Unit Four
“Male Reproductive System”
Human Reproductive System
Origin
• The organs that allow males and females to
reproduce come from one of three germ layers
that differentiate soon after fertilization
• During the first trimester three germ layers begin
to separate to form the various organs and
structures of the human body
• The three germ layers are:
– 1. Endoderm
– 2. Mesoderm
– 3. Ectoderm
Human Reproductive System
Origin
• Ectoderm gives rise to skin, nails, hair
follicles, sweat glands, and nerves within
the lungs
– Neuroectoderm is a specialized portion of
the ectoderm that gives rise to the brain,
spinal cord, peripheral nerves, and muscles
and bones in the face
Human Reproductive System
Origin
• Mesoderm gives rise to the heart,
kidneys, various bones and muscles,
blood vessels, as well as portions of the
reproductive and urinary system
• Endoderm gives rise to the lungs, liver,
pancreas, intestines, and the lining of the
respiratory and gastrointestinal tracts
Human Reproductive System
Origin
• The previous three
germ layers begin to
form the organs and
structures of the body
fifteen days after
fertilization
• Once a baby is born
he/she has the
required sex organs
for reproduction
Male Reproductive System
• Two main categories:
– 1. Primary Sex Organs – Paired Testes
– 2. Secondary/Accessory Sex Organs –
Epididymis, Vas Deferens, Ejaculatory Duct,
and Urethra
Male Reproductive System
• Primary Sex Organs – Testes
– Testes are defined as oval shaped organs
suspended in the sacs of the scrotum and are
the site of sperm and hormone production
– Hormones are also known as Androgens
– Each testis is divided into approximately 250
compartments that contain tubules where
sperm is constantly produced
Male Reproductive System
• Male sex hormones, like Testosterone, are
secreted by cells located between the
Seminiferous Tubules
• Cells that secrete hormones are called
“Endocrine Cells”
• Since these endocrine cells are located
between the tubules, they are called
“Interstitial Cells”
Male Reproductive System
Male Reproductive System
• Secondary/Accessory Sex Organs
– Epididymis – a long narrow tube at the back
of the testes that connects the testes to the
vas deferens; enables movement of sperm
from testes to vas deferens
– Vas Deferens – additional tube through which
sperm continue their journey from the
epididymis to the ejaculatory duct
Male Reproductive System
• Secondary/Accessory Sex Organs
- Ejaculatory Duct – continuation of
tube from the vas deferens through the
prostate into the urethra allowing for
the movement of sperm toward their
final destination
- Urethra - canal through which urine is
discharged from the bladder and through
which semen is discharged in the male
Male Reproductive Anatomy
Spermatogenesis
• Spermatogenesis is the production of
sperm via Meiosis
• At puberty (12 to 14 years of age), the
Interstitial Cells begin producing
Androgens
• At the same time, the Seminiferous
Tubules also enlarge, and begin to
produce sperm
Spermatogenesis
Spermatogenesis
• 1. Spermatogonia – diploid germ cells
• 2. Spermatogonia divide via Mitosis to produce
more diploid cells
• 3. Some Spermatogonia become Primary
Spermatocytes
• 4. Primary Spermatocytes enter into Meiosis I
• 5. After Meiosis I, they are Secondary
Spermatocytes
• 6. After Meiosis II, there are four Spermatids
that differentiate into Sperm
Anatomy of Sperm
• Sperm also known as Spermatozoa, have
three parts:
– 1. Head – contains nucleus (DNA) and
Acrosome (possesses enzyme to penetrate
egg)
– 2. Middle Piece – presence of Mitochondria
provide energy for movement of the tail
– 3. Tail – used for locomotion and powered by
the Mitochondria in the Middle Piece
Anatomy of Sperm
The Prostate
• The Prostate surrounds the Urethra
adjacent to the bladder
• The Prostate secretes a thin, milky fluid
that is alkaline/basic. This adjusts the pH
of the semen.
• The fluid secreted by the Prostate also
enhances the motility of the sperm
• Prostate enlargement and cancer are
common problems in men 50 and older
Male External Genitals
• There are two external genitals:
– 1. Penis – the structure that releases the
sperm into the female reproductive tract
– 2. Scrotum – the structure that contains the
developing sperm
Male External Genitals
• The penis becomes erect in preparation for
sexual intercourse as a result of a large
influx of blood to the tissue within the penis
• Erectile Dysfunction/Impotency is the
result of the tissue in the penis not
expanding enough to retain the blood
previously introduced into the penis
Reproductive System Overview
https://www.youtube.com/watch?v=_7rsH2lo
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