What Type of Tissue Is Responsible for Contractions?

Type of Tissue

• Muscular tissue like the myometrium is a type of tissue responsible for movement in the body. When a part of the body needs to move, like the uterus does to deliver a baby, the muscle tissue contracts. The myometrium is a smooth muscle tissue, which means it cannot move on command; it is involuntary. This means that you are not consciously in control of its functioning. The myometrium functions autonomously during labor, as it begins to contract--similar to your intestines digesting your food without your conscious input. Once the myometrium begins contracting in labor, you are unable to stop this process, because it is working of its accord.

Features of Myometrium Tissue

• The myometrium forms the middle layer of the uterine wall; it is the bulkiest part of the organ. It has a firm and dense texture, comprising smooth muscle fibers, which move and stretch easily. The muscle tissue contains blood vessels and lymph vessels. It also contains nerve endings that are responsible for the sensations a woman feels during a contraction, much like the nerve endings in your hands let you know when you are touching something hot.

What Causes Myometrium to Contract

• When a woman reaches full term in her pregnancy, the pituitary gland, a pea-sized organ in the brain, triggers, releasing a hormone called oxytocin. This hormone then sends a signal to the muscle tissue (myometrium) of the uterus to begin contracting to ease the baby downwards and out through the birth canal. The medical field has not established what causes the pituitary gland to trigger the production of oxytocin, so you cannot precisely predict when the myometrium will begin contracting.

What Happens in a Contraction

• When the myometrium tissue contracts, it causes the top of the uterus, called the fundus, to tighten and thicken, while stretching and opening the lower part of the organ, including the cervix. Over time this process will enable the cervix to loosen and dilate to 10cm wide, which will allow the baby to pass through the cervix and out though the vagina. At the beginning of labor, contractions will be erratic and last for short bursts of time, but as your labor advances the surges will become more regular and longer lasting, until you are ready to push the baby out.

What a Contraction Feels Like

• When the myometrium contracts it will make your abdomen feel tight, similar to the sensation of a cramp in your leg. The contraction will increase with intensity, moving like a wave around your back and abdomen and peaking in the middle of the contraction, then slowly subsiding until the next one happens. Women have likened contractions at the beginning of labor to menstrual cramps or trapped gas; as labor progresses, these sensations will become stronger and more intense.