Vulval vestibule

The vulval vestibule, also known as the vestibule of the vagina, is a part of the female external genitalia located within the vulva. It is the area enclosed by the labia minora and serves as the entrance to both the vagina and the urethra. The vestibule contains the openings of several important structures, including the vaginal orifice (introitus), the external urethral orifice, and the ducts of the Bartholin’s and Skene’s glands, which secrete lubricating fluids.

Location

The vulval vestibule is located within the vulva, between the labia minora. It lies just below the clitoral glans and extends to the posterior fourchette, surrounding the openings of the urethra and vagina. This area is bordered by the labia minora on both sides and is considered part of the external female genitalia.

Structure and Anatomy

The vulval vestibule is a key component of the female external genitalia, with several significant anatomical structures located within it. Below is a detailed description of the various elements of the vulval vestibule, including its boundaries, openings, and associated glands.

General Structure

The vulval vestibule is the area of the vulva located within the labia minora and forms the entrance to the vagina and urethra. It is a relatively small, shallow depression that acts as a passageway to the internal genital organs. The vestibule is lined with mucosal tissue, which is similar in texture to the lining of the vaginal walls, allowing for moisture and flexibility.

Shape and Texture: The vestibule is a roughly oval-shaped space, covered in soft, moist mucosa that helps maintain hydration and protects the underlying structures. It is a smooth area, sometimes slightly raised due to the underlying glands and tissues.

Boundaries of the Vulval Vestibule

The vestibule is defined by specific anatomical landmarks within the vulva, which help delineate its borders.

Labia Minora

The labia minora are two small, thin folds of skin that form the inner lips of the vulva and directly surround the vestibule. These folds extend from the clitoris at the top of the vulva to the posterior end of the vestibule. They provide the lateral boundaries for the vestibule and help protect the sensitive tissues inside.

Clitoral Hood and Glans

At the top of the vestibule is the clitoral hood and the clitoral glans, which form the anterior border of the vestibule. While the clitoris itself is not part of the vestibule, it plays a significant role in the overall structure of the vulva and is situated just above the urethral opening.

Posterior Fourchette

The posterior boundary of the vestibule is defined by the posterior fourchette, a thin fold of skin where the labia minora meet at the back of the vulva. This structure is located near the perineum and serves as the lower limit of the vestibule.

Openings in the Vulval Vestibule

The vulval vestibule contains several openings that lead to important internal structures, including the urethra, vagina, and glands.

Vaginal Orifice (Introitus)

• The vaginal orifice, also known as the introitus, is the primary opening of the vagina, located near the center of the vestibule. This is the largest opening within the vestibule and serves as the entrance to the vaginal canal.
• Hymen: In some women, the vaginal orifice is partially covered by the hymen, a thin membrane that can vary in size and shape. The hymen is located just inside the vaginal opening and may stretch or tear during physical activities or sexual intercourse.

Urethral Opening (External Urethral Meatus)

The urethral opening, or external urethral meatus, is located just above the vaginal orifice, closer to the clitoris. It is a small, slit-like or round opening through which urine is expelled from the body. The urethral opening is positioned in the anterior part of the vestibule, usually in close proximity to the clitoris.

Bartholin’s Gland Ducts

• The Bartholin’s glands, also known as the greater vestibular glands, are small glands located on either side of the vaginal orifice. The ducts of these glands open into the vestibule, providing lubrication to the vaginal entrance during sexual arousal.
• Location of Bartholin’s Ducts: The openings of these glands are situated near the posterior part of the vestibule, at approximately the 5 o’clock and 7 o’clock positions around the vaginal opening. These glands play an essential role in the lubrication of the vulva and vaginal area.

Skene’s Gland Ducts

• The Skene’s glands, also known as the paraurethral glands, are located near the urethra. These glands secrete fluids that help lubricate the urethral opening. The ducts of the Skene’s glands open into the vestibule near the external urethral meatus, contributing to the moist environment of the vulva.
• Location of Skene’s Ducts: The ducts are positioned on either side of the urethral opening, providing fluid that protects the urethral orifice and may also play a role in female ejaculation.

Mucosal Lining of the Vestibule

The vestibule is lined with mucosal tissue, which serves to protect the sensitive underlying structures and maintain a moist environment.

• Moisture and Lubrication: The mucosal lining of the vestibule is similar to the tissue found inside the mouth or the vagina. It secretes small amounts of moisture to keep the area lubricated, allowing for smooth functioning of the urethra and vaginal orifice.
• Sensory Receptors: The vestibular mucosa contains sensory receptors that contribute to the overall sexual response. While the vestibule itself is less sensitive than the clitoris, it still plays a role in sexual sensation, particularly during the arousal process.

Associated Muscles

The vestibule is surrounded by several muscles that contribute to its function and help maintain its structure.

Bulbospongiosus Muscle

The bulbospongiosus muscle surrounds the vestibule and plays a role in compressing the bulb of the vestibule, which is located on either side of the vaginal orifice. This muscle aids in increasing blood flow to the area during arousal and helps maintain the tightness and integrity of the vaginal entrance during sexual activity.

Perineal Muscles

The vestibule is also supported by the muscles of the perineum, including the superficial transverse perineal muscles. These muscles help anchor the posterior end of the vestibule and provide structural support to the vulva and vaginal opening.

Vascular Supply and Innervation

The vestibule has a rich blood supply and is innervated by several nerves that contribute to its function.

Blood Supply

The blood supply to the vestibule comes from the internal pudendal artery, which supplies the entire vulva and perineum. The arteries of the vestibule contribute to the engorgement of the surrounding tissues during sexual arousal, increasing sensitivity and lubrication.

Nerve Supply

The vestibule is innervated by branches of the pudendal nerve, which provides both sensory and autonomic innervation to the area. While the vestibule itself is less densely innervated than the clitoris, it still contains sensory receptors that contribute to sexual arousal and sensitivity.

Homology with Male Anatomy

The structures within the vulval vestibule have homologous counterparts in male anatomy, as both male and female genitalia develop from the same embryonic tissues.

• Bartholin’s Glands and Bulbourethral Glands: The Bartholin’s glands are homologous to the bulbourethral glands (Cowper’s glands) in males. Both types of glands produce lubricating fluids during sexual arousal.
• Skene’s Glands and Prostate: The Skene’s glands are homologous to the prostate in males. These glands secrete fluids that help maintain the health of the urethra and contribute to female sexual function.

Function

The vulval vestibule serves several important functions related to the female genital system, including acting as an entry point for the vagina, facilitating urination, providing lubrication, and contributing to sexual sensation. Below is a detailed description of the various functions of the vulval vestibule:

Entrance to the Vagina

The primary function of the vulval vestibule is to serve as the entry point to the vagina, connecting the external genitalia to the internal reproductive organs.

• Vaginal Orifice: The vaginal orifice, also known as the introitus, is located within the vestibule. This is the opening through which sexual intercourse occurs, menstrual blood exits the body, and babies pass during childbirth. The vestibule facilitates smooth access to the vaginal canal by serving as a pathway between the labia minora and the internal reproductive organs.
• Hymen: In some women, the vestibule contains remnants of the hymen, a thin membrane that partially covers the vaginal orifice. The hymen stretches or tears during sexual activity, tampon use, or physical exertion, allowing for vaginal access.

Passage for Urine

The vulval vestibule also functions as the exit point for urine, as it contains the urethral opening through which urine is expelled from the body.

• Urethral Orifice: The external urethral meatus is located within the vestibule, just above the vaginal opening. The urethra transports urine from the bladder and expels it through the meatus during urination. The positioning of the urethral opening within the vestibule allows for the efficient removal of urine from the body, preventing it from coming into contact with the vaginal orifice or surrounding areas.
• Separation of Functions: The close proximity of the vaginal orifice and the urethral opening within the vestibule allows for the separation of reproductive and urinary functions, while maintaining easy access to both.

Lubrication

The vulval vestibule plays an essential role in lubrication, particularly during sexual arousal, by housing the ducts of several glands that secrete fluids.

Bartholin’s Glands (Greater Vestibular Glands)

• Bartholin’s Glands, located on either side of the vaginal orifice, secrete a lubricating fluid that helps moisten the vaginal entrance during sexual arousal. The ducts of these glands open into the vestibule, allowing the fluid to coat the vaginal opening and the surrounding tissues.
• Lubrication for Intercourse: This secretion is important for reducing friction during sexual intercourse, making penetration more comfortable and minimizing the risk of irritation or injury.
• Response to Arousal: The Bartholin’s glands become more active during sexual arousal, increasing the amount of lubrication in response to heightened physical stimulation.

Skene’s Glands (Paraurethral Glands)

• The Skene’s glands, located near the urethral opening, also contribute to lubrication. These glands secrete fluid that helps keep the urethral opening moist, preventing irritation and infection. Their ducts open into the vestibule, allowing the fluid to flow onto the surrounding tissues.
• Moisture for Urethral Protection: The fluid produced by the Skene’s glands protects the urethral opening by maintaining a moist environment, which reduces the likelihood of dryness or irritation, particularly during sexual activity or urination.

Sexual Sensation

The vulval vestibule contributes to sexual sensation by containing sensory receptors and interacting with the surrounding erectile tissues.

• Sensory Receptors in the Vestibule: While the vestibule itself is less sensitive than the clitoris, it still contains sensory receptors within its mucosal lining. These receptors respond to touch and pressure, providing additional sensation during sexual arousal or stimulation of the external genitalia.
• Interaction with the Clitoris and Labia Minora: The vestibule is closely associated with the clitoris and labia minora, which are highly sensitive structures. During sexual arousal, the clitoris becomes engorged, and the labia minora swell slightly, increasing blood flow and heightening sensitivity in the vestibular area. As a result, stimulation of the vestibule can enhance overall sexual pleasure.
• Bulbospongiosus Muscle Contraction: The vestibule is surrounded by the bulbospongiosus muscle, which helps compress the bulb of the vestibule during sexual arousal. This compression increases blood flow and contributes to the sensation of fullness and sensitivity in the vulvar area, further enhancing sexual pleasure.

Support of Reproductive Health

The vulval vestibule plays an important role in maintaining reproductive health by providing a protective barrier between the external environment and the internal reproductive organs.

• Moisture Regulation: The mucosal lining of the vestibule helps maintain moisture in the vaginal and urethral areas, which is essential for preventing infections and irritation. By keeping the tissue hydrated, the vestibule promotes a healthy environment for both sexual and urinary functions.
• Protection Against Infections: The vestibule’s location at the entrance of the vaginal and urethral orifices provides a degree of protection against external pathogens. The secretions from the Bartholin’s and Skene’s glands help flush out bacteria and reduce the risk of infections, such as urinary tract infections (UTIs) or vaginal infections.
• Defense Mechanisms: The vestibule, through its mucosal lining and associated glands, forms part of the body’s first line of defense against pathogens. The acidic environment of the vagina, along with the fluids secreted into the vestibule, creates conditions that are less favorable for the growth of harmful bacteria.

Interaction with Muscles

The vestibule works in conjunction with the muscles surrounding the external genitalia to aid in both sexual and urinary function.

• Bulbospongiosus Muscle: The bulbospongiosus muscle, which surrounds the vestibule, contracts during sexual arousal and orgasm. This contraction helps compress the bulb of the vestibule and contributes to the sensation of fullness and rhythmic contractions experienced during orgasm.
• Pelvic Floor Muscles: The muscles of the pelvic floor support the external genitalia, including the vestibule. These muscles help maintain the structure of the vulva and provide the necessary support for both sexual function and urinary control.

Contribution to the Sexual Response Cycle

The vulval vestibule contributes to the sexual response cycle, particularly during the stages of arousal and orgasm.

• Arousal Phase: During sexual arousal, the glands within the vestibule, particularly the Bartholin’s and Skene’s glands, increase their secretion of lubricating fluids. The increased blood flow to the clitoris and labia minora also enhances sensitivity in the vestibule, preparing the body for sexual activity.
• Orgasm Phase: The vestibule plays a role in orgasm through the contraction of surrounding muscles, particularly the bulbospongiosus muscle. These contractions help intensify the sensations experienced during orgasm and contribute to the overall sexual response.

Clinical Significance

The vulval vestibule plays a crucial role in sexual, urinary, and reproductive health, and its clinical significance lies in several areas:

• Vestibulitis (Vulvar Vestibulitis Syndrome): This is a condition where the vestibule becomes inflamed and painful, often causing discomfort during sexual intercourse (dyspareunia), tampon use, or even during routine activities. Vestibulitis can lead to chronic pain and is often a part of vulvodynia, a broader condition involving vulvar pain.
• Infections: The vulval vestibule is susceptible to infections, such as yeast infections, bacterial vaginosis, or Bartholin’s gland cysts. Infections in the vestibule can cause inflammation, swelling, and discomfort, particularly around the vaginal and urethral openings.
• Urinary Tract Infections (UTIs): Due to the proximity of the urethral opening to the vaginal entrance, bacteria can easily enter the urinary tract through the vestibule, leading to UTIs. Proper hygiene and hydration are important in minimizing the risk of infection.
• Bartholin’s Gland Dysfunction: Blockages in the Bartholin’s gland ducts within the vestibule can lead to the formation of cysts or abscesses, causing pain, swelling, and discomfort. In some cases, surgical drainage may be required.
• Sexual Health and Arousal: The vestibule contributes to sexual sensation and arousal. Dysfunction or pain in this area can impact sexual health, leading to reduced pleasure or discomfort during sexual activity.