What does the abdominopelvic cavity extends between?
the abdominopelvic cavity extends between the thoracic diaphragm and pelvic diaphragm (observe the abdominal cavity is its major part).
What occupies most of the abdominal cavity?
How high can the abdominal cavity ascend?
What are the abdominal organs protected by?
the digestive organs occupy most of the abdominal cavity.
the abdominal cavity can ascend superiorly to the 4th ICS
the more superiorly positioned abdominal organs (liver, stomach, and spleen) are protected by the thoracic cage.
What divides the abdominal cavity into four quadrants?
Name the quadrants but ignore the organs listed for each quadrant.
the transumbilical and median planes divide the abdominal cavity into four quadrants
What do the midclavicular lines and subcostal and transtubercular planes demarcate?
the midclavicular lines and subcostal and transtubercular planes demarcate the epigastric, umbilical, and hypogastric (pubic) regions that are used to localize visceral pain referred from the abdominal cavity onto the abdominal wall.
What is the anterolateral abdominal wall formed mainly by?
What are the abdominal wall muscles derived from?
the anterolateral abdominal wall is formed mainly by a musculotendinous sheet
the abdominal wall muscles are derived from myoblasts in the parietal mesoderm.
What do the musculotendinous sheet consists of?
Name the muscles of the three-layered sheet.
the musculotendinous sheet consists of three layers with muscle fibers of each layer running in different directions.
Layer 1 - external oblique
Layer 2 - internal oblique
Layer 3 - transversus abdominis
What do the external oblique and contralateral internal oblique form?
What does synergistic action of these muscles cause?
a two-bellied muscle sharing a common central aponeurosis.
synergistic action of the muscle bellies causes flexion and rotation for torsional movement of the trunk.
What is the transverse, circumferential orientation of the transverse abdominis muscle ideal for?
ideal for compressing abdominal contents and increasing intra-abdominal pressure.
What does aponeuroses of the three muscle layers form?
What is the rectus abdominis?
aponeuroses of the three muscle layers form the rectus sheath that encloses the paired rectus abdominis muscles and separates them by the vertical linea alba.
the rectus abdominis is a powerful flexor of the vertebral column, especially the lumbar region.
What is the linea alba used for?
the linea alba is used surgically for rapid midline incisions that are relatively bloodless and avoid major nerves
1) What is the superior epigastric artery a terminal branch of?
2) What does the inferior epigastric artery arise from?
3) What does the superior and inferior epigastric arteries anastomose within?
1) the internal thoracic artery
2) the external iliac artery.
3) the rectus sheath.
1) What does the abdominal aorta bifurcates (at L4) to form? What do these arteries then form?
2) What does the external iliac artery become?
3) What artery supplies the pelvis?
3) the abdominal aorta bifurcates (at L4) to form the right and left common iliac arteries and their division forms the bilateral external and internal iliac arteries.
2) the femoral artery
3) the internal iliac artery supplies the pelvis
What causes prune belly syndrome and why does the abdomen become distended?
PRUNE BELLY SYNDROME – partial or complete absence of abdominal muscles, thinning of abdominal wall
Sometimes associated with:
o Malformations of the urinary tract and bladder, including urethral obstruction
o Accumulation of fluid
o Abdominal distension
o Atrophy of abdominal muscles
Why does lack of anterolateral wall muscle tone contribute to visceroptosis and lordosis?
PROTUBERANCE OF ABDOMEN
• Lack of AL wall muscle tone --> cannot hold abdominal organs against gravity --> sinking of abdominal viscera below their natural position (visceroptosis)
• Lack of AL wall muscle tone --> cannot resist weight of protuberant abdomen on anterior pelvis --> pelvis tilts anteriorly at the hip joints when standing --> lordosis
Why do palpation-induced spasms of anterolateral wall muscles provide a clinical sign of acute abdomen?
INTENSE PALPATION-INDUCED SPASMS OF ANTEROLATERAL WALL MUSCLES
• Occur when an organ is inflamed --> clinically significant sign of acute abdomen
• The spasms (guarding) attempt to protect the viscera from pressure, which is painful when an abdominal infection is present
• the thoracic nerve supply of the skin + muscles of the wall explains why these spasms occur
Why can transverse incisions of the rectus abdominis be made without permanent damage to the muscle?
TRANSVERSE INCISIONS OF THE RECTUS ABDOMINUS
• Rectus Abdominus muscle fibers run short distances between tendinous intersections (which run transversely)
• Cutting the muscle creates a new tendinous intersection
• Segmental nerves supplying it enter the lateral part of the rectus sheath where they can be located and preserved