Thoracic Wall and Apertures Anatomy

Thoracic Wall

• The thoracic wall is lined internally by endothoracic fascia.
• It contains superficial thoracic muscles.
• The thoracic wall extends between the superior and inferior thoracic apertures.
• The thoracic wall is covered externally by the skin and muscles attaching the shoulder girdle to the trunk.
• The thoracic wall is bounded:
  • Posteriorly - Thoracic part of the vertebral column
  • Anteriorly - Sternum and costal cartilages
  • Laterally - Ribs and intercostal spaces
  • Superiorly - Suprapleural membrane
  • Inferiorly - Diaphragm

Superior Thoracic Aperture

• Bounded by:
  • 1st Thoracic vertebra (posteriorly)
  • 1st rib (laterally)
  • Manubrium of sternum (anteriorly)

Inferior Thoracic Aperture

• Bounded by:
  • 12th thoracic vertebra (posteriorly)
  • 11th and 12th pairs of ribs (laterally)
  • Costal cartilages of ribs 7-10 and xiphisternal joint (anteriorly)

Thoracic Cage

• Not ossified until around age 40

Intercostal Space

• The intercostal space lies between two adjacent ribs.

Intercostal Muscles

• The intercostal muscles are divided into three layers:
  • External intercostal muscles
  • Internal intercostal muscles
  • Innermost intercostal muscles

Arterial Supply to Thoracic Wall

• The thoracic wall is supplied by the intercostal arteries.
• The intercostal arteries arise from the aorta.

Venous Drainage of Thoracic Wall

• The thoracic wall is drained by the intercostal veins.
• The intercostal veins drain into the azygos/hemiazygous veins or the internal thoracic veins.

Azygos System of Veins

• The azygos system of veins drains the thoracic wall.
• The azygos veins drain into the superior vena cava (SVC).
• The hemiazygos veins drain into the azygos vein.

Intercostal Nerves

• The intercostal nerves are the anterior rami of the first 11 thoracic nerves.
• The first 6 intercostal nerves are distributed within their intercostal spaces.
• The 7th- 9th intercostal nerves leave the anterior end of their intercostal space by passing deep to the costal cartilage to enter the anterior abdominal wall.
• The 10th and 11th intercostal nerves pass directly into the abdominal wall.
• The 12th intercostal nerve runs in the abdomen and runs forward in the abdominal wall as the subcostal nerve.

Atypical Intercostal Nerves

• The 1st intercostal nerve divides into a large superior and a small inferior part.
  • The superior part joins the brachial plexus.
  • The inferior part becomes the 1st intercostal nerve and there is no anterior cutaneous branch.
• The 2nd intercostal nerve supplies the skin of the axilla and the upper medial side of the arm.

Lymphatic Drainage of the Thoracic Wall

• The thoracic wall is drained by the lymphatic system.
• The lymph vessels drain into the following lymph nodes:
  • Axillary lymph nodes
  • Parasternal lymph nodes (to the thoracic duct (left) and bronchomediastinal trunk (right))
  • Intercostal lymph nodes (to the thoracic duct).
• The thoracic duct drains the lower limbs, pelvic cavity, abdominal cavity, left side of the thorax, head and neck, and arm.
• The right lymphatic duct only drains lymph from the right arm, thorax, head, and neck.

The Thoracic Cavity

• The thoracic cavity is the space enclosed by the thoracic wall.
• It contains the heart, lungs, and associated structures.
• The mediastinum is the central compartment of the thoracic cavity.
• The lungs are located on either side of the mediastinum.

The Pleura and Lungs

• The pleura is a double-layered membrane that surrounds the lungs.
  • Visceral pleura covers the lungs.
  • Parietal pleura lines the thoracic cavity.
• The lungs have differences at their hilum:
  • The right lung has three lobes: superior, middle, and inferior.
  • The left lung has two lobes: superior and inferior.
• The hilum is the region where the bronchus, blood vessels, and nerves enter and exit each lung.

The Heart

• The heart is a four-chambered organ that pumps blood throughout the body.
• The heart is located in the mediastinum.
• The heart is covered by a double-layered membrane called the pericardium.

The Diaphragm

• The diaphragm is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity.
• The diaphragm is the primary muscle of inspiration.
• The diaphragm has three parts: sternal, costal, and vertebral.
• The diaphragm has three openings:
  • Caval foramen
  • Esophageal hiatus
  • Aortic hiatus
• The diaphragm is innervated by the phrenic nerve.
• The diaphragm is responsible for creating pressure differentials within the thoracic cavity that allow for breathing.

### The Respiratory System

• Respiratory system allows for the intake of Oxygen and the exhalation of Carbon Dioxide.
• The respiratory system includes the:
  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs
• Breathing muscles:
  • Diaphragm
  • External Intercostal Muscles
• Respiration is the process of gas exchange between the body and the external environment.

### The Circulatory System

• The circulatory system is responsible for transporting blood throughout the body.
• The circulatory system includes the:
  • Heart
  • Blood vessels:
    • Arteries
    • Veins
    • Capillaries
• The heart pumps blood through the body.
• Arteries carry oxygenated blood away from the heart.
• Veins carry deoxygenated blood back to the heart.
• Capillaries exchange gases and nutrients with tissues.

Explore the anatomy of the thoracic wall and its apertures in this quiz. Understand the boundaries, muscles, and structural components that define the thoracic cage. Perfect for students studying human anatomy and physiology.