Histology of Male Reproductive System

Petek Korkusuz MD PhD

• To learn histological structure and the histophysiology of male reproductive organs

Aim

Learning Goals

• To learn the histology and histophysiology of two testes • To learn the histology and histophysiology of the genital ducts • To learn the histology and histophysiology of the associated glands: – Paired seminal vesicles – Single prostate glands – Bulbourethral (Cowper) glands • To learn the histology and histophysiology of the penis

Male Genital System • Two testes

testosterone

• Associated glands

..

vesicles glands • Penis...

..

formation of spermatozoa & synthesis, release and storage of

• Genital ducts

formation of noncellular portion of semen

– Paired seminal – Single prostate – Bulbourethral (Cowper) glands

delivery of semen to female reproductive system

Testes

• Paired oval organs, located in the scrotum (approx 4x3x3cm) • Testes develop retroperitoneally, carry a peritoneal outpouching while descending in scrotum: tunica vaginalis • Tunica albuginea (irregular dense connective tissue) surrounds each testis • Tunica vasculosa tissue) located capsule.

(highly vascular loose connective immediately deep to TA forms the vascular

Testes

• The posterior aspect of TA is thickened to form mediastinum testis septa shaped ending .

• The connective tissue radiate from MT to subdivide each testis into approx 250 pyramid lobuli testis.

• Each lobule has 1-4 blindly seminiferous tubules • Richly vascularized and innervated CT. loose connective tissue derived from TV surrounds STs.

• Interstitial cells of Leydig make groups within this

Testes

• Seminiferous epithelium of STs produces spermatozoa . • Spermatozoa enter tubuli recti that connect the open end of each ST to rete testis (labyrinthine spaces within MT). • Spermatozoa leave the RT through ductuli efferentes (10-20 short tubules) which fuse with epididymis .

Testes: vascular supply

• The vascular supply of each testis is derived from testicular artery descending with testis into scrotum with ductus deferens (vas deferens) • The TA give branches before piercing the capsule to form intratesticular elts. • Testicular capillary beds are collected into pampiniform plexus of veins which are wrapped around the testicular artery • Artey, veins and the ductus deferens form the spermatic cord. • PP blood is cooler than TA; reduce the arterial blood temperature ...form a countercurrent heat exchange system. Testes temp is kept lower (35 o C)...spermatozoa develop normally

Seminiferous tubules

• 30-70 cm long, 150-250  m in diameter highly convoluted tubules (total1000 STs in two testes, total length 0.5 km) • Tunica propria (slender CT) and thick • A seminiferous (germinal) epithelium make the wall of ST basal lamina separates SE and the TP • TP contains type 1 collagen bundles housing several layers of fibroblasts (myoid cells in aimals not humans).

• There are spermatogenic cells and the Sertoli cells within the SE. Seminiferous tubules, some of which are outlined, and groups of pale-stained interstitial (Leydig) cells (arrowheads). Pararosaniline—toluidine blue (PT) stain.

Sertoli cells

• Tall columnar cells , with a basal clear oval nucleus and complex infoldings at the apical and lateral cell membranes • Contain cytoplasmic inclusions crystalloids of Charcot-Böttcher with unknown function • Cell cytoplasm is filled with SER, has many mitochondria and a well developed Golgi apparatus.

• Lat. cell membranes of adjacent Sertoli cells form occluding junctions subdividing the lumen of the ST into narrower basal and the wider adluminal compartments a . • The ZOs of Sertoli cells establish blood-testis barrier that isolates the adluminal compartment from CT influences thereby protecting the developing gametes from the immune systeme.

Blood-testis barrier

• Sertoli cells enzymes. • Myoid cells form the blood testis barrier. • Basal compartment the interstitial space and the spaces occupied by the spermatogonia. • Adluminal compartment comprises the tubule lumen and the intercellular spaces down to the level of the occluding junctions (OJ). In this compartment are spermatocytes, spermatids, and spermatozoa. comprises • Cytoplasmic residual bodies from spermatids undergo phagocytosis by the Sertoli cells and are digested by lysosomal surround the seminiferous epithelium.

Sertoli cells function in:

• supporting the developing spermatogenic cells; • establishing the blood testis barrier; • phagocytosis of cytoplasm shed by developing spermatogenic cells; • manufacturing the following substances: androgen binding protein, antimullerian hormone, inhibin, testicular transferrin, and a fructose rich medium.

Spermatogenic cells

•Most of the cells composing the thick seminiferous epithelium are spermatogenic cells in various stages of maturation.

Spermatogonia

, are located in the basal compartment, •Primary spermatocytes,

secondary spermatocytes, spermatids , spermatozoa

occupy the adluminal compartment. •Spermatogonia are diploid cells that undergo mitotic division to form more spermatogonia, primary spermatocytes, which migrate from the basal into the adluminal compartment.

Spermatogenesis

• Primary spermatocytes enter the first meiotic division to form secondary spermatocytes, which undergo the second meiotic division to form haploid cells known as

spermatids.

• Spermatids are transformed into spermatozoa by shedding of much of their cytoplasm, rearrangement of their organelles, and formation of flagella.

• Part of the wall of a seminiferous tubule. Several cells of the spermatogenic lineage are present: a spermatogonium, primary spermatocytes, and young and late spermatids. The approximate limits of a Sertoli cell holding several spermatids are delineated. H&E stain. High magnification.

• Spermatocytes and spermatids in the epithelium of a seminiferous tubule. The tubule is covered by myoid cells..

Spermatids

• Electron micrograph of a mouse spermatid. In the center is the nucleus, covered by the acrosome. The flagellum can be seen emerging in the lower region below the nucleus. A cylindrical bundle of microtubules, the manchette, limits the nucleus laterally. (Courtesy of KR Porter.)

The maturation process (spermatid....spermatozoa)

– Spermatocytogenesis: spermatogonia differentiate into primary spermatocytes – Meiosis: reduction division whereby diploid primary spermatocytes reduce their chromosome complement, forming haploid spermatids – Spermiogenesis: transformation of spermatids into spermatozoa (sperm)

Spermatogenesis

• Diagram showing the clonal nature of the germ cells. Only the initial spermatogonia divide and produce separate daughter cells. • Once committed to differentiation, the cells of all subsequent divisions stay connected by intercellular cytoplasmic bridges . • Only after they are separated from the residual bodies can the spermatozoa be considered isolated cells.

Spermiogenesis

• The occurring during principal in changes spermatids spermiogenesis are demonstrated.

• The basic structural feature of the spermatozoon is the head , which consists primarily of condensed nuclear chromatin.

• The reduced volume of the nucleus affords the sperm greater protect mobility the and genome may from damage while in transit to the egg.

• The rest of the spermatozoon is structurally arranged to promote motility.

• Bottom: The structure of a mature spermatozoon.

Spermatozoon

• Spermatids discard much of their cytoplasm and form a flagellum to become transformed into spermatozoa, a process known as spermiogenesis.

• Spermatozoa (sperm) are long cells (~65 length • Tail μ m), composed of a head, housing the nucleus, and a tail, which accounts for most of its of the spermatozoon is subdivided into four regions: neck, middle piece, principal piece, and end piece . The plasmalemma of the head continuous with the tail’s plasma membrane.

is

Spermatozoon

• Neck (~5

fibers.

μ m long) connects the head to the remainder of the tail. It is composed of the cylindrical arrangement of the nine columns of the connecting piece that encircles the two centrioles, one of which is usually fragmented. The posterior aspects of the columnar densities are continuous with the nine outer dense • Middle piece (~5 μ m long) is located between the neck and the principal piece. It is characterized by the presence of the mitochondrial sheath, which encircles the outer dense fibers and the centralmost axoneme. The middle piece stops at the annulus. Two of the nine outer dense fibers terminate at the annulus; the remaining seven continue into the principal piece.

Spermatozoon

Principal piece End piece

to 1.0 μ (~5 m.

μ (~45 of the middle piece. μ the fibrous sheath. m long) is the longest segment of the tail and extends from the annulus to the end piece. The axoneme of the principal piece is continuous with that Surrounding the axoneme are the seven outer dense fibers that are continuous with those of the middle piece and are surrounded, in turn, by m long) is composed of the central axoneme surrounded by plasmalemma. The axoneme is disorganized in the last 0.5

Spermatozoon

• Scanning electron micrograph of a spermatozoon in the uterine cavity of a rodent. The tufts are ciliated epithelial cells. x2,000.

Leydig cells

• Luteinizing hormone (LH ), anterior pituitary gland, binds to a gonadotropin released from the LH receptors activating cyclic adenosine monophosphate (cAMP ).

kinases on the Leydig cells, adenylate cyclase Activation of the Leydig cells by cAMP induces

esterases

inactive of to form protein

cholesterol

to become active and free cholesterol cleave synthesis is also from intracellular lipid droplets. The first step in the pathway of testosterone LH-sensitive because LH activates

desmolase

, converts free pregnenolone .

the

cholesterol

enzyme cholesterol that into • The various synthetic products pathway are of the shuttled between the smooth endoplasmic reticulum and mitochondria until

testosterone

by these cells .

, the male hormone, is formed and is ultimately released

Leydig cells

• Epithelium of seminiferous tubules surrounded by myoid cells. The spaces between the tubules contain connective tissue, blood and lymphatic vessels, and interstitial cells.

Leydig cells

Interstitial cells and cells of the seminiferous epithelium. H&E stain. High magnification.

Leydig cells

• Electron micrograph of a section of an interstitial cell. There is abundant smooth endoplasmic reticulum as well as mitochondria. Medium magnification.

Hormonal relationships

• Because

FSH

synthesize and blood testosterone levels are not sufficient to initiate and maintain spermatogenesis, induces Sertoli cells to release

androgen-binding protein (ABP

). ABP binds testosterone , thereby preventing the hormone from leaving the region of the seminiferous tubule and local elevating testosterone levels in the sufficiently environment to spermatogenesis.

the sustain

Hormonal relationships

• Release of increased testosterone

LH

is inhibited by levels

dihydrotestosterone

.

of and dihydrotestosterone the hormone secondary

5 α

its

-reductase

more , whereas release of FSH is inhibited by

inhibin

, which is produced by Sertoli cells.

• Testosterone is also required for the normal functioning of the seminal vesicles, prostate, and bulbourethral glands as well as for the appearance and maintenance of the male sexual characteristics. The cells that require testosterone possess , the enzyme that converts testosterone to active form,

Hypophyseal control of male reproduction

• Luteinizing hormone (

LH

) acts on the Leydig cells, • Follicle-stimulating hormone ( hormone,

FSH

) acts on the seminiferous tubules. A testicular

inhibin

in the pituitary. , inhibits FSH secretion

Intratesticular genital ducts

• Tubuli recti • Rete testis

•Connect seminiferous tubules to epididymis

Tubuli recti

• Short, straight tubules delivering spermatozoa from the seminiferous tubules into rete testis.

• Lined by Sertoli cells in their first half near the ST • Formed by seminiferous epithelium, lined by a simple cuboidal epithelium in their second half near the rete testis • Cuboidal cells have short stubby microvilli and most have a single flagellum

Rete testis

• Consists of labyrinthine spaces lined by a simple cuboidal epithelium within the mediastinum testis.

• Cuboidal cells resemble those of tubuli recti; have numerous short microvilli with a single flagellum • Immature spermatozoa pass from tubuli recti into rete testis

Ductuli efferentes

• 10-20 short tubules that drain spermatozoa from the rete testis andpierce the tunica albuginea of testis to conduct the sperm to epididymis • Simple epithelium contains noncilliated cuboidal cells or cilliated columnar cells • Cillia of the columnar cells move the spermatozoa toward the epididimis • Cuboidal cells having many lysososomes and apical plasmolemmal invaginations are responsible of endocytosis (resorb most of the luminal fluid) • Epithelium sits on a separates it from the thin loose CT • CT is surrounded by a thin layer of smooth muscle. BL that wall of each ductule circularly arranged

Extra testicular genital ducts • Epididymis • Ductus deferens • Ductus ejaculatorius

Epididymis

• Secrete numeruous factors that facilitate the maturation of spermatozoa; but spermatozoa cannot fertilize a secondary oocyte untill they undergo of a head, body and tail • The lumen is lined by . capacitation ; a process trigered by secretions produced in female genital system.

• Is a thin, long (4-6 m), highly convoluted tubule consisting pseudostratified epithelium composed of two cell types: short basal cells functioning as stem cells and the tissue by a BL with round nuclei tall principal cells • Circularly arranged smooth muscle cells spermatozoa to the ductus deferens.

with basally located oval nuclei and stereocillia, resorbing the luminal fluid and manifacturing glycerophosphocholine (a glycoprotein that inhibits spermatozoon capacitation preventing spermatozoon from fertilizing a secondary oocyte untill the sperm enters the female genital tract) • Epith is separated from the underlying loose coonective surround the CT layer. Peristaltic contractions of this layer help conduct the

Epididymis

• Highly coiled ductus epididymidis, sectioned several times. • Its wall is made of a pseudostratified columnar epithelium surrounded by connective tissue and smooth muscle. • Inset: Higher magnification of the epithelial cells with their long microvilli (stereocilia).

Ductus deferens (Vas deferens)

• Each DF is a thick walled muscular tube with a small irregular lumen that conveys the spermatozoa from the tail of the epididimis to the ejaculatory duct. • Mucosa of tissue formed by pseudostratified columnar epithelium (principal cells are shorter) with stereocilia and a lamina propria smooth muscle . • Thick outer wall is formed of (three layers:inner outer longitudunal middle circular) and collagen fibers (blue).

• SML isinvested by a thin layer fibroelastic connective

Extra testicular genital ducts

• The dilated terminus of each ductus deferens is known as ampulla • As the ampula approaches the prostate gland it is joined by seminal vesicle .

• The continuation of the junction of the ampulla with the seminal vesicle is known as ejaculatory duct .

Ejaculatory duct

• Ampulla of ductus deferens joins the seminal vesicle to form ejaculatory duct; which then enters the prostate gland and opens in the prostatic urethra at the colliculus seminalis • Lumen is lined by columnar epithelium .

• Is a short straight tubule simple • Subepithelial CT is folded • Has no smooth muscle its wall.

in

Accessory genital glands

• Paired seminal vesicle • Single prostate gland • Paired bulbourethral glands

Seminal vesicles

• About 15 cm long highly tubular structures located between post aspect of the neck of the bladder and the prostate gland; and join the ampulla of the ductus deferens just above the prostate gland • Its mucosa is highly convoluted that are observed to open into a central lumen.

• Lumen is lined by a pseudustartified columnar epithelium (short basal cells and low columnar) • Each columnar cell cell-with numerous short microvilli and a single flagellum • Subepithelial fibroelastic CT forming labyrinth-like cul-de-sacs is surrounded by inner circular outer longitudinal smooth muscle coat • SM is surrounded by lipochrome pigment fibroelastic CT the enery for the spermatozoa. again • This gland produces a viscose yellow fructose rich seminal fluid that makes 70% of the volume of the semen. It is the source of • The characteristic pale yellow colour of semen is due to the released by seminal vesicles

Seminal vesicles

• Tortuous tubular gland with a much folded mucosa gives the impression that the gland consists of many tubules.

Prostate

• Is the largest of the accessory glands, is pierced by the urethra and the ejaculatory ducts.

• Slender composed

capsule

of a is richly vascularized, dense irregular dense connective interspersed

muscle cells.

with • Connective tissue tissue

smooth stroma

of the gland is derived from the capsule and is, therefore, also enriched by smooth muscle fibers in addition to their normal connective tissue cells.

• Is a conglomeration of 30 to 50 individual

compound tubuloalveolar glands

concentric layers submucosal, and main.

, • is arranged in three discrete, mucosal,

Prostate

• Mucosal glands are closest to the urethra and thus are the shortest of the glands • Submucosal glands glands. the glands are the peripheralmost prostate.

to oval

(corpora amylacea),

composed of calcified are peripheral to the mucosal glands and are consequently larger than the mucosal • Largest and most numerous of

main glands

which compose the bulk of the • Lumina of the tubuloalveolar glands frequently house round

prostatic concretions

glycoproteins, whose numbers increase with a person’s age.

,

• Distribution of its glands in 3 zones. The gland ducts open into the urethra.

Prostate

• Section of the central region of the prostate showing the prostatic urethra and tubuloalveolar glands surrounded by connective tissue and smooth muscle.

Prostate

Prostate

• Components of prostate gland are lined by a

simple to pseudustratified to columnar epihelium

muscle. ; surrounded by connective tissue and smooth

Prostatic secretion

• Constitutes a part of semen.

• Is a serous, white fluid rich in lipids, proteolytic enzymes, acid phosphatase, fibrinolysin, and citric acid.

• Formation, and release regulated synthesis, of the prostatic secretions are by

dihydrotestosterone

, the active testosterone form of

Bulbourethral (Cowper’s) glands

• Paired small (3-5 mm diam) glands located at the root of penis, just just at the beginning of membranous urethra • Capsule contains fibroblasts, smooth and skeletal muscle cells (sk muscle derived from the muscles of the urogenital diaphragm) • Capsule sends septa dividing each gland into lobules • Epith of these compound tubuloalveolar glands varies from simple cuboidal to simple columnar • The secretion is a thick slippery fluid that lubricate the lumen of the urethra

Penis

• Is composed of three columns of

erectile tissue

, each enclosed by its own dense, fibrous connective tissue capsule, the

tunica

albuginea.

• 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 .

• 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.

Penis

• Three tissue

corpora

by a common loose connective hypodermis, and are covered by thin skin.

sheath, • Skin continues distal to the glans penis to form a retractable sheath, the

prepuce

individual is circumcised, it is the prepuce that is removed.

• Erectile tissue are surrounded but no . When an of the penis contains shaped, numerous endothelially variably lined spaces.

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

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

Penis