The Reproductive System
- The testes produce both sperm as exocrine glands
and the male sex hormones as endocrine glands.^
- The scrotal sac will elevate or descend on exposure to
changes in temperature to ensure sperm survival.
The Testes
- Each testis is covered by a capsule of connective
tissue called the tunica albuginea, which extends
inward to form a series of compartments called
lobules.^
- Each lobule contains one to three convoluted semi-
niferous tubules in which spermatogenesis occurs.^
- Spermatogenesis begins as immature sperm cells,
called spermatogonia, which divide by mitosis to
form primary spermatocytes.^
- Primary spermatocytes divide by meiosis to form
secondary spermatocytes that develop into
spermatids.^
- Spermatids develop into mature sperm cells or
spermatozoa.^
- Sertoli cells supply nutrients to the developing
sperm cells.^
- In the lobules, interstitial cells of Leydig produce the
male sex hormone testosterone.
The Anatomy of the Spermatoza
- Three hundred million spermatozoa are produced
daily and can live up to 48 hours in the female
reproductive tract.^
- Each spermatozoa consists of a head, which con-tains
the nuclear genetic material and an acrosome
containing enzymes, a middle piece or collar con-
taining mitochondria, and a tail that is a flagellum to
propel the sperm cell.
The Functions of Testosterone
- It controls the development, growth, and mainte-
nance of the male sex organs.^
- It stimulates muscle buildup and bone
development.^
3.^ It causes sperm maturation.^
4. It causes enlargement of the thyroid cartilage, or
Adam’s apple, and thickening of the vocal cords,
resulting in a deep voice.^
- It produces body hair patterns, like facial and chest
hair, and a receding hairline.^
- It stimulates aggressive behavior.
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The Ducts of the System- The formed sperm cells move from the convoluted
seminiferous tubules of the testis to the straight tu-
bules at the top of the lobule.^ - They then move to a network of ducts in the testis
called the rete testis.^ - They move out of the testis through coiled efferent
ducts that connect to a single tube called the ductus
epididymis.^ - The tightly coiled epididymis is located on the pos-
terior border of a testis.^ - As the epididymis straightens, it is called the ductus
deferens or vas deferens. It is 18 inches long.^ - The vas deferens is enclosed in a sheath called the
spermatic cord. It empties into its ejaculatory duct.^ - Each ejaculatory duct ejects the spermatozoa into
the single urethra.^ - The urethra is the terminal duct of the system. It is
about 8 inches long and is a common passageway
for sperm and urine.^ - The urethra passes through the prostate gland, the
urogenital diaphragm, and the penis. It is divided
into three parts.^ - The prostatic urethra is surrounded by the prostate
and is about 1 inch long; the membranous urethra is
about 1/2 inch long and connects to the penis; the
spongy or cavernous urethra is within the penis and
ends at the male urethral orifice at the head of the
penis. Its size varies according to the size of the penis
but is about 6 inches long.
The Accessory Glands- The paired seminal vesicles produce an alkaline
viscous part of semen rich in fructose and nutrients
and pass it into each ejaculatory duct.^ - The single prostate gland produces an alkaline fluid of
semen that activates the sperm cells to swim.^ - The small paired bulbourethral glands or Cowper’s
glands secrete a thick, viscous mucus that enters the
spongy urethra and is a lubricant for sexual
intercourse.
Semen- Semen or seminal fluid is a mixture of sperm cells
and the secretions of the accessory glands.^ - It is milky in color and rich in the sugar fructose,
which provides energy for the beating flagellum of
each sperm.