Male Reproductive System PDF Notes

Male Reproductive System Dr. Lalit P. Singh Page 1 of 30 MALE REPRODUCTIVE SYSTEM Lecture Learning Objectives: 1. Describe the microanatomy and functions of the testis. Classi...

Male Reproductive System Dr. Lalit P. Singh Page 1 of 30 MALE REPRODUCTIVE SYSTEM Lecture Learning Objectives: 1. Describe the microanatomy and functions of the testis. Classify the testis as an exocrine gland by morphology and secretion. Describe the histological and anatomical organization of the testis in terms of its coverings, lobular organization, and interstitium. Describe the endocrine component of the testis. Describe the histological organization of the seminiferous tubule. 2. Describe the histological appearance of the Sertoli cell in the seminiferous epithelium. Describe the basal and adluminal compartments created by the Sertoli cell. Describe the functions of the Serotli cell. 3. Describe the spermatogenic cells in the testes. Describe the spermatogonial, spermatocyte and spermatid phases of spermatogenesis. Describe the location, function, and histology of the spermatogonial cell. Describe the location and histology of the primary spermatocyte. Describe the first meiotic division (reductional division) of the spermatocyte phase. Describe the second meiotic division (equatorial division) of the spermatocyte phase and its role in establishing haploid gametes. Describe the DNA and chromosome content of the spermatids. Describe the location and histology of the round and elongated spermatid. Describe the golgi phase, cap phase, acrosome phase and maturational phase. 4. Describe the microanatomy and functions of the excretory ducts of the male reproductive system. Describe the location, histological features, and function of the straight tubules. Describe the location, histological features, and function of the rete testis. Describe the location, histological features, and function of the efferent ductules. Describe the location, and histological features of the epididymal duct. Describe the functions of the principal cells of the epididymal duct. Describe the histological features of the ductus (vas) deferens. Compare and contrast the histology of the ampulla of the ductus deferens with that of the seminal vesicle. 5. Describe the microanatomy and functions of the accessory glands of the male reproductive system. Describe the histological organization of the seminal vesicle, the typical classification of the secretory epithelium and the major secretory molecule. Male Reeproductive System Dr. Lalitt P. Singh Page 2 of 30 Describe th he organization of the prostatee gland, the typpical classificattion of the secrretory epitheliuum, its secretions and a their functiion. Describe th he role of testossterone in accessory gland funnction. Describe th he two distinguiishing histolog gical features oof the prostate ggland. 6. Describe D the microanatomy an nd function of the t penis. Describe th nization of the penis in transvverse section. he general organ Describe th he histological organization o off the corpora ccavernosum, coorpus spongiosuum, and the peenile urethra. Describe th he connective tiissue and vascu ular componennts of the erectiile (cavernous)) tissues. Lecture Content Ou utline I. Testes II. Seertoli cells in the t testes III. Sp permatogenic cells in the teestes A. A Spermatogonia and the t spermatog gonial phase B. B Spermatocytes and the t spermatocyyte phase C. C Spermatids and the spermatid s phaase IV. Excretory ductss A. A Straighht tubules B. B Rete teestis C. C Efferen nt ductules D. D Epidid dymal duct E. Ductuss deferens V. Accessory A glannds A. A Seminaal vesicles B. B Prostatte gland C. C Bulbou urethral gland VI. Peenis General Comments: The malee reproductiv ve system (F Fig. 1) includes:: the testes, excretory e du uct system, accessory a glaands (seminaal vesicles, prostate glaand, bulboureethral glands) and a penis. Th his system iss responsib ble for sperm matogenesis and the productio on of male seex hormoness Fiig. 1. Male reeproductive (androgens - testosterrone). system m Male Reeproductive System Dr. Lalitt P. Singh Page 3 of 30 I. THE T TESTE ES (Fig. 2) The testess can be regarded as a an endocrrine gland, beccause Leydig g cells synth hesize and secrete testosterone. The testess can also bee regarded as a an exocrin ne organ, witth the secrettion product being the Fig. 2. DDiagram showiing the spermatozzoa. testees and A system of ducts fun nctions as a conduit c (chaannel) of speerm from secretoory ducts the semin niferous tubu ules out of th he body. Several gllands secretee products in nto this pathw way that com mbine with spermatozzoa to make up semen. A. A The teestis is a com mpound tubu ular gland thaat uses the hholocrine mechaanism to seccrete sperm (exocrine ( funnction of testes). B. B Each testis t ounded by a dense irreguular is surro conneective tissue capsule called the tunicaa albuginea (Fig. 3). 3 The innerrmost layer of o this capsuule is loose conneective tissue with blood vessels v calleed the tunicaa vasculosa. C. C The tu nea thickenss posteriorly to form unica albugin the meediastinum testis. t Septaee of connectiive tissue dividee each testis into lobules. D. D Each lobule l contaains from onee to four sem miniferous Fig. 3. A section of thhe testes tubulees (Figs. 3, 4). 4 Each sem miniferous tubbule begins aand ends neaar the meediastinum testes. t Male Reproductive System Dr. Lalit P. Singh Page 4 of 30 E. The interstitial connective tissue (interstitium or stroma) contains lymphatic vessels, blood vessels, and nerves. In addition there are Leydig cells (interstitial cells) as shown in Fig. 4. 1. Leydig cells are larger than any other cells of the interstitium, have an eosinophilic cytoplasm, and have a vesiculated nucleus with a prominent nucleolus and a cytoplasm with lipid droplets. They may be found in groups between the seminiferous Fig. 4. A section of the testes showing seminiferous tubules and interstitial tubules. connective tissue 2. Leydig cells function to secrete testosterone (endocrine function of the testes). 3. Testosterone is critical for development, maturation and maintenance of male gamete production, reproductive tract function, and male secondary sexual characteristics. 4. Like other steroid secretory cells, Leydig cells have abundant sER and many mitochondria with tubulo- vesicular cristae which give them their acidophilia by LM. F. Each seminiferous tubule is surrounded by a layer of dense connective tissue called the tunica propria. It contains contractile myoid cells that function like myofibroblasts. Myoid cells have characteristics of both smooth muscle cells and fibroblasts. In Male Reeproductive System Dr. Lalitt P. Singh Page 5 of 30 ns this layer is relatively human y thick. It conntracts to heelp propel secretted spermato ozoa along th he seminiferoous tubule luumen. G. G A basal lamina separates the tunica t propriia from the sseminiferouss epitheelium. H. H The seeminiferous epithelium is i a complexx stratified eppithelium thhat contaiins an epitheelial cell (Serrtoli cell) annd spermatoggenic cells called d spermatogo onia, spermaatocytes, andd spermatids (Fig. 5). Fig. 5. Seminiferous S eepithelium Clinical C corrrelation Male M infertility - The testis is suspend ded in a sac, the scrotumm, which maintains the tem mperature of the t testis 2-33 ºC below bbody tempeerature. This temperaturee reduction iis critical forr sperm produuction. Infertility can be caused c by seeveral factorrs including elevatted temperatture. Spermaatogenesis reequires a low wer tempeerature (34-3 35 ºC) than body b temperaature (37ºC)). If the testiss is kep pt at body tem mperature, sp permatogeneesis ceases, aalthough testostterone secretion is unafffected. Male s with undesscended testiclles (cryptorcchidism) are infertile. Othher factors pproducing sterilitty include mutagens, m steeroids, infecttions, and raadiation. Male Reproductive System Dr. Lalit P. Singh Page 6 of 30 II. SERTOLI CELLS IN THE TESTES A. The seminiferous epithelium contains epithelial cells (somatic cells that do not become sperm) called Sertoli cells (Fig. 6). Sertoli cells form compartments to organize the spermatogenic cells that are undergoing spermatogenesis. Fig. 6. Seminiferous epithelium containing Sertoli cells 1. Sertoli cells are columnar in shape and stretch from the basal lamina to the lumen of the seminiferous tubule. They have indistinct plasma membrane boundaries, an indented, vesiculated nucleus, and a prominent Fig. 7. Sertoli cell nucleus with prominent nucleoli nucleolus (Fig. 7). 2. The spaces between the Sertoli cells create microenvironments needed for the development of the different types of spermatogenic cells. 3. Sertoli-Sertoli cell junctions are specialized junctions created between two neighboring Sertoli cells within the seminiferous epithelium (Fig. 5). a. These junctions are the basis of the Fig. 8. TEM of Sertoli- Sertoli cell junction blood-testis barrier (Fig. 8, S1). Male Reproductive System Dr. Lalit P. Singh Page 7 of 30 b. They also divide the seminiferous epithelium into a basal compartment containing spermatogonium (and very briefly, primary spermatocytes), and an adluminal compartment containing spermatocytes and spermatids (Fig. 9). Fig. 9. Diagram showing adluminal and basal compartments 4. Sertoli cells also bind to spermatids within the seminiferous epithelium to form Sertoli-spermatid junctions (Fig. 8, S2). They are thought to help anchor the spermatid to the Sertoli cell during sperm development. 5. Sertoli cells produce testosterone binding protein to maintain a high concentration of testosterone (200 times higher than normal blood levels of 300- 1000 ng/dl) within the seminiferous epithelium since testosterone is necessary for spermatogenesis. 6. Sertoli cells secrete fluid to help move the spermatozoa along the lumen of the seminiferous tubule. Clinical correlation Autoimmunity to spermatozoa - If the Sertoli-Sertoli cell junctions are compromised, the immune system may detect "foreign" proteins of the spermatozoa, which have a different genetic makeup than the host, and mount an antibody response to them. Vasectomy allows spermatozoa to leak out of the reproductive tract and be exposed to the immune system. Such individuals frequently have autoimmunity to their sperm. Male Reproductive System Dr. Lalit P. Singh Page 8 of 30 III. SPERMATOGENIC CELLS IN THE TESTES Spermatogenesis takes approximately 65-75 days to complete in humans and is divided into three phases: 1. Spermatogonial phase: production of spermatocytes by spermatogonial (gonial) cells. 2. Spermatocyte phase: meiotic divisions of spermatocytes reduce the DNA content to one copy per cell. 3. Spermatid phase: differentiation of the sperm. A. Spermatogonia and the Spermatogonial phase Spermatogonia (gonia or gonial cells) are the least developed of the spermatogenic cells that reside within the seminiferous epithelium of the testes. There are actually 3 types of spermatogonia: Ad (dark), Ap (pale) and B (Fig. 10). Fig. 10. Diagram showing different cell types of spermatogonia Male Reproductive System Dr. Lalit P. Singh Page 9 of 30 1. All spermatogonia are round with a round nucleus, and are next to the basal lamina (basal compartment). Any cell resting on the basal lamina but lacking Sertoli cell morphology will be called a spermatogonial cell. The Ad, Ap, and B subtypes can be classified based on the appearance of the nuclei in routine histological preparations, but you are not responsible for this (Fig. 7). 2. Functionally, Type Ad Fig. 7. Seminiferous epithelium showing spermatogonia type spermatogonia divide by mitosis to form either another pair of type Ad that remain as stem cells, or a pair of type Ap. 3. Type Ap spermatogonia are committed to the differentiation process that will produce sperm. They will proceed through several rounds of mitosis but will not complete cytokinesis. a. This produces many spermatogonia linked by cell bridges. The linked cells are called a cohort and will develop together b. Type Ap spermatogonia is undergo differentiation to become B type spermatogonia. This is the last step in the spermatgonial phase Male Reproductive System Dr. Lalit P. Singh Page 10 of 30 4. Type B spermatogonia will divide by mitosis to next produce preleptotene primary spermatocytes. a. The primary spermatocytes move up into the adluminal compartment of the seminiferous epithelium. b. This is thought to occur by Sertoli cells forming new Sertoli-Sertoli junctions beneath the primary spermatocytes and breaking down the junctions above them. B. Spermatocytes and the Spermatocyte Phase A critical part of gamete production involves the process of meiosis in which the normal diploid (2 copies of each chromosome) content of DNA is reduced to haploid (1 copy of each chromosome). Meiosis involves a recombination of the parental DNA to produce genetic expression in the gametes distinct from that of the parent. In the spermatocyte phase, primary spermatocytes undergo meiosis to reduce both the chromosome number and the amount of DNA. 1. Primary spermatocytes were formed from type B spermatogonia by mitosis. Primary spermatocytes move from the basal to the adluminal compartment of the seminiferous Fig. 7. Seminiferous epithelium showing epithelium. spermatogonia Male Reeproductive System Dr. Lalitt P. Singh Page 11 of 30 2. Primary sp permatocytes have the laargest nucleii of any cells in n the seminiiferous epithhelium. The nucleus is filled with strands s of coondensed andd very basophilicc chromatin (Figs. ( 7, 11). Fig.. 11 Fig. 12 3. permatocytes undergo m Primary sp meiosis I (reduction nal division). Primary Definition: H Homologous chromosom mes are a pairr of spermatoccytes initiate meiosis I byy chromosom mes, one inherited duplicating g their chrom mosomes. Eaach from each p parent, that ha ave corresponding gene sequences chromosom me (46 chromosomes tottal) is and that pair during meio osis. Humans ha ave 22 pairs oof now comp posed of two chromatids (sister homologouss non-sex chromosom mes. chromatid ds) (Fig. 12). Primary spermatoccytes have a normal n num mber of chromosom mes and twicce the total aamount of D DNA compared to interphasse cells. 4. During a prolonged p prophase of o meiosis I (over 2 weeeks), pairs F Fig. 13 Male Reproductive System Dr. Lalit P. Singh Page 12 of 30 of homologous chromosomes come into close opposition. The pairs form groups of four chromatids called tetrads and exchange DNA. This process is called "crossing-over" and it contributes to genetic diversity by creating chromosomal DNA sequences unlike those of the parent (Fig. 13). 5. From metaphase I to anaphase I of meiosis I, the chromosomes, each consisting of two chromatids, line up as in mitosis but instead of dividing, the chromatids remain joined during Fig. 14 division into two cells (Fig. 14). 6. Meiosis I produces two secondary spermatocytes each with 23 chromosomes but with the normal amount of DNA because each chromosome remains composed of two Fig. 15 chromatids (Fig. 15). 7. The secondary spermatocytes are still in the adluminal compartment. They do not undergo DNA synthesis but instead proceed through the phases of meiosis II (equatorial division). It only takes a few hours for secondary spermatocytes to complete meiosis II. Male Reproductive System Dr. Lalit P. Singh Page 13 of 30 8. The brief life of secondary spermatocytes makes it very unlikely they will be seen in any given histological section so you don’t have to identify them. 9. From metaphase II to anaphase II of meiosis II, the chromosomes consisting of two chromatids in the nuclei of secondary spermatocytes line up on the metaphase plate and separate to yield two spermatids (Fig. 16). Fig. 16 10. At the completion of meiosis II each spermatid nucleus contains 23 chromosomes and one-half of the DNA of an interphase somatic cell. Each spermatid is a true haploid cell. 11. One diploid spermatogonium yields four haploid, genetically unique spermatids (Fig. 17). Male Reproductive System Dr. Lalit P. Singh Page 14 of 30 Fig. 17 Male Reproductive System Dr. Lalit P. Singh Page 15 of 30 C. Spermatids and the Spermatid Phase 1. Early (round) spermatids are located in the adluminal compartment of the seminiferous epithelium and are formed from secondary spermatocytes that have completed meiosis II. 2 Early (round) spermatids are small and round with a fairly darkly staining basophilic nucleus (Fig. 7). There will not be any strands of condensed chromatin in the nucleus. Fig. 7 3. Spermatids do not undergo mitosis or meiosis. They undergo a series of biochemical and morphological changes called spermiogenesis. a. The process of spermiogenesis is divided into the: 1) Golgi phase, 2) cap phase, 3) acrosome phase, and 4) maturation stage (Fig 18). Fig. 18 Male Reproductive System Dr. Lalit P. Singh Page 16 of 30 4. During the Golgi phase spermatids produce an acrosomal vesicle from the Golgi apparatus. This is a membrane- bound vesicle that is next to the nuclear envelope. a. The acrosomal vesicle contains hydrolytic enzymes (hyaluronidase, acrosin, neuraminidase) to help penetrate the coverings of the ovum and receptors for the zona pellucida surrounding the ovum. b. The microtubules of the tail (axoneme) begin to form at this stage. 5. During the cap phase the acrosomal vesicle flattens against the round spermatid nucleus to form a cap sometimes visible by LM (Fig 19, left). The tail elongates. Fig. 19 6. During the acrosome phase the acrosome vesicle condenses. a. In addition the nucleus condenses and elongates giving the sperm head a pointed, flattened, appearance (Fig, 19, middle). Male Reproductive System Dr. Lalit P. Singh Page 17 of 30 b. Mitochondria migrate to the initial portion of the axoneme adjacent to the neck to form a spiral wrapping to constitute the "middle piece" of the spermatozoan. 7. In the maturation phase excess cytoplasm is extruded into a residual body, which is usually phagocytized by a nearby Sertoli cell. 8. Changes in the morphology of the nucleus during the acrosome phase results in the formation of the late (elongated) spermatids. The small dense triangular head of the late or elongated spermatids makes them easy to recognize. They are often located very close to the lumen of the seminiferous tubules. 9. The late (elongated) spermatid is shed from the seminiferous epithelium to become a sperm (spermatozoan) (Fig. 7 and Fig. 19, right). Fig. 7 a. Although morphologically mature, the newly-shed sperm are nonmotile and incapable of fertilization. b. Spermatozoa are moved passively along the seminiferous tube lumen by the flow of the fluid secreted by the Sertoli cells and by contractions of the myoid cells of the tunica propria. Male Reeproductive System Dr. Lalitt P. Singh Page 18 of 30 IV. EXCRETOR E RY DUCTS (Fig. 20) A. A Straig ght Tubules 1. Straight tu ubules (tubulli recti) are the t first componen nt of the excretory duct d system. F Fig. 20 2. They are in ntratesticulaar ducts loccated at the ends e of seminifero ous tubules where w they meet the mediastiinum testis. 3. ubules are lin Straight tu ned with simplle cuboidaal epithelium m (Fig. 21). F Fig. 21 B. B Rete Testis T 1. Th he rete testis is an intrateesticular du uct system off interconneccting ep pithelial-lined channels within w the connectivee tissue mediiastinum tesstis (Fig. 22)). Fiig. 22 2. The epitheelial lining iss simple cubboidal, similaar to that of the straigh ht tubules. Male Reeproductive System Dr. Lalitt P. Singh Page 19 of 30 3. The main function of both b the straaight tubules and the retee testes is to o transport sp permatozoa ffrom the sem miniferous tubules to the epididym mal duct. Thhis is done byy the movementt of testiculaar fluid contaaining the spperm throughh the ducts. C. C Effereent Ductules (Fig. 23) 1. The rete teestis merges to form efferent du uctules (ducttuli efferentes)). a. Effferent ductulles are a F Fig. 23 parrt of the excu urrent (ex xtratesticularr) duct system m. b. Effferent ductulles are the brridge betweeen the testess and d the epididy ymis, and wiill merge to form the heaad of the epididym mis. 2. uctules are lined with Efferent du pseudostraatified colum mnar epitheliium that consissts of alternaating groups of tall ciliated d columnar cells c and nonn- ciliated cu uboidal cells (Fig. 24). A An incompletee layer of baasal cells is aalso present. Fig. 24 3. he testicular fluid Most of th f secreteed by the cells in the seminifero ous tubules is reabsorbedd in the efferrent ductuless by the cub boidal cells. Male Reproductive System Dr. Lalit P. Singh Page 20 of 30 4. The efferent ductules are highly convoluted and surrounded by a thin layer of smooth muscle. 5. Sperm movement through efferent ductules is facilitated by the action of the ciliated cells and the contraction of the smooth muscle. D. Epididymal Duct (Fig. 25) 1. The epididymis consists of both the efferent ductules and the duct of the epididymis. The epididymis can be divided Fig. 25 into head, body and tail regions. The epididymal duct is a single highly coiled tube about 5-6 meters long. 2. The epithelium lining the epididymal duct is pseudostratified columnar with principal cells and basal cells. In addition, narrow cells, clear cells, and halo cells are present in small numbers. 3. The apical surface of the principal cells contains non-motile branched stereocilia (Fig. 26) (recall that stereocilia are elongated microvilli, not Fig. 26 true cilia.) Male Reproductive System Dr. Lalit P. Singh Page 21 of 30 4. Major functions of the principal cells include: a. Absorption of testicular fluid that was not absorbed by the efferent ductules, this occurs mainly in the head of the epididymal duct b. Phagocytosis of abnormal spermatozoa and residual bodies c. Secretion of glycerylphosphorylcholine (GPC), glycoproteins, and other molecules that function in the maturation of spermatozoa, leading to motility and the ability to fertilize an oocyte. Mature sperm are stored in the tail. 5. Basal cells may be the precursors of the principal cells, and may also regulate electrolyte and water transport by the principal cells. 6. The entire epididymal duct is surrounded by smooth muscle that gets progressively thicker. In the tail region there are three layers of smooth muscle similar to that found in the ductus deferens (Fig. 27). Fig. 27 Male Reeproductive System Dr. Lalitt P. Singh Page 22 of 30 E. E Ductu us Deferens (Fig. ( 28) 1. The ductus deferens (v vas deferens ) continues ddirectly from m the tail of the epididym mis and is a ccomponent oof the spermatic cord. F Fig. 28 2. The wall of o the ductus defferens consists off a muscosa, musculariss, and adventitia (Fig. 29). 3. The mucossa of the ducctus deferens contains pseudostraatified colum mnar epithelium m. a. Th he epithelium m is sim milar to the pseeudostratifieed F Fig. 29 collumnar epith helium liningg the epididyymal duct. b. Th he epithelium m contains sttereocilia to tthe level of thee ampulla. 4. The lamina propria off the ductus ddeferens conntains elastic fibers. Male Reeproductive System Dr. Lalitt P. Singh Page 23 of 30 5. The muscu ularis of the ductus deferrens is aboutt 1mm thickk. It consists of inner lon ngitudinal, m middle circulaar and outerr nal layers. Peeristalsis of tthis thick muuscular wall longitudin acts to pro opel sperm du uring ejacul ation. 6. The adven ntitia is a loo ose elastic coonnective tissue that blends witth the connecctive tissue oof structuress within the spermatic cord. 7. The ampullla is the dilaated region oof the ductuss deferens adjacent to o the prostate and semin al vesicle. T The epitheliuum in the amp pulla becomees folded andd resembles that of the seminal veesicle. The epithelium e inn the ampullaa of the ductus defferens may have h a secrettory functionn (Fig. 30). Fig. 330 Fig. 31 V. ACCESSOR A RY GLANDS General commen nts: The T accessorry glands aree secretory glands g providding fluid annd nutrients tto support s and nourish the spermatozoaa. These T fluids form the bu ulk of the sem men. All A accessory y glands are dependent upon u testosteerone for theeir full morphologic m cal developm ment and phy ysiological aactivity. Male Reproductive System Dr. Lalit P. Singh Page 24 of 30 A. Seminal Vesicles (Fig. 31) 1. The seminal vesicles are paired, elongate, and highly folded tubular glands. Secretions from seminal vesicles make the largest Fig. 31 contribution (50 - 70%) to the volume of the semen. 2. The epithelium of the seminal vesicles varies but generally it is pseudostratified columnar. The epithelium can vary with aging or with the amount of testosterone present (normal male levels in blood are 300-1,000 ng/dl). 3. The mucosa (epithelium plus lamina propria) is extensively branched and folded, creating a large surface area for secretion (Fig. 32). 4. The epithelium secretes fructose and other Fig. 32 sugars, bicarbonate, prostaglandins, proteins, and amino acids. Fructose is the principal metabolic substrate for sperm. Male Reproductive System Dr. Lalit P. Singh Page 25 of 30 5. The lamina propria is loose vascularized connective tissue with many elastic fibers. 6. The epithelium is surrounded by an inner circular and an outer longitudinal smooth muscle cell layer. 7. The adventitia is collagenous connective tissue containing many elastic fibers. 8. A short excretory duct from the seminal vesicle combines with the ampulla of the ductus deferens as they enter the prostate gland to form the ejaculatory duct (Fig. 33). Fig. 33 B. Prostate Gland (Fig 34) 1. The prostate gland is a single gland and the largest accessory gland. It surrounds the prostatic segment of the urethra (lined with transitional epithelium). Fig. 34 Male Reproductive System Dr. Lalit P. Singh Page 26 of 30 2. The prostate gland is divided into anatomically and clinically distinct zones. It is composed of compound tubuloalveolar glands arranged in groups: the main prostatic glands (peripheral zone), submucosal glands (central zone), and the mucosal glands (transitional zone). The ducts from these glands converge to excretory ducts that open into the prostatic urethra (Fig. 35). Fig. 35 3. The epithelium of the prostate gland can vary between simple columnar and pseudostratified columnar. 4. The prostatic epithelium depends on adequate levels of testosterone. Inadequate testosterone results in a change in the epithelial shape and a loss of or reduction in secretory activity. 5. The epithelial cells secrete prostate-specific acid phosphatase, citric acid, fibrinolysin (liquifies semen), prostate specific antigen (a protease) and amylase. Male Reproductive System Dr. Lalit P. Singh Page 27 of 30 6. The lumens of the prostatic glands may contain calcified bodies called prostatic concretions (Fig. 36). These are a diagnostic feature of the gland. The concretions stain red/pink with the eosin dye in H&E or blue/green using the trichrome stain. 7. The stroma of the prostate gland is infiltrated with smooth muscle fibers. The combination of smooth muscle cells, fibroblasts, elastic and collagen fibers is known as a fibromuscular stroma (Fig. 37). Clinical Correlations: Benign Prostatic Hyperplasia - As men age, the mucosal and submucosal glands (Fig. 8) and the Fig. 36 prostatic stroma begin to hypertrophy, a condition known as benign prostatic hypertrophy. The mechanism is thought to involve stromal cell conversion of testosterone by 5-α reductase to dihydrotestosterone (DHT). The DHT acts as an autocrine factor on the stromal cells and a paracrine factor on the epithelium to produce growth factors. The growth factors cause hyperplasia of both stroma and epithelium. Because these glands are adjacent to the prostatic urethra, the enlarged tissue gradually reduces the lumen of the urethra, resulting in difficulties with urination. Some men are affected by age 50 and most are affected by age 85. Prostate cancer - A common form of cancer in men is adenocarcinoma of the prostate. It affects approximately 30% of the male population over the age of 75. The tumors often develop in the main (outer) glands (Fig. 8), and they may not be detected Fig. 37 early by the patient because the growth may not Male Reproductive System Dr. Lalit P. Singh Page 28 of 30 impinge on the urethra. Frequently the cancer cells enter the circulatory system and metastasize to bone. Carcinoma causes an increase in blood levels of both PSA and prostate specific acid phosphatase, both of which can be used to detect and monitor the progress of the disease. C. Bulbourethral gland Ducts of the bulbourethral (Cowpers) glands are located in the urogenital diaphragm and open into the penile urethra. The bulbourethral glands are all-mucous secretory glands lined by a tall epithelium. VI. PENIS (Fig 38) A. The penis is composed of erectile tissue arranged into two dorsal cylinders (corpora cavernosa) and a smaller ventral cylinder Fig. 38 (corpus spongiosum) containing the urethra. B. The cylinders of erectile tissue are surrounded by a dense collagenous sheath, the tunica albuginea. The skin covering the penis is thin, and contains a subcutaneous layer of smooth muscle. C. The male urethra consists of prostatic, membranous, and penile segments. The corpus spongiosum contains the penile portion of the urethra (Fig. 39). 1. The morphology of the urethral epithelium is variable but is often Fig. 39 stratified or pseudostratified columnar. Male Reeproductive System Dr. Lalitt P. Singh Page 29 of 30 2. Mucous seecreting glan nds (glands off Littré) are common c as ooutpouchinggs of the uretthra. D. D Erectiile tissues are interconneecting vascular spaces co omposed of trabecculae and laccunae (Fig. 40). 4 1. The trabecculae consistt of dense conn nective tissu ue and smooth mu uscle. 2. The lacunaae are vascu ular spaces lined with endotheliu um. F Fig. 40 Clinical C Corrrelation Erectiile dysfunctio on - Two ch hemicals, nitrric oxide (NO NO) and a speciffic phosphod diesterase aree important in the mechaanism of produ ucing erection n. Acetylchooline, a trans mitter releassed by the parasy ympathetic nerves n in thee penis (or cllitoris), acts on the endoth helium of thhe erectile tisssue to produuce NO. Thee NO spread ds into the sm mooth muscle of the trabbeculae and helicine arteriees causing ann enzyme, gu uanylate cycclase, to prodduce cGMP P, which in turn, t relaxes the smooth muscle. Incrreased blood flow throug gh the helicin ne arteries prroduces erecction by filling g of the lacunnae. Counterracting this iis productionn of a speciffic phosphod diesterase thaat breaks dow wn the cGM MP to constrrict the smoo oth muscle. In I men with some types of erectille dysfunctioon, administtration of a pphosphodiestterase inhibiitor, such as sildenafil citrate, suppreesses the desstruction of cGM MP, allowin ng erection to o take place.. Male Reproductive System Dr. Lalit P. Singh Page 30 of 30 References Ross, M. R., Kaye, G.I., Pawlina, W. Histology 4th Ed., Baltimore: Lippincott, Williams & Wilkins, 2003, Chap. 21, "Male reproductive system". Pawlina & Ross, Histology 7th Ed., 2015, Chapter 22 Kerszenbaum, A.L. Histology and Cell Biology, St. Louis, Mosby, 2002, Chap. 20. MacCallum, D.K. Michigan Medical Histology, University of Michigan, Ann Arbor, 2000. Chapter: Male reproductive system 12/05/2022