# cervix anatomy > The cervix is made up of the ectocervix and endocervix and is on average 3 – 4 cm long and 2.5 cm wide (Pardo et al., 2003; Mazouni et al., 2005; Robert et al., 2013). The ectocervix is the portion of the cervix projecting into the vagina.[[(Martyn et al, 2014)#^irhsy]] > The opening of the ectocervix to the vagina is called the external os. Although studies of cervical length in non-pregnant women are few, it is acknowledged that the size and shape of both the cervix and the external os differ in women (Pardo et al., 2003; Mazouni et al., 2005) and vary with age, hormonal changes, parity and surgical treatments to the cervix.[[(Martyn et al, 2014)#^kmlw3]] > The cervix is a firm, cylindrical structure situated at the lower pole of the uterine corpus. The length of a normal adult non-pregnant cervix is approximately 25 mm, with an anteroposterior diameter ranging between 20 and 25 mm and a transverse diameter of 25e30 mm, although considerable variations occur due to age, parity and stage of menstrual cycle [3e5]. The cervix is divided into two portions that lie above and below the vaginal reflection, the portio supravaginalis and portio vaginalis respectively. Outside of pregnancy the cervical canal is collapsed, firm, and fusiform in shape. It ensures communication between the cavity of the corpus and the lumen of the vagina, and is bounded by the internal and external o[[(Nott et al, 2016)#^pchiz]]