Lecture 44 Flashcards
What structures is the penis made up of? What are the erectile tissues?
The penis is involved in both urination and copulation, it is a cylindrical organ with a root (bulb, attachment site to the body), body and the glans (covered by the prepuce/foreskin). There are three cylindrical erectile tissues: two as the corpora carvernosa (corpus cavernosum) (main erectile tissue, on the dorsal aspect (upper part)), one is the corpus spongiosum (contains the urethra, forms the bulbs and glans and is the ventral aspect (lower part)).
Why is there large venous surface area in the scrotum? What is the cremaster muscle. What is the temperature dcontrolled at.
In the scrotum there is a large amount of venous surface area, this allows for large temperature control via the scrotum. The cremaster muscle is a muscle found in the spermatic cord which can contract for heat conservation. The temperature is controlled at roughly 34 degrees.
How is a vasectomy done and why?
A vasectomy is a method of contraception, it is done via cutting/tieing the ductus deferens. This prevents sperm from joining the seminal fluid.
What are accessory glands and what are the components of semen?
Accessory glands are associated with the male reproductive system, they contribute to seminal fluid composition and volume and are the seminal vesicles(we have two, make up 60% of total volume, behind the urinary bladder (lateral to ampulla of ductus deferens) and form ejaculatory duct with ampulla, contains fructose for nourishment of sperm and provides alkaline pH to neutralise the acidic environment of the urethra and vagina), the prostate gland( inferior to bladder, wraps around prostatic urethra and makes up 30% of semen, slightly acidic milky fluid which contains enzymes (prostate specific antigen), double check this one) and the bulbourethral glands (two glands in urogenital diaphragm, opens into the spongy/penile urethra and contributes 5% of semen volume which acts to lubricate and neutralise acidity in the urethra before ejaculation), sperm makes up the last 5%.
What is gametogenesis?
Gametogenesis is the formation of the sex cells (spermatogenesis in males, oogenesis in females). It occurs via meiosis (needing haploid 23 + 23 makes 46) and is under hormonal control.
What is spermatogenesis? What parts do sperm have and How does it occur?
Spermatogenesis is the process by which spermatogonia are transformed to mature spermatozoa (formation of male gamete), sperm have a head (acrosome cap on head, contains enzymes to break into egg) a body (containing mitochondria for energy) and a tail (flagellum).
During development spermatogonia migrate from the yolk sac to testes and remain dormant until puberty, during puberty the spermatogonia divide via mitosis into type A (for replenishment of type B) and type B (both diploid, 46), The type B differentiate into primary spermatocytes (diploid) which undergo meiosis I, it forms 2 secondary spermatocytes (haploid), these undergo meiosis to form spermatids (haploid), these differentiate into spermatozoa with a head, body and tail via spermiogenesis. These spermatozoa are released into the lumen and four are produces from the original type B cell. The sperm needs to develop further in the epididymis to become viable.
What is meiosis and what are the stages?
Meiosis is two cycles of cell division to produce the gametes, it is the same for spermatozoa or ova, meiosis I produces two cells from 1 for haploid cells, is meiosis II each cell produced in meiosis I breaks up to form 2 haploid cells.
Where does spermatogenesis occur and what hormones are involved?
Spermatogenesis occurs in the seminiferous tubules and is controlled by many hormones: gonadotropin releasing hormone from the hypothalamus, leading to production Luteinising hormone (stimulates production of testosterone)and follicle stimulating hormone (controls spermatogenesis, increase) from the anterior pituitary (also gonadotropins), testosterone is an androgen and is produced in Leydig cells, lastly is inhibin (inhibits FSH) produced in the Sertoli cells. Negative feedback of testosterone also suppresses LH and GnRH.
