Parturition

Parturition is the act of giving birth to a baby. It consists of many different stages which interact to provide delivery of child and the placenta.

Organs Involved

The primary organ involved is the uterus. This contains a layer known as the myometrium which contains bundles of non-striated (smooth) muscle as well as connective tissue (collagen), nerves and blood vessels. The muscles of the inner wall of the myometrium are circular, whereas the muscles on the outer wall are longitudinal. During pregnancy this layer increases in mass approximately 20 fold, with hypertrophy increasing from 50um to 500um, hyperplasia increasing and glycogen deposits increasing.

The muscle cells act as a syncytium, in which spontaneous depolarising pacemaker potentials occur. If these are above a certain threshold (known as the action potential) then a wave of calcium is released and a contraction occurs.