Abdomen

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24 Topographic Anatomy

STUDYAIMS

At the end of your study, you should be able to

Understand the boundaries of the abdominal cavity

Identifysurface landmarks of the abdomen

Know the four quadrants of the abdomen and their contents

Know the nine regions of the abdomen

Know the lines and planes that create the four quadrants and nine regions

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GUIDE

Abdomen: Topographic Anatomy

[Plate 240, Abdomen]

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[Plate 242, Regions and Planes of Abdomen]

Abdomen: General description

Lies between the diaphragm and the pelvic inlet.

Is the largest cavityin the bodyand is continuous with the pelvic cavity. Lined with parietal peritoneum, a serous membrane

Bounded superiorlybythe diaphragm

Has a concave dome

Spleen, liver, part of the stomach, and part of the kidneys lies under the dome and are protected bythe lower ribs and costal cartilages.

Lower extent lies in the greater pelvis

Between the ala or wings of the ilia

Ileum, cecum, and sigmoid colon thus partlyprotected Anterior and lateral walls composed of muscle

Viscera in these areas are more likelyto be damaged byblunt force and penetrating injuries. Posterior wall comprised of vertebral column, the lower ribs, and associated muscles

Protect the abdominal contents.

Bony landmarks of the abdomen

Xiphoid process

Lower sixcostal cartilages

Anterior ends of the lower sixribs (ribs 7 to 12) (Section 3-3: Thorax-Body Wall)

Lumbar vertebrae (L1 to L5)

Pelvis

Iliac crest

Anterior superior iliac spine (ASIS)

Anterior inferior iliac spine

Pubic symphysis

Pubic crest and pubic tubercle

Abdomen: Topographical anatomy

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Costal margin: Formed bythe medial borders of the 7th through 10th costal cartilages Rectus sheath

From xiphoid process and 5th through 7th costal cartilages → pubic symphysis and pubic crest

Contains rectus abdominis muscle (Section 4-2: Abdomen-Body Wall) Linea alba

Aslight indentation that can sometimes be seen extending from the xiphoid process to the pubic symphysis

Afibrous raphe where the aponeuroses of the external and internal abdominal oblique and the transversus abdominis muscles on either side unite.

Semilunar line (linea semilunaris)

Vertical indentation seen as a curved line from the tip of the ninth rib cartilage to the pubic tubercle on each side in well-muscled individuals

Represents the lateral edge of the rectus abdominus muscle Tendinous intersections

Transverse attachments between the anterior rectus sheath and rectus abdominis muscle

Maybe seen as transverse grooves in skin on either side of midline (six-pack) Inguinal ligament

From ASIS to pubic tubercle of pelvis

Folded inferior edge of external abdominal aponeurosis

Separates abdominal region from thigh Umbilicus

At approximate level of intervertebral disc between the L3 and L4

Marks the T10 dermatome Liver

Mainlyin the right upper quadrant, behind ribs 7 through 11 on the right side

Crosses the midline to reach towards the left nipple (Section 4-5: Abdomen-Viscera (Accessory Organs))

Spleen

Beneath ribs 9 through 11 on the left side

10th rib is axis of spleen Kidneys

Located in loin region

Left kidneyis higher than right (pelvis at L1/2 on left and L2/3 on right) (Section 4-8: Abdomen-Kidneys and Suprarenal Glands)

Abdominal contents

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Gastrointestinal tract

Stomach

Duodenum

Ileum

Jejunum

Cecum and appendix

Ascending, transverse and descending colon

Part of the sigmoid colon

Accessorydigestive organs

Liver

Gallbladder

Pancreas

Spleen

Suprarenal glands

Urinarysystem-kidneys and ureters

Kidneys are the onlyorgans developing beneath the parietal peritoneum

Never have a mesentery

Thus are primarilyretroperitoneal

Organs that develop within the abdominal cavityand then become retroperitoneal

Are called secondarilyretroperitoneal

Pancreas

Two thirds of the duodenum

Ascending and descending colon.

All the rest of the organs are peritoneal

Lie within the peritoneal cavity

Covered bya layer of visceral peritoneum

Visceral peritoneum is continuous with the parietal peritoneum lining the cavityvia a mesentery.

Abdominal regions

Abdominal quadrants

Clinicians usuallydivide the abdomen is into four quadrants for descriptive purposes, using the following planes:

Median plane: imaginaryvertical line following the line alba from the xiphoid process to the pubic symphysis

Transumbilical plane: imaginaryhorizontal line at the level of the umbilicus

These lines or planes create four quadrants

Right upper

Left upper

Right lower

Left lower Abdominal regions

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Clinicians maydivide the abdomen into nine regions

For more accurate descriptive and diagnostic purposes

Use two vertical and three horizontal lines or planes

Horizontal planes (in descending order):

Subcostal plane: passes through the lower border of the 10th costal cartilage on either side

Sometimes the transpyloric plane is used instead of the subcostal; passes through the pylorus on the right and the tips of the ninth costal cartilage on either side

Transumbilical plane: passes through the umbilicus at the level of the L3/4 intervertebral disc

Transtubercular (intertubercular) plane: passes through the tubercles of the iliac crests and the bodyof L5

Vertical planes

Right midclavicular line

Left midclavicular line

Pass from the midpoint of the clavicle to the midpoint of inguinal ligament.

These planes create nine abdominal regions:

Right and left hypochondriac regions, superiorlyon either side

Right and left lumbar (flank) regions, centrallyon either side

Right and left inguinal (groin) regions, inferiorlyon either side

Epigastric region superiorlyand centrally

Umbilical region, with the umbilicus as its center

Hypogastric or suprapubic region, inferiorlyand centrally Descriptive quadrants and regions are essential in clinical practice

Each area represents certain visceral structures

Allow correlation of pain and referred pain from these areas to specific organs. Regions and quadrants are palpated, percussed, and auscultated during clinical examination

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Contents of the Abdominal Quadrants

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