Male Reproductive System

• The male reproductive system includes the testes, ducts, and glands.
• The male's reproductive role is to produce viable sperm and deliver it to the female reproductive system.

Site of Spermatogenesis

• Spermatogenesis occurs in the testes.

Pathway of Spermatozoa

• Spermatozoa travels through the epididymis, ductus deferens (vas deferens), and ejaculatory duct.

Accessory Organs/Glands

• Seminal vesicles, prostate gland, and bulbourethral glands are accessory glands.

Testes

• The testes (singular: testis) are paired, oval glands that descend into the scrotum.
• Sperm is produced in the testes throughout a male's life.
• At the onset of puberty, the testes produce testosterone, the male sex hormone.
• Testosterone stimulates and promotes the growth of secondary sex characteristics in men.

Seminiferous Tubules

• Seminiferous tubules contain spermatogonia, which are stem cells involved in spermatogenesis.
• Seminiferous tubules contain sustentacular cells, which sustain and promote sperm development.

Spermatogenesis

• Spermatogenesis includes spermatocytogenesis and spermiogenesis.
• Spermatogonium becomes a spermatocyte, which becomes 4 spermatids, which become 4 spermatozoa.
• Spermatogenesis literally means the formation of sperm.
• Spermatogenesis occurs in the seminiferous tubules of the testes and takes 65 to 70 days.
• Spermatogenesis begins with one cell, which becomes two, and finally four.

Stages of Sperm Development

• Spermatogonia are located on the basal lamina undergo mitosis.
• Primary spermatocytes undergo the 1st meiotic division.
• Secondary spermatocytes undergo the 2nd meiotic division.
• Spermatids are haploid, with 4 created from each spermatocyte.

Sperm Cells

• Sperm cells are haploid cells produced when secondary spermatocytes divide.
• A mature sperm has a head, neck, and tail.
• Sperm from the lumen of seminiferous tubules enters the duct of the epididymis.
• Sperm takes 20 days to travel through the 4-6 meter long tortuous duct.
• If ejaculation does not occur, sperm will die and degenerate.

Abnormal Sperm

• Abnormal sperm are seen more frequently than abnormal oocytes
• Abnormal sperm characteristics include two heads, two tails, dwarfism, or giantism.

Epididymis

• The epididymis is a comma-shaped organ on top of the testicle that stores and propels sperm toward the urethra during ejaculation.
• Sperm moves from the epididymis into the vas deferens (ductus deferens).
• The epididymis is an elongated tubule with head, body, and tail regions.
• The epididymis stores and protects spermatozoa, and facilitates the functional maturation of spermatozoa.

Semen

• During its trip the sperm picks up fluids from glands, vital for keeping sperm cells alive and motile.
• When sperm and fluid join, it is then called semen.

Contents of Semen

• A typical ejaculate is 2-5 ml of fluid.
• Ejaculate contains between 20 to 120 million spermatozoa per ml.
• Seminal fluid has a distinct ionic and nutritive glandular secretion.

Accessory Glands

• The glands of the male reproductive system include the seminal vesicles, prostate gland, and bulbourethral glands.

Seminal Vesicles

• Seminal vesicles are active secretory glands.
• Seminal vesicles contribute approximately 60% of the total volume of semen.
• Seminal vesicle secretions contain fructose, prostaglandins, and fibrinogen.

Prostate Gland

• The prostate gland secretes prostate fluid.

Bulbourethral Glands (Cowper's Glands)

• Bulbourethral glands secrete alkaline mucus with lubricating properties.

Hormonal Regulation of Testicular Function

• The hypothalamus releases gonadotropin-releasing hormone (GnRH).
• GnRH stimulates the anterior pituitary to secrete FSH and LH.
• FSH acts on the sustentacular cells.
• LH stimulates interstitial cells to release testosterone.

Testosterone

• Testosterone is a male sex hormone (androgen) synthesized from cholesterol.
• Testosterone is produced by Leydig cells of the testes.
• In the blood, testosterone is transported in bound form with Sex Hormone Binding Globulin.
• LH increases its secretion.

Effects of Testosterone

• Testosterone causes the descent of the testes and the development of male reproductive organs.
• Testosterone leads to the development of secondary sex characteristics including baldness, deep voice, hair distribution, increased muscle mass (protein deposition), bone growth, and effects on sebaceous glands (acne).