UROGENITAL TRIANGLE Urogenital triangle The urogenital triangle makes

UROGENITAL TRIANGLE

Urogenital triangle The urogenital triangle makes up the anterior portion of the perineum. It contains the roots of the external genitalia and the openings of the urogenital system The female urogenital triangle is home to the opening of the vagina, the urethra, and the clitoris. Sunday, January 2, 2022 Lufukuja G. 2

Urogenital triangle Boundaries Anteriolly • Lower margin of pubic symphysis and arcuate pubic ligament Posterior • Imaginary line joining the two ischial tuberosities On each side • Ischio-pubic ramus

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Contents of the Urogenital Triangle • In the male, the triangle contains the penis and scrotum. • In the female, the triangle contains the external genitalia and the orifices of the urethra and the vagina.

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Urogenital triangle… • The structures closing the urogenital triangle from below upwards (superficial to deep) include, 1) Skin 2) Fatty layer of superficial fascia 3) Membranous layer of superficial fascia (Colles fascia) 4) Contents of the superficial perineal pouch 5) Urogenital diaphragm • 5. 1 Perineal membrane (Inferior fascia of urogenital diaphragm) • 5. 2 Contents of deep perineal pouch • 5. 3 Superior fascia of urogenital diaphragm 14 -03 -2011 7

The perineal fascia • The perineal fascia of the urogenital triangle includes superficial and deep layers. • The superficial fascia of the urogenital triangle can be divided into a fatty layer and a membranous layer (Colles fascia). • Note: In males, the fatty layer is much thinner and is absent in the penis and scrotum Sunday, January 2, 2022 Lufukuja G. 8

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The fatty layer (fascia of Camper) • The fatty layer (fascia of Camper) is continuous with the fat of the ischiorectal fossa and the superficial fascia of the thighs. • In the scrotum, the fat is replaced by smooth muscle, the dartos muscle. The dartos muscle contracts in response to cold and reduces the surface area of the scrotal skin • They are supplied by sympathetic nerves from the superior hypogastric plexus Sunday, January 2, 2022 Lufukuja G. 13

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The membranous layer • The membranous layer (Colles' fascia) is attached posteriorly to the posterior border of the urogenital diaphragm and laterally to the margins of the pubic arch; anteriorly it is continuous with the membranous layer of superficial fascia of the anterior abdominal wall (Scarpa's fascia). The fascia is continued over the penis (or clitoris) as a tubular sheath Sunday, January 2, 2022 Lufukuja G. 16

Superficial Perineal Pouch • Boundaries • Bounded below by the membranous layer of superficial fascia and above by the urogenital diaphragm. • It is closed behind by the fusion of its upper and lower walls. Laterally, it is closed by the attachment of the membranous layer of superficial fascia and the urogenital diaphragm to the margins of the pubic arch • Anteriorly, the space communicates freely with the potential space lying between the superficial fascia of the anterior abdominal wall and the anterior abdominal muscles

Applied antomy • Rupture of the Urethra in Males and Extravasation of Urine • An injury to the urethra leaving Buck's fascia intact results in a collection of urine (extravasation) limited to the penis, deep to Buck's fascia. However, if the injury to the bulb of the penis results in urethral injury accompanying a tear of the Buck's fascia, then extravasated blood and urine would accumulate in the superficial perineal space, passing into the penis (outer to Buck's fascia) as well as the scrotum and lower anterior abdominal wall. G. LUFUKUJA 21

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Applied antomy • Extravasation of urine • Although there are no barriers (other than gravity) to prevent fluid from spreading superiorly from this space, it cannot spread inferiorly into the thigh because the membranous layer fuses with the deep fascia of the thigh (fascia lata) along a line approximately 2. 5 cm inferior and parallel to the inguinal ligament. G. LUFUKUJA 24

Urogenital triangle… Contents of the superficial perineal pouch • The superficial perineal pouch is the area located between the perineal membrane (undersurface of the urogenital diaphragm) and a membranous layer of superficial fascia. • The principal structures in this pouch are the erectile tissues of the penis and clitoris and associated skeletal muscles. 14 -03 -2011 25

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. Contents of the superficial perineal pouch… Erectile tissues • These attached parts are often termed the crura (from the Latin for 'legs') of the clitoris or the penis. • The distal ends of the corpora, which are not attached to bone, form the body of the clitoris in women and the dorsal parts of the body of the penis in men. 14 -03 -2011 27

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Contents of the superficial perineal pouch… Erectile tissues • A pair of cylindrically shaped corpora cavernosa, one on each side of the urogenital triangle, are anchored by their proximal ends to the pubic arch. 14 -03 -2011 31

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Contents of the superficial perineal pouch… Greater vestibular glands • The greater vestibular glands (Bartholin's glands) are seen in women. • They are small, pea-shaped mucous glands that lie posterior to the bulbs of the vestibule on each side of the vaginal opening and are the female homologues of the bulbourethral glands in men. 14 -03 -2011 35

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Contents of the superficial perineal pouch… Muscles • The superficial perineal pouch contains three pairs of muscles: 1. The ischiocavernosus 2. Bulbospongiosus, and 3. Superficial transverse perineal muscles. • Two of these three pairs of muscles are associated with the roots of the penis and clitoris; the other pair is associated with the perineal body. 14 -03 -2011 37

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Contents of the superficial perineal pouch… Muscles… 1. Ischiocavernosus • The two ischiocavernosus muscles cover the crura of the penis and clitoris. • Each muscle is anchored to the medial margin of the ischial tuberosity and related ischial ramus and passes forward to attach to the sides and inferior surface of the related crus. 14 -03 -2011 39

Contraction of this muscle assists in causing the erection of the clitoris by forcing blood from the crus into the body of the erect penis and clitoris. 14 -03 -2011 40

superficial perineal pouch… 2. Bulbospongiosus • The two bulbospongiosus muscles are associated mainly with the bulbs of the vestibule in women and with the attached part of the corpus spongiosum in men. • The bulbospongiosus muscle surrounds the orifice of the vagina and covers the vestibular bulbs. 14 -03 -2011 41

The fibers of bulbospongiosus extend forward to gain attachment to the corpora cavernosa of the clitoris. The bulbospongiosus muscle reduces the size of the vaginal orifice and compresses the deep dorsal vein of the clitoris, thereby assisting in the mechanism of erection in the clitoris. 14 -03 -2011 43

Contents of the superficial perineal pouch… Muscles… 2. Bulbospongiosus… • In men, the bulbospongiosus muscles are joined in the midline to a raphe on the inferior surface of the bulb of the penis. • The raphe is anchored posteriorly to the perineal body. • Muscle fibers course anterolaterally, on each side, from the raphe and perineal body to cover each side of the bulb of the penis and attach to the perineal membrane and connective tissue of the bulb. • Others extend anterolaterally to associate with the crura and attach anteriorly to the ischiocavernosus muscles 14 -03 -2011 44

Contents of the superficial perineal pouch… • In men, the bulbospongiosus muscles have two additional functions: 1. They facilitate emptying of the bulbous part of the penile urethra following urination (micturition); and 2. Their reflex contraction during ejaculation is responsible for the pulsatile emission of semen from the penis. 14 -03 -2011 45

Urogenital triangle… Contents of the superficial perineal pouch… Muscles… 3. Superficial transverse perineal muscles • The paired superficial transverse perineal muscles follow a course parallel to the posterior margin of the inferior surface of the perineal membrane. • These flat band-shaped muscles, which are attached to ischial tuberosities and rami, extend medially to the perineal body in the midline and stabilize the perineal body. • Nerve Supply: All the muscles of the superficial perineal pouch are supplied by the perineal branch of the pudendal nerve. 14 -03 -2011 46

Muscles of the superficial perineal pouch Muscle Origin Insertion Innervatio n Function Ischiocavernosus Ischial tuberosity and ramus Crus of penis and clitoris Pudendal nerve (S 2 to S 4) Move blood from crura into the body of the erect penis and clitoris Bulbospongiosus In women: perineal body In men: perineal body, midline raphe In women: bulb of vestibule, perineal membrane, body of clitoris and corpus cavernosum In men: bulbospongiosus, perineal membrane, corpus cavernosum Pudendal nerve (S 2 to S 4) Move blood from attached parts of the clitoris and penis into the glans In men: removal of residual urine from urethra after urination; pulsatile emission of semen during ejaculation Superficial transverse perineal Ischial tuberosity and ramus Perineal body Pudendal nerve (S 2 to S 4) Stabilize the perineal body 14 -03 -2011 47

Urogenital Diaphragm Urogenital diaphragm • It is a triangular musculofascial diaphragm situated in the anterior part of the perineum, filling in the gap of the pubic arch • It consists of two muscles – sphincter urethrae and deep transverse perinei • NOTE: The inferior layer of fascia is often referred to as the perineal membrane. 14 -03 -2011 48

Urogenital Diaphragm… Fascia of the urogenital diaphragm Anteriorly, the two layers of fascia fuse, leaving a small gap beneath the symphysis pubis Posteriorly, the two layers of fascia fuse with each other Laterally, the layers of fascia are attached to the pubic arch The closed space that is contained between the superficial and deep layers of fascia is known as the deep perineal pouch 14 -03 -2011 49

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Transverse Perineal Ligament Perineal membrane Superior fascia of urogenital diaphragm 14 -03 -2011 52

Contents of the deep perineal pouch 1. Part of the urethra, centrally. 2. The inferior part of the external urethral sphincter muscle, above the center of the perineal membrane, surrounding the urethra. 3. Deep transverse perineal muscles 4. Anterior extensions of the ischioanal fat pads. 5. Bulbourethral glands in males 6. Dorsal neurovascular structures of the penis/clitoris

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Perineal membrane (Inferior fascia of urogenital diaphragm)… • In the male, the perineal membrane is crossed by the urethra, 2– 3 cm behind the inferior border of the symphysis pubis; the vessels and nerves to the bulb of the penis; the ducts of the bulbourethral glands 14 -03 -2011 57

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APPLIED ANATOMY… Pudendal nerve block • A common method for relieving the pain associated with childbirth is to inject an anesthetic agent into the tissue surrounding the pudendal nerve near the point where it enters the perineum through the lesser sciatic foramen, at the ischial spine. . 14 -03 -2011 59

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APPLIED ANATOMY… Vulval Infection • In the region of the vulva, the presence of numerous glands and ducts opening onto the surface , makes this area prone to infection. • The sebaceous glands of the labia majora, the ducts of the greater vestibular glands, the vagina (with its indirect communication with the peritoneal cavity), the urethra, and the paraurethral glands can all become infected. • The vagina itself has no glands and is lined with stratified squamous epithelium. Provided that the p. H of its interior is kept low, it is capable of resisting infection to a remarkable degree. 14 -03 -2011 61

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