Lecture 30: Respiration 1 Flashcards
Two stages of respiration
- External respiration
2. Internal respiration
External respiration
The entire sequence of events involved in the exchange of O2 and CO2 between the external environment and the cells of the body
Internal respiration
Intracellular metabolic processes carried out within the mitochondria which use O2 and produce CO2 during the derivation of energy from nutrient molecules
Two zones of the respiratory system
- Conducting zone - brings air in and out of lungs
2. Respiratory zone - Lined with alveoli where gas exchange occurs
what is the main airway of the conducting zone?
trachea
Trachea and larger bronchiole structure
rigid non-muscular tubes enriched by a series of cartilaginous rings that prevent compression of the tubes
Do the smaller bronchioles in the conducting zone have cartilage?
Nope
What kind of muscle and innervation does the conducting zone have?
Smooth muscle
Sympathetic and parasympathetic innervations
Sympathetic adrenergic neurons in the conducting zone
Activate B-adrenergic receptors in bronchial smooth muscle which creates relaxation and dilation of the airways
Parasympathetic cholinergic neurons in the conducting zone
Activate muscarinic receptors which creates contraction and constriction of the airways
How does the ANS influence resistance and airflow?
Changes in diameter in the conducting airways leads to changes in their resistance
What are B adrenergic agonists like epinephrine used for
To dilate airways in the treatment of asthma
4 parts of the respiratory zone
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs
- Alveoli
Respiratory bronchioles
- Alveoli occasionally bud off their walls
- Contains smooth muscle
- Have limited ability for gas exchanges
Alveolar ducts
Respiratory bronchioles branch into many alveolar ducts which lead into microscopic air sacs called alveoli, where gas exchange takes place
Alveolar sacs
A group of two or more alveoli with a common opening into an alveolar duct
Functional unit of the lung
Alveoli
Alveolar walls consists of
- a single layer of flattened Type 1 alveolar cells
- contains Type II alveolar cells which synthesize pulmonary surfactant which is necessary for the reduction of surface tension of alveoli
- Alveolar macrophages that keep alveoli free of debris
Two hormones that affect Type II alveolar cells
- Thyroid hormone - increases their number in the wall of the alveoli
- Cortisol - enhances their maturation
Lungs are housed in
Airtight thoracic cavity
Four things the thoracic cavity is composed of
- Several pairs of ribs
- Sternum
- Intercostal muscles between ribs
- Thoracic vertebrae
The only communication between thorax and atmosphere is through
respiratory airways into the alveoli
Pleural sac
Separates each lung from thoracic wall and other surrounding structures
Double wall closed sac
Intra-pleural fluid
- Secreted by pleural membranes
- Lubricates the pleural surfaces, thereby reducing friction as they slide past each other during breathing
Two types of inflammation of the pleural sac
- Dry pleurisy
2. Wet pleurisy
Dry pleurisy
- Fluid content remains unchanged by disease
- Two layers of membrane may become swollen and rub against each other during breathing
- Pain
Wet pleurisy
- Fluid increases abnormally
- Less likely to cause pain because there is usually no chaffing
- Fluid may interfere with breathing
Atmosphere exerts pressure known as
Barometric or atmospheric pressure
At sea level, atmospheric pressure is equal to
760 mmHg
Individual pressure exerted by a particular gas
Partial pressure
Air is ____ on entering respiratory passages
humidified
Partial pressure of water vapor at normal body temperature is
47 mmHg
Water vapor dilutes all other gases in inspired air, thus gas pressure in the trachea =
760 - 47 = 713 mmHg
PO2 of humidified tracheal air =
(760-47 mmHg) x 0.21 = 150 mmHg
Changes in respiratory pressure during breathing are sometimes expressed as
relative pressire
A positive or negative pressure indicates that the pressure is
relative to atmospheric pressure and is respectively, above or below atmospheric pressure
When relative pressures are used, atmospheric pressure is set at
0
Intra-alveolar pressure
- Pressure within alveoli that increases and decreases with each breath
- Always equal to barometric pressure at the end of inspiration and expiration (rest period)
Intra-pleural pressure
- Within pleural sac/cavity
- Usually less than atmospheric pressure (-4mmHg)
- Does not equilibrate because no communication between pleural cavity and atmosphere or the lungs
Transpulmonary pressure
- Pressure gradient that holds the lung open
- Period of rest between breathing cycles when no air is moving into or out of the lungs
If intrapleural pressure were ever to equilibrate with atmospheric pressure
the transmural pressure would be abolished, meaning the lungs and thorax would assume their own inherent dimensions
Pneumothorax
Air in chest
Atelectasis
The lungs collapse to their unstretched size with no force present to stretch the lungs
Traumatic pneumothorax
A puncture in the chest wall that permits air from the atmosphere to flow down pressure gradient and enter the pleural cavity abolishing the transmural pressure gradient
Spontaneous pneumothorax
Hole in lung will permit air to move down pressure gradient and enter the pleural cavity from the lungs, abolishing the transmural pressure gradient
