Histology of Male Reproductive System Flashcards
What does the male reproductive system consist of?
Testes
System of genital ducts
Accessory genital glands
Peis
What do the seminiferous tubules of the testes produce and secrete?
Spermatozoa
What do the testes contain?
Contain endocrine cells, the interstitial cells (of Leydig) that secrete the male hormone, testosterone
What are the structures within the testes?
Tunica albuginea
Tunica vasculosa
Lobuli testis
Seminiferous tubules
What are the characteristics of the tunica albuginea?
CT capsule that encloses each testis
Composed of dense irregular collagenous CT
Mediastinum testis
What is the mediastinum testis?
Part of the tunica albuginea
Thickened portion of the tunica albuginea where the epididymis attaches
Site where blood vessels, lymphatics vessels, nerves and genital ducts come in or not
Gives rise to incomplete CT septa that radiate into testis - septa subdivide testis into about 250 lobuli testis (lobules)
What are the characteristics of the tunica vasculosa?
Layer of loose CT deep to the tunica albuginea
Has a rich vascular supply and is the vascular capsule around the testis
What are the characteristics of the Lobuli testis?
Each lobules contains:
1-4 coiled seminiferous tubules
Interstitial cells of Leydig
Loose CT stroma - highly vascularized, fills the spaces between seminiferous tissues in the lobuli testes and is also where interstitial cells of Leydig are located
What are the components of the Seminiferous Tubules?
Tunica (lamina) Propria
Basal Lamina
Seminiferous Epithelium (germinal epithelium)
Sertoli cells
Compartments of seminiferous epithelium
Spermatogenic cells
What are the characteristics of the tunica (lamina) propria of the seminiferous tubules?
Thin CT layer that contains collagen and 3-5 layers of myoid cells (contractile) that produce rhythmic contractions to move spermatozoa through the tubules
What are the characteristics of the seminiferous epithelium or germinal epithelium?
Stratified epithelium that lines interior of seminiferous tubules
Contains spermatogenic cells (gametes) and Sertoli cells (support)
How do the spermatogenic cells differentiate and then become sperm?
Undergo progressive differentiation as they move from periphery of the seminiferous tubules to the hollow lumen, where they are released
Spermatozoa pass through genital ducts to reach exterior
As sperm pass through the ducts, the accessory glands (seminal vesicles, prostate, and bulbourethral glands) release secretory products into genital duct lumen to form semen (fluid + sperm)
What are the Sertoli cells and their function?
Tall, columnar, non-replicating cells
Highly folded
Clear, ovoid or triangular nucleus and prominent nucleolus
Sertoli cell to Sertoli cell junctional complex binds the lateral cell membranes of adjacent Sertoli cells together to compartmentalize seminiferour epithelium into 2 compartments
What is the seminiferous epithelium compartments?
Luminal compartment - adluminal
Basal epithelial compartment
What do the occludens junctions of the Sertoli cells create?
Blood-testis barrier
Sertoli cells provide physical support and also physiological support for spermatogenic cells
BTB isolates the haploid secondary spermatocytes, spermatids, and spermatozoa from immune system in adult
BTB has gap junctions
Release androgen-binding protein (ABP), hormones, and nutrients
Testosterone binds to ABP in seminiferous tubules which promotes spermatogenesis
What is in the luminal compartment of the seminiferous epithelium?
Spermatozoa
Spermatids
Secondary spermatocytes
Primary spermatocytes
What is in the basal epithelial compartment of the seminiferous epithelium?
Basal to the zonulae occludentes (ZO) formed by Sertoli cells
ZO forms the BTB which segregates the luminal from the CT - it shields the forming gametes from the immune system
Contains spermatogonia and early primary spermatocytes
What are the spermatogenic cells?
Spermatids (most mature)
Secondary spermatocytes
Primary spermatocytes
Spermatogonia (least mature)
Umbilical vesicle (yolk sac) gives rise to primordial germ cells which in turn differentiate into spermatogonia
What is spermatogenesis?
Maturation process of spermatogenic cells
It begins in response to pituitary gonadotropin release shortly before puberty
Takes about 74 days for spermatogonium to transition through process of spermatogenesis
Takes approximately an additional 12 days for a sperm to pass through epididymis
3 phases - spermatogonial, meiosis, spermiogenesis
What happens during the spermatogonial phase of spermatogenesis?
Occurs in basal compartment
Process by which spermatogonia differentiate into primary spermatocytes
Spermatogonia rest directly on basal lamina and have 46 single chromatid chromosomes (2n, 2d)
3 types of spermatogonia
What are the 3 types of spermatogonia?
Type A dark spermatogonia
Type A pale spermatogonia
Type B spermatogonia - these undergo mitosis to form primary spermatocytes (2n, 2d)
What occurs during the spermatocyte phase (Meiosis)?
Occurs in luminal compartment
Process by which primary spermatocytes differentiate into spermatids
Primary spermatocytes (2n, 4d) are largest cells of the seminiferous epithelium
Primary spermatocytes enter Meiosis I to form secondary spermatocytes that have 23 double chromatid chromosomes (1n, 2d)
Secondary spermatocytes are rarely observed because they enter Meiosis II immediately to form spermatids that have 23 single chromatid chromosomes (1n, 1d)
What occurs during the spermatid phase (spermiogenesis)?
Occurs in luminal compartment
Process by which spermatids are transformed into spermatozoa (sperm)
Spermatids are very small cells with round, dense nuclei, and occurs in groups next to lumen
Spermatids are non-motile and transform into motile spermatozoa (1n, 1d)
What are the interstitial cells of Leydig?
Located in the lobuli testis, in the loose CT stroma that fills the spaces between adjacent seminiferous tubules
Endocrine cells - stimulated by gonadotropins (FSH, LH) to synthesize and secrete testosterone
What are the genital ducts?
These are the pathway of sperm (and semen) through the genital system
Spermatozoa are formed in the seminiferous epithelium lining the seminiferous tubules and then pass through genital ducts
What are the genital ducts in order?
Tubuli recti
Rete testis
Efferent ductules
Duct of the epididymis
Ductus deferens
Ejaculatory duct
Urethra
What are the intratesticular genital ducts?
Tubuli recti - lined by Sertoli cells and lined by simple cuboidal epithelium in the distal end
Rete testes - Labrinthine spaces, lined by simple cuboidal epithelium or low columnar epithelium
What are the extratesticular genital ducts?
Epididymis
Ductus deferens (vas deferens)
Ejaculatory duct
What is the epididymis?
This is where sperm acquire their motility
Motility likely due to changes in intracellular levels of cAMP, Ca 2+, and pH
Has efferent ductules
Duct of epididymis
What are the histological characteristics of the efferent ductules of the epididymis?
Pseudostratified columnar epithelium with cilia
Basal lamina
Thin loose CT
Smooth muscle cells - circularly arranged
Apical cell membrane invaginations resorb fluid (released by Sertoli cells) from lumen by endocytosis
Cilia sweep the sperm towards the ducts of epididymis
What are the characteristics of the duct of epididymus?
Regions - head, body, tail
Pseudostratified columnar epithelium with stereocilia
Basal lamina
Loose connective tissue
Smooth muscle layer - peristaltic contractions
What are the characteristics of the ductus deferens?
Pseudostratified columnar epithelium with sterocilia
Basal lamina
Loose fibroelastic CT - folded
Smooth muscle coat: inner layer = longitudinal, middle layer = circular, outer layer = longitudinal
Ampulla - dilated end of the ductus deferens, joins the seminal vesicles to form the ejaculatory duct
What are the characteristics of the ejaculatory duct?
Simple columnar epithelium
Basal lamina
Subepithelial CT
No smooth muscle
What are the accessory genital glands?
Seminal vesicles
Prostate gland
Bulbourethral glands
What are the characteristics of the seminal vesicles?
Epithelium is pseudostratified columnar epithelium with short round basal cells and tall non-ciliated columnar cells
Subepithelial CT is fibroelastic
Smooth muscle coat
Thin fibrous coat covers smooth muscle coat
Controlled by testosterone
Function is secretion of viscous, yellow, fructose-rich seminal fluid with amino acids, ascorbic acid, prostaglandins, and proteins
What are the characteristics of the prostate gland?
Largest accessory gland, chestnut-shaped
Capsule is dense irregular collagenous CT (highly vascular) and smooth muscle cells
CT stroma arises from the capsule and is the same as the capsule
Tubuloalveolar glands
What are the layers of the tubuloalveolar glands?
Mucosal layer - inner layer, has small glands
Submucosal layer - intermediate layer, has larger glands
Peripheral layer - has the main prostatic glands, the largest glands
Simple to pseudostratified columnar epithelium - synthesizes proteins
Prostatic concretions - corpora amylacea, calcified glycoproteins
What is benign prostatic hyperplasia?
Non-harmful enlargement of the prostate becomes more common with age
What is adenocarcinoma of the prostate?
Prostate cancer
What are the characteristics of the bulbourethral glands (Cowper’s glands)?
Located at proximal end of the membranous urethra
Capsule is fibroelastic CT, which gives rise to septa which divides the gland into lobules
Compound tubuloalveolar glands are simple cuboidal to simple columnar epithelium
Secretes thick, slippery fluid to lubricate lumen of urethra
What are the characteristics of the erectile tissue?
3 columns, each covered by a dense, fibrous, CT capsule - the tunica albuginea
2 corpora cavernosa - dorsally
1 corpus spongiosum - ventrally
What are the layers of the urethra?
Transitional epithelium
Lamina propria - loose fibroelastic tissue, very vascular, contains glands of Littre
Muscularis - layer of smooth muscle outside the mucosa. upper 2/3rds of the urethra has two layers of smooth muscle (inner longitudinal and outer circular). Lower third has three layers of smooth muscle: inner longitudinal, middle circular, outer longitudinal
Adventitia
What are the characteristics of the prostatic urethra?
3-4 cm long, lies in the prostate gland
Lined by transitional epithelium
What are the characteristics of the membranous urethra?
1-2 cm long
Passes through the perineal membrane
Lined by stratified columnar epithelium
Interspersed with patches of pseudostratified columnar epithelium
What are the characteristics of the spongy urethra?
Passes through the length of the penis and corpus spongiosum
Stratified columnar epithelium
Interspersed with patches of pseudostratified columnar and stratified squamous, nonkeratinized epithelium
Glans is stratified squamous epithelium
What are the two mucus glands of urethra?
Glands of Littre - urethral glands
Bulbourethral Glands (of Cowper)
Lubricate the urethral lumen
Glands are located along the length of the penile urethra
