M6(3) Male Reproductive System (Testes, External Genitalia, Ducts, Glands)

Male Reproductive Organs

Includes

• Testes (primary sex organ / gonads)

• Accessory Structures

Accessory Structures

Includes

a) External Genitalia

b) Duct System

c) Accessory Glands

External Genitalia

Includes

• Scrotum

• Penis

Scrotum

Sac of skin that hangs outside at the root of the penis, contains a pair of oval testes

• Encloses and protects testes

• Divided by midline septum, which provides a compartment for each testes

Scrotum Purpose

Its location allows testes to produce sperm at a temperature of around 3°C cooler than body temp (34-35°C)

• Normal body temp of ~37°C is not optimal for sperm production

Scrotum and Temperature

When it is cold, the testes are pulled closer for warmth. When this occurs:

• Scrotal skin wrinkles, decreasing its SA and increasing its thickness to reduce heat loss

Scrotal Muscle and Temperature

Two sets of muscles help to maintain the intra-scrotal temperature

• Dartos Muscle

• Cremaster Muscles

Dartos Muscle

Layer of smooth muscle in the superficial fascia

• Wrinkles scrotal skin

Cremaster Muscles

Bands of skeletal muscle that arise from the internal oblique muscles of the trunk

• Elevates the testes

Testis Structure

Regions called ‘lobules’ contain seminiferous tubules which is where sperm is made

• Seminiferous tubules connect to rete testis

• Rete testis connect to efferent ductules and enter the epididymis

• Epididymis connects to Ductus Deferens

Testicular Arteries

Branch from the abdominal aorta, supply the testes

Testicular Veins

Arises from a network called the pampiniform venous plexus (surrounds the portion of each testicular artery within the scrotum), drains the testes

• Cooler venous blood in each pampiniform plexus absorbs heat from the arterial blood, cooling it before it enters the testes

Spermatic Cord

The ductus deferens + A connective tissue sheath that encloses

• Nerve fibers

• Blood vessels

• Lymphatics

Duct System

Sperm/semen flows through

1. Epididymis

2. Ductus (vas) deferens

3. Ejaculatory Duct

4. Urethra

Epididymis

Comma-shaped organ, site of sperm maturation / storage

• Head of epididymis contains efferent ductules that empties to the duct of the epididymis

Pseudostratified Epithelium

Type of epithelial tissue that looks multilayered but is actually a single layer of cells

Epididymis Mucosa

Has pseudostratified epithelium

• Some pseudostratified epithelial cells have stereocilia, which

  • absorb excess testicular fluid (concentrates sperm)

  • pass nutrients to stored sperm

Epididymis and Storage

Sperm can be stored in the epididymis for several months

• If held longer, epithelial cells of the epididymis eventually phagocytize them

Epididymis and Ejaculation

Sperm are ejaculated from the epididymis, not the testes

• During ejaculation, smooth muscle in the ducts of the epididymis contracts which expels sperm to the ductus deferens

Ductus Deferens

Transports sperm during ejaculation

• At its end, it expands to form the ampulla of the ductus deferens

Ductus Deferens Mucosa

Has pseudostratified epithelium

• Its muscular layer is extremely thick

Ductus Deferens and Ejaculation

During ejaculation, its smooth muscle creates strong peristaltic waves that squeeze sperm forward along the tract and into the urethra

Ejaculatory Duct

The duct that comes directly after the ampulla of the ductus deferens joins with the seminal gland duct

• Each ejaculatory duct empties into the urethra

Vasectomy

A form of permanent birth control

• Small incision made into the scrotum

• Each ductus deferens is cauterized

• Sperm is still produced, but they can no longer reach the body exterior

  • Instead, they deteriorate and are phagocytized

Urethra

Terminal portion of the male duct system

• Transports both urine and semen

Urethra Regions

Contains 3 regions:

• Prostatic Urethra

• Intermediate / Membranous Urethra

• Spongy Urethra

Prostatic Urethra

Surrounded by the prostate

Intermediate / Membranous Urethra

In the urogenital diaphragm

Spongy Urethra

Runs through the penis and opens to the outside at the external urethral orifice

Urethra Mucosa

Contains scattered urethral glands that secrete lubricating mucus into the lumen just before ejaculation

Penis

Male copulatory organ that delivers sperm into the female reproductive tract

• Consists of root, body, and glans penis (enlarged tip)

Prepuce

Loose covering skin around the glans

• Foreskin

Penis Erectile Tissue

Sponge-like tissue that can fill with blood to create an erection

• Corpus Spongiosum

• Corpus Cavernosa

Corpus Spongiosum

Surrounds the urethra

• Expands distally, forming the glans

• Expands proximally forming a part of the root known as the ‘bulb of the penis’

Corpus Cavernosa

Makes up most of the penis

• Proximal end forms the ‘crus of the penis’