Male Reproductive System PDF

MALE REPRODUCTIVE SYSTEM Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected]  LEARNING OUTCOMES HIST.24 - Reproductive Male HIST.24.01 - Name the layers of the capsule of the testis HIST.24.02 - Describe the division of th...

MALE REPRODUCTIVE SYSTEM Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected]  LEARNING OUTCOMES HIST.24 - Reproductive Male HIST.24.01 - Name the layers of the capsule of the testis HIST.24.02 - Describe the division of the testis into lobules HIST.24.03 - Describe the arrangement of the seminiferous tubules within the lobules HIST.24.04 - Define spermatogenesis and describe each cell type involved, in order HIST.24.05 - Describe the structure and give the function of the Sertoli cell HIST.24.06 - Define spermiogenesis and list the steps involved HIST.24.07 - Describe the structure of a mature sperm HIST.24.08 - Give the function and location of Leydig cells HIST.24.09 - List the ducts through which sperm pass and give one distinguishing feature of each HIST.24.10 - State the function of the seminal vesicle and prostate gland HIST.24.11 - Describe the organization of the penis as seen in cross section HIST.24.12 - Describe the histological structure of erectile tissue HIST.24.13 - Describe the blood supply of the penis and the role that it plays in 2 erectile function  OVERVIEW Male reproductive system (MRS) is composed of: gonad - testes, genital excurrent ducts: epididymis, 3 ductus deferens, ejaculatory duct accessory glands: prostate gland, seminal vesicles, bulbourethral glands, male urethra copulatory organ (penis).  FUNCTIONS OF MRS Reproductive (production of the male gametes - spermatozoa), Endocrine (production of the androgen (male sex hormone) - testosterone). Helps in deposition of sperms in the female reproductive tract. 4  TESTIS Testes are a pair of male gonads located in the scrotum. Testis develops in the posterior abdominal wall and descends into the scrotum. 5 Temperature of the scrotum is 2–3°C lower than the body temperature, which is essential for normal spermatogenesis. Functions: 1. Production of the male gametes 2. Synthesis and secretion of the male sex hormone testosterone.  TESTIS Testis is surrounded by: tunica vaginalis (visceral and parietal layers) - serous sac derived from the peritoneum tunica albuginea - collagenous connective tissue (CT) capsule of the testis. tunica vasculosa - vascular capsule of the testes. mediastinum testis represents the posterior thickened portion of the tunica 6 albuginea housing the rete testis.  TESTIS CT septa arising from the capsule penetrate the gland and divide it into 250 7 pyramidal lobules. Each lobule is occupied by 1-4 convoluted seminiferous tubules, which form a network. These are sperm producing tubules. Each seminiferous tubule is surrounded by CT stroma.  CONVOLUTED SEMINIFEROUS TUBULES Consist of: fibrous tunica propria, complex stratified seminiferous, germinal, or spermatogenic, epithelium. Tunica propria consists of: 1. Basal layer: innermost layer; contains thin collagen fibers; 2. Myoid layer: spindle-shaped myofibroblastes (myoid cells) which exhibit smooth muscle 8 characteristic → aids movement of spermatozoa along the tubules. 3. External fibrous layer: collagen fiber and fibroblasts.  CONVOLUTED SEMINIFEROUS TUBULES Seminiferous (spermetogenic) epithelium consists of 2 basic cell populations: 1) Spermatogenic cells – sperms in different stages of their development 2) Sertoli (supporting) cells. 9 Photomicrograph. Histology of testis (low magnification, H&E stain). 10  SPERMATOGENIC CELLS Spermatogenic cells are arranged in layers (5 or 6) and differentiate from the periphery to the lumen of the tubule: spermatogonia (types A (A pale and A dark) and type B) are the undifferentiated germ cells, are located at the periphery of the tubule; primary spermatocytes (46 chromosomes, 4N DNA) are found in the middle of 11 the tubule; they results from the growth and differentiation of one type B spermatogonium; secondary spermatocytes (23 chromosomes, 2N DNA) arise from the division of primary spermatocytes; they are located near the lumen of the seminiferous tubule; spermatids (23 chromosomes, IN DNA) are small cells with condensed chromatin; spermatozoa. SPERMATOGENIC CELLS 12  SERTOLI (SUPPORTING, SUSTENTACULAR, NURSE) CELLS Sertoli cells are tall pyramidal cells. Rest on the basal lamina, apical ends extend into the lumen of the seminiferous tubule. Each Sertoli cell supports 30–50 germ cells; 13 Has abundant sER, some rER, well-developed Golgi complexes, numerous mitochondria. Elongated nucleus has infoldings and a prominent nucleolus, very little heterochromatin. Varying numbers of lysosomes, lipid droplets, vesicles, and glycogen granules.  FUNCTIONS OF SERTOLI CELLS 1) support, protection, and nutrition of the developing spermatozoa; 2) phagocytosis of cytoplasmic fragments, which form during spermatogenesis; 3) secretion of: fluid that is used for sperm transport; androgen binding protein (ABP) that serves to concentrates testosterone in the luminal 14 compartment of the tubule, where high concentrations of testosterone are essential for normal maturation of the sperm. small amount of steroids - estrogens and testosterone; peptides inhibin and activin, which suppress and activate FSH synthesis and release in the anterior pituitary gland; antimullerian hormone causes regression of the embryonic müllerian (paramesonephric) ducts; without MIS these ducts persist and become parts of the female reproductive tract); plasminogen activator, which converts plasminogen to the active proteolytic hormone plasmin, transferrin (assist in providing iron to maturing gametes), and ceruloplasmin (a copper-transporting protein). ANDROGEN BINDING PROTEIN 15  JUNCTIONS Sertoli cells are bound to one another by an unusual junctional complex; Lateral processes of Sertoli cells + flattened cisterna of sER+ Actin filament bundles = Sertoli cell-to-Sertoli cell junctional complex, that divides the seminiferous epithelium into 2 compartments: o basal (abluminal), o adluminal. 16 Basal compartment contains spermatogonia and has free access to materials found in the blood. Adluminal compartment contains spermatocytes, spermatids and spermatozoa.  BLOOD-TESTIS BARRIER A barrier between the blood vessels and the seminiferous tubules. Consists of: o endothelial cells of blood capillary of interstitial CT; o basal lamina of endothelial cells; o interstitial connective tissue; 17 o tunica propria of seminiferous tubule; o Sertoli cell-to-Sertoli cell junctional complex. FUNCTIONS: prevents passage of cytotoxic agents into the seminiferous tubules. protects also the developing sperm cells from immunologic attack. BLOOD-TESTIS BARRIER 18  ENDOCRINE FUNCTION OF THE TESTIS Spaces between the seminiferous tubules are filled with interstitial connective tissue, nerves, blood and 19 lymphatic vessels. Principal cells of interstitial tissue are the interstitial, or Leydig, cells, which have the characteristic of steroid-secreting ceils. Franz von Leydig, 1821–1908, German anatomist ARROWS SHOW LEYDIG CELLS 20  LEYDIG CELLS Rounded in shape, have a centrally located nuclei, elaborate smooth sER→ eosinophilic cytoplasm. INCLUSIONS: lipid droplets, lipofuscin pigment, rod-shaped cytoplasmic crystals (crystals of Reinke). Leydig cells have luteinizing hormone (LH) receptors. 21 LH stimulates Leydig cell for production of testosterone. Crystals of Reinke Crystals of Reinke * Friedrich Reinke 1862– 1919, German anatomist  PRODUCTION OF TESTOSTERONE Production of testosterone starts in the 7th week of intrauterine development. It gradually decreases from the 5th month of the intrauterine development and the activity is decreased until puberty, After puberty interstitial endocrine (Leydig) cells are stimulated by the increased level 22 of the LH from the adenohypophysis to produce more testosterone. In this period, testosterone is mainly necessary for the initiation of spermatogenesis.  FUNCTIONS OF THE LEYDIG CELLS Synthesis of testosterone, which is responsible for the development of male reproductive organs and promoting secondary sexual characteristics. Also secrete: insulin-like protein 3 that stimulates descent of the testis during development. testicular oxytocin stimulates contraction of myoid cells, moving the spermatozoa toward the efferent ductules.  HORMONAL REGULATION Testosterone secretion is promoted by luteinizing hormone (LH) FSH stimulates Sertoli cells to manufacture and discharge androgen-binding protein (ABP), which binds to testosterone. Increased level of testosterone in the region of spermatogenesis stimulates the process of spermatozoon production. 24 Testosterone and inhibin, secreted by Sertoli cells, stimulate a feedback mechanism to inhibit LH production.  SPERMATOGENESIS Spermatogenesis is the process by which spermatogonia develop into sperm. Complete cycle (gonia → zoa) takes 60 to 74 days. It begins shortly before puberty, under the influence of rising levels of pituitary gonadotropins, and continues throughout life. 25 Mature male functional sperm cells are produced within the seminiferous tubules of the testes. *Please, revise the 1st Embryology Lecture from XY1040.  MALE GENITAL DUCTS Male genital ducts are subdivided into: I. Intratesticular, II. Excurrent ducts. 26 I. Intratesticular excretory ducts: 1. Tubuli recti (straight tubules), 2. Rete testis, 3. Efferent ductules.  INTRATESTICULAR DUCTS Tubuli recti are lined with Sertoli cells in an initial part, in the distal part - simple cuboidal epithelium. Rete testis is a highly anastomotic network of channels lined with simple cuboidal epithelium. 27 From the rete testis 10-20 efferent ductules extend that form the head of the epididymis. Rete testis  EFFERENT DUCTULES #3 in the picture LAYERS: I. Mucosa which contains: 1) pseudostratified columnar epithelium composed of: 28 - columnar ciliated cells that promote the transport of spermatozoa toward the ductus epididymis; - nonciliated cuboidal cells that absorb much of the fluid secreted by the seminiferous tubules; 2) lamina propria is composed of LCT; II. Muscularis is composed of circularly oriented smooth muscle cells; III. Adventitia consists of LCT.  EXCURRENT DUCTS Excurrent ducts are the duct of the epididymis, which forms the epididymis, the ductus (vas) deferens and the ejaculatory duct. 29  EPIDIDYMIS Epididymis is a single, long and extremely convoluted duct located at the posterior aspect of each testis. It consists of a head, which receives efferent ductules, a body and a tail, which is at the lower pole of the testis and continues as vas deferens. 30  EPIDIDYMIS I. Mucosa: 1) pseudostratified columnar epithelium that composed of: - tall columnar (principal) cells with long 31 microvilli (stereocilia); - basal cells - stem cells; 2) lamina propria is composed of LCT; II. Muscularis is composed of smooth muscle cells whose peristaltic contractions help to move the sperm along the duct; III. Adventitia consists of LCT. EPIDIDYMIS 1. Tunica albuginea of testis 2. Rete testis in mediastinum testis 3. Epididymis (tail) 4. Vas (ductus) deferens 32 5. Pseudostratified epithelium of epididymis 6. Spermatozoa in lumen of duct of epididymis  DUCTUS (VAS) DEFERENS Continuation of the ductus epididymis; it empties into the prostatic urethra. Ductus deferens has a thick wall but a small lumen. Wall consists of 3 layers: 33 I. Mucosa forms longitudinal folds and comprises: 1) pseudostratified columnar epithelium: columnar cells with stereocilia; basal cells - stem cells; 2) lamina propria is composed of LCT rich in elastic fibers; II. Muscularis: longitudinal inner and outer layers separated by a circular layer; III. Adventitia consists of LCT. DUCTUS (VAS) DEFERENS 34  EJACULATORY DUCT About 2 cm long paired duct, which arises from the excretory duct of seminal gland epmptying into the ductus deferens just before entering the prostate. It passes through the prostate until it opens into the prostatic urethra in the area of a small protuberance called the seminal colliculus (colliculus seminalis). 35  ACCESSORY GENITAL GLANDS Prostate gland, Seminal vesicles, Bulbourethral glands (Cowper’s gland). 36  PROSTATE GLAND Largest accessory sex gland which surrounds the bladder neck and the first part of the urethra. Prostate gland is covered by CT capsule rich in smooth muscle cells. Prostate consists of 30–50 branched tubuloalveolar glands (parenchyma), surrounded by a fibro-muscular stroma. 37  PROSTATE GLAND Prostate consists of: I. Capsule II. Parenchyma (tubuloalveolar glands) – functional part, III. Fibromuscular stroma – supportive scaffold. 38 PROSTATE GLAND 39  PROSTATE GLAND. PARECNYMA I. Parenchyma – prostatic glands consist of: a) Secretory portions, b) Duct system. a) Secretory portions of prostatic gland are lined by a simple or pseudostratified 40 columnar epithelium which consists of 4 types of cells: 1. Prostatic exocrine cell (prostatocyte) – columnar cell with secretory vacuoles and lysosomes – secrete lipoprotein secretory granules called prostasomes into the ejaculate, which, after ejaculation, fuse with the sperm cell membrane, change its structure and function, and provide sperm with enough zinc and calcium – prostasomes contain many enzymatically active substances, signal molecules and ions that play a role in the modulation of sperm function 2. Basal cell – cuboidal cell; the source of the renewal of glandular epithelium 3. Prostatic endocrine cell – contains neuron-specific enolase, serotonin and chromogranin in the secretory granules 4. Sialomucin-producing cell.  PROSTATE GLAND. PARENCHYMA 2. Ducts Submucosal and main glands open into the urethra through ducts. There are 12–20 independent ducts opening into the urethra. Ducts are lined by a simple columnar epithelium which changes to a transitional epithelium in the terminal part.  DIVISION TO HISTOLOGIC ZONES ACCORDING TO MCNEAL This division is commonly used in clinical practice 30 to 50 compound tubulo-alveolar prostatic glands are divided on 3 groups: o Transition zone (5% of the prostate volume), surrounds the prostatic urethra, and contains the mucosal glands emptying directly into the urethra. o Central zone (25%) contains the submucosal glands with longer ducts. o Peripheral zone – main (70%) contains the main glands with still longer ducts.  CLINICAL CORRELATION Benign prostate hyperplasia is characterised by an increase in number of the submucosal prostate glands → enlargement of transitional zone → obstruction of urinary flow. Carcinoma of the prostate is a malignant neoplasia arising in the glandular epithelium of the peripheral zone or, less commonly, in the central or transitional zones. Peripheral zone is palpable on per-rectal examination. Prostate-specific antigen (PSA)/kallikrein-3 is a glycoprotein enzyme secreted by prostatic epithelium. In prostatic cancers, PSA level increases significantly. 43  PROSTATE GLAND. FIBROMUSCULAR STROMA II. Stroma includes a thin capsule that surrounds the entire organ and extensions from the capsule which penetrate the parenchyma. It consists of fibrous (collagen and elastic fibers) CT and smooth muscles (fibromuscular). Smooth muscles present in the stroma contract during ejaculation and propel the secretions of the gland (the prostatic fluid) into the urethra.  PROSTATE GLAND Small spherical bodies of glycoproteins composition (prostatic concretions - (corpora amylacea) are frequently observed in the lumen of prostatic glands. These bodies are: often calcified, significance is not understood, 45 number increases with age.  FUNCTIONS OF THE PROSTATE GLAND Main function: secrete a clear, slightly alkaline (pH 7.29) fluid that contributes to the formation of seminal fluid. Prostate secretion is rich in: 46 prostatic acid phosphatase (PAP), fibrinolysin, citric acid, prostate-specific antigen (PSA), zinc, beta-microseminoprotein.  SEMINAL VESICLES A pair of elongated sac-like glands located at the base of the urinary bladder 47 FUNCTIONS: Produce seminal fluid. Seminal fluid is rich in fructose (main energy source for sperms) and prostaglandins. Seminal fluid is alkaline in nature that helps to neutralize vaginal secretions. Seminal fluid contains lipochrome pigments that impart yellowish color to semen.  SEMINAL VESICLES LAYERS: I. Mucosa which has many branched folds and comprises: 1) pseudostratified columnar epithelium; 2) lamina propria which is composed of LCT with elastic fibers; II. Muscularis which consists of outer longitudinal and inner circular layer of 48 smooth muscle tissue. III. Adventitia merges with the surrounding CT. SEMINAL VESICLES 49 SEMINAL VESICLES 50  BULBOURETHRAL GLANDS (COWPER’S GLANDS ) Located proximal to the membranous portion of the urethra and empty into it. 51 William Cowper, British Anatomist, 1666–1709.  BULBOURETHRAL GLANDS (COWPER’S GLANDS ) Compound tubulo-alveolar glands lined with mucus-secreting simple cuboidal epithelium. Skeletal and smooth muscle cells are present in the septa that divide each gland into lobes. 52 Secretion is clear mucus, contains galactose, galactosamine, galacturonic acid, sialic acid and acts as a lubricant, cleans and lubricates the urethra prior to and during ejaculation.  SEMEN Contains fluids and sperm cells from the testis and secretory products from the epididymis, ductus deferens, prostate, seminal vesicles, and bulbourethral glands. The major components of the semen can be traced to the secretion from the seminal 53 vesicles (65% to 75%) and prostate gland (25% to 30%). Additional components include testicular fluid (2% to 5%) that was not completely absorbed in the straight tubules as well as secretions from the bulbourethral (Cowper’s) glands that account for less than 1%. Semen is alkaline (pH 7.7) and helps to neutralize the acid environment of the urethra and the vagina. A normal single ejaculate contains approximately 70 to 100 million spermatozoa per millilitre. A man with a sperm count of less than 20 million spermatozoa/mL of ejaculate is considered to be sterile.  FACTORS WITH NEGATIVE INFLUENCE ON THE DEVELOPMENT OF SPERM CELLS 1. Chromosome aberrations, microdeletion of Y chromosome 2. Varicose veins, developmental testicular defects (untreated cryptorchidism – non- descended testes; 3. testicular agenesis – absence of testes) 4. Lack of nutrients (selenium, vitamins A, C, E, B12) 5. Systemic diseases, infections (parotitis), cystic fibrosis 6. Increased temperature (frequent visits to the sauna, tight underwear) 7. Endocrinopathy (central hypogonadism), steroid hormone treatment 8. Autoimmune sperm cell damage 9. Toxins (pesticides, polychlorinated biphenyls) 10.Some drugs (spironolactone), chemotherapeutics, ionizing radiation 11.Unhealthy lifestyle 12.Post-testicular causes of male infertility: impotence, retrograde ejaculation, post-infectious54 occlusion of ductus deferens, hypospadia, epispadias.  PENIS Penis is the male copulatory organ. Erectile tissue of the penis contains a specialized arrangement of arteries, shunts, and venous sinusoids within a matrix of CT and smooth muscle. Erectile tissue is organised into paired dorsal corpora cavernosa and one ventral corpus spongiosum. Wall: Skin Superficial fascia Deep fascia Tunica albuginea  PENIS Tunica albuginea - thick CT sheath that binds three erective masses together and also partially separates two corpora cavernosa. Between this sheath and the overlying skin are loose elastic CT (Buck’s fascia) and Colles fascia that permits the skin of the penis to move freely along the shaft. Penile urethra passes through the corpus spongiosum, where it is associated with small 56 mucous glands of Littre.  URETHRA MASCULINA – MALE URETHRA Parts: 1. Pars intramuralis – runs through the neck of the urinary bladder - transitional epithelium 2. Pars prostatica – runs through prostate - transitional epithelium 3. Pars intermedia (pars membranacea, diaphragmatica) – runs through the muscle tissue of the pelvic and urogenital floor - pseudostratifed or stratifed columnar epithelium, 4. Pars spongiosa – runs in the corpus spongiosum of urethra - stratifed squamous epithelium. References Thank you for your attention! 59 Manneken Pis, Location within Brussels.