Thorax

• Abdomen


  The region of the trunk that lies between the diaphragm above and the inlet of the pelvis below

  
• Abdomen


  • It is a roughly cylindrical chamber
  • The superior aperture is the inferior thoracic aperture
  • The inferior limit is the superior margin of the lower limb
  • It contains a single large peritoneal cavity that freely communicates with the pelvic cavity

  
• Superior aperture of the abdomen

  The inferior thoracic aperture, the margin of which consists of vertebra TXII, rib XII, the distal end of rib XI, the costal margin, and the xiphoid process of the sternum

  
• Superior aperture of the abdomen

  • Vertebra LIII on the right crus and vertebra LII on the left crus
  • Medial and lateral arcuate ligaments cross muscles of the posterior abdominal wall and attach to vertebrae, the transverse processes of vertebra LI and rib XII, respectively
  • A median arcuate ligament crosses the aorta and is continuous with the crus on each side

  
• Pelvic inlet


  The circular margin formed posteriorly by the sacrum, anteriorly by the pubic symphysis, and laterally by a distinct bony rim on the pelvic bone

  
• Functions of the abdomen

  • Houses and protects major viscera
  • Breathing, it relaxes during inspiration and contracts during expiration, helps in coughing and sneezing
  • Changes in intra abdominal pressure

  
• Abdominal viscera


  • Major elements of the gastrointestinal system (caudal end of the esophagus, stomach, small and large intestines, liver, pancreas, and gallbladder)
  • The spleen
  • Components of the urinary system (kidneys and ureters)
  • The suprarenal glands
  • Major neurovascular structures

  
• Mesenteries


  Thin sheets of tissue that suspend the central gut tube (gastrointestinal system) from the posterior abdominal wall and partly from the anterior abdominal wall

  
• Divisions of the gut

  • Foregut (distal end of the esophagus, the stomach, and the proximal part of the duodenum)
  • Midgut (distal part of the duodenum and the jejunum, ileum, ascending colon, and proximal two-thirds of the transverse colon)
  • Hindgut (distal one-third of the transverse colon, descending colon, sigmoid colon, and superior part of the rectum)
• Abdominal wall


  • Consists partly of bone (five lumbar vertebrae and their intervening intervertebral discs, the superior expanded parts of the pelvic bones, and bony components of the inferior thoracic wall) and mainly of muscle

  
• Muscles of the posterior abdominal wall

  • Quadratus lumborum
  • Psoas major
  • Iliacus

  
• Muscles of the lateral abdominal wall

  • Transversus abdominis
  • Internal oblique
  • External oblique

  
• Rectus abdominis


  A segmented muscle that spans the distance between the inferior thoracic wall and the pelvis

  
• Transpyloric plane


  A horizontal plane that transects the body through the lower aspect of vertebra LI, about midway between the jugular notch and the pubic symphysis, crossing the costal margin on each side at roughly the ninth costal cartilage

  
• Transpyloric plane


  • Crosses through the opening of the stomach into the duodenum (the pyloric orifice)
  • Crosses through the body of the pancreas
  • Approximates the position of the hila of the kidneys

  
• Abdominal and pelvic organ location description

  Two methods: 9 regions pattern and 4 quadrant pattern

  
• 9 regions pattern


  1. 2 vertical lines (right & left midclavicular lines)

  2. 2 horizontal lines (subcostal line, transtubercular line)
• 4 quadrant pattern


  1. Horizontal transumbilical plane passing through the umbilicus and the intervertebral disc between vertebrae LIII and LIV

  2. Vertical median plane
• Surgical incisions


  Traditionally large incisions, now smaller incisions due to anesthesia and muscle-relaxing drugs
• Laparoscopic surgery


  • Small incisions no more than 1 to 2 cm in length
  • Camera (laparoscope) inserted through an umbilical port-site to transmit images to a monitor
  • Abdominal cavity inflated with gas to create space to operate
  • Additional port-sites for surgical instruments
• Layers of the anterior abdominal wall

  • Skin
  • Superficial fascia (above umbilicus one layer, below umbilicus two layers - Camper's fascia and Scarpa's fascia)
  • Deep fascia
  • Muscular layer (external oblique, internal oblique, transverse abdominal, rectus abdominis)
  • Transversalis fascia
  • Extraperitoneal fascia
  • Parietal peritoneum

  
• Superficial fascia


  A layer of fatty connective tissue, usually a single layer but in the lower region of the anterior abdominal wall it has two layers (Camper's fascia and Scarpa's fascia)

  
• Abdominal wall


  • Anterior abdominal wall
  • Posterior abdominal wall
• Layers of anterior abdominal wall

  • Skin
  • Superficial fascia
  • Deep fascia
  • Muscular layer
  • Transversalis fascia
  • Extraperitoneal fascia
  • Parietal peritoneum

  
• Superficial fascia


  Layer of fatty connective tissue, usually a single layer but forms two layers (Camper's fascia and Scarpa's fascia) below the umbilicus
• Camper's fascia


  Superficial fatty layer of superficial fascia
• Scarpa's fascia


  Deeper membranous layer of superficial fascia
• Anterolateral muscles


  • External oblique
  • Internal oblique
  • Transversus abdominis
  • Rectus abdominis
  • Pyramidalis

  
• External oblique muscle


  • Broad and thin muscular sheet, fibers pass downward forward medially, origin on lower 8 ribs, insertion on xiphoid process, linea alba, pubic crest, pubic tubercle, iliac crest

  
• Linea alba


  Aponeurotic component covering anterior abdominal wall to midline, formed by fusion of aponeuroses of abdominal wall muscles, wider above umbilicus and narrower below

  
• Aponeurosis of external oblique muscle

  • Fascia surrounding spermatic cord
  • Inguinal ligament
  • Lacunar ligament
  • Pectineal ligament
  • Boundaries of inguinal canal
  • Formation of rectus sheath

  
• Inguinal ligament


  Folded backward lower border of external oblique aponeurosis, between anterior superior iliac spine and pubic tubercle, lateral part gives origin to internal oblique and transversus abdominis, inferior border attaches to fascia lata

  
• Superficial inguinal ring


  Triangular defect in external oblique aponeurosis, above and medial to pubic tubercle, opening for spermatic cord or ligament of uterus

  
• Lacunar ligament


  Extension of external oblique aponeurosis backward and upward to pectineal line on superior ramus of pubis

  
• Pectineal ligament


  Fibers extending from lacunar ligament along pectineal line of pelvic brim

  
• Internal oblique muscle


  • Broad thin muscular sheet deep to external oblique, smaller and thinner, fibers pass superomedially, origin on lumbar fascia, anterior 2/3 iliac crest, lateral 2/3 inguinal ligament, insertion on lower 3 ribs, costal cartilage, xiphoid process, linea alba, symphysis pubis

  
• Transversus abdominis muscle


  • Fibers run horizontally forward under internal oblique, origin on inner surface of lower 6 costal cartilages, lumbar fascia, anterior 2/3 iliac crest, lateral 1/3 inguinal ligament, insertion on xiphoid process, linea alba, symphysis pubis

  
• Rectus abdominis muscle


  • Long flat muscle extending length of anterior abdominal wall, paired muscle separated by linea alba, widens and thins as it ascends from pubic symphysis to costal margin, intersected by transverse fibrous bands or tendinous intersections

  
• Pyramidalis muscle


  • Small triangular muscle anterior to rectus abdominis, base on pubis, apex attached superiorly and medially to linea alba

  
• Rectus sheath


  Aponeurotic tendinous sheath completely enclosing rectus abdominis and pyramidalis muscles, anterior wall formed by external oblique and half internal oblique aponeuroses, posterior wall formed by other half internal oblique and transversus abdominis aponeuroses