Reproductive System - II Flashcards
describe the accessory structure, the scrotum
contains:
- two testes
- two epididymides
- two spermatic cords (with part of ductus deferens)
- houses testes away fro the body to maintain temperature at ~34 decrees celsius
- scrotum lined by dartos muscle - lines inside of scrotum, when it contracts it wrinkles the skin, decreasing the surface area needing to be heated
- cremaster muscle - contracts for heat conservation, covers spermatic cord and testes, brings them up closer to the body for heating
describe the spermatic cord
- there are two spermatic cords
- runs between abdomen and testes
- contains: ductus deferens, blood vessels - testicular artieries and veins (veins are called venous plexus, which is like a web around the artery, increasing the surface area for thermal exchange to cool the blood from the body to the ~34 degrees), nerves, lymphatics
describe the accessory structure, the penis
dual function:
- urination
- copulation
cylindrical organ:
- root (bulb): where the penis is adhered to the urogenital triangle of the body wall
- body
- glans covered by prepuce/foreskin
contains three cylindrical erectile tissues:
Two corpora cavernosa (sing. = corpus cavernosum):
- main erectile tissue
- dorsal aspect
One corpus spongiosum:
- contains urethra
- forms bulb and glans
- ventral aspect
- not as much erectile tissue because don’t want to block urethra
describe the accessory glands
- spermatozoa carried to female reproductive tract in seminal fluid (together called semen)
- seminal fluid is mostly proceeds by three types of accessory glands
- seminal vesicles
- prostate gland
- bulbourethral glands - seminal fluid functions: fluid medium to carry spermatozoa from male to female reproductive tracts, protection for the spermatozoa against acidic vagina or urine, energy/nutrition for the spermatozoa, lubrication, motility (interaction between seminal fluid and spermatozoa cause motility)
describe the seminal vesicles
two glands located:
- posterior to bladder
- lateral to ampulla
produce viscous secretion:
- makes ip ~60% of semen
- alkaline pH protects sperm against acidic environment in urethra and vagina
describe the prostate gland
location:
- inferior to bladder
- wraps around prostatic urethra
produces secretion:
- ~30% of semen
- slightly acidic, milky fluid
- contains PSA: prostate-specific antigen
- contributes to sperm activation, viability and motility
describe the bulbourethral glands
- two glands located in the urogenital diaphragm
- open into spongy/penile urethra
- contribute ~5% of semen volume
- secretions lubricate and neutralise acidity in urethra prior to ejaculation
- last 5% of semen is made of spermatozoa
what is a vasectomy?
- surgical method of sterilisation in males
- cut the ductus deferens (cut ends tied or cauterised)
- this has no effect on seminal fluid a this fluid doesn’t contain sperm
- it would reduce semen volume as sperm is part of this though
describe gametogenesis
formation of the gametes (sex cells)
- spermatogenesis in males
- oogenesis in females
under hormonal control
occurs via mitosis and meiosis
- cells need to be haploid (23 chromosomes)
brief overview of meiosis
- same basic process in males and females
- original cell has 46 chromosomes (diploid/2n)
- two cycles of cell division to produce gametes (23 chromosomes = haploid/n)
- meiosis I: 2 haploid cells produced from one original diploid cell
- meiosis II: each cell produced from meiosis I divides to produce two haploid cells with 23 chromosomes
describe spermatogenesis
- formation of the male gamete
- the process by which spermatogonia are transformed to mature spermatozoa (sperm)
- occurs continuously from puberty onwards
- occurs in the seminiferous tubules
what occurs in the first stage of spermatogenesis?
- spermatogonia divide by mitosis into 2 daughter cells (diploid - 46 chromosomes)
- one spermatogonium (type A) stays at the basement membrane of the seminiferous tubule - this is important because they are the steam cells so one has to stay behind to produce more
what occurs in the second stage of spermatogenesis?
- the second spermatogonia (type B) differentiates into a primary spermatocyte (diploid), which undergoes meiosis I
- form 2 secondary spermatocytes (haploid - 23 chromosomes, have the right number of chromosomes but too much DNA)
what occurs in the third and final stage of spermatogenesis?
- these undergo meiosis II to form spermatids (haploid)
- spermatids differentiate into spermatozoa with a head, body and tail via spermiogenesis
- spermiogenesis is the process of differentiation from a circular cell to one with a tail and stuff, it is part of spermatogenesis
- spermatozoa released into lumen, then transported down the tuble by fluid
what are some key structural changes that occur during spermiogenesis
- acrosome starts to form (the triangle pointy bit, contains enzymes that help it enter the oocyte)
- tail forms (flagella)
- excess cytosol with extra organelles comes away and is disposed of
- lots of mitochondria to provide these cells with lots of energy
