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Chapter 28

HAP201 Chapter 28: The Reproductive Systems


Department
Nursing
Course Code
Nursing HAP201
Professor
Judith Card
Chapter
28

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HAP201 Week One/Chapter 28: The Reproductive Systems
Male Reproductive System
LO 28.1: Describe the location, structures and functions of the male reproductive system
The organs of the male reproductive system include the following
o Testes: also known as male gonads, these produce sperm and secrete hormones
o Duct system: transports and stores sperm, assists in their maturation and conveys to the exterior. This system includes the
epididymis, ductus deferens, ejaculatory ducts and urethra)
o Accessory sex glands: semen contains sperm plus the secretions provide by the accessory sex glands
o Supporting structures: (1) penis delivers sperm into the female reproductive tract; (2) scrotum supports the testes
SCROTUM
o Consists of loose skin and underlying subcutaneous layer that hangs from the root (attached portion) of the penis
o Raphe: a median ridge that separates the scrotum into lateral portions
o Scrotal septum: structure that internally divides the scrotum into sacs, each containing a single testis; made up of dartos
muscle (subcutaneous layer and muscle tissue)
o Master muscle: series of small bands of skeletal muscle that descend as an extension of the internal oblique muscle through
the spermatic cord to surround the testes
o Temperature of the testes is regulated by the location of the scrotum and the contraction of its muscle fibres
Normal sperm is produced in temperatures of 2-3oC below the core body temperature. This temperature is maintained
within the scrotum, since its outside the pelvic cavity
In response to cold temperatures, the cremaster and dartos muscles contract, causing the testes to move closer to the
body so they can absorb body heat. Dartos muscle contraction causes the scrotum to become tight (wrinkled) to reduce
heat loss.
Exposure to warmth reverses these actions
TESTES
o Also known as testicles; are paired oval glands in the scrotum; each testis weighs approx. 10-15 grams
o They are developed near the kidneys, in the posterior portion of the abdomen and begin to descend into the scrotum via the
inguinal canals during the end of the seventh month of fetal development
o The tunic vaginalis is a serous membrane that partially coves the testes
o Hydrocele is a collection of serous fluid in the tunica vaginalis that may be caused by testes injury or inflammation of the
epididymis
o The tunica albuginea is a white fibrous capsule that is composed of dense irregular connective tissue that surrounds the
testes and is internal to the tunica vaginalis. It forms that lobules, a series of internal compartments, by extending inward,
forming septa that divide the testis.
o Seminiferous tubules are tightly coiled tubules that are contained in the lobules; sperm production occurs here
(spermatogenesis)
The tubules contain two types of cells: (1) spermatogenic cells (sperm-forming cells) and (2) sustentacular
cells/Sertoli cells (have several functions in supporting spermatogenesis)
Spermatogonia are stem cells that develop from primordial germ cells. These cells arise from the yolk sac
and enter the testes during the fifth week of development. In embryonic testes, the primordial germ cells
differentiate into the spermatogonia, remaining dormant during childhood and actively producing sperm
during puberty. Order of advancing maturity: primary spermatocytes, secondary spermatocytes, spermatids,
and sperm cells (spermatozoon). After a sperm cell has formed, it is released into the lumen of the
seminiferous tubule
Sustentacular cells are embedded among the spermatogenic cells in the seminiferous tubules. It extends from
the basement membrane to the lumen of the tubule. Internal to the basement membrane and spermatogonia,
tight junctions join neighbouring sustentacular cells together, forming the blood-testis barrier substances
must first pass through the sustentacular cells before they reach the developing sperm. It also isolates the
developing gametes from the blood, and prevents an immune response against the spermatogenic cell’s surface
antigens (are “foreign” by the immune system). The barrier does not include spermatogonia
Sustentacular cells support and protect developing spermatogenic cells. They nourish spermatocytes,
spermatids, and sperm; phagocytize excess spermatid cytoplasm as development proceeds; and control
movements of spermatogenic cells and the release of sperm into the lumen of the seminiferous tubule. They
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also produce fluid for sperm transport, secrete the hormone inhibin and regulate the effects of testosterone and
FSH (follicle-stimulating hormone)
o Interstitial cells: cells that are present in the spaces between adjacent seminiferous tubules. They secrete testosterone.
SPERMATOGENSIS: this process takes 65-75 days and begins with the spermatogonia, which contain the diploid (2n)
number of chromosomes).
o Spermatogonia are types of stem cells, thus some remain near the basement membrane of the seminiferous tubules in an
undifferentiated state to serve as a reservoir of cells for future cell division and subsequent sperm production.
o Others lose contact with the basement membrane, travel through the blood-testis barrier and undergo development changes
and become primary spermatocytes (these are diploid; they have 46 chromosomes).
o Each primary spermatocyte replicates its DNA and then meiosis begins
o The two cells formed by meiosis I are called secondary spermatocytes, each containing 23 chromosomes, the haploid (n)
number. No replication of DNA occurs with these cells
o Spermatids are produced in meiosis II, whine the chromosomes line up along the metaphase plate and the two chromatids
separate, producing four haploid cells, i.e. spermatids.
o A single primary spermatocyte therefore produces four spermatids vis two rounds of cell division (meiosis I and
meiosis II)
o As spermatogenic cells proliferate, they fail to complete cytokinesis, remaining in contract via cytoplasmic bridges through
their entire development. This pattern accounts for the synchronized production of sperm in any given area of the
seminiferous tubule
o Spermiogensis is the final stage of process and is the stage of development of haploid spermatids into the sperm. There is no
cell division and each spermatid becomes a single sperm cell
Spherical spermatids transform into elongated, slender sperm. An acrosome will form atop the nucleus, which
condenses and elongates, a flagellum develops and mitochondria multiply. Sustentacular cells dispose of the excess
cytoplasm that sloughs off. Finally, sperm are released from the connections to sustentacular cells, an event known as
spermiation. Sperm enters lumen of tubule and fluid secreted by sustentacular cells pushes sperm along their way,
towards the ducts of the testes. At this point, sperm cannot swim
SPERM: approx. 300 million sperm complete spermatogenesis. A sperm contains several structures that are highly adapted for
reaching and penetrating a secondary oocyte
o Head: it is flattened and pointed; contains the nucleus with 23 highly condensed chromosomes. The acrosome covers two-
thirds of the nucleus and is a cap-like vesicle filled with enzymes (hyaluronidase and proteases) that help a sperm to
penetrate a secondary oocyte to start fertilization.
o Tail: this is divided into four parts neck, middle piece, principle piece and end piece
Neck: constricted region behind the head that contains centrioles, forming the microtubules that comprise the
remainder of the tail
Middle piece: contains mitochondria arranged in a spiral, which provide ATP for sperm locomotion (movement) to the
site of fertilization and for sperm metabolism
Principle piece: longest portion of the tail
End piece: terminal, tapering portion of the tail
Reproductive System Ducts in Males
Ducts of the Testis
o Fluid secreted by the sustentacular cells will generate pressure that will push sperm and fluid along the lumen of
seminiferous tubules and then into a series of very short ducts called straight tubules. These lead to a network of ducts in
the testis called rete testis. From here, sperm moves into a series of coiled efferent ducts in the epididymis that empty into a
single tube called the ductus epididymis
Epididymis
o This is a comma-shaped organ that lies along the posterior border of each testis. Each consist of ductus epididymis. The
efferent ducts from the testis join the ductus epididymis at the larger, superior portion of the epididymis called the head. The
body is the narrow mid-portion of the epididymis, and the tail is the smaller, inferior portion. At its distal end, the tail of the
epididymis continues as the ductus deferens
o This is the site of sperm maturation, the process in which sperm acquire motility and the ability to fertilize an ovum
(approx. takes 14 days). It also helps arousal by peristaltic contraction of its smooth muscle. Moreover, it stores sperm,
which remain viable here for up to several months. Sperm that is not ejaculated by that time is eventually reabsorbed.
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Ductus Deferens
o This duct is created within the tail of the epididymis, as when the ductus epididymis becomes less convoluted, its diameter
will increase. This duct is also known as vans deferens
o Functionally, this duct conveys perm during sexual arousal from the epididymis towards the urethra by peristaltic
contractions of its muscular coat. It also stores sperm for several months and those that are not ejaculated are reabsorbed.
Spermatic Cord
o This is the supporting structure of the male reproductive system that ascends out of the scrotum
o It consists of the following
Ductus (vas) deferens as it ascends through the scrotum
Testicular artery
The pampiniform plexus, veins that drain the testes and carry testosterone into circulation
Autonomic nerves
Lymphatic vessels
The cremaster muscles
Ejaculatory Ducts
o These are ducts that eject sperm and seminal vesicle secretions just before the release of semen from the urethra to the
exterior
Urethra
o In males, this is the shared terminal duct of the reproductive and urinary system. It serves as a passageway for both semen
and urine
Accessory Sex Glands
Ducts of the male reproductive system store and transport cells, but the accessor sex glands secrete most of the liquid portion of
the semen.
Seminal Vesicles
o Also called seminal glands; secrete an alkaline, viscous fluid that contains fructose, prostaglandins, and clothing proteins
that are different from those in the blood
The alkaline nature of the seminal fluid helps to neutralise the acidic environment of the male urethra and female
reproductive tract that otherwise would inactivate and kill the sperm
The fructose is used for ATP production by sperm
Prostaglandins contribute to sperm motility and viability and may stimulate smooth muscle contractions within the
female reproductive tract.
The clotting proteins help semen coagulate after ejaculation.
Prostate
o This gland secretes a milky, slightly acid fluid that contains several substances
Citric Acid: this is used by sperm for ATP production via the Krebs cycle
Proteolytic Enzymes: enzymes, such as prostate-specific antigen (PSA), pepsinogen, lysozyme, amylase, and
hyaluronidase, eventually break down clotting proteins from seminal vesicles.
Acid phosphate: function is unknown
Seminalplasmin: this is an antibiotic that can destroy bacteria. It may help decrease the number of naturally occurring
bacteria in semen and in the lower reproductive tract.
Bulbourethral Glands
o These glands are paired and are pea sized
o During sexual arousal, these glands secrete an alkaline fluid into the urethra that protects the passing sperm by neutralizing
acids from urine in the urethra.
o They also secrete mucus that lubricates the end of the penis and the lining of the urethra, decreasing the number of sperm
damaged during ejaculation. Some males release a drop or tow of this mucus upon sexual arousal and erection, but the fluid
does not contain any sperm cells
Semen
This is a mixture of sperm and seminal fluid, a liquid that consists of secretions of the seminiferous tubules, seminal vesicles
prostate, and bulbourethral glands.
The volume of semen in an ejaculation can determine whether or not a man is fertile. A very large amount of semen is needed
for successful fertilization, since only a fraction ever reaches the secondary oocyte
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