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Introduction to AbdomenAbdominal Wall

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The Human Abdomen

Between the pelvis and the thorax.

From the thorax (at the thoracic diaphragm) tothe pelvis at the pelvic brim.

The pelvic brim stretches from the lumbosacralangle (the intervertebral disk between L5 and S1) tothe pubic symphysis and is the edge of the pelvicinlet.

Functionally, the human abdomen is wheremost of the alimentary tract is placed.

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Regions of the Abdomen Transpyloric line

Half-way between the suprasternal notch and the topof the symphysis pubis.

Hilum of each kidney is below it, while its left endapproximately touches the lower limit of the spleen.

Ffirst lumbar vertebra behind.

Subcostal line

Lowest point of the subcostal arch (tenth rib).

Upper part of the third lumbar vertebra, and it is aninch or so above the umbilicus.

It indicates roughly the transverse colon, the lowerends of the kidneys.

Intertubercular line

Across between the two rough tubercles.

Body of the fifth lumbar vertebra.

Passes through or just above the ileo-caecal valve.

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What are the 4 horizontalplanes in the abdomenand what are theirvertebral levels?

Transpyloric: T1

Subcostal: L2/L3

Transumbilical: L3/L4

Transtubercular: L4/L5

What are the nine zonesand the planes thatdelineate them?

The two horizontal planesare the subcostal (L1) andthe transtuburcular (L4) andthe two vertical planes arethe midclavicular lines.

Hypochondrium, Epigastrium

Lumbar, Umbilicus

Inguinal, Illiac (Inguinal)

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Abdominal Cavity The abdominal cavity is lined with a protective membrane

termed the peritoneum.

The kidneys are located in the abdominal cavity behind theperitoneum, in the retroperitoneum.

The viscera are also covered, in the front, with a layer ofperitoneum called the greater omentum (or omental apron).

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Anterior Abdominal Wall

Layers of the abdominal wall are (from superficial to deep):

Skin

Fascia

Camper's fascia - fatty superficial layer. Scarpa's fascia - deep fibrous layer.

Muscle

Rectus abdominis

External oblique muscle Internal oblique muscle

Transverse abdominal muscle

Fascia transversalis

Peritoneum

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Fascia

Superficial:

Campers fascia

Continuous with fascia over thorax and thigh.

Fatty layer.

Deep Superficial:

Scarpas fascia

Membranous layer.

Continues into perineum as:

Superficial perineal fascia = Colles fascia.

Deep:

Thin layer covering abdominal muscles.

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Muscles

5 muscles attachmentsof the anteriorabdominal wall:

External oblique,

the internal oblique,

transversus abdominus,

rectus abdominus, and the pyramidalis.

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External Oblique

Proximal:

Outer surface of ribs 5-12

Distal:

Illiac crest

apponeurosis: linea alba

Action:

Compresses abdominal contents, bilateral

bending of trunk, unilateral flexion of trunkto same side, rotation of anterior abdomento opposite side.

Innervation:

Anterior rami of spinal nervesT7

-T

12

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Internal Oblique

Proximal:

Thoracolumbar fascia, illiac crest andinguinal ligament.

Distal: Inf. border of ribs 9-12,

Aponeorosis ends at linea alba, pubic crestand pectineal line.

Action:

Rotates abdomen to the same side.

Innervation:

L1

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Transversus Abdominus

Proximal:

Thoracolumbar fascia, illiac crest, lateral 2/3 of inguinalligament, costal cartilages of ribs 7-12.

Distal: Pubic crest , pectineal line,

Apponeurses end at linea alba

Actions:

Compresses abdomen.

Innervation:

L1

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Rectus Abdominus

Proximal:

Pubic crest, pubic tubercle, and pubic symphysis

Distal:

Costal cartilages of ribs 5-7, xiphiod process.

Actions:

Compress abdominal contents, flex vertebral column, tenseabdominal wall.

Innervations:

t7-t12

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Pyramidalis

Proximal:

pubis, pubic symphysis

Distal:

linea alba

Action:

tenses linea alba

Innervation:

Anterior ramus of spinal nerve T12

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Rectus Sheath Formed by the aponeuroses of the Obliqui and Transversus.

Contains the Rectus abdominis and Pyramidalis muscles.

Above the arcuate line

At the lateral margin of the Rectus, theaponeurosis of the Obliquus internusdivides into two lamellae:

One passes in front of the Rectus, blendingwith the aponeurosis of the Obliquusexternus.

the other, behind it, blending with theaponeurosis of the Transversus, andthese,

join at the medial border of the Rectus, areinserted into the linea alba.

Below the arcuate line:

Below this level, the aponeuroses of allthree muscles (including the internus)

pass in front of the Rectus

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Arcuate line

Also known as Linea semicircularis or Douglas' line

Horizontal line that demarcates the lower limit of the posteriorlayer of the rectus sheath.

Also where the inferiorepigastric vesselsperforate the rectusabdominus.

Occurs about 1/3 of thedistance from the umbilicusto the pubic crest, but thisvaries from person to person

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Transversalis Fascia

Thin aponeurotic membrane which liesbetween the inner surface of theTransversus abdominis and theextraperitoneal fascia.

Directly continuous with the iliac andpelvic fasciae.

In the inguinal region, the transversalisfascia is thick and dense in structureand is joined by fibers from the

aponeurosis of the Transversus, but

It becomes thin as it ascends to thediaphragm, and blends with the fasciacovering the under surface of thismuscle.

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Behind

Fat which covers the posterior surfaces of the kidneys.

Below

Posteriorly, to the whole length of the iliac crest, between theattachments of the Transversus and Iliacus;

Between the anterior superior iliac spine and the femoral vessels it isconnected to the posterior margin of the inguinal ligament, and isthere continuous with the iliac fascia.

Medial to the femoral vessels

it is thin and attached to the pubis and pectineal line, behind theinguinal falx, with which it is united;

it descends in front of the femoral vessels to form the anterior wall of

the femoral s

heat

h.

Beneath the inguinal ligament

it is strengthened by a band of fibrous tissue, which is only looselyconnected to the ligament, and is specialized as the iliopubic tract.

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Other Fascia

Fascia of Camper

A thick superficial layer ofthe anterior abdominal wall.

It is areolar in texture, andcontains in its meshes avarying quantity of adiposetissue.

It is found superficial toScarpa's fascia.

Fascia of Scarpa

A layer of the anteriorabdominal wall.

It is found deep to theCamper Fascia andsuperficial to the ExternalOblique muscle.

Thinner and moremembranous

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Connected to the aponeurosis of the Obliquus externusabdominis

In mid-line: Adherent to the linea alba and to the symphysis

pubis

Extends to the dorsum of the penis, forming the fundiformligament;

Continuous with the superficial fascia over the rest of the trunk

Blends with the fascia lata of the thigh, below the inguinalligament

Continued over the penis and spermatic cord to thescrotum.

From the scrotum it may be traced backward intocontinuity with the deep layer of the superficial fascia ofthe perineum

In the female, it is continued into the labia majora andfrom there to the fascia of Colles.

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Review The umbilicus.

Th

e linea alba is a median fibrous wh

ite line or band. The linea semilunaris is a curved line that extends from the 9th

costal cartilage to the pubic tubercle. This indicates the lateralborder of the rectus abdominis muscle.

The superficial fascia just above the inguinal ligament can be

divided into two layers:

There is a fatty superficial layer (Camper's fascia)

There is also a membranous deep layer (Scarpa's fascia)

The superficial vessels and nerves run between these two

layers. The membranous deep layer is continuous with the superficial

fascia of the thigh, the fascia lata.

This layer is also continuous with the superficial fascia of theperineum (Colles' fascia) and with that investing the scrotum

and penis and the labia majora.

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Inguinal Ligament

Band running from thepubic tubercle to theanterior superior iliacspine.

It is formed by theexternal abdominaloblique aponeurosisand is continuous withthe fascia lata of thethigh.

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Lacunar Ligament

The lacunar ligament is that part of the aponeurosis of theObliqus externus which is reflected backward and laterally,and is attached to the pectineal line.

Its base is concave, thin, and sharp, and forms the medialboundary of the femoral ring.

Its apex corresponds to the pubic tubercle.

Its posterior margin is attached to the pectineal line, and iscontinuous with the pectineal fascia.

Its anterior margin is attached to the inguinal ligament.

Its surfaces are directed upward and downward.

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Ligament of Cooper

This is a strong fibrous band.

It extends lateralward from the base of the lacunar ligamentalong the pectineal line, to which it is attached.

It is strengthened by t

he pectineal fascia, and by a lateralexpansion from the lower attachment of the linea alba.

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Posterior Abdominal Wall

The posterior abdominal wall is composedprincipally of muscles and fascia attached to thevertebrae, hip bones, and ribs.

Muscles of the Post. Wall:

psoas major,

iliacus, and

quadratus lumborum.

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Quadratus Lumborum Muscle

It lies adjacent to the transverseprocesses of the lumbar

vertebrae and is broaderinferiorly.

Superior attachments: medial halfof inferior border of 12th rib andtips of lumbar transverse

processes.

Inferior attachments: iliolumbarligament and internal lip of theiliac crest.

Innervation: Ventral branches ofT12 and L1 to L4

Functionv: Extends and laterallyflexes the vertebral column, andfixes the 12th rib during

inspiration.

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Psoas Major Muscle

Passes from the abdomen tothe thigh deep to the

inguinal ligament.

The lumbar plexus isimbedded in this muscle.

Proximal attachments are:

sides ofT12 to L5vertebrae and intervertebraldiscs between them.

Distal attachment is: lesser

trochanter of femur

Innervation: ventral rami oflumbar nerves (L1, L2, andL3)

The Iliacus Muscle

Large triangular or fan-shapedmuscle lies along the lateral

side of the psoas major in thepelvis.

Proximal attachments are: iliaccrest, iliac fossa, ala of

sacrum, and anterior sacroiliacligaments.

Distal attachments are: tendon ofpsoas major and body offemur, inferior to lesser

trochanter.

Innervation: femoral nerve (L2and L3)

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