Female External Genitalia

The female reproductive system includes organs involved in menstruation, sexual activity, fertilization, pregnancy, and childbirth. It is categorized as follows:

• External Genitalia: Vulva
• Internal Genitalia: Vagina, uterus, cervix, fallopian tubes, and ovaries
• Accessory Reproductive Organs: Mammary glands

1.0Development of Female Genitalia 

• The development of the genital duct system and external genitalia is driven by hormones present in the fetus. In male fetuses, Sertoli cells in the testes produce a nonsteroidal hormone called Müllerian-inhibiting substance (MIS), which leads to the regression of the Müllerian ducts. 
• Additionally, androgens from the fetal testes cause the external genitalia to develop into a male phenotype. Without MIS, the Müllerian ducts develop, and the mesonephric (Wolffian) duct system regresses. 
• Without androgen influence, the external genitalia differentiate into a female phenotype.
• The Müllerian duct forms between the fifth and sixth weeks of gestation, lateral to the intermediate cell mass and the Wolffian duct. The Müllerian duct has three main sections:

1. The cranial vertical portion opens into the coelomic cavity and later develops into the fallopian tubes.

2. The horizontal portion crosses the mesonephric duct.

3. The caudal vertical portion fuses with its counterpart from the opposite side, eventually forming the uterus, cervix, and the upper third of the vagina.

• The dorsal coelomic epithelium, which forms the Müllerian duct, remains open at its origin site, ultimately giving rise to the fimbriated ends of the fallopian tubes. 
• At the point of origin, each Müllerian duct forms a solid bud, penetrating the mesenchyme lateral and parallel to the Wolffian duct. 
• As these buds elongate, a lumen develops in the cranial part, beginning at each coelomic opening. 
• The caudal ends of the Müllerian ducts cross the ventral aspect of the Wolffian duct, with the most cranial portions eventually forming the fallopian tubes.

2.0Development of External Genitalia

• During the third week of development, mesenchymal cells migrate around the cloacal membrane, creating a pair of slightly elevated cloacal folds. 
• By the fourth to fifth week of gestation, these cloacal folds unite anteriorly to form the genital tubercle. Caudally, the cloacal folds differentiate into urethral folds (anteriorly) and anal folds (posteriorly).
• In female development, the genital tubercle elongates slightly to form the clitoris, and the urethral folds do not fuse as they do in males. Instead, they develop into the labia minora. The genital swellings enlarge and form the labia majora. 
• The urogenital membrane breaks apart to expose the lower part of the urogenital sinus or groove. This urogenital groove then opens centrally, giving rise to the vestibule, urethra, and the lower one-third of the vagina.

Anatomy of the female External genitalia vulva

Perineum 

The arrangement of the superficial and deep fasciae in the urogenital region creates two distinct triangular spaces: the superficial and deep perineal spaces.

Superficial Perineal Space 

• This area, located just above the perineal membrane (also known as the urogenital diaphragm), is referred to as the superficial compartment of the perineum. 
• The perineal membrane constitutes the lower part of the anterior pelvic floor; it is a triangular sheet of dense fibromuscular tissue that covers the anterior half of the pelvic outlet.
• The superficial compartment of the perineum contains several key structures, including:
• Colles fascia
• The clitoris and its crura
• Ischiocavernosus muscle
• Bulbocavernosus muscle
• Greater vestibular glands
• Superficial transverse perineal muscles

Deep Perineal Space 

• This space is located deep in the perineal membrane and contains the following structures:
• Deep perineal muscle
• Compressor urethrae muscle
• Urethrovaginal sphincter

Perineal Body

• Within the region bounded by the lower vagina, perineal skin, and anus lies a mass of connective tissue known as the perineal body, or central tendon of the perineum. 
• This structure is anchored to the inferior pubic rami and ischial tuberosities through the perineal membrane and the superficial transverse perineal muscles. 
• At its lateral edges, the upper portions of the perineal body connect with some fibers of the pelvic diaphragm. 
• Posteriorly, the perineal body is indirectly linked to the coccyx via the external anal sphincter, which is embedded within the perineal body. 

3.0Lower Genital Tract - External Genitalia

Vulva (Pudendum) 

• The female external genitalia, collectively known as the vulva, encompass several structures: the mons pubis, labia majora, labia minora, clitoris, vestibule, vestibular bulbs, and the greater vestibular glands.

Mons Pubis

• The mons pubis is the rounded area of skin located over the pubic symphysis and adjacent pubic bone, and it is covered with hair. 
• Before puberty, the mons pubis is relatively flat, and the labia minora are not well-defined. 
• During adolescence, coarse hair develops on the mons and labia majora, while the labia minora become more prominent and flap-like. 
• In adult females, the mons pubis is covered by coarse hair, extending to a horizontal boundary. After menopause, the pubic hair thins, and the labial tissue undergoes slight atrophy.

Labia Majora 

• The labia majora are two prominent, longitudinal folds of skin that extend from the mons pubis to the perineum, forming the lateral boundaries of the vulva. 
• Each labium features an external surface that is pigmented and covered with hair, while its internal surface is smooth, pink, and dotted with large sebaceous follicles.

Labia Minora 

• The labia minora are two small, flat folds of skin located between the labia majora. Unlike the labia majora, they lack fat and are lined with non-keratinized squamous epithelium. 
• They contain elastic tissue, veins, some smooth muscle, and numerous nerve endings. These folds extend obliquely from the clitoris, running laterally and posteriorly alongside the vaginal opening. 
• Anteriorly, each labium minus divides into two parts: the upper part forms a fold known as the clitoral hood or prepuce, which covers the glans of the clitoris. In contrast, the lower part creates the frenulum of the clitoris. 
• Posteriorly, the labia minora meet in the midline to form a thin ridge of skin called the fourchette.

Vestibule 

• The vestibule is the space located between the labia minora. 
• It houses the vaginal and external urethral openings, as well as the openings of the two greater vestibular (Bartholin's) glands and several mucous-secreting lesser vestibular glands.

Urethra 

• The urethra opens into the vestibule approximately 2.5 cm below the clitoris and above the vaginal opening. 
• It does so through a short, vertical slit with slightly elevated edges called the urethral meatus. On either side of the urethra's lateral margins, the ducts of the paraurethral glands (also known as Skene's glands) open into the vestibule.

Vaginal Orifice 

• The vaginal orifice is positioned at the posterior end of the vestibule, behind the urethral opening. 
• It is partially covered by a mucous membrane called the hymen, which acts as a septum.

Greater Vestibular Glands (Bartholin’s Glands) 

• The greater vestibular glands, also known as Bartholin's glands, are the female counterparts of the male bulbourethral glands. 
• They are two small, round or oval, reddish-yellow structures located on either side of the vaginal orifice, approximately at the 4 o'clock and 8 o'clock positions, beneath the bulbospongiosus muscle. 
• Each gland has a duct, about 2 cm long, which opens into the posterior part of the vestibule, in the groove between the hymen and the labia minora, just outside the hymenal ring. 
• These glands are composed of tubuloacinar tissue, with columnar cells that produce an alkaline, clear or whitish mucus that serves a lubricating function. The secretion is stimulated by sexual arousal. 
• The duct is lined with columnar epithelium, transitioning to stratified squamous epithelium near its opening. 
• If a Bartholin's gland becomes blocked and filled with secretions, it can form a Bartholin's gland cyst. If this cyst becomes infected and inflamed, it results in a painful condition known as a Bartholin's abscess.

Bulbs of the Vestibule 

• The bulbs of the vestibule are elongated masses of erectile tissue, each about 3 cm long, located on either side of the vestibule. They flank the vaginal orifice and join anteriorly via a narrow commissural bulborum (pars intermedia). 
• These structures are homologous to the bulb of the penis in males, though they are bilaterally split in females. If the posterior ends of the vestibular bulbs are damaged during labor, it can lead to severe bleeding.

Clitoris 

• The clitoris is an erectile organ partially covered by the anterior bifurcated ends of the labia minora. It consists of three main parts: the root, the body, and the glans. The body, which can be felt through the skin, contains two corpora cavernosa made of erectile tissue encased in dense fibrous tissue. 
• The glans clitoris is a small, rounded tubercle of spongy erectile tissue located at the tip of the body and connected to the bulbs of the vestibule by slender bands of erectile tissue. 
• It is visible between the anterior ends of the labia minora and features highly sensitive epithelial tissue, which plays a crucial role in sexual arousal and response.