Lesson 2: Axial Skeleton

What is the upper portion of the trunk between the neck and the abdomen called?

Chest/Thorax

What are the most common of all radiographic procedures?

Chest radiographic examinations

The radiographic anatomy of the chest is divided into what three sections

1. Bony Thorax
2. Respiratory System Proper
3. Mediastinum

What is the bony thorax?

Part of the skeletal system that provides a protective framework for the parts of the chest involved with breathing and blood circulation.

What does the term 'thoracic viscera' refer to?

The parts of the chest, consisting of the lungs and the remaining thoracic organs contained in the mediastinum.

What is the function of the bony thorax during respiration?

It serves as an expandable, bellows-like chamber that expands during inspiration and contracts during expiration.

How is respiration created in the bony thorax?

By the synchronous work of muscles attached to the rib cage and atmospheric pressure, resulting in air moving into and out of the lungs.

What is the primary purpose of the bony thorax?

To protect important organs of the respiratory system and vital structures within the mediastinum, such as the heart and great vessels.

What structures make up the bony thorax?

The sternum (anteriorly), thoracic vertebrae (posteriorly), and the 12 pairs of ribs.

What would an AP or PA projection radiograph demonstrate regarding the thoracic spine?

It would demonstrate the thoracic spine but show the sternum minimally, if at all.

What is the sternum?

The anterior part of the bony thorax; a thin, narrow, flat bone.

What is the average length of an adult sternum?

7 inches (18 cm).

What is another name for the sternum?

Breast bone.

What type of tissue composes the sternum?

Highly vascular cancellous tissue.

What is a common medical procedure performed on the sternum?

Marrow biopsy to withdraw a sample of red bone marrow.

What is the best projection to show the entirety of the sternum?

Lateral view.

How many divisions is the sternum divided into?

Three divisions.

What is the superior portion of the sternum called?

Manubrium.

What does the term 'manubrium' mean in Latin?

Handle.

What is the length of the manubrium in adults?

2 inches (5 cm).

What separates the manubrium from the body of the sternum?

Sternal Angle (Angle of Louis).

What is the large center portion of the sternum called?

Body.

What is the length of the body of the sternum in adults?

4 inches (10 cm).

How many segments is the body of the sternum at birth?

Four separate segments.

When does the union of the body segments of the sternum typically begin?

During puberty.

At what age may the union of the body segments of the sternum be complete?

About 25 years old.

What is the smaller inferior portion of the sternum called?

Xiphoid Process.

What is the composition of the xiphoid process during infancy and youth?

Composed of cartilage.

At what age does the xiphoid process become totally ossified?

About 40 years old.

What is the typical size range of the xiphoid process?

2-5 cm.

What vertebral landmarks correspond to the xiphoid process?

T9-T10.

What is the superior portion of the bony thorax?

Clavicles

What are the clavicles commonly known as?

Collar bones

To what bone are the clavicles connected?

Scapula

Through which joint are the clavicles connected to the manubrium?

Sternoclavicular joint

Another term for shoulder blades

Scapulae

How many pairs of ribs are there in the human body?

12 pairs

What part of the body do the ribs circle?

The thorax

How are ribs numbered?

According to the thoracic vertebra to which they attach, numbered from the top down

How is thoracic vertebrae located?

located posteriorly

Which landmark of the sternum is approx. 2 inches (5cm) above ljn?

T1

Which landmark of the sternum is at the level of the jugular notch (suprasternal notch, manubrial notch, uppermost border of the manubrium)?

T2, T3

Which landmark of the sternum is at the level of the sternal angle (angle of Louis)?

T4, T5

Which landmark of the sternum is at the level of the inferior angles of the scapulae?

T7

Which landmark of the sternum is at the level of the xiphoid process?

T9, T10

Which landmark of the sternum is at the inferior costal/ribs?

L2, L3

These ribs are connected to the sternum by costocartilage (a short piece of cartilage)

RIBS 1-7 — TRUE RIBS

These ribs have costal cartilage that joins together at the costocartilage of rib 7

RIBS 8-12 — FALSE RIBS

These ribs are connected only posteriorly or through the vertebrae and do not have costocartilage, and do not connect to the sternum

RIBS 11-12— FLOATING RIBS

Where does each clavicle articulate medially?

With the manubrium of the sternum at the clavicular notch

What is the only bony connection between each shoulder girdle and the bony thorax?

The sternoclavicular articulation

What do ribs 1-7 connect to anteriorly?

The sternum, through individual sections of costocartilage.

How many pairs of facets does the sternum have for costocartilage?

Seven pairs of facets.

Where are the facets for costocartilage located on the sternum?

Laterally along the manubrium and body.

Where is the first pair of facets located?

Just below the clavicular notch.

At what level does the second costocartilage connect to the sternum?

At the level of the sternal angle.

How can you locate the anterior end of the second rib?

Locate the sternal angle first and then feel laterally along the cartilage and the bone of the rib.

How do the 3rd-7th costocartilages connect to the sternum?

They connect directly to the body of the sternum.

These ribs also possess costocatilage, but these connect to costocartilage 7, which connects to the sternum

RIBS 8-10

What are the two ends of a typical rib?

Posterior or Vertebral End and Anterior or Sternal End

What does the posterior or vertebral end of a rib articulate with?

The thoracic vertebrae

What is the head of a rib?

The part that articulates with one or two thoracic vertebral bodies

What is the tubercle of a rib?

An elevated area lateral to the neck that articulates with the transverse process of a vertebra

What is the angle of the rib?

The area of forward angulation

What does the anterior or sternal end of a rib articulate with?

The costocartilage

What is the shaft or body of a rib?

The section between the two ends

The Posterior View of the Ribs contains three Articular Facets

• the Head

• the Neck

• the Tubercle (at the vertebral end of the rib)

What is the angle of the rib?

The angle of the rib is where the shaft curves forward and downward toward the sternal end.

How much higher is the posterior or vertebral end of the rib compared to the anterior or sternal end?

The posterior or vertebral end is 3-5 inches (8-13 cm) higher than the anterior or sternal end.

What does the lower inside margin of each rib protect?

The lower inside margin of each rib protects an artery, a vein, and a nerve.

Why are rib injuries very painful?

Rib injuries are very painful and may be associated with substantial hemorrhage.

What is the costal groove?

The costal groove is the inside margin of the rib that contains blood vessels and nerves.

What are the characteristics of the first ribs?

The first ribs are short, broad, the most vertical of all the ribs, and most sharply curved.

How do the lengths of ribs 2-6 compare to each other?

Ribs 2-6 get longer.

How do the lengths of ribs 7-12 compare to each other?

Ribs 7-12 get shorter.

Which ribs are the widest?

Ribs 8-9 are the widest ribs.

What anatomical structures should be shown in a Chest PA?

The apex of the lungs, costophrenic angles, and vertebral bodies (T1-T10) should be shown.

What is the costophrenic angle?

The costophrenic angle is the lower lateral tip of the lungs.

What is the cardiophrenic angle?

The cardiophrenic angle is the lower medial tip of the lungs.

What is the common name for the vertebral column?

Spine or spinal column

What is the function of the vertebral column?

It provides a flexible supporting column for the trunk and head.

How does the vertebral column affect weight distribution?

It transmits the weight of the trunk and upper body to the lower limbs.

In which plane is the vertebral column located?

Midsagittal plane

What aspect of the body does the vertebral column form?

The posterior or dorsal aspect of the bony trunk of the body.

How many separate bones does a young child have in the vertebral column?

33 separate bones

How many separate bones does an adult have in the vertebral column?

Average of 26 separate bones

What are the four types of vertebrae?

• Cervical Vertebrae

• Thoracic Vertebrae

• Lumbar Vertebrae

• Sacrum and Coccyx

What are the cervical vertebrae?

The first seven vertebrae of the spine.

What are the thoracic vertebrae?

The next 12 vertebrae after the cervical vertebrae, each connects to a pair of ribs.

What is another term for the thoracic spine?

Dorsal spine.

What are the lumbar vertebrae?

The next five vertebrae after the thoracic vertebrae, and the largest individual vertebrae.

Why are lumbar vertebrae the strongest?

Because the load of body weight increases toward the inferior end of the column.

What are common sites of injury and pathology in the lumbar region?

Cartilaginous disks between the inferior lumbar vertebrae.

What is the sacrum?

A bone formed from multiple separate bones that fuse into one distinct bone.

How many sacral segments are present in a newborn?

5 sacral segments.

What is the coccyx?

A bone formed from 3-5 coccygeal segments that fuse together.

What follows the various curves of the spinal column?

Spinal canal

Where does the spinal canal begin?

At the base of the skull

Where does the spinal canal extend distally?

Into the sacrum

What does the spinal canal contain?

The spinal cord