The cervix is the ring of muscles also called the neck of the uterus in female reproductive system. This protrudes through the anterior wall of the vagina, opening into it at the external os.
After the fertilization of the ovum by the spermatozoa, the uterus prepares for the implantation which results from the secretion of hormones. Under the influence of oetrogen, secreted by the developing follicle, the cells of the endometrium divide rapidly causing the endometrium to build up and thicken.
While the viscosity of cervical mucus changes in response to hormone levels and during pregnancy, progesterone fosters the production of highly viscous mucus resulting in the formation of a plug that forms a physical barrier to bacteria and prevents their ascension into the uterine cavity. This plug is called CERVICAL PLUG.
The plug is formed as soon as there is implantation of fertilized eggs. The thickness of the cervical mucus becomes different as hormone levels changes in pregnancy.
The progesterone, encourages the production of thick fluid/ mucus which brings about the formation of a plug. This prevents bacteria from getting into the uterine cavity.
This model suggests that the cell membrane is a dynamic structure, because the proteins and phospholipids move laterally within the lipid bilayer ( so it is more of a fluid than solid)
Homologous structures are anatomical features in an organism that are structurally and functionally diverse but they originate from a single common ancestor.
Homologous structures possess a similar basic internal structure but can have entirely different morphology and function.
For example, the wings of a bat and a human's arm have the same internal structure but they have different functions.
Vestigial structures are evolutionary remnants that no longer serve a purpose in modern forms or descendants of the original organism.
Inherited and developmental are out of context in terms of evolutionary relationships.
