Basic Abdominal Anatomy

BASIC ABDOMINAL ANATOMY Boundaries of the Abdominal • • • Superiorly - Xiphoid process - costal margins - thoracic wall Posteriorly - Vertebral column Inferiorly - Pelvic bones - Inguinal ligament - Pelvic cavity Bony landmarks and other important landmarks Layers of the abdominal wall Skin Superficial fascia Two layers - External layer: fatty layer – Camper’s Internal layer: membranous layer-Scarpa’s Layers 3-5 Lateral layers (all are muscular) • External oblique • Internal oblique • Transverse abdominis Medial layers • Rectus sheath anterior and pyramidalis • Rectus abdominis • Rectus sheath posterior Rectus sheath • • • • • Formed by the aponeuroses of the lateral muscular layers Pyramidalis muscle can be absent or unilateral Laterally, the sheath is fused at the linea semilunaris Medially, the sheath is fused at the linea alba Arcuate line – inferior demarcation of the posterior sheath Composition of the posterior rectus heath • combination of the aponeuroses of the internal abdominal oblique and the transversus abdominis muscles Rectus sheath above and below arcuate line Rectus sheath: formed by aponeurosis of flat muscles Arcuate Line This anatomical finding may not always be present, and its position may vary. However, when present, the arcuate line is of great clinical significance, especially for surgeons, as Spigelian hernias usually present close to the arcuate line. Additionally, the arcuate line indicates where the inferior epigastric vessels perforate the rectus sheath. Layer 6: Transversalis fascia Layer 7: Extraperitoneal fascia Layer 8: Parietal peritoneum Fascia of the abdomen • • • • • • Subcutaneous tissue over most of the anterolateral wall Superficial, intermediate, and deep layers of investing fascia cover the external aspects of the three muscle layers of the anterolateral abdominal wall and their aponeuroses (flat expanded tendons) and cannot be easily separated from them Major site for fat storage Males are especially susceptible to subcutaneous accumulation of fat in the lower anterior abdominal wall Superior the umbilicus the subcutaneous tissue is consistent with that found in the regions Inferior to the umbilicus the deepest part of the subcutaneous tissue is reinforced by many elastic and collagen fibres, so it has two layers: - Superficial fatty layer: camper’s fascia - Deep membranous layer: scapa fascia ✓ Continuous inferiorly into the perineal fascia but not the thighs Superficial fascia • Also, knowns as subcutaneous tissue - A loose areolar connective or adipose tissue that connect the skin to the underlying bones or deep fascia Males: continues over the penis - Scrotum – dartos fascia Females - Continuous and is a component of labia majora Deeper layer • Fuses with superficial layer below inguinal ligament • A layer of dense connective tissue that surround individual muscles and groups of muscles to separate into fascial compartment Other abdominal fascia Investing fascia - Extremely thin - Represented mostly by the epimysium superficial to or between muscles - Cover 3 muscle layers of the anterolateral wall Endoabdominal fascia Also knows as intra-abdominal fascia - The internal aspect of the abdominal wall is lined with membranous and areolar sheets of varying thickness constituting Endoabdominal fascia Although continuous, different parts of this fascia are named according to the muscle or aponeurosis it is lining The portion lining the deep surface of the transversus abdominis muscle and its aponeurosis is the transversalis fascia For example, transverse fascia