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Cervical Softening - Anatomy & Physiology (view source)
Revision as of 22:39, 6 August 2011
, 22:39, 6 August 2011→Cervical Softening
In ruminants the cervical mucus is expelled from the vagina during oestrous and is known as 'bulling string'. Bulling string therefore indicates that animal is in oestrous and should be mated.
In ruminants the cervical mucus is expelled from the vagina during oestrous and is known as 'bulling string'. Bulling string therefore indicates that animal is in oestrous and should be mated.
==Cervical Softening==
==Cervical Softening==
A number of variables during pregnancy lead to the initiation of contractions of the myometrium including oxytocin, prostaglandins and neural inputs from the autonomic nervous system. These contractions of the myometrium lead to an increased pressure within the amniotic fluid. These contractions trigger a series of events that lead to the cervix becoming flexible and gradually beginning to dilate. As the force of the contractions increases, the cervix will open completely. Much of the activity related to the initiation of contractions is initiated by fetal stress resulting in an increased production of fetal cortisol. The effects listed below are all linked to the initial increase in fetal cortisol in some way.
===Endocrinology===
===Endocrinology===
Immediately prior to birth, the pre-parturition cervix looses firmness. Cervical softening involves two changes in the intracellular matrix; firstly a reduction in the number of collagen fibres and secondly an increase in GAGs to decrease aggregation of the remaining collagen fibres.
Immediately prior to birth, the pre-parturition cervix loses firmness. Cervical softening involves two changes in the intracellular matrix; firstly a reduction in the number of collagen fibres and secondly an increase in GAGs to decrease aggregation of the remaining collagen fibres.
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Relaxin is produced by the ovaries and the placenta and together with progesterone prevent uterine contractions throughout the pregnancy. However, relaxin also aids in the loosening of tissues in the cervix and pelvic ligaments to loosen pre-parturition. Relaxin and PGE2 work in combination on the cervix.
Relaxin is produced by the ovaries and the placenta and together with progesterone prevent uterine contractions throughout the pregnancy. However, relaxin also aids in the loosening of tissues in the cervix and pelvic ligaments to loosen pre-parturition. Relaxin and PGE2 work in combination on the cervix.
===Progesterone Production===
===Progesterone Production===
The initiation of myometrial contractions via fetal cortisol results in cells within the uterus and the placenta undergoing a degree of stretch. This stretching is thought to activate several systems within the cells resulting in the production of progesterone. Stretching can increase the avaliability of cyclo-oxygenase 2 or COX-2 which is part of a chain of reactions converting arachadonic acid to PGE2 and PGF2α resulting in an increased cellular output. Both of these types of prostaglandin potentiate oxytocin once outside the cell and this inturn potentiates an increase in the level of arachadonic acid, thus scaling up production in the entire system. Secondly the stretching the cell also results in increased expression of oxytocin receptors in the cell surface resulting in a greater impact on the cell for a given level of oxytocin, further upregulating the system.
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Outside the cell levels of oestradiol are also increasing and this also has an impact on the systems behind the production of prostaglandins. Oestradiol increases the avaliability of COX-2 within the cell and also the expression of oxytocin receptors providing a further mechanism to increase the total prostaglandin output of the cell.
===Softening Mechanisms===
===Softening Mechanisms===