Surgical Anatomy Of Vulva And Perineum

The most significant anatomical areas in the female reproductive system are the vulva and perineum. Their structures and functions are different. The area beneath the vulva after the subcutaneous tissue is removed is referred to as the superficial perineal pouch.

The perineal membrane is a deeper membrane found in the superficial perineal pouch. The deep perineal pouch's structures are found deeper within this perineal membrane. The inferior border of the abdominopelvic cavity is formed by the pelvic diaphragm, a large yet thin layer of muscular tissue.

Perineum Boundaries

The perineum is a diamond-shaped region with the following boundaries, located between the vulva and the anus and enclosed by the bony pelvic outlet.  Anterior: pubic symphysis, or the front of the pelvic bone. Ischial tuberosities are the bony protrusions in the buttocks that are visible when sitting.

The sacrotuberous ligament is the ligament that runs from the sacrum to the ischial tuberosity.  Posterior: the coccyx, or tailbone.  Skin between the vulva and the anus inferior
The perineum is separated into two triangles and has a variety of structures:

Anterior triangle, also known as the urogenital triangle: The urethra and external genitalia are located at the front part of the perineum. Urination and sexual function depend on this region.

 Posterior triangle, also called the anal triangle: The anus and related structures are located in the back of the perineum. It has anal sphincters and aids in the process of feces.

Also Read: Oligohydramnios Its Causes And Management

Tissues Filling The Anterior Triangle 

1. Skin and subcutaneous tissue of the vulva
2. Superficial perineal pouch 
3. Deep perineal pouch

The clitoris and its crura, the vestibule bulb, Bartholin's gland, the ischiocavernosus and bulbospongiosus muscles, the superficial transverse perineal muscle, the branches of the pudendal arteries, and nerves are all found in the superficial perineal pouch.  The sphincter urethero vaginalis, compressor urethrae, external urethral sphincter, and perineal membrane are all located in the deep perineal pouch.

Vulva

The female's external genitalia, or vulva, consists of the following structures:

Mons Pubis: The adipose tissue that covers the pubic bone is known as the mons pubis. It acts as a cushion for protection and possesses hair.
Labia Majora: The vulva's outer "lips" are called labia majora. They are fatty, dense tissues that have sebaceous glands and sweat in them.  The posterior commissure is where the labia majora on either side unite.  The perineal body is the region between the anal and vaginal openings.

Labia Minora: The hairless, inner "lips" of the vulva are known as the labia minora. They enclose the urethral and vaginal openings and are more delicate and thinner than the labia majora.

The fourchette is the posterior place where the labialis minora connect from both sides. The clitoris is an extremely sensitive organ situated at the anterior junction of the labia minora. It shares similarities with the male penis in terms of erectile tissue and sexual sensitivity. It is composed of folds that unite to form frenulum below and perpuce of clitoris above.

COMPARISON BETWEEN LABIA MAJORA AND LABIA MINORA

The smoother, more glossy transitional look of the nonkeratinized stratified squamous epithelium is known as Hart's line.

Applied Anatomy

The anterior/upper boundary of the labia majora is where the uterine round ligament ends.  The obliterated vaginal process (canal of the nuck) may be a dilated embryonic remnant in the region of labia majora. This region gives birth to leiomyomas.
The illness known as hidradenitis suppurativa can result from a chronic infection of the apocrine sweat glands located in the labia majora. Hydradenomas are neoplastic enlargements of these apocrine glands.

Vestibule

The space bounded on both sides by the labia minora is known as the vestibule. The term "hymen" refers to the thin membrane covering the vaginal opening, which is lined by stratified squamous (non-keratinized) epithelium.  Fossa navicularis is the name for a little depression in the fossa.

True Virgin Vs. False Virgin

 Following childbirth, leftovers are referred to as Carunculae Myrtiformes.

Structures Opening Into The Vestibule 

On either side, it has the Bartholin's gland apertures in addition to the urethral and vaginal openings.  Both sides' ducts ascend superficially and open just beyond the hymen;  Skin's paraurethral glands open into the vestibule;  Bartholin's glands: these are tiny glands on either side of the vaginal entrance that release mucus for lubrication during sexual excitement.

Also Read: Vessels Of The Abdominal Wall

Bartholin’s Gland

This gland, also known as the Greater Vestibular Gland, is located in the superficial perineal pouch and is homologous to the male Cowper's glands. The duct's purpose is to exude alkaline mucus during coitus. It opens into the vestibule at the intersection of ⅔ and ⅓ posterior, directly outside the hymen.

Applied Anatomy 

 Debris collection can obstruct the opening of Bartholin's gland, causing cysts to form.  The position of the vulva's swelling indicates if the Bartholin's duct is enlarged or infected.
  Urethral diverticulum may result from Skene's gland inflammation or duct blockage.

Superficial Perineal Compartment

 It is the area between the perineal membrane and the superficial layer of the perineal muscles' investing fascia.

Clitoris

The vulva, or external genitalia of the female reproductive system, contains the highly sensitive and erogenous clitoris organ. The clitoris is one of the most sensitive regions of the body, with hundreds of nerve endings and an autonomic supply, making it the major female sex organ responsible for sexual pleasure. It also has clitoris glans and body.

The suspensory ligament of the clitoris suspends the body in the pubic symphysis. Clitoris glans are present at the tip of Clitoris.  The stratified squamous epithelium covering Glans is non-keratinized. In the clitoris, corpora cavernosa comprises the body.

The corpse of the cavernosa is separated into two wings-like appendages known as crura.  Ventricular bulbs are the venous aggregate of veins and the erection-promoting and vascular structure of the external female gentalia that fastens to the clitoris' body.  The clitoris deep artery supplies primarily the clitoris body and extends deep into the tunica albuginea layer.
The pudendal nerves branch off to supply the glans region through the dorsal artery nerve and the clitoris vein.

Contents Of Superficial Perineal Pouch

The area in the perineum between the genitalia anteriorly and the anus posteriorly in both sexes is anatomically known as the superficial perineal pouch, or superficial perineal compartment.
  The different structures seen in this pouch may differ slightly in males and females.

Ischiocavernosus muscle: it enters into the clitoris' crura after emerging from the ischial ramus and the medial portion of the ischial tuberosity, respectively.  Muscle of the bulbospongiosus: this muscle is clearly divided on both sides and originates from the perineal body. After that, fibers spread out to cover the larger vestibular glands and vestibular bulbs.

 Superficial transverse perineal muscle: The superficial transverse perineal muscle is a transverse strip of muscle that passes through the superficial perineal region in front of the anus.  If the ischiocavernosus muscle is eliminated, the crus of the clitoris is present on both sides; if the bulbospongiosus muscle is removed, vestibular bulbs are present.

It arises from the anterior and medial aspects of the ischial tuberosity and inserts at the perineal body.  The internal pudendal artery and vein, as well as the terminal branches of the pudendal nerve, serve the region behind Bartholin's duct.

 Compression of the clitoris crura results from contraction of the ischiocavernosus muscle. It enhances the sensation and arousal of sex.  The Bartholin gland secretion is released when the bulbospongiosus muscle contracts.  One factor contributing to clitoris' erectile dysfunction is vestibular bulbs.

Also Read: Surgical Anatomy Of Anterior Abdominal Wall

Perineal Membrane 

The perineal membrane joins medially to the vaginal entrance and the wall of the urethra, and it has a lateral attachment to the lateral ischiopubic rami beneath the ischiocavernosus muscle. The perineal membrane attaches to the arcuate ligament of the pubic symphysis anteriorly and alone to the perineal body posteriorly.

  The dorsal nerve of the clitoris runs deep to the perineum membrane, then perforates the perineal membrane, and eventually lies underneath the crus of the clitoris.  The pudendal nerve gives rise to a perineal branch that travels superficially to the perineal pouch. 

Structures Of The Deep Perineal Pouch

The deep perineal space, sometimes referred to as the deep perineal pouch, is an area in the pelvis that is home to a number of anatomical components, such as blood vessels, muscles, and nerves. It is made up of the pubococcygeus portion of the levator ani muscle and is situated in the perineum, which is the area between the pubic symphysis and the coccyx.

The muscular sheath originates from the ischiopubic rami and extends from both sides over the urethral aperture. It is composed of the fibers of the compressor urethral muscles, which are striated skeletal muscle. Compressor Urethrae Muscle: This muscle helps maintain urine continence by compressing the urethra (also known as the sphincter urethrae muscle in females).

The striated urogenital sphincter complex, which is made up of some smooth muscle fibers oriented transversely and another transversely placed skeletal muscle fiber on both sides mixed with perineal membrane, is the collective name for the fibers that make up the sphincter urethrovaginalis. Its function is to compress the lower part of the urethra.

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Perineal Body

Attachments

• Bulbospongiosus
• Superficial transverse perineal
• Fibers of external anal sphincter
• Perineal membrane 
• Fibers of pubococcygeus
• Ischiocavernosus muscle is laterally placed and not attached to the perineal body.

 In nulliparous women, the length of the perineal body ranges from 3.5 to 5 cm.  During pregnancy or the second stage of labor, the perineal body can expand by up to 65%.  The perineal body extends with repeated vaginal deliveries or childbirths, which may cause the vaginal lower wall to sink.
  During an episiotomy, a medial incision is made into the perineal body; this is the area that is torn during perineal tears.  During an episiotomy, the superficial transverse perineal, bulbospongiosus, and fourchettes are sliced.

Sensory Innervation Of Vulva 

The external female genitalia, or vulva, is extensively innervated to enable sensory awareness. Multiple nerves supply the vulva's sensory innervation. These comprise: the terminal branches of the pudendal nerves provide the majority of sensory innervation; the illioinguinal nerve and the genital branch of the genitofemoral nerves supply certain areas of the vulva anteriorly (the area of the mons pubis and ant. Labia majora); and the posterior cutaneous nerve of the thigh (branch of sacral plexus) supplies the area posteriorly inferior to the thigh.

Pudendal Nerve And Vessels 

The sacral plexus (S2, S3, and S4 roots) gives rise to the pudendal nerve, which is the primary sensory and motor nerve.  The anterior division of the internal iliac artery gives rise to the internal anterior pudendal artery.  The superficial external pudendal artery, a branch of the femoral artery, supplies blood to the region of the mons pubis.

The pudendal nerve is located directly medial to the ischial spine, behind the sacrospinous ligament.Subsequently, it proceeds into the Pudendal/Alcock's Canal before emerging into the perineum. It results in the formation of the perineal nerve, which contains numerous branches:  Muscular branch; Sensory branch to vestibule and bottom third vagina; Posterior labial branch . The perineal skin and external anal sphincter are supplied by the inferior rectal nerve.

Applied Anatomy 

Stretch injuries during childbirth and labor can be more likely due to the pudendal nerve, which is located behind the ischial spine and sacrospinous ligament. Fecal incontinence may result from injury to the inferior rectal nerve. The pudendal nerve block is situated just medial to the ischial spine and behind the sacrospinous ligament.

The distal extension of the inferior hypogastric plexus provides autonomic innervation to the corpora cavernosa of the clitoris. These fibers pass through the paravaginal and paraurethral connective tissue, under the pubic symphysis, and join the dorsal nerve of the clitoris. Damage to the inferior hypogastric plexus during extensive perineal surgeries may result in sexual dysfunction.

Lymphatic Drainage of the Vulva 

 One crucial component of the lymphatic system that aids in the removal of waste materials and extra fluid from the tissues in the vulvar region is the vulva's lymphatic drainage.The vulva's lymphatic drainage normally follows this pattern:  The thigh's fascia lata is the deep membranous layer of the fascia; • The subcutaneous fatty layer contains superficial inguinal lymph nodes. 

Vulvar drainage primarily occurs in the upper and medial quadrants, from the labia majora to ipsilateral side. • The saphenous vein empties into the femoral vein through a hole known as the saphenous opening, which is located above the fascia lata of the thigh.

Bilateral drainage occurs in the fourchette, 1 cm above midline tissues such as the clitoris; drainage proceeds to the deep inguinal lymph nodes, which are situated further into the femoral canal, following the superficial inguinal lymph nodes.Cloquet's lymph nodes, commonly known as the lymph node of Rosenmuller, are the most superior of these inguinal lymph nodes.

 The discharge proceeds to the pelvic lymph node from the deep inguinal lymph nodes.  Vulva cancer causes lymphatic dissemination to the inguinal femoral group of lymph nodes.
One side group of the inguinal lymph node will be affected when the malignancy affects the lateral side of the vulva.

Some clitoris lymph nodes may bypass this pathway and leak straight to the pelvic lymph node.  Both sides of the inguinal group will be impacted when vulva cancer affects the anterior half of the labia minora, clitoris, and fourchette (midline structures).

Important Questions

Q. What Are The Structures Present In The Superficial Perineal Pouch?

Ans:  The clitoris and its crura, a vestibule bulb, Bartholin's gland, ischiocavernosus and bulbospongiosus muscles, superficial transverse perineal muscle, branches of pudendal vessels, and nerves are all found in a superficial perineal pouch.

Q. Define Bulbospongiosus Muscle?

Ans The bulbospongiosus muscle, sometimes referred to as the bulbocavernosus muscle, is a muscle found in both male and female perineals. It serves distinct purposes for each gender and is a component of the pelvic floor musculature.

Q. Labia Majora Is Made Up Of Which Kind Of Tissues?

Ans: It is made up of keratinized, stratified squamous epithelium

Q. Sebaceous Glands Are Present In-

Ans: Labia majora

Q. Name The Location Where Hart’s Line Is Present-

Ans: Hart's line, which divides the anal canal into its upper two thirds and lower one third, is situated in the middle of the canal.

Q. Which Part Of The Vulva Leads To Leiomyomas?

Ans: The anterior/upper edge of the labia majora is where the uterine round ligament ends. This area is the source of leiomyomas.

Q. Define The Term “Hidradenitis suppurativa (HS)”

Ans: Acne inversa, orhidradenitis suppurativa, is a persistent skin illness that affects hair follicles in places of the body where skin rubs against skin, like the groin, buttocks, under the breasts, and under the armpits. The development of sore, inflammatory nodules, abscesses, and subcutaneous sinus tracts (tunnels) are indicative of HS.

Q. Which Part Of The Labia Majora Results In Hidradenitis Suppurativa?  

Ans: Hydradenitis suppurativa is a disorder caused by persistent infection of the apocrine sweat glands in the labia majora.

Q. Neoplastic Enlargement Of Apocrine Glands Will Lead To-

Ans: Hidradenomas

Q. Elaborate The Term “Carunculae Myrtiformes.”

Ans: Small, fleshy lumps or remnants known as carunculae myrtiformes are discovered near the vaginal introitus, or the female vagina's exterior opening. The posterior (back) fourchette of the vulva, or the place where the labia minora converge at the base of the vaginal entrance, is where these caruncles are located.

Q. What is the Function of Bartholin’s Gland?

Ans: The little glands known as Bartholin's Glands, which release mucus to lubricate the vaginal entrance during sexual stimulation, are located on either side of the opening.

Q. Which Gland is Called the Greater Vestibular Gland?

Ans:  Bartholin’s gland

Q. Cowper’s Glands in the Male is Homologous to-

Ans: Bartholin’s gland

Q. Inflammation/duct Obstruction of the Skene’s Gland Can Lead to-

Ans: Urethral diverticulum

Q. The Perineal Membrane Attaches Anteriorly to the-

Ans: Arcuate ligament of the pubic symphysis

Q. The Perineal Membrane Attaches Medially to the-

Ans:  Wall of the urethra and the vaginal opening

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