Explain the external and internal structure of the uterus.

(N/A) $\Rightarrow$ The uterus is a single organ,also known as the womb.
$\Rightarrow$ The shape of the uterus is like an inverted pear.
- It is supported by ligaments attached to the pelvic wall.
- The uterus opens into the vagina through a narrow cervix. The cavity of the cervix is called the cervical canal,which,along with the vagina,forms the birth canal.
- Wall of the uterus: The wall of the uterus consists of three layers of tissue:
$1$. Perimetrium: The external thin membranous layer.
$2$. Myometrium: The middle thick layer of smooth muscle.
$3$. Endometrium: The inner glandular layer that lines the uterine cavity.
- The endometrium undergoes cyclical changes during the menstrual cycle,while the myometrium exhibits strong contractions during the delivery of the baby.