducts receives sperm from the ductus deferens and the secretion of the seminal vesicle on its own side.

Both ejaculatory ducts empty into the single urethra

Seminal vesicles

The paired seminal vesicles are posterior to the urinary bladder

Their secretion contains fructose to provide an energy source for sperm and is alkaline to enhance sperm motility.

The duct of each seminal vesicle joins the ductus deferens on that side to form the ejaculation duct

Prostate gland

• A muscular gland just below the urinary bladder

It surrounds the first inch of the urethra as it emerges from the bladder

The glandular tissue of the prostate secretes an alkaline fluid that helps maintain sperm motility.

The smooth muscle of the prostate gland contracts during ejaculation to contribute to the expulsion of semen from the urethra

Bulbourethral (Cowper‘s) glands

They are located below the prostate gland and empties to the urethra Their alkaline secretion coats the interior of the urethra just before ejaculation, which neutralizes any acidic urine that might be present.

Urethra-penis

The urethra is the last of the ducts through which semen travels, and its longest portion is enclosed within the penis.

Male Reproductive System

The penis is an external genital organ; its distal end is called the glans penis and is covered with a fold of skin called the prepuce or foreskin which is removed by surgical procedure of circumcision

Male Reproductive System

Within the penis are three masses of cavernous (erectile) tissue by which the flow of blood to these masses through arteries cause penile erection.

Spermatogenesis

It is the process of meiosis as it takes place in the testes, the site of sperm production.

Within each testis are seminiferous tubules that contain spermatogonia, which are stem cells that generate sperm.

Male Reproductive System

A spermatogonium divides by mitosis to form two cells, one of which will remain in place as a stem cell, while the other differentiates (specializes) to become a primary spermatocyte that will undergo meiosis.

Gamete formation is regulated by hormones

Male Reproductive System

Follicle-stimulating hormone (FSH) from the anterior pituitary gland initiates sperm production, and testosterone, secreted by the testes when stimulated by luteinizing hormone (LH) from the anterior pituitary, promotes the maturation of sperm.

Inhibin, also produced by the testes, decreases the secretion of FSH

For each primary spermatocyte that undergoes meiosis, four functional sperm cells are produced.

Sperm production begins at puberty (10 to 14years of age), and millions of sperm are formed each day in the testes.

Although sperm production diminishes with advancing age, there is usually no complete cessation

The sperm cell and semen

• A sperm cell consists of several parts

The head contains the 23 chromosomes.

On the tip of the head is the acrosome, which is similar to a lysosome and contains enzymes to digest the membrane of an egg cell.

Within the middle piece are mitochondria that produce ATP.

The flagellum provides motility, the capability of the sperm cell to move.

It is the beating of the flagellum that requires energy from ATP.

Sperm from the seminiferous tubules enter a tubular network called the rete testis, and then enter the epididymis, the first of the reproductive ducts.

Semen consists of sperm and the secretions of the seminal vesicles, prostate gland, and bulbourethral glands

Its average pH is about 7.4.

During ejaculation, approximately 2 to 4 mL of semen is expelled.

Each millilitre of semen contains about 100 million sperm cells.

Key Points

The male reproductive system consists of the testes and a series of ducts and glands Testes produces testosterone hormone which is responsible for maturation of sperm and secondary male characteristics The process of spermatogenesis is controlled by hormones and the sperm cell produced aid transported by the reproductive ducts which are epididymis, ductus deferens, ejaculatory duct, and urethra

Evaluation

• Define male reproductive system
• What are the composition of male reproductive system
• What are the structure of the male reproductive system

What are the process of spermatogenesis