✅Muscles & Mechanics Of Respiration Flashcards
What is the larynx associated with?
- Muscles of neck and pharynx
2. Intrinsic muscles:
– Control vocal folds
– Open and close glottis
What does the Trachealis muscle do?
Controls air going in and out
What are the two pleural cavities separated by?
mediastinum
What does each pleural cavity contain?
– Holds a lung
– Is lined with a serous membrane (the pleura)
What are pleura?
Thin membranes between the lung & chest wall
What are the inner and outer pleura called?
» Visceral pleura (inner)
» Parietal pleura (outer)
Describe pleural space
» Contains a small amount of fluid
» Airtight, creating a negative pressure
When does Pneumothorax occur?
Occurs when air enters the pleural space, due to spontaneous rupture or trauma
What happens when Pneumothorax occurs?
Lung collapses while chest wall expands
What lubricates space between two layers?
Pleural Fluid
What does boyles law refine?
• Defines the relationship between gas pressure and volume
P = 1/V
What happens in a contained gas?
– External pressure forces molecules closer together
– Movement of gas molecules exerts pressure on container
What happens If you decrease the volume of the container
collisions occur more often per unit of time, increasing the pressure of the gas.
What happens If you increase the volume?
fewer collisions occur per unit of time, because it takes longer for a gas molecule to travel from one wall to another. As a result, the gas pressure inside the container decreases.
What happens in the body when breathing?
» Ribcage moves upward & outward during inspiration
» Ribcage moves downward & inward during expiration
» Inspiration creates a more –ve pressure in pleural space & lungs
» Air fills the lungs until the intrapulmonary gas pressure equals atmospheric
What happens in inspiration?
Diaphragm, functioning like a piston
What happens in expiration?
» “Elastic” recoil
» When ventilatory requirements increase (e.g. exercise), muscles of expiration are recruited.
What direction does air flow?
from area of higher pressure to area of lower pressure
What does A respiratory cycle consist of?
An inspiration (inhalation) An expiration (exhalation)
What are the components of the ventilatory pump?
chest wall, respiratory muscles, pleural space
What is the chest wall made up of?
» Muscles of respiration (mostly intercostals)
» Bones (spine, ribs and sternum)
What does the chest wall do?
It Enables outward expansion and inward recoil forces
What are the respiratory muscles made up of?
» Diaphragm (major inspiratory muscle), separates the thorax from abdomen (bottom) & from the muscular chest wall (sides)
» Expiratory muscles used in “active breathing” (major: internal intercostals & abdominal muscles)
What does pulmonary ventilation do?
Causes volume changes that create changes in pressure
The volume of the thoracic cavity changes with expansion or contraction of……. or …….
Diaphragm
Rib cage
What does the diaphragm form?
The floor of the thoracic cavity
What is the diaphragm’s shape when relaxed?
Dome shaped
What is the diaphragm made up of?
xiphoid process, internal surface of rib cage, costal cartilages of last 6 ribs and anterior surfaces of lumbar vertebra
What is inside the diaphragm?
The central tendon
What is always active?
Inhalation
What are the mechanics of breathing?
As the rib cage is elevated or the diaphragm is depressed, the volume of the thoracic cavity increases
What does Boyle’s law define?
The relationship between gas pressure and volume
What does P =
1/V
What happens in a contained gas?
– External pressure forces molecules closer together
– Movement of gas molecules exerts pressure on container
What are the four most common methods of reporting gas pressures?
Millimetres of mercury
Torr
Centimetres of water
Pounds per square inch
What is the mechanics of inhalation?
P outside > P inside
Elevation of the rib cage and contraction of the diaphragm increase the size of the thoracic cavity. Pressure within the thoracic cavity decreases, and air flows into the lungs.
What is the mechanics of exhalation?
P outside < P inside
When the rib cage returns to its original position and the diaphragm relaxes, the volume of the thoracic cavity decreases. Pressure increases, and air moves out of the lungs
What major factors does breathing depend on?
- the compliance of the lungs and chest wall
- the resistance of the airways to the smooth flow of air
Describe wall compliance
The lung is elastic: constantly pulling inward & would collapse if not held open by the chest wall. The chest wall is also elastic, put constantly being pulled outward by muscles that are always under slight tension
Describe the airway resistance
The radius of the vessels of the airway establishes the resistance to airflow (inverse square law). Diameter of bronchi & bronchioles rarely restrict flow of air in healthy persons, but in some diseases (chronic obstructive pulmonary disease) airflow is restricted.
Compliance is an indicator of what?
Expandability
Low compliance requires what?
Greater force
High compliance requires what?
Less force
What 3 factors affect compliance?
- Connective tissue structure of the lungs
- Level of surfactant production
- Mobility of the thoracic cage
Describe surfactant
• An oily secretion
• Contains phospholipids and proteins
• Coats alveolar surfaces and reduces surface tension
What is The intrapulmonary (also called intra-alveolar) pressure is relative to?
Atmospheric pressure
In relaxed breathing, the difference between atmospheric pressure and intrapulmonary pressure is what?
Small
Maximum intrapulmonary pressure: during maximum straining (dangerous activity) range can increase from what?
-30 mm Hg (inhalation) to +100 mm Hg (closed glottis)
What is intrapleural pressure?
The pressure in space between the parietal and visceral pleura
What does the intrapleural pressure remain below?
atmospheric pressure throughout respiratory cycle (due to relationship between lungs and body wall)
Describe 2 injuries to the chest wall
– Pneumothorax allows air into pleural cavity
– Atelectasis (also called a collapsed lung) as a result of pneumothorax
What does Cyclical changes in intrapleural pressure operate?
the respiratory pump, aiding venous return to the heart
What is tidal volume (Vt)?
the amount of air moved in and out of lungs in a single respiratory cycle
What are the most important respiratory muscles? (Primary respiratory muscles)
• The diaphragm
• External intercostal muscles of the ribs
• Accessory respiratory muscles – activated only when respiration increases significantly
Why is the diaphragm important in inhalation?
– Contraction draws air into lungs – 75% of normal air movement
Why are External intercostal muscles important to inhalation?
– Assist inhalation
– 25% of normal air movement
Why are accessory muscle important in inhalation?
Assist in elevating the ribs
What are the accessory muscles?
– Sternocleidomastoid
– Serratus anterior
– Pectoralis minor
– Scalene muscles
When do the accessory respiratory muscles become active?
When the depth and frequency of respiration must be increased markedly
What do the Internal intercostal +
transversus thoracis
muscles in exhalation?
Depress the ribs
What do the abdominal muscles do in exhalation?
Compress the abdomen
Forces the diaphragm upward
What are the two modes of breathing?
Quiet
Forced
Describe quiet breathing
– Involves active inhalation and passive exhalation – Diaphragmatic breathing or deep breathing
dominated by diaphragm
– Costal breathing or shallow breathing
dominated by rib cage movements
What is dyspnea?
Shortness of breath” – producing an accelerated pattern of shallow, ineffective breathing, and accompanies elevated arterial CO2 and [H+]
What is hyperventilation?
Overbreathing” so that the increase in pulmonary ventilation exceeds the oxygen needs of metabolism, it lowers the normal alveolar concentration of CO2, leading to excessive CO2 unloading
