Sperm and Fertility
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42 Terms
Where does sperm production occur?
seminiferous tubules of testes
When does spermatogenesis begin?
at puberty
What are the three phases of spermatogenesis?
mitotic division, meiotic division, cytodifferentiation
What is the function of Sertoli cells?
support developing sperm cells
Where are Leydig cells found, and what do they do?
outside seminiferous tubules, produce testosterone
What happens to spermatogonial stem cells at puberty?
reactivate and divide by mitosis
What happens to the two daughter cells after spermatogonial mitosis?
one remains a stem cell, other continues developing
Where does mitosis occur during spermatogenesis?
basal compartment of seminiferous tubules
What happens when developing cells move between Sertoli cells?
enter adluminal compartment and become primary spermatocytes
How many chromosomes do spermatogonia and primary spermatocytes have?
46 chromosomes, diploid, 2n
What happens during meiosis I?
primary spermatocytes divide into secondary spermatocytes
How many chromosomes and chromatids does a secondary spermatocyte have?
23 chromosomes, each with two chromatids
What happens during meiosis II?
two secondary spermatocytes divide to produce four haploid spermatids
How many chromosomes do spermatids have?
23 chromosomes, haploid, n
What is spermiogenesis?
transformation of round spermatids into spermatozoa
What happens to excess cytoplasm during spermiogenesis?
form residual bodies which are engulfed by sertoli cells
Where do sperm go after formation?
lumen of seminiferous tubules
What are the three main parts of a sperm?
head, mid piece, tail
What does the sperm head contain?
nucleus, acrosome
What is the function of the sperm nucleus?
contains dna
What is the acrosome?
enzyme filled cap that helps sperm penetrate the eggs coverings
What is the function of the sperm midpiece?
contains mitochondria that produce energy
What is the function of the sperm tail?
propels the sperm
What is the function of the zona pellucida?
layer of glycoproteins around oocyte, allows entry of one sperm
What is the hormonal pathway controlling sperm production?
hypothalamus releases gnrh, anterior pituitary releases fsh and lh, act on testes
What does LH do?
stimulates leydig cells to produce testosterone
What does FSH do?
act on sertoli cells to support spermatogenesis
What is the role of testosterone in reproduction?
supports sperm production and male secondary characteristics
What is androgen-binding protein (ABP)?
product of sertoli cells that binds testosterone
Why is testosterone important for spermatogenesis?
developing sperm cannot mature without it
What is the function of inhibin?
reduces fsh secretion through negative feedback
How does testosterone regulate its own production?
negative feedback reduces gnrh and pituitary gonadotrophin secretion
What is the role of kisspeptin?
regulates gnrh release
What is male infertility?
reduced ability to achieve fertilisation due to low sperm count or poor sperm motility
What is oligospermia?
low sperm count, lower than 20m/ml
What is azoospermia?
no sperm present
What does it mean if sperm are immotile?
cannot swim
What is IVF?
oocytes collected and fertilized outside of the body
Approximately how many motile sperm does IVF require?
50,000
What is ICSI? (Intracytoplasmic Sperm Injection)
one sperm directly injected into oocyte
Does sperm need to be motile for ICSI?
no
Where can sperm for ICSI be collected from?
semen or from testes by biopsy