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STUDY OF HUMAN ANATOMY ANATOMY OF THE ABDOMEN DEFINITION OF ABDOMEN • A region of the body bounded by the following regions:– – – – Superiorly – thorax Inferiorly – pelvis/perineum Posteroinferiorly – back Inferolaterally – lower limbs BONY LANDMARKS OF THE ABDOMEN • Xiphoid process • Costal margin – 7th – 11th costal cartilages • Pelvic bones • L1 – L5 Lumbar vertebrae ABDOMINAL CAVITY • extends btw thoracic diaphragm & pelvic diaphragm – abdominopelvic cavity • upper part is under cover of the osteocartilagenous thoracic cage • occupied by organs of the digestive, urogenital, endocrine & vascular structures. CONTENTS OF THE ABDOMINAL CAVITY CONTENTS OF THE ABDOMINAL CAVITY ABDOMINAL WALL PLANES OF THE ABDOMEN • 4 planes divide the abdominal cavity into 9 regions – 2 vertical (midclavicular), midclavicular to midinguinal – 2 transverse – ( subcostal & transtubercular) • Subcostal – pass through 10th costal cartilage • Transtubercular – pass through iliac tubercle REGIONS OF THE ABDOMEN REGIONS OF THE ABDOMEN QUADRANTS OF THE ABDOMEN • 2 planes delineate the abdominal cavity into 4 quadrants • 1 vertical – median • 1 transverse – transumbilical POSITIONS OF THE ABDOMINAL ORGANS ANTEROLATERAL ABDOMINAL WALL • Anterior & lateral walls extending from the thorax to pelvis • Consists of the – (1) Skin – (2) Fascia Subcutaneous & deep – (3) Muscles – (4) Transversalis fascia – (5) Extraperitoenal fat – (6) Peritoneum ANTEROLATERAL ABDOMINAL WALL • Anterior & lateral walls extending from the thorax to pelvis • Consists of the – (1) Skin – (2) Fascia Subcutaneous & deep – (3) Muscles – (4) Transversalis fascia – (5) Extraperitoenal fat – (6) Peritoneum SKIN • Loosely attaches to the superficial fascia, except at the umbilicus. • Varies in texture - wrinkle, rough, smooth, scars. • Thin in front and thick at the back • Distribution of hair varies with sex, age and race. • Natural tension lines run horizontally around the body wall. FASCIA • (L. panniculi – apron) • Composed of fatty tissues and fibrous connective tissue • Divided into two layers – (1) Superficial – (2) Deep – covers abdominal muscles • (1) Same as elsewhere and varies in amount of fat. • (1) Major site of fat storage. • (1) Excessive fat deposition in the lower anterior abdominal wall – morbid obesity SUPERFICILA FASCIA/TISSUE • Superior to umbilicus – Consistent with other regions • Inferior to umbilicus – Reinforced by collagen and elastic fibers – Thus 2 layers – • (1) Superficial fatty layer (Camper’s fascia) • Same elsewhere • (2) Deep membranous layer (Scarpa’s fascia) • Membranous continues to the perineum – Colles’s fascia, not to the thigh. SUPERFICIAL FASCIA SUPERFICIAL FASCIA MUSCLES OF THE ANTEROLATERAL ABDOMINAL WALL • 5 pairs of muscles bilaterally – 3 flat, 2 vertical • • • • • (1) External oblique (2) Internal oblique (3) Transversus abdominis (4) Rectus abdominis (5) Pyramidalis EXTERNAL OBLIQUE MUSCLE • • • • O: external surfaces of 5th – 12th ribs I: linea alba, pubic tubercle, ant ½ of iliac crest N: thoracoabdominal nerves (T7-T11 spinal nerves), subcostal nerve. A: compresses the abdomen to provide support for abdominal organs. INTERNAL OBLIQUE MUSCLE • • • • O: thoracolumbar fascia, ant 2/3 of iliac crest, lat 1/3 of inguinal ligament. I: inferior borders of 10th – 12th ribs, linea alba, pecten pubis, conjoint tendon. N: thoracoabdominal nerves (T6-T12 spinal nerves), L1 nerve A: compresses and supports abdominal viscera TRANSVERSUS ABDOMINIS MUSCLE • • • • O: thoracolumbar fascia, internal surfaces of 7th-12th costal cartilages, iliac crest, lat 1/3 of inguinal ligament. I: linea alba, pubic crest, pecten pubis, conjoint tendon. N: thoracoabdominal nerves (T6-T12 anterior rami of spinal nerves), L1 nerve A: compresses and supports abdominal viscera RECTUS ABDOMINIS MUSCLE • • • • O: pubic symphysis & pubic crest I: xiphoid process & 5th-7th costal cartilages N: thoracoabdominal nerves (T6-T12 spinal nerves) A: flexes trunk, compresses and supports abdominal organs, prevents pelvic tilting ABDOMINAL MUSCLES ABDOMINAL MUSCLES DEEP FASCIA • Dense connective tissue layer , devoid of fat, that covers the muscles and their aponeurosis. • 3 layers – superficial, intermediate & deep. DEEP FASCIA PYRAMIDALIS MUSCLE • Small, insignificant muscle. • Absent in 20% of people • • • • O: pubic crest, pubic symphysis I: linea alba N: subcostal nerve (T12) A: tenses the abdomen RECTUS SHEATH • A strong incomplete fibrous compartment • Formed by decussation and interweaving of the flat abdominal muscles. • Internal oblique aponeurosis splits into two layers: anterior & posterior and invest the rectus abdominis muscle. RECTUS SHEATH • Anterior wall – external oblique, anterior layer of internal oblique • Posterior wall – transversus abdominis and posterior layer of internal oblique. • All aponeuroses fuse in the midline – linea alba. • In the midline, it contains the umbilical ring. A defect where fetal umbilical vessels pass to the placenta. • Splitting of internal oblique, lateral to rectus abdominis – semilunar line. RECTUS SHEATH • Posterior wall ends slightly below the umbilicus – arcuate line of Douglas. • The rectus abdominis is covered by the transversalis fascia posteriorly. CONTENTS OF THE RECTUS SHEATH • Contents of the Rectus Sheath. – Rectus abdominis muscle – Pyramidalis – Superior & inferior epigastric vessels – Intercostal nerves (T7-T11) RECTUS SHEATH ENDOABDOMINAL FASCIA • A membranous and areolar sheets. • Named according to muscle or aponeurosis it lines. • Transversalis fascia as it lines the transversus abdominis muscle. • A variable amount of fat separates the fascia above from the peritoneum – extraperitoneal fat. • Peritoneum – a single layer of epithelial cells and connective tissue. NERVES OF THE ANTEROLATERAL ABDOMINAL WALL • (1) thoracoabdominal nerves (T7 – T11) • (2) Subcostal nerve (anterior ramus of T12) • (3) Iliohypogastric • (4) Ilioinguinal VESSELS OF THE ANTEROLATERAL ABDOMINAL WALL • (1) superior epigastric artery • (2) musculophrenic artery • (3) 10th & 11th post intercostal arteries • (4) subcostal artery • (5) inferior epigastric • (6) deep circumflex iliac • (7) superficial circumflex iliac • (8) superficial epigastric VEINS & LYMPHATICS OF THE ANTEROLATERAL ABDOMINAL WALL • (1) Subcutaneous venous plexus • (2) Paraumbilical veins • (3) Lateral thoracic vein • (4) Superficial epigastric veins • (5) superficial circumflex iliac • (6) superior & inferior epigastric • (7) deep circumflex iliac • (8) posterior interocstal (11th) & subcostal veins FUNCTIONS OF THE ABDOMINAL MUSCLES • Form a strong expandible support for the wall • Support organs from injuries • Compress to increase intraabdominal pressure to facilitate expulsion • Move trunk to maintain posture • Assists in breathing FINIS