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Histology of the male reproductive system
Testes
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Each testes surrounded by capsule of dense connective tissue known as the
tunica albuginea
Thickened on posterior side to form the mediastinum testis, from which fibrous
septa penetrate the organ dividing it into ~250 lobules
Each lobule contains 1-4 seminiferous tubules surrounded by loose connective
tissue rich in blood and lymphatic vessels, nerves and endocrine interstitial
cells (Leydig cells)
o Seminiferous tubules produce sperm
o Leydig cells secrete testicular androgens (testosterone and
dihydrotestosterone)
Testes develop retroperitoneally in dorsal wall of embryonic abdominal cavity
o Move during foetal development, eventually suspended in scrotum via
spermatic cord
o Due to origin in the abdomen, each has a serous sac (tunica
vaginalis), derived from the peritoneum
Temperature of ~34oC required for spermatogenesis, and maintained in the
scrotum by various mechanisms
o Testicular arteries are surrounded by the pampiniform venous plexus,
which forms a countercurrant heat exchange system
o Evaporation of sweat from the testes also contributes
o Relaxation and contraction of the dartos muscle of the scrotum and
cremaster muscle of the spermatic cord also regulates

Taken from Mescher, Junqueira’s Basic Histology: Text and Atlas, Twelfth Edition
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Clinical note
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Cryptorchidism is failure of descent of the testes into the scrotum
Testes maintained at core body temperature
Some cases spermatogenesis can occur normally if they are surgically
removed to the testes
So important to check newborns that the testes are present in the scrotum
Germ cell proliferation is inhibited at core body temperature, but
testosterone synthesis by interstitial cells is not, so secondary sex
characteristics are not affected
Spermatogonia affected by alcohol, malnutrition and certain drugs
Interstitial cell tumours can cause precocious puberty

Seminiferous tubules
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~200 million sperm produced per day
Each tubule is a convoluted loop linked by a straight tubule to the rete testis
The rete testes is a labyrinth of epithelium-lined channels in the mediastinum
testes
Efferent ductules connect the rete testes to the epididymis
Seminiferous tubules are lined with complex, specialised stratified epithelium
(seminiferous epithelium)
Basement membrane covered by fibrous connective tissue lined with myoid
cells, allowing weak contractions
Two types of cells in the seminiferous epithelium
o Sustentacular (Sertoli cells): non-dividing, supportive
o Proliferative cells of the spermatogenic lineage

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Proliferative cells have 4-8 layers and produce cells that become sperms
Spermatogenesis: germ cell division through mitosis and meiosis
Spermiogenesis: final differentiation of haploid germ cells

Spermatogenesis
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Begins at puberty with a primitive germ cell (spermatogonium)
Located basally
Stem cells divide to give new stem cells and transit amplifying progenitor cells
(type A spermatogenia)
Type A spermatogenia undergo clonal divisions remaining interconnected as
syncytium, before forming type B spermatogenia
Type B spermatogenia then undergo a final mitotic division to make two cells
that grow to become primary spermatocytes
Primary spermatocytes replicate their DNA (2n), and enter meiosis
o Homologous chromosomes come together in synapsis
o DNA recombination
o Cell division to produce diploid cells (46 chromosomes) but each has
chromatids, so 4n
Cells then enter meiotic prophase and stay so for 22 days
Homologous chromosomes separate in the first meiotic division, producing
smaller cells called secondary spermatocytes
o Only 23 chromosomes, so haploid, but each has 2 chromatids, so 2n
Secondary spermatocytes are short lived – quickly undergo second meiotic
division
o Division separates the chromatids, producing haploid cells called
spermatids

Clonal nature of male germ cells
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Stem cells produced from type A spermatogonia remain as separate cells
All subsequent divisions of the daughter progenitors have incomplete
cytogenesis, and remain attached by intercellular cytoplasmic bridges
o Allows free communication between cells derived from a single type A
spermatogonium through their remaining meiotic and mitotic divisions
Some cells degenerate along the way, and some may separate
Spermatogenic syncytium role is unknown; may allow diploid cells to be
supplied with full complement of the RNA and proteins encoded on X or Y
that’s missing
Germ cells finally become separated during the differentiation process
Whole process takes @2 months
Cells at different stages of development are grouped together in the
seminiferous epithelium

Taken from Mescher, Junqueira’s Basic Histology: Text and Atlas, Twelfth Edition
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Taken from Mescher, Junqueira’s Basic Histology: Text and Atlas, Twelfth Edition
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Seminal vesicles
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Contain highly torturous tubes
Unusual mucosa
o Thin, complex folds that fill most of the lumen
o Folds lined with simple/pseudostratified columnar epithelium
o Cells rich in secretory granules
o Elastic lamina propria with smooth muscle layers (inner circular and
outer longitudinal)
Exocrine glands producing solution containing fructose, prostaglandins,
fibrinogen, plus other substances, proteins and enzymes (70% of ejaculate)
o Energy source, coagulation post-ejaculation, affect activity in female
reproductive tract
Structure and function dependent on testosterone

Prostate gland
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Surrounds urethra below the bladder
Contains branched tubuloalveolar glands surrounded by fibromuscular
stroma and covered by a capsule
Glands arranged in layers around the urethra of the bladder
o Inner mucosal
o Intermediate submucosal
o Peripheral main
Ducts from each gland may converge or empty into the prostatic urethra,
which runs through the centre of the prostate
Three zones

Transition zone(5% vol): surrounds prostatic urethra and glands
emptying in
o Central zone (25% vol): contains submucosal glands with longer ducts
o Peripheral zone (70% vol): contains main glands with longest ducts;
area most commonly affected by inflammation and cancer
Tubuloalveolar glands are lined by simple or pseudostratified columnar
epithelium
o Produce prostatic fluid, contains glycoproteins and enzymes
Glands surrounded by fibroelastic capsule; septa from the capsule divide the
gland into lobes
Structure and function dependent on testosterone
Corpora amylacea (small, often calcified concentrations) commonly seen
o Deposited GAGs; no obvious clinical relevance
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Taken from Mescher, Junqueira’s Basic Histology: Text and Atlas, Twelfth Edition
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Clinical note
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During an erection, PNS stimulation in the vasculature release NO to
endothelial cells
Endothelial cells synthesise and release more NO
NO stimulates cGMP in smooth muscle cells, triggering sequestration
of Ca2+ in SER – muscle relaxation
Diffusion through smooth muscle via gap junction – relaxation and
vasodilation, inflow of blood
Arterial or neural insufficiency to tissue of the penis can lead to
erectile dysfunction
o Can be treated with phosphodiesterase inhibitor e
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sildenafil, preventing cGMP degradation
o Enhances effect of NO

Reference
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Junqueira’s Basic Histology: Text and Atlas
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