This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The spleen lies under the ninth, tenth, and eleventh ribs of the left side. Its long axis follows the tenth rib. Its anterior end is at the midaxillary line, while its posterior end reaches to within 4 cm. (1 1/2 in.) of the median line.
The lower edge of the right kidney reaches to within an inch of the level of the umbilicus; this is about opposite the level of the third lumbar spine. The left is 1.25 to 2 cm. (1/2 to 3/4 in.) higher. This leaves about 4 cm. (1 1/2 in.) between the lower edge of the kidneys and the highest point of the iliac crests. Their upper edge is almost or quite up to the level of the tip of the xiphoid cartilage. The pelvis of the kidney and commencement of the ureter are 5 cm. (2 in.) from the median line, about on the level of a line joining the upper ends of the lineae semi-lunares. Posteriorly the right kidney rises to the lower border of the eleventh rib, the left kidney to the upper border. The outer edge of the kidney is a little beyond the outer borders of the erector spinas and quadratus lumborum muscles.
Duodenum. - The duodenum begins at the pylorus and curves first upward and then downward along the right of the spine to the body of the third lumbar vertebra; it then crosses and ascends to the left side of the body of the second. This places it just above the umbilicus in the median line and behind the transverse colon.
The upper extremity of the root or attachment of the mesentery begins 2.5 cm. (1 in.) to the left of the median line and 7.5 cm. (3 in.) above the umbilicus. It runs obliquely downward and to the right for about 15 cm. (6 in.) to a point below and to the right of the umbilicus, over the right sacro-iliac joint, and 8 to 10 cm. (3 to 4 in.) above the middle of a line joining the anterior superior spine and the symphysis pubis.
The coils of the jejunum lie mostly to the left of the median line, but some are also found in the pelvis.
The coils of the ileum lie mostly to the right of the median line, and also are found in the pelvis.
Caecum. - The caecum lies in the right iliac fossa between the linea semilunaris and the anterior iliac spine.
The ileocaecal valve lies 8 to 10 cm. (3 to 4 in.) above the middle of Poupart's ligament.
McBurney's point is 4.5 cm. (1 3/4 in.) above and to the inner side of the right anterior superior iliac spine on a line to the umbilicus.
The base of the appendix is 2 cm. (3/4 in.) below the ileocaecal valve. This is a little (1 in.) below the point where the linea semilunaris is crossed by a line drawn from the anterior iliac spine to the umbilicus, and is opposite the level of the anterior spine.
This lies just to the outer side of the gall-bladder, under the ninth costal cartilage.
The lower edge of the transverse colon is about at the level of the umbilicus.
This rises higher than the hepatic flexure, about to the level of the eighth costal interspace.
When empty the bladder sinks into the pelvis. When distended it rises toward the umbilicus, carrying the peritoneal fold with it so as to leave a space of 2.5 to 5 cm. (1 to 2 in.) between it and the top of the pubis.
The aorta bifurcates on the body of the fourth lumbar vertebra 2 cm. (3/4 in.) below and to the left of the umbilicus. A line from this point to the middle of one drawn from the anterior superior spine to the symphysis pubis indicates the course of the iliac arteries. The upper third of this line is the common iliac and the lower two-thirds the external iliac. The ureters cross the points of bifurcation of the common iliac arteries. The caeliac axis lies just below the tip of the ensiform cartilage. The renal arteries are about 5 cm. (2 in.) lower. The iliac veins lie along the inner side of the iliac arteries, and the ascending cava runs along the right side of the aorta.
The deep epigastric arteries run lengthwise at or a little outside of the middle of the recti muscles. They pass beneath the edge of the recti a little below the level of aline joining the umbilicus and middle of Poupart's ligament.