T3: Gamete Transport Flashcards
what is the overview of sperm challenges
- transport
- capacitation
- hyperactivation
- chemotaxis/recognition
5.cumulus penetration - sperm-zona binding
- acrosome reaction
- egg penetration
- fertilization
how long does sperm transport through bovine and oviduct take
4-16 hours
how long does it take dead/defective spermatozoa to pass through the oviduct
15 mins
what are some barriers for the sperm
- vagina/cervix/uterus
-uterotubal junction
-isthmus/ sperm reservoir
what are some barriers to the oocyte
-follicle wall
-infundibulum
-ampulla
what are the semen depositions for species
vagina: cow, sheep, primates
cervical: mouse
intrauterine: sow, mare
what happens with the sperm in the cervix
spermatozoa migrate along the walls/ folds, not through the lumen
name the challenges for sperm deposition
-acidic PH in vagina (high lactate secretion)
-retrograde/backflow of semen
-long uterine body and horns
-leukocytic infiltration of uterus
what are the solutions to the challenges of semen deposition
-alkaline ph of seminal plasma
-cervical mucus serves as a vehicle for sperm and a filter for seminal plasma
-uterine muscle contractions increase in the late follicular phase
-timing of immune response to sperm is delayed (leukocyte infiltration occurs only after coitus)
what is included in immediate transport
-retrograde loss
-phagocytosis
-entrance into cervix/uterus
what is included/processes in the cervix
-privileged pathways
-removal of non-motile sperm
-removal of some abnormalities
what is included/processes in the uterus
-capacitation initiated
-phagocytosis
what is included/processes in the oviduct
-capacitation completed
-hyperactive motility
what is included/processes in fertilization
-acrosome reaction
-spermatozoon penetrates oocyte
-male and female pronuclei form
what are the two phases of sperm transport
rapid and sustained transport phase
what is included in the rapid transport phase
-within a few minutes sperm can be found in oviduct
-these sperm are non-viable and do not result in fertilization
what is included in the sustained transport phase
-trickle like delivery over hours
-these are the capacitated sperm that do not result in fertilization
what are the two types of mucous in cow
sialomucin: low viscosity and helps forward movement( helps create a privileged pathway: basal cells/ crypts
sulfomucin: high viscosity and washes sperm out: apical cells, cervical
what king of environment is important for the privileged pathway?
low viscosity environment in the valley of the cervix creates a “privilege pathway” for healthy spermatozoa
what are the challenges for the uterotubal junction/ solution
fold in mucosa (dead ends), viscous fluid, removal of seminal plasma, removal of defective/slow spermatozoa
solution: waves of contractions
what is the oviductal sperm reservoir and where is it present
binding of spermatozoa to oviductal epithelium in utero-tubal junction or isthmus
- present in cows, pigs, hamsters, sheep, mares
what are the proposed functions of the oviductal sperm reservoir
-maintenance of spermatozoa between the onset of oestrus and ovulation
-synchronization of sperm/ egg transport in oviduct
-prevention of polyspermy
-capacitation and hyperactivation
in cattle, earlier _____ reduces ______
earlier insemination reduces fertilization rates but increase embryo quality (timing difference between mating and ovulation
describe the binding of spermatozoa to oviductal sperm reservior
carbohydrate recognition is the mechanism, oviductal mucosa protects spermatozoa against aging and damage
release from the oviductal sperm reservoir
a change in the sperm surface, rather a change in oviductal epithelium
-only hyperactivated spermatozoa can detach
what process is reversible and which is not
capacitation id not fully reversible
hyperactivation is reversible
what is capacitation
set of changes in the sperm plasma membrane that enables a cell to acquire fertilizing potential/ undergo acrosome reaction
what does capacitation require
requires the removal of seminal fluid (has decapacitating activity)
how is capacitation asynchronous and continuous
only a percentage of spermatozoa are capacitated and those are continuously replaced
how long does the capacitated state lasts how long
50-240 minutes, post capacitated cells die unless they undergo acrosome reaction
how is capacitation initiated
initiated in the cervix by seminal plasma removal, completed in the isthmus during detachment from sperm reservoir by female-derived factors
which factors during capacitation are not species specific
female factors
explain the process of capacitation
-the plasma membrane of epididymal spermatozoa contains a complement of surface molecules (proteins and carbs) are attached to the head of the sperm (epididymal +seminal plasma)
-the surface molecules in epididymal sperm becomes coated with seminal plasma proteins that mask portions of the membrane molecules
(Ejaculated +female tract)
-When sperm are exposed to the female repro tract environment, these seminal plasma coating along with some surface molecules are removed, this exposing portions of the molecules that can bind to the zona pellucida of the oocyte
(capacitated)
what are some of the sperm changes after capacitation
-cholesterol increase
-acrosome is altered
-increase in intracellular calcium and levels of PH
-tyrosine phosphorylation
what do we need both of so that the sperm can be released from the oviductal sperm reservoir
both capacitation and hyperactivation
describe the process of hyperactivation
-increase in the flagellar bend amplitude and asymmetry lateral head displacement (tail movement is bigger and faster)
-enhances release from sperm reservoir, progressive motility and sperm penetration of cumulus ECM
-is accompanied by calcium oscillations in sperm head and midpiece, regulated by CAMP
-reversible process
what is the start of oocyte transport
capture by the infundibulum fasclitated by expanded cumulus fimbria and mesosalpinx contractions
what is oocyte transport facilitated by
oviductal muscle contractions (low amplitude and high frequency during estrus)
-cilia =: FACILITATE TRASNPORT (back and forth movement)
describe what happens when the penis becomes erect
when erotogenic stimuli are present the NANC neurons fire and release nitric oxide from their terminals.
-when NO is released it activates an enzyme called guanylate cyclase. This enzyme convertrs GTP to CGMP and causes the smooth muscle of the corporal sinusoids to relax (vasodilation)
the sinusoids engorge with blood and intracorporal pressures increases.
GTP–NO acting on guanylate cyclase—–cGMP sinusoid smooth muscle relaxes = erection
cGMP—-PDEs—–GMP (sildenafil blocks the action of PDE)
describe the day length/ hormone dependence for the ovary
Day 1: Estrogen (LH surge)
-cilia beat moves egg to AIJ against flow of secretion
-counter current of secretion is more effective than cilia
Day 3: Progesterone
-more cilia beat
-less secretion in isthmus
-embryo should be able to pass
how long is the embryo in the oviduct till
day 4
when does the control of ovum transport start
occurs under estrogen dominance
describe the control of ovum transport
distal isthmus and uterus are richly supplied with sympathetic nerves
-both A(stimulating) and B(inhibiting) adrenergic receptors are present
what enhances the activity of alpha receptors
estrogen= contraction of the isthmus
what enhances the activity of B receptors
progesterone= relaxation of the isthmus to allow embryo transport into the uterus
what drives sperm-oocyte recognition
chemotaxis: sperm recognizes the egg
thermotaxis: 2 degree Celsius difference between isthmus and ampulla
exposure to what alters sperm motility
cumulus cells
when do spermatozoa acquire chemotactic responsiveness
during capacitation
what is the overview of gamete transport part 1
- deposition of spermatozoa and sperm protective seminal plasma
- acquisition of motility and rapid swimming through cervix
- sperm movement through uterine cavity assisted by muscle contraction
- slowing of the sperm in uterotubal junction or isthmus
what is the overview of gamete transport part 2
- binding to oviductal epithelium sperm reservoir
- capacitation, hyperactivation and sperm release induced by ovulation
- oocyte picked by cilia on fimbria, moved down ampula by cilia and contractions
- fertilization occurs in ampullary-isthmic junction
what does sulfomucin corresponds to
high viscosity and washes sperm out
-from apical portions of cervical mucosa
what does sialomucin corresponds to
low viscosity and helps movement
-inside with the basal cells/ crypts
