TBL15 - Abdominopelvic Cavity Flashcards
What does the abdominopelvic cavity consist of? What two structures does it extend between?
1) The abdominopelvic cavity consists of the large abdominal cavity and small pelvic cavity
2) It extends between the thoracic and pelvic diaphragms
What occupies the abdominal cavity? Where can the abdominal cavity ascend to? What are the superiorly positioned abdominal organs protected by?
1) The digestive organs occupy the abdominal cavity
2) The cavity can ascend superiorly to the 4th ICS
3) Thus, the more superiorly positioned abdominal organs (liver, stomach, and spleen) are partially protected by the thoracic cage
What planes divide the abdominal cavity into four quadrants? Name the quadrants but ignore the organs listed for each quadrant.
1) For descriptive purposes, transumbilical (horizontal) and median (vertical) planes divide the abdominal cavity into four quadrants
2) Right upper quadrant, left upper quadrant, right lower quadrant, & left lower quadrant
What do the midclavicular lines and subcostal and transtubercular planes demarcate? What do these regions do?
1) The midclavicular lines and subcostal and transtubercular planes demarcate the epigastric, umbilical, and hypogastric (pubic) regions
2) These regions localize visceral pain referred from the abdominal organs onto the anterior abdominal wall (to be studied later)
What mainly forms the anterolateral abdominal wall? What is this sheet derived from?
1) The anterolateral abdominal wall is formed mainly by a musculotendinous sheet consisting of three laterally positioned muscle layers with their fused aponeuroses forming the anterior aspect of the sheet
2) The sheet is derived from mesenchymal cell-derived myoblasts and fibroblasts of the parietal mesoderm
What causes prune belly syndrome and why does the abdomen become distended?
1) Partial or complete absence of abdominal musculature is called prune belly syndrome
2) Usually, the abdominal wall is so thin that organs are visible and easily palpated
3) Urinary tract defects cause an accumulation of fluid that distends the abdomen, resulting in atrophy of the abdominal muscles
What does the external oblique form? Where do its fibers run? What does the internal oblique form? Where do its fibers run?
1) The external oblique forms the superficial muscle layer
2) Its fibers run inferomedially from the lateral surfaces of the 5th-12th ribs to the iliac crest
3) The internal oblique forms the intermediate muscle layer
4) Its fibers run superomedially from the iliac crest to the inferior borders of the 10th-12th ribs
What do the external and internal obliques form? What does synergistic action of these muscles allow for?
1) The external oblique and contralateral internal oblique form a two-bellied muscle sharing a common central aponeurosis
2) Synergistic actions of the muscle bellies cause flexion and rotation for torsional movement of the trunk
What forms the innermost muscle layer of the obliques? What is its function?
1) The transverse abdominis forms the innermost muscle layer
2) The transverse, circumferential orientation of its fibers (from internal surfaces of the 7th-12th ribs to the linea alba) is ideal for compressing abdominal contents and increasing intraabdominal pressure
What forms the rectus sheath and what does it enclose? How is the linea alba formed and what does it separate?
1) The fused aponeuroses of the three muscle layers form the rectus sheath that encloses the paired rectus abdominis muscles
2) Midline fusion of the bilateral rectus sheaths forms the vertical linea alba that separates the rectus abdominis muscles
What is the linea alba used for and why?
The linea alba is used surgically for rapid midline incisions that are relatively bloodless and avoid major nerves
Where do the rectus abdominis muscles extend from? What is their function?
1) The rectus abdominis muscles extend vertically from the pubic symphysis to the 5th-7th costal cartilages
2) Thus, the muscles powerfully flex the vertebral column, especially the lumbar region
Why does lack of anterolateral wall muscle tone contribute to visceroptosis and excessive lordosis?
1) When the anterior abdominal muscles are underdeveloped or become atrophic, as a result of old age or insufficient exercise, they provide insufficient tonus to resist the increased weight of a protuberant abdomen on the anterior pelvis
2) Visceroptosis (or enteroptosis) is a prolapse or a sinking of the abdominal viscera (internal organs) below their natural position. Any or all of the organs may be displaced downward
3) The pelvis tilts anteriorly at the hip joints when standing (the pubis descends and the sacrum ascends) producing excessive lordosis (sway back) of the lumbar region
Why do palpation-induced spasms of anterolateral wall muscles provide a clinical sign of acute abdomen?
1) Warm hands are important when palpating the abdominal wall because cold hands make the anterolateral abdominal muscles tense, producing involuntary spasms of the muscles, known as guarding
2) Intense guarding, board-like reflexive muscular rigidity that cannot be willfully suppressed, occurs during palpation when an organ (such as the appendix) is inflamed and in itself constitutes a clinically significant sign of acute abdomen
3) The involuntary muscular spasms attempt to protect the viscera from pressure, which is painful when an abdominal infection is present. The common nerve supply of the skin and 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?
1) Transverse incisions through the anterior layer of the rectus sheath and rectus abdominis provide good access and cause the least possible damage to the nerve supply of the rectus abdominis
2) This muscle may be divided transversely without serious damage because a new transverse band forms when the muscle segments are rejoined
3) Transverse incisions are not made through the tendinous intersections because cutaneous nerves and branches of the superior epigastric vessels pierce these fibrous regions of the muscle
