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Organ system histology
Cervix and vagina histology
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The cervix is the lower, cylindrical part of the uterus that opens into the vagina. Histologically the cervix is different from the rest of the uterus and also has a mucosa that doesn’t shed during menstruation. The cervical mucosa can be separated into three distinct regions: the endocervix, transformation zone, and ectocervix, which is also called the exocervix. The endocervical mucosa forms the wall of the cervical canal and will have a mucus-secreting simple columnar epithelium. The ectocervical mucosa is present in the part of the cervix that protrudes into the upper vagina and surrounds the external os, which is the lower opening of the uterus. This mucosa will have a non-keratinized stratified squamous epithelium that’s continuous with the vagina. The transformation zone is the region between the endo- and ectocervix. There’s an abrupt change from columnar cells to squamous cells within the transformation zone called the squamocolumnar junction. The exact location of the squamocolumnar junction will change or shift depending on the age of the individual as well as changes in the size of the uterus during menstruation. The transformation zone is also the ideal site to collect cells from during a Pap smear or Pap test. Underneath all regions of the cervical mucosa is a thick cervical wall that consists of dense connective tissue. Unlike the uterus, it only has a small amount of smooth muscle present.
The cervix is a short, cylindrical neck of tissue that connects the uterus to the vagina. The cervical mucosa has three visibly distinct zones: The endocervix: made of the simple columnar epithelium. The ectocervix: made of a non-keratinized stratified squamous epithelium. The transformation zone: has both squamous and columnar cells.
The vagina is a tube of muscle that leads from the cervix to the outside of the body. The wall consists of three main layers: the inner mucosa, the muscular, and the adventitia. The inner mucosa has a non-keratinized stratified squamous epithelium that keeps it moist and protects it from infection.
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