Lab 7 Pre-Lab Exercise:
1. Surface anatomy of the abdomen
Visualization of the position of abdominal viscera is fundamental to a physical examination. Some of these viscera or their parts can be felt by palpating through the abdominal wall. Surface features can be used to establish the positions of deep structures.
Structures at the L1 level
At the transpyloric plane (L1 level) are: 1) the beginning and the upper limit of the end of the duodenum, 2) the hila of the kidneys, 3) the neck of the pancreas, 4) the origin of the superior mesenteric artery from the aorta.
2. Major blood vessels
Each of the vertebral levels n the abdomen is related to the origin of major blood vessels:
1) the celiac trunk originates from the aorta at the upper border of L1,
2) the superior mesenteric originates at the lower border of L1,
3) the renal arteries originate around L2,
4) the inferior mesenteric artery originates at L3
5) the aorta bifurcates into the right and left common iliac arteries at L5
6) the lest and right common iliac veins join to form the inferior vena cava at L5
3. Major abdominal viscera
Most of the liver is under the right dome of the diaphragm and is deep to the lower thoracic wall. The inferior margin of the liver can be palpated descending below the right costal margin when a patient is asked to inhale deeply. On deep inspiration, the edge of the live can be felt slipping under the palpating fingers place under the costal margin.
The stomach is located in the upper left quadrant. The cardiac orifice lies behind the left 7th costal cartilage, 2.5 cm from the midline. The pyloric orifice lies 2.5 cm to the right of the midline of the transpyloric plane.
The fundus can be represented as a semicircle of 7.5 cm diameter starting on the left of the cardiac orifice, the acute angle between the two producing the cardiac notch. The highest point of the fundus reaches the level of the left 5th intercostal space. The greater curvature is continued from the fundus curving gently downwards to the left as far as the 10th left costal cartilage before turning medially to reach the pylorus. The lesser curvature continues from the right side of the cardiac orifice to reach the pyloric orifice. The lowest part of its curving path is marked by a notch, the angular incisures, which lies just to the left of the midline.
The duodenum is 25 cm long can be divided into 4 parts.
The first part is 5 cm long and runs backwards, upwards, and to the right. It has a shorter surface projection which can be represented on the body wall by connecting the pylorus to a point about 2.5 cm away just above the medial to the 9th costal cartilage, and next to the right side of the L1 body.
The second part is 7.5 cm long and curves downwards to reach the subcostal plane at the level of L3 (5 cm from the midline).
The third part is 10 cm long and crosses the midline, lying just above the umbilicus, inclining slightly upwards to end just to the left of the midline at the L2-L3 disk level.
The fourth part is 2.5 cm long and ascends to the duodenojejunal flexure, situated about 2.5 cm to the left of the midline at the level of the L2 upper body.
Caecum and appendix
The caecum and appendix are in the right lower quandrant. The ileocaecal valve lies at the point of intersection of the right lateral line and the transtubercular plane, near the front of the right sacroiliac joint.
The caecum lies in the right iliac fossa, usually coming to within 2.5 cm of the inguinal ligament. If distended by feces or gas, it may be palpated through the anterior abdominal wall. It is approximately 7.5 cm in both length and breadth.
The appendix opens by its base into the caecum, 1.5 cm below the ileocaecal valve. This is marked by McBurney’s point,which is 1/3 of the distance along the line connecting the ASIS to the umbilicus.
The biliary system
The liver and gallbladder are located in the right upper quandrant. The fundus of the gall bladder projects below the lower border of the liver to contact the abdominal wall where the right lateral border of the rectus abdominis crosses the 9th costal cartilage (i.e., the transpyloric plane).
The body of the gallbladder lies beneath a line drawn from 5 cm upwards and to the left from the fundus.
The bile duct runs vertically downwards to reach the transpyloric plane 5 cm to the right of the midline, and then for a further 2.5 cm downwards and to the right to enter the ampulla of Vater halfway along the second part of the duodenum.
The spleen is located in the upper left quadrant. The postero-medial end of the spleen lies 5 cm to the left of the midline at the level between T10-T11 spines. The axis of the spleen extends antero-laterally along the line of the 10th rib and normally reaches no further forward than the mid-axillary line, so that the normal organ lies beneath ribs 9, 10, and 11.
The best way to mark the pancreas is to start at its neck. This lies on the transpyloric plane 1-2 cm to the right of the midline, behind the pylorus. The body extends from the neck along a line running upwards and to the left from 10cm to reach the hilum of the spleen. The head of the pancreas lies downwards and to the right of the neck, within the confine of the duodenal loop.
The hila of the kidneys lie approximately on the transpyloric plane, the right just below and the left just above (both 5 cm from the midline). These points lie just medial to the tops of the 9th costal cartilages.
The lower poles of the kidneys lie 7.5 cm from the midline at a level 2.5 cm above the supracristal plane. The upper poles lie only 2.5 cm from the midline at a level midway between the xiphisternal joint and the transpyloric plane. The length of each kidney is 11 cm. The true width of 6 cm is only represented as 4.5 cm on the surface due to the oblique position of the organs on the sides of the lumbar vertebrae.
Posteriorly, each kidney can be projected as the same obliquely set bean-shaped outline around the hilum, which lies at the level of the L1 spine (5 cm from the midline). The upper poles reach the level of T11 spine and so lie deep to the 12th rib. The lower poles lie at the level of L3 spine. The center of both adrenal glands lie symmetrically 3 cm above the transpyloric plane (3 cm form the midline).
The ureters and bladder
The ureters begin at points on the transpyloric plane (5 cm from the midline) and run downwards and slightly medially to enter the bladder at points marked superficially by the pubic tubercles. The neck of the bladder lies deep to the lower part of the pubic symphysis. The openings of the ureters lie behind the pubic tubercle. As the bladder is distended, the peritoneum is separated from the suprapubic region so that the bladder lies directly beneath the anterior abdominal wall (up to 5 cm above the pubic symphysis).