HISTOLOGY of

MALE REPRODUCTIVE SYSTEM

Mr. Babatunde, D.E.

Male Reproductive System

❖ Consists of the testes contained in the scrotum, the genital ducts and their associated glands (accessory glands) and the penis.

❖ Testes function to produce spermatozoa (sperm) and to synthesize the hormone testosterone.

❖ Major accessory glands include the paired seminal vesicles and the single prostate gland.

❖ Minor accessory glands include the two bulbourethral glands located at the root of the penis.

❖ Accessory glands function to manufacture the fluid portion of the semen, which transports and nourishes the spermatozoa as they pass through the excretory ducts.

❖ Penis is the male copulatory organ that delivers spermatozoa into the female reproductive tract and serves as a conduit for excretion of urine from the body.

Menbranous urethra

Urethra

Penis

Corpus cavernosum

of the penis

Corpus cavernosum

of the urethra

Prepuce Glands penis

Testicular lobule

Tunicia albuginea

Tunicia vaginalis

Tubuli recti Rete testis

Bladder

Prostate

Ampulla

Seminal vesticle

Ejaculatory duct

Bulbourethral gland

Ductus deferens

Ductus epididymids

Ductus efferentes

Epididymis

Mediastinum

testis

Fig 22-1 (Text)

Testes

Testis

❖ Is an ovoid body, about 4 to 5cm long, that is

housed within the scrotum.

❖ Develops retroperitoneally in the abdominal

cavity and descends into the

scrotum,carrying parietal and visceral layers

of the peritoneum (the tunica vaginalis) that

partially cover the testis on its anterior and

lateral surfaces.

Tunica albuginea Seminiferous epithelium

Seminiferous tubules

septum

Blood vesselLumen

Seminiferous

tubulesSeminiferous

epithelium

Tunica

vasculosaTunica albuginea

Tunica albuginea

Tunica

vasculosa

Seminiferous

tubules

Tunica Albuginea

❖ Is the thick fibrous connective tissue capsule of

the testis.

❖ Is thickened posteriorly to form the

mediastinum testis from which connective

tissue septa arise to divide the organ into

approximately 250 compartments (lobuli

testis).

Lobule Testis

⚫ Are pyramidal-shaped incomplete

compartments that intercommunicate.

⚫ Contain from 1 to 4 seminiferous tubules each,

embedded in a meshwork of loose connective

tissue where nerves, vessels, and scattered

interstitial cells of Leydig are present.

Tunica albuginea Seminiferous epithelium

Seminiferous tubules

lobule

Interstitial Cells of Leydig

❖ Are located in the interstitial spaces between the seminiferous tubules.

❖ Mature and begin to secrete during puberty and are richly supplied with capillaries and lymphatic vessels.

❖ Are round to polygonal in shape, possessed a large central nucleus, many mitochondria, a well-developed Golgi apparatus, smooth endoplasmic reticulum, and many lipid droplets.

❖ Are endocrine cells that produce the male sex hormone testosterone, when stimulated by luteinizing hormone (interstitial cell stimulating hormone) from the pituitary gland.

Figure 22–8. Interstitial cells and cells of the seminiferous epithelium.

H&E stain. High magnification.

Interstitial cells

Spermatogonium

Blood vessel

Sertoli cell

Primary spermatocytes

Figure 22–3. Epithelium of

seminiferous tubules

surrounded by myoid cells.

The spaces between the

tubules contain connective

tissue, blood and lymphatic

vessels, and interstitial cells.

PT stain. Medium

magnification.

Connective

tissue

Interstitial

cells

Myoid

cells

Figure 22–14. Electron micrograph of a section of an interstitial cell. There is

abundant smooth endoplasmic reticulum as well as mitochondria. Medium

magnification.

Seminiferous Tubules❖ Are the sites where spermatozoa are produced.❖ Are 30 to 70 cm long, with a diameter of 150 to 250

um.❖ Are lined by a complex, stratified epithelium.❖ Are enveloped by a fibrous connective tissue tunic,

composed of several layers of fibroblasts. Myoid cells, resembling smooth muscle, are present in the inner layer of some species.

❖ Form tortuous pathways through the organ before they become continuous with the short straight tubuli recti.

Figure 22—6.

Spermatocytes and

spermatids in the

epithelium of a

seminiferous tubule. The

tubule is covered by

myoid cells. Picrosirius-

hematoxylin (PSH) stain.

Medium magnification.

Tubuli Recti

❖ Have a narrow lumen lined by a simple cuboidal epithelium.

❖ Lead into the rete testis, a network of epithelial-lined channels located in the mediastinum.

Seminiferoustubules

Tubuli rectiConnective tissue

Mediastinum testis

EpitheliumRete testis

Ductuli Efferentes

❖ Lead from the rete testis into the epididymis.

Epithelium

Ductuli efferentes

Connective tissue

Spermatozoa

Spermatozoa

Ductuli EfferentesRete testis

Seminiferous Epithelium

❖ Is composed of two different types of cells, the

spermatogenic cells from which the germ cells

eventually develop and the Sertoli cells, which

support and provide nutrition to the

spermatogenic cells.

❖ Is 4 to 8 cell layers thick.

Figure 22–4. Part of a seminiferous tubule with its surrounding tissues. The

seminiferous epithelium is formed by 2 cell populations: the cells of the

spermatogenic lineage and the supporting or Sertoli cells.

Cytoplasmic bridges

Early spermatids

Secondary

spermatocytes

Primary

spermatocyte

Interstitial cells

spermatogonium

Late spermiogenesis

meiosis

Initial spermiogenesis

Basal lamina

fibroblast

Figure 22–5. 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.

spermatogonium

Sertoli cell

Primary spermatocyte

Young spermatids

Late spermatids

Sertoli Cells

❖ Are columnar, extremely complex in shape, and

extend from the basal lamina to the lumen.

❖ Their apical and lateral plasma membranes are

markedly irregular in outline since they

envelope the developing germ cells.

Figure 22–4. Part of a seminiferous tubule with its surrounding tissues. The

seminiferous epithelium is formed by 2 cell populations: the cells of the

spermatogenic lineage and the supporting or Sertoli cells.

Cytoplasmic bridges

Early spermatids

Secondary

spermatocytes

Primary

spermatocyte

Interstitial cells

spermatogonium

Late spermiogenesis

meiosis

Initial spermiogenesis

Basal lamina

fibroblast

❖ Contain a well-developed smooth endoplasmic

reticulum, some rough endoplasmic reticulum,

an abundance of mitochondria and lysosomes,

and an extensive Golgi apparatus.

Spermatocytogenesis

❖ refers to division of the spermatogonia to provide a continuous supply of cells that will give rise to primary spermatocytes.

Meiosis

❖ are two successive divisions that reduce the chromosome number from diploid to haploid and produce spermatids.

Spermiogenesis

❖ is cytodifferentiation and transformation of spermatids to form spermatozoa.

❖ Nucleus is pale, oval, displaying frequent

indentations and a large nucleolus.

❖ Form occluding junctions with adjoining

Sertoli cells, thus subdividing the lumen of

the seminiferous tubule into a basal and an

adluminal compartment.

❖ Zonulae occludentes are responsible for

establishing the blood-testis barrier that

serves to protect the developing sperm cells

from autoimmune reactions.

Figure 22–12. The Sertoli cells

form the blood-testis barrier.

Neighbor Sertoli cells are attached

by occluding junctions that divide

the seminiferous tubules into 2

compartments and impede the

passage of substances between both

compartments. The basal

compartment comprises the

interstitial space and the spaces

occupied by the spermatogonia.

The 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. Cytoplasmic residual

bodies from spermatids undergo

phagocytosis by the Sertoli cells

and are digested by lysosomal

enzymes. The myoid cells surround

the seminiferous epithelium.

Adluminal

compartment (blue)

Late spermatids

Early spermatids

Sertoli cell

Spermatocyte

Spermatogonium

Basal compartment

(red)

Myoid cell

Endothelial

cells

Lumen of capillary

Functions

Of Sertoli cells are manifold.

❖ Support, protect, and nourish developing

spermatozoa.

❖ Phagocytose excess cytoplasm discarded by

spermatids in the process of spermiogenesis.

❖ Form the blood- testis barrier which plays an

essential role in isolating spermatogenic cells

from the immune system.

❖ Secrete a fluid into the seminiferous tubules

that transports spermatozoa to the genital

ducts.

❖ Contain FSH receptors and under FSH

influence synthesize androgen-binding protein

(ABP) that binds testosterone, concentrating it

to permit sperm maturation.

❖ Secrete inhibin, a hormone that inhibits

synthesis and release of FSH from the anterior

pituitary.

Sertoli cells(continued)

⚫ Produce Mullerian Inhibiting Factor/Hormone

that inhibits the paramesonephric duct/Mullerian

duct

⚫ Produces plasminogen activator which converts

plasminogen to active proteolytic hormone

plasmin

⚫ Transferrin, an iron-transporting protein

⚫ Ceruloplasmin, a copper-transporting protein

⚫ Stem cell factor

Figure 22–13. Hypophyseal

control of male

reproduction. Luteinizing

hormone (LH) acts on the

Leydig cells, and follicle-

stimulating hormone (FSH)

acts on the seminiferous

tubules. A testicular

hormone, inhibin, inhibits

FSH secretion in the

pituitary. ABP, androgen-

binding protein. (Modified

and reproduced, with

permission, from Bloom W,

Fawcett DW: A Textbook of

Histology, 10th ed.

Saunders, 1975.)

Spermatogenic Cells

❖ Include several characteristic cell types in the

seminiferous epithelium: spermatogonia,

primary spermatocytes, secondary

spermatocytes, spermatids, and spermatozoa.

❖ Each of these cells represents a distinct stage in

the differentiation of male germ cells. The

entire process is known as spermatogenesis.

Type A spermatogonia

(stem cells)

Type B spermatogonia

(progenitor cells)

Mitosis

Primary spermatocytes

secondary spermatocytes

Residual bodies

Spermatids

Residual bodies

Spermatozoa

Spermiogenesis

Second meiotic division

First meiotic division

Figure 22–7. 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. (Modified and reproduced, with

permission, from Bloom W, Fawcett

DW: A Textbook of Histology, 10th ed.

Saunders, 1975.)

Spermatogenesis

❖ Is divided into three phases:

spermatocytogenesis(spermatogonial phase) ,

meiosis( spermatocyte phase), and

spermiogenesis( spermatid phase).

❖ In man takes approximately 74 days; its cell

divisions are unusual, in that the daughter cells

remain connected to each other via

intercellular bridges (forming a syncytium).

Syncytium

❖ May be responsible for the synchronous

development of germ cells along any one

seminiferous tubule.

❖ Is disrupted at the completion of

spermatogenesis, when the individual

spermatozoa are released into the lumen ( The

process known as spermiation)

Spermatogonia

❖ are the diploid germ cells that sit upon the

basal lamina.

❖ are of three types: pale type A, dark type A,

and type B.

Pale spermatogoniaArterioles

Seminiferous

epithelium

Sertoli cell

Spermatogonia B

Dark spermatogonia

Nucleolus

Venule

Pale Type A

❖ are small (about 12 um diameter) and possess a pale-staining nucleus and cytoplasm containing spherical mitochondria, a small Golgi complex, and abundant free ribosomes.

❖ at puberty these cells undergo mitosis and give rise to either more pale type A spermatogonia (to maintain the supply of spermatogonia) or type B spermatogonia (which undergo mitosis and give rise to primary spermatocytes).

Dark Type A

❖ (with dark nuclei) represent noncycling,

reserve cells that have the potential to produce

more pale type A cells.

lumen

Seminiferousepithelium

Sertoli cell

Spermatogonia

Connective tissue

Primary

spermatocyte

Basal compartment

Spermatozoa

myoid cell

Fibroblast

Spermatid

Adluminalcompartment

Primary Spermatocytes

❖ are identified as the largest germ cells in the seminiferous epithelium.

❖ are diploid cells (46 chromosomes) that undergo meiosis.

Prophase

❖ of the first meiotic division is long (it takes more than 22 days).

❖ Including several stages: leptotene, zygotene, pachytene, diplotene (during which crossing over, the exchange of genetic material between homologous chromosomes, occurs) and diakinesis.

❖ is followed by metaphase I, anaphase I, and telophase I, which compose the first meiotic division.

First Meiotic Division

❖ results in the formation of small secondary spermatocytes.

Secondary Spermatocytes

❖ possess the haploid number of chromosomes (23), and

the amount of DNA has been reduced (from 4N to

2N).

❖ undergo the second division, producing spermatids.

Spermatids

❖ are haploid cells with 23 chromosomes and one-half the amount of DNA (since no S phase took place).

❖ are small (7 to 8 um diameter) and located near the lumen of the seminiferous tubule.

❖ their nuclei often display regions of condensed chromatin.

❖ contain a pair of centrioles, mitochondria, free ribosomes, smooth endoplasmic reticulum, and a well-developed Golgi apparatus.

❖ undergo the cytodifferentiation process known as spermiogenesis.

Spermiogenesis

❖ Is the unique differentiation process whereby spermatids transform into spermatozoa that are release into the lumen of the seminiferous tubule.

❖ Acrosome and sperm tail are formed during spermiogenesis, the nucleus becomes condensed and elongated, and excess cytoplasm not directly involved in forming the spermatozoa is shed and phagocytosed by Sertoli cells.

❖ Is divided into four phases: Golgi, cap, acrosome, and maturation phases.

Golgi Phase❖ of spermiogenesis is characterized by the formation of

proacrosomal granules in the Golgi complex.

Proacrosomal Granules

❖ coalesce to form a single acrosomal granule

enclosed within an acrosomal vesicle, which

becomes attached to the anterior end of the

nuclear envelope.Centrioles

❖ migrate away from the nucleus to form the

flagellar axoneme and then retreat toward the

nucleus and assist in forming the connecting

piece associated with the tail.

Cap Phase

❖ Involves the expansion of the acrosomal

vesicle over much of the nucleus, to form the

acrosomal cap.

Acrosomes

❖ contain hydrolytic enzymes (acid phosphatase,

neuraminidase, hyaluronidase, protease, and

phosphatase).

Acrosomal Reaction

❖ refers to the release of enzymes that facilitate the

dissociation of the cells of the corona radiata and the

digestion of the zona pellucida.

Acrosome Phase

❖ is characterized by the nucleus becoming

condensed and flattened, mitochondria

aggregating around the proximal portion of the

flagellum to form the middle piece, and

elongation of the spermatid.

Elongation

❖ may be facilitated by a cylinder of microtubules, the

manchette. By the end of the acrosome phase the

spermatids are oriented with their acrosomes pointing

toward the base of the seminiferous tubule.

⚫ Figure 22—10. 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.)

Maturation Phase

❖ is characterized by excess cytoplasm being

discarded (including the intercellular bridges

that connected the spermatids) and

phagocytosed by Sertoli cells.

❖ is completed when nonmotile spermatozoa are

released (tail first) into the lumen of the

seminiferous tubule.

Cycle of Seminiferous Epithelium

❖ refers to the wave-like sequence of maturation that

occurs along the seminiferous tubules.

One Cycle

❖ is the reappearance of identical cell associations within

the epithelium.

❖ in humans is approximately 16 days, so that 4.6cycles

(approximately 74 days) must occur for a

spermatogonium to be transformed into a

spermatozoon.

⚫ Figure 22—9. Top: The principal changes occurring in spermatids during spermiogenesis. 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 mobility and may protect the genome 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.

Histophysiology

Temperature

❖ of 35˚C is critical for the development of spermatozoa.❖ is achieved in the scrotum by the pampiniform plexus

of veins that wrap around the testicular artery and function to dissipate heat.

❖ is achieved also by evaporation of sweat from the skin of the scrotum.

❖ below 35˚C, contraction of the cremaster muscle in the spermatic cord brings the testis close to the body wall to increase the temperature.

Cryptorchidism

❖ is a condition when the testes fail to descend into the scrotum during development.

❖ the normal body temperature inhibits spermatogenesis, resulting in sterility. However, this condition does not affect testosterone production.

Luteinizing Hormone (LH)

❖ of the pituitary gland stimulates the interstitial cells of Leydig to secrete testosterone, which is responsible for the normal development of male germ cells and secondary sex characteristics.

Follicle-Stimulation Hormone (FSH)

❖ of the pituitary gland acts on the Sertoli cells, promoting the synthesis of androgen-binding protein (ABP).

ABP

❖ binds with testosterone and maintains a high

concentration of testosterone in the seminiferous

tubules, where it is essential for spermatogenesis.

❖ binds estrogens and inhibits spermatogenesis.

Increased testosterone levels inhibit LH release,

whereas FSH release is stopped by inhibin (secreted

by Sertoli cells).

Figure 22–13. Hypophyseal

control of male

reproduction. Luteinizing

hormone (LH) acts on the

Leydig cells, and follicle-

stimulating hormone (FSH)

acts on the seminiferous

tubules. A testicular

hormone, inhibin, inhibits

FSH secretion in the

pituitary. ABP, androgen-

binding protein. (Modified

and reproduced, with

permission, from Bloom W,

Fawcett DW: A Textbook of

Histology, 10th ed.

Saunders, 1975.)

Genital Ducts

❖ convey the spermatozoa and semen to outside of

the body.

❖ extend from the seminiferous tubules to the

urethra. Although they are continuous, they are

structurally and histologically different. Their

names identify the regional division and unique

characteristics they possess.