The cervical stroma is composed mainly of collagen, elastin, and proteoglycans, but very little smooth muscle. As described in Chapter 21 (p. 409), changes in the amount, composition, and orientation of these components lead to cervical ripening prior to labor onset. In early pregnancy, increased vascularity within the cervix stroma beneath the epithelium creates an ectocervical blue tint that is characteristic of Chadwick sign. Cervical edema leads to softening-Goodell sign, whereas isthmic softening is Hegar sign.
Most of the uterus is composed of myometrium, which contains smooth muscle bundles united by connective tissue with many elastic fibers. Interlacing myometrial ibers surround myometrial vessels and contract to compress these. This anatomy allows hemostasis at the placental site during the third stage of labor.
he number of myometrial muscle ibers varies by location (Schwalm, 1966). Levels progressively diminish caudally such that, in the cervix, muscle makes up only 10 percent of the tissue mass. The uterine body's inner wall has relatively more muscle than its outer layers. And, in the anterior and posterior walls, the muscle content is greater than in the lateral walls. During pregnancy, the upper myometrium undergoes marked hypertrophy, but cervical muscle content does not change significantly.
The uterine cavity is lined with endometrium, which is composed of an overlying epithelium, invaginating glands, and a supportive, vascular stroma. As discussed in Chapter 5 (p. 83), the endometrium varies greatly throughout the menstrual cycle. This layer is divided into a functionalis layer, which is sloughed with menses, and a basalis layer, which serves to regenerate the functionalis layer following each menses. During pregnancy, the endometrium is termed decidua and undergoes dramatic hormonally driven alterations.
Several ligaments extend from the uterine surface toward the pelvic sidewalls and include the round, broad, cardinal, and uterosacral ligaments (Figs. 2-10 and 2-11) . Despite their appellation, the round and broad ligaments provide no substantial uterine support, which contrasts with the cardinal and uterosacral ligaments.
he round ligament originates somewhat below and anterior to the origin of the fallopian tubes. Clinically, this orientation can aid fallopian tube identification during puerperal sterilization.
External iliac a. & v.
Lateral vaginal sulcus Adventitial layer of anterior vaginal wall Rectum
FIGURE 2-1 1 Pelvic viscera and their connective tissue support. (Reproduced with permission from Corton MM: Anatomy. In Hoffman BL, Schorge JO, Bradshaw KD, et al (eds): Williams Gynecology, 3rd ed. New York, McGraw-Hili Education, 2016.) his is important if pelvic adhesions limit tubal mobility and thus, hinder fimbria visualization and tubal confirmation prior to ligation. Each round ligament extends laterally and down into the inguinal canal, through which it passes, to terminate in the upper portion of the ipsilateral labium majus. Sampson artery, a branch of the uterine artery, runs within this ligament. In nonpregnant women, the round ligament varies from 3 to 5 mm in diameter and is composed of smooth muscle bundles separated by ibrous tissue septa (Mahran, 1965). During pregnancy, these ligaments undergo considerable hypertrophy and increase appreciably in both length and diameter.