Objectives
- Identify histological features of the following viscera: Testes, Efferent ductules, Epididymis, Ductus Deferens, Seminal vesicles, Prostate, Penis
- Review histologic features of the urethra (also explained in the urinary system section)
Overview
Disclaimer: The following information describes anatomical features a reproductive system in which an individual is genetically XY with no variation or surgical intervention and contains the above listed viscera. The term “male” will be used to refer to this collection of viscera.
The general function of the male reproductive system is to produce androgens, or sex hormones and produce male gametes, sperm. Production of sperm occurs through spermatogenesis (male meiosis) and spermiogenesis in the testes. Sperm continue to mature and prepare for fertilization as they move through the epididymis into the ductus deferens. Sperm mix with semen components produced by the seminal vesicles and prostate in the prostatic urethra. Semen with all components moves through the membranous urethra, spongy urethra and out of the external urethral orifice in the glans (distal) penis.
Testes: paired organs that develop in the presence of the SRY gene in association with the urinary system in the posterior abdominal wall before moving into the scrotum just prior to birth. Structure:
- Tunica vaginalis– most outer covering, continuation of the peritoneum
- Tunica albuginea– dense Ct capsule
- ∼250 lobules separated by CT septum
- Seminiferous tubules (convoluted loops) fill lobules and consist of specialized epithelium (see below)
- Rete testes– seminiferous tubules come together in anastomosing channels just before sperm travel into excurrent duct system
Seminiferous epithelium consists of spermatogonia (stem cells) lying on a basement membrane surrounded by myoid cells. Spermatogonia undergo steps of spermatogenesis (meiosis) as they move towards the lumen. Sertoli cells provide the niche needed for this process. Once cells reach the spermatid stage, they undergo spermiogenesis which is a massive morphologic and physiologic change including formation of the acrosome cap, removal of excess cytoplasm with the help of the manchette, and formation of the flagellum (tail). Spermatids are released into the lumen before traveling to the excurrent duct system where they undergo more maturation including gaining motility in the epididymis. A final physiologic change occurs just before fertilization within the uterine tubes of the female known as capacitation. Leydig cells are found outside the seminiferous tubules and are responsible for testosterone production.
Excurrent duct system:
- Efferent ductules– first part of excurrent duct system found in head of epididymis. Pseudostratified columnar epithelium with tall and short cells creating a saw-tooth appearance, included ciliated cells and cells with microvilli. Smooth muscle layer surrounding epithelium.
- Epididymis– site where sperm gain motility, lies along superior and posterior surface of testes, divided into a head, body and tail. Pseudostratified epithelium consisting of tall principal cells with stereocilia (extended microvilli) and basal cells. Can also find migrating lymphocytes, halo cells. Increasing layers of smooth muscle surround the epithelium as you move distally towards tail.
- Ductus deferens– travels from the perineum to the pelvis through the inguinal canal within the spermatic cord and ends in a dilated portion called the ampulla just prior to the ejaculatory duct at the prostate. Pseudostratified columnar epithelium similar to the epididymis (tall cells with stereocilia) but the lumen is not as smooth due to mucosal folds that are increased in the ampulla region. Thick muscular layer.
Accessory Sex Glands:
- Seminal vesicles– paired tubular glands found on the posterior wall of the bladder, lateral to the ampullas of the ductus deferens that produce fructose and other semen components. Combine with ampulla to form ejaculatory ducts which enter the prostate and empty into the prostatic urethra. Mucosa- pseudostratified columnar epithelium with tall non-ciliated cells and short round cells. Highly folded. Thin layer of surrounding smooth muscle and outer fibrous layer.
- Prostate gland– produces alkaline seminal fluid. Consists of 30-50 tubuloalveolar glands arranged within an inner mucosal layer, and intermediate submucosal layer, and a peripheral layer. Mucosal glands empty directly into prostatic urethra while submucosal and peripheral glands drain to prostatic sinuses on posterior wall of urethra. The fibromuscular stroma contains dense irregular CT and smooth muscle fibers. Alveoli of the glands are often filled with prostatic concretions (corpora amylacea) that may be partially calcified.
- Bulbourethral glands- pea-sized compound tubuloalveolar glands (similar structure to mucous glands) located on either side of the membranous urethra with ducts that drain into the spongy urethra. Produces pre-seminal (pre-ejaculate) fluid that lubricates and neutralizes any acidic urine in the spongy urethra.
Penis: consists of highly vascularized erectile tissues surrounded by connective tissue. Corpora cavernosa are the 2 dorsal masses of erectile tissue. The corpus spongiosum is ventrally located (penis is erect in anatomical position) and contains the spongy urethra. The main neurovasculature of the penis is dorsally located consisting of a central, deep dorsal vein, dorsal arteries on either side of the vein and dorsal nerves on the lateral sides of the arteries. The corpora cavernosa tissue each have a deep artery, running through the tissues int he central regions. The skin of the penis is loosely attached except for the distal glans penis where it is tightly attached. Sebaceous glands can be identified in the proximal penile skin. The glans penis is highly innervated by somatic and autonomic nerves.
Male Reproductive Specimen
In this specimen, practice identifying cells in different states of spermatogenesis. Start with the basement membrane of the seminiferous tubule and identify spermatogonia. Spermatogonia > primary spermatocytes > secondary spermatocytes > spermatids > spermatozoa. Also look for the supporting Sertoli cells (columnar cells with processes that reach out among the germ cells). Outside of the seminiferous tubules, you may see the myoid cells that surround the basement membrane and you should identify the testosterone-producing Leydig cells.
In the efferent ductules, look for the pseudostratified epithelium with microvilli and cilia. Look for the saw-toothed appearance of the lumen. Also look for the surrounding smooth muscle.
In this specimen slide, review stages of spermatogenesis in the seminiferous tubules of the testes. Spend some time comparing and contrasting parts of the excurrent duct system: efferent ductules, epididymis, and ductus deferens. All 3 structures have pseudostratified epithelium but you should be able to see stereocilia in the latter two. Notice the thick layer of smooth muscle surrounding the ductus deferens.
The spermatic cord consists of fascia, arteries (testicular a., cremasteric a., deferential a.), pampiniform plexus of veins, nerves (ilioinguinal and iliohypogastric nn.), cremaster muscle, and ductus deferens.
This is a specimen slide of a portion of the seminal vesicle. Take a close look at the pseudostratified columnar epithelium. Notice how all of the nuclei are located at the basement membrane so it appears as if the epithelium is simple columnar. It is difficult to pick out the shorter cells because there are more columnar cells than basal cells. Look for smooth muscle in the lamina propria and the 2 layers of smooth muscle in the muscularis layer. The outer layer is typical adventitia.
In this specimen of the prostate, examine the glandular tissue and fibromuscular stroma. Notice the epithelium of the glandular tissue varies. Look for prostatic concretions in some of the lumen of the glands. Notice the large neurovasculature supply found at the edge of the prostate. You can identify arteries, veins, and nerves.
In this specimen of the prostate, you can get a good look at the zones of the prostate. In the transitional zone, you can see the prostatic urethra where you should see transitional epithelium. This is the site of benign prostatic hyperplasia. In the central zone, you can see one of the two ejaculatory ducts (epithelium depends on species). In the peripheral zone, examine the glandular tissue of the prostate. This is a younger prostate so there is not much production of prostatic concretions at this point.
Take look at the glandular tissue of the bulbourethral gland. You can see alveoli surrounded by typical connective stromal tissue.
This is a cross-section of the penis. Identify the erectile tissue, urethra, and dorsal neurovasculature bundle.
More Practice
Use this specimen slide to determine which portion is the seminal vesicle and which portion is part of the prostate gland. Review the contents of each structure.
Identify the structure in this specimen slide.
Identify the structure in this specimen slide.
Identify the structure in this specimen slide.
Use this slide to review structures of the penis.
More Practice Answers
Slide 1. Cincinnati 3890
- A) black- seminal vesicle; B) blue- prostate
- Pseudostratified, non-ciliated
- Pseudostratified, non-ciliated (black arrows); and simple columnar (blue arrows)
Slide 2. New England College of Osteopathic Med
- ductus deferens- single tube with thick muscular layer
- Sperm
- Three layers of muscle, inner longitudinal, middle circular, outer longitudinal
Slide 3. New England 78
- Epididymis
- A) pseudostratified columnar with stereocilia (green arrows); B) spermatozoa/sperm
- Area of interest, no questions
Slide 4. New England
- testes
- A) black- spermatozoa; B) blue- primary spermatocyte; C) green- Sertoli cells; D) red- spermatogonia; E) early spermatid; F) yellow- myoid cells
- Leydig cells
Slide 5. U. of Mississippi Penis
- A) black- corpora cavernosa; B) green- corpora spongiosa
- A) blue- urethra; B) red- mucous gland
- yellow- nerves
- Vessels
- Skin- stratified squamous, keratinized
