Mechanism of Ventilation

Boyles law

________ states that the volume of gas is inversely proportional to pressure (when temperature is constant)

Serratus anterior

________- elevates the ribs (when the scapulae are fixed)

Sternocleidomastoid

________- elevates the sternum.

Expiration

________ is the phase of ventilation in which air is expelled from the lungs.

inferior surface

Attachments: These originate from the ________ of the lower ribs, near the angle of the rib.

Latissimus

________ dorsi- elevates the lower ribs.

COPD

People with ________ often exhale through pursed lips in an effort to maintain a high intrapulmonary pressure and prevent premature collapse of the small airways.

asthma exacerbation

In a(n) ________, the already narrowed airways (due to mucosal inflammation and smooth muscle hypertrophy) are further constricted due to increased smooth muscle tone.

internal intercostals

Actions: Share the action of the ________.

Active expiration

________ utilises the contraction of several thoracic and abdominal muscles.

Inspiration

________ is the phase of ventilation in which air enters the lungs.

receptor agonists

Beta- ________ such as salbutamol can be given to reverse the constriction.

Internal intercostal

________- depresses the ribs.

ribs

Actions: Elevates the ________, increasing the thoracic volume.

interosseous part

Actions: The ________ reduces the thoracic volume by depressing the ribcage, and the interchondral part elevates the ribs.

destruction of elastin

In emphysema, there is ________ fibres within alveoli.

superior border

Attachments: Originate at the lower border of the rib, inserting into the ________ of the rib below.

interosseous part

Actions: The ________ reduces the thoracic volume by depressing the ribcage, and the interchondral part elevates the ribs.

External intercostal muscles

________- relax to depress the ribs and sternum, reducing the anterior /posterior dimension of the thoracic cavity.

posterior surface

Attachments: From the ________ of the inferior sternum to the internal surface of costal cartilages 2- 6.

subcostal muscles

The ________ are found in the inferior portion of the thoracic wall.

inner thoracic

As the lungs are held against the ________ wall by the pleural seal, they also undergo an increase in volume.

Active inspiration

________ involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals)

relaxation of muscles

During breathing, the contraction and ________ acts to change the volume of the thoracic cavity.

phrenic nerve

Each ________ is formed in the neck within the cervical plexus and contains fibres from spinal roots C3- C5.

Chronic

In ________ Obstructive Pulmonary Disease (COPD) the airway obstruction is compounded by chronic bronchitis.

External intercostal muscles

________- elevates the ribs and sternum, extending the anterior /posterior dimension of the thoracic cavity.

inner thoracic

The space between the outer surface of the lungs and ________ wall is known as the pleural space.

Attachments

 Originate at the lower border of the rib, inserting into the superior border of the rib below

Actions

 Elevates the ribs, increasing the thoracic volume

Innervation

 Intercostal nerves (T1-T11)

Attachments

 Originates from the lateral edge of the costal groove and inserts into the superior surface of the rib below

Actions

 The interosseous part reduces the thoracic volume by depressing the ribcage, and the interchondral part elevates the ribs

Innervation

 Intercostal nerves (T1-T11)

Attachments

 Originates from the medial edge of the costal groove and inserts into the superior surface of the rib below

Actions

 The interosseous part reduces the thoracic volume by depressing the ribcage, and the interchondral part elevates the ribs

Innervation

 Intercostal nerves (T1-T11)

Attachments

 From the posterior surface of the inferior sternum to the internal surface of costal cartilages 2-6

Actions

 Weakly depress the ribs

Innervation

 Intercostal nerves (T2-T6)

Attachments

 These originate from the inferior surface of the lower ribs, near the angle of the rib

Actions

 Share the action of the internal intercostals

Innervation

 Intercostal nerves

Right crus 

Arises from L1-L3 and their intervertebral discs

Left crus 

Arises from L1-L2 and their intervertebral discs

At rest, the right dome lies slightly higher than the left

this is thought to be due to the presence of the liver

When the volume of the thoracic cavity increases 

the volume of the lungs increases and the pressure within the lungs decreases

When the volume of the thoracic cavity decreases 

the volume of the lungs decreases and the pressure within the lungs increases

Diaphragm 

flattens, extending the superior/inferior dimension of the thoracic cavity

External intercostal muscles 

elevates the ribs and sternum, extending the anterior/posterior dimension of the thoracic cavity

Diaphragm 

relaxes to return to its resting position, reducing the superior/inferior dimension of the thoracic cavity

External intercostal muscles 

relax to depress the ribs and sternum, reducing the anterior/posterior dimension of the thoracic cavity

Scalenes 

elevates the upper ribs

Sternocleidomastoid 

elevates the sternum

Pectoralis major and minor 

pulls ribs outwards

Serratus anterior 

elevates the ribs (when the scapulae are fixed)

Anterolateral abdominal wall 

increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity

Internal intercostal 

depresses the ribs

Innermost intercostal 

depresses the ribs