Testicular Function Flashcards
What is a gamete?
A mature haploid reproductive cell
What are male and female gametes called?
Spermatozoa in males, oocytes in females.
Why is a gamete haploid?
To ensure the embryo has the correct number of chromosomes.
What is a germ cell?
Cells that give rise to gametes.
What is gametogenesis?
The process by which gametes are made.
What is spermatogenesis?
Gametogenesis in males.
What is oogenesis?
Gametogenesis in females.
When does reproductive system differentiation occur in embryos?
Around week 7.
What happens during the indifferent stage in embryos?
Primordial germ cells (PGCs) arise.
What are PGCs?
Diploid germ cell precursors from the epiblast.
When do PGCs arise?
During gastrulation (week 3).
Where do PGCs migrate to?
The genital ridges.
What determines male vs female development?
Presence or absence of the Y chromosome.
What gene on the Y chromosome triggers male development?
SRY gene.
What is another name for the SRY gene?
Testis-determining factor (TDF).
What type of factor is the SRY gene?
An architectural transcription factor.
How does SRY function?
Changes DNA structure to allow other transcription factors to activate testis genes.
What evidence supports the SRY gene’s role in sex differentiation?
Mutation/translocation cases and transgenic mouse experiments.
Which cells express the SRY gene?
Columns of cells from the coelomic epithelium.
Name the 3 cell types that arrive at the genital ridges.
Coelomic epithelial cells, PGCs, mesonephric migratory cells.
What do coelomic epithelial cells form?
Primitive sex cords.
What do PGCs become once in sex cords?
Pro-spermatogonia.
What do sex cord cells become?
Sertoli cells.
What do mesonephric cells form?
Vasculature, Leydig cells, myoid cells.
Where does sperm develop?
In the seminiferous tubules.
What is found inside the seminiferous tubules?
Pro-spermatogonia and Sertoli cells.
Is meiosis active in early testis development?
No, it is inhibited.
What is found between seminiferous tubules?
Leydig cells and vasculature.
What hormones do testes begin to produce?
Androgens, AMH, and inhibin.
What are the 2 main functions of the testes?
Sperm and hormone production.
What is the blood-testis barrier (BTB)?
A barrier dividing seminiferous tubules into compartments.
What forms the BTB?
Junctional complexes between Sertoli cells.
Function of the BTB (immune protection)?
Prevents immune response against sperm.
Function of BTB (microenvironment)?
Controls transport of molecules for sperm development.
When does the BTB develop?
At puberty before spermatogenesis.
What is spermatogenesis?
Production of mature sperm.
How many sperm are produced daily?
~100 million.
Name the 3 phases of spermatogenesis.
Proliferation, division, differentiation.
Where does mitosis of prospermatogonia occur?
In the basal compartment.
What are As spermatogonia?
Spermatogonial stem cells.
What do A spermatogonia produce?
B spermatogonia.
What do B spermatogonia become?
Primary spermatocytes.
What happens in the division phase?
Meiosis I & II → spermatids.
How long does meiosis I take?
24 days.
What does meiosis produce?
Haploid spermatids.
What happens in the differentiation phase?
Spermatids become spermatozoa.
What structures form during differentiation?
Acrosome, flagellum, nucleus, mitochondria, cytoplasm loss.
Why can men produce sperm indefinitely?
SSCs are self-renewing.
What is the acrosome?
Golgi-derived vesicle with enzymes to penetrate the egg.
What is the flagellum’s role?
Sperm motility.
What forms the flagellum?
Centrioles.
Role of mitochondria in sperm?
Energy for motility.
Where is sperm DNA located?
In the nucleus.
What happens to histones in sperm?
Replaced by protamines.
What happens to excess cytoplasm?
Shed and phagocytosed by Sertoli cells.
Why is sperm transcriptionally inactive?
DNA is tightly packed and no protein machinery remains.
What is spermiation?
Release of sperm into the tubule lumen.
How long is spermatogenesis in humans?
64 days.
What controls spermatogenesis timing?
Germ cells.
What is the spermatogenic wave?
Continuous sperm production at different stages.
What are the main testis hormones?
Androgens, estrogens, cytokines.
What produces testosterone?
Leydig cells.
Where does testosterone go?
Blood, lymph, seminiferous tubules.
What converts testosterone in seminiferous tubules?
Sertoli cells via 5α-reductase.
Role of DHT in Sertoli cells?
Supports spermatogenesis.
What does ABP do?
Binds testosterone to maintain high local levels.
What produces inhibin?
Sertoli cells.
Function of inhibin?
Inhibits FSH from pituitary.
What produces AMH?
Sertoli cells.
Role of AMH?
Regression of Müllerian ducts.
Are sperm motile when leaving testis?
No.
What do sperm require for fertilisation?
Maturation and capacitation.
Where does sperm maturation occur?
Epididymis.
Function of epididymis cells?
Reabsorb fluid, alter sperm surface proteins.
What regulates epididymis function?
Estrogen and androgens.
How long does sperm maturation take?
10–14 days.
Epididymis segments?
Caput, corpus, cauda.
Function of caput?
Enables motility.
Function of corpus?
Enhances fertilising ability.
Function of cauda?
Stores sperm.
What is the vas deferens?
Tube connecting epididymis to ejaculatory duct.
Function of vas deferens?
Major sperm reservoir.
What is a vasectomy?
Ligation of vas deferens to prevent sperm in ejaculate.
What is ejaculation?
Sperm transport from male to female.
What is semen?
Sperm + seminal plasma.
Sperm count in ~2ml semen?
~200 million.
What secretes seminal plasma?
Accessory sex glands.
What are male accessory sex glands?
Prostate, seminal vesicles.
Functions of seminal plasma (4)?
Transport, nutrition, buffering, antioxidant.
Is ejaculate homogeneous?
No.
STI agents are in what semen part?
Seminal plasma.
Seminal vesicle structure?
Sac-like glands.
Where do seminal vesicles empty?
Ejaculatory duct.
Function of seminal vesicle fluid (3)?
Clotting, retention, sperm protection.
Structure of prostate?
Solid tissue mass.
When does prostate secrete?
During copulation.
What does prostate secrete?
Alkaline, zinc-rich fluid with enzymes.
Function of prostate secretions?
Liquefaction of ejaculate post-entry.
Which gland gives most ejaculate volume?
Seminal vesicles.
What is the bulbourethral gland?
Cowper’s gland, secretes pre-ejaculate.
Function of pre-ejaculate (2)?
Lubrication, neutralisation of urethra.
Can pre-ejaculate contain sperm?
Yes, if recent ejaculation.
What is capacitation?
Physiological change allowing egg penetration.
When does capacitation occur?
In female reproductive tract.
