Unit 2 – Reproductive Module Histology of the male reproductive system Safaa El Bialy (MD, PhD)

Objectives Identify the following structures of the testes: seminiferous tubules, interstitial cells of Leydig, spermatogonia, primary spermatocytes, secondary spermatocytes, spermatozoa, Sertoli cells, epididymis (and its cell layers). Describe the histology of the prostate. Identify the erectile tissue in the penis.

Masculine genital apparatus Four main functional constituents: The testicles Production of gametes Secretion of testosterone 2. Duct system (efferent ducts, epididymis, vas deferens, ejaculatory duct) Receive, stock and vehicle the sperms 3. Exocrine glands (seminal vesicles and prostate) Secrete a nutritive, lubricating liquid 4. Penis Organ of copulation

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Testicular descent http://www.youtube.com/watch?v=a0PFGU6-FFE

Les couches du testicule Epidermis Dartos muscle External spermatic fascia (fascia of external oblique muscle) Cremasteric muscle (fibres of internal oblique muscle) Internal spermatic fiascia(fascia transversalis) Tunica vaginalis (parietal layer) Virtual cavity formed by the 2 layers of the vaginalis Tunica vaginalis (visceral layer) Tunica albuginea Interlobular septum of the testicle

Testis tunica vaginalis sheath derived from the peritoneum that is picked up by the testis along the course of its migration to the scrotum double mesothelial layer that covers almost the entire testis tunica albuginea capsule of connective tissue surrounding the testis fibrous septa extend from the albuginea and divide the testis into lobules lobuli testis each lobule contains1-4 seminiferous tubules, where spermatozoa are produced the seminiferous tubules converge towards a very anastomosed plexus, the rete testis; from there the efferent ducts carry spermatozoa to the epididymis testicular interstitium (tissue surrounding the tubules) is formed by loose connective tissue containing vessels and interstitial cells of Leydig that secrete testosterone

Seminiferous tubules Structure of seminiferous tubules: seminal epithelium rests on a basal lamina epithelium made up of Sertoli cells (supporting cells, not germinal cells) and germinal cells at various stages of spermatogenesis Basal membrane Fibromyoblast Fibrocyte Sertoli cell Spermatogonie A Germinal cells at different stages Spermatozoid lumen

Seminiferous tubules and interstitium Lumen Basal lamina Interstitial cells of Leydig Spermatogonium Sertoli cells Spermatocyte I Spermatids

Tubules séminifères SC sertoli cells PS primary spermatocytes F fibroblasts M myocytes RS round spermatids LS late spermatid

Cells of spermatogenesis Spermatogonia the only germinal cells present before puberty round, sparse cytoplasm and found near the basal lamina diploid for chromosome number (46, 2n) Primary spermatocytes largest germinal cells; abundant cytoplasm large nucleus with chromatin strands in a reticular pattern Secondary spermatocytes produced by meiosis I smaller and closer to the lumen haploid for chromosome number (23, n) divide quickly into spermatids, therefore rarely identified Spermatids produced by meiosis II small with a dark nucleus; closest to the lumen Spermatozoa product of spermiogenesis within the lumen have long flagellum

Seminiferous tubules Lumen Spermatids Sertoli cells Primary spermatocytes Spermatogonia Basal lamina 13

Sertoli cells Derived from mesoderm They can only proliferate in the first year of life (their equivalent in the female are follicular cells) They are long and pyramid shaped, and extend from the basal lamina to the lumen They have an oval, indented, pale nucleus, and a clearly visible nucleolus

Seminal epithelium Spermatozoa

Functions of Sertoli cells Physical and nutritional support Secretory functions in the male embryo, they secrete MIS (Müllerian inhibiting substance), which inhibits the development of Müllerian ducts secretion of ABP (Androgen Binding Protein), which concentrates testosterone in the tubular lumen for spermatogenesis and spermiogenesis secretion of inhibin, which suppresses the pituitary secretion of FSH secretion of tubular fluid necessary for transporting spermatozoa Phagocytosis Protection (blood-testis barrier)

Blood-testis barrier Tight junction complexes joining Sertoli cells they are found above the spermatogonia and form the blood-testis barrier Junctions that separate the seminiferous tubules into two compartments: basal compartment located between the basal lamina and tight junctions contains spermatogonia, which have access to blood-borne materials adluminal compartment contains the other cells formed during spermatogenesis; they are protected by the blood-testis barrier cells of this compartment are nourished by Sertoli cells Following mitotic division of spermatogonia, the tight junctions break down to accommodate the passage of primary spermatocytes in the adluminal compartment, after which new tight junction complexes are formed

Interstitial cells of Leydig Found between the seminiferous tubules Abundant acidophilic cytoplasm containing lipid vacuoles; resemble adrenal cortical cells under the electron microscope (cells that synthesize steroids, therefore containing abundant smooth endoplasmic reticulum) Secrete testosterone when stimulated by LH 18

Seminal fluid Sperm 3-5 ml per ejaculation close to 100 million spermatozoa approximately 20% are abnormally shaped and 25% are immobile secretions of accessory glands alkaline in order to neutralize the acid environment of the urethra and vagina contains prostaglandin (affects the transport of spermatozoa in the genital systems of both sexes) Sperm Flagellum Nucleus Acrosome Head

Epididymis Coiled shape has a head, body and tail Formed from the epididymal canal an extremely tortuous tube (about 4-6 m long!) Surrounded by vascular connective tissue and smooth muscle for peristaltic movements The epididymis is a reservoir for spermatozoa maturation phase

Epididymis Epithelium pseudostratified columnar Epididymal canal Vascular connective tissue Spermatozoa Connective tissue Epithelium Spermatozoa Smooth muscle Stereocilia Epithelium pseudostratified columnar cells have (stereocilia)

Spermatic cord and vas deferens The vas deferens is the extension of the epididymal canal It passes through the spermatic cord before entering the pelvis The spermatic cord also contains blood vessels, nerves and connective tissue Vas deferens Adventitia Muscle layer (thick) Mucosa Stellate lumen Blood vessel Connective tissue

Vas deferens Lumen Stereocilia Pseudostratified columnar epithelium Lamina propria Muscle layer

Canal deferent

Urethra is lubricated by: Cowper’s bulbourethral glands periurethral glands of Littre 25

Seminal vesicles Glands that produce an alkaline viscous yellowish secretion (~ 70% of seminal fluid) Mucosa is a system of anastomosed folds; formed by pseudostratified columnar epithelium and a lamina propria Muscle layer formed by smooth muscle; contracts during ejaculation (inner circular and outer longitudinal) Mucosal folds Smooth muscle Low magnification High magnification

Prostate Gland that produces a thin milky secretion (30% of seminal fluid); rich in citric acid and hydrolytic enzymes Formed by tubuloalveolar glands surrounded by fibromuscular stroma 3 prostate zones transition – surrounds the proximal segment de of the prostatic urethra central – surrounds the ejaculatory ducts peripheral Epithelium is simple columnar (mostly) or pseudostratified columnar

Prostate Glandular epithelium Gland Fibromuscular stroma Épithélium Low magnification High magnification

Prostate Lumen Epithelium Corpora amylacea (prostatic concretions) Fibromuscular tissue

Penis (cross section) 30

Erectile tissue in the penis 3 erectile tissues in the penis 2 corpora cavernosa and 1 corpus spongiosum surrounded by tunica albuginea (connective tissue) Erectile tissue is formed by wide vascular spaces bordered by endothelium, supported by trabeculae of connective tissue containing smooth muscle fibres Trabecula Vascular space Tunica albuginea Low magnification High magnification

  This table shows the male reproductive homologous structures to the women’s: Female structure Male structure Labia majora Scrotum Bulbs of the vestibule Corpora spongiosa Subcutaneous smooth muscle of the labia majora Dartos muscle of scrotum Labia minora Spongy urethra Bartholin’s gland Cowper’s gland Crura Crus of penis Clitoris Penis Clitoral hood Foreskin Clitoral glans Glans penis Skene’s glands Prostate gland Ovary Testis