Sperm transport and Fertilization

Sperm Transport in the Female Genital Tract
of Different Animals
Deposition of semen by male:
Sperm deposited in the cranial part of the vagina
of cow, sheep, bitch, queen, and primates.
In the pig and horse the sperm is directly
deposited in the cervix or uterus.
Volume of semen in animals:
In ruminants: Amount of semen is small in volume,
from 3-5 ml with high proportion of spermatozoa.
But majority of the spermatozoa destroyed by
retrograde transport.
Sperm Transport in the Female Genital Tract
of Different Animals
Volume of semen in animals:
In boars:
The volume of ejaculate is large (200-400 ml) with low
concentration of spermatozoa. The boar ejaculate in
3 fraction. The first fraction contains few
spermatozoa with secretion from accessory glands.
The second fraction is rich in spermatozoa. The third
fraction is consists of the secretion of bulbourethral
gland which form coagulum that reduces retrograde
sperm loss.
Sperm Transport in the Female Genital Tract
of Different Animals
In Stallion:
The stallion ejaculates in a series of “jets”. In the first
jets the proportion of spermatozoa is maximum. The
later Jets contains highly viscous mucous to block the
retrograte spermatozoa loss.
In dog:
First ejaculate is clear fluid from prostate and ranges
from 0.5 to 5 ml. Second one is rich in spermatozoa
and the volume ranges from 1-4ml and contains 300
million to few billion spermatozoa. The third fraction
is from the prostate also and contains high volume of
fluid ranges from 1 to 80 ml.
Sperm Transport in the Female Genital Tract
of Different Animals
In birds:
The spermatozoa of the ejaculates of the cock reserves in the
“sperm-host-gland” at the uterovaginal junction or at the
infundibulum of the oviduct of hens. Here, the spermatozoa
nourished by the enriched nutrient secreted by the tubular
gland of sperm-host-gland. In these gland spermatozoa can
survive up to three month and can fertilize the ova of hen.
Transport of spermatozoa to the ampulla of the mammalian
 Due to tone and motility of the tunica muscularis of the
female genital tract.
Steps of Fertilization
1. Capacitation
Changes of the spermatozoa in the female
reproductive tract occurred after ejaculation
by male constitute capacitation. Without this
changes spermatozoa cannot fertilize the egg.
Capacitation begins in the uterus and end in the
isthmus of the oviduct.
Steps of Fertilization
1. Capacitation
Capacitation process includes:
(1) Removal of the glycoprotein coat and
seminal plasma proteins from its surface.
(2) Alteration in the flagellar motility that are
necessary to penetrate the zona pellucida.
(3) Development of the capacity to fuse with the
plasma membrane of the oocyte.
Steps of Fertilization
2. Interaction Between Spermatozoa and the Zona Pellucida
The zona pellucida (ZP) is an extracellular matrix
surrounding the oocyte and the early embryo.
Following steps are needed for perfect fertilization:
1. Capacited spermatozoa bind with the ZP.
2. Acrosome reaction and penetration of the ZP.
3. Modification of the ZP that prevent polyspermy
(prevent to enter more than one spermatozoa).
Steps of Fertilization
3. Acrosomal Reaction
Acrosomal reaction performed
by following steps:
1. The spermatozoa adhere with the
zona pellucida.
2. Acrosomal cap secretes hydrolytic
enzyme acrosin & hyaluronidase
3. Above two enzymes digest the
Jelly coat and vitelline layer of ZP.
4. By the propulsive action of the tail
and actin filament, spermatozoa
Enters into the oocyte.
Stage of Fertilization
4. Syngamy
 After penetration of ZP, sperm adhere to and
fuse with the plasma membrane of the
 The membrane of oocyte fuse with the
membrane of spermstozoon.
 In the later stages the oocyte engulf fertilizing
spermatozoon including its tail. This
mechanism is called syngamy.
 The molecular protein fertilin α, fertilin β,
and cyritestin causes fusion.
Stage of Fertilization
5. Oocyte activation
This step include:
Establishment of a block to prevent polyspermy. It is
accompanied by releasing of cortical granules which prevent other
spermatozoa to enter into the oocyte.
ii. Resumes of meiosis and pronucleus formation: It includes a)
resumes of meiosis II, formation of ovum with enough yolk (at this
stage is called Zygote) and 2nd polar body.
b) Several changes of the nucleus of the spermatozoa which leads
to the formation of male pronucleus.
c) Changes in the nucleus of the zygote to form female pronucleus.
d) Fusion of the male and female pronuclei, union of male and
female haploid genomes in the centre of the zygote, a process
known as synkaryosis. This leads to the mitosis and start to form
new individuals.

similar documents