Male Reproductive System - Anatomy, Physiology and Pathology

MALE REPRODUCTIVE
SYSTEM
Anatomy of Male Reproductive System
Spermatogenesis and Male Sex Hormones
Male Reproductive System-associated
Diseases

INTRODUCTION
• The male reproductive system consists of the external genitalia (penis and
scrotum), a pair of testes and associated duct system, and the accessory glands
and ducts (seminal vesicles, prostate gland and Cowper’s gland; vas deferens,
ejaculatory duct and urinogenital tract).
• It is located in the pelvic region of male.
• The most part of the genitalia undergo development in the first trimester of
gestation and on reaching reproductive maturity (at puberty), hormones play an
important role in spermatogenesis and expression of secondary sexual
characteristics.
• Maintaining reproductive health during puberty and post-pubertal stages is very
important as it can prevent a number of reproductive system-associated diseases.

ANATOMY OF MALE REPRODUCTIVE SYSTEM
 THE EXTERNAL GENITALIA
• The male external genitalia consists of
1. The PENIS and 2. The SCROTUM
 ANATOMY OF HUMAN PENIS
• The male intromittent organ, additionally serves as the urinal duct.
• Average length: 13.12 cm and average circumference: 11.66 cm of erect penis
• Consists of three parts:
1. CORPUS – The body of penis (parts: corpus cavernosa, corpus spongiosum,
glans penis and urethral meatus)
2. PENILE EPITHELIUM – Shaft skin, foreskin and preputial mucosa.
3. RADIX – The root of penis (parts: crura of penis and bulb of penis)

1. CORPUS
• The body of the penis consists of the penile shaft and the glans penis.
• Penile shaft is made of three columns of erectile tissue: two corpora cavernosa
(also called corpora cavernosa penis) (in dorsal side) and one corpus spongiosum
(also called corpus cavernosum urethrae) (in ventral side).
• The penile erection caused due to sexual arousal in man is maintained by the
controlled blood flow through the sinuses of these erectile tissues. The septa
between the two corpora is called the septum pectiniforme.
• These erectile tissues are covered by layers of connective and fibrous tissues:
dartos fascia, areolar tissue, Buck’s (deep) fascia and tunica albuginea.
• The dartos fascia (or the peripenic muscle) is a layer of connective tissue just
beneath the cutaneous skin layer of the penis and has elastic fibres. It is also
temperature sensitive and expands and contracts with temperature changes. It is
only loosely connected with the underlying areolar tissue so it provides mobility
and elasticity to the penile skin.
• The areolar tissue bears the dorsal arteries and veins and dorsal nerves associated
with the penis.

• Beneath the areolar tissue lies the Buck’s fascia, which is a dense layer of
connective tissue which surrounds the two erectile tissue types individually. This
plays an important role in maintaining erection by compressing the erection veins
of the penis.
• Tunica albuginea is the fibrous envelope of the corpus cavernosa and corpus
spongiosum. It is a bi-layered structure. It consists of ~5% elastin, with the
remainder mostly consisting of collagen.
• The tunica albuginea along with Buck’s fascia plays an important role in
maintaining penile erection.

• The glans penis is a sensitive (due to the predominance of free nerve endings),
bulbous structure at the distal end of the penis.
• It is the expanded cap of the corpus spongiosum, situated above the rounded ends
of the corpus cavernosa.
• The glans tapers at the tip and resembles an “acorn” and has the urethral opening
called the urethral orifice or urinary meatus.
• The circumference of the base of the glans form a rounded projecting border
called the corona glandis.
• The corona glandis appears overhanging the tissue fissure between the shaft and
the glans called the coronal sulcus.
• At the ventral tapering of the corona glandis, an elastic band of tissue called the
frenulum of prepuce of penis (or frenulum) connects the foreskin to the vernal
mucosa and helps retract the foreskin over the glans.

2. PENILE EPITHELIUM
• The penile epithelium consists of the shaft skin, foreskin (prepuce) and preputial
mucosa.
• The shaft skin and foreskin are cutaneous in nature and serve as a protective
barrier. The skin darkens upon reaching puberty.
• The shaft skin protects the penile shaft whereas the foreskin covers and protects
the glans and the urinary meatus in uncircumcised men.
• The foreskin is a sensitive, double-layered fold of smooth muscles, blood vessels,
neurons, skin and mucous membrane. The highly innervated mucocutaneous
zone of the penis occurs near the tip of the foreskin.
• The foreskin of adult male is generally retractable over the glans. During the early
stages of genital development and infancy, the foreskin and glans are attached to
each other by mucosal epithelium. This is known as penile adhesion. Gradually
before or during puberty, the mucosal epithelium keratinizes and thus the foreskin
gets separated from the glans and acquires complete retractability.
• On retraction of the foreskin, it forms a highly innervated wrinkly skin near the
head of the penis (at the corona) called the ridged band. More particularly, it
refers to the transitional area from the external to the internal surface of the
foreskin.

• Beneath the foreskin lies the dartos fascia. The elastic fibers contained in this layer
form an innervated whorl at the tip of the foreskin.
• The preputial mucosa (inner mucosa) is the epithelium of the inside of the
foreskin. It starts at the ridged band of the foreskin and continues to the coronal
sulcus, where it meets the epithelium of the glans and penile shaft. The preputial
mucosa is devoid of hair, as is the cutaneous surface.
• The inner mucosa contains apocrine glands, which secrete cathepsin B, lysozyme,
chymotrypsin, neutrophil elastase (has protective immunological functions
and hormones such as androsterone. These secretions, along with dead cells,
mucin and sebum, form a white, smooth and moist lubricant called smegma.

3. RADIX
• The root of the penis consists of the bulb of penis and crura of penis.
• The bulb of penis is the proximal tip of the corpus spongiosum, resembling an
enlarged bulb-like structure, fitted into the crura of the penis.
• The crura of the penis consists of the two tapering ends of the corpora cavernosa
called the crus and merges with the pelvic floor muscles.

 ANATOMY OF SCROTUM
• It is a suspended dual-chambered sack made of skin and smooth muscle.
• The scrotum bears the testes. One testis is typically placed lower than the other to
avoid compression in the event of impact.
• The perineal raphae is a small, vertical, slightly raised ridge of scrotal skin under
which is found the scrotal septum. It appears as a thin longitudinal line that runs
front to back over the entire scrotum.
• During development, each testis descends from their starting point on
the posterior abdominal wall, down the abdomen and through the inguinal canals
to reach the scrotum.
• In humans and some other mammals, the scrotum becomes covered with pubic
hair at puberty, and will usually tighten during penile erection and when exposed
to cold temperature with the help of the cremaster muscles and its associated
nerves.
• The scrotum has the following layers: the skin, dartos fascia, external spermatic
fascia, cremaster muscle, internal spermatic fascia and tunica vaginalis.

• The skin of the scrotum is thin, wrinkled and darkens upon reaching puberty. It also
develops scrotal hair as one of the secondary sexual characteristics.
• The dartos of scrotum consists mostly of smooth muscle. The tone of this smooth
muscle is responsible for the wrinkled (rugose) appearance of the scrotum.
• The external spermatic fascia (also called intercrural fascia) is a thin membrane,
prolonged downward around the surface of the spermatic cord and testis. It is
separated from the dartos by loose areolar tissue.
• The cremaster muscle is a thin layer of involuntary striated muscle found in the inguinal
canal and scrotum between the external and internal layers of spermatic fascia,
surrounding the testis and spermatic cord. It is a paired structure, one on each side of
the body. It is innervated from the genital branch of the genitofemoral nerve.
• The cremaster muscle's function is to raise and lower the testes in order to regulate
scrotal temperature for optimal spermatogenesis and survival of the resultant
spermatozoa (35 °C i.e. two degrees below the body temperature of 37 °C. It does this
by increasing or decreasing the exposed surface area of the surrounding tissue, allowing
faster or slower dissipation of body heat.
• It also contracts during arousal which can prevent injury to the testes during copulation
and ejaculation. Retraction can also occur during moments of extreme fear, possibly to
help avoid injuring the testes while dealing with a fight-or-flight situation.

• The internal spermatic fascia (also called infundibuliform fascia) is a thin layer,
which loosely invests the spermatic cord.
• The tunica vaginalis is the pouch of serous membrane that covers the testes.
• Consists of visceral lamina and parietal lamina. The visceral lamina covers the
greater part of the testis and epididymis whereas the parietal lamina is far more
extensive than the visceral, extending upward for some distance in front and on
the medial side of the spermatic cord and reaching below the testis. The inner
surface of the tunica vaginalis is smooth and covered by a layer of simple
squamous mesothelial cells. The interval between the visceral and parietal
laminae constitutes the cavity of the tunica vaginalis called cavum vaginale in
which the testis is suspended.
1. Testis
2. Epididymis
3. Mesorchium
4. Visceral lamina
5. Parietal lamina
6. Cavum vaginalis
7. Epididymis
8. Internal spermatic fascia

 THE TESTIS AND ASSOCIATED DUCT SYSTEM
• The testis is the main male reproductive gland (gonad); homologous to ovary in
female.
• Produces spermatozoa and androgens (primarily testosterone).
 ANATOMY OF TESTIS AND ASSOCIATED DUCT SYSTEM
• The testes are covered by a tough membranous shell called the tunica albuginea.
• The testis contains the following tubules and ducts: seminiferous tubules, rete
testis, vasa efferentia, epididymis and vas deferens.
• The glandular structure of the testis consists of numerous compartments called
the testicular lobules formed by septa made by the tunica albuginea. The number
of lobules vary 250-290 in a single testis.
• The lobules are conical in shape, the base being directed toward the circumference
of the organ, the apex toward the mediastinum testis.
• Each lobule is contained in one of the intervals between the fibrous septa which
extend between the mediastinum testis and the tunica albuginea, and consists of
1-3 seminiferous tubules.

• The seminiferous tubules are the specific location of meiosis and the subsequent
creation of spermatozoa.
• The epithelium (called germinal epithelium) of the tubule consists of two types of
cells: sustentacular cells known as Sertoli cells (nurse cells), which are tall,
columnar type cells that line the tubule and spermatogenic cells (also called
spermatogonia, found in between the Sertoli cells), which differentiate
through meiosis to spermatozoa.
• Adjacent to the seminiferous tubules lie the Leydig cells, which secretes
testosterone.
• Sertoli cells function to nourish the developing spermatozoa. They
secrete androgen-binding protein (ABP), a binding protein which increases the
concentration of testosterone inside the seminiferous tubules.
• The seminiferous tubules are of two types: convoluted and straight, convoluted
toward the lateral side, and straight (also called tubulus rectus) as the tubule
comes medially to form ducts that will exit the testis.
• Tubuli recti is lined only by Sertoli cells.

• The rete testis is the network of interconnecting tubules where the tubuli recti
empty. It is located within a highly vascular connective tissue in the mediastinum
testis. The epithelial cells form a single layer that lines the inner surface of the
tubules. These cells are cuboidal, with microvilli and a single cilium on their
surface.
• Sperm cells leave the seminiferous tubules in the dilute secretions of Sertoli cells.
The rete testis modify the luminal fluids with a limited amount of secretion and
reabsorption, but their primary function is to mix and transport the sperm into the
vasa efferentia.
• The vasa efferentia (also called efferent ductule) connect the rete testis with the
initial section of the epididymis.
• In humans, there are ~15 to 20 vasa efferentia, which occupy nearly one-third of
the head of the epididymis.
• The ductuli are unilaminar and composed of columnar ciliated and non-ciliated
(absorptive) cells. The ciliated cells serve to stir the luminal fluids, to help ensure
homogeneous absorption of water from the fluid produced by the testis, which
results in an increase in the concentration of luminal sperm. The epithelium is
surrounded by a band of smooth muscle that helps to propel the sperm toward
the epididymis.

• The epididymis is a tube that connects testis (through the vasa efferentia) to vas
deferens. It is a single, narrow, tightly-coiled tube in adult humans, 6-7 m in length.
• The epididymis can be divided into three main regions:
1. CAPUT (head of the epididymis): receives spermatozoa via the vasa
efferentia of the mediastinum testis. It is characterized by a
thick epithelium with long stereocilia and a little smooth muscle. It is involved
in absorbing fluid to make the sperm more concentrated.
2. CORPUS (body of the epididymis): has an intermediate epithelium and smooth
muscle thickness.
3. CAUDA (tail of the epididymis): has the thinnest epithelium of the three
regions and the greatest quantity of smooth muscle.
• The epididymis is covered by a two layered pseudostratified epithelium.
The epithelium is separated by a basement membrane from the connective
tissue wall which has smooth muscle cells.

• The major cell types in the epithelium are: 1. Principal cells: columnar cells in the
caput region these cells have long stereocilia. The stereocilia are much shorter in
the caudal segment. They also secrete carnitine, sialic acid, glycoproteins
and glycerylphosphorylcholine into the lumen; 2. Basal cells: shorter, pyramid-
shaped cells which contact the basal lamina but taper off before their apical
surfaces reach the lumen. These are thought to be undifferentiated precursors of
principal cells; 3. Apical cells: predominantly found in the head region; 4. Clear
cells: predominant in the tail region; 5. Intraepithelial lymphocytes: distributed
throughout the tissue; 6. Intraepithelial macrophages.

• The vas deferens is the duct which transport sperm from the epididymis to
the ejaculatory duct in anticipation of ejaculation. It is a partially coiled tube which
exits the abdominal cavity through the inguinal canal.
• There are two ducts, connecting the left and right epididymis with the seminal
vesicles to form the ejaculatory duct in order to move sperm.
• In humans, each tube is about 30 cm long, 3-5 mm in diameter and is surrounded
by smooth muscle. Its epithelium is pseudostratified columnar epithelium lined
by stereocilia. They are part of the spermatic cords.
• During ejaculation, the smooth muscle in the walls of vas deferens contracts
reflexively, thus propelling the sperm forward (called as peristalsis). The sperm is
transferred from the vas deferens into the urethra, collecting secretions from the
male accessory sex glands.

 ACCESSORY GLANDS AND DUCTS
• The three main types of male accessory glands (MAGs) are: seminal vesicles,
prostate gland, Cowper’s (bulbourethral) gland and urethral glands.
• The products of these glands serve to nourish and activate the spermatozoa, to
clear the urethral tract prior to ejaculation, serve as the vehicle of transport of
the spermatozoa in the female tract, and to plug the female tract after placement
of spermatozoa to help ensure fertilization.
• Seminal vesicles, a pair of glands that are positioned below the urinary
bladder and lateral to the vas deferens. Each vesicle consists of a single tube
folded and coiled on itself, with occasional diverticula in its wall. The excretory
duct of each seminal gland unites with the corresponding vas deferens (the
ampullary duct) to form the two ejaculatory ducts.
• Each seminal vesicle spans ~5 cm, though its full unfolded length is ~10 cm, but it
is curled up inside the gland's structure.

• Seminal vesicles have mucosa, consisting of a lining of interspersed columnar cells and
a lamina propria; and a thick muscular wall. The lumen of the glands is highly irregular and
stores secretions from the glands of the vesicles.
• The epithelium is pseudostratified columnar in character, similar to other tissues in the male
reproductive system. The height of these columnar cells, and therefore activity, is dependent
upon testosterone levels in the blood.
• The lamina propria, containing underlying small blood vessels and lymphatics. Together with
the epithelia, this is called the mucosa, and is arranged into convoluted folds, increasing the
overall surface area.
• A muscular layer, consisting of an inner circular and outer longitudinal layer of smooth
muscle, can also be found.
• Seminal vesicles secrete a significant proportion of the fluid (70-85%) contributing to semen.
• Lipofuscin granules from dead epithelial cells give the secretion its yellowish color.
• Seminal fluid is alkaline, resulting in human semen having a mildly alkaline pH. The alkalinity
of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm.
The vesicles produce semenogelin, a protein that causes semen to become sticky and jelly-
like after ejaculation.
• The thick secretions from the seminal vesicles contain proteins, enzymes, fructose, mucous,
vitamin C, flavins, phosphorylcholine and prostaglandins.
• The seminal vesicles contain 5α-reductase which metabolizes testosterone into its much
more active form, dihydrotestosterone (DHT). They also contain luteinizing hormone
receptors.

• The prostate is a walnut-sized exocrine gland which secretes a fluid which contributes to the
volume of the semen. This prostatic fluid is slightly alkaline, milky or white in appearance, and in
humans usually constitutes roughly 30% of the volume of semen, the other 70%
being sperms and seminal fluid. The mean weight of the normal prostate in adult males is about
11 g. The prostate surrounds the urethra just below the urinary bladder.
• The prostatic fluid is expelled in the first part of ejaculate, together with most of the sperm. In
comparison with the few spermatozoa expelled together with mainly seminal fluid, those in
prostatic fluid have better motility, longer survival and better protection of genetic material.
• Prostate can be divided into many zones or lobes. It does not have a capsule; rather an integral
fibromuscular band surrounds it. It is sheathed in the muscles of the pelvic floor, which contract
during the ejaculatory process. The prostate also contains some smooth muscles that also help
expel semen during ejaculation.
• Three histological types of cells are present in the prostate gland: glandular cells, myoepithelial
cells, and subepithelial interstitial cells.
• The secretory epithelium is mainly pseudostratified, comprising tall columnar cells and basal
cells, which are supported by a fibroelastic stroma — containing randomly oriented smooth-
muscle bundles — that is continuous with the bladder. Within the prostate, the urethra coming
from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts.
• In human prostatic secretions, the protein content is less than 1% and includes proteolytic
enzymes, prostatic acid phosphatase, beta-microseminoprotein, and prostate-specific antigen.
The secretions also contain Zn with a concentration 500-1000 times the concentration in blood.
DHT predominantly regulates the prostate.

• The bulbourethral glands or Cowper's glands is a pair of two small exocrine MAG located
posterior and lateral to the membranous portion of the urethra at the base of the penis.
• The bulbourethral glands are responsible for producing a pre-ejaculate fluid called Cowper's
fluid which is secreted during sexual arousal, lubricating and neutralizing the acidity of the
urethra in preparation for the passage of sperm cells.
• They are compound tubulo-alveolar glands, each approximately the size of a pea in humans.
They are composed of several lobules held together by a fibrous covering. Each lobule
consists of a number of acini, lined by columnar epithelial cells, opening into a duct that
joins with the ducts of other lobules to form a single excretory duct. This duct is ~2.5 cm
long and opens into the bulbar urethra at the base of the penis. The glands gradually
diminish in size with advancing age.
• The bulbourethral gland contributes up to 4 ml of fluid during sexual arousal. The secretion is
a clear fluid rich in mucoproteins.

• The urethral glands (Littré glands/ periurethral glands) secrete mucus and are most
numerous in the section of the urethra that runs through the penis. Urethral glands produce
a colloid secretion containing glycosaminoglycans; this secretion protects the urethral
epithelium from urine.
• The ejaculatory ducts are paired structures in male reproductive system. Each ejaculatory
duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They
pass through the prostate and open into the urethra at the seminal colliculus.
• During ejaculation, semen passes through the prostate gland, enters the urethra and exits
the body via the urinary meatus.

SPERMATOGENESIS
• Spermatogenesis is the process by which haploid spermatozoa develop from germ
cells in the seminiferous tubules of the testes.
• This process starts with the mitotic division of the stem cells located close to the
basement membrane of the tubules called spermatogonial stem cells (or
spermatogonia).
• The mitotic division of the stem cells produces two types of cells: type A cells (replenish
the stem cells) and type B cells (differentiate into primary spermatocytes).
• The primary spermatocyte divides meiotically (Meiosis I) into two secondary
spermatocytes. Each secondary spermatocyte divides into two equal
haploid spermatids by Meiosis II.
• The spermatids are transformed into spermatozoa by the process of spermiogenesis.
• These develop into mature spermatozoa, also known as sperm cells.
• Spermatogenesis is highly dependent upon optimal conditions for the process to occur
correctly, and is essential for sexual reproduction.
• Spermatogenesis starts at the age of puberty de to the increase in the secretion of
gonadotropin releasing hormone
• DNA methylation and histone modification have been implicated in the regulation of
this process.It starts at puberty and usually continues uninterrupted until death,
although a slight decrease can be discerned in the quantity of produced sperm with
increase in age.

SPERMATOGENESIS
• For humans, the entire process of spermatogenesis is variously estimated as taking
74-120 days. Including the transport on ductal system, it takes 3 months.
• Testes produce 200-300 million spermatozoa daily. However, only about half or
100 million of these become viable sperm.

SPERMATOGENESIS
 STAGES OF SPERMATOGENESIS
• The entire process of spermatogenesis can be broken up into several distinct
stages, each corresponding to a particular type of cell in humans.
1. Spermatocytogenesis
• results in the formation of haploid secondary spermatocytes.
• In spermatocytogenesis, a diploid spermatogonium, which resides in the basal
compartment of the seminiferous tubules, divides mitotically, producing two
diploid intermediate cells called primary spermatocytes.
• Each primary spermatocyte then moves into the adluminal compartment of the
seminiferous tubules and duplicates its DNA and subsequently undergoes meiosis I
to produce two haploid secondary spermatocytes.
2. Spermatidogenesis
• Spermatidogenesis is the creation of spermatids from secondary spermatocytes.
Secondary spermatocytes produced earlier rapidly enter meiosis II and divide to
produce haploid spermatids.
• Each cell division from a spermatogonium to a spermatid is incomplete; the cells
remain connected to one another by bridges of cytoplasm to allow synchronous
development.

SPERMATOGENESIS
3. Spermiogenesis
• During spermiogenesis, the spermatids begin to form a tail by
growing microtubules on one of the centrioles, which turns into basal body. These
microtubules form an axoneme. Later the centriole is modified in the process
of centrosome reduction. The anterior part of the tail (called midpiece) thickens
because mitochondria are arranged around the axoneme to ensure energy supply.
Spermatid DNA also undergoes packaging, becoming highly condensed. The DNA is
packaged firstly with specific nuclear binding proteins like histones, which are
subsequently replaced with protamines during spermatid elongation. The
resultant tightly packed chromatin is transcriptionally inactive. The Golgi
apparatus surrounds the now condensed nucleus, becoming the acrosome.
• Maturation then takes place under the influence of testosterone, which removes
the remaining unnecessary cytoplasm and organelles. The excess cytoplasm,
known as residual bodies, is phagocytized by surrounding Sertoli cells in the
tubules.
• The resulting spermatozoa are now mature but lack motility, rendering them
sterile. The mature spermatozoa are released from the protective Sertoli cells into
the lumen of the seminiferous tubule in a process called spermiation.
• The non-motile spermatozoa are transported to the epididymis in testicular
fluid secreted by the Sertoli cells with the aid of peristaltic contraction. While in
the epididymis, the spermatozoa gain motility and become capable of fertilization.

SPERMATOGENESIS
 ROLE OF SERTOLI CELLS
• At all stages of differentiation, the spermatogenic cells are in close contact with
Sertoli cells which are thought to provide structural and metabolic support to the
developing sperm cells.
• After Spermatogenesis,sperm cells become embedded in the sertoli cells and are
finally released from the seminiferous tubules by the process called spermiation.
• Increased levels of gonadotropin then acts at the anterior pituitary gland and
stimulates secretion of two gonadotropins-LH and FSH.
• FSH acts on the sertoli cells and stimulates secretion of some factors which help in
the process of spermiogenesis.
• They support the developing gametes in the following ways: 1. Maintain the
environment necessary for development and maturation, via the blood-testis
barrier (by ICAM-1); 2. Secrete substances initiating meiosis; 3. Secrete supporting
testicular fluid; 4. Secrete androgen-binding protein (ABP); 5. Secrete hormones
affecting pituitary gland control of spermatogenesis, particularly the polypeptide
hormone, inhibin; 6. Phagocytize residual cytoplasm left over from
spermiogenesis; 7. Secretion of anti-Müllerian hormone causes deterioration of
the Müllerian duct; 8. Protect spermatids from the immune system of the male,
via the blood-testis barrier; 9. Contribute to the spermatogonial stem cell niche.

SPERMATOGENESIS
 ROLE OF LEYDIG CELLS
• Leydig cells release a class of hormones called androgens (19-C steroids). They
secrete testosterone, androstenedione and dehydroepiandrosterone (DHEA),
when stimulated by the pituitary hormone luteinizing hormone (LH).
• LH acts at the leydig cells and stimulates synthesis and secretion of androgens.
• Androgens in turn stimulate the process of spermatogenesis.
• Prolactin (PRL) increases the response of Leydig cells to LH by increasing the
number of LH receptors expressed on Leydig cells.

SPERMATOGENESIS
 STRUCTURE OF SPERM CELL
• The human sperm cell is the reproductive cell in males and will only survive in warm
environments; once it leaves the male body the sperm's survival likelihood is reduced
and it may die, thereby decreasing the total sperm quality.
• A human sperm cell consists of a flat, disc shaped head 5.1 µm by 3.1 µm and a tail
50 µm long. The tail flagellates, which propels the sperm cell (at about 1–3 mm/minute
in humans) by whipping in an elliptical cone. Sperm have an olfactory guidance
mechanism and after reaching the Fallopian tubes, must undergo a period of
capacitation before penetration of the ovum.
• Head: It has a compact nucleus with only chromatic substance and is surrounded by
only a thin rim of cytoplasm. Above the nucleus lies a cap-like structure called
the acrosome, formed by modification of the Golgi body, which secretes the
enzyme spermlysin.
• Neck: It is the smallest part (0.03 µm), and has a proximal and distal centriole. The
proximal centriole enters into the egg during fertilisation and starts the first cleavage
division of the egg, which has no centriole. The distal centriole gives rise to the axial
filament which forms the tail and has a (9+2) arrangement. A transitory membrane
called the manchette lies in the middle piece.
• Middle piece: It has 10–14 spirals of mitochondria surrounding the axial filament in the
cytoplasm. It provides motility, and hence is called the powerhouse of the sperm. It
also has a ring centriole (annulus) that form a diffusion barrier between the middle
piece and the principal piece and serve as a stabilizing structure for tail rigidity.

SPERMATOGENESIS
• Tail: It is the longest part (50 µm), having an axial filament surrounded by cytoplasm
and plasma membrane, but at the posterior end the axial filament is naked.
• Semen has an alkaline nature and the spermatozoa do not reach full motility
(hypermotility) until they reach the vagina, where the alkaline pH is neutralized by
acidic vaginal fluids. This gradual process takes 20–30 minutes. During this
period, fibrinogen from the seminal vesicles forms a clot, securing and protecting the
sperm. Just as they become hypermotile, fibrinolysin from the prostate gland dissolves
the clot, allowing the sperm to progress optimally.
• The spermatozoon is characterized by a minimum of cytoplasm and the most densely
packed DNA known in eukaryotes. Compared to mitotic chromosomes in somatic cells,
sperm DNA is at least six fold more highly condensed.
 EJACULATION
• Ejaculation is the discharge of semen from the male reproductory tract, usually
accompanied by orgasm(the sudden discharge of accumulated sexual excitement
during the sexual response cycle, resulting in rhythmic muscular contractions in
the pelvic region characterized by sexual pleasure; controlled by the autonomic
nervous system). It is the final stage and natural objective of male sexual stimulation
and an essential component of natural conception.
• In rare cases, ejaculation occurs because of prostatic disease. Ejaculation may also
occur spontaneously during sleep (a nocturnal emission). Anejaculation is the
condition of being unable to ejaculate.
• Ejaculation is usually very pleasurable for men; dysejaculation is an ejaculation that is
painful or uncomfortable. Retrograde ejaculation is the condition where semen travels
backwards into the bladder rather than out the urethra.

SECONDARY SEXUAL CHARACTERISTICS AND SEX HORMONES
 SECONDARY MALE SEXUAL CHARACTERISTICS
• During the onset of puberty in males, testosterone and other hormone levels in
the blood get elevated resulting in secondary male sexual characters.
• In males, testosterone directly increases size and mass of muscles, vocal cords
and bones, Enlargement of larynx (Adam's apple) deepening the voice, and
changing the shape of the face and skeleton.
• Converted into DHT in the skin, it accelerates growth of androgen-responsive facial
and body hair but may slow and eventually stop the growth of head hair.
Increased stature.
• Growth of facial hair and body hair, including underarm, abdominal, chest
hair and pubic hair. Loss of scalp hair due to androgenic alopecia can also occur.
• Greater mass of thigh muscles in front of the femur.
• Increased development of testes, penis and associated organs.
• Heavier skull and bone structure.
• Increased muscle mass and strength.
• Broadening of shoulders and chest; shoulders wider than hips
• Increased secretions by sebaceous glands.
• Coarsening or rigidity of skin texture due to less subcutaneous fat.

 MALE SEX HORMONES
1. Luteinizing hormone (LH)
• produced by gonadotropic cells in the anterior pituitary gland.
• LH acts upon the Leydig cells of the testes and is regulated by gonadotropin-
releasing hormone (GnRH).
• The Leydig cells produce testosterone under the control of LH, which regulates the
expression of the enzyme 17β-hydroxysteroid dehydrogenase that is used to
convert androstenedione, the hormone produced by the testes, to testosterone.
• When testosterone levels are low, it stimulates the pituitary gland to release LH. As
the levels of testosterone increase, it will act on the pituitary through a negative
feedback loop and inhibit the release of GnRH and LH consequently.
2. Follicle-stimulating hormone (FSH)
• FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary
gland and regulates the development, growth, pubertal maturation and
reproductive processes of the body. FSH and LH work together in the reproductive
system.
• In males, FSH induces Sertoli cells to secrete androgen-binding proteins (ABPs),
regulated by inhibin's negative feedback mechanism on the anterior pituitary.
• FSH also stimulates primary spermatocytes to undergo the first division of meiosis,
to form secondary spermatocytes.

3. Testosterone
• Testosterone is the primary male sex hormone (steroid). In male humans,
testosterone plays a key role in the development of male reproductive tissues such
as testes and prostate, as well as promoting secondary sexual characteristics such
as increased muscle and bone mass, and the growth of body hair.
• Testosterone is necessary for normal sperm development.
• It activates genes in Sertoli cells, which promote differentiation of spermatogonia.
• Androgens including testosterone enhances muscle growth.
• Testosterone also regulates the population of thromboxane A2 receptors
on megakaryocytes and platelets and hence platelet aggregation in humans.
• Adult testosterone effects are more clearly demonstrable in males than in females,
but are likely important to both sexes. Some of these effects may decline as
testosterone levels might decrease in the later decades of adult life.

MALE REPRODUCTIVE SYSTEM-ASSOCIATED DISEASES
• Some of the diseases and conditions associated with the male reproductive system
are:
1. Genitourinary cancers (e.g. Prostate cancer, testicular cancer)
2. Enlarged prostate or BPH
3. Prostatitis
4. Erectile dysfunction
5. Cryptorchidism or Undescended testicle (UDT)
6. Testosterone deficiency syndrome
7. Varicocele
8. Hydrocele
9. Male infertility
10. Sexually transmitted infections (STIs)

1. Genitourinary cancers
 Prostate cancer
• Prostate cancer is cancer that occurs in the prostate gland.
• Prostate cancer is one of the most common types of cancer in men. Usually
prostate cancer grows slowly and is initially confined to the gland itself, where it
may not cause serious harm. However, some types of prostate cancer are
aggressive and can spread quickly.
• Prostate cancer that's detected early — when it's still confined to the prostate
gland — has a better chance of successful treatment.
 Symptoms
• Trouble in urinating, decreased force in the stream of urine, blood in semen,
discomfort in the pelvic area, erectile dysfunction.
 Prevention
• Choose a healthy diet full of fruits and vegetables.
• Exercise most days of the week.
• Maintain a healthy weight.

 Testicular Cancer
• The testes produce male sex hormones and sperm for reproduction. Testicular cancer
occurs in the testis (or testes).
• Compared with other types of cancer, testicular cancer is rare. But it is the most
common cancer in American males between the ages of 15 and 35. In India, the
occurrence rate is 1:1,00,000.
• Testicular cancer is highly treatable, even when cancer has spread beyond the testis.
The cancer usually affects only one testis.
• Depending on the type and stage of testicular cancer, you may receive one of several
treatments, or a combination.
 Symptoms
• A lump or enlargement in either testis.
• A feeling of heaviness in the scrotum and firmness of the testicle.
• A dull ache in the lower abdomen or groin and scrotum.
• Gynecomastia due to hormonal effects of β-hCG.
• A sudden collection of fluid in the scrotum, pain or discomfort in a testicle or the
scrotum.
• Lower back pain (lumbago) due to cancer spreading into lymph nodes.

2. Enlarged prostate or Benign Prostatic Hyperplasia (BPH)
• An enlarged prostate means the gland has grown bigger. Prostate enlargement
happens to almost all men as they get older.
• An enlarged prostate is often called benign prostatic hyperplasia (BPH). It is not
cancer and it does not raise the risk for prostate cancer.
 Symptoms
• Dribbling at the end of urination, inability to urinate (urinary retention),
incomplete emptying of your bladder, urinary incontinence.
• Needing to urinate 2 or more times per night.
• Pain with urination or bloody urine (these may indicate infection).
• Slowed or delayed start of the urinary stream, straining to urinate.
• Strong and sudden urge to urinate, weak urine stream.

3. Prostatitis
• Prostatitis is the inflammation (swelling) of the prostate gland. It can be very
painful and distressing, but will often get better eventually.
• Unlike other prostate conditions which usually affect older men, prostatitis can
develop in men of all ages. But it commonly affects men aged between 30 and 50.
• There are two main types of prostatitis: 1. chronic prostatitis – where the
symptoms come and go over a period of several months; it's the most common
type and not usually caused by an infection, and 2. acute prostatitis – where the
symptoms are severe and develop suddenly; it's rare, but can be serious and
requires immediate treatment, and is always caused by an infection.
 Symptoms
• Severe pain in or around your penis, testes, anus, lower abdomen or lower back,
defecation can be painful.
• Urinary symptoms, sometimes blood in your urine, acute urinary retention.
• Generally feeling unwell with aches, pains and possibly fever.
• A small amount of thick fluid (discharge) may come out of the penis.
• An enlarged or tender prostate on rectal examination, although in some cases it
may be normal.
• Sexual problems, such as erectile dysfunction, pain when ejaculating or pelvic pain
after copulation.

4. Erectile dysfunction (ED)
• Erectile dysfunction (impotence) is the inability to get and keep an erection firm
enough for intercourse.
• Having trouble in erection from time to time isn't necessarily a cause for concern. If
erectile dysfunction is an on-going issue, however, it can cause stress, affect your self-
confidence and contribute to relationship problems. Problems getting or keeping an
erection can also be a sign of an underlying health condition that needs treatment and
a risk factor for heart disease.
• If you're concerned about ED, talk to your doctor — even if you're embarrassed.
Sometimes, treating an underlying condition is enough to reverse erectile dysfunction.
In other cases, medications or other direct treatments might be needed.
 Symptoms
• Trouble getting and keeping an erection.
• Reduced sexual desire (libido).
 Prevention
• Manage diabetes, heart disease or other chronic health conditions.
• See your doctor for regular check-ups and medical screening tests.
• Quit smoking, limit or avoid alcohol, and don't use illegal drugs.
• Exercise regularly.
• Take steps to reduce stress, get help for anxiety, depression or other mental health
concerns.

5. Cryptorchidism
• The absence of one or both testes from the scrotum.
• A testis absent from the normal scrotal position may be: 1. anywhere along the
"path of descent" from high in the posterior (retroperitoneal) abdomen, just
below the kidney, to the inguinal ring; 2. in the inguinal canal; 3. ectopic, having
"wandered" from the path of descent, usually outside the inguinal canal and
sometimes even under the skin of the thigh, the perineum, the opposite scrotum,
or the femoral canal; 4. undeveloped (hypoplastic) or severely abnormal
(dysgenetic); 5. missing (anorchia).
• Undescended testes are associated with reduced fertility, increased risk
of testicular germ-cell tumors and psychological problems when the boy is grown.
• Undescended testes are also more susceptible to testicular torsion (and
subsequent infarction) and inguinal hernias.
• Without intervention, an undescended testicle will usually descend during the first
year of life, but to reduce these risks, undescended testes can be brought into the
scrotum in infancy by a surgical procedure called an orchiopexy.

6. Testosterone deficiency syndrome
• Testosterone deficiency syndrome (also known as late-onset hypogonadism), is a
clinical and biochemical syndrome that can occur in men in association with advancing
age.
• The condition is characterized by deficient testicular production of testosterone. It may
affect multiple organ systems and can result in substantial health consequences.
 Symptoms
• Decreased libido, erectile dysfunction, decreased frequency of morning erections,
decreased performance.
• Increased visceral body fat or obesity, decreased lean muscle mass, decreased strength,
fatigue, decreased physical activity, low bone mineral density, anemia, flushes.
• Loss of facial, axillary and pubic hair or slow beard growth, decline in general feeling of
well-being, depression, mood changes, irritability, inability to concentrate, insomnia.
 Treatment
• Testosterone supplementation in most cases.
• Therapy aimed at improving pituitary function, metabolic alterations that may respond
to other measures in case of secondary hypogonadism.

7. Varicocele
• Varicocele is an abnormal enlargement of the pampiniform venous plexus in the
scrotum. This plexus of veins drains blood from the testicles back to the heart.
The vessels originate in the abdomen and course down through the inguinal
canal as part of the spermatic cord on their way to the testis.
• Varicoceles occur in around 15% to 20% of all men.The incidence of varicocele
increase with age.
 Symptoms
• Soft lumps, usually above the testis and mostly on the left side of the scrotum.
Right-sided and bilateral varicocele does also occur.
• Pain or heaviness in their scrotum. Varicocele can be one of the causes of male
infertility.

8. Hydrocele
• A hydrocele is an accumulation of serous fluid in a body cavity. A hydrocele
testis is the accumulation of fluids around a testis. It can occur in almost any part
of the body. In virtue of the topic, hydrocele can occur in penis, spermatic code or
epididymis.
• Hydrocele testis is often caused by fluid secreted from tunica vaginalis.
• Primary hydroceles may develop in adulthood, particularly in the elderly and in hot
countries, by slow accumulation of serous fluid. This is presumably caused by
impaired reabsorption, which appears to be the explanation for most primary
hydroceles.
• A hydrocele can also be the result of a plugged inguinal lymphatic system caused
by repeated, chronic infection of Wuchereria bancrofti or Brugia malayi,
two mosquito-borne parasites (nematodes) of Africa and Southeast Asia,
respectively. As such, the condition would be a part of more
diffuse sequelae commonly referred to as elephantiasis, which also affects the
lymphatic system in other parts of the body.

 Symptoms of hydrocele testis
• In testes, a hydrocele feels like a smooth, small fluid-filled balloon inside
the scrotum, mainly in front of the testis.
• Hydroceles vary greatly in size and are typically painless and harmless. However, as
the fluid continues to accumulate and the scrotum further enlarges, more
discomfort can be expected.
• Large hydroceles will cause discomfort because of their size. Sometimes pain can
be in both testes.
• It has also been found to decrease a man's sex drive (libido) and makes him less
active for fear of enlarging the mass. As the fluid of a hydrocele is transparent,
light shone through the hydrocelic region will be visible from the other side. This
phenomenon is called transillumination.
• Symptoms of a hydrocele can easily be distinguished from testicular cancer, as a
hydrocele is soft and fluid-filled, whereas testicular cancer feels hard and rough.
• A hydrocele testis is not generally thought to affect fertility. However, it may be
indicative of other factors that may affect fertility.

9. Male Infertility
• Male infertility refers to a male's inability to cause pregnancy in a fertile
female.
• In humans it accounts for 40–50% of infertility. It affects approximately 7%
of all men. Male infertility is commonly due to deficiencies in the semen
and semen quality is used as a surrogate measure of male fertility.
• Male infertility can be due to: 1. immune infertility (due to production of
anti-sperm antibodies); 2. chromosomal anomalies and genetic
mutations (like Klinefelter syndrome and Y chromosome deletions); 3. age
and life style; 4. neoplasm (e.g. seminoma); 5. cryptorchidism; 6. trauma;
7. hydrocele; 8. defects in USP26 in some cases; 9. acrosomal defects
affecting egg penetration; 10. idiopathic oligospermia.

 Prevention
• Avoiding smoking, heavy drug and alcohol use, as it damages sperm DNA.
• Avoiding excessive heat to the testes; even the heat from laptop is enough to
heat up the testes.
• Maintaining optimal frequency of coital activity: sperm counts can be
depressed by daily coital activity and sperm motility may be depressed by
coital activity that takes place too infrequently (abstinence 10–14 days or
more).
• Healthy diets (i.e. the Mediterranean diet) rich in such nutrients as omega-3
fatty acids, some antioxidants and vitamins. Diets low in saturated fatty acids
(SFAs) and trans-fatty acids (TFAs) are inversely associated with low semen
quality parameters. In terms of food groups, fish, shellfish and seafood,
poultry, cereals, vegetables and fruits, and low-fat dairy products have been
positively related to sperm quality. However, diets rich in processed meat, soy
foods, potatoes, full-fat dairy products, coffee, alcohol and sugar-sweetened
beverages and sweets have been inversely associated with the quality of
semen in some studies.

10. Sexually transmitted infections (STDs)
• Sexually transmitted infections (STIs), also referred to as sexually transmitted
diseases (STDs), are infections that are commonly spread by sexual activity,
especially vaginal intercourse, anal sex and oral sex.
• Many times STIs initially do not cause symptoms. This results in a greater risk of
passing the disease on to others. Symptoms and signs of disease may
include vaginal discharge, penile discharge, ulcers on or around the genitals,
and pelvic pain. STIs can be transmitted to an infant before or during childbirth
and may result in poor outcomes for the baby. Some STIs may cause problems with
the ability to get pregnant.
• More than 30 different bacteria, viruses, and parasites can be transmitted through
sexual activity. Bacterial STIs include chlamydia, gonorrhea, and syphilis. Viral STIs
include genital herpes, HIV/AIDS, and genital warts. Parasitic STIs
include trichomoniasis.
• While usually spread by sex, some STIs can be spread by non-sexual contact with
donor tissue, blood, breastfeeding, or during childbirth.

• STI diagnostic tests are usually easily available in the developed world, but this is
often not the case in the developing world. The most effective way of preventing
STIs is by not having sex with unknown people. Some vaccinations may also
decrease the risk of certain infections including hepatitis B and some types of HPV.
• Safer sex practices such as use of condoms, having a smaller number of sexual
partners, and being in a relationship where each person only has sex with the
other also decreases the risk. Circumcision in adult males may be effective to
prevent some infections. During school, comprehensive sex education may also be
useful.
• Most STIs are treatable or curable. Of the most common infections, syphilis,
gonorrhea, chlamydia, and trichomoniasis are curable, while herpes, hepatitis B,
HIV/AIDS, and HPV are treatable but not curable. Resistance to certain antibiotics is
developing among some organisms such as gonorrhea.

Chlamydia infection caused
by Chlamydia trachomatis

Gonorrhoea caused by
Neisseria gonorrhoeae

Syphilis caused by
Treponema pallidum

Genital herpes caused by
Herpes simplex virus

HIV-AIDS caused by
Human Immunodeficiency
Virus (HIV)

Genital warts caused by
Human Papillomavirus (HPV)

Trichomoniasis caused by
Trichomonas vaginalis

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