Exam 5: Breeding Behavior, Early Pregnancy, and Maternal Recognition Flashcards
Describe the process of an erection
Arterial blood comes in and sinusoids fill
Venous outflow restricted by contraction of ischiocavernosis muscles
Pressure builds in corpus cavernosum
Retractor penis muscle relaxes
Erection and protrusion occur
What initiates the cascade leading to erectionl?
Nitric oxide
What control is the cascade leading to erection under?
Parasympathetic
What is ejaculation?
Propulsive discharge of semen from the penis
What causes ejaculation?
Stimulation of glans penis
What can the glans penis stimulation be duplicated with?
Artificial vagina
What control is ejaculation under?
Sympathetic
What do you get from ejaculation?
Rhythmic contraction of urethralis, bulbospongiousus, and ischiocavernosus muscle leading to wavelike expulsion
What occurs concurrently with ejaculation?
Emission
What is emission?
The fluid being released from the accessory sex glands
What is the duration of ram copulation?
1 to 2 seconds (1 pelvic thrust with foreleg clasp)
What is the volume of ram ejaculation?
0.8 to 1 mL
What is the duration of bull copulation?
1 to 3 seconds (1 pelvic thrust with foreleg clasp)
What is the volume of bull ejaculation?
3-5 mL
What is the duration of stallion copulation?
20-60 seconds (multiple pelvic thrusting, flagging of tail followed by inactive phase)
What is the volume of stallion ejaculation?
75-120 mL
What is the duration of boar copulation?
5 to 20 minutes (rapid pelvic thrusting to engage penis in cervix. When penis is engages thrusting stops and ejaculation commences accompanied by somnolence)
What is the volume of boar ejaculation?
200-250 mL
What contributes to the large volume of ejaculation in boars?
Accessory sex glands are large
What are the stages of breeding in dogs?
First stage coitus (1-2 min)
The turn (2-5 sec)
Second stage coitus (5-45 min)
What completes the “tying” in second stage coitus in dogs?
Bulbus glandis
What species use the cranial vagina as the site of semen deposition?
Bull Ram Buck Dog Tom
What species use the intra cervical as the site of semen deposition?
Boar
What species use the intra uterine as the site of semen deposition?
Stallion
Alpaca
What is used as the site of semen deposition in AI?
Intra uterine
What are the 3 stages of sperm transport?
Short, rapid sperm transport (2-10 minutes)
Colonization of reservoirs (cervix and UTJ)
Slow prolonged release of sperm cells
When does fertilization occur?
When a minimum number of sperm cells reach the site of fertilization
What does it mean when you say that sperm use the buddy system?
The depend on each other to get to the ovum even though only one will be successful
What plays a role in the transport of sperm cells?
Elevated tone and motility of female tract under the influence of estrogen
Prostaglandins in semen have a similar effect
What are the 2 phases in the transport of sperm cells?
Rapid phase
Sustained phase
Describe the rapid phase
Sperm reach oviduct in few minutes
Describe the sustained phase
Sperm reside at ostium and slowly enter oviduct
Sperm reservoir
Describe the colonization of reservoirs
Huge numbers of sperm are trapped in folds of the cervix
Cervical mucus directs sperm towards the cervical crypts where a reservoir is formed
What does a large reservoir mean?
More sperm are available to move towards oviduct for longer period of time
Where is the reservoir at for species that ejaculate into uterine horns?
UTJ
What happens to almost all sperm cells shortly after breeding?
They are lost
What percentage of sperm cells are lost after AI in cows?
60%
What percentage of sperm cells reach the site of fertilization?
0.007%
What removes many sperm cells after breeding?
Neutrophils
What is capacitation?
Final maturation process which allows sperm to fertilize the ovum
Where does capacitation occur?
Female reproductive tract
What does capacitation involve?
Both physiological and biochemical processes
What does sperm undergo in capacitation?
Changes that are required prior to penetration of the ovum
Phospholipid bilayer is altered permitting the acrosome reaction to occur
What happens in capacitation?
Seminal plasma coats the sperm with proteins that are stripped away when in the female tract
Sperm are now able to bind in the zona
What does capacitation prevent?
Premature acrosome activation until sperm are at the site of fertilization
Is capacitation reversible?
Yes
What does seminal plasma contain?
Decapacitation factor
What does the acrosome reaction occur in the presence of?
Oocytes
What is the acrosome reaction?
An orderly fusion of sperm’s plasma membrane and the outer acrosomal membrane
What does the acrosome reaction do?
Allows sperm to penetrate and digest its way through the zona of the oocyte
Exposes equatorial segment for later fusion with plasma membrane of oocyte
What are pre-requisites for oocyte penetration?
Capacitation and acrosome reaction
What is the oocyte activated by?
The fusion with the sperm
What happens after the acrosome reaction?
Meiosis that was arrested in metaphase II is resumed
What mediates polyspermy prevention?
Cortical granules
What happens if the fertilization of oocyte is done by more than one spem?
Leads to polyploid nucleus
Death
What are the 2 mechanisms of polyspermy prevention in order?
Zona block
Vitelline block
What happens in a zona block?
Zona undergoes biochemical changes that prevent other sperm from penetrating the zona
What does a vitelline block do?
Prevents oocyte plasma membrane from fusing with more sperm
What is syngamy?
Fusion of male and female pronuclei at time of fertilization
What is an embryo?
Organism in the early stages of development but cannot be distinguished
What is a fetus?
Developing offspring that is still within the uterus but is recognizable as a specific species
Describe maternal recognition
Luteolysis must be prevented for early embryo to survive
High progesterone levels must be maintained to maintain pregnancy
Conceptus must prevent luteolysis by signaling its presence in the uterus
What happens if the signal from the conceptus is inadequate of mistimed?
MRP will not occur and luteolysis will occur leading to pregnancy loss
What normally happens in an animal that is not pregnant?
There is no embryo
No maternal recognition of pregnancy factor
Oxytocin is released from CL
Binds oxytocin receptors on endometrium and stimulated PGF2α release
CL is lysed and new cycle begins
What happens in a pregnant ewe, doe, and cow?
Blastocyst produces interferon-τ from day 13-21 after ovulation
IFN-τ binds to endometrium and inhibits oxytocin receptor synthesis
PGF2α is dependent on a threshold number of oxytocin receptors being present
Pregnancy is maintained
What happens in a pregnant sow?
Conceptus produces estradiol as signal for MRP
E2 begins being produced at day 11
Causes PGF2α to be “rerouted” toward the uterine lumen
Luminal PGF2α has no access to circulation and thus cannot cause luteolysis
Must have at least 2 conceptuses in each horn for pregnancy to be maintained
What happens in a pregnant mare?
Presence of conceptus b/w days 12-14 prevents luteolysis
Conceptus must migrate often to signal its presence (remains spherical unlike ewe, cow, and sow)
Precise proteins are not yet known
What happens in a pregnant dog and cat?
Both have obligatory diestrus period after ovulation that last as long as or longer than gestation
CL of pregnancy and CL of normal cycle have similar lengths
This is why P4 has no use as a pregnancy test in dogs and cats
