male reproductive system 1

Introduction: Male Reproductive

System

Male Reproductive System is responsible for:

• Production, nourishment and temporary storage of the haploid male gametes(spermatozoa)

• Suspension of spermatozoa to the female genital system

• Production of male sex hormones

Male Genital System Comprises:

• Testes- produce spermatozoa, synthesize and secrete androgens

Epididymis, Vas deferens, Ejaculatory duct and part of male urethra- forming ductal

system for the carriage of spermatozoa to the exterior

• Seminal Vesicles, Prostate Gland and Cowper’s Gland- providing fluid nutrients to nourish spermatozoa

Cowper’s gland

• Penis- a biological feature of male animals including both vertebrates and invertebrates.

- It is a reproductive, intromittent organ(capable of delivering sperm) that additionally serves as the urinal duct in placental mammals.

Penile erection • physiological phenomenon where

the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal.

SPERMATOGENESIS

• process by which male primary germ cells undergo division, and produce a number of cells termed spermatogonia, from which the primary spermatocytes are derived.

• Each primary spermatocyte divides into two secondary spermatocytes, and each secondary spermatocyte into two spermatids or young spermatozoa.

• These develop into mature spermatozoa, also known as sperm cells.

• Thus, the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa

 ACCESSORY GLANDS OF THE MALE REPRODUCTIVE TRACT

Seminal Vesicles

• Function secrete a significant proportion of the fluid that ultimately 

becomes semen

 Lipofuscin granules from dead epithelial cells give the secretion its yellowish color.

About 50-70% of the seminal fluid in humans originates from the seminal vesicles, but is not expelled in the first ejaculate fractions which are dominated by spermatozoa and prostatic fluid.

Seminal vesicle fluid is alkaline, resulting in human semen having a mildly alkaline pH

• Description:– A pair of diverging saccular structures

– About 5cm in length behind neck of bladder and between the ampullae of ductus deferens above, and the prostate gland, below

– Their lower ends taper to a narrow straight duct that opens into the ampullae of the ductus deferens where these continue as the ejaculatory ducts

– Wall of the vesicles is composed of connective tissue capsule with an underlying layer of smooth muscle

– A plexus of sympathetic nerve fibers and small ganglia can be found on the vesicle wall

Structure:

– coiled or convoluted tube with numerous diverticula along its length resulting in a lumen of labyrinth complexity

– in sections, the mucosa forms thin folds from which secondary and tertiary folds project into the lumen

– however, all of these recesses open into a wider central portion of the lumen

– pseudostratified epithelium has low columnar or cuboidal cells with smaller numbers of rounded cells between their bases

– surface of epithelium bears microvilli

– some of the cells have a single flagellum projecting into the lumen from a pair of centrioles in their cytoplasm

– they contain numerous slender mitochondria, well-developed granular endoplasmic reticulum and abundant secretory granules

– small lipid droplets and aggregations of lipochrome pigment are commonly found in the basal cytoplasm

– (pigment first appears at puberty; may be sufficiently abundant in older adults to give the interior of the vesicles a brownish color in the fresh state)

Did you know that..Before: Seminal vesicles were thought to be

reservoirs for storage of semen (and this statement is wrong because although

their secretion accounts for the greater part of the volume of the ejaculate, spermatozoa are not normally found in their lumen. There are some considerable species differences in the consistency of their secretion, but usually described as a clear, viscous, gelatinous fluid)

Prostate

• Composed of secreting glands that open into the urethra

• These prostatic glands and ducts are embedded in a supporting stroma of fibroblasts, collagen and smooth muscle

Functions:• to store and secrete a slightly alkaline fluid, milky or

white in appearance

• The fluid usually constitutes 20-30% of the volume of the semen along with spermatozoa and seminal vesicle fluid.

• alkalinity of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm.

• Secretion of prostate contains acid phosphatase, amylase and fibrinolysin

Description:

– largest of the accessory glands in males

– its sectretion together with the seminal vesicle contributes to the volume of ejaculation

– size: horse chestnut

Zones:                        Lobes:

Zone(often used in Pathology) Description

Peripheral zone (PZ) The sub-capsular portion of the posterior aspect of the prostate gland that surrounds the distal urethra. It is from this portion of the gland that ~70-80% of prostatic cancers originate

Central zone (CZ) This zone surrounds the ejaculatory ducts. Accounts for roughly 2.5% of prostate cancers although these cancers tend to be more aggressive and more likely to invade the seminal vesicles.

Transition zone (TZ) ~10-20% of prostate cancers originate in this zone.  Surrounds the proximal urethra and is the region of the prostate gland that grows throughout life and is responsible for the disease of benign prostatic enlargement

Anterior fibro-muscular zone (or stroma) This zone is usually devoid of glandular components, and composed only, as its name suggests, of muscle and fibrous tissue.

– surrounds urethra at its origin from the urinary bladder

– around the gland: thin capsule formed by dense connective tissue and extends into it as its stoma

– capsule and stoma: both contain smooth muscle, fibroblasts and collagen

– compound tubuloacinar glands are arranged in concentric zones

– 30-40 short glands (around urethra) discharge their secretion through separate openings on either side of colliculus seminalis: Mucosal Glands

– Peripheral to these is a zone of longer, branching submucosal glands(sharing a smaller number of ducts)

– Outside of these are the main glands( make up the greater part of the prostate)

Tubuloacinar Units

– Sometimes narrow or wider in form: variable

– Branching folds or papillae of the mucosa project into the lumen

– Epithelium: simple or pseudostratified columnar but may be reduced to low cuboidal or squamous in

dilated or cystic dilatations

– Cells contain abundant rough ER, numerous secretory granules

In the Lumen of Glands:• Corpora Amylacea or Prostatic Concretions- ovoid

or spherical bodies- These are glycoprotein in composition- May become a site of calcium in deposition- More common in prostate of older men- No known significance

Bulbourethral Glands• Cowper’s glands*a neglected gland

• Paired

• Partially embedded in the muscle of urogenital diaphragm

• Compound tubuloacinar glands

• Less than 1cm in diameter

• Each open by a single duct into the floor of proximal portion of the cavernous urethra

Functions:

• each gland produces a clear, viscous secretion during sexual arousal, known as pre-ejaculate

• helps to lubricate the urethra for spermatozoa to pass through

• neutralizing traces of acidic urine in the urethra• helps flush out any residual urine or foreign 

matter*the fluid is capable of picking up sperm

Glands

• Branched and distorted tubules ( blind ends usually dilated to form alveoli

• Ampullae: tubules comprising the small lobules of the gland that converge on wider channels

• Duct arises from confluence of the ampullae of several lobules

• Prominent connective tissue partitions between the lobules have collagenous and elastic fibers; also both striated and smooth muscle fibers

• They are lined by tall, mucus secreting epithelium

Small ducts and Ampullae

• Lined by cuboidal or columnar epithelial cells

• Lumenal surface: irregular with short microvilli

• Basolateral surfaces: corrugate and interlock with similar irregularities on adjacent cells

• Epithelium: with patches of mucous cells

• In the apical cytoplasm: few cells of electron-dense secretory granules (resembling serous cells)

• Larger excretory ducts: lined by pseudostratified epithelium (with patches of mucous cells may be found)

Secretion

• emitted at the onset of ejaculation and makes a small contribution to the initial fraction of the semen

• Clear, mucus-like, viscous fluid

• Can be drawn out into a long thin thread on contact

• Said to have a lubricant function

SUMMARYSTRUCTURE LOCATION EPITHELIUM

PROSTATE Surrounds urethra at urinary bladder

Varies from CUBOIDAL to PSEUDOSTRATIFIED COLUMNAR CELLS arranged in alveoli resting on distinct basement membrane; lamellated concretions are prominent(especially in older men

SEMINAL VESICLE Posterior to prostate SIMPLE or PSEUDOSTRATIFIED COLUMNAR CELLS resting on thin basement membrane; mucosa is highly folded

BULBOURETHRAL Posterior to membranous urethra

Most alveoli consist of CUBOIDAL to COLUMNAR CELLS with mucin droplets; typical mucous glandular epithelium

STRUCTURE EPITHELIUM SMOOTH MUSCLE

CONNECTIVE TISSUE

FUNCTION(S)

PROSTATE -Many rER profiles with dilated cisternae-large Golgi complex-Few mitochondriaand lysosomes

Fibers in capsule and stroma surrounding the many tubuloalveolar glands

Abundant fibroelastic tissue in capsule and septa

-Produces and stores prostatic fluid w/c makes up most of the semen-May stimulate motility of sperm

SEMINAL VESICLE -cytoplasm dominated by rER profiles-large Golgi complex-many small electron-dense granules

Moderately thick inner circular and outer longitudinal layers

-Fibrous -Thin capsule with many elastic fibers-Lamina propia rich in elastic fibers 

-Provides nutrients for sperm (esp fructose)

BULBOURETHRAL GLAND

Limited to thin circular layer surrounding large excretory ducts

Thin fibrous capsule with septa which subdivide gland into lobules

-Supply mucus to lubricate lumen of urethra during erotic stimulation

Penis• the external sex organ of the male through 

which both urine and semen pass• Thin skin

• is composed of three columns of erectile tissue, each enclosed by its own dense, fibrous connective tissue capsule, the tunica albuginea.

• Superficial to the tunica is an outer sheath of connective tissue, the penile fascia

• Two of the columns of erectile tissue, the corpora cavernosa, are positioned dorsally; their tunicae albugineae are discontinuous in places, permitting communication between their erectile tissues. 

• Third column of erectile tissue, the corpus spongiosum, is positioned ventrally. Because the CS houses the penile portion of the urethra, it is also called the corpus cavernosum urethrae. 

Penis• CS ends distally in an enlarged, bulbous portion, the glans penis 

(head of the penis). The tip of the glans penis is pierced by the end of the urethra as a vertical slit.

• Three  corpora  are  surrounded  by  a  common  loose  connective tissue sheath, but no hypodermis, and are covered by thin skin.

• Skin  continues  distal  to  the  glans  penis  to  form  a  retractable sheath,  the prepuce. When an  individual  is  circumcised,  it  is  the prepuce that is removed.

• Erectile tissue  of  the  penis  contains  numerous  variably  shaped, endothelially lined spaces.

• Vascular spaces of the corpora cavernosa are  larger centrally and smaller peripherally, near the tunica albuginea. 

• Vascular  spaces  of  the  corpus  spongiosum  are  similar  in  size throughout its extent. 

•  

Corpus spongiosum

• At its end the corpus spongiosum expands, forming the glans

 • penile urethra is lined with 

pseudostratified columnar epithelium. 

•  Small mucus-secreting urethra glands (glands of Littre) are found along the length of the penile urethra.

•  In uncircumcised men the surface of the glans is covered by the prepuce or foreskin, a retractile fold of thin skin with sebaceous glands in the internal fold.

 Glans penis• In the glans, it becomes 

stratified squamous epithelium continuous with that of the thin epidermis covering the glans.

• Consist of dense connective tissue containing a plexus of of large anastomosing veins with both circular and longitudinal smooth muscles in their walls.

• Covered by a fold of skin called the prepuce

• Histology of the Glans and prepuce:• keratinized squamous epithelium.• Histology of the erectile tissue:• the corpora contain septa of smooth 

muscle, which form bizarrely shaped cavities. Vascular endothelium lines the septa and cavities. The afferent arteries for the erectile tissue possess a strong muscularis.

 Levels of the Glans • Epithelium• Lamina Propria• Corpus Spongiosum• Tunica Albuginea *• Corpus Cavernosum *

Epithelium• Both circumcised and intact 

(uncircumcised) men have partially keratinized stratified squamous epithelium five to sixlayers thick

Lamina Propria• In the glans, the loose connective 

tissue of the penile fascia and the fibrous tunica albuginea are lacking so that the lamina propria adheres firmly to the underlying corpus spongiosum

Corpus spongiosum.The interstitial fibrous connective tissue is more abundant and contains more elastic fibers than in the corpus cavernosum.

Prepuce• covers the glans penis. • This is the skin that is cut 

away when a circumcision is done.

• Anatomic Levels of the Foreskin– Epidermis– Dermis– Dartos– Lamina propria– Epithelium

prepuce

• The outside of the foreskin is a continuation of the skin on the shaft of the penis, but the inner foreskin is a mucous membrane like the inside of the eyelid or the mouth

•  Smooth muscle fibres keep it close to the glans but make it highly

• The presence of Meissner's corpuscles (a type of nerve ending) has been reported. elastic

epidermis • consists of a keratinized stratified squamous 

cell epithelium

dermis of the foreskin• consists of connective tissue with blood 

vessels and nerve bundles. Meissner corpuscles are present in the dermal papillae and a few Vater-Pacini corpuscles in deeper areas. 

dartos • consists of smooth muscle fibers invested 

with elastic fibers,

lamina propria, or chorion, • is composed of a vascular connective tissue 

looser than the glans lamina propria. squamous epithelium • which is identical to and a prolongation of the 

glans and coronal sulcus' epithelia except that the basal layer shows a progressive pigmentation toward the free edge of the foreskin where it reaches the skin epidermis.

Figure 38.13 Full-thickness of the foreskin showing all five layers: keratinized stratified squamous epithelium ( top ), dermis, dartos, submucosa, and squamous epithelium of the mucosal portion ( bottom ).

Microscopic and Immunohistochemical FeaturesThe male foreskin is formed by a midline collision of ectoderm, neuroectoderm, and mesenchyme, resulting in a pentalaminar structure ( 8 ). There are five layers in the histologic evaluation of the foreskin ( Figure 38.13 ):•The epidermis consists of a keratinized stratified squamous cell epithelium that is similar to the epidermis seen in the cutaneous tegument. Melanocytes, Langerhans cells, and Merkel cells are also present. Compared to the mucosal epithelium, the epidermis is thinner with better developed rete ridges and usually a pigmented basal layer (Figure 38.14 ). Vellous hairs, sebaceous, and sweat glands may be seen connected to the epidermis.

Corpora cavernosa• Sponge-like system of irregular shaped 

vascular spaces fed by afferent arteries and veins 

• covered by a resistant layer of dense connective tissue, the tunica albuginea 

• Between the lower surfaces of the corpora cavernosa there is  a deeper groove occupied by the corpus cavernosum urethrae

• The corpora cavernosa and the corpus spongiosum are both composed of erectile tissue, which contains a large number of venous cavernous spaces lined with endothelial cells and separated by trabeculae of connective tissue fibers and smooth muscle cells.

Tunica albuginea

• Thinner in the corpus cavernosum urethrae

• Has circularly arranged smooth muscles cells in the inner layer , longitudinally in the outer layer

• Forms a fibrous partition between the two corpora cavernosa

• Has elastic fibers

Skin covering the Penis 

• Thin • Abundant subcutaneous 

layer containing some smooth muscles

• Devoid of hair • Limited number of sweat 

glands

The Penis

MECHANISM OF ERECTION 

• Penile erection involves filling the cavernous spaces of the corpora cavernosa and corpus spongiosum with blood.

• Initiated by external stimuli to the CNS and is controlled by autonomic nerve input to smooth muscle in vascular walls of the penis

MECHANISM OF ERECTION • Parasympathetic stimulation relaxes 

muscle in the trabeculae and dilates the helicine arteries, leading to increased blood flow into the cavernous spaces. 

• The filled spaces compress the venules and veins against the dense tunica albuginea, blocking outflow of the blood and producing tumescence and rigidity in the cylinders of erectile tissue.

•  Beginning with ejaculation, the firing of sympathetic nerves stimulates constriction of the helicine arteries, decreasing blood flow into the spaces, lowering the pressure there and allowing the veins to open and drain most blood from the erectile tissue.

•