Biomechanics of the Respiratory System Quiz

Study Notes

Biomechanics of the Respiratory System

Understanding the morphology of the joints in the rib cage, the origin and insertions of muscles, and their planes of action contributes to understanding normal function.

Rib Cage Anatomy

The costovertebral joints are the connections between the head of the rib and the vertebral body.
The costotransverse joints are the connections between the tubercle of the rib and the transverse process of the corresponding thoracic vertebrae.
These joints form the attachment points for the rib cage and the spine, allowing for proper movement of the chest during breathing and other activities.

Rib Movement

The movement of the ribs (with inspiration) can be described as a bucket handle movement, moving up and down beside a bucket.
The movement of the sternum (with inspiration) can be described as a pump handle movement.
Bucket and pump handle rib movement is caused by the anterior ends of ribs 8–10 moving upwards and outwards during inspiration.
This results in:
- (A) Increasing transverse dimension.
- (B) Increasing antero-posterior (AP) dimension.

Respiratory Control Centers

Inspiration and expiration are controlled by the respiratory control centers in the brain.
The respiratory control centers control the muscles responsible for breathing, making it an involuntary process.

Mechanisms of Breathing

There are two mechanisms for breathing: involuntary and voluntary.
Involuntary breathing is controlled by the respiratory center, and the stimulus for breathing is increased CO2.
Conditions that impact involuntary breathing include:
- Pharmacological (post-operative medication, or an overdose)
- Head injury
- Tumor
- Cerebrovascular Accident (CVA)
Voluntary breathing is controlled by cortical control, and occurs when we consciously regulate our breathing.

Muscles of Inspiration and Expiration

The principal muscles of inspiration are:
- External intercostals
- Intercostal part of the internal intercostals
- Diaphragm
The accessory muscles that can contribute to inspiration are:
- Sternocleidomastoid
- Scalenes
These accessory muscles are recruited when additional respiratory effort is required to meet the oxygen demand of the person.
The muscles of expiration are:
- Internal intercostal muscles
- Abdominal muscles (rectus abdominus, external obliques, internal obliques, and transverse abdominus)
A useful tip for remembering which intercostals contribute to inspiration and expiration is: "External intercostals inspire, internal intercostals expire".

Description

Test your knowledge of the morphology of the joints in the rib cage, the origin and insertions of muscles, and their planes of action in relation to the respiratory system. Review images A, B, and C to understand the bony anatomy of the rib cage and the costovertebral and costotransverse joints.