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Urogenital Triangle & External Genitalia

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1 Urogenital Triangle & External Genitalia
Pelvis & Perineum Unit Lecture 7 د. حيدر جليل الأعسم

2 Urogenital Triangle It is bounded in front by pubic arch and laterally by ischial tuberosities. Superficial Fascia: divided into: A. Fatty layer (Camper’s fascia) continuous with ischiorectal fossa fat & superficial fascia of thighs. In scrotum, fat is replaced by dartos muscle. B. Membranous layer (Colles' fascia) attached posteriorly to posterior border of urogenital diaphragm & laterally to margins of pubic arch; anteriorly it is continuous with membranous layer of superficial fascia of anterior abdominal wall (Scarpa's fascia). Fascia is continued over penis (clitoris) as a tubular sheath.

3 Urogenital Triangle Superficial Perineal Pouch: It is bounded Below by membranous layer of superficial fascia Above by urogenital diaphragm. Behind, It is closed by fusion of its upper and lower walls. Laterally, it is closed by attachment of membranous layer of superficial fascia &urogenital diaphragm to margins of pubic arch. Anteriorly, It communicates freely with potential space between superficial fascia of anterior abdominal wall & abdominal muscles.

4 Urogenital Triangle Urogenital Diaphragm: is a triangular musculofascial diaphragm situated in anterior part of perineum, filling in gap of pubic arch. It is formed by sphincter urethrae & deep transverse perineal muscles, which are enclosed between superior & inferior layers of fascia of urogenital diaphragm. Inferior layer of fascia is the perineal membrane. Anteriorly 2 layers of fascia fuse leaving gap below symphysis pubis. Posteriorly, 2 layers of fascia fuse with each other & with membranous layer of superficial fascia & perineal body. Laterally, layers of fascia are attached to pubic arch. Space between superficial & deep layers of fascia is deep perineal pouch

5 Contents of Urogenital Triangle in Male
Penis: It has a fixed root and a body that hangs free. Root of Penis: is made up of three masses of erectile tissue called bulb of penis and right & left crura of penis. A. Bulb: situated in midline & attached to undersurface of urogenital diaphragm & continued forward into body forming corpus spongiosum. It is traversed by urethra and is covered on its outer surface by bulbospongiosus muscles. B. Crus: is attached to side of pubic arch & is covered on its outer surface by ischiocavernosus muscle. Two crura converge anteriorly & come to lie side by side in dorsal part of body of penis, forming corpora cavernosa.

6 Contents of Urogenital Triangle in Male
Body of Penis: is composed of 3 cylinders of erectile tissue enclosed in a tubular sheath of fascia (Buck's fascia). Erectile tissue is made up of two dorsally placed corpora cavernosa & single ventral corpus spongiosum which, at its distal extremity, expands to form glans penis that covers distal ends of corpora cavernosa. On tip of glans penis is, a slitlike orifice of urethra, external urethral meatus. Prepuce or foreskin is a hoodlike fold of skin that covers glans & connected to it below urethral orifice by frenulum. Body of penis is supported by 2 condensations of deep fascia that extend downward from linea alba & symphysis pubis to be attached to fascia of penis. A. Fundiform lig. B. Suspensory lig of Penis

7 Blood Supply of Penis Arteries: Corpora cavernosa are supplied by deep arteries of penis; corpus spongiosum is supplied by artery of bulb. In addition, there is dorsal artery of penis. All arteries are branches of internal pudendal Artery. Veins: into internal pudendal veins. Lymph Drainage: Deep structures of penis: into internal iliac nodes. Skin of penis: into medial group of superficial inguinal nodes. Nerve Supply: from pudendal nerve & pelvic plexuses.

8 Blood supply of Scrotum
Arteries: External pudendal branches of femoral and scrotal branches of internal pudendal arteries. Veins: veins accompany arteries. Lymph Drainage: wall of scrotum is drained into medial group of superficial inguinal lymph nodes. Lymph drainage of testis & epididymis ascends in spermatic cord & ends in lumbar (para-aortic) lymph nodes. Nerve Supply: anterior surface of scrotum is supplied by ilioinguinal nerve & genital branch of genitofemoral nerve, posterior surface is supplied by branches of perineal nerves & posterior cutaneous nerve of thigh.

9 Superficial Perineal Pouch in Male
It contains structures forming root of penis & muscles covering: Bulbospongiosus muscles: situated one on each side of midline & cover bulb of penis & posterior portion of corpus spongiosum. They compress penile part of urethra & empty residual urine or semen. Anterior fibers also compress deep dorsal vein of penis, thus impeding venous drainage of erectile tissue & assist in process of penis erection. Ischiocavernosus muscles: cover crus penis & compress crus penis and assist in process of erection of penis. Superficial Transverse Perineal Muscles: lie in posterior part of superficial perineal pouch. Each muscle arises from ischial ramus and is inserted into perineal body. They fix perineal body in perineum center. Nerve Supply: superficial perineal pouch muscles are supplied by perineal branch of pudendal nerve.

10 Deep Perineal Pouch in Male
Membranous part of urethra Sphincter urethrae Deep transverse perineal muscles Bulbourethral glands Internal pudendal vessels & branches Dorsal nerves of penis

11 Contents of Deep Perineal Pouch in Male
Membranous Part of Urethra: is about 1.3 cm long and lies within urogenital diaphragm, surrounded by sphincter urethrae muscle; it is continuous above with prostatic urethra and below with penile urethra. It is shortest & least dilatable part of urethra. Sphincter Urethrae Muscle: arises from pubic arch bilaterally & passes medially to encircle urethra in deep perineal pouch. Nerve Supply: Perineal branch of pudendal nerve supplies sphincter. Action: Muscle compresses membranous part of urethra and relaxes during micturition. It can voluntarily stop micturition. Deep Transverse Perineal Muscles: lie posterior to sphincter urethrae muscle. Each muscle arises from ischial ramus and passes medially to be inserted into perineal body.

12 Contents of Deep Perineal Pouch in Male
Bulbourethral Glands: are two small glands that lie beneath sphincter urethrae muscle. Their ducts pierce perineal membrane to enter penile urethra. Secretion is poured into urethra during erotic stimulation. Internal Pudendal Artery: enters deep perineal pouch & give rise to artery to bulb; arteries to crura (deep artery of penis) & dorsal artery of penis, which supplies skin and fascia of penis. Dorsal Nerve of Penis: on each side passes forward through deep perineal pouch and supplies skin of penis.

13 Male Urethra It is 20 cm long from neck of bladder to external meatus on glans penis 1. Prostatic urethra: about 3 cm long & passes through prostate from base to apex. It is widest & most dilatable portion of urethra. 2. Membranous urethra about 1.3 cm long within urogenital diaphragm, surrounded by sphincter urethrae. It is least dilatable portion of urethra. 3. Penile urethra is about 16 cm long & is enclosed in bulb and corpus spongiosum of penis. External meatus is narrowest part of urethra. Part of urethra within glans penis is dilated to form fossa terminalis (navicular fossa).

14 Contents of Urogenital Triangle in Female
It contains external genitalia & orifices of urethra & vagina. Clitoris: It corresponds to penis in male & situated at apex of vestibule anteriorly. It has a structure similar to penis. Root of Clitoris: is made up of 3 masses of erectile tissue bulb of vestibule & right & left crura of clitoris. Because of presence of vagina, bulb of vestibule is divided into two halves & attached to undersurface of urogenital diaphragm & covered by bulbospongiosus muscles. Crura of clitoris correspond to crura of penis and become corpora cavernosa anteriorly. Each remains separate and is covered by an ischiocavernosus muscle.

15 Contents of Urogenital Triangle in Female
Body of Clitoris: consists of two corpora cavernosa covered by their ischiocavernosus muscles. Corpus spongiosum of female is represented by a small amount of erectile tissue from vestibular bulbs to glans. Glans of Clitoris: is a small mass of erectile tissue that caps body of clitoris. It is provided with numerous sensory endings. Glans is partly hidden by prepuce. Blood Supply, Lymph Drainage & Nerve Supply are similar to those of the male penis.

16 Superficial Perineal Pouch in Female
Structures forming root of clitoris & muscles covering them: Bulbospongiosus Muscle: surrounds orifice of vagina and covers vestibular bulbs. Bulbospongiosus muscle reduces size of vaginal orifice and compresses deep dorsal vein of clitoris to assist in clitoris erection. Ischiocavernosus Muscle: on each side covers crus of clitoris. It assists in causing erection of clitoris. Superficial Transverse Perineal Muscles: similar to those of male. Nerve Supply:perineal branch of pudendal nerve.

17 Deep Perineal Pouch in Female
Part of female urethra Part of vagina Sphincter urethrae, pierced by urethra & vagina Deep transverse perineal muscles Internal pudendal vessels & branches Dorsal nerves of clitoris Female Urethra: It is about 4 cm long. It extends from neck of bladder to external meatus, where it opens into vestibule about 2.5 cm below clitoris. It traverses sphincter urethrae and lies immediately in front of vagina. At sides of external urethral meatus are small openings of ducts of paraurethral glands.

18 Superficial Perineal Pouch in Female
Paraurethral Glands: correspond to prostate in male, and open into vestibule by small ducts on either side of urethral orifice. Greater Vestibular Glands: They are a pair of small mucus-secreting glands that lie under cover of posterior parts of bulb of vestibule and labia majora. Each drains its secretion into vestibule by a small duct, which opens into groove between hymen & posterior part of labium minus.

19 Vulva It is the collective name for female external genitalia & includes mons pubis, labia majora & minora, clitoris, vestibule of vagina, vestibular bulb, & greater vestibular glands. Blood Supply: external & internal pudendal arteries on each side. Lymph Drainage: Medial group of superficial inguinal nodes Nerve Supply: Anterior parts of vulva are supplied by ilioinguinal nerves & genital branch of genitofemoral nerve. Posterior parts of vulva are supplied by perineal nerve & posterior cutaneous nerve of thigh.

20 Thank You

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