HistologyLecture 21 Male Reproductive System

Male Reproductive System

Male reproductive system is consists of

Testes

Genital ducts Intratesticularextratesticular

Accessory glands Seminal vesicles prostate gland

bulbourethral glands (of Cowper) Copulatory organ

Penis

TestisReproductive functions (produce sperm)

Endocrine functions (produce testosterone)

Tunica vaginalis is a peritoneal outpouching that form a serous cavity that partially surrounds testis

Dense irregular connective tissue capsule: tunica albuginea with fibrous incomplete septa divide testis into about 250 lobules

Deep to tunica albuginea is a layer of loose highly vascular CT known as tunica vasculosa

Each lobule has 1-4 seminiferous tubules with surrounding loose connective tissue, vessels and interstitial cells of Leydig

Sperm produced by seminiferous tubule

Testosterone produced by Leydig cells

Seminiferous Tubule

Each tubule has 150-250 µm diameter, 30-70 cm long; over 250 m in each testis

Each tubule composed of a CT layer known as tunica propria and a Stratified epithelium known as seminiferous epithelium

Epithelium has 2 major cell types Sertoli cells (supporting cells)

Spermatogenic cells

Tunica propria composed of collagen type I, several layer of fibroblasts and myoid cells(not in humans)

A prominent basal lamina separate tubules from each other

End of each seminiferous tubule changes to cuboidal epithelium of tubuli recti, leading to rete testis, efferent ducts and then epididymis

Spermatogenic Cells

4-8 layers of cells dividing by mitosis and meiosis to produce spermatozoa

3 phases of spermatogenesis

spermatocytogenesis: spermatogonia divide by mitosis giving rise to primary

spermatocytes

Meiosis: primary spermatocytes go through meiotic divisions giving rise to

haploid spermatids

spermiogenesis: spermatids differentiate into spermatozoa

Spermatogonia Spermatogonia are small and diploid cells,12 µm

diameter that lie on basal lamina

Spermatogonia are three categories consist of:

Type A spermatogonia continue dividing; flattened oval nucleus light and dark

types )))))Dark Type A: are reserve cells when

divide form additional dark type A and pale type A )))))Pale type

A: have abundant euchromatin, divide and form additional pale type A and type B

spermatogonia

Type B spermatogonia undergo meiosis; round nucleus, differentiate into primary

spermatocytes

Spermatocytes & Spermatids

Primary spermatocytes are largest cells of seminiferous epithelium with clumped chromatin in nucleus

Prophase of first meiotic division lasts for 22 days

Secondary spermatocytes are small, short-lived cells with heterochromatic nuclei

by second meiotic division give rise to spermatids,

Spermatids undergo spermiogenesis to form spermatozoa

Spermatid

Spermatids are small, round haploid cells

All spermatid which are developing from a single pale type A spermatogonium are connected to one another by cytoplasmic bridges

They are located near the lumen of seminiferous tubule

Spermatids accumulate hydrolytic enzymes in an acrosomal granule, rearrange and reduce the number of their organelles and form a flagella and transformed to spermatozoa

This process is called spermiogenesis and has 4 phases include of Golgi, Cap, Acrosomal, and Maturation phases

Timing of Spermatogenesis

Human seminiferous epithelium reveals 6 characteristic of identical cell associations known as stages of spermatogenesis

One cycle of the seminiferous epithelium is 16 days interval in the same stage of spermatogenesis

For a spermatogonium to be transformed to a spermatozoa 4 cycles must occur ( 64 days )

64 days required for cell to go from spertogonia to spermatozoa

The same stage of seminiferous epithelium continues to reappear at specific distances along the length of the tubule

The distance between two identical seminiferous epithelium is known as wave of the seminiferous epithelium

In human there is 6 repeating wave

Different seminiferous tubules will be at different stages of differentiation

Spermatozoa may be present in some tubules and predominantly spermatids or primary spermatocytes in others

Sertoli Cells Elongated columnar supporting cells with base at basal

lamina and apex near lumen of seminiferous tubule

Lateral complex infoldings surround spermatogonia and spermatocytes

Lateral cell membranes of adjacent sertoli cells form occluding junction with each other that establish Blood Testis Barrier

Tight junctions subdivide lumen into two compartments basal and adluminal

Nucleus basally located, euchromatic and with distinct nucleolus

Cytoplasm houses inclusion products known as crystalloids of Charcot-Böttcher

Functions of Sertoli Cells Support and nourish cells of seminiferous tubule

Establishment of blood testis barrier and protecting new developing gametes from immune system

No vasculature inside tubule so sertoli cells transport nutrients to lumenal region

Phagocytose cast-off cytoplasmic droplets from spermatids

Secrete fructose rich fluid into lumen that helps sperm flow in genital ducts

Produce androgen binding protein (ABP)

Produce inhibin which decreases FSH release by pituitary, slowing spermatogenesis

Syntesis of antimüllerian hormone during embryogenesis

Synthesis and secretion of testicular transferrin that conveys iron to gametes

Interstitial Tissue

Between seminiferous tubules are vessels, nerves,

fibroblasts and other connective tissue cells which is

collectively called tunica vasculosa

After puberty interstitial cells of Leydig differentiate

and produce testosterone

Leydig cells are eosinophilic and have lots of SER and

mitochondria with tubular cristae, lipid droplets and

other characteristic of a steroid producing cell

The cytoplasm contains crystallized proteins known as

crystals of Reinke

Intratesticular Genital Ducts

Intratesticular duct system connect seminiferous tubules to epididymis

These ducts are:

Tubuli recti (straight tubules)

Rete testis

Efferent ducts

Tubuli Recti

Short segment of duct at the end of seminiferous tubules

Lined by Sertoli cells that change to simple cuboidal epithelial cells at its

second half near rete testis

Cuboidal cells have short stubby microvilli and a single flagellum

High glycogen amount in some species

Connective tissue sheath support the tubuli

Rete Testis

Branched network of channels lined with simple cuboidal

epithelium

Some cells ciliated and have a single flagellum

Surrounded by connective tissue of mediastinum

Efferent Ducts 10 – 20 short tubule that pierce tunica albugina

Tubules with nonciliated cuboidal cells alternating

with region of ciliated columnar cells giving a

scalloped look to epithelium

Nonciliated cells absorb fluids secreted by

seminiferous tubule cells by endocytosis

Beating of cilia helps sperm movement

Thin loose CT surrounded by a layer of smooth

muscle cells that are circularly arrayed

Lead to epididymis

Excretory Genital Ducts

Excretory or extratesticular ducts are:

Ductus epididymis

Vas deferens

Ejaculatory duct

Ductus Epididymis Highly coiled tube 4-6 m long

Pseudostratified columnar epithelium with stereocilia

Rounded basal cells or stem cell with dense nuclei

Columnar principal cells with pale nuclei and stereocilia

Columnar principal cells have many stereocilia, pinocytotic and coated vesicles, RER, and well developed golgi apparatus

Thin connective tissue layer with underlying circularly arrayed smooth muscle

Secretions preserve sperm capacitation

Phagocytosis of residual bodies and resorbtion of luminal fluid

Smooth muscle contractions for peristalsis to move sperm through the tubule

Ductus (Vas) Deferens

Straight tube from epididymis to ejaculatory duct

Narrow folded lumen with thick smooth muscle layer

Epithelium is pseudostratified columnar with stereocilia but principal cells are shorter

Lamina propria with loose fibroelastic connective tissue and vessels

Smooth muscle layer has inner longitudinal, middle circular and outer longitudinal layers

Smooth muscle layers surround by a thin layer of connective tissue

Dilated region, ampulla, has highly folded, thickened epithelium

Ejaculatory duct

A short straight tubule that enter prostate gland

The lumen lined by simple columnar

epithelium

Subepithelial connective tissue which is folded

support the epithelium

Ejaculatory duct has no smooth muscle cells in

its wall

Spermatic Cord

Testicular artery

Pampiniform (venous) plexus

Nerves

Ductus deferens

Surrounded by skeletal muscle, the cremaster muscle

Accessory Genital Glands

Paired seminal vesicle

Single prostate

Paired bulbourethral (Cowper’s) glands

Seminal Vesicle

Highly coiled tubular structures, 15 cm long

Duct joins with ductus deferens at prostate

Folded epithelium with pseudostratified columnar epithelium

Rounded basal cells and low columnar cells

Low columnar cells have short microvilli and a single flagellum, RER, golgi

apparatus, numerous mitochondria, lipid and lipochrome droplets, and many

secretory granules

Seminal Vesicle

Lamina propria is a fibroelastic CT

Thin smooth muscle layers, inner circular, outer longitudinal

Viscous yellowish fructose-rich secretion making up 70% of ejaculate volume

Pale yelloish color is due to lipochrome released by the seminal vesicle

Prostate Capsule is composed of richly vascularized dense irregular

CT interspersed with smooth muscle

Stroma is derived from capsule and has smooth muscle cells in addition to normal CT cells

30-50 individual compound tubuloacinar glands with ducts leading to prostatic urethra

Gland arranged in three separate concentric layers *mucosal gland *submucosal gland *main gland

Epithelium is simple columnar or pseudostratified columnar cells with organelles endowed in protein synthesis

Prostate

Prostatic fluid stored for release during ejaculation

Secretions is a serous white fluid include amylase,

proteases, acid phosphatase and lipids

Prostatic concretions (Corpora Amylacea) found in

gland lumens increase with age, function unknown

They are composed of calcified glycoproteins

Past age 40 glands hypertrophy which can lead to

urethral blockage or cancer

Bulbourethral (Cowper’s) Glands

Its fibroelastic capsule contains smooth muscle cells as well as skeletal muscle fibers derived from urogenital diaphragm

Compound tubuloacinar glands with simple cuboidal to simple columnar

Gland acini surrounded by smooth muscle

Secretion is clear mucous released during sexual arousal for lubrication

Penis 3 cylindrical masses of highly vascularized erectile tissue

2 corpora cavernosa are dorsal

1 corpus spongiosum is ventral and surrounds urethra

Each of them enclosed by dense fibrous CT known as tunica albugina

corpus spongiosum end as a bulbous portion known as glans of penis

A common loose CT sheath surrounding all three corpora

Outer covering is skin

Skin form a retractable sheath over glans which is called prepuce

Prepuce lined by nonkeratinized stratified epithelium

Penis

Erectile tissue consists of venous spaces lined by

unfenestrated endothelium and separated by septa of

connective tissue and smooth muscle

Septa of corpus spongiosum has more elastic fiber and

less smooth muscle

Capillary plexus in septa supply some blood to

vascular spaces

The main source of blood during erection that flow

into spaces are from helical arteries

Blood flows into venous spaces during erection and

smooth muscle contraction slows outflow of blood

Urethra

15 – 20 cm long in male

Prostatic urethra 3- 4 cm long located in prostate, and is lined by transitional epithelium

Membranous urethra 1-2 cm long, it is pass through urogenital diaphragm, is lined by stratified columnar with patches of Pseudostratified columnar epithelium

Spongy urethra(Penile) 15 cm long, is lined by stratified columnar with patches of pseudostratified columnar epithelium

In the glans (the navicular fossa) it is lined by stratified squamous

Mucous glands of Littre found along urethra in lamina propria and subepithelial loose connective tissue

HR Mahmoudzadeh Sagheb

Z Heidari

MH Noori Mugahi

Department of Histology