Applied anatomy of anterior abdominal wall.pptx

This ppt decribes the anatomy of anterior abdominal wall which can be helpful for mbbs students and pg students as it desrcibes the basic anatomy as well as the applied aspect to each layer of anterior abdominal wall.

1. Applied anatomy of anterior abdominal wall Dr. Shivani Siddhpura M.S.ObsGyn

2. The abdominal wall The superior border of the abdominal wall is the lower edge of the rib cage (ribs 7 through 12). The inferior margin is formed by the iliac crests, inguinal ligaments, and pubic bones.

3. Abdominal wall Layers Skin Subcutaneous Tissue: Fatty Camper’s fascia Fibrous Scarpa’s fascia Rectus Sheath (musculoaponeurotic layer) Transversalis Fascia Preperitoneal Fat Peritoneum

4. Skin The fibers in the dermal layer of the abdominal skin are oriented in a predominantly transverse direction following a gently curving upward line (Langer’s line). As a result, vertical skin incisions sustain greater lateral tension and thus, in general, develop wider scars. In contrast, low transverse incisions, such as the Pfannenstiel, follow Langer lines and lead to superior cosmetic results.

5. Subcutaneous tissue The subcutaneous layer can be separated into a superficial, predominantly fatty layer—Camper fascia, and a deeper membranous layer—Scarpa fascia. Camper fascia continues onto the perineum to provide fatty substance to the mons pubis and labia majora and then to blend with the fat of the ischioanal fossa. Scarpa f ascia continues inferiorly onto the perineum as Colle’s fascia.

6. Applied anatomy of subcutaneous fascia Spread of infection and abscess formation in the vulvar area is facilitated by the loose areolar tissue in the subcutaneous layers and the contiguity of the vulvar fascial planes with the groin and anterior abdominal wall. This is because Scarpa’s fascia continues into the perineum and becomes Colle’s fascia, but it fuses to the deep fascia of the thigh, thus forming a barrier to the spread of fluids and infection into the thigh (of course necrotizing fasciitis could eventually penetrate this fascia boundary but in this patient it may have impeded the spread of the infection into the thigh). 

7. Musculoaponeurotic layer Deep to the subcutaneous tissue is a layer of muscle and fibrous tissue (“fascia”) that holds the abdominal viscera in place and controls movement of the lower torso. The muscles of this layer can be considered in two groups: the vertical muscles in the midline (rectus abdominis and pyramidalis) and the more lateral flank muscles (the external oblique, internal oblique, and transversus abdominis). The fascia, properly called the rectus sheath, is created by the broad, sheet like tendons of these muscles, which form aponeuroses that unite with their corresponding member of the other side.

8. Rectus Sheath The muscle fibers of the external oblique become aponeurotic approximately at the midclavicular line. In the lower abdomen, this demarcation gradually develops more laterally. At its inferior margin, the muscle fibers of the internal oblique extend farther toward the midline than do the muscle fibers of the external oblique. Because of this, fibers of the internal oblique muscle are found underneath the aponeurotic portion of the external oblique muscle during a low transverse incision .

9. In addition, between the internal oblique and transversus abdominis muscles lies a neurovascular plane. This plane contains the nerves and arteries that supply the anterolateral abdominal wall. Although not often possible, the nerves should be identified and spared, and strategies used to avoid injury within the neurovascular plane should be used. For example, low transverse fascial incisions often used for gynecologic surgery should not extend beyond lateral margins of rectus muscles to avoid nerve and inferior epigastric vessel injury. In addition, suture that extend lateral to the edges of incision should be avoided as they may entrap the iliohypogastric and/or ilioinguinal nerve, which may lead to denervation injury or pain.

10. Arcuate line Its location is 2/3rd the distance from the pubic symphysis & 1/3 rd from the umbilicus. It is the demarcation where the internal oblique and transversus abdominis aponeuroses of the rectus sheath start to pass anteriorly to the rectus abdominis muscle, leaving only the transversalis fascia posteriorly.  It is also where the inferior epigastric vessels perforate the rectus abdominis.

11. Cross sections of lower abdominal wall above and below the arcuate line. 1 . external oblique 2 . internal oblique 3 . transversus abdominis muscle. A: Above the arcuate line ( linea semicircularis ): the anterior fascial sheath of the rectus muscle (in gray ) is derived from the external oblique and split aponeurosis of internal oblique muscles. The posterior sheath is formed by aponeurosis of the transversus abdominis muscle and split aponeurosis of the internal oblique muscle. B: Lower portion of the abdominal wall, below the arcuate line: The rectus muscle does not have a posterior fascial sheath, while all of the fascial aponeuroses form the anterior rectus muscle sheath. The rectus muscle is in direct contact with the transversalis fascia

12. Upto 7 th costal cartilage Below costal cartilage to arcuate line Arcuate line to pubic symphysis

13. Sagittal section showing extension of rectus sheath

14. Content of rectus sheath Muscles: Rectus Abdominis & pyramidalis Arteries: Superior epigastric artery branch of internal thoracic artery Inferior epigastric artery branch of external iliac artery . Veins corresponding to the arteries. Nerves: Terminal part of lower 6 thoracic nerves Lower 5 intercostal nerves (T7-T11) Subcostal Nerve

15. Applied Anatomy of rectus Sheath Divarication of the recti  ( separation of the recti abdominis muscles) : The separation of two rectus muscles usually occur in elderly multiparous woman with weak abdominal muscles. In this condition, the aponeuroses forming the rectus sheaths become excessively stretched, consequently when the patient coughs or strains, the recti separate widely and a hernial sac containing loops of intestine protrudes forward between the medial margins of the recti. Hematoma of rectus sheath:  Sometimes the superior and inferior epigastric arteries are unduly stretched during a severe bout of coughing or in later months of pregnancy and ruptures if they are exposed to blunt trauma to the anterior abdominal wall leading to the formation of hematoma within the rectus sheath. Clinically, it presents as: Midline abdominal pain. Tender mass confined to one rectus sheath

16. Transversalis Fascia Deep to the muscular layers and superficial to the peritoneum lies the transversalis fascia, a layer of fibrous tissue that lines the abdominopelvic cavity. It is visible during abdominal incisions as the layer just underneath the rectus abdominis muscles suprapubically .

17. peritoneum The peritoneum is a single layer of epithelial cells and supporting connective tissue called the serosa that lines the abdominal cavity and covers the abdominopelvic organs. The infraumbilical part of the anterolateral abdominal wall is characterized by five peritoneal folds that converge toward the umbilicus. The single median umbilical fold extends from the apex of the bladder to the umbilicus and covers the median umbilical ligament, a fibrous remnant of the urachus. Lateral to this are paired medial umbilical folds, which cover the medial umbilical ligaments, formed by the occluded part of the umbilical arteries. The lateral umbilical folds cover the inferior epigastric arteries and veins and, if transected, can lead to significant bleeding.

18. Umbilical ARea The umbilicus is an important surgical landmark and the most common point of entry during endoscopic surgery. All layers of the anterolateral abdominal wall fuse at the umbilicus. The umbilicus usually lies at a vertical level corresponding to the junction between the third and fourth lumbar vertebrae. This is also the level at which the iliac veins join to form the vena cava and at which the abdominal aorta bifurcates. The skin around the umbilicus is innervated by the 10 th thoracic spinal nerve (T10 dermatome). The umbilicus contains the umbilical ring, a defect in the linea alba through which the fetal umbilical vessels passed to and from the umbilical cord and placenta. The umbilical ring provides a window through which umbilical hernias may develop.

19. Vessels of the anterior abdominal wall Knowledge of the course of the abdominal wall blood vessels helps the surgeon anticipate their location during abdominal incisions or insertion of laparoscopic trocars. The blood vessels that supply the abdominal wall can be separated into those that supply the skin and subcutaneous tissues and those that supply the musculofascial layer.

20. A, B , and C designate safe spots for laparoscopic trocar insertion. Dotted lines indicate lateral border of the rectus muscle. The location of abdominal wall blood vessels in relationship to abdominal landmarks apparent at laparoscopy.

21. Three groups of vessels provide blood supply to the skin and subcutaneous tissues. The superficial epigastric vessels run a diagonal course in the subcutaneous tissue from the femoral vessels toward the umbilicus, beginning as a single artery that branches extensively as it nears the umbilicus. The external pudendal artery runs a diagonal course medially from the femoral artery to supply the region of the mons pubis. The superficial circumflex iliac vessels course laterally from the femoral vessels toward the flank.

22. The blood supply to the lower abdominal wall’s deeper musculofascial layer parallels the subcutaneous vessels. The inferior epigastric and the deep circumflex iliac arteries branch from the external iliac. The deep circumflex iliac artery lies between the internal oblique and transversus abdominis muscle. The inferior epigastric artery and its two veins originate lateral to the rectus muscle. The angle between the inferior epigastric vessels and the lateral border of the rectus muscle forms the apex of the inguinal triangle ( Hesselbach triangle), the base of which is the inguinal ligament. This triangle represents the area through which direct inguinal hernias protrude medial to the inferior epigastric vessels. Around the umbilical area, the inferior epigastric artery anastomoses with the superior epigastric, a branch of the internal thoracic artery.

23. Applied anatomy of vessels of abdominal wall Lateral laparoscopic trocars are placed in a region of the lower abdomen where injury to the inferior epigastric and superficial epigastric vessels can easily occur. The inferior epigastric arteries and the superficial epigastric arteries run similar courses toward the umbilicus. Knowing the typical location of these blood vessels helps in choosing insertion sites that will minimize their injury, reducing the potential for hemorrhage and hematomas. Just above the pubic symphysis, the vessels lie approximately 5.5 cm from the midline, whereas at the level of the umbilicus, they are 4.5 cm from the midline. Therefore, placement either lateral or medial to the line connecting these points minimizes potential vascular injury.

24. Nerve supply of anterior abdominal wall The innervation of the abdominal wall arises from the abdominal extension of intercostal nerves 7 through 11, subcostal nerve (T12), and iliohypogastric and ilioinguinal nerves (both L1). The cutaneous sensory innervation of the abdominal wall is derived from the intercostal nerves and the iliohypogastric and ilioinguinal nerves. The iliohypogastric and ilioinguinal nerves pass medial to the anterosuperior iliac spine in the abdominal wall. The former supplies the skin of the suprapubic area. The latter supplies the lower abdominal wall, and by sending a branch through the inguinal canal, it supplies the upper portions of the labia majora (anterior labial nerves) and medial portions of the thigh.

25. Nerve and vessel locations on anterior abdominal wall relative to surgically important landmarks

26. Applied anatomy of nerves of anterior abdominal wall The ilioinguinal and iliohypogastric nerves can be entrapped or cut during closure of a transverse incision or insertion of accessory trocars in the lower abdomen. This may lead to chronic pain syndromes that may manifest months to years after surgery. The risk of iliohypogastric and ilioinguinal nerve injury can be minimized if lateral trocars are placed superior to the anterosuperior iliac spines and if low transverse fascial incisions are not extended beyond the lateral borders of the rectus muscles. Elevation of the rectus sheath off the muscle during the Pfannenstiel incision stretches the perforating nerve, which is sometimes ligated or cauterized to provide hemostasis from the accompanying artery. This may leave an area of cutaneous anesthesia.