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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.