This is our first article in the ‘What should one expect’ series. This series is aimed at helping patients, families as well as medical staff to get a wholesome picture of malignancies, right from Anatomy to management. This article focuses on anatomy of ca cervix.Lets divide the ca cervix section into two parts. First being the basic anatomy followed by pathology and management later on. I’ll try to keep it simple so that both, doctors and more importantly patients are able to grasp the basic concepts behind cervical cancer. So directly diving into the topic, lets first start with the anatomy.
Basic architecture of the cervix
Cervix is a cylinder shaped, firm structure located at the lower end of the uterus.
As we know every tissue is made up of cells and every hollow cavity or tract is lined by cells, that have particular functions such as protective function, lubricating function as well as immune function. Similarly, the cervix is also lined by cells, along its length. The cervical lining of cells is very oddly arranged, read further to understand how.
The outer aspects of the cervix that are exposed to the outside is covered in stratified squamous epithelium. This epithelium is arranged in layers and has a protective function. The inner aspect is lined by columnar cells which have a secretory function that helps in lubrication.
At the junction of these two cell linings is the squamo-columnar junction. The exact location of this junction keeps changing with hormonal and parity status of the woman.
In children the junction is located more towards the os, as puberty sets in the junction goes more outwards and in adult life the junction goes back towards the os. So basically, what happens here is that the columnar cells which was once within the cervical canal moves towards the outside and is later replaced by new squamous epithelium during adult life, due to which the junction goes back inwards towards the os.
The process by which the new squamous epithelium replaces the columnar epithelium is called ‘squamous metaplasia’.
Transformation zone as we can see in the diagram is the region that lies in between the original squamo-columnar junction and the new squamo-columnar junction, and it is this zone which gives rise to most cervical malignancies.
Now that we understood the basic structure of the cervix it is time to move ahead.
Cervix is surrounded by some important structures that play a role in staging in cervical cancer.
The parametrium is the fibrous and fatty connective tissue that surrounds the uterus and cervix and is covered by the broad ligament…Imagine throwing a sheet of cloth over furniture, similarly the peritoneum is like a sheet of cloth that is thrown over the uterus and its surrounding structures forming the broad ligament.
Position of ureters in relation with the uterus and cervix has its own importance as any obstruction in their path, maybe due to a malignancy can result in backflow of urine causing hydronephrosis, which is the swelling of the kidney due to build up of urine.
Ligaments involved in cervical cancer
Sometimes patients with cervical cancer may present with back pain….Why back pain in a cervical patient? The answer lies in the following few lines.
Ligament support of cervix— > Cardinal ligament- Extends from the cervix to the lateral pelvic wall.
Uterosacral ligament- extends from cervix to the sacrum…Involvement of this ligament by the tumour is responsible for back pain.
Blood supply of cervix
The main blood supply to the cervix is the cervico-vaginal branch, 91% of times this branch arises from the uterine artery at its point of intersection with the ureter and 9% of times this branch arises from the internal iliac artery.
This branch gives off branches that enter the cervix perpendicular to its wall and then divides itself into anterior and posterior arcuate arteries, which lie between outer third and middle third of the uterine muscle as shown in the diagram below. Posterior arcuate branch is generally wider.
The venous drainage runs along the arterial system, with communication between the cervical plexus and neck of the urinary bladder. The veins drain into the hypogastric venous plexus.
Nerve Supply of cervix
The cervix gets parasympathetic nerve supply from the inferior hypogastric plexus of nerves.
The sympathetic fibres originate from the lower thoracic spinal cord and passes through the inferior hypogastric plexus to the cervix. The parasympathetic fibres originate from S2-S4 segments of the spinal cord to the inferior hypogastric plexus and then towards the cervix.
Afferent fibres of the upper vagina and cervix travel back along the pelvic splanchnics (S2-S4) and to the pudendal nerve.
The Parasympathetic nerves serve in normal physiologic function such as cervical dilatation and secretion. The afferent fibres carry pain sensation through the pudendal nerve, hence the pudendal block given in order to reduce pain.
Lymphatic drainage of the cervix- An important concept in cervical cancer
The lymphatic drainage of cervix is divided into lateral , posterior and posterolateral.
The lateral aspect drains into the paracervical nodes, obturator nodes and external iliac nodes.
The Posterior aspect drains into the sacral nodes along the utero-sacral ligaments.
The posterolateral aspect drains into the internal iliac nodes. The internal and external iliac nodes further drain into the common iliac nodes and in turn into the paraaortic nodes. All lymph drained from the pelvic region is returned to the venous circulation via the thoracic duct, which empties its contents in or around the junction of the left internal jugular vein and subclavian vein.
Thats all you need to understand of cervical anatomy in order to get a grasp of further sections. Further in the ‘what should one expect’ series, we’ll give you a brief understanding about the pathology of cervical cancer.