Abdomen Anatomy Set 4

The sympathetic trunks pass deep to the
medial arcuate ligament. There are two small
apertures in each crus of the diaphragm; one
transmits the greater and the other the lesser
splanchnic nerve

The inferior or horizontal (3rd) part of the
duodenum runs transversally to the left, passing over the inferior vena cava, aorta, and L3 vertebra. It is crossed by the superior mesenteric
artery and vein and the root of the mesentery

The diaphragm is attached on each side to
the medial and lateral arcuate ligaments, which
are thickenings of the fascia covering the psoas
major and quadratus lumborum muscles,
respectively

In the current terminology, the left liver
includes the caudate lobe and most of the
quadrate lobe. The anatomical left lobe is separated from these lobes on the visceral surface by  the fissure for the round ligament of the liver
and the fissure for the ligamentum venosum;
on the diaphragmatic surface the anatomical
left lobe is separated by the attachment of the
falciform ligament

The inferior vena cava begins anterior to
the L5 vertebra by the union of the common
iliac veins. The union occurs approximately
2.5 cm to the right of the median plane, inferior
to the bifurcation of the aorta and posterior to
the proximal part of the right common iliac
arteryThe inferior vena cava begins anterior to
the L5 vertebra by the union of the common
iliac veins. The union occurs approximately
2.5 cm to the right of the median plane, inferior
to the bifurcation of the aorta and posterior to
the proximal part of the right common iliac
artery

The bifurcation of the aorta can be located
on the surface anatomy approximately 2.5 cm
superior to the transpyloric plane to a point
slightly inferior to and to the left of the umbilicus. Bifurcation is also indicated just to the left of the midpoint of a line joining the highest
points of the iliac crests

The nerves of the kidneys and suprarenal
glands are derived from the celiac plexus, the
lesser and least thoracic splanchnic nerves, and
the aorticorenal ganglion

The pelvic splanchnic nerves are distinct
from other splanchnic nerves in that they have
nothing to do with the sympathetic trunks and
are derived directly from ventral rami of spinal
nerves S2 through S4. They also convey presynaptic parasympathetic fibers to the inferior hypogastric plexus

The esophagus is a muscular tube (approximately 25 cm long) that extends from the pharynx to the stomach. It normally has four constrictions and is crossed by the arch of the aorta and the left main bronchus

The psoas muscle is a long, thick, fusiform muscle that lies lateral to the lumbar vertebrae. Psoas is a Greek word meaning “muscle
of the loin.” The muscle passes inferolaterally,
deep to the inguinal ligament to reach the lesser
trochanter of the femur. The lumbar plexus of
nerves is embedded in the posterior part of the
psoas

The parasympathetic root of the celiac
plexus is a branch of the posterior vagal trunk
that contains fibers from the right and left vagal
nerves. The sympathetic roots of the plexus are
the greater and lesser splanchnic nerves

The diaphragm, the chief muscle of inspiration, descends during inspiration. Only its central part moves because its periphery, as the
fixed origin of the muscle, attaches to the inferior
margin of the thoracic cage and the superior
lumbar vertebrae

Digestion occurs mainly in the stomach
and duodenum. Peristalsis—ring-like, contraction waves that begin around the middle of the stomach and move slowly toward the
pylorus—is responsible for mixing the masticated food mass with gastric juices and for
emptying the contents of the stomach into the
duodenum

Most reabsorption occurs in the ascending colon

The suprarenal medulla is derived from
neural crest cells associated with the sympathetic nervous system. The chromaffin cells of the medulla are related to sympathetic (postganglionic) neurons in both derivation (neural crest cells) and function. These cells secrete
catecholamines (mostly epinephrine) into
the bloodstream in response to signals from
presynaptic neurons

For several weeks the rapidly growing
midgut, supplied by the superior mesenteric
artery, is physiologically herniated into the
proximal part of the umbilical cord. It is attached to the yolk sac by the yolk stalk. As it
returns to the abdominal cavity, the midgut
rotates 270 degrees around the axis of the
superior mesenteric artery

The splenic artery is the largest branch of
the celiac trunk. It follows a tortuous course
posterior to the omental bursa, anterior to the
left kidney, and along the superior border
of the pancreas. It divides into five or more
branches that enter the hilum of the spleen

The stomach, spleen, mesentery, and intestine may herniate into the thorax when there is
a traumatic diaphragmatic hernia

The crura of the diaphragm are musculotendinous bundles that arise from the anterior surfaces of the bodies of the superior three
lumbar vertebrae, the anterior longitudinal
ligament, and the intervertebral discs

The central tendon of the diaphragm has
no bony attachments and is incompletely divided into three leaves, resembling a wide
cloverleaf. Although it lies near the center of the
diaphragm, the central tendon is closer to the
anterior part of the thorax. The inferior vena
cava perforates the central tendon. The aortic
hiatus is formed by the right and left muscular
crura

The esophageal hiatus is an oval aperture
for the esophagus in the muscle of the right crus
of the diaphragm at the level of the T10 vertebra. The esophageal hiatus also transmits the anterior and posterior vagal trunks, esophageal
branches of the left gastric vessels, and a few
lymphatics

The left gastro-omental artery arises from
the splenic artery and courses along the
greater curvature to anastomose with the right
gastro-omental artery

The appendicular artery is located in the
mesoappendix and the anterior cecal artery is
located in the superior ileocecal fold. Both the
appendix and cecum are vascular. The inferior
ileocecal fold is avascular

The smooth surface of the gastric mucosa,
mucous layer of the stomach, is thrown into
longitudinal ridges when contracted. These
are the gastric folds or rugae and most obvious
along the greater curvature of the stomach

In a small proportion of individuals, the
inferior end of the thoracic duct—which begins
with the convergence of the main lymphatic
ducts of the abdomen—takes the form of the
commonly depicted, thin-walled sac or dilation
known as the cisterna chyli