THE CERVIX

THE CERVIX

�CERVIX / NECK OF THE UTERUS�

• Although the cervix is part of the uterus, structure and function differ from the main body of the uterus.

SITUATION

• It forms the lower 1/3 of the uterus and is the area below the isthmus which includes the internal and external os.
• It enters the vagina at right angle.

SHAPE

• The cervical canal is fusiform and the cervix as a whole is Barrel shaped.

SIZE OF CERVIX

• It is 2.5cm long in adult. It becomes bigger in pregnancy and at times at birth it becomes almost equal size with the uterus.

GROSS STRUCTURE

• Supravaginal cervix – this is the portion that lies outside and above the vagina.
• Superiorly, it meets the border of the uterus at the isthmus.
• The infravaginal cervix – the portion which projects into the vagina.

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IMAGE

INTERNAL OS

• It opens into the cavity of the uterus . It dilates during labour.
• Incontinence is due to anomaly of the cervix or dilatation of the cervix during dilatation and curettage.

THE EXTERNAL OS

• It opens into the vagina at the lower end of the cervical canal.
• On pelvic examination it is found at the upper border of the symphysis pubis.

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THE EXTERNAL OS CONT’D

• On vagina examination it is circular in shape, smooth and with a dimple in the centre but after 36^th week of pregnancy the dimple will admit a tip of finger.
• In multigravida it is a transverse, slit like and admit a finger tip. It is known as multip’s Os.

THE CERVICAL CANAL

• It lies between the internal and external os.

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�MICROSCOPIC STRUCTURE�

• There are three layers of tissues.
• ENDOMETRIUM
• This is the inner layer contains many racemose glands that secrete mucus.
• The ciliated epithelium tissue facilitates the passage of spermatozoa.
• The tissue is arranged in folds called arbor vitae.
• The folds allows dilatation of the cervix during labour.

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2. MUSCLES

• Involuntary muscle fibres are mingled with dense collagenous tissue which gives the cervix a fibrous nature.
• Longitudinal fibres from the uterus pass into the cervix.
• There are also spiral fibers running clockwise and anticlockwise lying in circular fashion.
• The muscle fibers increase during pregnancy.

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3.PERITONEUM

• It covers the part that lies above the vagina and loosely applied in the area where it reflects up and over the bladder. This allows the bladder and uterus to adjust their position as required.
• Infravaginal cervix has an outer coat of stratified epithelium.
• The stratified epithelium continues a short distance into the cervical canal meet the cervical endometrium at squamocolumnar junction (the commonest site of cervical cancer)

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• BLOOD SUPPLY- Uterine arteries and drain by uterine veins�
• LYMPHATIC DRAINAGE- Into the internal iliac and sacral glands.

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• NERVE SUPPLY- Symphathetic and parasymphathetic nerves from lee frankenhause (sacral)plexus.

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SUPPORTS

1.Transverse cervical ligaments- Extend from the cervix to the lateral walls of the pelvis.

2. Pubocervical ligaments- Runs forwards from the cervix to the pubic bones.

3. Uterosacral ligaments- Extends from the cervix and pass backwards to the sacrum.

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RELATIONS

• ANTERIORLY- Uterocervical pouch of perineum and bladder.
• POSTERIORLY- The pouch of Douglas and rectum.
• LATERALLY- The broad ligaments and ureters.

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FUNCTIONS

• It helps to prevents infection entering the uterus.

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• It dilates and withdraws during labour to enable vaginal delivery of the fetus and placenta.

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• Following delivery, the cervix returns almost to its non pregnant state.

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�CHANGES� IN THE CERVIX DURING PREGNANCY�

• The cervix remains 2.5cm long throughout pregnancy but the action of the hormone oestrogen causes it to increase in width and the vascularity also increase which gives it a purplish or bluish colour.(Jacquemiers sign).
• Pulsation is felt at the lateral fornices of the vagina called Osainders sign.
• There is also proliferation of the gland which secret mucus. This mucus fills the cervical canal and prevent the entry of bacterial into the uterus.

CONT’D

• This mucous plug the canal and it is known as operculunm.This process is under the influence of the hormone progesterone.
• Prostaglandin from the cervical tissues soften the cervix from the third mouth onwards till delivery.
• Towards the end of pregnancy part of the cervix incorporate into the lower uterine segment therefore shorten the cervix.
• At term, the external Os of the cervix opens to admit the tip of the finger and this is called ripe cervix.

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��COMPLICATIONS OF THE CERVIX DURING PREGNANCY��

• Incompetent cervix – Shirodkar operation is done.
• Cervical erosions – it clear spontaneously.
• Cervical polyps-no treatment is carried out during pregnancy.
• Congenital abnormalities
• Carcinoma of the cervix

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ANY QUESTIONS?

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THE END

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