Male Reproductive Histology (Dennis) Flashcards
What are the main functions of the male reproductive system?
- production, nourishment, and temporary storage of sperm
- synthesis/secretion of male sex hormones (androgens)
Where does sperm and androgen production occur?
testes
What structures transport sperm?
- epididymis
- ductus deferens
- ejaculatory duct
- urethra
What structures help produce semen?
- seminal vesicles
- prostate gland
- bulbourethral gland
What are the structures a/w the testes?
- testes: paired organs located in the scrotum, posteriorly a/w the epididymis
- tunica albuginea (TA): dense CT capsule
- TA forms the mediastinum testis (posterior), network of fibrous CT that extends from top to near bottom of each testis
- septa create lobules in which seminiferous tubules are housed
- tunica vaginalis: derived from peritoneum, has an outer parietal layer lining the scrotum and an inner visceral layer covering the tunica albuginea
What structures are a/w the seminiferous tubules?
- septa create 250-300 lobules containing 1-4 convoluted seminiferous tubules lined w/ seminiferous epithelium composed of:
1. sustentacular (Sertoli) cells
2. spermatogenic cells - tubules surrounded by CT and 3-5 layers of flattened, peritubular myoid cells (create peristaltic contractions that help move spermatozoa)
- interstitial cells of Leydig found in between seminiferous tubules
Identify the structures in the following images:
- IC: interstitial cells
- SC: Sertoli cells
- M: peritubular myoid cells
- F: fibroblasts
- SG: spermatogonia
- PS: primary spermatocytes
- ES: early spermatids
- LS: late spermatids
- steroid-producing cells (testosterone) containing lipid droplets, mito, and well-developed sER
- present in between tubules, close to blood vessels and lymphatic channels
- accompanied by myoid cells and fibroblasts
interstitial cells (of Leydig)
Identify the structures in the following images:
- BV: blood vessel
- L: lobule
- LC: leydig cells
- LP: lamina propria
- S: CT septa
- Sc: spermatocytes
- Sg: spermatogonia
- Sn: Sertoli nucleus
- Sp: spermatids
- TA: tunica albuginea
- X: tangential section of tubule w/ lumen obscured
- arrows: spermatid nuclei displaying early shape change
What are the structures/cells a/w seminiferous epithelium?
- SE: stratified epithelium w/ unusual characteristics
- sustentacular (Sertoli) cells: columnar cells w/ extensive processes that surround spermatogenic cells and occupy spaces between them; organize tubules and extend through the full thickness of epithelium; hallmark is cyclops nucleus
- spermatogenic cells: replicate and differentiate into mature sperm; spermatogonia (most immature) rest on basal lamina; spermatids (most mature) are attached to apical portion of Sertoli cell near tubule lumen
- “nurse” cells w/ crypts supporting 30-50 germ cells
- function in: exchange/transport of metabolites and nutritive factors into lumen; exocrine/endocrine secretion; phagocytose residual bodies (spermiogenesis) and effete spermatogenic cells
- bound by tight junctions to form Sertoli cell-to-Sertoli cell junctional complex: creates 50+ parallel lines of fusion along basolateral membranes, establishes blood-testis-barrier
Sertoli cells
What are the different types of spermatogenic cells?
- spermatogonia: clonoally divide (mitosis), located near basement membrane; type A spermatogonia (generates copies of itself and/or differentiates into type B); type B spermatogonia (enter meiotic prophase as primary spermatocytes)
- spermatocytes: two meiotic divisions and inside blood-testes barrier; primary spermatocytes > secondary spermatocytes > spermatids
How is a blood-testis barrier established?
- Sertoli-Sertoli junctional complex divides epithelium into basal and luminal compartments
- complexes establish blood-testis barrier: isolates haploid germ cells (secondary spermatocytes, spermatids, and sperm) from systemic circulation
How do pre-sperm cells move through the seminiferous compartments?
- spermatogonia and early primary spermatocytes are restricted to basal compartment
- primary spermatocytes pass through junctional complex, move from basal > luminal compartment
- mature spermatocytes and spermatids are restricted to luminal compartment
How do spermatids mature and where are they housed during their stages?
- spermatids undrego spermiogenesis and differentiate into mature sperm cells
- round (early) sperm: housed in niches of Sertoli cells
- elongated (late) spermatids: housed in apical crypts of Sertoli cells
- the release of mature spermatids into lumen
- spermatids lose intercellular bridges and mature spermatids are separated
- spermatozoa are fully formed, but not yet functional
- sperm are propelled into epididymal duct
spermiation
What is the general structure of sperm?
- comprised of head, neck, and tail
- head: contains flattened, elongated nucleus; partially capped by acrosome; contains hydrolytic enzymes
- tail: subdivided into middle piece containing mitochondria, principal piece which is the longest segment, and end piece
What is the pathway for sperm transport>
straight tubules
>
rete testis
>
efferent ductules
>
epididymis
>
ductus deferens
>
ejaculatory duct
What structures are a/w the epididymis?
- epididymis: highly elongated and coiled duct (about 6 m) where sperm mature, has a head, body, and tail
- composed of psuedostratified columnar epithelium w/ long stereocilia: 1) principal cells: columnar cells extending from lumen to basal lamina w/ stereocilia, 2) stem cells of principal cells
- has a thin circular layer of smooth muscle cells; in tail region there is an addition of inner and outer longitudinal layers
- sperm maturation consists in acquiring forward motility, mature sperm are stored in tail
Identify the structures in the following image:
- AT: adipose tissue
- BV: blood vessel
- C: cilia
- CT: connective tissue
- P: pigment
- SC: stereocilia
- SM: smooth muscle
- arrows: islands of epithelium in the lumen
What structures are a/w ductus deferens?
- ductus deferens: 45 cm muscular tube lined w/ pseudostratified columnar epithelia w/ sparse stereocilia, supported by a CT lamina propria w/ elastic fibers
- muscular wall: inner and outer longitudinal layers, and middle circle layer
- external layer consists of loose CT and adipocytes
- ampulla: dilated portion that leads directly into prostate gland
- distal ends receive ducts of seminal vesicle, forming ejaculatory ducts
Identify the structures in the following images:
What are the accessory glands of the male reproductive system?
- seminal vesicles (2), prostate gland (1), bulbourethral glands (2), urethral glands
- seminal vesicles and prostate gland prod majority of seminal fluid, function is regulated by androgens (testosterone and DHT)
- all glands empty into the prostatic urethra > end site of prostatic ducts (prostatic secretions) and ejaculatory ducts (semen and secretions from seminal vesicles)
What is the function and histological structure of seminal vesicles?
- function: prod alkaline secretion rich in fructose and prostaglandins, contributes to semen (~70%), excretory duct penetrates the prostate after joining ductus deferens > from ejaculatory duct
- histology: external CT capsule, highly folded mucosa lined by pseudostratified columnar epithelium, inner circular and outer longitudinal smooth muscle
Identify the structures in the following image and where in the body this sample was obtained:
seminal vesicles
What are the zones of the prostate gland?
(prostate: collection of 30-50 tubuloacinar glands embedded in dense fibromuscular stroma, CT capsule)
- central zone: surrounds ejaculatory ducts as they pierce prostate gland (~25% of glandular tissue)
- peripheral zone: surrounds central zone and posteriolateral parts of the gland (70% of glandular tissue), most prostatic carcinomas arise here, palpable during digital rectal exam
- transitional zone: surrounds prostatic urethra (5% of glandular tissue, contains mucosal glands), parenchymal cells undergo hyperplasia and form nodular masses of epithelial cells, can compress the prostatic urethra causing difficult urination (benign prostatic hyperplasia (BPH))
- periurethral zone: contains mucosal and submucosal glands, in later stages of BPH this zone may undergo pathologic growth but mainly from stromal compartments
- all glands empty into the prostatic urethra > end site of prostatic ducts (prostatic secretions) and ejaculatory ducts (semen and secretions from seminal vesicles)
Identify the structures in the following images:
- BV: blood vessel
- C: prostatic concretion
- Cap: capsule
- Ep: epithelium
- L: lymphocytes
- SM: smooth muscle
- arrows: inactive alveoli
- arrowheads upper figure: epithelial islands
- arrowheads lower figure insert: basal cells
Identify the structures in the following images:
- pea-sized structures located in the urogenital diaphragm
- compound tubuloalveolar glands, resemble mucous glands
- lined w/ simple columnar epithelium under the control of testosterone
- secrete preseminal fluid > lubricate penile urethra, neutralizes traces of acidic urine
bulbourethral glands
Describe the structure of the penis:
- consists of cylindrical, columnar masses of erectile tissue: R/L is corpora cavernosa (2), and ventral is corpus spongiosum (1) which contains penile urethra
- all 3 erectile tissues are comprised of irregular, interconnected vascular sinuses w/ fibrocollagenous stroma
- glans penis is the distal tip of the corpus spongiosum
- corpora cavernosa are each surrounded by a dense fibroelastic layer, the tunica albuginea
How is an erection produced?
-
erection involves blood filling the cavernous spaces of erectile tissues, controlled by ANS in the vascular walls:
1) parasympathetics relax trabecular smooth muscle and dilate helicine arteries > increases blood flow and filling of cavernous spaces
2) enlargement compresses dorsal veins against tunica albuginea > blocks venous outflow and produces rigidity in erectile tissues
3) at ejaculation, sympathetics constrict helicine arteries and trabecular muscle > decreases blood flow into spaces, allowing veins to drain most of the blood
