Spermatogenesis Flashcards
Label the male reproductive anatomy.
Where is sperm made?
pathway of sperm?
Where do the ejaculatory ducts feed into?
Testes make + store sperm in the epididymis
Sperm carried from epididymis -> ductus deferens–> urethra, which unites w the seminal vesicle to form ejaculatory ducts
Ejaculatory ducts feed into urethra at seminal colliculus, within the prostate - urethra then runs through prostate & penis
5 features of testes
why are testes in scrotum?, what happens when sperm enters vagina, overheated testes?, normal volume & how this is measured
Testes lie w/in scrotum bc sperm production is 1.5-2.5oC lower than body temp - Also, when sperm enters vagina it warms up, which could potentially activate spermatozoa
Overheating of testes reduces sperm count
Testes are well-vascularised, w dense nerve innervation
Testes normal vol between 15 - 25ml; measured w an orchidometer
What is found on the basement membrane of semniferous tubules?
what are the walls of tubules made up of & which compartments do tight junctions between these form, what do these compartments act as + what is it filled with?
what are spaces between the tubules filled with?
Primary germ cells (spermatogonia) are found on basement membrane of the seminiferous tubules
Tubule walls are made up of tall columnar epithelial Sertoli cells. Tight junctions between these form adluminal compartments
The adluminal compartment is filled w sertoli secretions and acts as a specific enclosed environment for spermatogenesis.
Spaces between the tubules are filled with ISF, Leydig cells blood & lymph vessels
What are the 5 Sperm stages during spermatogenesis?
Where does mature sperm go?
.
How long is spermatogenesis and what is an important aspect of it?
New cycle every 16 days, entire process takes ~74 days:
One important aspect of spermatogenesis is the cytoplasmic bridges, which allow spermatids to remain connected, forming a syncytium. This enables synchronous development, meaning that diff spermatogenesis stages are happen simultaneously within the seminiferous tubules!
Spermatozoa that are fully matured and ready for ejaculation are released into the epididymis for storage until ejaculation
Compare and contrast Oogonia v Spermatogonia
Describe the process of steroid production in the testes
How much greater are intra testicular testosterone levels?
Leydig cells contain LHr + convert cholesterol–> androgens. Intra-testicular testosterone levels= 100x those in plasma.
Androgens cross over to & stimulate Sertoli cells- this controls spermatogenesis.
Sertoli cells also contain FSHr, which when activated upregulate aromatase + convert androgens to oestrogens. FSH establishes a quantitatively normal Sertoli cell population.
Androgen initiates & maintains sperm production.
What can happen if you take anabolic steroids?
- Testosterone (i.e. in anabolic steroids) will increase negative feedback along the HPG axis
- This will reduce FSH and LH secretion from the pituitary, therefore the testes won’t be stimulated, causing testicular atrophy
What happens during erection, ejaculation and evacuation
Point, shoot and score: erection (parasympathetic), ejaculation (sympathetic) and evacuation of semen (somatic)
Erection: PS stimulation vasodilates c. cavernosum, partially constricts venous return. This causes penis to get engorged w blood/erect
Ejaculation: symp inputs cause coordinated sm contractions along the ductus deferens, glands & urethra to move sperm + seminal fluid (emission)
Evacuation: Somatic ns (via perineal branch of pudendal nerve S2-S4) causes final contractions to expel cum out of urethra😳
Label this
What does ejaculate/seminal fluid consist of?
volume, how many sperm per ejaculate, how many get near to egg,
3 secretions seminal fluid consists of?
Vol ~1.5ml - 6ml
100-300m sperm per ejaculate, most lost before reaching ampulla of the uterine tube, around 120,000 sperm get near to egg, only one enters
Seminal fluid consists of secretions from: Seminal vesicles, prostate, bulbo-urethral gland combined w epididymal fluid
State 3 different parts involved in producing ejaculate, and specifically what they secrete.
Bulbourethral glands: clear, viscous pre-cum, high in salt. Lubricate urethra for sperm. Alkaline- neutralise any acidic urine
Seminal vesicles: secrete 50-70% of ejaculate. Has proteins, enzymes, fructose, mucus, vit C and PGs. High fructose give sperm energy. High pH protects sperm against acidic vagina
Prostate: milky white fluid. <1 Protein content inc proteases, prostatic acid phosphatase and PSA. These liquefy the ejaculate
Also high Zn conc (500-1,000x that of blood). Anti-microbial effect
When a male is potentially infertile, semen analysis can be carried out to further investigate the issue
When does this happen and what are the normal values approx?
What are some possible defects?
Note- to be considered a normal sample, just over 4% of cells need to be normal – this is bc spermatogenesis creates lots of cells v quickly, but v few of these cells are perfect (complete opp of oogenesis)
Describe the structure of the spermatozoon
What is the internal structure of the flagellum?
Mitochondria: provide energy to power the flagellum
Flagellum: propells the sperm along. The internal structure is the same as all microtubules – 9 pairs of fibres in a ring around a central column of 2 fibres
Acrosome: hydrolytic enzymes that digest the ZP
Nucleus: haploid DNA
