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The testis is a mixed endocrine and compound, tubular, cytogenic exocrine gland.

General morphology
Very dense CT capsule - tunica albuginea, with an outer mesothelium-covered visceral tunica vaginalis propria. Septa/septula extends from the capsule to the CT mediastinum. In the partitions thus formed (lobuli testis), lie looped, coiled seminiferous tubules (where spermatogenesis occur), lined by germinal epithelium, and feeding via straight tubuli recti into cuboidal epithelium-lined ducts of the rete testis, which lead through the mediastinum to roughly 6-12 ductuli efferentes. These take the spermatozoa to a single, coiled, tubular epididymis lying behind the testis. Between, and outside, the coils of a seminiferous tubule lie blood and lymph capillaries, cells and fibres of CT, and hormone-secreting Leydig interstitial cells. Leydig cells secrete testosterone.

Seminiferous tubule and spermatogenesis:
The stratified germinal epithelium has cells of two kinds:
  1. Spermatogenic cells, quiescent or in the various phases of development;
  2. Sertoli supporting cells; well attached, tall with an irregular columnar form, and a pale ovoid nucleus with a prominent nucleolus ; taking up testosterone ; and controlling spermatogenesis.
Spermatogenesis in the epithelium is initiated by the pituitary hormone FSH, and passes through these stages:
  1. spermatogonium, spheroid cell lying basally, divides mitotically for several generations, then become a
  2. primary spermatocyte, larger, divides by the first meiotic division (to halve the chromosome number to haploid 23 and introduce genetic variety), to produce
  3. secondary spermatocytes, small, soon undergoing the second meiotic division, maintaining the chromosome number at 23, to give
  4. spermatids, smaller and incompletely separated, which, without dividing, metamorphose by the process - spermiogenesis - into
  5. spermatozoa, released into the tubule’s lumen.
The stages are not all seen at any one place in the germinal epithelium ; various combinations exist and are distributed as a mosaic in the tubule’s wall.

Spermatogenesis is protected to a degree by the tight attachments between the capillary endothelial cells and, separately, between the Sertoli cells, creating a two-tiered blood-testis barrier, for example, against immune attack. The inner protected compartment of the seminiferous tubule is the ‘adiuminal’ compartment.

The spermatozoon is a very elongated motile cell, with a cell membrane enclosing the:
  1. acrosomal head cap, with an enzyme - proacrosin - to aid binding to, and penetration of, the zona pellucida of the oocyte;
  2. nucleus, streamlined in shape, with dense chromatin;
  3. neck joining the head (nucleus and head cap) to the flagellar tail, which has the:
    1. middle piece, with an axial axonemal core of microtubules in a eilium-like array, nine dense longitudinal fibres and, outermost, a sheath of mitochondria ending at the annulus;
    2. principal piece, with both longitudinal and circumferential fibres around the axoneme;
    3. end piece, with microtubules like a cilium, but no dense fibres.
Spermiogenesis - whereby the spermatid, a typical cell (except for its chromosomes) becomes a spermatozoon - involves:
  1. construction of the acrosome by the Golgi complex;
  2. the nucleus, thus polarized at one end, condenses and elongates;
  3. at the other end, one of the centrioles initiates formation of the flagellar tail;
  4. mitochondria migrate to form a sheath in the tail;
  5. excess cytoplasm is shed as a residual body;
  6. the head of the spermatid throughout spermiogenesis stays held in a recess in a Sertoli cell.
Sertoli cell functions: to protect, nourish, and release the spermatids; to phagocytose residual bodies; and to make androgen-binding protein, fluid, and inhibin to influence pituitary FSH release.

Endocrine testis
  1. Leydig cells, eosinophilic, with much smooth ER, lipid droplets, and crystals of Reinke, lie outside the tubules’ BLs, constituting a diffuse, steroid-secreting endocrine gland.
  2. Leydig interstitial cells are controlled by gonadotrophic interstitial cell-stimulating hormone (ICSH/LH) of the anterior pituitary, and produce the androgenic hormone - testosterone, responsible for:
  3. (a) Spermatogenesis;
    (b) development and maintenance of reproductive ducts and accessory glands;
    (c) secondary sexual characteristics;
    (d) male mating behaviour;
    (e) general anabolic effects on metabolism.

Paths Traversed By Spermatozoa

Efferent ducts/Ductuli efferentes are unevenly lined by simple, columnar, epithelial cells, in groups of tall ciliated and short secretory; the wall has circular smooth muscle; functions - reabsorption of the fluid used to move sperm out of the testis; maturation of the sperm.

Epididymis/ductus epididymidis is regularly lined by tall, absorptive, columnar cells with non-motile stereocilia, and smaller basal cells, together forming a pseudostratified epithelium. (Epididymis stores, matures and provides progressive motility to sperms)

Ductus deferens/vas deferens 1 Lined by an epithelium similar to that of the epididymis, on a lamina propria; in the ampulla, this mucosa has many folds most of the very thick wall is smooth muscle: inner, longitudinal; middle, circular; outer, longitudinal; adventitia of CT binds it to nerves, blood and lymphatic vessels, and the skeletal cremaster muscle, to comprise the spermatic cord function - rapid transport of sperm during ejaculation, under sympathetic control.

Ejaculatory ducts: Each occurs after a dilation of the ductus d. - the ampulla; lined by pseudostratified or simple columnar epithelium on CT, without smooth muscle. Ducts open into the prostatic urethra through a hillock on the posterior urethral wall - verumontanum/colliculus seminalis, with its blind recess - prostatic utricle (utriculus masculinus).

Three portions; prostatic, membranous, and cavernous (penile);

Male Accessory Glands

Prostate gland: Lobulated by septa of CT, with much smooth muscle. Divisible, with histology and rectal-probe ultrasound, into several zones: peripheral (prone to cancer), peri-urethral (subject to benign prostatic hypertrophy (BPH)), and an anterior non-glandular fibromuscular zone. Glandular acini open into many ducts, entering the urethra individually, thus the prostate is a collection of compound tubuloacinar glands. Laminated, rounded, prostatic concretions (originally glycoprotein, but later calcifying) - corpora amylacea - develop in some acini as age increases.

Functions - secretion of a watery fluid to dilute the semen (form 20% of seminal volume); the protease - prostate-specific antigen (PSA) - liquifies the gel from the seminal vesicles to free the sperm; the roles of the citrate (the anionic counterpart to Na+) and acid phosphatase are uncertain. PSA serves as a serum marker of prostatic cancer, if excessive for the man’s age. The stroma has abundant smooth muscle to make the prostate a self-squeezing gland, without the need for myoepithelial cells. Stroma interacts with the epithelium in the control of growth and secretion, and is a major player in benign prostatic hypertrophy.

Seminal vesicles are coiled, convoluted, tubular structures; with a very extensively folded mucosa, having a pseudostratified, columnar, secretory epithelium. Functions - secretion of a viscid gel composed of seminogelin, with fructose to provide energy for the sperm, and prostaglandins that may alter contractions in the female tract (AFP-60- Seminal vesicle contributes 60% of the seminal volume containing ascorbic acid, fructose and prostaglandins).

Cowper’s bulbo-urethral glands are compound, tubulo-alveolar gland making special mucus, to lubricate and prepare the urethra for ejaculation.


Connective tissue capsules or tunicae albugineae enclose three roughly cylindrical erectile bodies - two corpora cavemosa penis, and one corpus spongiosum/cavemosum urethrae. The two corpora cavemosa are incompletely separated by a sagittal pectiniform septum. Their endothelium-lined venous sinuses, between a - meshwork of dense trabeculae of muscular CT, can be engorged with blood from helicine (coiled) arteries causing erection.

Corpus spongiosum (a) is erectile, but less turgid than the corpora cavernosa; (b) has less smooth muscle in the CT trabeculae; (c) originates proximally as the bulbus urethrae and (d) extends distally to form the bulbous glans. Occupied by many veins and nervous receptors, and covered by stratified squamous epithelium, variably keratinized ; (e) ensheaths the cavernous/penile urethra, lined by stratified columnar and finally stratified squamous epithelium.

Erection and detumescence are controlled by autonomic nerve fibres to the arteries and trabeeular smooth muscle. Erection results from parasympathetically directed trabecular and arterial relaxation, and passive occlusion of the veins draining the corpora.

Sensory nerves serve the glans, skin and deep receptors.

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