Abdomen
2
INTRODUCTION
The abdomen is that portion of the trunk inferior to the
diaphragm and superior to the pelvis with which it is con-
tinuous. The abdomen extends inferiorly to the superior
pelvic aperture.
AREAS AND FASCIA OF THE ABDOMEN
Areas of the abdomen
Area Structure Significance
Abdominal cavity Boundaries: Larger, superior part of the
• Superior— abdominopelvic cavity
diaphragm
• Inferior—
continuous with
pelvic cavity at
superior pelvic
aperture
• Anterolateral—
muscular abdominal
wall
• Posterior—
vertebral column
Regions (9) Divided into regions • Regions:
by: • Right and left
• 2 horizontal hypochondriac
planes—subcostal • Right and left inguinal
and transtubercular • Right and left lateral
• 2 vertical- • Epigastric
midclavicular • Umbilical
planes • Pubic
• Used for description of
organ location or location
of pathologic processes
(continued)
33
,34 CLINICAL ANATOMY FOR YOUR POCKET
Areas of the abdomen (continued)
Area Structure Significance
Quadrants (4) Divided into • Quadrants:
quadrants by a • Right and left upper
horizontal • Right and left lower
(transumbilical) and a • Used for description of
vertical (median) organ location or location
plane of pathologic processes
Inguinal canal • 4–6 cm long, • Transmits the spermatic
inferomedially cord or round ligament of
directed passage the uterus, ilioinguinal
extending between nerve, and the genital
the deep and branch of the
superficial inguinal genitofemoral nerve
rings • One result of the oblique
• Walls of canal: nature of canal is that the
• Anterior— superficial and deep rings
external oblique do not overlap; therefore,
aponeurosis increases in intra-
• Posterior— abdominal pressure force
transversalis the canal “closed” to
fascia and prevent herniation
medially the
conjoint tendon
• Roof—
transversalis
fascia and arching
fibers of the
internal oblique
and transversus
abdominis
• Floor—iliopubic
tract, inguinal
ligament, and
lacunar ligament
from lateral to
medial
Subinguinal space Space located deep to Serves to connect the
the inguinal ligament abdominopelvic cavity with
and iliopubic tract the lower limb
Additional Concepts
Deep Inguinal Ring
The deep inguinal ring, the internal opening of the inguinal
canal, is an evagination of transversalis fascia, just superior
to the middle of the inguinal ligament and immediately lat-
eral to the inferior epigastric vessels.
, CHAPTER 2 | ABDOMEN 35
Superficial Inguinal Ring
The superficial inguinal ring is the slitlike external open-
ing of the inguinal canal in the aponeurosis of the external
oblique muscle, just superior to the public tubercle. The
medial and lateral margins of the opening are the medial
and lateral crura, which are prevented from spreading
apart by intercrural fibers.
Structures of the abdominal wall
Feature Description
Superficial fascia Inferior to umbilicus, it is composed of 2 layers:
• A superficial fatty layer (Camper’s fascia)
• A deep membranous layer (Scarpa’s fascia)
Investing fascia Covers the muscles (4) forming the muscular wall of
the abdomen
Endoabdominal fascia • Lines inner surface of abdominal wall
• Named according to muscle it lines:
• Transversalis fascia lines the transverse
abdominal muscle
• Divided into anterior, middle, and posterior
layers
• Middle and posterior layers enclose the
intrinsic muscles of the back—relatively
thick, provides attachment for anterolateral
abdominal wall muscles
• Anterior layer is fascia of quadratus
lumborum muscle—thickened superiorly to
form lateral arcuate ligament, inferiorly
attaches to iliolumbar ligament
• Lumbar fascia lines the quadratus lumborum
• Psoas fascia lines the psoas major muscle
• It is thickened superiorly to form the medial
arcuate ligament
• It is continuous with the thoracolumbar
fascia
Parietal peritoneum • Lines abdominopelvic cavity
• Located deep to the endoabdominal fascia
from which it is separated by extraperitoneal
fat
Rectus sheath • Formed by the aponeuroses of the external and
internal oblique and transverse abdominal
• The sheath contains the rectus abdominis,
the superior and inferior epigastric vessels,
the pyramidalis, segmental nerves, and
lymphatics
(continued)
, 36 CLINICAL ANATOMY FOR YOUR POCKET
Structures of the abdominal wall (continued)
Feature Description
Conjoint tendon • Fused tendons of internal oblique and transverse
abdominal at their attachment to the pubis
• Forms medial portion of posterior wall of inguinal
canal
Inguinal ligament • Free, fibrous inferior edge of external oblique,
extending between the anterior superior iliac
spine and pubic tubercle
• Laterally provides attachment for transverse
abdominal and internal oblique
Iliopubic tract • Thickened inferior margin of the transversalis
fascia
• Forms portion of floor and posterior wall of
inguinal canal
• Located posterior and parallel to the inguinal
ligament
• Forms the anterior boundary of the subinguinal
space
Lacunar ligament • Medial-most internally directed portion of the
inguinal ligament
• Forms portion of floor of inguinal canal
• Attaches to superior pubic ramus
Pectineal ligament Continuation of lacunar ligament as it runs along
the pectin pubis
Additional Concept
Rectus Sheath
Rectus sheath—Above a line midway between the
pubic symphysis and umbilicus the anterior layer of the
sheath is formed by the external oblique and the ante-
rior portion of the internal oblique, which splits to con-
tribute to the posterior layer of the sheath with the
transverse abdominal muscle. Below this line, the
sheath is deficient posteriorly, with the aponeurosis of
all three muscles forming the anterior layer of the
sheath, with only the transversalis fascia separating the
rectus abdominis from the parietal peritoneum. The
lower edge of the aponeurotic “line” of the posterior
sheath is the arcuate line.
2
INTRODUCTION
The abdomen is that portion of the trunk inferior to the
diaphragm and superior to the pelvis with which it is con-
tinuous. The abdomen extends inferiorly to the superior
pelvic aperture.
AREAS AND FASCIA OF THE ABDOMEN
Areas of the abdomen
Area Structure Significance
Abdominal cavity Boundaries: Larger, superior part of the
• Superior— abdominopelvic cavity
diaphragm
• Inferior—
continuous with
pelvic cavity at
superior pelvic
aperture
• Anterolateral—
muscular abdominal
wall
• Posterior—
vertebral column
Regions (9) Divided into regions • Regions:
by: • Right and left
• 2 horizontal hypochondriac
planes—subcostal • Right and left inguinal
and transtubercular • Right and left lateral
• 2 vertical- • Epigastric
midclavicular • Umbilical
planes • Pubic
• Used for description of
organ location or location
of pathologic processes
(continued)
33
,34 CLINICAL ANATOMY FOR YOUR POCKET
Areas of the abdomen (continued)
Area Structure Significance
Quadrants (4) Divided into • Quadrants:
quadrants by a • Right and left upper
horizontal • Right and left lower
(transumbilical) and a • Used for description of
vertical (median) organ location or location
plane of pathologic processes
Inguinal canal • 4–6 cm long, • Transmits the spermatic
inferomedially cord or round ligament of
directed passage the uterus, ilioinguinal
extending between nerve, and the genital
the deep and branch of the
superficial inguinal genitofemoral nerve
rings • One result of the oblique
• Walls of canal: nature of canal is that the
• Anterior— superficial and deep rings
external oblique do not overlap; therefore,
aponeurosis increases in intra-
• Posterior— abdominal pressure force
transversalis the canal “closed” to
fascia and prevent herniation
medially the
conjoint tendon
• Roof—
transversalis
fascia and arching
fibers of the
internal oblique
and transversus
abdominis
• Floor—iliopubic
tract, inguinal
ligament, and
lacunar ligament
from lateral to
medial
Subinguinal space Space located deep to Serves to connect the
the inguinal ligament abdominopelvic cavity with
and iliopubic tract the lower limb
Additional Concepts
Deep Inguinal Ring
The deep inguinal ring, the internal opening of the inguinal
canal, is an evagination of transversalis fascia, just superior
to the middle of the inguinal ligament and immediately lat-
eral to the inferior epigastric vessels.
, CHAPTER 2 | ABDOMEN 35
Superficial Inguinal Ring
The superficial inguinal ring is the slitlike external open-
ing of the inguinal canal in the aponeurosis of the external
oblique muscle, just superior to the public tubercle. The
medial and lateral margins of the opening are the medial
and lateral crura, which are prevented from spreading
apart by intercrural fibers.
Structures of the abdominal wall
Feature Description
Superficial fascia Inferior to umbilicus, it is composed of 2 layers:
• A superficial fatty layer (Camper’s fascia)
• A deep membranous layer (Scarpa’s fascia)
Investing fascia Covers the muscles (4) forming the muscular wall of
the abdomen
Endoabdominal fascia • Lines inner surface of abdominal wall
• Named according to muscle it lines:
• Transversalis fascia lines the transverse
abdominal muscle
• Divided into anterior, middle, and posterior
layers
• Middle and posterior layers enclose the
intrinsic muscles of the back—relatively
thick, provides attachment for anterolateral
abdominal wall muscles
• Anterior layer is fascia of quadratus
lumborum muscle—thickened superiorly to
form lateral arcuate ligament, inferiorly
attaches to iliolumbar ligament
• Lumbar fascia lines the quadratus lumborum
• Psoas fascia lines the psoas major muscle
• It is thickened superiorly to form the medial
arcuate ligament
• It is continuous with the thoracolumbar
fascia
Parietal peritoneum • Lines abdominopelvic cavity
• Located deep to the endoabdominal fascia
from which it is separated by extraperitoneal
fat
Rectus sheath • Formed by the aponeuroses of the external and
internal oblique and transverse abdominal
• The sheath contains the rectus abdominis,
the superior and inferior epigastric vessels,
the pyramidalis, segmental nerves, and
lymphatics
(continued)
, 36 CLINICAL ANATOMY FOR YOUR POCKET
Structures of the abdominal wall (continued)
Feature Description
Conjoint tendon • Fused tendons of internal oblique and transverse
abdominal at their attachment to the pubis
• Forms medial portion of posterior wall of inguinal
canal
Inguinal ligament • Free, fibrous inferior edge of external oblique,
extending between the anterior superior iliac
spine and pubic tubercle
• Laterally provides attachment for transverse
abdominal and internal oblique
Iliopubic tract • Thickened inferior margin of the transversalis
fascia
• Forms portion of floor and posterior wall of
inguinal canal
• Located posterior and parallel to the inguinal
ligament
• Forms the anterior boundary of the subinguinal
space
Lacunar ligament • Medial-most internally directed portion of the
inguinal ligament
• Forms portion of floor of inguinal canal
• Attaches to superior pubic ramus
Pectineal ligament Continuation of lacunar ligament as it runs along
the pectin pubis
Additional Concept
Rectus Sheath
Rectus sheath—Above a line midway between the
pubic symphysis and umbilicus the anterior layer of the
sheath is formed by the external oblique and the ante-
rior portion of the internal oblique, which splits to con-
tribute to the posterior layer of the sheath with the
transverse abdominal muscle. Below this line, the
sheath is deficient posteriorly, with the aponeurosis of
all three muscles forming the anterior layer of the
sheath, with only the transversalis fascia separating the
rectus abdominis from the parietal peritoneum. The
lower edge of the aponeurotic “line” of the posterior
sheath is the arcuate line.
