Changes

==Cervix Structure==

==Cervix Structure==

The cervix has only a small amount of musculature and is mainly composed of '''collagen fibre bundles''' and '''proteoglycan matrices'''. The collagen fibres are helical strands of amino acids bound together to form fibrils whilst the proteoglycan matrix are made up of a protein core with '''Glycosaminoglycan''' branches or '''GAGs'''. GAGs determine the degree of collagen fibre aggregation. An increased GAG content reduces collagen aggregation and vice versa.

The cervix has only a small amount of musculature and is mainly composed of '''collagen fibre bundles''' and '''proteoglycan matrices'''. The collagen fibres are helical strands of amino acids bound together to form fibrils whilst the proteoglycan matrix are made up of a protein core with '''glycosaminoglycan''' branches or '''GAGs'''. GAGs determine the degree of collagen fibre aggregation. An increased GAG content reduces collagen aggregation and vice versa.

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The texture of the cervical tissues is influenced by the relative levels of [[Sex_Hormones#Female_Sex_Hormones|oestrogen]] and [[Sex_Hormones#Female_Sex_Hormones|progesterone]] and therefore are changable dependant on the stage of the [[Oestrous_Cycle_-_Anatomy_%26_Physiology|oestrous cycle]]. The mucous membrane of the cervix is highly folded and contains mucin producing cells. Mucin production increases under the influence of oestradiol and helps to lubricate the vagina in preparation for copulation. Mucin is also responsible for the transport of bacteria and foreign bodies away from the uterus. During the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Luteal_Phase|luteal phase]] and during pregnancy small levels of mucin are produced under the influence of progesterone to help form a 'cervical plug'. This plug ensures that the external environment is unable to penetrate the uterus.  

The texture of the cervical tissues is influenced by the relative levels of [[Sex_Hormones#Female_Sex_Hormones|oestrogen]] and [[Sex_Hormones#Female_Sex_Hormones|progesterone]] and therefore are changable dependant on the stage of the [[Oestrous Cycle - Anatomy & Physiology|oestrous cycle]]. The mucous membrane of the cervix is highly folded and contains mucin producing cells. Mucin production increases under the influence of oestradiol and helps to lubricate the vagina in preparation for copulation. Mucin is also responsible for the transport of bacteria and foreign bodies away from the uterus. During the [[Oestrous Cycle - Anatomy & Physiology#Luteal_Phase|luteal phase]] and during pregnancy small levels of mucin are produced under the influence of progesterone to help form a 'cervical plug'. This plug ensures that the external environment is unable to penetrate the uterus.  

===Cervical Species Differences===

===Cervical Species Differences===

In [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Cow|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. For further differences between species please see; [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Mare|mares]], [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Ewe|ewe]], [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Nanny_Goat|goat]], [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Sow|sow]], [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Bitch|bitch]] and the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Queen|queen]].

In [[Oestrous Cycle - Cattle|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. For further differences between species please see; [[Oestrous Cycle - Horse|mares]], [[Oestrous Cycle - Sheep|ewe]], [[Oestrous Cycle - Goat|goat]], [[Oestrous Cycle - Pig|sow]], [[Oestrous Cycle - Dog|bitch]] and the [[Oestrous Cycle - Cat|queen]].

==Cervical Softening==

==Cervical Softening==

A number of variables during pregnancy lead to the initiation of contractions of the [[Uterus_-_Anatomy_%26_Physiology#Myometrium|myometrium]] including oxytocin, [[Oestrous_Cycle_Pharmacological_Manipulation_-_Anatomy_%26_Physiology#Prostaglandins|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 begun 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.

A number of variables during pregnancy lead to the initiation of contractions of the [[Uterus - Anatomy & Physiology#Myometrium|myometrium]] including oxytocin, [[Oestrous Cycle Pharmacological Manipulation - Anatomy & Physiology#Prostaglandins|prostaglandins]] and neural inputs from the [[Autonomic Nervous System - Anatomy & Physiology|autonomic nervous system]]. These contractions of the myometrium lead to an increased pressure within the amniotic fluid and 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 begun 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 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.

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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Several hormones are known to exhibit an effect on the cervix resulting in pre-parturition softening; 'prostaglandins' and [[Ovaries_Endocrine_Function_-_Anatomy_%26_Physiology|'relaxin']]. Prostaglandin levels increase markedly in the days prior to parturition, peaking at parturition. There are three main types and sources of prostaglandin that are important in cervical softening; prostaglandin E2 (PGE2), prostacyclin (PGI2) and Prostaglandin F2α (PGF2α).

[[Ovaries Endocrine Function - Anatomy & Physiology|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.  

 

[[Ovaries_Endocrine_Function_-_Anatomy_%26_Physiology|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 within 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.  

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 availability 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 in turn potentiates an increase in the level of arachidonic acid, thus scaling up production in the entire system. Secondly the stretching within 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.

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 availability 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===

It is thought that prostagladins together with relaxin may induce cervical softening by inducing collagen breakdown within the tissues and/or by altering the GAG/proteogylcan composition. Collagen breakdown within the tissue would facilitate a higher degree of movement and stretch in the tissue which is required for softening. Similarly an increase in the GAG content of the tissues stimulated by prostaglandin would result in a decrease in collagen fibril agglutination therefore reducing the stretch-resistance of the remaining collagen.

It is thought that prostagladins together with relaxin may induce cervical softening by inducing collagen breakdown within the tissues and/or by altering the GAG/proteogylcan composition. Collagen breakdown within the tissue would facilitate a higher degree of movement and stretch in the tissue which is required for softening. Similarly, an increase in the GAG content of the tissues stimulated by prostaglandin would result in a decrease in collagen fibril agglutination therefore reducing the stretch-resistance of the remaining collagen.

[[Category:Parturition]][[Category:To Do - Review]]

[[Category:Parturition]][[Category:A&P Done]]