Male Reproductive Histology - BGDA Flashcards
What are the 4 main components of the male reproductive system?
1 - testes/testicles
2 - genital ducts - intra and extra testicular
3 - accessory glands (prostate, seminal vesicle, bulbourethral glands)
4 - penis
What are the intra and extra testicular ducts?
Intra - straight tubules, rete testis and efferent ductules
Extra - epididymis, ductus deferens, ejaculatory duct
What is the mediastinum testis?
Thickened tunica albuginea on the posterior side of testis
What is the role of interstitial tissue?
Located between the seminiferous tubules
- connective tissue structure that contains interstitial (leydig cells)
What do interstitial leydig cells produce?
These are large round/polygonal cells with eosinophilic cytoplasm rich in small lipid droplets
- produce testosterone which stimulate the development of the secondary male sex characteristics
How many seminiferous tubules does each testis contain?
250-1000 approx
What are the features of seminiferous tubules?
Measures 150-250 um in diameter and 30-70cm in length
- a loop connected to the rete testis via straight tubule
What is the rete testis?
A network of epithelium-lined channels located within mediastinum testis
- opens into epididymis through 10-20 efferent ductules
What is spermatogenesis?
A process that begins at puberty with the proliferation of spermatogenic progenitor cells called spermatogonia
What are spermatogonia?
Small round cells occupying a basal niche in the epithelial wall of the tubules
- lie next to the basement membrane
Outline key features of Type A spermatogonia (stem cells)
- spermatogonia with dark, ovoid nuclei
- act as stem cells
- divide frequently and give rise both to new stem cells and cells with more pale-staining, ovoid nuclei that divide more rapidly as transit amplifying (progenitor) cells
Outline key features of Type A spermatogonia (progenitor cells)
These cells undergo several unique clonal divisions
- leave most of the cells interconnected as a syncytium
Outline Type B spermatogonia
These cells are more spherical and pale nuclei
- undergo final mitotic division to produce two cells that grow in size and become primary spermatocytes
What are the largest cells of the spermatogenic lineage?
Primary spermatocytes
What are key features of primary spermatocytes?
Spherical cells with euchromatic nuclei
- presence of partially condensed chromosomes in various stages of synapsis and recombination
What is the result of the division of each primary spermatocyte?
Production of two secondary spermatocytes
Why are secondary spermatocytes rare in testis sections?
They are very short-lived cells that remain in interphase only briefly and quickly undergo the second meiotic division
What does the division of each secondary spermatocyte produce?
Two haploid cells called spermatids each of which contains 23 chromosomes
What are spermatids?
Haploid cells with 23 chromosomes
What is spermiogenesis?
The final stage of spermatogenesis when spermatids differentiate to become spermatozoa
Which changes occur during spermiogenesis?
1) Formation of acrosome
2) Condensation and elongation of the nucleus
3) Development of the flagellum (formation of neck, middle piece and tail)
4) Shedding of most of the cytoplasm as residual bodies
What are the two ends of sertoli cells?
Basal end: adhere to the basal lamina
Apical end: extend to the lumen
How are sertoli cells structured?
Ovoid or triangular, euchromatic nuclei, and have a prominent nucleus
What do sertoli cells do?
1) Nourish the spermatogenic cells
- all cells of spermatogenic lineage are closely associated with the extended surfaces of Sertoli cells and depend on them for metabolic and physical support (each sertoli cell supports 30-50 developing germ cells)
2) Exocrine and endocrine secretion
- Androgen-binding protein (ABP) concentrates testosterone to a level required for spermiogenesis
- inhibin
3) Phagocytosis
What is the blood-testis barrier?
A tight barrier formed by elaborate tight occluding junctions between their basolateral membranes within the seminiferous epithelium
What are the two compartments of the blood-testis barrier?
1) Basal compartment containing spermatozoa
2) Adluminal compartment containing primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa
What is the main function of the intratesticular ducts (straight tubules, rete testis, efferent ductules)?
Carry spermatozoa and liquid from the seminiferous tubules to the duct of the epididymis
What is the histology of straight tubules?
Simply lined with sertoli cells
What is the histology of rete testis?
- Epithelium containing cuboidal cells
- supporting tissue containing connective tissue of the mediastinum
What is the histology of efferent ductules?
- Epithelium composed of nonciliated cuboidal cells (absorb some of the fluid secreted by the sertoli cells) + ciliated cells (create a fluid flow which carries sperm passively out of the testis toward the epididymis)
- supporting tissue - a thin layer of circularly oriented smooth muscle cells which aid the movement of sperm into the duct of the epididymis
Where is the epididymis located?
In the scrotum along the superior and posterior sides of the testis
How is the epithelium of the epididymis structured?
Pseudostratified columnar epithelium consisting of columnar principal cells and small round stem cells
Outline the smooth muscle layer of the epididymis
Circular layer located in the tall region as an addition to inner and outer longitudinal layers
How does spermatozoa change when it passes through the epididymis?
- Acquires motility
- maturation of the acrosome
- reorganisation of the cell membrane surrounding the head
Define ductus deferens
The ductus deferens is a long straight tube that joins with the duct of the seminal vesicle to form the ejaculatory duct which opens into the prostatic urethra.
What are the histological features of ductus deferens?
1) Mucosa; folded longitudinally
- epithelium is psuedostratified columnar
- lamina propria containing many elastic fibres
2) Muscular wall
- longitudinal inner, middle circular and longitudinal outer layers
3) Adventitia
What are key features of the seminal vesicles?
- Paired highly torturous tubes covered by connective tissue
- located posterior to the urinary bladder
What is the function of seminal vesicles?
Secrete 70% of the seminal fluid including fructose, prostaglandins and fibrinogen.
Outline histological features of the seminal vesicles.
1) Mucosa: containing a lot of folds composed of;
- epithelium: simple or pseudostratified columnar epithelial cells rich in secretory granules
- lamina propria; thin layer containing elastic fibres
2) Muscular layer composed of smooth muscle;
- inner circular layer
- outer longitudinal layer
3) Adventitia
What are the three major zones of the prostate gland?
1) Transition zone:
- 5% of prostate volume
- surrounds the superior portion of the urethra
- contain periurethral mucosal glands
2) Central zone
- 25% prostate volume
- contain periurethral submucosal glands
3) Peripheral zone;
- 70% of prostate volume
- contains main glands of the prostate
What are the functions of the prostate gland?
Production of a fluid that contains exosomes, various glycoproteins, enzymes and small molecules such as prostaglandins
- One clinically important product of the prostate is prostate-specific antigen (PSA) which helps liquefy coagulated semen for the slow release of sperm after ejaculation
Outline the histology of the prostate gland.
- Consists of 30-50 tuboacinar glands embedded in a dense fibromuscular stroma in which smooth muscle contracts at ejaculation
- tuboacinar glands lined with simple or pseudostratified columnar epithelium
- presence of small spherical concretions called corpora amylacea in the lumens of many prostatic tuboacinar glands (these are partially calcified and contain primary deposited glycoproteins and keratin sulfate)
What are bulbourethral/cowper’s glands?
Paired round glands located in the urogenital diaphragm - empty into the proximal part of the penile urethra
Outline the histology of bulbourethral glands
Composed of several lobules with tuboacinar secretory units:
- epithelium: mucus-secreting simple columnar epithelium that is also testosterone dependent
- supporting tissue: smooth muscle cells
What do the bulbourethral glands do?
Lubricate the urethra for the passage of seminal fluid
What are the three masses of erectile tissue on the penis?
Two dorsal corpora cavernosa and a ventral corpus spongiosum
What is the histology of the two dorsal corpora cavernosa?
Each of them surrounded by tunica albuginea
What is the histology of the ventral corpus spongiosum?
- Surrounds the penile urethra
- at the end, expands and forms the glans of penis –> covered by the prepuce or foreskin
What is the histology of the penile urethra?
Most of the penile urethra is lined with pseudostratified columnar epithelium which become stratified squamous epithelium in glans
What is the histology of erectile tissues in the penis?
Consist of venous cavernous spaces;
- lined with endothelium
- separated by trabeculae with smooth muscle and connective tissue continuous with the surrounding tunica albuginea
