Vagina

The vagina is the elasto-muscular component of the female genital tract in mammals. You might wonder where is the vagina located, it runs from the vulva to the cervix in humans. A membrane called the hymen covers the external vaginal opening in most cases. The cervix (uterine neck) curves into the vagina at the deep end. The vaginal canal allows for sexual activity and childbirth. It also regulates menstrual discharge (menses), which is a normal part of the monthly menstrual period in humans and highly associated primates.

Although there is a scarcity of research on the vagina science and vaginal cavity in various creatures, its position, composition, and size have been reported to differ between organisms, which is known from vagina description. The urethral opening for the urinary tract and the vaginal opening in the vaginal cavity for the genital tract are typically found in the vulva of female mammals. Male mammals, on the other hand, typically have a single urethral opening for both urine production and reproduction. In humans, the vaginal opening is much wider than the urethral opening surrounding, and both are covered by the labia.

The cloaca is the single external opening for the gastrointestinal, urinary, and reproductive tracts in amphibians, reptiles, mammals, and monotremes.

Structure

Gross Anatomy: The human vaginal canal runs from the vulva to the cervix and is made up of elastic and muscular tissue. The urogenital triangle is where the vaginal opening is located. The urogenital triangle includes the urethral opening and related portions of the external genitalia, as well as the front triangle of the perineum. Between both the urethra in the front and the rectum in the back, the vaginal canal travels upwards and backwards. The cervix protrudes into the vagina on the front surface at around a 90-degree angle near the upper vagina. The labia close the vaginal and urethral openings.

Vaginal Opening and Hymen: The vaginal opening in the vagina system is located behind the urethral opening at the back end of the vulvar vestibule. The labia minora (vaginal lips) usually cover the opening to the vagina, but it may be revealed after vaginal delivery.

The hymen is a tissue layer that covers or surrounds the vaginal opening. Intercourse and childbirth have varying effects on the hymen. It may fully vanish where it is split, or traces known as carunculae myrtiformes may remain. It can, however, return to its original position due to its high elasticity. Any  Disease, accident, medical examination, masturbation, or physical exercise may also lacerate the hymen.

Variations and Size: Women of childbearing age have different vaginal lengths. There is a variation in length between the front and back walls of the vagina due to the existence of the cervix at the front of the wall. The front wall is around 7.5 cm (2.5 to 3 in) long, while the back wall is approximately 9 cm (3.5 in) long. The vagina increases in length and width while sexual arousal. When a woman stands up straight, the vagina system points upward and backward, forming a 45-degree angle with the uterus. The vaginal opening and hymen are both different sizes; in girls, the hymen is usually crescent-shaped, but it may be any shape.

Development: The vaginal plate is the vagina's forerunner. The vaginal plate develops where the fused edges of the paramesonephric ducts join the back wall of the urogenital sinus as the sinus tubercle while development. The plate divides the cervix from the urogenital sinus as it develops, and the central cells of the plate gradually split down to create the vaginal lumen. This typically happens between the twenty-fourth and twenty-fifth weeks of growth. Membranes identified as vaginal septae may develop across or even around the tract if the lumen doesn't form or is incomplete, obstructing the outflow tract later on in life.

Microanatomy: From the lumen outwards, the vaginal wall is made up of a mucosa dreamed up of stratified squamous epithelium which is not keratinized, with just a lamina propria (a thin layer of connective tissue) beneath it. Second, there's a surface of smooth muscle with circular fibre bundles running parallel to longitudinal fibres (those that run lengthwise).

Finally, the adventitia is an external connective tissue layer. Most texts list the two sublayers of the mucosa (epithelium and lamina propria) separately to arrive at four layers.

The smooth muscular layer inside the vagina has a mild contractive force that may trigger certain pressure in the vaginal lumen; somewhat stronger contractive pressure comes from muscles in the pelvic floor that are connected to the adventitia across the vagina, such as throughout childbirth.

Blood and Nerve Supply: The vaginal artery, which arises from a branch including its internal iliac artery or the uterine artery, is the primary blood supply to the vagina. The vaginal arteries anastomose (join) with the cervical branch of the uterine artery along the side of the vagina, forming the azygos artery, which runs across the middle of the anterior and posterior vagina.

The middle rectal artery and the internal pudendal artery, both branches of the internal iliac artery, supply the vaginal region.

Such arteries are accompanied by three classes of lymphatic vessels: the upper group follows the uterine artery's vaginal branches; the middle group comprises the vaginal arteries; as well as the lower group drains lymph from the region beyond the hymen to the inguinal lymph nodes.

Ninety-five per cent of the vaginal lymphatic channels are all within three millimetres of the vaginal surface.

What are the Functions of the Vagina?

Below mentioned are the functions of the vagina:-

Secretions- The uterus, cervix, and vaginal epithelium produce the majority of vaginal secretions, with the Bartholin's glands providing minuscule vaginal lubrication throughout sexual arousal. A small amount of vaginal secretion is required to keep the vagina moist; secretions can rise during sexual arousal, throughout or just before menstruation, or even during pregnancy. The daily bleeding and mucosal tissue (recognized as menses) from the internal wall of the womb through the vaginal canal is known as menstruation. The composition and thickness of the vaginal mucous membrane change mostly during the menstrual cycle, which is a normal, natural shift in the female reproductive system (primarily the uterus and ovaries) that allows for pregnancy.

Sexual Activity: When the vaginal nerve endings are stimulated during sexual intercourse, they can produce pleasurable sensations. Women can enjoy one part of the vaginal canal or the sensation of closeness and fullness experienced during vaginal penetration. Since the vaginal nerve endings are sparse, women often do not receive enough sexual pleasure, or orgasm, from vaginal penetration alone.

Childbirth: The vaginal birth canal is where a baby is delivered. Vaginal discharge and membrane break (water breaking), which might lead to a gush of amniotic fluid or an abnormal or irregular stream of fluid from the vagina, are two signals that labour (a physiological phase preceding delivery) is approaching. Water breaks more often during childbirth, but it may also happen before labour (recognised as premature rupture of membranes), which occurs in 10% of cases.

Vaginal Microbiota: From birth to menopause, the vaginal flora is a dynamic ecosystem that evolves. The vaginal microbiota lives in and on the vaginal epithelium's outermost sheet. This microbiome is made up of species and genera that rarely cause illness or infections in women with healthy immune systems. Lactobacillus species control the vaginal microbiome.