Thorax and Thoracic Cage

Thorax

• The thorax is the part of the body between the neck and abdomen, containing the respiratory and cardiovascular systems.

• The thoracic cavity is divided into three compartments: the central mediastinum, and the right and left pleural cavities.

Thoracic Cage

• The thoracic cage provides rigidity and protects internal organs.

• It also supports the upper limbs, provides attachment points for muscles of the upper limbs, abdomen, neck, back, and respiration.

Ribs

• Ribs are curved, flat bones that form most of the thoracic cage.

• There are three types of ribs:

  • True (vertebrosternal) ribs (1st–7th ribs): attach directly to the sternum through their own costal cartilages.
  • False (vertebrochondral) ribs (8th, 9th, and usually 10th ribs): connect indirectly to the sternum through the cartilage of the rib above.
  • Floating (vertebral, free) ribs (11th, 12th, and sometimes 10th ribs): cartilages do not connect to the sternum.

Costal Cartilages

• Increase in length through the first 7 ribs and then gradually decrease.

• The first 7 attach directly and independently to the sternum.

• The 8th, 9th, and 10th articulate with the costal cartilages just superior to them, forming a continuous cartilaginous costal margin.

• The 11th and 12th costal cartilages form caps on the anterior ends of the corresponding ribs and do not attach to any other bone or cartilage.

Intercostal Spaces

• Separate the ribs and their costal cartilages.

• Spaces are named according to the rib forming the superior border of the space (e.g., the 4th intercostal space is between ribs 4 and 5).

• There are 11 intercostal spaces and 11 intercostal nerves.

• The space below the 12th rib is called the subcostal space.

Thoracic Vertebrae

• Composed of 12 stacked vertebrae that provide attachment points for ribs.

• The superior articular facets interlock with the inferior articular facets of the vertebra above.

• The thoracic spine allows for movement in all directions, but provides more rotation than other sections and less flexion and extension.

Thoracic Vertebrae Anatomy Continued

• Superior Articular Processes: for articulation with the inferior articular process of the vertebra above.
• Pedicle: project posteriorly allowing space for the vertebral foramen.
• Vertebral Foramen: for passage of the spinal cord.
• Lamina: attachment sites for deep back muscles.
• Inferior Articular Processes: for articulation with the superior articular process of the vertebra below.
• Intervertebral discs: made of fibrocartilage, provide cushion and shock absorption.

Superior/Inferior Costal Facets

• Occur on the bodies of typical thoracic vertebrae (T2–T9).

• Facets are arranged in pairs on adjacent vertebrae:

  • An inferior (demi)facet of the superior vertebra
  • A superior (demi)facet of the inferior vertebra.

• Together, they form a single socket for the head of the rib of the same number as the inferior vertebra (e.g., head of rib 6 articulates with the superior costal facet of vertebra T6).

Atypical Thoracic Vertebrae

• T1: has a typical inferior costal (demi)facet and articulates with rib 1.
• T10, T11, and T12: have a single pair of whole costal facets, with T10's facet located partly on the body and partly on the pedicle, while T11 and T12's facets are located on their pedicles.

Spinous Processes

• Projecting from the vertebral arches of typical thoracic vertebrae.
• Long and slope inferiorly.
• Usually overlap the vertebra below.
• They cover the intervals between the laminae of adjacent vertebrae, protecting the spinal canal.

The Sternum (AKA: Breastbone)

• A flat, elongated bone that forms the middle of the anterior part of the thoracic cage.
• Provides protection for mediastinal viscera (mostly the heart).
• Consists of three parts:
  • Manubrium
  • Body
  • Xiphoid process.

Thorax

• The thorax is the area between the neck and abdomen.
• Contains the primary organs of the respiratory and cardiovascular systems.
• Divided into three compartments:
  • The central mediastinum: contains the heart and structures for air, blood, and food transport.
  • Right and left pleural cavities: contain the lungs
  • The lungs are the main organs of the respiratory system.

Thoracic Cage

• Provides rigidity and protection for internal organs.
• Resists pressure generated from lung recoil and breathing.
• Provides attachment points for upper limbs.
• Provides attachments for muscles in the abdomen, neck, back, and respiration.

Ribs

• Curved, flat bones forming most of the thoracic cage.
• Light in weight yet resilient.
• Contains bone marrow which produces blood cells.

Types of Ribs

• True (vertebrosternal) ribs: Ribs 1-7, attach directly to the sternum through their costal cartilages.
• False (vertebrochondral) ribs: Ribs 8-10, connect indirectly to the sternum through their cartilages attaching to the rib above.
• Floating (vertebral, free) ribs: Ribs 11-12, their cartilages don't connect directly or indirectly to the sternum, ending in the posterior abdominal musculature.

Costal Cartilages

• Contribute to the elasticity of the thoracic wall.
• Length increases till the 7th rib then gradually decreases.
• The first 7 costal cartilages attach directly to the sternum.
• Ribs 8-10 attach indirectly to ribs above forming the costal margin.
• Ribs 11-12 form caps on the anterior ends of the ribs without attaching to other bone.

Intercostal Spaces

• Separate ribs and costal cartilages.
• Named after the rib that forms the superior border.
• Contain muscles, membranes, and blood vessels.
• Space below the 12th rib is subcostal space.

Thoracic Vertebrae

• 12 stacked vertebrae that provide attachment points for ribs.
• Superior articular facets interlock with inferior facets of the vertebra above.

Thoracic Vertebrae Anatomy

• Superior Articular Processes: For articulation with the inferior articular process of the vertebra above.
• Pedicle: Project posteriorly allowing space for the vertebral foramen.
• Vertebral Foramen: Passage for the spinal cord.
• Lamina: Attachment sites for deep back muscles.
• Inferior Articular Processes: For articulation with the superior articular process of the vertebra below.
• Intervertebral Discs: Made of fibrocartilage, provide cushioning and shock absorption between vertebrae.

Superior/Inferior Costal Facets

• Present on typical thoracic vertebrae (T2-T9).
• Arranged in pairs, one on each adjacent vertebra, for articulation with ribs:
  • Inferior facet of the superior vertebra.
  • Superior facet of the inferior vertebra.
• Form a socket to receive the head of the corresponding rib (e.g., rib 6 with T6).

Atypical Thoracic Vertebrae

• T1: Has a whole costal facet on its body, articulating with rib 1 only.
• T10: Has a whole bilateral facet, partly on its body and pedicle, for rib 10.
• T11 and T12: Have a whole bilateral facet on their pedicles, for ribs 11 and 12 respectively.

Spinous Processes

• Project from the vertebral arches of typical thoracic vertebrae.
• Long and slope inferiorly.
• Overlap the vertebra below.
• Provide protection for the spinal canal.

The Sternum

• Flat, elongated bone forming the middle of the anterior thoracic cage.
• Protects mediastinal viscera (mainly the heart).
• Composed of three parts:
  • Manubrium
  • Body
  • Xiphoid process

Explore the anatomy of the thorax, including the thoracic cavity, thoracic cage, and rib types. This quiz covers the essential functions and structures of this vital area of the human body. Test your knowledge on the respiratory and cardiovascular systems within the thorax.