Abdominal Wall
Landmarks: bony & soft
• costal arch: formed by #7-10 costal
cartilages
– a. infrasternal angle - sharp upward angle at
midline, xiphoid process at the apex
– b. epigastric fossa - depression just inferior to
xiphoid
Coxal bones
• Three bones fused together
• ilium: anterior superior iliac spine; iliac
crest
• ischium
• pubis: pubic symphysis,
• inguinal ligament (below): indicated at
surface by depression separating leg from
abdomen
Abdominal wall
• Linea alba: midline from xiphoid to pubic
bone, umbilicus - at level of L4
• Linea semilunaris: parallels linea alba on
each side; marks lateral border of rectus
abdominis
• Tendinous intersections: 3 horizontal
divisions of rectus abdominis between
linea semilunaris
Regions
Superficial vessels
• thoracoepigastric veins: drain laterally
from umbilical level up
• anterior perforating veins: closer to midline
• umbilical venous plexus (caput medusae
may seen in portal hypertension)
• superficial epigastric artery, vein
• superficial circumflex iliac artery vein
Nerves
• Thoracoabdominal nerve: continuations of
intercostals 7-11 & subcostal from thorax to
abdomen, between internal oblique & transverse
abdominis
• Anterior, lateral cutaneous nerve: terminal
branches of thoracoabdominal nerve to the
surface
– T7-9 to skin superior to umbilicus
– T10 to skin surrounding umbilicus
– T11-12, L1 to skin inferior to umbilicus
• Iliohypogastric nerve: to skin over inguinal region
• Ilioinguinal nerve: just inferior to iliohypogastric to
skin of superior, medial thigh
Muscles
•
•
•
•
External oblique muscle
Internal oblique muscle
Transversus abdominis
Rectus abdominis
EXTERNAL ABDOMINAL OBLIQUE
• Origin
– Anterior fibers: external surfaces of ribs five
through eight interdigitating with serratus anterior
– lateral fibers: external surface of ninth rib,
interdigitating with serratus anterior; and external
surfaces of 10th, 11 th ans 12th ribs, interdigitating
with latissnus dorsi
• Insertion
– Anterior fibers: into a board, flat aponeurosis,
terminating in the linea alba, which is a tendinous
rephe which extends from the xiphoid
– Lateral fibers: as the inguinal ligament, into
anterior superior spine and public tubercle, and
into the external lip of anterior one half of iliac
crest.
EXTERNAL ABDOMINAL OBLIQUE
• Action
– Anterior fibers: acting bilaterally, the anterior
fibers flex the vertebral column approximating
the thorax and pelvis anteriorly, support and
compress the abdominal viscera, depress the
thorax, and assist in respiration. Acting
unilaterally with the anterior fibers of the
Internal Oblique on the opposite site, the
anterior fibers of External Oblique rotate the
vertebral column, bring the thorax forward
(when the pelvis is fixed), or the pelvis
backward (when the thorax is fixed). For
example, with the pelvis fixed, the right
external oblique rotates the thorax
counterclockwise, and the left external oblique
rotates the thorax clockwise.
EXTERNAL ABDOMINAL OBLIQUE
• Action
– Lateral fibers: acting bilaterally, the lateral
fibers of the external oblique flex the vertebral
column, with major influence on the lumbar
spine, titling the pelvis posteriorly. Acting
unilaterally with the lateral fibers of the internal
oblique on the same side, these fibers of the
external oblique laterally flex the vertebral
column, approximating the thorax and iliac
crest. These external oblique fibers also act
with the internal oblique on the opposite side
to rotate the vertebral column. The external
oblique, in its action on the thorax, is
comparable to the sternocleidomastoid in its
action on the head.
EXTERNAL ABDOMINAL OBLIQUE
• Nerve
– Anterior fibers: T5, 6, T7-T12
– Lateral fibers: T5, 6, T7-T12
• Direction of the fibers:
– Anterior fibers: the fibers extend
obliquely downward and medialward
with the uppermost fibers from the
xiphoid
– Lateral fibers: fibers extend obliquely
downward and medialward, more
downward than the anterior fibers
INTERNAL ABDOMINAL OBLIQUE
• Origin
– Lower anterior fibers: middle one third of
intermediate line of iliac crest, and
thoracolumbar fascia
– Upper anterior fibers: anterior one third of
intermediate line of iliac crest
– Lateral fibers: middle one third of intermediate
line of iliac crest, and thoracolumbar fascia
• Insertion
– Lower anterior fibers: inferior borders of 10th,
11th, and 12th ribs and linea alba by means of
aponeurosis
– Upper anterior fibers: linea alba by means of
aponeurosis
– Lateral fibers: inferior borders of 10th, 11th,
and 12th ribs and linea alba by means of
aponeurosis
INTERNAL ABDOMINAL OBLIQUE
• Action
– Lower anterior fibers: acting bilaterally,
the lateral fibers flex the veterbral
column, approximating the thorax and
pelvis anteriorly, and depress the
thorax. Acting unilaterally with the
lateral fibers of the external oblique on
the same side, these fibers of the
internal oblique laterally flex the
vertebral column, approximating the
thorax and pelvis. These fibers also act
with the external oblique on the
opposite side to rotate the vertebral
column.
INTERNAL ABDOMINAL OBLIQUE
• Action
– Upper anterior fibers: acting bilaterally, the
upper anterior fibers flex the vertebral column,
approximating the thorax and pelvis anteriorly,
support and compress the abdominal viscera,
depress the thorax, and assist in respiration.
Acting unilaterally, in conjuction with the
anterior fibers of the external oblique on te
oppisite side, the ipper anterior fibers of the
internal oblique rotate the vertebral column,
bringing the thorax backward (when the pelvis
is fixed), or the pelvis forward (when the thorax
is fixed). For example, the right internal
oblique rotates the thorax clockwise and the
left internal oblique rotates the thorax
couinterclockwise on a fixed pelvis.
INTERNAL ABDOMINAL OBLIQUE
• Action
– Lateral fibers: acting bilaterally, the
lateral fibers flex the veterbral column,
approximating the thorax and pelvis
anteriorly, and depress the thorax.
Acting unilaterally with the lateral
fibers of the external oblique on the
same side, these fibers of the internal
oblique laterally flex the vertebral
column, approximating the thorax and
pelvis. These fibers also act with the
external oblique on the opposite side
to rotate the vertebral column.
INTERNAL ABDOMINAL OBLIQUE
• Nerve
– Lower anterior fibers: T7-11, T12,
iliohypogastric and ilioinguinal, ventral rami
– Upper anterior fibers: T7-11, T12,
iliohypogastric and ilioinguinal, ventral
– Lateral fibers: T7-11, T12, iliohypogastric and
ilioinguinal, ventral rami
• Direction of fibers:
– Lower anterior fibers: fibers extend obliquely
upward and medialward, more upward than the
anterior fibers
– Upper anterior fibers: fibers extend obliquely
medialward and upward
– Lateral fibers: fibers extend obliquely upward
and medialward, more upward than the
anterior fibers
•
TRANSVERSUS ABDOMINIS
• Origin
– inner surfaces of cartilages of lower six ribs,
interdigitating with the diaphragm; thoracolumbar
fascia; anterior three fourths of internal lip of iliac
crest; and lateral one third of inguinal ligament
• Action
– Acts likes a girdle to flatten the abdominal wall and
compress the abdominal viscera; upper portion
helps to decrease the infrasternal angle of the ribs
as in expiration. This muscle has no action in
lateral trunk flexion except that it acts to compress
the viscera and stabilize the linea alba, thereby
permiting better action by anteriolateral trunk
muscles
• Insertion
– linea alba by means of a board aponeurosis, pubic
crest and pectin publis
• Nerve
– T7-T12, iliohypogastric, ilioinguinal, ventral
divisions Direction of fibers: transverse (horizontal)
RECTUS ABDOMINIS
• Origin
– pubic crest and symphysis
• Action
– flexes the vertebral column by approximating the
thorax and pelvis anteriorly. With the pelvis fixed,
the thorax will move toward the pelvis; with the
thorax fixed, the pelvis will move toward the
thorax.
• Insertion
– costal cartilages of fifth, sixth, and seventh ribs,
and xiphiod process of sternum
• Nerve
– T5-T12, ventral rami
Inguinal triangle
• bounded by
– lateral border of rectus abdominis muscle
medially
– inguinal ligament inferiorly
– inferior epigastric artery laterally
Inguinal canal
• roof:
– internal oblique & transversus abdominis muscle
• posterior wall:
– transveralis fascia, reinforced medially by conjoint
tendon (internal oblique & transversus abdomilis
muscle)
• Floor:
– Superior surface of inguinal ligament
• Anterior wall:
– aponeurosis of the external oblique muscle
• Superficial & deep ring
• Graham “Mr Europe"
Black had his hernia
repaired at the
Centre on Friday
and on Monday he
was ‘working-out' at
the gym! (not always
recommended for
the rest of us!)