Male Reproductive System Histology PDF

Histology of Male reproductive system Dr Abdul Hakim Elnfati Spring -2023  References book: Exam sources: lecture notes + details in references book. © 2009 The McGraw-Hill Companies, Inc. All rights reserved https://histologyguide.com//...

Histology of Male reproductive system Dr Abdul Hakim Elnfati Spring -2023  References book: Exam sources: lecture notes + details in references book. © 2009 The McGraw-Hill Companies, Inc. All rights reserved https://histologyguide.com//slidebox/slidebox.html  Lecture outline: Part 1: Introduction and testis histology. Part 2: Spermatogenesis. Part 3: Spermiogenesis. Part 4: spermatogenesis waves + sertoli cells. Part 5: Excretory Genital Ducts. Part 6: Accessory Glands. Part 7: Penis. © 2009 The McGraw-Hill Companies, Inc. All rights reserved  Histology of Male reproductive system Part 1: Introduction and testis histology.  consists of the: – Testes. – Genital ducts. – Accessory glands. – Penis. The BioDigital Human is an interactive 3D software https://human.biodigital.com/gar/anatomy/male/reproductive-system/  Testis: Develop in the abdominal pelvic cavity of fetus Descend into scrotal sac shortly before or after birth Scrotum. The bag of skin that holds and helps to protect the testicles. The testicles make sperm and, to do this, the temperature of the testicles needs to be cooler than the inside of the body. This is why the scrotum is located outside of the body. 31-8 The scrotal sac is constituted of a thin layer of external skin, which contains more pigment than the surrounding skin, many sebaceous and sweat glands as well as some hair. 1. Skin 2. Dartos muscular layer: two coherent plexuses of smooth muscle cells; contracts in cold or during sexual stimulation 3. External spermatic fascia 4. Cremasteric muscle ( bundles of skeletal muscle, 5. Internal spermatic fascia 6. Parietal layer of tunica vaginalis  Testis Each testis is oval surrounded by a fibrous capsule called tunica albuginea 31-10  Each testis ( testicle) is surrounded by a dense connective tissue capsule, the tunica albuginea. Tunica albuginea thickens on the posterior side to form the mediastinum testis. From this fibrous region, septa penetrate the organ and divide it into about 250 pyramidal compartments or testicular lobules. Each lobule contains:  connective tissue with endocrine interstitial cells (or Leydig cells) secreting testosterone.  one to four highly convoluted seminiferous tubules in which sperm production occurs.  250 testicular lobules separated by connective tissue stroma. Each lobule consists of 1-4 seminiferous tubules embedded in a loose connective tissue. 31-13 Interstitial Tissue: The interstitial tissue of the testis between the seminiferous tubules consists of sparse connective tissue containing fibroblasts, lymphatics, and blood vessels including fenestrated capillaries. During puberty interstitial cells, or Leydig cells, develop as large round or polygonal cells with central nuclei and eosinophilic cytoplasm rich in small lipid droplets. These cells produce the steroid hormone testosterone.  A plastic section shows lipid droplets filling the cytoplasm of the clumped interstitial cells (IC), or Leydig cells, in the connective tissue (CT) between tubules. Such cytoplasm is typical of steroidsecreting endocrine cells and here indicates cells actively secreting testosterone. The epithelium of a nearby seminiferous tubule is immediately surrounded by myoid cells (M). (X400; PT) Seminiferous Tubules Each testis has from 250 to 1000 such tubules in its lobules. each tubule measures 150-250 μm in diameter and 30-70 cm in length. The combined length of the tubules of one testis totals about 250 m. Sperm are produced in the seminiferous tubules at a rate of about 1500 sperm/ sec. ST Each tubule is linked by a very short, narrower segment, the straight tubule RT (ST), to the rete testis (RT), which embedded in the mediastinum testis. About 10-20 efferent ductules connect the rete testis to the head of the epididymis (EP). EP Lobules converging at rete testis. The dense capsule of the testis, the tunica albuginea, thickens on the posterior side as the mediastinum (M) testis, from which many thin septa (S) subdivide the organ into about 250 lobules. Each lobule contains one to four convoluted seminiferous tubules (ST) in a sparse connective tissue interstitium. Each tubule is a loop attached by means of a short straight tubule to the rete testis (RT), a maze of channels embedded in the mediastinum testis. From the rete testis the sperm move into the epididymis. (X60; H&E) Testis, low power, seminiferous tubules  Each seminiferous tubule is lined with; 1- a complex, specialized Myoid stratified epithelium called germinal or spermatogenic epithelium. 2- Large nondividing Sertoli cells ,which physically and metabolically support developing sperm cells. The basement membrane of this epithelium is covered by fibrous connective tissue, with an innermost layer containing flattened, smooth muscle- like myoid cells which allow weak contractions of the tubule. Seminiferous tubules (ST) are surrounded by stroma containing many interstitial cells (IC), typically located near capillaries, which secrete androgens. The seminiferous tubule wall consists of a unique germinal epithelium composed of columnar Sertoli cells and dividing spermatogenic stem cells. Seen around the seminiferous tubules are myoid cells (M) with elongated nuclei. (X400; H&E)  Histology of Male reproductive system Part 2: Spermatogenesis.  Spermatogenesis: sperm formation Begins at puberty several million sperm/day (1500 sperm/ second) 64-70 days total period for one mature sperm. Three stages: – Formation of spermatocytes – Meiosis – Spermiogenesis 23 Spermatogenesis Spermatogonia (46 chromosomes) Mitosis – makes primary spermatocytes Undergo meiosis  two secondary spermatocytes Divides – two spermatids = 4 spermatids Develop flagella to become mature sperm cells with 23 chromosomes 31-24  Spermatogonia: Sperm production begins at puberty with proliferation of stem and progenitor cells called spermatogonia, small round cells about 12 μm in diameter. These cells occupy a basal niche in the epithelial wall of the tubules, next to the basement membrane and closely associated with Sertoli cell surfaces. Different stages of spermatogonia development can be recognized by subtle changes in shape and staining properties of their nuclei. Spermatogonia with dark, ovoid nuclei act as stem cells (typeA spermatogomia), dividing infrequently and giving rise both to new stem cells and to cells with more pale-staining, ovoid nuclei that divide more rapidly as transit amplifying (type A progenitor spermatogonia) cells. type A spermatogonia (progenitor) undergo several divisions that leave most of the cells interconnected as a syncytium. These become type B spermatogonia, which have more spherical and pale nuclei. Spermatogonia The dark type A spermatogonia or reserve stem cells (Ad) which rarely divide. Their intensely stained nuclei show a lightly stained central spherical cavity. The pale type A spermatogonia or renewing stem cells (Ap) with their ovoid nuclei containing lightly stained homogeneous and finely granulated chromatin. These type Ap cells divide regularly by mitosis to produce new type Ap cells or type B spermatogonia. Stain: H–E Magnification: ×900  Primary Spermatocyte Each type B spermatogonium undergoes a final mitotic division to produce two cells that grow in size and become primary spermatocytes, which are spherical cells with euchromatic nuclei. Primary spermatocytes replicate their DNA, so each chromosome consists of duplicate chromatids, and enter meiosis, during which homologous chromosomes come together in synapsis, DNA recombination occurs, and two rapid cell divisions produce haploid cells. The primary spermatocyte has 46 (44 + XY) chromosomes. Soon after their formation, these cells enter the first meiotic prophase that lasts about 3 weeks. The primary spermatocytes are the largest cells of the spermatogenic lineage and are characterized by the presence of partially condensed chromosomes in various stages. The stages of Primary Spermatocyte: T.S in seminiferous tubules  secondary Spermatocyte Primary spermatocyte in the first meiotic division produces smaller cells called secondary spermatocytes with only 23 chromosomes (22 + X or 22 + Y). Secondary spermatocytes are rare in testis sections because they are very short-lived cells that remain in interphase only briefly and quickly undergo the second meiotic division and produce spermatids.  Histology of Male reproductive system Part 3: Spermiogenesis.  Spermiogenesis: Division of each secondary spermatocyte separates the chromatids of each chromosome and produces two haploid cells called spermatids each of which contains 23 chromosomes. Spermatids undergoes to spermiogenesis (the final stage of sperm production. Maturation step, no cell division. The maturation include formation of flagellum, acrosome, compact nucleus.  The acrosome is a specialized type of lysosome containing hydrolytic enzymes, mainly hyaluronidase and a trypsin-like protease called acrosin. These enzymes are released when a spermatozoon encounters an oocyte and the acrosomal membrane fuses with the sperm’s plasma membrane. They dissociate cells of the corona radiata and digest the zona pellucida, both structures that surround the egg. This process, the acrosomal reaction, is one of the first steps in fertilization.  Chromatin condensation in spermiogenesis : Nuclei become more elongated and very highly condensed, with the histones of nucleosomes replaced by small basic peptides called protamines. Nucleosomes Condensed chromatin protamine Transition Histones protein Human sperm nucleus Li et al, 2008  Flagellum growth continues as the tail and mitochondria aggregate around its proximal region to form a thickened middle piece where the ATP for flagellar movements is  Sperm cells – Head – Tail Inactive Nucleus with 23 Flagellum that propels chromosomes sperm forward Acrosome – enzyme-filled sac – Helps sperm penetrate ovum – Midpiece Mitochrondria that generate cell’s energy 31-41  Histology of Male reproductive system Part 4: Spermatogenesis waves + sertoli cells. -Spermatogeneic cells wave.  There are 12 possible histological section in seminiferous tubule based on type of germ cells. Retinoic acid  Sertoli cells: Tall “columnar” epithelial cells that nourish the spermatogenic cells and, their nuclei are typically ovoid or triangular, euchromatic. Sertoli cells adhere to the basal lamina and their apical ends extend to the lumen.  divide the seminiferous tubules into two (basal and adluminal) compartments. Each Sertoli cell supports 30-50 developing germ cells.  Blood-testis barrier: Sertoli cell function are elaborate tight junctions between their basolateral membranes that form a blood-testis barrier within the seminiferous epithelium. This physical barrier prevents autoimmune attacks against the unique spermatogenic cells, which first appear after the immune system is mature and central self-tolerance is well established. Spermatogonia lie in a basal compartment of the tubule, below the tight junctions and not sealed off from the vascularized interstitial tissue. Newly formed primary spermatocytes temporarily disassemble the adhesion molecules of the local occluding junctions and move into the tubule’s adluminal compartment  Sertoli cells functions: Sertoli cells have three general functions: Support, protection, and nutrition of the developing spermatogenic cells: spermatocytes, spermatids, and developing sperm depend on Sertoli cells for production or transport into the lumen of metabolites and nutritive factors such as the iron-transport protein transferrin. protect spermatogenic cells from circulating immune components ( blood testis bareiar).  Exocrine and endocrine secretion: Sertoli cells continuously release into the seminiferous tubules water that carries new sperm out of the testis. Production of androgen-binding protein (ABP), which concentrates testosterone to a level required for spermiogenesis. As endocrine cells, they secrete the 39-kDa glycoprotein inhibin, which feeds back on the anterior pituitary gland to suppress FSH synthesis and release. In the fetus Sertoli cells also secrete a 140-kDa glycoprotein called müllerian-inhibiting substance (MIS) that causes regression of the embryonic müllerian  Histology of Male reproductive system Part 5: Excretory Genital Ducts. 2- Excretory Genital Ducts 2-vas deferens. 1- Epididymis. 3- Urethra.   Epididymis: Epididymis The long, coiled duct of the epididymis, surrounded by connective tissue. lies in the scrotum along the superior and posterior sides of each testis. About 4-5 m in length. it includes a ( head, body and tail). head region where the efferent ductules enter, a body, and a tail opening into the ductus deferens.  Epididymis function: storage and secretion. Passage of sperm through the duct of the epididymis normally takes 2-4 weeks, during which spermatozoa undergo maturation and acquire the ability to fertilize. Important changes within sperm while passing through the epididymis include: Development of the competence for independent forward motility, Maturation of the acrosome. Biochemical and organizational changes within the nucleus and cell membrane.   Histology of Epididymis: Lined with pseudostratified columnar epithelium composed of Rounded basal cells and columnar cells with stereocilia. basal lamina loose connective. smooth muscle cells. The stereocilia in the epididymis are non-motile. These membrane extensions increase the surface area of the cell, allowing for greater absorption and secretion.   Epididymis histology: (a): The epididymis contains a long, highly coiled duct in which sperm are temporarily stored and undergo the final maturation steps required for their ability to fertilize an egg. The duct of the epididymis (DE) is enclosed by connective tissue that contain many blood vessels (V) and the connective tissue is covered by a capsule and the tunica vaginalis (TV). The duct is lined by a pseudostratified columnar epithelium with long stereocilia (arrows). The columnar cells are very tall and the stereocilia very long in the head of the epididymis and both gradually shorten toward the tail. X140. H&E.   Epididymis histology: (b): The higher power micrograph shows the duct is surrounded by a thin circular layer of smooth muscle cells and the lumen is seen to contain sperm (S). The smooth muscle becomes thicker and a longitudinal layer develops in the body and tail of the epididymis. X400. H&E. (c): Another section of the smooth muscle (SM) and wall of the duct shows two abundant cell types in the epithelium: the tall principal cells with stereocilia and small basal cells (B) on the basal lamina. Macrophages and intraepithelial lymphocytes are also commonly seen in the epididymal duct. X500. H&E.   vas deferens: a long straight tube with a thick muscular wall. continues toward the prostatic urethra and empties into it. It is characterized by a narrow lumen and a thick layer of smooth muscle. Its mucosa is folded longitudinally and is lined along most of its length by pseudostratified columnar epithelium with sparse stereocilia. The lamina propria is rich in elastic fibers and the very thick muscularis consists of longitudinal inner and outer layers and a middle circular layer. The muscles produce strong peristaltic contractions during ejaculation which rapidly move sperm along this duct from the epididymis.   vas deferens histology : The micrograph of a vas deferens in cross- section shows that it consists of a mucosa (M), a thick muscularis with inner and outer layers of longitudinal smooth muscle (L-SM) and an intervening layer of circular smooth muscle (C-SM), and an external adventitia (A).   vas deferens histology : (b): The lamina propria (LP) is rich in elastic fibers and the thick epithelial lining (E) shows longitudinal folds.   vas deferens histology : (c): Higher magnification of the mucosa shows that the epithelium is pseudostratified with basal cells and many columnar cells with some stereocilia. X400. H&E.  Histology of Male reproductive system Part 6: Accessory Glands.  3- Accessory Glands: The accessory glands of the male reproductive tract produce secretions that are added to sperm during ejaculation to produce semen and which are essential for reproduction. The accessory genital glands are:  seminal vesicles (2).  prostate gland (1).  bulbourethral glands (2). these sets of glands connect to the ductus deferens or urethra. The first two types of glands contribute the major volume to semen and the latter produces a secretion that lubricates the urethra before ejaculation.  The seminal vesicles are paired exocrine  seminal vesicles glands that secrete most seminal fluid, including sperm nutrients. The two seminal vesicles consist of highly tortuous tubes about 15 cm in length. The seminal vesicles are exocrine glands that produce a viscid, yellowish secretion containing: fructose, citrate, inositol, prostaglandins, fibrinogen, as well as enzymes and other proteins. These semen components, which typically make up about 70% of the ejaculate, provide nutrient energy sources for the sperm, coagulate semen after ejaculation, and affect activity of the female reproductive tract. The height of the seminal vesicle epithelial cells and their degree of secretory activity are dependent on adequate levels of testosterone.  seminal vesicles histology: The unusual mucosa displays a great number of thin, complex folds that fill most of the lumen. The folds are lined with simple or pseudostratified columnar epithelial cells rich in secretory granules. The lamina propria contains elastic fibers and is surrounded by smooth muscle with inner circular and outer longitudinal layers.  seminal vesicles histology: a): A low-power micrograph shows that each consists of a highly coiled duct surrounded by two layers of smooth muscle (SM) that expel the luminal contents during ejaculation. The mucosa characteristically displays thin primary, secondary, and tertiary folds (arrows) that give the lumen (L) a distinctive appearance. X20. H&E.  seminal vesicles histology: (b, c): Both micrographs show that the folds include smooth muscle (SM) covered by a thin lamina propria (LP) and an epithelium. The epithelial cells are simple or pseudostratified columnar, varying with activity and location in the gland, and contain lipid droplets, secretory granules,  The prostate gland: is a dense organ surrounding the urethra below the bladder. It is approximately 2 cm x 3 cm x 4 cm in size and weighs about 20 g. The prostate is a collection of 30–50 branched tubuloalveolar glands, all surrounded by a dense fibromuscular stroma covered by a capsule. The glands are arranged in concentric layers around the urethra: the inner layer of mucosal glands. an intermediate layer of submucosal glands. a peripheral layer with the prostate's main glands. Ducts from individual glands may converge but all empty directly into the prostatic urethra, which runs through the center of the prostate. The prostate has three zones, corresponding to the glandular layers: transition zone occupies about 5% of the prostate volume, surrounds the prostatic urethra, and contains the mucosal glands emptying directly into the urethra. central zone occupies 25% of the gland's volume and contains the submucosal glands with longer ducts. peripheral zone occupies about 70% of the prostate and contains the main glands with still longer ducts.  The tubuloalveolar glands of the prostate are lined by a simple or pseudostratified columnar epithelium. The glands produce prostatic fluid containing various glycoproteins and enzymes and store this fluid for expulsion during ejaculation. rich fibromuscular stroma surrounds the glands. The prostate is surrounded by a fibroelastic capsule. (a): The prostate has a dense fibromuscular stroma (S) in which are embedded a large number of small tubuloalveolar glands (G). (b): A micrograph of one gland, including a corpus amylaceum (CA) concretion, shows a secretory simple or pseudostratified columnar epithelium (E) surrounded by lamina propria (LP), which is in turn surrounded by smooth muscle (M). (c): Higher magnification shows the lamellar nature of a corpus amylaceum (CA) and the columnar epithelium underlain by sparse lamina propria.  Histology of Male reproductive system Part 7: Penis  Penis The main components of the penis are three cylindrical masses of erectile tissue, plus the penile urethra, surrounded by skin. Two of these cylinders—the corpora cavernosa—are placed dorsally. The other—the corpus spongiosum—is ventral and surrounds the urethra. At its end the corpus spongiosum expands, forming the glans. Most of the penile urethra is lined with pseudostratified columnar epithelium. The corpus spongiosum (CS) is on the ventral side of the penis and surrounds the urethra (U). Two corpora cavernosa (CC) fill the dorsal side and all three bodies of cavernous or erectile tissue are surrounded by dense, fibrous tunica albuginea (TA). Along the dorsal side run the major blood vessels (V) and deep in each mass of erectile tissue are smaller blood vessels (V), including the central arteries. Externally the penis is covered by skin (S) attached to the tunica albuginea or neighboring connective tissue (a): The micrograph shows the corpus spongiosum (CS) surrounding the penile urethra (PU) with its longitudinally folded wall. Near the penile urethra are small urethral glands (UG) with short ducts for the release of a mucus-like secretion into the urethra during erection. These glands supplement the similar function of the larger, paired bulbourethral glands. In one of the two dorsal corpora cavernosa (CC) small helicine arteries (HA) are visible. The bodies of erectile tissue are ensheathed by dense, nonelastic tunica albuginea (TA) connective tissue. X100. H&E