Changes

The [[Cervix - Anatomy & Physiology|cervix]] retains the foetus in the uterus. Connective tissue resists stretch, allowing distension of the [[Uterus - Anatomy & Physiology|uterine body]] whilst maintaining the cervix in a closed state.  For the foetus to move out of the uterus, the cervix must soften or 'ripen'.

The basic function of the [[Cervix - Anatomy & Physiology|cervix]] during pregnancy is to retain the foetus within the uterus and to maintain the internal environment of the uterus by preventing the external environment accessing the uterus. Therefore the cervix regulates the passage to and from the uterine cavity. This ensures that any micro-organisms within the external environment are unable to access the uterus. During pregnancy the [[Uterus - Anatomy & Physiology|uterine body]] becomes distended whilst stretch resistant tissues allow the cervix to be maintained in a closed state.  For the foetus to move out of the uterus, the cervix must soften or 'ripen'.

The texture of the cervical tissues is influenced by the relative levels of oestogen and progesterone and therefore is changable dependant on the stage of the 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 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 cervix is composed of:

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.

* '''Collagen fibre bundles''': helical strands of amino acids bound together to form fibrils

* '''Proteoglycan Matrix''': protein core with '''Glycosaminoglycan''' branches '''(GAGs)'''.  GAGs determine the degree of collagen fibre aggregation.  An increased GAG content reduces collagen aggregation and vice versa.

Immediately prior to birth, the pre-parturition cervix looses firmness.