Anterior abdominal wall

• Abdominal Regions


  9 regions used to describe the location of abdominal organs, pains or pathologies

  
• Abdominal Regions


  • Delineated by 4 planes: 2 sagittal (vertical) and 2 transverse (horizontal)

  
• Abdominal Regions


  • Right hypochondrium
  • Epigastric
  • Left Hypochondrium
  • Right lumbar (lateral)
  • Umbilical
  • Left lumbar (lateral)
  • Right inguinal/iliac
  • Pubic (hypogastric)
  • Left inguinal/iliac

  
• Most often used Transverse Planes

  • Subcostal plane
  • Transtubercular plane
• Subcostal plane


  Passes through the inferior border of the 10th costal cartilage on each side
• Transtubercular plane


  Passes through the iliac tubercles
• Most often used Sagittal Planes

  • Midclavicular planes
• Midclavicular planes


  Pass from the midpoint of the clavicles to the mid-inguinal points
• Other Transverse Planes


  • Transpyloric plane
  • Interspinous plane
• Transpyloric plane


  Horizontal line through L1 vertebra

  
• Interspinous plane


  Passes through the anterior superior iliac spine
• Other Sagittal Planes


  • Semilunar lines
• Semilunar lines


  Lines at which layers of the rectus sheath fuse lateral to the rectus abdominis muscle and medial to the oblique muscles

  
• Abdominal Quadrants


  • Defined by 2 planes: Transumbilical plane (passes through the umbilicus) and Median plane

  
• Organs in Right Upper Quadrant

  • Liver- right lobe
  • Gallbladder
  • Stomach- pylorus
  • Duodenum- parts 1-3
  • Pancreas- head
  • Right suprarenal gland
  • Right Kidney
  • Right colic (hepatic) flexure
  • Ascending colon- superior part
  • Transverse colon- right half

  
• Organs in Left Upper Quadrant

  • Liver- left lobe
  • Spleen
  • Stomach
  • Jejunum and proximal ileum
  • Pancreas- body and tail
  • Left suprarenal gland
  • Left kidney
  • Left colic (splenic) flexure
  • Descending colon- superior part
  • Transverse colon- left half

  
• Organs in Right Lower Quadrant

  • Cecum
  • Appendix
  • Ileum (most of)
  • Ascending colon- inferior part
  • Right ovary
  • Right uterine tube
  • Right ureter- abdominal part
  • Right Spermatic cord- abdominal part
  • Uterus (if enlarged)
  • Urinary bladder (if full)

  
• Organs in Left Lower Quadrant

  • Sigmoid colon
  • Descending colon- Inferior part
  • Left ovary
  • Left uterine tube
  • Left ureter- abdominal part
  • Left spermatic cord- abdominal part
  • Uterus (if enlarged)
  • Urinary bladder (if full)
• Mid-inguinal points


  Midpoints of the lines joining the anterior superior iliac spine and the pubic tubercles on each side
• Borders of Anterolateral Abdominal Wall


  • Superior: Cartilages of 7th to 10th ribs, Xiphoid process of sternum

  Inferior: Inguinal ligament, Superior margins of the anterolateral aspects of the pelvic girdle (Iliac crests, pubic crests, pubic symphysis)

  
• Layers of Anterolateral Abdominal Wall

  • Skin

  2. Superficial fascia (2 layers below umbilicus): Camper fascia (superficial fatty layer), Scarpa fascia (deep membranous layer)

  3. Investing superficial fascia: External oblique muscle

  4. Investing intermediate fascia: Internal oblique muscle

  5. Investing deep fascia: Transversus Abdominis

  6. Endoabdominal (transversalis) fascia

  7. Extraperitoneal fat

  8. Peritoneum

  
• Muscles of Anterolateral Abdominal Wall


  • External oblique

  Internal oblique

  Transversus abdominis

  Rectus abdominis

  Pyramidalis

  
• External oblique


  • Origin: External surfaces of 5th–12th ribs

  Insertion: Linea alba, Pubic tubercle, Lateral lip of iliac crest

  Innervation: T7-T11 spinal nn., Subcostal n.

  Main Action: Compress abdominal contents, Flex trunk, Bend trunk to same side, Rotate trunk to opposite side

  
• Internal oblique


  • Origin: Thoracolumbar fascia, Anterior 2/3 of iliac crest, Connective tissue deep to lateral 1/3 of inguinal ligament, Inferior borders of 10th–12th ribs

  Insertion: Linea alba, Pecten pubis via conjoint tendon

  Innervation: Anterior rami of T6-T12 spinal nn., L1 spinal n.

  Main Action: Compress abdominal contents, Flex trunk, Bend trunk and turn anterior part of abdomen to same side

  
• Transversus abdominis


  • Origin: Internal surfaces of 7th–12th costal cartilages, Thoracolumbar fascia, Iliac crest, Connective tissue deep to lateral 1/3 of inguinal ligament

  Insertion: Linea alba, aponeurosis of internal oblique, Pubic crest, Pecten pubis via conjoint tendon

  Innervation: Anterior rami of T6-T12 spinal nn.

  Main Action: Compress abdominal contents

  
• Rectus abdominis


  • Origin: Pubic symphysis, Pubic crest, Xiphoid process, 5th–7th costal cartilages

  Innervation: Anterior rami of T6-T12 spinal nn.

  Main Action: Compress abdominal contents, Flex lumbar vertebrae, Control tilt of pelvis

  
• Pyramidalis


  • Origin: Front of pubis

  Insertion: Pubic symphysis, Linea alba

  Innervation: Anterior ramus of T12 spinal n.

  Main Action: Tenses the linea alba
• Combined actions of anterolateral abdominal wall muscles

  • Move the trunk & maintain posture

  Strong expandable support (stomach, uterus)

  Depress the ribs by approximating anterior costal margin and pubic crest (expiration)

  Compress abdomen (evacuation & heavy weight lifting)

  Support & protect viscera especially intestines

  
• External oblique aponeurosis


  • Begins medially at the midclavicular line and inferiorly at the spino-umbilical line

  Fibres decussate at the linea alba

  Most fibres become continuous with tendinous fibres of the contralateral internal oblique muscle

  Inguinal ligament (Poupart ligament) is the inferior margin

  Lacunar ligament is at medial end of inguinal ligament to superior pubic ramus

  Pectineal ligament (of Cooper) is the most lateral fibres of lacuna ligament on pecten pubis

  
• Internal oblique aponeurosis


  • Fibres also become aponeurotic at the midclavicular line
• Transversus abdominis


  • Aponeurosis forms conjoint tendon with internal oblique

  Neurovascular plane is superficial to this muscle

  
• Muscle contributions to covering of spermatic cord and rectus sheath

  • External oblique: External spermatic fascia, Aponeurosis- anterior layer

  Internal oblique: Cremaster muscle & fascia, Aponeurosis- both layers

  Transversus abdominis: No contribution, Aponeurosis- posterior layer

  
• Rectus abdominis


  • Enclosed in the rectus sheath

  Anchored transversely by attachment to the anterior layer of the rectus sheath at 3 tendinous intersections: At the level of the xiphoid process, Halfway between the xiphoid process and umbilicus, At the umbilicus

  
• To test action of rectus abdominis

  Raise head while lying flat on back without using arms
• Pyramidalis


  • Variable in size, Larger on one side (may be double), Not always present (80% only)
• Rectus Sheath


  • Strong, incomplete fibrous compartment of the rectus abdominis and pyramidalis muscles

  Contents: Rectus abdominis and pyramidalis muscles, Superior and inferior epigastric arteries and veins, Lymphatic vessels, Abdominal portions of the anterior rami of spinal nerves T7-T12 (thoraco-abdominal nerves)

  Formed by the decussation and interweaving of the aponeuroses of the flat abdominal muscles: Anterior layer- external oblique and anterior lamina of internal oblique, Posterior layer- transversus abdominis and posterior lamina of internal oblique

  
• Arcuate line


  • One third distance from the umbilicus to the pubic crest

  Demarcates transition in composition of posterior layer of rectus sheath

  Above arcuate line (superior ¾ of posterior layer): Made from aponeuroses of transversus abdominis and posterior lamina of internal oblique

  Below arcuate line (inferior ¼ of posterior layer): All 3 aponeuroses pass anterior to the rectus abdominis, Only the thin transversalis fascia covers the rectus abdominis posteriorly

  
• Rectus sheath superior to costal margin

  • Posterior layer is deficient: Transversus abdominis continues superiorly as transversus thoracis internal to costal cartilages, Internal oblique attaches to the costal margin

  Rectus abdominis lies directly on the thoracic wall

  
• Linea alba


  Interlacing fibres of the anterior and posterior layers of the rectus sheath in the anterior median line

  Separates the bilateral rectus sheaths

  Narrows inferior to the umbilicus to the width of the pubic symphysis

  Widens superiorly to the width of the xiphoid process

  Transmits small vessels and nerves to the skin

  
• Umbilical ring


  In the middle of the linea alba beneath the umbilicus

  All layers of the anterolateral abdominal wall fuse