Reproductive Lecture 3 🔮🍑 Flashcards
Where dose Sperm Production: Spermatogenesis take place
Takes place in the seminiferous tubules of the testes
Spermatogenesis Only occurs after
puberty
There are three phases to spermatogenesis
- mitotic division
- meiotic division
- Cytodifferentiation
huge numbers of sperm are produced constantly by the
mature male ….how much
300 – 600 sperm/gram of testis tissue/second
Spermatogenesis
• At puberty the
primary gem cells are
reactivated
– spermatogonial stem cells.
The spermatogonia divide by mitosis.
1 daughter cell remains undifferentiated -to
maintain the stem cell population.
The other daughter cell continues to divide by
mitosis forming
spermatogonia.
The spermatogonia continue to divide by mitosis.
Spermatogenesis
Where do the mitotic divisions occur
in the basal compartment of
the seminiferous tubules
Spermatogonia have how many chromosomes ?
46
When the mitotic divisions are complete the spermatogonia
move between
adjacent sertoli to the adluminal
compartment of the seminiferous tubules.
In the adluminal compartment the cells are called
primary spermatocytes –they undergo meiosis
Each of these primary spermatocytes starts with
n-46
The primary spermatocytes undergo
meiosis I
the DNA content …….
doubles - each of the spermatocytes still has46 chromosomes. (meiosis I).
The primary spermatocytes then divide to produce
secondary spermatocytes
Secondary spermatocytes have …
How ,any chromosomes and how many chromatids ?
23 chromosomes, each
chromosome has two chromatids.
Secondary spermatocytes divide very rapidly by ………….. to give …………….
meiosis II
- to give four spermatids each with 23 chromosomes.
Spermiogenosis Round spermatids.
Spermatids are still round cells and have a round
morphology
The final process in spermatogenesis is
spermiogenesis in which the round spermatids
differentiate their shape and become
spermatozoa (Sperm).
Sperm move into the
lumen of the seminiferous
tubules
The midpiece on the sperm is
packed with mitochondria to produce energy
The sperm head contains
the DNA and is covered by the acrosome a compartment filled with enzymes that are required for egg penetration.
The excess cytoplasm of the spermatid is also lost into a structure
called
the residual body that is phagocytosed by the Sertoli cells after the sperm leaves
Sertoli Cells
(inside seminiferous tubules In direct contact with…..
spermatogonia
Male infertility
A common feature of infertile men is a reduced sperm count <20 million/ml
=
oligospermia
no sperm =
azoospermia
Male infertility
can’t swim
immotile
Male infertility
• IVF- in vitro fertilisation
- Oocytes are harvested and fertilised ex vivo
– Requires approximately 50,000 motile sperm
ICSI- IntraCytoplasmic Sperm Injection.
– A single sperm is injected directly into the oocyte
– Sperm does not even need to be motile
– Can use sperm collected by biopsy from the
testes!!!
