Respiratory System - Topic 1 Flashcards
What is the main function of the respiratory system?
to supply tissues with oxygen and dispose of carbon dioxide generated by cellular metabolism
Cellular respiration
the usage of oxygen in the metabolism of organic molecules
External respiration
exchange of oxygen and carbon dioxide between lungs and blood
Internal respiration
exchange of oxygen and carbon dioxide between bloodstream and tissues/cells
Importance of oxygen in, and carbon dioxide out
we need lots of oxygen because most of the energy generated by our tissues is the result of oxidation of food substrates
carbon dioxide is the by-product of oxidative metabolism, so getting CO2 is important to prevent an accumulation which would result in acidification of bodily fluids
What are the 7 functions of the respiratory system?
- Provide oxygen
- Eliminate CO2
- Acid-base regulation (with kidneys)
- Phonation
- Host defence
- Alterations in arterial chemical messengers, either by removal or inactivation, or by producing/ activating others
- Trap and dissolve blood clots from systemic circulation
Organization of the respiratory system
Passage of air:
Nose => pharynx => larynx => trachea => bronchi => bronchioles => alveoli
Explain the relationship between blood vessels and airways
Ventilation (air movement) must be matched to perfusion (blood flow) in order for respiration to work efficiently
- there are MANY blood vessels in lungs
What are the two alveolar cell types?
- Type I alveolar epithelial cells (96-98% of surface area of alveolus)
- thin and flat (ideal for rapid diffusion)
- basement membrane of type I cells and capillary endothelium are fused - Type II alveolar epithelial cells
- cuboidal in shape
- source of pulmonary surfactant (lowers surface tension forces)
- can divide and differentiate into type I cells
What type of cell is present in alveoli for host defense?
alveolar macrophages
Describe the membranes lining the lungs
- visceral pleura is attached to the lung
- parietal pleura is attached to the interior thoracic wall and diaphragm
- separated by thin layer of intrapleural fluid => lubricates pleural surfaces as they slide over each other during breathing
Intrapleural pressure
(Pip) less than atmospheric pressure
What is pleurisy?
inflammation of the pleura (often caused by viral infections)
Muscles used for inspiration
Normal, quiet breathing:
- diaphragm, external intercostal muscles
Exercise:
- accessory muscles recruited (scalene muscles, sternomastoids)
Muscles used for expiration
Normal, quiet breathing:
- expiration is passive (i.e., muscles of inspiration relax)
Exercise:
- accessory muscles recruited (internal intercostals, abdominal muscles)
Functions of the conducting zone
- pathway for airflow
- defends against microbes, toxic chemicals, other foreign material
- warms and moistens air
- phonation
Function of the respiratory zone
GAS EXCHANGE
What happens as inspired air moves down the airways?
- moves down airways by bulk flow
- cross-sectional area of airways increases extensively past terminal bronchioles because of branching
- forward velocity of air falls and diffusion takes over as mechanism of air movement
What is the anatomic dead space?
30% of a normal breath (about 150mL) remains in the conducting zone, no gas exchange occurs
Host defence
Clearance of inhaled particles is a function of their size, which determines how far into the lungs they can penetrate (i.e., smaller particles move further down)
Mucociliary clearance (host defence)
- goblet cells and mucous glands create two layers of mucous (gel layer and sol layer)
- dust particles stick to the mucous
- cilia in the sol layer beat in one direction to push the particles out of the respiratory system
Metabolic functions of the respiratory system (and special case)
- endothelial cells lining pulmonary circulation are exposed to entire cardiac output, so they provide a good place to modify biologically active substances
- most things are unaffected or inactive, but angiotensin I is converted to angiotensin II by ACE (its the only example of biological activation)
Overview of respiration (end of topic 1)
- ventilation: exchange of air between atmosphere and alveoli by bulk flow
- exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion
- transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow
- exchange of O2 and CO2 between blood in tissue capillaries and cells in tissues by diffusion
- cellular utilization of O2 and production of CO2
