Vagina: Structure, Functions, Anatomy & Diseases

Vagina is a muscular and elastic canal that is a part of the female genital tract and is lined with nerves and mucus membranes. It connects the cervix and uterus to the outside of the body, thus, allowing various processes such as menstruation, childbirth and intercourse. In mammals, the vagina is the elasto-muscular portion of the female genital canal. The vagina goes from the vulva to the cervix in humans, and you might be wondering where it is. The exterior vaginal entrance is usually covered by a membrane called the hymen. At the deep end of the vaginal canal, the cervix (uterine neck) curls into the vagina. Sexual activity and delivery are both possible in the vaginal canal. Menstrual discharge (menses) is a typical feature of the monthly menstrual cycle in humans and closely related primates.

Key Terms: Vagina, Artery, Female Genital Organ, Vulva, Cervix, Hymen, Menstruation, Uterus, Sexual Intercourse, Childbirth 

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What is Vagina?

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The vagina is a tubular organ that runs horizontally for 15 to 20 cm from the external part of the cervix to the transverse fold overlaying the external urethral orifice into the pelvic cavity. This transverse flap is typically maintained on each side of the vagina in maiden mares, forming the hymen. The hymen can sometimes fully ring the vestibulovaginal junction and become imperforate, making breeding impossible unless it is removed. The vestibule extends the vagina caudally. When the vagina is relaxed, it is a fibromuscular, compressed tube. The vaginal lateral walls are stiffer than the anterior and posterior walls. As a result, the middle region of the vagina has an H-shaped cross-section. 

The vaginal length and shape differ from woman to woman, with an average length of 6.3 cm. The vagina is placed anterior to the rectum and anus, posterior to the urinary bladder and urethra, and laterally to the ureter and uterine artery in the female pelvis. In regard to the perineum, it is at a 45-degree angle, and it is at a 90-degree angle in reference to the uterus.

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Structure of Vagina

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Although there is a scarcity of studies on the vagina in different animals, its location, structure, and size have been observed to differ between species. The urethral aperture for the urine system and the vaginal opening for the genital tract are the two external openings in the vulva of female animals. Male animals, on the other hand, often have a single urethral entrance for both urination and reproduction. In humans, the vaginal entrance is substantially bigger than the urethral hole adjacent, and both are covered by the labia. The cloaca is the only external entrance for the gastrointestinal, urinary, and reproductive systems of amphibians, birds, reptiles, and monotremes.

Also Read: Female Reproductive System

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What are the Functions of Vagina?

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The following are the functions of the vaginal canal:-

• Secretions

 The bulk of vaginal secretions are produced by the uterus, cervix, and vaginal epithelium, with the Bartholin's glands contributing tiny vaginal lubrication during sexual stimulation. To maintain the vagina moist, a little quantity of vaginal secretion is necessary; secretions might rise during sexual desire, during or immediately before menstruation, or even during pregnancy. Menstruation is the passage of blood and mucosal tissue (known as menses) from the inside wall of the womb via the vaginal canal on a regular basis. The vaginal mucous membrane changes in composition and thickness largely throughout the menstrual cycle allowing for conception.

• Sexual Activity

When the vagina is stimulated during sexual activity, nerve endings in the vagina can give pleasurable feelings. Women may like one area of the vaginal canal or the sensation of closeness and fullness experienced during vaginal penetration. Because the vaginal nerve endings are few, women typically do not get enough sexual excitement, or orgasm, through vaginal penetration alone. Childbirth pain is much more manageable since there are fewer nerve endings in the vaginal area. The G-spot is a possible erogenous zone in the vaginal region. It is often characterised as being positioned at the anterior wall of the vagina, a couple or few inches in from the entrance, and when this area is stimulated during sexual activity, some women experience extreme pleasure, and occasionally an orgasm. 

Some doctors and researchers believe that female ejaculation is caused by a G-spot orgasm, leading them to believe that G-spot pleasure comes from the Skene's glands, a female equivalent of the prostate, rather than any specific spot on the vaginal wall; however, other researchers believe the link between the Skene's glands and the G-spot area is weak.

• Childbirth 

A baby is born through the vaginal birth canal. Vaginal discharge and membrane rupture (water breaking), which can result in a burst of amniotic fluid or an aberrant or irregular stream of fluid from the vagina, are two signs that labour (the physiological period before birth) is coming. Although water breaks more frequently during childbirth, it can also happen before labour (known as the preterm rupture of membranes), which happens in 10% of cases.

• Vaginal Microbiota 

The vaginal flora is a dynamic ecosystem that changes from birth through menopause. The vaginal microbiota dwells in and on the outermost sheet of the vaginal epithelium. In women with sound immune systems, this microbiome is made up of species and genera that seldom cause disease or infections. The vaginal microbiota is governed by Lactobacillus species.

Also Read: Birth Control

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Anatomy of Vagina

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The vagina is a fibromuscular tube with anterior and posterior walls that are generally folded and in touch. The vagina does not have a spherical tube form. It looks more like an "H" lying on its side in the transverse plane. The cervix is surrounded by the vagina at its upper end, thus, forming two domes (fornices or vaults): an anterior and a (deeper) posterior one. The posterior fornix functions as a natural store for semen after intravaginal ejaculation. In the following 20-30 minutes, the semen is trapped in the fornix liquefies, allowing for easier penetration via the cervical canal.

Anatomy of Human Vagina

• Opening of the Vagina

The entry into the vagina, also known as the vaginal vestibule or introitus, is the vaginal opening. The anus is placed between the urethra and the urethra. Menstrual blood exits the body through this hole. It's also utilised to give birth and for sexual activity.

• Wall of the Vagina

The vaginal wall is comparable to the tissue in your mouth in that it is made up of muscle coated with mucous membrane. Layers of tissue with numerous elastic fibres make up the wall. Rugae, which are folds of additional tissue that allow the vagina to expand during sex or birthing, are also seen on the surface of the wall.

During the menstrual cycle, the tissues of the vaginal wall undergo hormonal changes. Glycogen is stored in the cells of the tissue's outer layer. This layer is lost during ovulation. Bacteria break down the glycogen, which serves to maintain a pH level in the vagina to protect it from potentially hazardous bacteria and fungus.

• Hymen

The hymen is a thin membrane that encircles the vaginal entrance. Hymens come in a variety of shapes and sizes, although the majority are half-moon shaped. Menstrual blood can exit the vaginal canal thanks to its form.

The hymen may rip when someone has their first intercourse or puts anything into the vaginal canal. This can also happen while you're doing a lot of activity.

Menstrual flow, tampon use, and intercourse can all be hampered by certain hymen forms and kinds. 

• Microanatomy

The vaginal wall is made up of a mucosa composed of stratified squamous epithelium that is not keratinized, with only a lamina propria beneath it, from the lumen outwards. Second, smooth muscle has a surface with circular fibre bundles that run parallel to longitudinal fibres. Finally, the adventitia is a connective tissue layer that is found on the outside of the body. 

To arrive at four layers, most texts list the two sublayers of the mucosa (epithelium and lamina propria) separately. The smooth muscular layer inside the vagina has a minor contractive force that can cause pressure in the vaginal lumen; somewhat stronger contractive pressure occurs from muscles in the pelvic floor related to the adventitia across the vagina, such as during birthing.

• Blood and Nerve Supply

The vaginal artery, which arises from a branch of the internal iliac artery or the uterine artery, supplies blood to the vagina. The vaginal arteries anastomose (connect) with the cervical branch of the uterine artery along the wall 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, also supply the vagina. 

These arteries are accompanied by three groups of lymphatic vessels: the top group follows the uterine artery's vaginal branches; the middle group accompanies the vaginal arteries, and the bottom group drains lymph from the region outside the hymen to the inguinal lymph nodes. Ninety-five per cent of the vaginal lymphatic tubes are within three millimetres of the vaginal surface. The sympathetic and parasympathetic portions of the pelvic plexus supply the nerve supply for the upper vagina and the pudendal nerve supplies the lower vagina.

Also Read: Reproductive Health

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Common Diseases of Vagina

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Some of the most common diseases associated with the Vagina are as follows: 

• Vaginitis

It is a vaginal irritation causing discomfort. A shift in the balance of vaginal flora or infection is the most common cause. Vaginitis can be caused by low oestrogen levels after menopause, as well as various skin conditions.

The following are the most prevalent kinds of vaginitis:

• Vaginosis is caused by bacteria- This is caused by an overpopulation of bacteria occurring naturally in your vagina, which throws off the natural equilibrium.
• Infections caused by yeast- Candida albicans, a naturally occurring fungus, is the most common cause.
• Trichomoniasis- This is caused by a parasite and is commonly transferred sexually.

• Vaginismus

Vaginismus is a condition in which the vaginal muscles tighten involuntarily. Penetration is unpleasant, if not impossible, due to muscular spasms. It usually starts when someone tries to have intercourse for the first time.

There is no one cause, however prior sexual trauma or emotional elements are frequently implicated. Fear of painful sex caused by vaginismus can cause muscles to tense, even more, causing additional discomfort.

• Vaginal atrophy 

It is a condition in which the uterus shrinks. The tissues of the vagina shrink and are thin as a result of vaginal atrophy, narrowing the canal and reducing its flexibility. During menopause, it's more prevalent. Estrogen production decreases during menopause, lowering vaginal fluids and interfering with vaginal pH.

Other reasons for low oestrogen, including nursing, ovary removal, and some drugs, might induce atrophy early in life. Vaginal dryness, painful intercourse, and itching are all possible side effects.

• Vaginal Prolapse

When the vaginal wall stretches or expands, it protrudes onto other organs, causing vaginal prolapse. It's uncommon for it to be limited to the vaginal area. During straining, the tissue that supports the uterus normally extends as well, weakening it.

Menopause, vaginal delivery, and recurrent abdominal pressure from obesity or straining bowel motions can all raise the risk of prolapse.

• Vaginal Cancer

Vaginal cancer is quite rare, according to reliable sources. Vaginal cancer can take several forms, but the most prevalent is squamous cell carcinoma, which begins in the vaginal lining. It may not create any symptoms in the early stages. However, if it spreads, it can result in atypical vaginal bleeding, discharge, or a mass in the vaginal canal.

The human papillomavirus is responsible for two-thirds of vaginal malignancies (HPV). Vaginal cancer is frequently treatable if detected early.

• Chlamydia

Young ladies are the most common victims of chlamydia. The majority of people who develop chlamydia have no symptoms, but those who do may have abnormal vaginal discharge and discomfort while peeing. The rectum can be affected by chlamydia, resulting in discharge, bleeding, and rectal pain.

Female Reproductive System

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Things to Remember

• The vagina is placed in front of the rectum and behind the bladder in humans, and it is around 9 cm (3.5 inches) long on average. 
• The uterus's cervix is connected to the upper portion of the vagina. The top and lower ends of the vaginal channel are the narrowest. 
• The external opening to the vagina is partially closed in most virgins by a thin fold of tissue called the hymen. The labia majora partially covers the aperture (vaginal orifice).
• The hymen is a thin tissue membrane that surrounds the vaginal opening and narrows it. It can be ripped or ruptured as a result of sexual activity or physical exertion.
• The vaginal canal is a soft, flexible tube with an elastic, muscular lining that gives lubrication and feeling and connects the uterus to the rest of the body. The vulva and labia form the entrance, while the inner end is formed by the uterus's cervix protruding into the vagina.
• During sexual intercourse, the vagina receives the penis and also functions as a channel for menstrual flow from the uterus. The infant goes through the vaginal canal during birthing (birth canal).
• Herpes simplex virus (HSV) infects the vulva, vagina, and cervix, creating tiny, painful blisters and ulcers that repeat. It's also typical to have no symptoms at all. The virus is spread through sexual contact. It is treatable but not curable.

Also Read: Male and Female Reproductive Organs