Physiology-Male Reproductive System Flashcards
Identify the different structures labeled below:
1) Tunica albuginea (connective tissue capsule) 2) Septae (invaginations of tunica albigunia separating lobules) 3) Seminiferous tubules 4) Visceral layer of tunica vaginalis 5) Parietal layer of tunica vaginalis 6) Mediastinum testes (where all vessels come in and go out)
Identify the different structures labeled below
*
What is the exocrine secretory product of the testes?
Spermatozoa from the seminiferous tubules
What is the endocrine secretory product of the testes?
Testosterone from the Leydig cells in the testicular interstitium
What composes the majority of the space in the testis?
Seminiferous tubules
What are the spiral hairs in the center of the seminiferous tubules?
Flagellae of the developing spermatids, their heads are still in the seminiferous tubules.
What cells are indicated in this slice from a testicle?
Yellow = tunica propria (CT covering each seminiferous tubule). Blue = fibroblasts, rarely peritubular contractile cells.
What cells are responsible for forming the three dimensional network on top of the lamina propria in the seminiferous tubules?
Sertoli cells. They are tall, columnar cells that cover the thickness of the wall (lamina propria to the lumen)
Why are Sertoli cells also called nursing cells?
Developing spermatids sit on their surface and utilize their nutrients and give them their waste. They also phagocytose failing cells.
What forms the blood-testis barrier?
Sertoli-Sertoli junctional complex
How can a vasectomy cause an immune reaction?
It breaks the blood-testis barrier.
What products are secreted from the Sertoli cells?
Androgen binding protein (keeps androgen in the tubules) and inhibin (feedback inhibitor of FSH release in the pituitary gland).
What is the sequence of events in spermato and spermiogenesis?
Spermatogonia (progenitor cells at base of seminiferous tubules) -> Primary spermatocytes (4n chromosomes & 2x DNA content from meiosis I) -> Secondary spermatocyte (1n chromosomes and 1x DNA, short lived) -> Spermatids (haploid in DNA and chromosomes) -> Spermatozoa (not yet motile/functional). As this process continues, the cells move closer and closer to the lumen.
What are the two phases of spermatogenesis?
Proliferation: 1) maintain progenitor cell population via mitotic division 2) Reduce DNA content & chromosome number by 1/2 through meiotic division. Differentiation: morphological changes
On EM what reflects the stage of sperm differentiation?
Their location in the wall: Green arrow = spermatogonia w/large nucleus. Orange arrow = primary spermatocytes actively dividing Yellow arrow = spermatids w/elongated nuclei.
Why are secondary spermatocytes hard to find?
In meiosis II you do not replicate the DNA so it is an extremely fast process.
What is spermiogenesis?
Spermatids begin to polarize from a round cell -> golgi accumulation fuses to form acrosomal vesical -> cell becomes more elongated -> acrosomal cap moves on top of nucleus -> flagella begins to develop -> mitochondria arranges around flagella -> cytoplasm is shed to leave nucleus, acrosomal cap and flagella. Spermatozoa leaving the seminiferous tubules are immotile and immature. Maturation takes place in the epididymis.
What is in the head of a spermatozoa?
The acrosomal cap contains enzymes (hyaluronidase, acrosin) and DNA.
What happens here?
Note the pseudostratified epithelium characteristic of the epididymis. This is where the spermatozoa mature and contains a lot of nutrients for the developing sperm.
How does activation of the sperm occur?
Acrosomal contact with the egg.
Where is the majority of blood supply found in the testis?
Intertitium. This is where the Leydig cells are that are secreting hormones into the blood. It will not be in the seminiferous tubules due to the testis-blood barrier produced by the Sertoli cells.
Run through the development of the testis?
Week 3) Yolk sac -> genital ridge. Week 4-8) Primordial testis, hCG stimulates Leydig production of testosterone Week 9) Scrotum forms, testis move to internal inguinal ring Week 13) Processus vaginalis forms path for testis decent into scrotum Weeks 26-36) Testis descend into scrotum & epididymus develops Week 37-40) Processus vaginalis closes
What is it called if the testis do not descend through the processus vaginalis into the scrotum?
Cryptorchidism = sterility because normal testicular function requires a temperature lower than body temperature.
Fluid accumulation in processus vaginalis
Hydrocele
2 factors that maintain proper temperature for spermatogenesis
Cremaster muscle suspends it and contracts, relaxes as needed. Cooled by venous pampiniform plexus.
What is the sperms pathway out of the testes?
Seminiferous tubules -> Straight tubules (Sertoli-like, epithelium only) -> Rete testis (epithelium w/microvilli only in mediastinum testes) -> Ductuli efferent (pseudo stratified columnar ciliated epithelium surrounded by thin layer of smooth muscle) -> Head of epididymis (stereo cilia on pseudo stratified columnar w/circular muscle layers, highly coiled, spermatozoa mature here) -> Stored in tail of epididymus -> Sympathetic stimulation sends them out the vas deferens (star shaped, pseudo stratified stereo cilia w/muscle) -> up the spermatocord -> through the inguinal canal -> enters pelvis through deep inguinal ring -> joins seminal vesicles -> ejaculatory duct in prostate -> urethra
How long does it typically take for a spermatogonia to develop into a spermatozoa?
74 days
What is Leydig secretion of testosterone dependent on?
Interstitial cell stimulating hormone (ICSH) from the anterior pituitary, an analogous hormone to LH in females
How is the muscle layer of the vas deferens arranged?
Thick outer longitudinal layer + inner circular layer + thin inner longitudinal layer
High folded tubes, walls appear to have pockets or cysts, pseudo stratified columnar epithelium with smooth muscle walls.
Seminal vesicles.
What is the function of the seminal vesicles?
To make the semen rich in fructose and prostaglandins that is released by contractile force during ejaculation with the sperm
Tubulo-alveolar glands, columnar to cuboidal epithelium surrounded by a fibroelastic capsule and smooth muscle.
Prostate gland.
What does the prostate make?
Enzymes (like prostate specific acid phosphatase, PSA and fibrolysin) and citrate that are expelled from the prostate gland lumen into the urethra and decrease semen viscosity after ejaculation.
Tubuloalveolar mucus glands
Bulbourethral glands, lubricate the urethra prior to ejaculation
How does an erection occur?
ACh stimulates endothelial NO and VIP production -> smooth muscle makes cGMP -> vasodilation -> corpora cavernosa and spongiosum fill with blood. These are surrounded by a fibrous capsule, tunica albuguinia, that compresses the venous return. This results in erection.
How does sildenafil maintain an erection?
It blocks PDE5 breakdown of cGMP and it is around longer to relax the smooth muscle
How does ejaculation terminate an erection?
Sympathetic stimulation causes contraction of trabecular smooth muscle in the helical arteries and blood can leave
