Download Lecture 19: Female External Genitalia and Breast Intro to

Lecture 19: Female External Genitalia and Breast
Intro to Urogenital Triangle:
 Contents
 The urogenital triangle represents the anterior half of the perineum
 In females, the UG triangle contains all of the external genitalia and associated muscles, and openings for
the urethra and vagina
 In males, the UG triangle contains the root of the penis and associated muscles, and the scrotum
 Borders
 Like the anal triangle, the roof of the UG triangle is the pelvic diaphragm
 Unlike the anal triangle, the UG triangle has a support platform (for genitalia)
 Perineal membrane
 The perineal membrane is a thin sheet of tough fascia that stretches between the two sides of the pubic
arch
 It covers the anterior part of the pelvic outlet
 The perineal membrane fills the anterior gap in the pelvic diaphragm (UG hiatus)
 However the perineal membrane is perforated by the urethra (both sexes) and the vagina
 Fasciae and Pouches of the Triangle
 Background
 The contents of the UG triangle are organized by a series of pouches and fascial layers
 Much of this fascia is continuous with similar fascia of the anterior abdominal wall
 Perineal Fasciae
 Background
 The perineal fascia—like other body fasciae—consists of two parts
1. Superficial fascia (Subcutaneous Tissue of the Perineum)
 As in the portion of the abdomen inferior to the umbilicus, the subcutaneous tissue of the
perineum consists of two layers
1. Superficial fatty layer
2. Deep membranous layer (Superficial Perineal Fascia or Colles fascia)
 AKA (especially clinically) superficial perineal fascia, or Colles fascia
 The deep membranous layer (superficial perineal fascia/Colles fascia) does not extend
into the anal triangle
 It is attached to the posterior margin of the perineal membrane
 Laterally, the deep membranous layer is continuous with the fascia lata (of the thigh)
 Note that fascia lata is a “typical” deep fascia, deep to superficial fascia of the thigh
 Males
 Anteriorly in males, the deep membranous layer is continuous with dartos fascia of
the penis and scrotum
 On each side of, and anterior to the scrotum, the deep membranous layer becomes
continuous with Scarpa fascia
 Females
 In females, the deep membranous layer passes superior to the labia majora and
becomes continuous with Scarpa fascia
2. Deep Perineal Fascia
 The deep perineal fascia (investing, or Gallaudet fascia) invests the muscles of the perineum
 This fascia is attached laterally to the ischiopubic rami
 Anteriorly it is continuous with the deep fascia of the external oblique and rectus abdominis, as
well as suspensory ligaments of penis or clitoris
 Superficial Perineal Pouch
 Background
 The superficial perineal pouch (compartment) is a potential space between the deep membranous layer
of the subcutaneous tissue of the perineum, and the perineal membrane
 The principal structures of this pouch are the erectile tissues (penis and clitoris) and their associated
skeletal muscle
 Deep Perineal Pouch
 Background
 The deep perineal pouch is bounded inferiorly by the perineal membrane, superiorly by the pelvic
diaphragm, and laterally by obturator fascia (of obturator internus muscle)
 The deep perineal pouch includes the fat-filled anterior recesses of the ischioanal fossa
 Contents
 The deep perineal pouch has contents common to both sexes
 Part of the urethra and associated part of the external urethral sphincter
 Neurovascular structures for external genitalia
 Various muscles
 Fat
 Clinical
 A forceful blow to the male perineum can rupture the spongy urethra in the bulb of the penis
 Urine and blood extravasate (escape) into the superficial perineal pouch, and their direction of flow
is determined by attachments of the perineal fascia
Female Urogenital Triangle:
 Introduction
 As mentioned previously, the female UG triangle includes the external genitalia and the perineal muscles
1. External Genitalia
 Components
 The female external genitalia comprise several structures
 Mons pubis
 Labia majora
 Labia minora (enclose vestibule of vagina)
 Clitoris
 Bulbs of vestibule
 Greater and lesser vestibular glands

Mons Pubis and Labia
 Mons Pubis
 The mons pubis is the rounded, fatty eminence anterior to the pubic symphysis
 Under the influence of estrogen it enlarges at puberty and becomes covered with coarse hair
 Protection of pubis?

Development
 Development of the external genitalia begins in the 3rd week, with the advent of structures common
to both sexes
 Indifferent stage
 In the seventh week, structures of the indifferent stage take on specific gender characteristics
 However, because of common origin, the external genitalia exhibit homology between males
and females

Labia Majora
 The labia majora are two prominent, longitudinal folds of skin running from the mons pubis to the
perineal body
 They form the lateral borders of the vulva, and provide some protection to the clitoris, and
urethral and vaginal openings
 The labia majora—homologous to the skin of the scrotum—are covered with hair and consist
primarily of loose subcutaneous tissue

Labia Minora
 The labia minora are hairless folds of fat-free skin that lie between the labia majora
 They surround and close over the vestibule of the vagina
 Anteriorly, each labium contributes to the formation of the prepuce, and the frenulum of the
clitoris (the labia minora are homologous to the skin of the penis)
 Note that the labia minora contain erectile tissue at their base, and that engorgement withblood
causes the labia to enlarge and protrude, often beyond the borders of the labia majora.

Clitoris
 Background
 The clitoris—which is homologous to the penis—is an erectile organ located where the labia
minora meet anteriorly
 Unlike the penis, the clitoris is not related to the urethra, or to urination
 With high cutaneous sensitivity, the clitoris is central to the sexual response
 Anatomy
 Like the penis, the clitoris consists of an attached part and a free part
 The attached part, or the root, consists of two crura attaching to the ischiopubic rami and
the perineal membrane
 The free part consists of a body and a head (glans)
 The body consists of two corpora cavernosa, which are extensions of the crura
 The glans is connected to the bulbs of the vestibule by thin bands of erectile tissue

Bulbs and Glands
 Bulbs of the Vestibule
 The bulbs of the vestibule are paired masses of elongated erectile tissue ~3cm long
 They lie along the sides of the vaginal orifice, immediately inferior to the perineal
membrane, in the superficial perineal pouch
 In part, engorgement of the bulbs causes constriction in the lower third of the vagina
 Note that vaginal smooth muscle and striated perineal muscle also contribute to constriction.
 Greater Vestibular Glands
 The round greater vestibular (Bartholin) glands lie on either side of the vaginal orifice, posterior
to the bulbs of the vestibule (also within the superficial perineal pouch)
 ~0.5 cm in diameter
 Along with cervical glands, the greater vestibular glands secrete much of the mucus necessary
for lubrication during intercourse
 Notes:
 Note that the vagina has no glands, thus lubrication for intercourse comes mainly from
mucus secreted by cervical and vestibular glands. As well, some lubricant is provided by
blood ultrafiltrate of the vaginal wall, and male secretions from the bulbourethral glands
(pre-ejaculatory fluid).
2. Perineal Muscles
 Introduction
 Anatomy
 The perineal muscles are located in two general areas
 Deep perineal pouch
 Superficial perineal pouch
 General Function
 In both sexes, muscles of the superficial perineal pouch are related to the function of erectile tissue
 In males, these muscles are additionally required for ejaculation, and forcing out urine
 Muscles of the superficial perineal pouch tend to be better developed in males
 In both sexes, muscles of the deep perineal pouch are associated with the urethra and thus play a direct
role in urinary continence
 Superficial Perineal Pouch
 Background
 In the superificial perineal pouch, both males and females have the same three muscles
1. Superficial transverse perineal muscle
2. Ischiocavernosus
3. Bulbospongiosus
1. Superficial Transverse Perineal Muscle
 The superficial transverse perineal muscle helps fix the perineal body and the pelvic diaphragm
 Supports abdominopelvic viscera and resists increased intraabdominal pressure
2. Ischiocavernosus
 In females, ischiocavernosus covers the crura of the clitoris
 It is attached to the ischiopubic rami, the crura, and the perineal membrane
 This muscle maintains erection of the clitoris by forcing blood from the root into the body, and by
compressing the outflow veins (to keep blood in the clitoris)
3. Bulbospongiosus
 In females, bulbospongiosus attaches to the perineal body posteriorly, and the crus of the clitoris
 This muscle plays a role in various sexual functions
 It constricts the vaginal orifice
 It compresses the greater vestibular gland
 It assists in erection of the clitoris
 Deep Perineal Pouch
 Background
 In the deep perineal pouch, muscle content differs slightly between males and females
 Common muscles
 External urethral sphincter
 In females only
 Compressor urethrae, sphincter urethrovaginalis, and band of smooth muscle,
 In males only
 Deep transverse perineal (in lieu of band of smooth muscle)
 Innervation of Vulva
 Somatic
 From Lumbar Plexus
 The anterior labial nerves supply the anterior aspect of the external genitalia, mainly the mons pubis
 The anterior labial nerves derive from the ilioinguinal nerve, and genital branch of genitofemoral
nerve
 From Sacral Plexus
 The perineal branch of the posterior cutaneous nerve of the thigh innervates the external genitalia
laterally
 Two main branches of the pudendal nerve supply the external genitalia centrally
1. Perineal nerve
 Posterior labial nerves supply the labia
 Deep branch of perineal nerve serves the superficial perineal muscles
2. Dorsal nerve of the clitoris supplies deep perineal muscles and sensation to the clitoris
 Autonomic
 Summary
 The bulb of the vestibule and the erectile bodies of the clitoris receive parasympathetic innervation via
cavernous nerves from the uterovaginal nerve plexus
 Parasympathetic stimulation produces increased vaginal secretion, and engorgement of the clitoris
and bulbs of the vestibule
 Blood Supply of Vulva
 Blood supply to the vulva is from branches of the internal and external pudendal arteries
 The internal pudendal artery supplies most of the skin, external genitalia, and perineal muscles
 Lymphatics of UG Triangle
 There are three main routes of lymphatic drainage from the UG triangle
 Vulva (most parts)
 Superficial inguinal nodes
 Glans clitoris and labia minora
 Deep inguinal or internal iliac nodes
 Urethra
 Internal iliac or sacral nodes
Breast:
 Background
 Breasts are the most prominent superficial structures of the anterior
thoracic wall
 General Structure
 Breasts consist of glandular and supporting fibrous tissue embedded within
a fatty matrix in the subcutaneous tissue of the pectoral region
 Surface Anatomy
 At the greatest prominence of the breast is the nipple
 It is surrounded by a circular pigmented area of skin
 Areola
 Gross Anatomy
 The bed of the breast is formed by deep fascia covering pectoralis
major, serratus anterior, and external oblique
 The retromammary space (females only) is superficial to the deep fascia
 Allows breast movement
 A small part of the breast may extend toward the axilla
 Axillary tail
Note that malignant invasion of the
retromammary space, or deep fascia,
results in elevation of the breast
during muscular contraction, a sign
of advanced breast cancer.
 Mammary Glands
 Microanatomy
 Background
 The mammary glands are modified sweat glands that produce
The axillary tail is sometimes
milk
prone to be mistaken for a
 They are accessory to reproduction in females, and are
lump, or enlarged lymph
secondary sexual features
nodes. This is particularly true
 Mammary glands are present in males, but are rudimentary
when the tail is enlarged
and functionless
during the menstrual cycle
 Lobules and Lobes
 One lobule and its terminal duct make up the basic secretory
unit of the female breast
 A lobe consists of numerous lobules
 Each mammary gland consists of 15-20 lobes
 Lobes tend to merge at their edges and are not distinguishable in surgery
 Ducts and Sinuses
 Each lobe has its own lactiferous duct
 Thus 15-20 ducts converge on the nipple and open independently on the nipple
 Near its orifice, each duct is slightly expanded to form a lactiferous sinus
 The sinuses expand further during lactation
 Attachment
 Background
 The mammary gland is attached in two ways
1. Firm attachment by suspensory ligaments (of Cooper), which run from the dermis of the overlying
skin to the deep fascia of muscle
 These ligaments are more developed in the superior part of the breast
2. Loose attachment to deep fascia of muscle
 Breast Blood Supply
 Arterial supply to the breasts derives from two sources
 Posterior intercostal arteries
 Internal thoracic arteries
 Venous drainage is mainly to the axillary vein
 Some drainage to internal thoracic vein
 Breast Innervation
 Nerve supply to the breast is from two sources
 Supraclavicular nerves
 Intercostal nerves
 Lateral mammary branches
 Medial mammary branches
 These convey sensory and sympathetic fibers
 Sympathetics to blood vessels and smooth muscle of skin and nipple
 Breast Lymphatics
 Anatomy
 Background
 Lymphatic drainage in the breast follows one major route
 Axillary nodes
 30-60 axillary nodes drain >75% of lymph
 The remaining lymph drains to parasternal and abdominal nodes
 Clinical
 Background
 The lymphatic flow of the breast is of clinical significance because metastatic dissemination occurs
primarily by lymphatic routes
 Axillary Nodes
 The axillary nodes—generally the first to be affected by metastasis—are divided into three levels (I-III)
 The (5-year) survival rate in breast cancer patients correlates most strongly with the number of nodes
involved at these levels
 Level I involvement (65%); level II involvement (31%), level III involvement (near 0%)
 Male Breast
 Background
 The male breast contains no unique elements (compared to the female breast)
 Glands are underdeveloped
 Usually only small ducts that do not extend beyond areola
 Fat content is not different from that of subcutaneous tissue elsewhere
 Clinical
 Breast cancer
 Approximately 1.5% of breast cancer cases occur in males
 Gynecosmastia
 Excessive proliferation of the male mammary glands due mainly to ductal proliferation
 Generally secondary to increased estrogen levels
 Mild cases in adolescence