Mod.A Embryology Lec1 Flashcards
Spermatogenesis (aim, site, duration)
Aim. Formation of sperms with haploid
number of chromosomes 23X or 23Y.
Site. In the seminiferous tubules of the testis.
Duration. From puberty till death.
Steps of spermatogenesis;
1-proliferation
2-growth
3-maturation
4-transformation
1- proliferation:
It Means increase in the number of the cells.
Spermatogonia (which have diploid number of chromosomes 46XY), divided by MITOSIS into 2 daughter spermatogonia which have also diploid number of chromosomes.
2- Growth:
each daughter spermatogonia enlarges in size forming primary spermatocyte
3-Maturation
1st maturation division:
each primary spermatocyte divides by meiosis into 2 secondary spermatocytes (haploid 23X or 23Y)
2nd maturation divi4-sion:
each secondary spermatocyte divides by mitosis(meiosis II) into 2 spermatids (haploid)
4-Transformation, spermiogenesis:
Nucleus = head.
Golgi = acrosamal cap.
Centeriols = axial filament.
Mitochonderia = helical sheath.
The sperms undergo maturation in the?
epididymis for about 60-64 days,
then stored in the ampulla of vas defferens.
If not ejaculated, they die and become absorbed.
Sperm (length, formed of)
Total length=60 μ
Formed of: 1- Head which contains Nucleus with haploid number of chromosomes which carry the genetic characters. Acrosomal cap. Secretes enzymes which facilitate penetration of the ovum.
2- Neck.
3- Body or middle piece. Contain
mitochondrial sheath which produce
energy for motility.
4- Tail .
Characters of the sperms
Viability: Sperm remain viable for 1-2 days in the female
genital tract.
Mobility: At least 70% are mobile.
Abnormal forms: Should not be more than 10%.
Abnormal forms as giant, dwarf or joined sperm.
Semen (source) (volume) (count)
1- Sperms from the testes
2- Secretions of the seminal vesicles, prostate, bulbourethral
glands and urethral glands.
volume 3-5ml
sperm count: 100 million
Necrospermia
dead sperms.
Oligospermia
low sperm count.
Azospermia
absence of sperms.
Semen analysis (importance)
diagnosis of evaluating patient with
male infertility.
male infertility:
a man with less than 15M sperm/ml and 40% total
motility is diagnosed with male
infertility.
types of male infertility:
Male infertility can be either
diagnosed as
insufficient numbers of
sperm in the ejaculate
(oligozoospermia)
absence of
sperm (azoospermia)
poor sperm motility (asthenozoospermia)
decreased normal morphology
(teratozoospermia).
Oogenesis (aim, site, duration)
Aim. Formation of ovum ( single large and haploid)
Site. In the ovary . Each ovary produce one ovum every 2 months.
Duration. From intrauterine life till menopause
Steps of oogenesis:
Two prenatal stages occur in intrauterine life
proliferation
growth
maturation
proliferation.(oogenesis)
Oogonia with diploid number of chromosomes 46XX divided by mitosis giving 2 daughter oogonia.
growth.(oogenesis)
The daughter oogonia enlarge forming primary oocytes .
Each primary oocyte become surrounded by follicular
cells forming a primordial follicle, further changes are
arrested till puberty.
when does maturation occur in oogenesis
after maturation
maturation.(oogenesis)
occurs once per month
5-15 primordial follicles begins to grow, one only
continues maturation and the rest degenerate
forming atretic follicles.
1- First maturation division
The primary (1ry) oocyte divided by meiosis giving
secondary oocyte and first polar body.
2- Second maturation division
It occurs after ovulation and only if fertilization occur.
The 2ry oocyte divided by mitosis into mature ovum
and second polar body which extruded to the
perivitelline space and degenerate.
