Lecture 40 Flashcards
Rete testis
Simple cuboidal epithelium. All testicular fluid (including spermatozoa) travel through ep. The fluid also has androgen binding protein bound to testosterone.
Fluid resorption in male tract
Hormonal regulation is maintained
throughout duct system of male reproductive system by the fact that fluid will be slowly resorbed from the duct system at all levels
from the testis all the way to vas deferens by a mechanism that involves transport of sodium chloride.
- i.e. gall bladder concentrates bile by removing water, which is facilitated by
transport of sodium chloride so water will passively follow to equilibriate osmolarity differences
Ep involved in this is located mostly in efferent ductules and epididymis
Efferent ductule
Have ciliated cells that provide motion of testicular fluid towards epididymis and consequently spermatozoa will be transported through ciliary action
Pseudostratified columnar epithelium
- saw-tooth appearance on lumen
Lumen had spermatozoa
- Basal cells at basement membrane, these are stem cells
- Ciliated cells have a line of basal bodies, which move content of tubule towards epididymis
- Principal cells are columnar and have stereocilia for resorption of fluid
Epididymis and vas deferens
Epididimys and vas deferens start getting surrounded by smooth muscle. So, contractility of these 2 regions will facilitate sperm transport
Sperm transport to rete testis
Where seminiferous tubules open up into rete testis, there is a part of the tubule that is straight called TUBULUS RECTUS. The seminiferous tubule is highly coiled, then it straightens up for short distance to hook up to rete testis.
At border bw seminiferous tubule and tubulus rectus (straight), spermatogenesis stops. The thing that remains is sertoli
cells in tubulus rectus.
Height of ep also decreases, so we transition from tubulus rectus (columnar) to cuboidal ep rete testis.
In seminiferous tubules, the blood-testis barriers which are towards the base of seminiferous tubules. This junction moves towards apical end as it goes from seminiferous tubules to tubulus rectus to rete testis
Epididymis - spermatozoa and appearance
Main storage site for spermatozoa bw ejaculations. Divided into head, body and tail regions.
If you take spermatozoa out of head of epididymis and put cells in petri dish, they do not move, so they do not have acquired motility yet
But if you take spermatozoa from tail of epididmyis, they are motile
So within epididymis, spermatozoa acquired motility
If you take motile spermatozoa from tail of epididymis and try to fertilize it with an egg, it will not be able to penetrate the egg
Appearance:
- apical surface is straight
- pseudostratified columnar epithelium with stereocilia
- Basal (stem) cells
- Principal cells with stereocilia for resorption of fluid
Along the length of epididymis, there is increase in smooth muscle cells surrounding the tubule. Smooth muscle contraction will transport spermatozoa to vas deferens
Vas deferens and surrounding
Pseudostratified Columnar Epithelium with Stereocilia
Smooth Muscle Coat on outside (responsible for transporting spermatozoa out of male reproductive tract)
- inner layer: longitudinal
- middle layer: circular
- outer layer: longitudinal
At low mag, next to vas deferens is pampiniform veins, which has lots of smooth muscle and a wider lumen. These are large veins with lots of smooth muscle in adventitia, purpose is to remove a lot of blood out of male reproductive system. So we have lots of blood supply that is
circulating through the SPERMATIC CORD (vas deferens + pampiniform vein)
Ep of vas deferens is basophilic. Pampiniform vein has thin endothelium
Bulbourethral gland
Gives mucus fluid that is activated during sexual arousal. So the penis will be lubricated by the bulbourethral gland.
Components of semen
- 200-300 million spermatozoa from seminiferous tubules
- Secretions from testicular ducts (seminiferous tubules gives reduced secretions)
- Secretions from Seminal Vesicles (Fructose, Prostaglandins) (gives energy for spermatozoa, mostly sugars)
- Secretions from the Prostate Gland (Hydrolytic Enzymes, PSA = prostate specific antigens)
- purpose of seminal fluid is for spermatozoa to be injected into female reproductive tract so they are packaged together in a semi fluid viscous medium
- but as soon as they enter female tract, all the packaging needs to be unwrapped
- so the hydrolytic enzymes get activated and semen becomes liquid (transition from viscous to liquid), allowing spermatozoa to migrate inward in the female tract.
• Mucus from Bulbourethral Glands
• Cellular debris
- bc not all spermatozoa survive
Seminal vesicle
- Pseudostratified Columnar Epithelium (columnar cells and basal stem cells)
- whitish viscous secretion
- fructose
- prostaglandins
Ep are secretory cells that have secretory vesicles to make fructose and prostalglandins
Spaces that are lined by a folded mucosa. The sacculations are convoluted and surrounded by fibromuscular CT.
There is 1 pair of seminal vesicles opening up to urethra, that is surrounded by prostate gland too
Prostate gland
Has homogenous deposits called prostatic concretions. They are sporadically found. With age, the number of concretions
increases. Have no clinical significance in terms of prostate gland function or prostate cancer.
Pseudostratified Epithelium. Ep has terminal web, so there are microvilli
Fibromuscular ströma: Ep cells are surrounded by cells that are contractile
3 zones:
1. Central zone - adjacent to urethra, has glands that have short ducts and not highly branched
- Transitional zone - larger glands
- Peripheral zone - large glands and are branched
All zones deliver secretion into urethra
BPH
With age, there is tendency of cells in central zone of prostate gland to proliferate by hyperplasia (increase in cell number), which is usually benign; called benign prostatic hyperplasia or BPH.
Often, BPH increases with age. Males affected have hard time urinating. This could be indication for BPH or prostate cancer. To
distinguish, measure PSA = prostate specific antigens. Prostate cancer has higher PSA
levels.
Prostate cancer also usually comes from peripheral zone or transitional zone
Digital prostate exam
Men do this when they are older
Finger goes into rectum and the doctor palpates outer surface of prostate gland to detect if there are any changes in that, indicating possible cancer. Then biopsy follows
Pathway of spermatozoa with features and functions of each structure
- Tubulus rectus
- Simple columnar epithelium (only Sertoli cells)
- Non-motile spermatozoa without fertilizing capacity - Rete testis
- Simple cuboidal epithelium
- Conduit of spermatozoa - Efferent ductules
- Pseudostratified columnar epithelium with ciliated cells
- Absorption of fluid from tubule, conduit of spermatozoa - Epididymis
- Pseudostratified columnar epithelium with stereocilia
- Absorption of fluid, storage of sperm, sperm acquire motility and fertilizing capacity - Vas deferens
- Pseudostratified columnar epithelium with stereocilia, 3 smooth muscle layers
- Contraction of smooth muscle propels sperm during ejaculation - Seminal vesicle
- Columnar to cuboidal pseudostratified or simple epithelium, folded mucosa
- Viscous secretion contains fructose, amino acids and prostaglandins - Prostate gland
- Similar to seminal vesicle, 30-50 glands, prostatic concretions
- Secretion contains acid phosphatase, fibrinolysin, citric acid - Bulbourethral gland
- Tubulo-alveolar glands
- Secretion provides lubricant upon sexual arousal
Penis
Urethra is surrounded by corpus spongiosum
Corpus cavernosum is separated by DCT tunica albuginea. Corpora cavernosa is plural. Erectile tissue that contains lots of blood. There will be hydrostatic pressure. Corpora cavernosa have one large central artery that connects to dorsal arteries that deliver blood into erectile tissue
Dorsal arteries and veins bring blood into erectile tissue and drain out
Molecular mechanisms regulating penile erection
Step 1: Sinusoids in erectile tissue
- Nerves produce nitric oxide (NO) which enters into smooth muscle cells surrounding the sinusoids. NO is passed on through gap junctions bw smooth muscle cells.
Step 2: Smooth muscle cell
- NO molecules activate guanylate cyclase converting GTP into cGMP
Step 3: Smooth muscle cell
- cGMP sequesters cytoplasmic Calcium from smooth muscle cells into calcium stores, triggering relaxation of myosin and actin.
- If calcium is gone, smooth muscle relaxes.
- Calcium is needed for muscle contraction
- Phosphodiesterase breaks down cGMP. If there is no sexual arousal, cGMP levels go down and calcium goes back to smooth muscle. Smooth muscle contracts and blood is sent out of erectile tissue, the penis becomes flaccid.
Step 4: Sinusoids in erectile tissue
- As smooth muscle cells relax, blood can enter the sinusoids or blood spaces and fill up the erectile tissue
- Blood flows into relaxed sinusoids which compress small veins preventing drainage
- As blood increases in sinusoids, it compresses veins that normally drain the blood. So this maintains the blood pressure in the erectile tissue
