The testis • Is oval structure surrounded anterolaterally by peritoneal outpouching called tunica vaginalis. • Deeper to the tunica vaginalis is a pasule of dense irregular collagenous CT called tunica albuginea.Posteriorlly it forms mediastinum testis, from which septa radiate to subdivided each testis into 250 compartment (lobuli testis). • Immediatlly deep to tunica albuginea there is a loose vascular CT. tunica vasculosa. • Each lobule has 4 seminiferous tubules. • Each tubule is surrounded by vascular loose CT. (extended from tunica vasculosa) called tunica propria that has fibroblasts, myoid cells and interstitial cells of Leydig.
Seminiferous tubules • They are highly convoluted and formed of stratified epithelium which is formed of two types of cells 1-Spermatogenic cells(spermatogonia,1ry spermatocytes, 2ry spermatocytes, spermatids and spermatozoa) and single layer of 2-Sertoli cells. • They have well developed basal lamina. • They are separated from each others by vascular CT. (tunica propria) rich in collagen-I and fibroblasts. • Myoid cells (as smooth muscle) may be present. • Each tubule is divided into peripheral (abluminal) and central (adluminal) compartments.
Compartments of seminifrous tubules • The lateral cell membranes of adjacent Sertoli cells form occluding junctions, that divide the lumen of the tubules into outer basal(abluminal) compartment and inner (adluminal) compartment. • The zonulae occludenes form blood-testis barrier. • The basal compartment contains spermatogonia (small diploid germ cells). • The adluminal compartment contains primary spermatocyts, seconary sprmatocytes, spermatids and sperms.
Spermatogonia • They are small diploid germ cells in basal compartment that are influenced by testosterone at puberty. • Types of sermatogonia: • Dark type A : are small dome-shaped cells with oval flat nuclei and abundant heterochromatin. They are reserve (stem) cells. 2. Pale type A :Their nuclei are oval & flat and have abundant euchromatin, by testesterone they undergo mitosis to give rise more type A and type B spermatogonia. 3. Type B :As type A with round nuclei. By mitosis they give primary spermatocytes.
Primary spermatocytes • Once they are formed they migrate to the adluminal compartment forming occluding junctions with Sertoli cells to maintain the blood-testis barrier. • They are the largest cells in the tubules with large vesicular nuclei. • They duplicate their chromosomes (4n DNA) and diploid (2n) chromosomes number, then enter the first meiotic division to give secondary spermatocytes.
Secondary spermatocytes • They are small cells because they are short lived (aren’t seen in the tubules). • They have 2n DNA and haploid number of chromosomes • They are quickly enter the second meiotic division to give spermatids (that have 1n DNA) and haploid number of chromosomes. • Spermatids • They are small round haploid cells. • They have abundant rER, mitochondria and Golgi. • By spermiogensis they are transformed into sperms.
Spermatogenesis • It the process of transformation of spermatogonia to give rise spermatozoa. • It is divided into three phases: 1-Spermatocytogenesis (differentiation of spermatogonia to 1ry spermatocytes). 2-Meiosis (reduction division of 1ry and 2ry spermatocytes to produce spermatids). 3-Spermiogenesis (transformation of spermatids into sperms)
Spermiogenesis • Is the transformation of spermatids into sperms (without any division). • It is formed of the following phases: 1-Glgi phase (formation of acrosomal vesicles containing hydrolytic enzymes bound to the nuclear envelope. Formation of flagellar axoneme) 2-Cap phase (acrosomal cap formation). 3-Acrosomal phase (nuclear condensation, elongation of the cell and shifting of mitochondria) . 4-Maturation phase (shedding of spermatid cytoplasm that phagocytosed by Sertoli cells).
Spermatozoon • Is formed of Head and Tail. • The head: is surrounded by plasmalemma and contains electron-dense nucleus that contains 23 chromosomes and an acrosome that partially surrounds the ant. Aspect of the nucleus. • The tail: Is subdivided into; • 1-Neck, it is small and contains 9 columns of connecting piece that encircles the centrioles. • 2-The middle piece, between the neck and the principle piece. It contains the mitochondrial sheath that encircles the outer dense fibers and the central axoneme. It stops at the annulus in which plasmalemma adheres
3- The principle piece • Is the longest segment of the tail. • It contains the axoneme that is surrounded by 7 outer dense fibers and by fibrous sheath. 4-the end piece Is composed of axoneme that surrounded by plasmalemma
Sertoli cells • They are tall columnar cells with lateral and apical cell membrane infoldings and zonulae occludentes junctions. • They have oval clear basally located nuclei with central nucleolus. • They are rich in sER, mitochondria, Golgi apparatus, cytoskeleton and endolysosomal vesicles. • They house inclusion products • (crystalloids of Charcot-bottcher)
Functions of Sertoli cells • Physical and nutritional support of germ cells. • Phagocytosis of cytoplasmic reminants of spermiogenesis. • Establishment of blood testis barrier. • Synthesis and secretion of androgen-binding protein. • Synthesis and secretion of inhibin (inhibits FSH). • Synthesis and secretion of testicular transferrin. • Synthesis and secretion of antimullerian hormone. • Secretion of a fructose-rich medium that nouriches spermatozoa
Interstitial cells of Leydig • They are scattered among the vascular CT. in which the seminefrous tubules are embeded. • They produce testesterone. • They are polyhedral cells that contain mitochondria with tubular cristae, sER, lysosomes, lipid droplets, lysosomes, proxisomes and crystals of Reinke
Genital ducts 1-Intratesticular ducts. • They connect the Seminiferous tubules with the epididymis. • They are: A-Tubuli recti, wich are short straight tubules that transport the sperms from the seminifrous tubules to the rete testis. • They are lined with Sertoli cells in their first half and by simple cuboidal cells in the second half. • The cuboidal cells have microvilli and a single flagellum.
B-rete testis, is lined by a simple cuboidal epithelium with microvilli and a single flagellum. • C-Ductuli efferentes, are short tubules that pierce the tunica albuginea. They are lined by nonciliated cuboidal cells alternating with ciliated simple columnar epithelial. Simple epithelium rests on basal lamina that separates it from the thin loose CT that is surrounded by a thin layer of smooth muscle cells
2-Extratesticular ducts They are: A-Epididymis,( a thin long highly convoluted tubule). It is lined by pseudostratified columnar epithelium that is formed of tow types of cells: a-Basal cells which are short pyramidal cells with round nuclei (heterochromatin). They are stem cells. b-Principal cells are columnar to cuboidal cells with basal pale nuclei. They are rich in rER &sRE. They have stereocilia (non-motile microvilli). They absorb the luminal fluid, act as phagocytic cells and secrete glycoprotein that inhibits capacitation of sperms. Under the basal lamina there is loose CT which is surrounded with a layer of circularly arranged smooth muscle
B-Ductus (vas) deference, it is a thick walled muscular tube with small irregular lumen. • It is formed of three layers: 1-Mucosa, of pseudostratified columnar epith. With stereocilia, basal lamina and fibroelastic CT. 2-Muscularis, three layers, inner and outer longitudinal layers and middle circular layer. 3-Fibroelastic loose CT(adventitia). The terminal end is dilated to form ampulla that joined with seminal vesicle to form the ejaculatory duct.
C-Ejaculatory duct • It is a short, straight tubule that enters and is surrounded by the prostate and pierces it. • Its lumen is lined by a simple columnar epithelium, basal lamina and sub-epithelial CT. • It has no smooth muscle in its wall.
Accessory genital glands • They are paired seminal vesicles, a single prostate and paired bulbo-urethral (Cowper’s glands). A-Prostate gland It is pierced with urethra and ejaculatory ducts. It is surrounded with dense irregular collagenous capsule that is rich in smooth muscle cells. The CT. stroma is formed of CT. rich in smooth muscle. It is formed of 30 to 50 compound tubuloalveolar glands.
It is formed of the following concentric layers: * mucosal glands, closest to urethra * submucosal, peripheral and larger than mucosal part * Main gland, the outermost and largest part. The secretory portion is lined with simple to pseudostratified columnar epithelium, their lumen contains calcified glycoprotein prostatic concretions (corpora amylacea). The prostatic secretion is rich in, acid phosphatase, lipids, proteolytiic enzymes, fibrinolysin and citric acid.
B-Seminal vesicles • They secrete 70% of the ejaculate. • They are highly coiled tubular gland. • They have highly folded mucosa that is lined by pseudostratified columnar epith. • The epith. Cells have RER, lipids and lipochrome pigments (responsible for yellow color of semen). • They have subepith. Fibroelastic CT.that is surrounded by inner circular and outer longitudinal smooth muscle. • They are covered by fibro-elastic CT.
C-Bulbourethral (Cowper’s) glands • They are located at the root of penis. • Their capsule is formed of fibro-elastic CT., smooth muscle and skeletal muscle. • They are formed of compound tubulo-alveolar glands that are lined by simple cuboidal to simple columnar epithelium. • They secrete thick, slippery fluid to lubricate the penile urethra.
Penis It is formed of three columns of erectile tissues (vascular spaces separated by trabeculae of CT. and smooth muscle), each enclosed by dense fibrous CT. tunica albuginea. There are two dorsally located corpora cavernosa and ventrally located single corpora spogiosum through which the urethra passes (penile urethra). It is covered with thin skin that is formed of epidermis and dermis but no hypodermis.