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In the vas deferens, how many layers of smooth muscle are there?
- 3 layers: long/circulatory/long
- Involved in ejaculatory contraction
Describe the epithelium and lamina propri of the vas deferens.
- Epl: pseudostratified with basal cells and principal cells with stereocilia
- L. Propria: Core of lamina propria makes the epl folded
How is the smooth muscle of the vas deferens controlled?
- Contraction is initiated by sympathetic control
- Short lived response
- Powerful rhythmic contractions for active ejaculation of spermatazoa
Where does a vasectomy occur and what are the consequences of this procedure?
- Occurs at the ductus (vas) deference
- no hormonal disruption
- spermatazoa and ejaculate are still produced
- Principal epl cells of epididymis and ductus deferens become very phagocytic
- In a small minority, an immune response against spermatazoa is mounted in the wall
Describe the epl/muscle of the ejaculatory ducts.
- Epl: similar to epididymis- pseudostratifed with basal cells and principal cells
- Muscle: no smooth muscle in walls
How do spermatazoa travel through the ejaculatory ducts?
- Passive flow, driven by the contraction of the vas deferens
- passes through prostate, delivers spermatazoa and seminal fluid to the urethra
Name the accessory genital glands nd provide their secretory function.
- Seminal vesicles- secrete fructose-rich seminal fluid (majority of semen volume), provides energy for sperm motility
- Cowper's (bulbourethral) glands- secrete GAG/Sialic Acid-Rich fluid for lubrication
- Prostate- Secretes protease/fibrolytic enzyme which liquifies semen
Describe the structure of the prostate.
- Parenchyma (functional): exocrine, compound tubuloalveolar gland
- pseudostratified epl including columnar cells for differentiation/secretion and basal cells for proliferation/hyperplasia, both of which are testosterone-responsive
- Stroma (supportive): Dense irregular connective tissue + sympathetic-responsive smooth muscle
- intermingled smooth muscle for sympathetic controlled contraction
How is the prostate histologically stained?
Stained using a Prostate Specific Antigen-specific stain which appears brown under LM
Compare benign prostate hyperplasia and prostate carcinoma.
- Benign: increased epl proliferation, cells remain polarized, still testosterone dependent
- Carcinoma (malignant): increase epl proliferation, not polarized, no lumen (appears endocrine instead of exocrine), PSA is released into the stroma and fenestrated capillaries, testosterone-independent
What is the functional role of the urethra?
Common urine/semen passage
Describe the epithelial transitions in the urethra.
- Begins as transitional epl (expansion/contraction) in the prostatic urethra. Then it becomes pseudostratified columnar epithelium (some mucous secretion) in the membranous/bulbar urethra. Finally it becomes stratified squamous epl (protective, merges with skin externally) in the penile urethra.
- Since the transition is gradual, there is a lower likelihood of tumour development, and it is protective of infection.
Describe the structure of the penis.
- Three columns of erectile tissue = corpora (corpus spongiosum and 2 corpora cavernosum)
- Tissue of corpora is fibroelastic CT
- Each corpus is surrounded by a dense irregular CT capsule (tunica albuginea)
- Highly vascular- helicine arteries with prominent smooth muscle
- Corpora contain venous spaces/sinuses
Compare the flaccid and erect state of erectile tissue.
- Flaccid state-
- 1) helicine arterial smooth muscle contracted
- 2) little blood to venous sinuses in corpora
- 3) considerable blood shunted directly to non-corporal veins via arteriovenous anastomses (direct path from artery to vein without a capillary bed)
- Erect state-
- 1) Helicine arterial smooth muscle relaxed
- 2) Increased blood to venous sinuses which fill and expand
- 3) Decreased drainage to veins from venous sinuses due to pressure against the tunica albuginea (maintains erection)
Name the signals/messengers involved in facilitating erection.
- Parasympathetic NS- relaxes helicine smooth muscle
- Nitric oxide signalling- relaxes helicine smooth muscle
- NO generated 2nd messenger, cGMP - facilitates filling of venous sinuses
How does Viagra work?
Viagra is a phosphodiesterase inhibitor which prevents the breakdown of cGMP to maintain filling of the venous sinuses