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- description "Midterm 3"
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- the process of obaining O2 from the environment and eliminating CO2 from the body.
What are the 4 steps of breathing?
- Breathing- physical exchange of gas btwn the environment and the alveoli.
- Alveolar gas exchange- exchange of O2 and CO2 btwn gas in the alveoli and blood in the pulmonary capillaries.
- Gas transport- the transport of O2 and CO2 by the blood from the lungs to the tissues of the body.
- Blood gas exchange- the exchange of O2 and CO2 btwn the blood and the tissues.
What are the steps of External Respiration?
- Ventilation or gas exchange btwn the atmosphere and air sacs (alveoli) in the lungs.
- Exchange of O2 and CO2 btwn air in the alveoli and the blood.
- Transport of O2 and CO2 btwn the lungs and the tissues.
- Exchange of O2 and CO2 btwn the blood and the tissues.
What is Internal (Cellular) Respiration?
- Intracellular metabolic processes that take place w/in mitochondria.
- Where the following reaction takes place:
- Food + O2 -> CO2 + H2O + ATP
What is External Respiration?
Exchange of O and CO btwn the environment and the cells of the body.
The Anatomy of the Respiratory System.
(the system responsible for the first two stages of external respiration)
- nasal passages- nose
- pharynx- common passageway for the lungs and the stomach.
- larynx- voice box located at the entrance to the trachea.
- trachea- tube through which air is conducted to the lungs.
- brochi- division of the trachea into 2 main branches.
What are Alveoli?
(Anatomy from Bronchi)
- small, thin-walled sacs where gas exhcange takes place.
- -tiny, air-filled chambers (~300um in diameter) w/in the lungs that serve as the site for the exchange of O2 and CO2 w/the blood.
- Attached to brachioles: small branches of the respiratory airway.
Microscopic Anatomy of an Alveolus
- Type I cell: form the walls of the alveoli.
- Type II cells: secrete a pulmonary surfactant that acts to reduce the surface tension of the water inside the alveoli.
- Each alveolus is in very close proximity to pulmonary capillaries.
The Lungs are...
- a pair of organs consisting of the lower portion of the respiratory airways, the pulmonary circulation, and connective tissue.
- Pleural Sacs- a pair of thin, fluid-filled, membranes that enclose the lungs. the space btwn the pair of membranes is referred to as the pleural cavity.
a gradient in pressure btwn the alveoli and the atmosphere provides the force to move air into and out of the lungs.
Pressures important in ventilation...
- Atmospheric pressure- pressure exerted by the weight of the gas in the atmosphere on objects on Earth's surface (760 mm Hg at sea level)
- Intra-alveolar pressure- the pressure w/in the alveoli (760 mm Hg when equilibrated with atmospheric pressure)
- Intrapleural pressure- pressure w/in the pleural sac (the pressure exerted outside the lungs w/in the thoracic cavity 4mm Hg less than atmospheric pressure - 756 mm Hg)
- Intra-pleural fluid cohesion- the force acting to attract two surfaces when they are separated by a layer of fluid.
- Transmural pressure gradients
Transmural pressure gradients are...
- differences in pressure btwn the intra-pleural space and the intra-alveolar and atmospheric spaces.
- helps ensure that the lungs maintain close proximity to the thoracic wall.
- An extremely dangerous condition that occurs when air is allowed to enter the plural cavity (either by a puncture wound in chest, or a hole in lung).
- -As a result, the transmural pressure gradient is lost and the lungs and thorax separate and assume their own inherent dimensions (lungs collapse and thoracic wall expands).
- At any constant temperature, the pressure exerted by a gas varies inversely with the volume of the gas.
- decreased gas volume -> increased pressure exerted by gas
- increased gas volume -> decreased pressure exerted by gas
Changes in lung volume and intra-alveolar pressure during inspiration and expiration.
- Before inspiration- system is equilibrated; no net movement of air.
- During inspiration- size of teh lungs increases as they are stretched to fill the expanded thorax.
- as the lungs increase in volume, intra-alveolar pressure decreases creating a pressure gradient that favors the flow of air into the alveoli.
- During expiration- as the lungs recoil to their pre-inpiratory size, intra-alveolar pressure increases, establishing a pressure gradient that favors the flow of air out of the alveoli into the atmosphere.
Intra-alveolar & intrapleural pressures during respiration...
- Throughout the respiratory cycle, intra-pleural pressure is always less than intra-alveolar pressure. Thus, a transmural pressure gradient always exists that serves to stretch the lungs to fill the available thoracic space.
- When intra-alveolar pressure is less than atmospheric pressure, air enters the lungs. When intra-alveolar pressure is greater than atmospheric pressure, air exits the lungs.
- Accessory muscles of inspiration- contract only during forceful inspiration.
- Major muscles of inspiration- contract every inspiration; relaxation causes passive expiration.
- Muscles of active expiration- contract only during active expiration.
- Diaphragm- contracts increasing the vertical dimensions of the thoracic cavity.
- External intercostal muscles- contract elevating the rib cage and increasing the thoracic cavity form side-to-side and front-to-back.
- (a) Elevation of ribs causes sternum to move upward and outward, which increases front-to-back dimension of thoracic cavity.
- (b) Lowering of diaphragm on contraction increases vertical dimension of thoracic cavity.
- (c) Contraction of external intercostal muscles causes elevation of ribs, which increases side-to-side dimension of thoracic cavity.
- Passive expiration- the ribs, sternum, and diaphragm return to resting position upon relaxation of the inspiratory muscles.
- Active expiration- contraction of abdominal muscles causes the diaphragm to be pushed upward, further reducing the vertical dimension of thoracic cavity.
- Also, contraction of internal intercostal muscles flattens the ribs and sternum further reducing the size of the thoracic cavity.
- (a) Contraction of internal intercostal muscles flattens ribs and sternum, further reducing side-to-side and front-to-back dimensions of thoracic cavity.
- (b) Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles restores thoracic cavity to preinspiratory size.
- (c) Contraction of abdominal muscles causes diaphragm to be pushed upward, further reducing vertical dimension of thoracic cavity.
- influences airflow
- F= ΔP/Rwhere...
- F= airflow rate
- ΔP= difference btwn atmospheric and intra-alveolar pressure.
- R= resistance of the airways, determined by their radius.
- A decrease in the radius of bronchioles.
- ↑ resistance due to a ↓ in radius
- caused by:contraction of airway smooth muscle
- - ↑ parasympathetic nervous stimulation
- - ↓ CO2 concentrations
- physical factors such as mucous, edema, airway collapse
- An increase in bronchiolar radius.
- ↓ resistance due to ↑ radius
- caused by:relaxation of airway smooth muscle
- - ↑sympathetic nervous stimulation
- - hormonal control: epinephrine
- - ↑ CO2 concentrations
Chronic Obstructive Pulmonary Disease (COPD) is...
What are the the 3?
- a group of lung diseases characterized by increased airway resistance resulting from narrowing of the lumen of the lower airways. (pathalogical increase in airway resistance)
- 1) Chronic Bronchitis: long-term inflammatory responses to irritants, pathogens or allergens lead to thickening and edema of the airway walls and overproduction of thick mucus.
- 2) Asthma: long-term inflammatory responses to irritants, pathogens or allergens lead to thickening and edema of the airway walls, overproduction of thick mucous, and hyper-resonsiveness of airway smooth muscle.
- 3) Emphysema: macrophage enzynes released in response to irritants cause collapse of airways and breakdown of alveolar walls. Many alveoli can burst and then enlarge.
Elastic recoil is the...
- force that restores the lungs to their preinspiratory volume after the inspiratory muscles relax at the end of inspiration.
- Due to:elastic properties of pulmonary tissue- elastin fibers are arranged in a meshwork that provides the tissue with a high degree of elasticity.
- alveolar surface tension- force due to the attraction of water molecules to each other; opposes expansion of the alveoli.
- Alveolar surface tension is reduced by a pulmonary surfactant (mixture of lipids and proteins) synthesized by type II alveolar cells.
plays a major role in preventing the collapse of small alveoli.