Flashcards in gamete interaction Deck (62)
when does the semen coagulate?
rapidly during or immediately after deposition
the coagulation of semen may become...
gelinatous (human, pig, horse)
fibrous (guinae pig)
how does the semen coagulate in humans?
enzymes from the prostate interact with fibrinogen like substrates derived from the seminal vesicle.
why does coagulation of semen happen?
to retain spermatozoa in the vagina or buffer it against the hostile acidity of the vaginal fluids
how long does it take for the coagulum to dissolve in the female tract?
20- 60 minutes
what percentage of sperm does not enter the cervix?
how long for and where are the sperm stored in the cervix?
humans 3-4 days
mice 0.5-1 days
deep in the cervical crypts of the mucus membrane
what are the sperm nourished by in the cervix?
what does the profession of the sperm to the uterus depend on?
the absence of progesterone domination (only in the absence does the mucus permit sperm penetration)
abnormal sperm are prevented from passing further up the reproductive tract
in humans what aids sperm movement through the uterus?
probably aided and directed by peristaltic contractions
how do the sperm travel across the uterotubule junction and enter the oviduct?
by their own propulsion
however the uterotubal junction regulated entry to the oviduct by its action as an intermitted sphincter
what happens when the sperm reach the isthmus of the oviduct ?
they linger and bind temporarily to oviductal epithelial cells.
what happens as a result of the sperm binding to the oviductal epithelial cells ?
the oviductal cells are stimulated secrete factors that serve to maintain the stored sperm in a viable state.
when do the sperm detach from the oviductal epithelial cells? where do they swim?
only at ovulation
they swim to the ampillary isthmus junction at the site of fertilisation
in vitro studies suggest that this process may depend on the release of chemo-attractants by both the oocyte and the cumulus mass.
what is the process called when sperm gain full fertilising capacity?
what are two characteristics a fully capacitated sperm can be distinguished by?
1) hyperactive motility -> the flagellar beats are stronger with a wider amplitude or whiplash beats.
2) A change in surface membrane proteins that leave the sperm responsive to signals encountered when close to the oocyte.
What changes are needed for a sperm to be a full capacitated state?
- oestrogen primed uterus/oviductal isthmus
- critical features of secretions of female reproductive tract (proteolytic enzymes, cholesterol binding sinks, higher ionic strength compared with seminal plasma)
- when ejaculate is exposed to atmospheric oxygen, reactive oxygen species form and stimulate the production of H2O2 a potent capacitating agent.
what is a physiological changes in the sperm during the process of capacitation?
stripping from and/ or modification of many of the glycoproteins that coat the sperm surface during passage through the epididymis and in the seminal plasma. (associated with change to the surface charge and macromolecular organization and lipid structure of the sperm membrane, especially loss of cholesterol.
What are the first steps of capacitation?
Where may they commence?
What are they followed by?
removal of glycoproteins and cholesterol efflux
may commence in the cervix
followed by an increased pH and calcium entry, generation of cAMP, activation of protein kinase A and the phosphorylation of tyrosines on a number of proteins
which part of the oviduct helps to stabilise the capacitated sperm?
the isthmic region
when does the sperm move to the ampullary-isthmic junction?
when an egg has been ovulated
what does the sperm need to penetrate before contact with the oocyte can occur?
cumulus of granulose cells
what is hyaluronidase?
it is the enzyme that digests the matrix of the cumulus cells causing them to fall apart.
the sperm acrosome is a rich source of hyaluronidase
what happens during the acrosome reaction?
the acrosome swells
its membrane fuses with the overlong plasma membrane
a vesiculated appearance is created
the contents of the acrosomal vesicle and the inner acrosomal membrane both become exteriorised in a process of exocytosis
what is the terminal phase of capacitation?
what is located on the inner acrosmal membrane which digest a path through the zona pellucida?
proteolytic enzymes such as across
(a path with the acrosome reacted sperm pass through aided by the whiplash forward propulsion of the hyper activated tail)
how long does penetration on the zona take?
between 5 and 20 minuted
why is it though to be important that the acrosome reaction occurs close to the oocyte?
because acrosome reacted sperm have a very short life span
what is between the zona pellucida and the oocyte membrane?