Vagina, Vulva, and Pelvic Floor: Anatomy

Development

Embryology timeline

• Weeks 1–6:
  • Embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week is sexually indifferent/nonbinary.
  • Embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week possesses the following primordial sexual organs:
    • Mesonephric ducts ( wolffian ducts Wolffian ducts A pair of excretory ducts of the middle kidneys of an embryo, also called mesonephric ducts. In higher vertebrates, wolffian ducts persist in the male forming vas deferens, but atrophy into vestigial structures in the female. Primary Amenorrhea)
    • Paramesonephric ducts (müllerian ducts)
    • Urogenital sinus Urogenital Sinus Congenital Malformations of the Female Reproductive System
    • Genital tubercle Genital Tubercle Development of the Urogenital System
    • Urogenital fold
    • Labioscrotal swelling Labioscrotal Swelling Congenital Malformations of the Female Reproductive System
• Week 7:
  • Sexual differentiation begins with the development of the gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types.
  • The genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure present at fertilization Fertilization To undergo fertilization, the sperm enters the uterus, travels towards the ampulla of the fallopian tube, and encounters the oocyte. The zona pellucida (the outer layer of the oocyte) deteriorates along with the zygote, which travels towards the uterus and eventually forms a blastocyst, allowing for implantation to occur. Fertilization and First Week determine if the developing, bipotent gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types differentiate into testes Testes Gonadal Hormones or ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy. 
  • The presence and/or absence of specific hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types secreted by the gonads Gonads The gamete-producing glands, ovary or testis. Hormones: Overview and Types determine how the remaining structures differentiate. 
• Week 20: Phenotypic differentiation is complete.

Female differentiation of the embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week

Male development is triggered by the presence of certain hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types; female development is triggered primarily by the absence of hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types.

• Male development is driven by 2 primary hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types produced in the testes Testes Gonadal Hormones:
  • Testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens: stimulates differentiation of the wolffian ducts Wolffian ducts A pair of excretory ducts of the middle kidneys of an embryo, also called mesonephric ducts. In higher vertebrates, wolffian ducts persist in the male forming vas deferens, but atrophy into vestigial structures in the female. Primary Amenorrhea into the male structures (e.g., epididymis Epididymis The convoluted cordlike structure attached to the posterior of the testis. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of spermatozoa. Testicles: Anatomy, vas deferens Vas Deferens The excretory duct of the testes that carries spermatozoa. It rises from the scrotum and joins the seminal vesicles to form the ejaculatory duct. Testicles: Anatomy, seminal vesicles Vesicles Female Genitourinary Examination, and ejaculatory ducts Ejaculatory Ducts Paired ducts in the human male through which semen is ejaculated into the urethra. )
  • Anti-Müllerian hormone ( AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea): causes degeneration of the müllerian ducts
• Developing ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries: Anatomy do not secrete testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens or AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea.
• In the absence of AMH AMH A glycoprotein that causes regression of mullerian ducts. It is produced by sertoli cells of the testes. In the absence of this hormone, the mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent mullerian duct, a form of male pseudohermaphroditism. Primary Amenorrhea, the paramesonephric/müllerian ducts persist to form the internal female sexual organs: 
  • Fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum’s final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes: Anatomy
  • Uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy
  • Upper ⅓ of the vagina 
• In the absence of testosterone Testosterone A potent androgenic steroid and major product secreted by the leydig cells of the testis. Its production is stimulated by luteinizing hormone from the pituitary gland. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to dihydrotestosterone or estradiol. Androgens and Antiandrogens:
  • Mesonephric/ wolffian ducts Wolffian ducts A pair of excretory ducts of the middle kidneys of an embryo, also called mesonephric ducts. In higher vertebrates, wolffian ducts persist in the male forming vas deferens, but atrophy into vestigial structures in the female. Primary Amenorrhea degenerate.
  • The urogenital sinus Urogenital Sinus Congenital Malformations of the Female Reproductive System, genital tubercle Genital Tubercle Development of the Urogenital System, folds, and swelling Swelling Inflammation differentiate into female external genitalia.
  • Note: All infants (male and female) are exposed to the mother’s high estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy levels in utero; therefore, the role estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy plays in female sexual development is unclear.
• Urogenital sinus Urogenital Sinus Congenital Malformations of the Female Reproductive System forms:
  • Lower ⅔ of the vagina 
  • Greater vestibular glands (also known as Bartholin glands)
  • Urethral and paraurethral glands (also known as Skene glands)
• Genital tubercle Genital Tubercle Development of the Urogenital System forms:
  • Glans clitoris
  • Vestibular bulbs
• Urogenital fold forms: labia minora
• Labioscrotal swelling Labioscrotal Swelling Congenital Malformations of the Female Reproductive System: labia majora

Gross Anatomy

Gross anatomy of the vagina

The vagina is the external entrance to the female reproductive tract.

• A fibromuscular tube connecting the vaginal vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy (between the labia minora) distally and the uterine cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy proximally
• Length: approximately 8–10 cm 
• Functions:
  • Discharge of menstrual fluid
  • Receipt of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy and semen
  • Delivery of an infant at the end of pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
• Fornix: 
  • The uppermost portion of the vagina (the annular Annular Dermatologic Examination recess between the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy and the vagina)
  • Can be divided into anterior, posterior, and lateral portions
• Hymen: 
  • Folds of vaginal mucosa stretching across the distal portion of the vaginal orifice
  • Embryologically, the hymen separates the urogenital sinus Urogenital Sinus Congenital Malformations of the Female Reproductive System and the vaginal lumen (usually ruptures before birth).
• Vaginal borders:
  •  Anterior: the urinary bladder Urinary Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters (ureter), and is held there until urination. Urinary Tract: Anatomy and urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy:
    • The urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy is embedded in the anterior wall.
    • The urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy drains the urinary bladder Urinary Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters (ureter), and is held there until urination. Urinary Tract: Anatomy (coursing parallel to the vagina prior to termination at the urethral orifice in the vaginal vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy).
  • Posterior: the anal canal and rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy
  • Lateral: the muscles of the pelvic floor and ischial bones
  • Superior: the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy
  • Inferior: the vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy

Gross anatomy of the vulva

The vulva refers to the external female genitalia and occupies most of the perineum.

• Borders of the vulva: 
  • Anterior: pubic symphysis
  • Posterior: perineum and anal orifice
  • Lateral: upper medial thighs
  • Superior: muscles of the pelvic diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy
• Mons pubis: hair-bearing region of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and adipose tissue Adipose tissue Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or “brite” adipose tissue, which is a transitional form. Adipose Tissue: Histology over the pubic symphysis
• Labia majora: 
  • Paired prominent longitudinal cutaneous folds containing adipose tissue Adipose tissue Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or “brite” adipose tissue, which is a transitional form. Adipose Tissue: Histology, which extend from the mon pubis to the perineum
  • Homologous to the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions of the male scrotum Scrotum A cutaneous pouch of skin containing the testicles and spermatic cords. Testicles: Anatomy
• Labia minora: 
  • Paired folds of hairless skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions between the labia majora 
  • Homologous to the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions of the male penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy
• Clitoris: 
  • The erectile structure partially enclosed by the labia minora (also known as the clitoral hood or prepuce Prepuce The double-layered skin fold that covers the glans penis, the head of the penis. Penis: Anatomy), which is similar to the corpora cavernosa Corpora cavernosa Penis: Anatomy
  • The majority of the structure is internal.
  • Structure:
    • Glans: external portion protruding slightly from the clitoral hood 
    • Body: passes under the pubic symphysis
    • Crura: the body splits like a “Y” and form paired crura, which run along the inferior edges of the pubic bones
  • Homologous to the male glans penis Glans Penis Penis: Anatomy
• Vestibular bulbs:
  • Elongated masses of corpus cavernosum (erectile tissue) flanking the vaginal orifice 
  • Located bilaterally just deep to the labia majora
  • Become engorged with blood during sexual arousal and contribute to sexual stimulation 
• Vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy: 
  • Cavity between the labia minora 
  • Contains:
    • Vaginal and urethral orifices 
    • Greater and lesser vestibular glands
• Greater vestibular glands (also known as Bartholin glands): 
  • Paired glands located in the vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy just distal to the vaginal orifice (at approximately 5 o’clock and 7 o’clock if the vaginal orifice was a clock face)
  • Secrete mucus for lubrication during sexual arousal
  • Homologous to bulbourethral glands Bulbourethral Glands Glands situated on each side of the prostate that secrete a fluid component of the seminal fluid into the urethra. in men
• Lesser vestibular glands (also known as Skene glands): 
  • Paired glands located on the distal anterior wall of the vagina adjacent to the external urethral orifice 
  • Homologous to the prostate Prostate The prostate is a gland in the male reproductive system. The gland surrounds the bladder neck and a portion of the urethra. The prostate is an exocrine gland that produces a weakly acidic secretion, which accounts for roughly 20% of the seminal fluid. gland in men
  • Exact function is unknown (believed to secrete lubrication at the urethral opening, which may act as an antimicrobial).

Gross anatomy of the perineum and superficial perineal space

The perineum refers to the external surface, including the vulva, and the shallow “space” beneath.

• Perineum boundaries:
  • Anterior: pubic symphysis
  • Anterolateral: inferior pubic rami
  • Lateral: ischial tuberosities
  • Posterolateral: sacrotuberous ligaments
  • Posterior: coccyx Coccyx The last bone in the vertebral column in tailless primates considered to be a vestigial tail-bone consisting of three to five fused vertebrae. Vertebral Column: Anatomy
• Triangles: an imaginary transverse line between the ischial tuberosities divides the perineum into 2 “triangles”:
  • Anterior: urogenital triangle (includes the vulva)
  • Posterior: anal triangle (includes the anus)
• The superficial perineal space (collectively known as the urogenital diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy) contains 3 muscles:
  • Ischiocavernosus: 
    • Extends anteriorly from the ischial tuberosities toward the clitoris 
    • Assists in clitoral erection Erection The state of the penis when the erectile tissue becomes filled or swollen (tumid) with blood and causes the penis to become rigid and elevated. It is a complex process involving central nervous system; peripheral nervous systems; hormones; smooth muscles; and vascular functions. Penis: Anatomy
  • Bulbospongiosus: 
    • Wraps around the lateral vagina like a pair of parentheses
    • Provides lateral structure and tightens on the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy during intercourse
  • Superficial transverse perineal muscle:
    • Extends medially from the ischial tuberosities toward the perineal body, which is a strong central tendon Central tendon Diaphragm: Anatomy of the perineum
    • Provides structure and support between the vagina and rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy
• Clinical relevance: The bulbospongiosus and superficial transverse perineal muscles often tear during labor and delivery and should be intentionally repaired.

Supporting Structures

The pelvic diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy provides structure to the pelvic cavity and surrounding structures. In addition, 3 primary levels of vaginal support Levels of Vaginal Support Pelvic Organ Prolapse are all connected through endopelvic fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis.

Pelvic diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy

The pelvic diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy is the deepest layer of the pelvic floor.

• Functions:
  • Provide structure to the pelvic floor separating the internal pelvic cavity from the external perineum
  • Resist intraabdominal pressure
• Structure:
  • Muscles start at the tendinous arch (below and parallel to the inferior margin of the pubic bones).
  • Muscles extend posteriorly toward the coccyx Coccyx The last bone in the vertebral column in tailless primates considered to be a vestigial tail-bone consisting of three to five fused vertebrae. Vertebral Column: Anatomy → “wrap around” the urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy, vagina, and rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy, providing lateral support
  • Perineal body: the central tendon Central tendon Diaphragm: Anatomy and the site of attachment for pelvic floor muscles
• Muscles of the pelvic diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy:
  • A group of muscles collectively known as the levator ani muscles:
    • Puborectalis: the innermost muscle originating from the tendinous arch just below the pubic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types and forming a sling around the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy. The puborectalis is in direct contact with the lateral vagina and the lateral and posterior rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy.
    • Pubococcygeus: the middle muscle connecting the tendinous arch/pubic bones to the coccyx Coccyx The last bone in the vertebral column in tailless primates considered to be a vestigial tail-bone consisting of three to five fused vertebrae. Vertebral Column: Anatomy
    • Iliococcygeus: the most lateral layer that connects the ischial spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy to the coccyx Coccyx The last bone in the vertebral column in tailless primates considered to be a vestigial tail-bone consisting of three to five fused vertebrae. Vertebral Column: Anatomy
  • Coccygeus
• Other muscles of the pelvic floor:
  • Piriformis
  • Obturator internus

Primary levels of vaginal support Levels of Vaginal Support Pelvic Organ Prolapse

• Level 1: 
  • The most proximal level of support
  • Consists of the uterosacral ligaments, which suspend the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy and upper vagina to the sacrum Sacrum Five fused vertebrae forming a triangle-shaped structure at the back of the pelvis. It articulates superiorly with the lumbar vertebrae, inferiorly with the coccyx, and anteriorly with the ilium of the pelvis. The sacrum strengthens and stabilizes the pelvis. Vertebral Column: Anatomy and lateral pelvic wall
  • Clinical relevance: Loss of level 1 support leads to uterine prolapse Uterine prolapse Downward displacement of the uterus. It is classified in various degrees: in the first degree the uterine cervix is within the vaginal orifice; in the second degree the cervix is outside the orifice; in the third degree the entire uterus is outside the orifice. Pelvic Organ Prolapse into the vagina.
• Level 2: 
  • Lateral attachments along the length of the vagina
  • Paravaginal attachments to the endopelvic fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis of the levator ani muscles surrounding the vagina
  • Clinical relevance: Loss of level 2 support leads to anterior vaginal wall and bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess prolapse ( cystocele Cystocele A hernia-like condition in which the weakened pelvic muscles cause the urinary bladder to drop from its normal position. Fallen urinary bladder is more common in females with the bladder dropping into the vagina and less common in males with the bladder dropping into the scrotum. Pelvic Organ Prolapse).
• Level 3:
  • The most distal level of support
  • Consists of the perineum and perineal muscles
  • Supports the distal ⅓ of the vagina
  • Clinical relevance: Loss of level 3 support leads to urethral hypermobility and incontinence anteriorly or posterior vaginal wall prolapse (also known as a rectocele Rectocele Herniation of the rectum into the vagina. Pelvic Organ Prolapse) posteriorly.

Neurovasculature

Circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment

• Arterial supply: 
  • Superior vagina: 
    • Vaginal artery (a branch directly off of the internal iliac artery)
    • Vaginal branch of the uterine artery Uterine Artery A branch arising from the internal iliac artery in females, that supplies blood to the uterus. Uterus, Cervix, and Fallopian Tubes: Anatomy (a different branch of the internal iliac artery)
    • Vessels run primarily along the lateral sides of the vagina.
  • Inferior vagina: internal pudendal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
  • Vulva: 
    • Majority of the structures are supplied by the internal pudendal artery (a branch of the internal iliac artery).
    • Lateral structures are supplied by the external pudendal artery (a branch of the femoral artery Femoral Artery The main artery of the thigh, a continuation of the external iliac artery. Femoral Region and Hernias: Anatomy).
• Venous supply: 
  • Vagina: 
    • Veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology form the vaginal venous plexuses around the vagina.
    • The veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology drain into the uterine vein → internal iliac vein
  • The vulval drains via external pudendal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology → great saphenous vein
  • The clitoris drains via the dorsal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology of the clitoris.

Lymphatic drainage

• Upper and middle vagina: external and internal iliac nodes
• Lower vagina and vulva: superficial and deep inguinal nodes

Innervation

• Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation:
  • Vulva:
    • Pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy branches
    • Ilioinguinal nerve Ilioinguinal nerve Inguinal Canal: Anatomy and Hernias branches
    • Genitofemoral nerve Genitofemoral nerve Inguinal Canal: Anatomy and Hernias branches
  • Vagina: 
    • Pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy
    • Pelvic splanchnic nerves ( S2 S2 Heart Sounds– S4 S4 Heart Sounds): afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology fibers of the upper vagina 
• Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation: vulva and vagina: pudendal nerves ( S2 S2 Heart Sounds– S4 S4 Heart Sounds)
• Autonomic innervation:
  • Sympathetic: uterovaginal plexus Uterovaginal plexus Uterus, Cervix, and Fallopian Tubes: Anatomy (off the inferior hypogastric plexus)
  • Parasympathetic: pelvic splanchnic nerves ( S2 S2 Heart Sounds– S4 S4 Heart Sounds)
• Clinical relevance: A pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy block can be used in childbirth to numb the perineum and lower portion of the vagina.

Microstructure

Vaginal microstructure

The vagina is a fibromuscular tube lined by mucosa made up of 3 layers:

1. Outer adventitia:

• Inner layer of dense connective tissue Dense connective tissue Connective Tissue: Histology
• Outer layer of loose connective tissue Loose connective tissue Connective Tissue: Histology

2. Middle muscularis layer:

• 2 indistinct layers of smooth muscle:
  • Outer longitudinal layer
  • Inner circular layer connected by oblique interlacing fibers
• Longitudinal fibers are continuous with superficial muscle fibers of the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy.
• Extensive vascular plexuses surround the muscular layer.

3. Inner mucosal layer:

• Nonkeratinized stratified squamous epithelium Stratified squamous epithelium Surface Epithelium: Histology: 
  • Allows for the normal “wear and tear” experienced by the vagina
  • Cells are ultimately shed from the surface of the mucosa into the vaginal lumen.
  • The basal layer is constantly dividing and replacing the epithelial cells above.
• Epithelial cells contain glycogen:
  • Superficial cells accumulate glycogen, which is secreted into the vaginal lumen when the cells are exfoliated into the vagina.
  • Natural vaginal bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology (particularly Lactobacillus spp.) break down glycogen in desquamated epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology to produce lactic acid.
  • The acidic environment creates a barrier to infection.
• Estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy promotes the storage of glycogen:
  • Glycogen content significantly ↑ at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty
  • Prepubescent and menopausal women have less glycogen → less acidic environment 
• No glands are present in the vaginal mucosa; lubrication is achieved by:
  • Cervical glands via mucus secretion Secretion Coagulation Studies
  • Transudation (i.e., “vaginal sweating”) of serous fluid
  • Secretions from Bartholin glands
• Contains vaginal rugae (numerous transverse folds functioning as friction ridges to stimulate the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy)

Vulvar microstructure

• Labia majora:
  • Longitudinal skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions folds
  • Contain smooth muscle and adipose tissue Adipose tissue Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or “brite” adipose tissue, which is a transitional form. Adipose Tissue: Histology
  • Pubic hair on the lateral surface, no hair on the medial surface
  • Sweat and sebaceous glands on both surfaces
• Labia minora:
  • Contain sweat and sebaceous glands
  • No hair on either surface
• Clitoris:
  • Contains 2 cylinders of erectile tissue ( corpora cavernosa Corpora cavernosa Penis: Anatomy)
  • The glans also contains erectile tissue.
  • Very large number of sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology

Clinical Relevance

Vulvar and vaginal disorders

• Pelvic Organ Prolapse Pelvic Organ Prolapse Pelvic organ prolapse (POP) is a general term that refers to herniation of 1 or more pelvic organs (e.g., bladder, uterus, rectum) into the vaginal canal, and potentially all the way through the introitus. Weakness and insufficiency of the pelvic floor may result in POP. Pelvic Organ Prolapse (POP): prolapse of the vaginal wall and the pelvic organs behind the wall (e.g., bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess or rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy) through the vaginal orifice. Pelvic Organ Prolapse Pelvic Organ Prolapse Pelvic organ prolapse (POP) is a general term that refers to herniation of 1 or more pelvic organs (e.g., bladder, uterus, rectum) into the vaginal canal, and potentially all the way through the introitus. Weakness and insufficiency of the pelvic floor may result in POP. Pelvic Organ Prolapse occurs when the vaginal support Vaginal Support Pelvic Organ Prolapse structures are weakened and unable to support the internal organs against intraabdominal pressure. Major risk factors include age, parity Parity The number of offspring a female has borne. It is contrasted with gravidity, which refers to the number of pregnancies, regardless of outcome. Pregnancy: Diagnosis, Physiology, and Care, and obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity.
• Female sexual dysfunction Sexual dysfunction Physiological disturbances in normal sexual performance in either the male or the female. Sexual Physiology: disorders in any part of the sexual response cycle, including desire, arousal, orgasmic, and pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways disorders. One particularly notable pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways disorder is vulvodynia, a chronic pain syndrome Chronic Pain Syndrome Fibromyalgia of the vulva without an identifiable cause often severely limiting the ability to engage in sexual activity.
• Vulvovaginitis Vulvovaginitis The term vulvovaginitis is used to describe an acute inflammation of the vulva and vagina. Vulvovaginitis can be caused by several infectious and non-infectious etiologies, and results from disruption of the normal vaginal environment. Common signs and symptoms include pain, pruritus, erythema, edema, vaginal discharge and dyspareunia. Vulvovaginitis: an acute inflammation Acute Inflammation Inflammation of the vulva and the vagina due to an infectious etiology. The 2 most common forms are candidiasis Candidiasis Candida is a genus of dimorphic, opportunistic fungi. Candida albicans is part of the normal human flora and is the most common cause of candidiasis. The clinical presentation varies and can include localized mucocutaneous infections (e.g., oropharyngeal, esophageal, intertriginous, and vulvovaginal candidiasis) and invasive disease (e.g., candidemia, intraabdominal abscess, pericarditis, and meningitis). Candida/Candidiasis (caused by Candida Candida Candida is a genus of dimorphic, opportunistic fungi. Candida albicans is part of the normal human flora and is the most common cause of candidiasis. The clinical presentation varies and can include localized mucocutaneous infections (e.g., oropharyngeal, esophageal, intertriginous, and vulvovaginal candidiasis) and invasive disease (e.g., candidemia, intraabdominal abscess, pericarditis, and meningitis). Candida/Candidiasis yeast Yeast A general term for single-celled rounded fungi that reproduce by budding. Brewers’ and bakers’ yeasts are saccharomyces cerevisiae; therapeutic dried yeast is yeast, dried. Mycology species) and bacterial vaginosis Bacterial vaginosis Polymicrobial, nonspecific vaginitis associated with positive cultures of gardnerella vaginalis and other anaerobic organisms and a decrease in lactobacilli. It remains unclear whether the initial pathogenic event is caused by the growth of anaerobes or a primary decrease in lactobacilli. Vulvovaginitis (a polymicrobial bacterial infection).
• Bartholin gland abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease: Bartholin glands can become occluded and develop cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change, which can then become infected. The resulting abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease typically presents as a painful mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast in the vestibule Vestibule An oval, bony chamber of the inner ear, part of the bony labyrinth. It is continuous with bony cochlea anteriorly, and semicircular canals posteriorly. The vestibule contains two communicating sacs (utricle and saccule) of the balancing apparatus. The oval window on its lateral wall is occupied by the base of the stapes of the middle ear. Ear: Anatomy at the location of the Bartholin gland (5 o’clock or 7 o’clock when viewing the vaginal orifice as a clock face). The abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is treated with incision and drainage Incision And Drainage Chalazion. A small catheter is often placed to allow for continued drainage and to decrease the risk of recurrence. Occasionally, surgical management is required.
• Vulvar and vaginal cancer Vaginal cancer Primary vaginal cancers are malignant tumors that originate from cells in the vagina. Squamous cell carcinoma (SCC) is by far the most common (80%-85%); other histologic types include adenocarcinomas, sarcomas (including sarcoma botryoides, typically seen in children), and melanomas. Vaginal Cancer: relatively uncommon types of cancer in the female reproductive tract. Risk factors for vaginal cancer Vaginal cancer Primary vaginal cancers are malignant tumors that originate from cells in the vagina. Squamous cell carcinoma (SCC) is by far the most common (80%-85%); other histologic types include adenocarcinomas, sarcomas (including sarcoma botryoides, typically seen in children), and melanomas. Vaginal Cancer include HPV HPV Human papillomavirus (HPV) is a nonenveloped, circular, double-stranded DNA virus belonging to the Papillomaviridae family. Humans are the only reservoir, and transmission occurs through close skin-to-skin or sexual contact. Human papillomaviruses infect basal epithelial cells and can affect cell-regulatory proteins to result in cell proliferation. Papillomavirus (HPV) infection and exposure to diethylstilbestrol Diethylstilbestrol A synthetic nonsteroidal estrogen used in the treatment of menopausal and postmenopausal disorders. It was also used formerly as a growth promoter in animals. According to the fourth annual report on carcinogens, diethylstilbestrol has been listed as a known carcinogen. Noncontraceptive Estrogen and Progestins (DES) in utero (a medication commonly prescribed for pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care complications until the early 1970s). Lichen sclerosus Lichen Sclerosus Atrophy and shriveling of the skin of the vulva that is characterized by the whitish lichen sclerosus appearance, inflammation, and pruritus. Benign Vulvar Conditions is a significant risk factor for vulvar cancer Vulvar cancer There are multiple different types of malignancies that can affect the vulva. The most common histologic type is squamous cell carcinoma (SCC), which accounts for approximately 75%-85% of all vulvar cancers. Vulvar Cancer.

Obstetric clinical relevance

• Obstetric lacerations: spontaneous tears to the perineum, vagina, or cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy occurring as a result of trauma due to the infant passing through the vaginal canal during delivery. Frequently, the bulbospongiosus and superficial transverse perineal muscles are lacerated and should be intentionally repaired to restore anatomic structure and function.
• Pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy block: opioid Opioid Compounds with activity like opiate alkaloids, acting at opioid receptors. Properties include induction of analgesia or narcosis. Constipation injection into the area surrounding the pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy providing excellent pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways relief to the perineum and lower vagina. The pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy block can provide anesthesia Anesthesia A state characterized by loss of feeling or sensation. This depression of nerve function is usually the result of pharmacologic action and is induced to allow performance of surgery or other painful procedures. Anesthesiology: History and Basic Concepts during perineal laceration Laceration Torn, ragged, mangled wounds. Blunt Chest Trauma repairs without an epidural. The pudendal nerve Pudendal nerve A nerve which originates in the sacral spinal cord (s2 to s4) and innervates the perineum, the external genitalia, the external anal sphincter and the external urethral sphincter. It has three major branches: the perineal nerve, inferior anal nerves, and the dorsal nerve of penis or clitoris. Gluteal Region: Anatomy block does not cover the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy and provides no relief against contraction pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways.

Related anatomical structures

• Pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy: consists of the pelvic girdle, pelvic cavity, pelvic floor, and all the viscera, vessels, and muscles contained in the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy. The pelvic cavity houses various gastrointestinal and urogenital structures. 
• Uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy: a pear-shaped, hollow organ composed of smooth muscle functioning to nourish the developing fetus until the end of the pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care. The uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy is also responsible for expulsion of the infant.