Subcutaneous Tissue

The layer collectively referred to by most surgeons as subcutaneous tissue is actually made up of superficial (Camper’s) and deep (Scarpa’s) fascia. These loose, fatty connective tissue layers contain the superficial abdominal wall vessels and are the most common site of postoperative wound infections.

Muscles and Transversalis Fascia

The abdominal wall is made up of five pairs of muscles. In the midline, the rectus abdominis muscles extend along the whole length of the front of the abdomen from the xiphoid process and costal cartilages of the fifth through the seventh ribs to the pubic crest and pubic symphysis. This broad strap muscle is divided into four segments by three fibrous intersections attached to the anterior, but not the posterior, rectus sheath. This allows the inferior (deep) epigastric vessels to pass along the posterior surface of the muscle without encountering a barrier.

The pyramidalis muscle is a small triangular muscle that lies in front of the rectus abdominis at the lower part of the abdomen and is contained within its fascial sheath. It arises from the front of the pubic symphysis and the anterior pubic ligament bilaterally and inserts into the linea alba, between the umbilicus and pubic symphysis. This muscle is commonly absent on one or both sides.

There are three sets of lateral muscles. The external oblique muscle is the most external and arises from the lower eight ribs. The fibers run downward and forward to form aponeuroses that extend anteriorly. Aponeuroses are fibrous membranes resembling flattened tendons that bind muscles to each other or bones. Beneath the external oblique muscle, the internal oblique muscle arises from the lumbar fascia, the iliac crest, and the lateral two thirds of the inguinal ligament and runs upward and forward to form aponeuroses. The most internal of the lateral muscles is the transversus abdominis muscle. It arises from the lateral third of the inguinal ligament, from the anterior three fourths of the iliac crest, from the costal cartilages of the sixth through eighth ribs, interdigitating with the diaphragm, and from the lumbodorsal fascia and ends in front in a broad aponeurosis. Deep to the transversus abdominis muscle is a continuous layer of specialized investing fascia that lines the abdominal cavity and continues into the pelvic cavity, the transversalis fascia.

Deep Fascia of the Rectus Sheath and Extraperitoneal Fascia

The rectus abdominis muscle is enclosed anteriorly and posteriorly by fascia known as the rectus sheath. This sheath is formed from fusion of the aponeuroses of all three lateral abdominal muscles. These aponeuroses fuse lateral to the rectus abdominis muscles as the linea semilunares and again in the midline as the linea alba, which extends from the xiphoid process to the pubic symphysis. The arcuate line is a tranverse line midway between the umbilicus and pubic symphsis. Above this line, the aponeuroses of the lateral muscles split to enclose the rectus muscle both anterior and posterior; below this line these aponeuroses all pass anterior to the rectus muscle. Inferiorly, the aponeuroses of the external oblique inserts into the anterior superior iliac spine and stretches over to the pubic tubercle, forming the inguinal ligament.

The inguinal canal is about 4 cm long and runs parallel to the inguinal ligament. The inguinal canal has an anterior wall formed by the aponeurosis of the external oblique, an inferior wall formed by the inguinal ligament, a superior wall formed by arching fibers of the internal oblique and transversus abdominis muscles, and a posterior wall formed by the transversalis fascia. A defect, or more precisely a tubular evagination, of the transversalis fascia forms the deep inguinal ring, through which the round ligament enters the inguinal canal. This ring lies midway between the anterior superior iliac spine and the pubic symphysis. Medial to the deep inguinal ring are the inferior epigastric vessels. The opening of the aponeurosis of the external oblique superior to the pubic tubercle is the superficial inguinal ring. Through it the round ligament, the terminal part of the ilioinguinal nerve, and the genital branch of the genitofemoral nerve exit the inguinal canal (see Fig. 7-1).

Deep to the transversalis fascia and the rectus sheath is a layer of connective tissue separating the transversalis fascia from the parietal peritoneum, the extraperitoneal fascia. This layer contains varying amounts of fat, lines the abdominal cavity and is continuous with a similar layer lining the pelvic cavity. Viscera in the extraperitoneal fascia are referred to as retroperitoneal.

Parietal Peritoneum

The parietal peritoneum is a one-cell thick membrane that lines the abdominal cavity and in certain places reflects inward to form a double layer of peritoneum called the mesentery.

Nerves

There are four categories of nerves that supply the anterior abdominal wall, each of which contain both motor and sensory fibers. The thoracoabdominal nerves originate from T7–T11, travel anteroinferiorly between the internal oblique and transversus abdominis muscles, and have the following distribution:

The subcostal nerves originate from T12 and travel anteroinferiorly between the internal oblique and transversus abdominis muscles to innervate the abdominal wall inferior to the umbilicus.

The iliohypogastric nerve and ilioinguinal nerve both originate from L1. Like the thoracoabdominal and subcostal nerves, these nerves begin their course anteroinferiorly between the internal oblique and transversus abdominis muscles. However, at the anterior superior iliac spine, they both pierce the internal oblique muscle to travel between the internal and external oblique muscles. The iliohypogastric nerves innervate the abdominal wall lateral and inferior to the umbilicus. The ilioinguinal nerve enters the inguinal canal and emerges from the superficial inguinal ring and is sensory to the labia majora, inner thigh, and groin.

These nerves are particularly at risk in lower abdominal incisions, which are the most common causes of abdominal wall pain as a result of nerve entrapment by suture or scar tissue.¹ For this reason, knowledge of the course of the ilioinguinal and iliohypogastric nerves in the anterior abdominal wall can help avoid injury during laparotomy and laparoscopic surgery. Data from cadaveric studies suggest that injury to these nerves can be minimized during laparoscopy by making transverse skin incisions and placing laparoscopic trocars at or above the level of the anterior superior iliac spine.² In cases of chronic abdominal pain caused by these nerves, an injection of local anesthetic at a site approximately 3 cm medial to the anterior superior iliac spine will often provide relief.

Blood Vessels

The major vessels in the anterior abdominal wall can be divided into deep and superficial vessels (Fig. 7-2).³ The superficial vessels include the superficial epigastric and the superficial circumflex iliac vessels. These vessels are branches of the femoral artery and vein. They course bilaterally through the subcutaneous tissue of the abdominal wall, branching as they proceed toward the head of the patient.

Figure 7-2 Anterior abdominal wall blood vessels.

(Modified from Hurd WW, Bude RO, DeLancey JOL, Newman JS: The location of abdominal wall blood vessels in relationship to abdominal landmarks apparent at laparoscopy. Am J Obstet Gynecol 171:642–646, 1994.)

To avoid vessel injuries, these superficial vessels can often be seen before secondary laparscopic port placement by transillumination of the abdominal wall using the intra-abdominal laparoscopic light source.³ Injury to these vessels during trocar placement can result in a palpable hematoma that will be found to be located anterior to the fascia on computed tomography (CT) scan.⁴ In unusual cases, the hematoma can dissect down into the labia majora.

The deep vessels consist of the inferior epigastric artery and vein, which are also bilateral. These vessels originate from the external iliac artery and vein and course along the peritoneum until they dive deeply into the rectus abdominis muscles midway between the pubic symphysis and the umbilicus. The inferior epigastric vessels are the lateral border of an inguinal triangle called Hesselbach’s triangle. This triangle is bound medially by the rectus abdominis muscle and inferiorly by the inguinal ligament.

The course of the inferior epigastric vessels can often be visualized at laparoscopy as the lateral umbilical fold because of the absence of the posterior rectus sheath below the arcuate line (Fig. 7-3).⁵ Injury to these vessels can result in life-threatening hemorrhage that must be quickly controlled by occluding the lacerated vessels with electrosurgery or precisely placed sutures.

Figure 7-3 Laparoscopic view of peritoneal landmarks and inferior epigastric vessels. The left round ligament is seen entering the deep inguinal ring. Medial to the round ligament at the deep inguinal ring are the inferior epigastric vessels. The peritoneal fold is referred to as the lateral umbilical fold. The peritoneal fold seen medial to the vessels has the obliterated umbilical artery and is referred to as the medial umbilical fold.

If these vessels cannot be visualized (usually because of excess tissue), trocars should be place approximately 8 cm lateral to the midline and 8 cm above the pubic symphysis.³ On the right side of the abdomen, this point approximates McBurney’s point, located one-third the distance from the anterior superior iliac spine to the umbilicus. The corresponding point on left is sometimes referred to as Hurd’s point.

Peritoneal Landmarks

Peritoneal Folds

Several useful landmarks can be used to guide the laparoscopic surgeon to avoid injury to important retroperitoneal structures. Two midline and two bilateral pairs of peritoneal folds can usually be seen on the anterior abdominal wall at laparoscopy (Fig. 7-4). The falciform ligament, which is the remnant of the ventral mesentery and contains the obliterated umbilical vein in its free edge, can be seen in the midline above the umbilicus extending to the liver. The median umbilical fold, which contains the urachus, can usually be seen in the midline below the umbilicus extending to the bladder. Although the urachus normally closes before birth, it should be avoided during secondary trocar placement, both because it can be difficult to penetrate and in rare cases can remain patent to the bladder.

Figure 7-4 The peritoneal reflections onto the urachus (median umbilical ligament), umbilical artery (medial umbilical ligament), and inferior epigastric vessels (lateral umbilical fold) are seen. The two important peritoneal pouches are seen between pelvic organs.

(From Drake RL, Vogl W, Mitchell AWM: Gray’s Anatomy for Students. Philadelphia, Elsevier, 2005, p 416, Fig. 5-58A.)

On each side of the urachus lie the medial umbilical folds. These landmarks contain the obliterated umbilical arteries and extend from the umbilicus to the anterior division of the internal iliac artery. Lateral to these, the lateral umbilical folds can be seen in 82% of patients.⁵ These are the most important structures to the laparoscopist, because they contain the inferior epigastric vessels and knowing their location can help the laparoscopist avoid injury to these large vessels during placement of secondary laparoscopic ports.

Peritoneal pouches normally exist between the pelvic organs (see Fig. 7-4). The vesico-uterine pouch is located anteriorly between the uterus and bladder. The ventral margin of the bladder can be visualized in approximately half of patients behind the anterior abdominal wall peritoneum and is important for secondary trocar placement, especially after previous abdominal surgery.⁵ The dorsal bladder margin can often be visualized on the anterior uterus and is used as a landmark during dissections during hysterectomy.

The recto-uterine pouch (pouch of Douglas) is located between the anterior surface of the rectum and the posterior surface of the vagina, cervix, and uterus. Endometriosis often involves the recto-uterine pouch and in severe cases, completely obliterates it. Inferiorly, an extraperitoneal fascial plane called the rectovaginal septum extends from the recto-uterine pouch to the perineal body. It lies between the posterior wall of the vagina and anterior wall of the rectum, and when involved with endometriosis can be felt on pelvic examination as nodularity.

Muscles

Several muscles of importance in the posterior abdominal wall lateral to the vertebral column can be seen lateral to the pelvic inlet. The diaphragm forms the roof of the abdomen and extends down to form the most superior aspect of the posterior abdominal wall. The psoas major muscle runs longitudinally from the transverse processes of the upper lumbar vertebrae to the lesser trochanter of the femur and makes up a large part of the posterior and medial wall. The tendon of the psoas minor muscle can be seen anterior to the psoas major muscle during dissection near the external iliac vessels. The quadratus lumborus muscle runs lateral and posterior to the psoas major muscle from the transverse process of the lumbar vertebrae and ribs to the iliac crest. The iliacus muscle spans the iliac fossa. Finally, the piriformis muscle begins at the anterior surface of the sacrum and passes through the greater sciatic foramen to attach to the greater trochanter of the femur. It lies immediately beneath the internal iliac vessels.

Nerves

Multiple nerves enter or transverse the pelvic sidewalls. Deep nerves of the pelvis, such as the superior and inferior gluteal nerves, supply several of the pelvic muscles but are not visible during reproductive surgery. Likewise, the obturator nerve traverses the pelvis. The obturator nerve originates at spinal cord levels L2–L4 and descends in the psoas major muscle until the pelvic brim, when it emerges medially to lie on the obturator internus muscle lateral to the internal iliac artery and its branches (Figs. 7-5 and 7-6). It descends on the obturator internus muscle to enter the obturator canal and exits in the thigh. It is sensory to the medial side of the thigh and motor to the muscles in the medial compartment of the thigh (the adductor muscles). It can easily be seen during pelvic sidewall dissections for endometriosis or lymph node dissection.

Figure 7-5 The obturator nerve is seen coursing over the pelvic brim when it emerges medially to lie on the obturator internus muscle lateral to the internal iliac artery and its branches. The anterior trunk of the internal iliac artery gives off several branches: a common trunk that typically divides into the umbilical artery and uterine artery, the obturator artery, the internal pudendal artery, the vaginal artery, and the middle rectal artery. The anterior trunk terminates as the inferior gluteal artery. The umbilical artery gives off the superior vesical artery.

(From Drake RL, Vogl W, Mitchell AWM: Gray’s Anatomy for Students. Philadelphia Elsevier, 2005, p 428, Fig. 5-64.)

Figure 7-6 Laparoscopic view. Two branches of the anterior trunk of the left internal iliac artery, the uterine artery and the umbilical artery, are seen medial to the left obturator nerve. The nerve lies on the obturator internus muscle. The relationship of the vessels with the ureter (retracted by the instrument) is seen.

The genitofemoral nerve (from spinal cord levels L1 and L2) lies on the anterior surface of the psoas muscle (Fig. 7-7). It has two branches, the femoral and genital. The femoral branch enters the thigh under the inguinal ligament, and the genital branch enters the inguinal canal. The genitofemoral nerve is sensory to the skin over the anterior surface of the thigh. Injury to this nerve is seen after appendectomy or when the fold of peritoneum from the sigmoid colon to the psoas muscle is incised.

Figure 7-7 The peritoneum over the left external iliac artery and psoas muscle has been removed. The instrument is on the left external iliac artery and points to the left genitofemoral nerve that is splitting into the two branches. Lateral to the nerve is the left psoas minor tendon.

The femoral nerve (spinal cord levels L2–L4) is not usually seen during pelvic surgery but may be injured by compression at laparotomy. It is a branch of the lumbar plexus and descends within the substance of the psoas major muscle, emerging at its lower lateral border. The nerve continues between the psoas and iliacus muscles and then passes posterior to the inguinal ligament to supply the skin of the anterior thigh region as well as many of the muscles in the anterior compartment of the thigh. Prolonged pressure on the psoas muscle may cause temporary or permanent damage to the femoral nerve. For this reason, caution must be taken when using self-retaining retractors to make certain that the lateral blades do not put pressure on the pelvic sidewalls.

The sacral and coccygeal nerve plexuses are located anterior to the piriformis muscle beneath the branches of the internal iliac artery. The most important nerves in this area are the sciatic and pudendal nerves. The sciatic nerve (from spinal cord levels L4–S3) lies anterior to the piriformis muscle and exits the pelvic cavity through the greater sciatic foramen inferior to the muscle. Anterior to the sciatic nerve are many branches of the internal iliac artery. The pudendal nerve (from spinal cord levels S2–S4) is also found anterior to the piriformis muscle and exits the pelvic cavity inferior to the piriformis muscle through the greater sciatic foramen. It courses around the sacrospinous ligament and ischial spine, through the lesser sciatic foramen, and into the perineum. Endometriosis may involve the sciatic nerve at this level and cause pain syndrome related to the course of this nerve.

Blood Vessels

The major blood vessels are perhaps the most important structures of the pelvis (see Fig. 7-5). Successful pelvic surgery requires a thorough understanding of their anatomy. The aorta bifurcates at the level of L4 into the left and right common iliac arteries. The common iliac artery passes laterally, anterior to the common iliac vein to the pelvic brim. At the lower border of L5, the common iliac artery divides into internal and external iliac branches. The external iliac artery gives off only two branches, the inferior epigastric artery and the deep circumflex iliac artery, and then, after passing under the inguinal ligament, becomes the femoral artery, which is the primary blood supply to the lower limb.

The internal iliac artery supplies all of the organs within the pelvis and sends branches out through the greater sciatic foramen to supply the gluteal muscles. A branch also exists through the greater sciatic foramen and re-enters the lesser sciatic foramen to supply the perineum. After passing over the pelvic brim, the internal iliac arteries divide into anterior and posterior trunks. The posterior trunk consists of three branches: the ilolumbar artery, the lateral sacral artery, and the superior gluteal artery. These vessels are closely related to the nerve plexus on the piriformis muscle. The superior gluteal artery is the largest branch of the internal iliac artery and supplies the muscles and skin of the gluteal region. Accidental occlusion of this artery during uterine fibroid embolization can result in necrosis of the gluteal region.

The anterior trunk of the internal iliac artery has several branches that are routinely seen during laparoscopic surgery. The obliterated umbilical artery is a fibrous band seen on the anterior abdominal wall as the medial umbilical fold and can be traced back to its juncture with the internal iliac artery. At this point, the uterine artery can be identified as it arises from the medial surface of the internal iliac. The superior vesical artery also arises near this point and courses medially and inferiorly to supply the superior aspect of the bladder and the distal ureter.

The uterine artery is of particular importance to the reproductive surgeon. After the umbilical artery emerges from the anterior trunk of the internal iliac artery, the uterine artery runs parallel to and then crosses over the ureter at the level of the uterine cervix in the base of the broad ligament.

The vaginal artery most commonly originates from the uterine artery, but may arise independently from the internal iliac artery. The uterine, vaginal, and ovarian arteries anastomose with each other, with branches of the internal pudendal artery, and with the corresponding contralateral arteries.

The other important branches of the anterior trunk of the internal iliac artery are the obturator artery, which courses laterally and anteriorly toward the obturator canal, and the middle rectal, internal pudendal, and inferior gluteal arteries. The inferior gluteal artery is the largest branch of the anterior trunk.

Ureters

The ureters measure approximately 25 to 30 cm from kidney to bladder and are occasionally duplicated on one or both sides for all or part of this course. Their abdominal segment lies behind the parietal peritoneum on the medial part of the psoas major muscle and crosses the common iliac vessels at the level of their bifurcation at the pelvic brim.

The pelvic segment of the ureters runs down on the lateral wall of the pelvic cavity, along the anterior border of the greater sciatic notch immediately beneath the parietal peritoneum. Here the ureters form the posterior boundary of the ovarian fossae. They then run medial and forward between the two layers of the broad ligaments. It is here that the ureters run parallel to the uterine arteries for about 2.5 cm before crossing under the arteries and ascending on the lateral aspects of the uterine cervix and upper part of the vagina to reach the bladder.

The average distance between the ureters and cervix is greater than 2 cm.⁸ However, the reproductive surgeon should remember that this distance can be less than 0.5 cm in approximately 10% of women, which explains in part the relatively common occurrence of ureteral injury during hysterectomy (Fig. 7-8).

Figure 7-8 Schematic representation of the proximity of the ureter to the cervix. A, Sagittal view of pelvic organs. B, Transverse view of pelvic organs at the level of the cervix.

(From Hurd WW, Chee SS, Gallagher KL, et al: Location of the ureters in relation to the uterine cervix by computed tomography. Am J Obstet Gynecol 184:336–339, 2001.)

On reaching the base of the bladder, the ureters run obliquely through the wall for approximately 2 cm and open by slitlike orifices at the angles of the trigone. When the bladder is distended during cystoscopy, these orifices are approximately 5 cm apart. When the bladder is emptied, this distance decreases by 50%.

Pelvic Diaphragm

The pelvic diaphragm forms the muscular floor of the pelvis and is made up of the levator ani and coccygeus muscles that are all attached to the inner surface of the minor pelvis (Fig. 7-9).⁹ The levator ani is composed of three muscles. The innermost puborectalis muscle is attached to the pubic symphysis and encircles the rectum. The thicker, more medial pubococcygeus muscle runs from the pubic symphysis to the coccyx. This muscle is attached laterally to the obturator internus muscle by a thickened band of dense connective tissue called the arcus tendineus. The fusion of these bilateral muscles in the midline is called the levator plate and forms a shelf on which the pelvic organs rest. When the body is in a standing position, the levator plate is horizontal and supports the rectum and upper two thirds of the vagina above it. The thinner, more lateral iliococcygeus muscle runs from the arcus tendineus and ischial spine to the coccyx. The posterolateral margin of the pelvic diaphragm is the coccygeus muscle, which extends from the ischial spine to the coccyx and lower sacrum.

Figure 7-9 Laparoscopic view of the levator ani muscle. The rectum has been transected. The hysterectomy is complete and sutures are seen in the vagina. The ureters are seen laterally entering the pelvis. Most of the levator ani muscle seen here is iliococcygeus. The fibers are directed toward the sacrum and coccyx as well as toward the opposite muscle to form a midline raphe.

Weakness or damage to parts of the pelvic diaphragm may loosen the sling behind the anorectum and cause the levator plate to sag. Women with prolapse have been shown to have an enlarged urogenital hiatus on clinical examination.¹⁰

Perineal Membrane, Deep and Superficial Perineal Pouches

The deep perineal pouch bridges the gap between the inferior pubic rami and the perineal body. It closes the urogenital hiatus and has a sphincter-like effect at the distal vagina. It provides structural support for the distal urethra and also contributes to continence because it is attached to periurethral striated muscles. Knowledge of the anatomy of this area is necessary for surgical procedures that involve creation of a neovagina in patients with androgen insensitivity syndrome or correction of ambiguous genitalia.

The perineal membrane and the deep perineal pouch are musculofascial structures located over the anterior pelvic outlet below the pelvic diaphragm. The perineal membrane is a fascial layer attached to the ischiopubic rami. There are openings in this fascia for the urethra and vagina. The deep perineal pouch is located superior to this membrane and has several contiguous striated muscles: the compressor urethrae and sphincter urethrovaginalis muscles, the external urethral sphincter, and the deep transverse perineal muscles.

The superficial perineal pouch contains several muscles, the ischiocavernosus, bulbospongiosis, and superficial transverse perineal muscles as well as the greater vestibular glands (Bartholin’s glands).

The Rectum

The rectum of the adult is approximately 12 to 15 cm in length. It begins at the rectosigmoid junction in front of S3 and ends at the anorectal junction at the level of the tip of the coccyx. Unlike the colon, it lacks taeniae coli, haustra, and omental appendices.

The upper third of the rectum projects into the peritoneal cavity anteriorly and laterally. At its midpoint, the anterior peritoneum of the rectum extends onto the fornix of the vagina to form the rectouterine pouch. The distal one third is completely retroperitoneal.

The blood supply to the rectum includes the superior rectal artery, a branch from the inferior mesenteric artery; the middle rectal artery, a branch from the internal iliac artery; and the inferior rectal artery, a branch from the internal pudendal artery. The rectum is innervated by sympathetic fibers from the inferior hypogastric plexus, parasympathetic fibers that leave the sacral spinal cord (S2–S4) as pelvic splanchnic nerves and enter the inferior hypogastric plexus before passing to the rectum, and sensory fibers from the rectum that join the inferior hypogastric plexus.

Vagina

The vagina is a musculomembranous sheath 7 to 9 cm in length that extends anteroinferiorly from the uterine cervix to the vestibule. Because the cervix enters the vagina along the anterior wall, the posterior wall is about 1 cm longer than the anterior wall. Anterior and posterior to the cervix are vaginal fornices. Intraperitoneally, the vagina is separated from the rectum by the rectouterine pouch and from the bladder by the vesicouterine pouch (see Fig. 7-4).

The vagina receives its blood supply from the uterine, vaginal, and middle rectal arteries, which form an extensive anastomotic network. Innervation of the vagina is from the inferior hypogastric plexus and pelvic splanchnic nerves.

Uterus

The uterus is a fibromuscular organ that varies in size and weight according to life stage and parity. The uterus is divided into a body (corpus) and cervix. The part of the body of the uterus above the uterine tube is called the fundus. In a nulliparous woman the uterus is about 8 cm in length from the external os to the fundus, 5 cm in width at the fundus, and 2 to 3 cm deep anteroposteriorly. It weighs between 40 and 100 g.

The uterine cavity is triangular in shape, and the anterior and posterior walls approximate each other. Because the uterine cavity is a virtual space, ultrasound assessment of the uterus will only show a cavity when it is distended with fluid.

The length of the uterine cavity changes according to life stage, in part because of the profound effect of hormones on uterine size. In premenarchal girls the uterine length from the external os to the fundus is 1 to 3 cm. The cervix occupies two thirds of the uterine length in prepubertal girls and only one third after menarche. During the reproductive years, the expected length of the cavity is about 6 to 7 cm, which is important to remember when introducing instruments into the uterine cavity during endometrial biopsy, hysteroscopy, or embryo transfer. In postmenopausal women the uterus decreases to about 3 to 5 cm long.

The uterine wall is made up of three layers: endometrium, myometrium, and serosa. The endometrium is hormonally responsive and varies in thickness from 5 to 15 mm during a single menstrual cycle during the reproductive years. After menopause, it should be less than 5 mm in thickness as measured by ultrasound.

The myometrium consists of three to four indistinct layers of smooth muscle approximately 1 to 1.25 cm thick during the reproductive years. It is thickest in the midportion of the uterine corpus and thinnest near the opening of the uterine tube. The outermost layer consists of mostly longitudinal fibers. The middle layer consists of circular and oblique fibers and includes most of the blood vessels and loose connective tissue. The innermost layer is composed of mostly longitudinal fibers that are continuous with the uterine tubes and ligaments that surround the uterus.

The uterine blood supply is from the uterine artery, a branch of the internal iliac artery. The uterine artery courses along the lateral border of the uterus and forms extensive anastomoses with the ovarian and vaginal arteries. Approximately 6 to 10 blood vessels penetrate the uterus from the uterine artery and run circumferentially as the anterior and posterior arcuate arteries. Vessels from the sides anastomose in the midline, but no large blood vessels are found in the midline. Doppler studies have shown that the arcuate arteries are at the periphery of the uterus. The arcuate arteries supply the radial branches that penetrate deeply the myometrium to reach the endometrium. These radial arteries give rise to the spiral arteries of the endometrium.

Incisions on the uterus made during myomectomy should take into consideration the anatomy of the uterus. An incision made vertically in the midline is less likely to divide the large uterine vessels on the lateral border of the uterus. However, vertical uterine incisions may transect several arcuate arteries.

Uterine Tubes

The uterine tubes are contained within the uppermost margin of the broad ligament and measure about 10 to 12 cm (see Fig. 7-1). Each tube is divided into several distinct anatomic segments: intramural (or interstitial), isthmic, ampullary, and infundibulum. The internal diameter of the tube ranges from less than 1 mm at the intramural portion to up to 10 mm at the infundibulum.

The intramural portion of the tube is usually 1.5 cm long and may be tortuous. The tubal ostium where it opens into the uterine cavity can be seen at hysteroscopy at each angle of the fundus.

The isthmic portion is often the site of tubal ligation and therefore the site of tubal anastomosis. The lumen is approximately 0.5 mm. Although magnification is required for anastomosis, the subsequent pregnancy rates are highest for procedures done in this area.

The ampulla comprises two thirds of the length of the tube and has four to five longitudinal ridges. It is the site of fertilization and thus the most common site of ectopic pregnancy. Although the lumen is much larger here, the pregnancy rates after anastomosis are lower.

The infundibulum is the distal section of the tube. It is not attached by peritoneum and is open to the peritoneal cavity. Its delicate finger-like projections are called fimbriae.

The tubal wall consists of three layers: mucosa, muscularis, and serosa. The muscular layer has a somewhat indistinct external longitudinal layer and inner circular layer of smooth muscle. The intramural portion has no anatomic sphincter, but closure is sometimes seen during hysteroscopy. The blood supply to the tube runs in the mesosalpinx and consists of branches from the uterine and ovarian arteries.

Ovaries

The ovaries are ovoid structures suspended from the posterior aspect of the broad ligament by the mesovarium (see Fig. 7-1). This fold of peritoneum contains an extensive complex of blood vessels. The infundibulopelvic ligament (suspensory ligament of the ovary) enters the ovary along its superior pole and carries the ovarian vessels, lymphatics, and nerves. These vessels are in close proximity to the ureter at the pelvic brim (see Fig. 7-1). The ovarian ligament is located on the inferior pole of the ovary. The ovary is attached to the broad ligament by the mesovarium. It has a rich vascular supply. An arcade of vessels is formed from the anastomoses of the uterine and ovarian vessels. Theses vessels, called helicine because of their highly coiled structure, course through the mesovarium into the medulla. Veins then drain the medulla from a plexus seen in the mesovarium. Dissection around this area during a lysis of tubal adhesions or cystectomy should be performed with great care to avoid bleeding.

The ovarian volume is dependent on both the life stage and the germ cell population. During the reproductive years, ovaries without functional cysts weigh approximately 20 to 35 g and measure approximately 4 × 2 × 1 cm. Before menarche and after menopause, the ovaries will be smaller.

Peritoneal Folds

The broad ligament is a double-layered transverse fold of peritoneum that encloses the uterus and uterine tubes and extends to the lateral walls and pelvic floor (see Figs. 7-1 and 7-4). It is made up of the mesometrium lateral to the uterus that encloses the uterine vessels and the ureters, the mesovarium that attaches the ovary to the broad ligament posteriorly, and the mesosalpinx that connects the uterine tube near the base of the mesovarium.

The suspensory ligament of the ovary, often referred to as the infundibulopelvic ligament, is a lateral continuation of the broad ligament beyond the uterine tube that connects the ovary to the pelvic brim and contains the ovarian artery and vein. The ureter crosses beneath these vessels near the point where this ligament joins the pelvic sidewall.

Fascial Ligaments

The cardinal ligament is a connective tissue condensation lateral to the cervix that is bordered anteriorly and posteriorly by the leaves of the broad ligament and inferiorly by the pelvic floor. It is continuous with the paracervix, a dense fibrous sheath around the lower cervix and the upper vagina, and is attached to the pelvic walls laterally. It usually contains major branches of the uterine vessels.

The uterosacral ligament is a connective tissue band arising from the posterior paracervix that fans out to attach to the sacrum and rectum. It contains some smooth muscle fibers.

Gubernacular Ligaments

The ovarian ligament runs in the broad ligament and attaches the medial pole of the ovary to the posterior-lateral uterine surface beneath the uterine tube. The round ligament is the forward continuation of the uterine attachment of the ovarian ligament. This fibromuscular structure traverses the deep inguinal ring and terminates as fibrous strands in the connective tissue of the labium majus.