Unit 8 Anatomy

Anterior division of illiac artery

Inferior gluteal artery Internal pudendal artery (runs with pudendal nerve) Umbilical artery a. The superior vesical artery comes off the umbilical artery to supply the superior portion of the urinary bladder. As the umbilical artery continues onto the anterior abdominal wall, it becomes the obliterated umbilical artery (a.k.a. medial umbilical ligament). Obturator artery a. Runs through the obturator foramen with the obturator nerve 20-30% of the time the obturator artery comes from a different location (external iliac, inferior epigastric or femoral), then it is called an anomalous obturator artery. An anomalous obturator artery can be a problem during surgical repair of a femoral hernia. Inferior vesical artery Middle rectal artery Uterine artery in females- Runs medially in the base of the broad ligament to the junction of the cervix and uterus. It passes superior to the ureter ("Water (ureter) passes under the bridge (uterine artery)"). It will ascend along the lateral margin of the uterus to anastomose with the ovarian artery.

Passing through the inguinal canal

Male - Spermatic cord, genital branch of genitofemoral nerve, and Ilioinguinal nerve (L1) Females - Round ligament of the uterus, genital branch of genitofemoral nerve, and Ilioinguinal nerve (lies lateral to the ligament)

Gubernaculum

a fibrous cord that connects the testis to the anterior abdominal wall at the site of the future deep inguinal ring

Broad Ligament

a fold of peritoneum (2 layers) that encloses the uterus, uterine tubes, round ligament of the uterus, ligament of the ovary, as well as ovarian and uterine vessels and nerves (NOT THE OVARY) . Although it is one continuous structure, for descriptive purposes it is divided into three parts: The mesosalpinx is associated with the uterine tube The mesovarium encloses the ligament of the ovary and attaches to the hilum of the ovary. Note that the ovary is not enclosed within the broad ligament! The mesometrium attaches the uterus to the lateral walls and floor of the pelvis

Urinary bladder

a hollow organ that serves as a reservoir for urine and is known for distensibility. It is located partly superior and partly posterior to the pubic bones. In males, the bladder is superior to the prostate gland and anterior to the rectum/anus. In females, the bladder is anterior to the vagina/uterus. The urinary bladder has bundles of smooth muscle fibers that are known as the detrusor muscle

Scrotum

a loose-fitting cutaneous pouch that contains the testes and part of the spermatic cords. It developed as an outpouching from the lower aspect of the anterior abdominal wall into which the testes and a portion of the attached spermatic cord descended (see Inguinal Canal lecture). On the surface, the scrotum is divided by a ridge or median raphe into two lateral compartments. The raphe continues onto the penis and along the midline of the perineum to the anus. The left compartment of the scrotum hangs lower than the right because the left spermatic cord is longer. Deep to its thin skin (layer 1) is a layer of superficial fascia (dartos fascia, layer 2), the fatty layer of which is replaced by the smooth dartos muscle. The next layers of fascia lie deep to the dartos muscle, 3) external spermatic fascia, 4) cremaster muscle and fascia, 5) internal spermatic fascia, 6) Tunica vaginalis. The visceral layer of the tunica vaginalis is intimately associated with the testes. The parietal layer of the tunica vaginalis lines the inner aspect of the scrotal wall and extends for a short distance into the spermatic cord. The Layers and coverings of the scrotum and testes are comparable to the coverings of the spermatic cord. The coverings of the spermatic cord are derived from its placement through the layers of the abdominal wall. (Table 2.4, Moore Clinical Anatomy has an illustration that correlates the layers in the different anatomical areas)

Vas deferens

a paired conduit via which sperm pass from the tail of the epididymis to the ejaculatory ducts. As a component of the spermatic cord, the vas deferens traverses the superficial and deep inguinal rings to gain access to the inside of the pelvis. Each vas deferens follows a sub-(retro) peritoneal course, exiting the deep ring just lateral to the inferior epigastric artery and travelling medially and inferiorly to pass superior to the ureter ("water under the bridge"). Before it terminates, it enlarges to form the ampulla of the vas deferens; it then narrows and joins the duct of the seminal vesicle to form the ejaculatory duct, which passes through the posterior portion of the prostate to open into the prostatic urethra. A procedure called a vasectomy is a method of sterilization via which the vas deferens is isolated and ligated through a small incision at the superior aspect of the scrotal sac. Following a vasectomy, the ejaculate contains no sperm; the sperm produced by the testes degenerate and are resorbed in the epididymis.

Deep perineal space

contains the urogenital diaphragm, membranous part of the urethra, bulbourethral (Cowper) glands in males Urogenital diaphragm consists of the deep transverse perineal muscle and the sphincter urethrae.

Urination for men

As the bladder expands, visceral afferent fibers traveling with the pelvic splanchnic nerves respond to pressure caused by the accumulation of urine in the bladder. This initiates the conscious urge to urinate. Voiding is accomplished by: Contraction of the smooth muscle of the bladder initiated by the pelvic splanchnic nerves. Relaxation of the pubococcygeus muscle that supports the neck of the bladder. This relaxation places the bladder in direct alignment with the internal urethral orifice. The pubococcygeous muscle is formed by skeletal muscle fibers that are part of the pelvic diaphragm, therefore innervated by somatic motor fibers from the pudendal nerve (S2-S4). Relaxation of the sphincter guarding the internal urethral orifice, allowing urine to flow into the urethra.

Scrotum blood supply

Blood supply to the anterior surface of the scrotum is by way of the external pudendal artery and vein (from the femoral artery and vein, respectively). Blood supply to the posterior surface of the scrotum is by way of the scrotal branches of the internal pudendal artery and vein. Sensory information from the anterior surface of the scrotum is conveyed by the ilioinguinal nerve (L1). Sensory information from the posterior surface of the scrotum is by way of the posterior scrotal nerves, from the superficial perineal branches of the pudendal nerve (S2, 3, 4), and from the pudendal branch of the posterior femoral cutaneous nerve. Lymphatic drainage generally follows the arteries. Vessels drain into the superficial inguinal nodes and nodes associated with the internal iliac artery.

Blood supply of seminal vesciles

Blood supply to the seminal vesicles is from the middle and inferior vesicle arteries, as well as the middle rectal artery. Venous drainage typically parallels the arteries.

External iliac artery branches

Deep iliac circumflex artery Inferior epigastric artery

Spermatic cord

Ductus (vas) deferens Pampiniform plexus of veins (will become the Testicular vein) Testicular lymphatics Testicular artery Artery to the Vas Deferens Cremasteric artery Testicular nerves (Sympathetic) Genital branch of genitofemoral nerve (nerve to the cremaster muscle)

Urogenital triangle

External - skin and fascia. Perineal fascia is called Colle's fascia. It is continuous with Scarpa fascia (anterior abdominal wall) and Dartos fascia (scrotum and penis).

Anal triangle

Ischiorectal fossa Potential space on either side of the anus/rectum and separated from the pelvis by the pelvic diaphragm. It contains ischioanal fat, which allows for distension of the anal canal during defecation, and the pudendal canal. The pudendal canal is found on the lateral wall of the fossa (medial to ischial tuberosity)/, and it transmits the pudendal nerve and internal pudendal blood vessels.

Inguinal Triangle of Hesselbach

It is defined medially by the lateral margin of the rectus sheath (also called the linea semilunaris), laterally by the inferior epigastric vessels, and inferiorly by the inguinal ligament. This is the area between the medial umbilical fold and the lateral umbilical fold (inferior epigastric vessels). The superficial inguinal ring is external to this triangular region. The ring creates a "hole" in the external wall, which creates a weakness. This region is important because it is the site through which direct inguinal hernias occur, especially in the elderly. (see Hernias, below).

Perineum division

It is divided into an anterior triangle called the urogenital triangle (contains the urethra and external genitalia) and a posterior triangle called the anal triangle (contains the anal canal and anus)

Pelvic diaphragm

Levator ani Coccygeus muscles (ischiococcygeus) a thin muscular sheet that constitutes the floor of the pelvic cavity. All pelvic viscera (bladder/urethra, prostate, uterus/vagina, rectum) rest on this muscular sheet and are associated with it at the level of the urinary and anal sphincters. By virtue of this association, the pelvic diaphragm plays a key role in maintaining continence. It is "tonically contracted" to support pelvic viscera, to resist increased intraabdominal pressure and to maintain urinary and fecal continence

Lymphatics

Ovary - The lymphatic vessels draining the ovaries ascend within the suspensory ligament to terminate in the para arotic nodes (located at approximately L1 - L2). Because these nodes are NOT palpable, carcinoma of the ovary is clinically silent and often not detected in a timely fashion. Uterus - The lymphatic vessels of the uterine tubes and of the fundus of the uterus also drain into the para aortic nodes. Some lymphatics follow the course of the round ligament to drain into the superficial inguinal nodes (an important fact to keep in mind when making a differential diagnosis!). The lymphatics of the body of the uterus drain into the external iliac nodes. The lymphatics of the cervix drain into the internal iliac. Vagina - Lymphatic vessels draining the vagina may drain into the external iliac, internal iliac, sacral, and superficial inguinal nodes External Genitalia - Lymphatics of the external genitalia drain into the superficial inguinal nodes

Pelvic splanchic nerve

PREGANGLIONIC PARASYMPATHETIC fibers from S2- S4. They are the only "splanchnic" nerves that are parasympathetic. They contribute to the inferior hypogastric plexus and innervate the descending colon, sigmoid colon, and the viscera of the pelvis and perineum.

Pelvic muscles

Pelvic wall: Obturator internus Piriformis Muscles of pelvic floor (PELVIC DIAPHRAGM) Levator ani Coccygeus muscles (ischiococcygeus)

Defecation for men?

Peristaltic activity initiated by pelvic splanchnic nerves moves waste material through the large bowel. Accumulation of fecal material within the rectum produces distension of its walls, stimulating visceral afferent fibers traveling with the pelvic splanchnic nerves and the perception of "fullness" Elimination of feces is accomplished by: Increased peristalsis Relaxation of the puborectalis muscle and the internal and external anal sphincter muscles. The puborectalis muscle pulls the rectum anteriorly when it contracts, thus aiding in retention of feces; upon relaxation during defecation, the rectum is in alignment with the anal canal.

Urination

Stretch receptors in the detrusor muscle are stimulated when the bladder is full (about 300 mL). Parasympathetic fibers (PELVIC SPLANCHNIC nerves) stimulate contraction of the detrusor muscle and relax the internal urethral sphincter to promote emptying (micturition). PUDENDAL nerve (somatic) innervates the external urethral sphincter (skeletal muscle), which will allow voluntary relaxation and voluntary control of micturition. Sympathetic fibers do the opposite by causing contraction of the internal urethral sphincter to inhibit emptying and to maintain urinary continence.

Vas deferens blood supply

The artery of the vas deferens usually arises as a branch from the superior vesicle artery (sometimes the middle or inferior vesicle arteries). The superior vesical artery branches from the umbilical artery which is from the anterior division of the internal iliac artery. It accompanies the vas throughout its course. Within the scrotum, it usually forms anastomoses with the testicular artery. The ampulla is supplied by the artery of the vas deferens, middle and inferior vesicle arteries, middle rectal artery. Depending on the location of any given segment, venous drainage will be into one or more of the following: the pampiniform plexus, vesical plexus, prostatic plexus.

Gender differences in the pelvis

The bony pelvis of the male is thick and robust. The pelvic inlet is narrow and heart shaped, and the pelvic outlet is comparatively small. The subpubic angle is narrower than that seen in the female The bony pelvis of the female is thin and light by comparison; the "flare" of the ilia is more prominent. The pelvic inlet is wide and round or oval, and the pelvic outlet larger than that in the male. The subpubic angle is wider. The distance between the ischial spines is the narrowest part of the passageway through which a baby's head passes at birth.

Round ligament

The ovaries also begin development in the upper lumbar region, and then they relocate to the lateral pelvic wall. Because the ovaries are attached to the uterus, they do not descend through the inguinal canal. The female gubernaculum connects the ovary and uterus and the uterus to the developing labia majora. It remains in the adult as the ovarian ligament (between the ovary and the uterus) and the round ligament of the uterus (between the uterus and the labia majora)

Blood supply to testes

The paired testicular arteries originate from the abdominal aorta (L2); they are retroperitoneal. They follow a course through the deep and superficial inguinal rings to become part of the spermatic cord. ii. The testicular veins originate from the coalescence of the extensive pampiniform venous plexus, a complex involved in regulating the temperature of the testes. The pampiniform venous plexus may develop varicosities; this condition may be the result of defective valves in the testicular veins. The condition of formation of varicosities is sometimes referred to as a varicocele. Since the varices usually are on the left side, it is thought that enlargement and dilation of the left testicular vein and the left pampiniform venous plexus is due to the relatively high venous pressure in the left renal vein. The left testicular vein drains into the left renal vein (which then drains into the inferior vena cava) but the right testicular vein drains directly into the inferior vena cava. The lymphatic vessels draining the testes traverse the spermatic cord, following the course of the testicular arteries to terminate in the para-aortic or lumbar lymph nodes (L1).

Rectouterine pouch

The peritoneum is then reflected off the posterior surface of the uterus and onto the rectum, forming the

Vesicouterine pouch

The peritoneum leaves the anterior body wall to course over the superior surface of the bladder and continues onto the fundus of the uterus, forming the

Spermatogensis

The production of normal sperm is highly temperature dependent and occurs only below 37 degrees. The location of the testes in the scrotal sac is ideally suited for sperm production, since the intratesticular temperature is about three degrees below that in the abdominal cavity. This temperature is maintained by evaporation from the surface of the scrotum, as well as countercurrent heat exchange (a process that allows cooling of the blood in the testicular arteries by the cooler venous return contained within the numerous vessels of the pampiniform plexus)

Vasculature of the vagina

The uterine artery, a branch of the anterior division of the internal iliac, runs over the ureter (water under the bridge), dividing into ascending, cervical, and descending (vaginal) branches. It supplies the uterus. The ovarian artery, a branch of the abdominal aorta, travels to the ovary within its suspensory ligament. As it crosses the pelvic brim, it lies close to the ureter and anastamoses with terminal branches of the uterine artery. It supplies the ovary, uterine tube, and fundus of the uterus. The internal pudendal artery, usually a branch of the anterior division of the internal iliac, supplies the vagina, and external genitalia. The external pudendal artery, a branch of the femoral, supplies the external genitalia Some of the uterine, and all of the vaginal veins, form a vaginal venous plexus that drains into the internal iliac veins. Like the prostatic venous plexus, it communicates with the external and internal vertebral venous plexi, creating the potential for the spread of infection. Veins from the ovary and distal uterine tube form the ovarian plexus and (ultimately) a single ovarian vein. On the right side, the ovarian vein drains into the IVC. On the left side, the ovarian vein drains into the left renal vein

Vestibular glands

also called Bartholin's glands, are homologous to the bulbourethral glands in males. They consist of two small glands located at the base of each vestibular bulb. These secrete mucus into the vestibule to lubricate the vagina.

Vestibular bulbs

also called clitoral bulbs, are homologous to the bulb of the corpus spongiosum of the penis. They are paired structures of elongated erectile tissue that line the inner surface of the clitoral crura. The opening of the urethra and the vaginal opening lie between the two vestibular bulbs. In response to sexual arousal, the vestibular bulbs fill with blood, causing erection

Coccygeus

also known as ischiococcygeus, lies deep to the sacrospinous ligament. It's muscular fibers run from the ischial spines to the inferior sacrum and coccyx. It also supports and raises the pelvic floor.

Perineal membrane

also known as the inferior fascia of the urogenital diaphragm

Seminal vesicles

are paired seminal vesicles, highly convoluted tubular glands located lateral and parallel to the ampulla of the vas deferens on the lower posterior wall of the bladder. They are subperitoneal and separated from the rectum by Denonviller's fascia, a thick fibromuscular layer of connective tissue that is traversed by bundles of smooth muscle that is continuous with the stroma of the prostate. The alkaline component of the fluid produced in the seminal vesicles contains fructose and choline. These two constituents are used for markers. Fructose for the forensic determination of rape. Choline crystals provide the basis to determine the presence of semen. Fructose is a primary source of nutrients for the sperm, as well as prostaglandins, ascorbic acid, simple sugars and amino acids. Contraction of the smooth musculature during ejaculation propels these components in a relatively large volume of secretory fluid into the ejaculatory ducts and flushes the sperm out of the urethra. The seminal vesicles contribute the largest volume of fluid to the ejaculate (approximately 70%)

Testes

are paired, ovoid glands. While both are the same size, the left testis is located lower in the scrotum than the right. Each testis is enclosed by a thick covering of connective tissue, the tunica albuginea. On the posterior surface of the testis, the tunica albuginea is thickened and specialized to form the mediastinum testis. In this region of the mediastinum, vessels and ducts enter and leave the testes. The head of the epididymis begins here; the tail of the epididymis and the first part of the vas deferens are attached by loose connective tissue to the lower posterior pole of each testis. The mediastinum testis gives rise to fibrous septae that penetrate the substance of the testis and subdivide it into a series of compartments or lobules. Each lobule contains between one and four seminiferous tubules, the cells of which produce spermatozoa. A series of interconnected intratesticular ducts convey the spermatozoa and some fluid from the seminiferous tubules to the epididymis, a tightly coiled tube that is the site of maturation and storage for sperm. The distal portion or tail of the epididymis becomes the ductus (vas) deferens. Sperm travel superiorly in the vas deferens, which, as part of the spermatic cord, traverses the superficial and deep inguinal rings. Once inside the pelvis, the vas deferens courses over the pelvic brim and descends inferiorly to join the duct of the seminal vesicle, forming the ejaculatory duct. In addition to spermatozoa, the testes make testicular fluid and the interstitial cells of Leydig in the interstitial tissue outside the seminiferous tubules make testosterone and other androgens.

Labia Minora

are two small folds of skin, without fat content, located between the labia majora. In the region of the clitoris, each minor labium divides: The upper (lateral) portion meets its counterpart of the opposite side to form the repuce of the clitoris, a small hood that projects over the glans clitoris. The lower (medial) portions fuse below the clitoris to form the frenulum of the clitoris. The labia minora enclose the vestibule of the vagina (urogenital sinus), into which the vagina, urethra, and ducts of the greater vestibular glands open. On each side of the urethral orifice are the openings of the paraurethral glands, homologues of the prostate. In young females, a thin mucous membrane, the hymen, surrounds and/or covers the vaginal orifice

Pelvic girdle

bony pelvis that connects the vertebral column with femurs; part of the appendicular skeleton

Mons Pubis

consists of tissue that covers and protects the pubic bone. After puberty, this will become covered in pubic hair.

Ovarian plexus

contains POSTGANGLIONIC SYMPATHETIC fibers from the thoracic and lumbar splanchnic nerves and visceral afferent fibers. The sympathetic fibers regulate blood flow. Because the ovary originated on the posterior abdominal wall (prior to its descent into the pelvic bowl), most of the nerves supplying it come from spinal levels T10 - T11. Thus, pain from the ovary is referred to this area via visceral afferents accompanying sympathetic fibers. The pain that results from distention and pressure caused by a ruptured ovarian cyst may be mistaken for appendicitis because the dermatomes involved are identical.

Superficial perineal space

contains superficial perineal muscles and greater vestibular (Bartholin) glands in females Ischiocavernosus which inserts into crus of penis or clitoris (corpus caverosum) Bulbospongiosus (and bulb of the penis in males or vestibular bulb in females) which inserts into corpus spongiosum Superficial transverse perineal muscle Perineal body (central tendon of perineum)

Anal canal

continuous with the rectum below the pelvic diaphragm and ends at the anus. The upper 2/3 is the visceral portion and the lower 1/3 is the somatic portion. The separation between the two portions is called the pectinate (dentate) line. The veins of the visceral portion drain into the portal venous system, the sensory is visceral afferent through pelvic splanchnic nerves, and this is the location that internal hemorrhoids form. The veins in the somatic portion drain into the caval (IVC) system, the SENSORY innervation is somatic from the PUDENDAL nerve, and this is the location that external hemorrhoids can form. The internal anal sphincter (smooth muscle in the lower part of the rectum innervated by pelvic splanchic nerves) is separated from the external anal sphincter (skeletal muscle) by an intermuscular groove called Hilton white line.

Sacrospinous and sacrotuberous ligaments

convert the greater and lesser sciatic notches (features of the hip bones) into the greater and lesser sciatic foramina

Penis

divided into a root region, the body or shaft region and the glans. The root of the penis consists of the bulb of the penis along the midline, and the crus (crura = plural) of the penis, one on either side of the bulb. The root lies within the superficial perineal space/pouch, immediately inferior to the deep perineal space and perineal membrane. The bulb of the penis is a midline structure; it is traversed by the urethra and is covered by the bulbospongiosus muscle at its origin. It continues forward to become the corpus spongiosum, on the ventral portion of the body of the penis. The crura or "legs" of the corpus cavernosum attach to the bilateral ischiopubic rami. The crura are spongy cylinders that are covered transiently by the ischiocavernosus muscles. The crura are the origin of the true erectile tissue of the paired corpora cavernosa. They project toward the midline, increasing in size as they do so; they fuse with one another, forming the corpora cavernosa of the dorsum of the body (shaft) of the penis.

Inguinal ligaments

extend from the anterior superior iliac spines to the pubic tubercles.

Rectum

extends from the sigmoid colon to the anal canal within the pelvis. It follows the curvature of the sacrum and coccyx. The ampulla just above the pelvic diaphragm stores feces.

Perineum

external area between the thighs and buttocks extending from the pubis to the coccyx. It lies below the pelvic diaphragm (pelvic floor), and is thus separated from, and inferior to, the true pelvis. The perineum consists of two defined "pouches", a superficial one and a deep one, that contain the anal canal, urethra, and external genitalia (penis and scrotum in males and vulva in females)

Body/shaft of the penis

f the penis is comprised of three cylinders: the dorsal paired corpora cavernosa and the single, ventrally positioned corpus spongiosum. These are enclosed within a tube of deep fascia (Buck's fascia), which also surrounds the deep dorsal vein, the paired dorsal arteries and the deep dorsal nerves located on the dorsal surface of the penis. The two corpora cavernosa contain true erectile tissue (large venous sinuses). The single corpus spongiosum surrounds the urethra The suspensory ligament of the penis, also made up of deep fascia, originates as a single entity from the pubic symphysis. It splits to form a sling that supports the transitional area between the root and the body of the penis. The fundiform ligament, a condensation of subcutaneous connective tissue extends from the linea alba. After it splits to surround and support the penis, it continues inferiorly to terminate as the scrotal septum.

Lacunar ligament

fibers from the inguinal ligament that run deep and posterior to attach to the superior pubic ramus lateral to the pubic tubercle

Conjoint tendon

formed by the combined fibers of the internal abdominal oblique and the transversus abdominis muscles as they come together to insert on the pubic bone. It is located immediately posterior to the superficial inguinal ring, and therefore strengthens it.

Sacral plexus

formed by the ventral rami of L4 - S4. Its branches include superior gluteal nerve (L4-S1), inferior gluteal nerve (L5-S2), sciatic nerve (L4- S3), nerve to obturator internus (L5-S2), nerve to quadratus femoris (L5-S1), nerve to piriformis (S2, S2), posterior femoral cutaneous nerve (S1-S3), pudendal nerve (S2 - S4), nerve to levator ani and coccygeus (S3-S4), pelvic splanchnic nerves (S2-S4).

Pudendal nerve in females

formed within the pelvis; exits the gluteal region via the greater sciatic foramen and then immediately reenters via the lesser sciatic foramen. It originates from ventral rami of spinal nerves S2-S4 and contains somatic motor and somatic sensory fibers. It branches into: Inferior Rectal Nerve - supplies the external anal sphincter, and the skin around the anus Perineal Nerve, which further divides into: Superficial - Posterior Labial Nerves - supplies sensory to the labia majora and the vestibule of the vagina Deep muscular branches to the bulbospongiosus, ischiocavernous, and sphincter urethrae muscles Dorsal Nerve of the Clitoris - sensory to the glans clitoris and the skin

Inguinal canals

found on the anteroinferior aspect of the abdominal wall, immediately above the inguinal ligaments. Their formation, during development, is intimately related to the descent of the testes and formation of the spermatic cords, in males. The clinical significance of the inguinal canals has to do with innate weaknesses in the abdominal wall at the level of the inguinal canal and the potential for hernia formation.

Pelvic outlet

inferior pelvic aperture is a diamond-shaped aperture defined by the pubic symphysis anteriorly, the ischial tuberosities and sacrotuberous ligaments laterally, and the sacrum and coccyx posteriorly. The pelvic and urogenital diaphragms close it inferiorly.

Defecation

initiated by distention of the rectum, which is sensed by the PELVIC SPLANCHNIC nerves. Peristalsis in the rectum increases (parasympathetic from pelvic splanchnic nerves), and puborectalis relaxes to decrease the angle between the rectum and the anal canal. Internal and external anal sphincters relax to allow passing of the feces. External anal sphincter (skeletal muscle) is innervated by PUDENDAL nerve, which allows for voluntary control over defecation.

Clitoris

is homologous to the penis, and consists of a small cylindrical structure. It originates as two crura that enlarge to become erectile tissue: corpora cavernosa clitoridis. The paired corpora are the body of the clitoris; the glans clitoris is at its distal extent and has a highly developed nerve supply

Labia Majora

is homologous to the scrotal sac. These are prominent longitudinal folds of skin extending posteriorly from the mons pubis, and which consist of fat and fibrous connective tissue into which the round ligament of the uterus extends. The two folds are joined anteriorly by the anterior labial commissure. They are supplied by branches of the EXTERNAL and INTERNAL PUDENDAL ARTERIES and receive sensory fibers from branches of the ILIOINGUINAL (anterior labial) and PUDENDAL (posterior labial) nerves. Labia majora contains the terminations of the round ligament of the uterus

Pectineal ligament (of Cooper)

lateral fibers of the lacunar ligament that run along the pectin pubis.

Uterovaginal plexus

located at the cervicovaginal junction. It contains postganglionic sympathetic, preganglionic parasympathetic, and visceral afferent fibers. Sympathetic fibers are vasomotor; in addition, they initiate contraction of uterine and vaginal musculature. Parasympathetic fibers are secretomotor; in addition, they inhibit muscular contraction. Visceral afferent fibers travel with both sympathetic and parasympathetic fibers. Pressure, stretching, and distensions are all perceived as painful stimuli. Afferents from the fundus and body of the uterus travel with the sympathetic fibers to the spinal levels T11-L2. Afferents from the cervix and upper portion of the vagina travel with the pelvic splanchnics to spinal levels S2-S4.

Opening of the urethra for females

located just inferior to the clitoris. The female urethra is much shorter than in the males (about 1.5 inches vs. 8 inches). Both the shortened length and the proximity of the urethra to the anal opening puts females at a much higher risk of bladder infections than males.

Pelvic diaphragm musculature

made up of the levator ani and coccygeus muscles. This diaphragm has two hiatuses (gaps): anteriorly, the urogenital hiatus allows passage of the urethra and vagina (in females) from the pelvic cavity into the perineal region; posteriorly, the rectal hiatus, allows passage of the anal canal.

Pelvic Cavity

most inferior portion of abdominopelvic cavity. It houses all the viscera associated with genitourinary functions, their innervation and blood supply. The peritoneum covering the walls of the abdominal cavity continues into the pelvis, and it is reflected over the superior aspects of the pelvic viscera (rectum, urinary bladder, and internal genitalia). Structures that lie beneath the peritoneum are considered to be subperitoneal (infraperitoneal).

Ureters

muscular tubes 25-30 cm long that carry urine from the kidneys to the urinary bladder. They are retroperitoneal, and they enter the pelvis by crossing over the common iliac artery and over the pelvic brim. They run along the lateral pelvic wall until they turn anterior and medial just superior to the levator ani to enter the urinary bladder through the floor of the bladder. The ureter runs under the UTERINE ARTERY in females ("water runs under the bridge"), and it could potentially be damaged during a hysterectomy

Glans

of the penis is the most distal, expanded portion of the corpus spongiosum. This is the site of the opening of the urethra, the external urethral meatus.

Erection and ejaculation

rection is a vascular event initiated by tactile, visual, olfactory and emotional/psychological stimuli, all of which generate afferent input into the central nervous system. Primary direct afferent innervation is from branches of the pudendal nerve. The dorsal nerve of the penis. The ilioinguinal nerve also contributes afferent sensory fibers to the base of the penis. Psychogenic input may also contribute to initial stages of an erection. Efferent signals sent via the pelvic splanchnic nerves (distributed with branches of the internal pudendal artery) initiate vasodilation of the spongy erectile tissue and stimulation of secretory activity in the bulbourethral glands. Pelvic splanchnic nerves have parasympathetic component fibers and arise from S2-4 Spinal cord. Continued afferent input results in activation of sympathetic fibers (lumbar splanchnic nerves carrying preganglionic sympathetic fibers from the L1-L2 spinal segments synapse in the inferior mesenteric and hypogastric ganglia; postganglionic sympathetic fibers distribute to pelvic viscera either directly or via branches of the internal iliac artery). This activation stimulates contraction of smooth musculature of the ducts of the epididymis, vas deferens, prostate and seminal vesicles. The contents of these organs/glands are released into the prostatic urethra, a process called emission. Semen enters the penile urethra and is expelled by rhythmic contractions of the bulbospongiosus and ischiocavernosus muscles (pudendal nerve, somatic motor fibers), the process of ejaculation. Reflux of the ejaculate into the bladder is prevented by the contraction of the internal urethral sphincer

Male urethra

s a fibromuscular tube that conducts urine from the bladder and semen from the ejaculatory ducts to the exterior of the body. It originates at the bladder neck and ends at the external urethral meatus of the glans penis. It is often divided into three segments depending on the structures that invest it: prostatic urethra, membranous urethra and spongy/penile urethra. The prostatic urethra traverses the prostate. It originates at the bladder neck and ends at the membranous urethra. It is retropubic, bounded superiorly by the bladder and supported inferiorly by the external urethral sphincter and the perineal membrane. One of the functions of the prostatic urethra is to transmit semen into the common genitourinary tract. The urethral crest is an elevated ridge, centrally located on the posterior wall; midway along its length the crest is enlarged and prominent, forming the seminal colliculus. The utricle is a small blind pouch located in the middle of the seminal colliculus; the ejaculatory ducts terminate by opening on either side of the utricle. The prostate is made up of 30-50 tubuloalveolar glands. These glands open up via ducts into the prostatic sinuses (depressions that flank the right and left sides of the urethral crest). Prostatic secretions form approximately 30% of the ejaculate. They are rich in citric acid, acid phosphatase and zinc. The secretions facilitate fertility, enhance sperm motility and help adjust the pH of the urethra. The membranous urethra is short and interconnects the prostatic and spongy urethra (bulb of the penis). It begins immediately below the apex of the prostate and passes through the deep perineal space/pouch and the perineal membrane (hence the name). The bulbourethral (Cowper's) glands lie on either side of its posterodistal extent; they are embedded in the musculature of the external urethral sphincter. In response to sexual arousal they produce a mucous-like glandular secretion that enters the spongy urethra (bulb) and lubricates it. The penile or spongy urethra is the longest part of the male urethra and is enclosed by the corpus spongiosum of the penis. It starts below the deep perineal space and passes anterosuperiorly to the front of the pubic symphysis.

Pudendal nerve

s the main SOMATIC MOTOR of the PERINEUM and SENSORY to EXTERNAL GENITALIA. It travels with the internal pudendal vessels through the greater sciatic foramen then crosses the ischial spine and enters the perineum through the lesser sciatic foramen. It then travels through the pudendal canal along the lateral wall of the ischioanal fossa medial to the ischial tuberosity. It will GIVE to the INFERIOR RECTAL NERVE, the PERINEAL NERVE, and the DORSAL NERVE of the PENIS/CLITORIS.

Urethra

s the structure that carries urine to the exterior. It begins in the floor of the bladder. The orifices for the two ureters and the internal urethral orifice are found at the angles of the trigone of the bladder, a triangular area on the floor of the urinary bladder. The internal sphincter surrounds the internal urethral orifice. - passage for urine from the bladder to the exterior. In males, it is about 20 cm long and also allows for passage of semen. It consists of three portions - prostatic (through the prostate gland), membranous (through the deep perineal pouch, UG diaphragm, and perineal membrane) and spongy/penile (through the bulb of the penis and corpus spongiusum). In females, the urethra is about 4 cm long.

Pelvic inlet

superior pelvic aperture is defined by drawing a line (iliopectineal line) from the superior aspect of the pubic symphysis, anteriorly, to the sacral promontory, posteriorly; this is also known as the pelvic brim. The region above this line is defined as the greater/ false pelvis. The lesser/true pelvis lies below it.

Posterior division of iliac artery

supplies the posterior pelvic wall and the gluteal region. Iliolumbar artery Lateral sacral artery Superior gluteal artery Arteries are paired with a vein of the same name that drains the area. The veins converge into the internal and external iliac veins then into the right and left common iliac veins then form the inferior vena cava.

Greater/False Pelvis

surrounded by superior portion of pelvic girdle (primarily the ala of ilium and iliac fossa). It is above the pelvic inlet (superior pelvic aperture - pelvic brim - iliopectineal line), and it contains abdominal organs (small intestines, cecum, vermiform appendix, and sigmoid colon).

Lesser/True Pelvis

surrounded by the inferior pelvic girdle. It is below the pelvic inlet and above the pelvic outlet (inferior pelvic aperture). It contains the reproductive organs, bladder, and rectoanal canal. The pelvic and urogenital diaphragms close it inferiorly.

Cremasteric reflex

the cremaster muscle (innervated by the genital branch of the GENITOFEMORAL NERVE, L1-L2) reflexively draws the testes up into the scrotum, especially when it's cold. Conversely, with warmer temperatures, the cremaster muscle relaxes and the testes descend deep into the scrotum. The main objective of these responses is to closely regulate the temperature of the testes in order to ensure an adequate environment for spermatogenesis the cremasteric reflex can be elicited by lightly stroking the skin of the upper medial thigh downwards (sensory innervation from the femoral branch of the genitofemoral nerve), causing the cremaster muscle (motor innervation from the genital branch of the genitofemoral nerve) on that side to contract, raising the testicle on that same side.

Pelvic pain line

the inferior limit of the peritoneum. Visceral afferent conveying pain for organs above the line (intraperitoneal organs) accompany sympathetic fibers. Visceral afferent conveying pain for organs below the line (pelvic organs, distal sigmoid colon and rectum) accompany parasympathetic fibers, i.e. pelvic splanchnic nerves (S2-S4).

Prostate

the largest of the male accessory sex glands (the others being the seminal vesicles and the bulbourethral glands); it is triangular in shape, about the size of a chestnut in young men. It lies approximately 2 cm behind (posterior to) the pubic symphysis and forms an inverted pyramid: the broad base is at the neck of the urinary bladder, inferior to the internal urethral sphincter; the narrow, pointed apex is directed caudally and is superior to the external urethral sphincter. The isthmus or anterior lobe of the prostate is made up primarily of muscular fibers that are continuous with those of the external urethral sphincter. This lobe is anterior to the urethra. The posterior surface of the prostate is in front of the ampulla of the rectum. The right and left lobes (roughly correspond to the peripheral zones) of the prostate are subdivided into lobules. One of the most important of these, clinically, is the inferoposterior lobule, which is located inferior to the urethra and is palpable upon rectal examination.

Levator ani

three main groups of muscle fibers: the iliococcygeus (most laterally), pubococcygeus and puborectalis (most medially) muscles. They all run posteriorly from the body of the pubis and insert on the coccyx and anococcygeal raphe. It supports and raises the pelvic floor. Some of the fibers of the pubococcygeus muscle interdigitate with dense fascia surrounding and supporting the urethra and prostate or vagina in a slinglike fashion. Often these specific muscle fibers are referred to as the pubourethralis, puboprostaticus or pubovaginalis, respectively, and they play a key role in maintaining urinary continence. The puborectalis muscle, the medial portion of the levator ani, originates from the posterior portion of the pubic bones, coursing posteriorly to loop around the anorectal junction. Right and left puborectalis muscles unite behind the anorectal junction (approx. at level of S3) to form a muscular sling. At this site, its fibers are interwoven with those of the internal and external anal sphincters, playing a key role in fecal continence