Clinical Anatomy of the Abdominal Cavity: Peritonitis and Ascites

Clinical Anatomy of the Abdominal Cavity

Lecture 15: Abdominal Cavity Part 1 · Dr. Karyn Lumsden BSc, DC · Assistant Professor · Karyn.Lumsden@medready.org Practice Questions are posted on Canvas

Learning Objectives for Abdominal Cavity

1. Identify the boundaries of the abdominal cavity
2. Distinguish the individual muscles that form the anterior abdominal wall using muscle fiber orientation and understanding their actions
3. Understand the concept of the rectus sheath and relate this with the arcuate line
4. Understand the layers of the anterior and lateral abdominal wall
5. Differentiate parietal peritoneum from visceral peritoneum
6. Differentiate localized and referred pain of the abdomen
7. Classify intraperitoneal versus extraperitoneal organs
8. Describe the following peritoneal structures: greater and lesser omentum, mesenteries, peritoneal ligaments
9. Divide the abdomen into 4 quadrants and 9 regions and understand the relationship with underlying abdominal viscera
10. Identify the abdominal viscera in situ and their relationship to the alimentary system: gastrointestinal tract, esophagus, stomach
11. Identify the abdominal viscera on CT imaging
12. Describe the following clinical correlations: ascites, achalasia, GERD, pyloric stenosis and hiatal hernia

Boundaries of the Abdomen

Superior Abdominal Boundaries

• Abdominal surface of diaphragm
• Interior thoracic aperture:
  • Xiphoid
  • Costal margin
  • 11th and 12th ribs
  • T12 vertebra

Inferior Abdominal Boundaries

• Pelvic inlet:
  • Pubic symphysis
  • Sacral alae
  • Sacral promontory Diaphragma

Abdominal wall muscles Pelvic floor muscles

Anterolateral Abdominal Boundaries

• Anterior abdominal wall muscles:
  • Rectus abdominis
  • External oblique
  • Internal oblique
  • Transversus abdominis

Posterior Abdominal Boundaries

• Lumbar vertebrae
• Posterior abdominal wall muscles

Muscles of the Abdominal Wall

• Function as a group:
• Provide support for viscera
• Can act as accessory muscles of respiration
• Aid in expulsive efforts
• Bilateral: flexion of the trunk
• Unilateral: lateral flexion and rotation of the trunk (a) Flexion/Extension (b) Lateral Flexion (c) Rotation

Anterior Muscles of the Abdominal Wall

• One 'vertical' muscle:
  • Rectus abdominis
• Three 'flat' muscles:
  • External oblique
  • Internal oblique
  • Transversus abdominis
• The three flat muscles blend into flat aponeurosis (tendons) forming a protective covering which surrounds the rectus muscle
• Converge on the midline Rectus abdominis Rectus sheath Linea semilunaris Transversus abdominis Internal oblique Linea alba External oblique Pyramidalis Inguinal ligament

Anterior Abdominal Wall Muscles: External Oblique

External Oblique Action

Bilateral: flexes trunk & compresses abdominal viscera Unilateral: lateral flexion & contralateral rotation of trunk

Anterior Abdominal Wall Muscles: Internal Oblique

Internal Oblique Action

Bilateral: flexes trunk & compresses abdominal viscera Unilateral: lateral flexion & ipsilateral rotation of trunk Internal abdominal oblique A ANTERIOR LATERAL

Anterior Abdominal Wall Muscles: Transversus Abdominus

Transversus Abdominus Action

Maintains posture & compresses/supports abdominal viscera Transversus abdominis Transversus abdominis A ANTERIOR LATERAL *INSERTION for all *: Aponeurosis of rectus abdominis (Rectus sheath) Rotation Internal abdominal oblique BANTERIOR

Muscles of the Abdominal Wall: Rectus Abdominus

• ACTION:
• Flexes lumbar spine
• Keeps lumbar spine straight against gravity
• Tendinous intersections divide muscle belly up into "packets"
• Aid in biomechanical action of muscle and reinforce strength
• Protected anteriorly and posteriorly by fascia known as the rectus sheath
• L and R sides of the sheath meet in the middle via the Linea alba Rectus abdominis Rectus sheath Linea semilunaris Transversus abdominis Internal oblique Linea alba External oblique Pyramidalis Inguinal ligament

Layers of the Abdominal Wall: Camper's Fascia

Campers Fascia = fatty layer

• A thick superficial layer of adipose and areolar connective tissue
• Sits just deep to the skin of the abdomen
• More prominent in lower aspect of abdomen (inferior to umbilicus)

Layers of the Abdominal Wall: Scarpa's Fascia

Scarpa's Fascia = Deep membranous layer

• Sits between Camper's fascia and rectus sheath
• Anchored laterally to the aponeurosis of the external oblique and medially to the linea alba of the rectus sheath

Layers of the Abdominal Wall: Rectus Sheath

Rectus Sheath = protective covering over rectus abdominus

• Composed of the aponeurosis of the three flat muscles as they converge in the midline to form the median linea alba
• External oblique
• Internal oblique
• Transversus Abdominus
• * Composition to sheath changes inferior to the umbilicus Camper's fascia Skin Scarpa's fascia Rectus Sheath Skin External oblique muscle Superficial fascia- fatty layer (Camper's fascia) Internal oblique muscle Superficial fascia- membranous layer (Scarpa's fascia) Transversus abdominis muscle Transversalis fascia Parietal peritoneum Extraperitoneal fatMidline

Layers of the Abdominal Wall Above Arcuate Line

1. Skin
2. Camper's Fascia
3. Scarpa's Fascia
4. Rectus Sheath: SUPERIOR to arcuate line
   • Anterior lamina (sheet) - full aponeurosis of external oblique and ANTERIOR 1/2 of the aponeurosis of the internal oblique
   • Posterior lamina (sheet) - POSTERIOR 1/2 of the aponeuroses of the internal oblique and full aponeurosis of transversus abdominis
5. Transversalis fascia
6. Extraperitoneal fat
7. Parietal Peritoneum Rectus sheath Skin Camper's fascia EO RA RA Scarpa's fascia 10 TA Transversalis fascia Extraperitoneal fat Linea semilunaris Linea alba Parietal peritoneum POSTERIOR EO - external oblique muscle IO - internal oblique muscle TA - transversus abdominis muscle RA - rectus abdominis muscle ANTERIOR

Anterior Layers of the Abdominal Wall: Rectus Sheath and Arcuate Line

Rectus Sheath:

• A durable, resilient, fibrous compartment that contains and protects the rectus abdominis
• The composition and arrangement of muscle layers differs depending on location with respect to an area known as the Arcuate line
• Arcuate line - Located 1/2 of the distance between umbilicus and pubic symphysis
• Inferior to this point the aponeuroses of all 3 lateral abdominal muscles pass anterior to the rectus abdominis muscle
• At this level, the internal aspect of rectus abdominis muscle is in direct contact with the transversalis facia
• A thin layer of CT located between the posterior surface of the TA muscle a the extraperitoneal fat of the parietal peritoneum External oblique muscle Rectus abdominis muscle Posterior wall of rectus sheath Internal oblique muscle Tendinous intersection Arcuate line Transversalis fascia Linea alba Pyramidalis muscle

Layers of the Abdominal Wall Below Arcuate Line

1. Skin
2. Camper's Fascia
3. Scarpa's Fascia
4. Rectus Sheath: INFERIOR to arcuate line
   • Anterior lamina (sheet) - aponeuroses of all 3 abdominal muscles
   • Posterior lamina (sheet) - no layer!
   • Transversalis facia now directly meets the posterior aspect of rectus abdominis mm.
5. Transversalis fascia
6. Extraperitoneal fat
7. Parietal Peritoneum Midline EO > IO R rectus TA TF BELOW ARCUATE LINE ANTERIOR Skin Camper's fascia EO RA RA Scarpa's fascia 10 TA Transversalis fascia Extraperitoneal, fat Linea semilunaris Linea alba Parietal peritoneum POSTERIOR EO - external oblique muscle IO - internal oblique muscle TA - transversus abdominis muscle RA - rectus abdominis muscle

Layers of Anterolateral Abdominal Wall

Superficial Layers

1. Skin/Superficial fascia
2. Camper's fascia - fatty layer
3. Scarpa's fascia - membranous layer

Deep Layers

1. External oblique m.
2. Internal oblique m.
3. Transversus abdominis m.
4. Transversalis fascia
5. Extraperitoneal fat
6. Parietal layer of peritoneum

4. External Oblique M. 5. Internal Oblique M. 6. Transverus Abdominis M. 7. Fascia transversalis 8. Extraperitoneal Tissue 9. Parietal layer of peritoneum

1. Skin
2. Fatty layer of superficial fascia ( Camper's fascia)
3. Membranous layer of superficial fascia ( Scarpa's facia) Rectus abdominis Rectus sheath Linea semilunaris Transversus abdominis X Internal oblique Linea alba External oblique Pyramidalis Inguinal ligament

Polling Question 1: Abdominal Muscle Action

Which of the following is most likely being used to perform the action show in the image? A. internal and external oblique muscles on the right side B. Left side transversus abdominus with right side external obliques C. Right side external oblique muscles with left side internal obliques D. Left side rectus abdominus with right side transversus abdominus E. Right side transversus abdominus with right side external obliques

Clinical Correlations: Hernias of Abdominal Wall

Hernia: when an organ (typically loop of intestine) pushes through a weak area of the abdominal wall Many hernias are asymptomatic but som may cause complications such as strangulation / compression of intestinal loop. Common signs and Symptoms:

• Visible bulge
• Burning or aching sensation
• Pressure
• Weakness Treatment: surgical repair Epigastric - upper abdomen at midline Incisional - at site of previous surgical incision Direct inguinal - near the opening of the inguinal canal Umbilical - at the navel Femoral - occur in the femoral canal Indirect inguinal - at the opening of the inguinal canal

Clinical Correlations: Direct Inguinal Hernia

• Aka "old man hernia"
• Usually occurs when abdominal muscles becomes weak over time
• Bulge/herniation occurs medial to epigastric vessels
• Common site of weakness: Hasselbach's triangle = Weakening of transversalis fascia
• Acquired injury due to increase in intra-abdominal pressure
• Lifting something too heavy Inferior Epigastric Vessels Deep Inguinal Ring Rectus abdominus Parietal Peritoneum Extraperitoneal fascia Transverse abdominal m. Internal oblique m. External oblique aponeurosis Medial | Lateral Conjoint tendon DIRECT INGUINAL HERNIA C Lineage Superficial Inguinal Ring Intestines Intestinal wall Testes Defective inguinal canal Normal inguinal canal Inguinal hernia Spermatic cord Herniated loop of intestine Scrotum @ MAYO CLINIC

Polling Question 2: Abdominal Surgical Incision Layers

Which of the following layers is least likely to be encountered during surgical incision into the left lower quadrant of the abdomen? A. Scarpa's fascia B. Anterior laminar sheet C. Transversalis fascia D. Aponeurosis of internal oblique E. Posterior laminar sheet F. Aponeurosis of external oblique