Abdomen L2 - Anterolateral Abdominal Wall (Part 1) Lecture Notes PDF

Anatomy of Abdomen Lecture 2 Anterolateral abdominal wall (part 1) Sajjad Abdulaziz A 3rd-staged medical student at Al-Nahrain University  Objectives Layers of anterolateral abdominal...

Anatomy of Abdomen Lecture 2 Anterolateral abdominal wall (part 1) Sajjad Abdulaziz A 3rd-staged medical student at Al-Nahrain University  Objectives Layers of anterolateral abdominal wall. Skin & subcutaneous tissue of anterolateral abdominal wall. Protuberance of abdomen. Muscles of anterolateral abdominal wall & their functions. Rectus sheath & its contents. Linea alba & umbilical ring. Anterolateral abdominal wall 🔵 The anterolateral abdominal wall extends from the inferior margin of thoracic cage to the superior margin of the pelvic girdle. Layers of anterolateral abdominal wall 🔵 The anterolateral abdominal wall consists of (from superficial to deep) : - skin. - subcutaneous tissue (superficial fascia). - muscles and their aponeuroses. - transversalis fascia (part of endoabdominal fascia facsia). - extraperitoneal fat. - parietal peritoneum. * there is no deep fascia deep to the subcutaneous tissue in the anterolateral abdominal wall, except a thin investing fascia covers the outer surface of external oblique muscle. Skin of anterolateral abdominal wall 🔵 Skin of the anterolateral abdominal wall attaches loosely to the subcutaneous tissue, except at the umbilicus, where it adheres firmly. 🔴 Striae gravidarum : - is a specific form of scarring of the skin of the abdominal area. - occurs during pregnancy due to rapid expansion of the uterus as well as sudden weight gain during pregnancy. - occurs in about 90% of pregnant women. Subcutaneous tissue of anterolateral abdominal wall 🔵 It includes a variable amount of fat. 🔴 Males are especially susceptible to subcutaneous accumulation of fat in the lower anterior abdominal wall. 🔵 Inferior to the level of umbilicus, the subcutaneous tissue of the anterolateral abdominal wall has two layers : - a superficial fatty layer (called Camper’s fascia). - a deep membranous layer (called Scarpa’s fascia). 🔵 The membranous layer continues inferiorly into the perineal region as the superficial perineal fascia (Colles fascia), but doesn’t continue into the thighs, because it fuses with the deep fascia of the thigh (fascia lata) along a line approximately 2.5 cm below and parallel to the inguinal ligament. 🔴 So, urethral rupture may lead to spreed of urine into the anterolateral abdominal wall deep to the Scarpa’s facsia. Urine from a urethral rupture cannot spread into thighs. Protuberance of abdomen 🔵 A prominent abdomen is normal in infants and young children. 🔵 The six common causes of abdominal protrusion begin with the letter F: food, fluid, fat, feces, flatus and fetus, in addition to the tumors and organomegaly (organ enlargement). Muscles of anterolateral abdominal wall 🔵 There are five muscles on each side of the anterolateral abdominal wall (three flat muscles and two vertical muscles) : - external oblique. - internal oblique. - transversus abdominis. - rectus abdominis. - pyramidalis. 🔵 At the linea alba, the aponeurotic fibers of external oblique decussate and become continuous with the aponeurotic fibers of the contralateral internal oblique. Thus, the contralateral external and internal oblique muscles together form a digastric muscle (a two-bellied muscle sharing a common central tendon that works as a unit). For example, the right external oblique and left internal oblique work together when flexing and rotating to bring the right shoulder toward the left hip (torsional movement of trunk). 🔵 The lower parts of aponeurosis of internal oblique & transversus abdominis are fused forming the conjoint tendon (inguinal falx) that inserted into the pecten pubis. 🔵 The neurovascular plane of the anterolateral abdominal wall lies between the internal oblique and transversus abdominis muscles. Functions of anterolateral abdominal muscles 🔵 Functions of anterolateral abdominal muscles are : - support and considerable protection. - movements of trunk (flexion, extension, twisting and lateral rotation). - maintaining posture. - role in respiration. - increase intra-abdominal pressure. Rectus sheath 🔵 The rectus sheath is a strong, incomplete fibrous compartment. 🔵 Is formed by aponeurosis of the three flat muscles which join in the midline to form a strong fibrous raphe (called linea alba). 🔵 The rectus sheath has two walls (anterior & posterior walls) : - the external oblique aponeurosis contributes to the anterior wall of the sheath throughout its length. - the internal oblique aponeurosis splits into two layers (laminae) at the lateral border of the rectus abdominis : the anterior lamina : which passes anterior to the rectus abdominis and joins the external oblique aponeurosis to form the anterior wall of the rectus sheath. the posterior lamina : which passes posterior to the rectus abdominis and joins the transversus abdominis aponeurosis to form the posterior wall of the rectus sheath.  - beginning approximately one third of the distance from the umbilicus to the pubic crest : the aponeuroses of the three flat muscles pass anterior to the rectus abdominis to form the anterior layer of the rectus sheath. while the posterior wall is formed only by the transversalis fascia. 🔵 The arcuate line demarcates the transition between the aponeurotic posterior wall of the sheath covering superior 3/4 of the rectus abdominis and the transversalis fascia covering inferior 1/4 of it. 🔵 Above the costal margin : - the posterior wall is absent. - the anterior wall is formed only by external oblique aponeurosis. 🔵 In thin muscular people, two grooves are visible in the skin overlying the lateral borders of rectus sheath. These grooves extend from the 9th costal cartilages to the pubic tubercle & are called lineae semilunares. Contents of the rectus sheath 🔵 The rectus sheath contains : - rectus abdominis muscle. - pyramidalis muscle. - superior and inferior epigastric vessels. - lymphatic vessels. - distal portions of the thoraco-abdominal nerves. Linea alba (white line) 🔵 The linea alba : - is a fibrous structure. - runs in the anterior midline from the xiphoid process to the pubic symphysis. - is formed by the fusion of aponeuroses of the three flat anterolateral abdominal muscles. - separates the bilateral rectus sheaths. - narrows inferior to the umbilicus and widens superior to it. - transmits small vessels and nerves to the skin. - in thin muscular people, a groove is visible in the skin overlying the linea alba. Umbilical ring 🔵 Is a defect in the linea alba through which the fetal umbilical vessels passed to and from the umbilical cord and placenta. 🔵 The umbilical ring lies at the level of L3/L4 IV disk. 🔵 All layers of the anterolateral abdominal wall fuse at the umbilicus. 🔵 As fat accumulates in the subcutaneous tissue postnatally, the skin becomes raised around the umbilical ring and the umbilicus becomes depressed. Thank you