The Respiratory System Flashcards
Nasal cavity
- breathing through nose is preferred (protective mechanism of lungs)
- nasal cavity lined with hairs to aid in removal of course particles, releases mucous to trap small particles and watery excretions which contain lysosomes to attack and destroy particles
- smaller hairs line inner nasal cavity which assist in moving mucous down to pharynx to be swallowed and destroyed by stomach acid.
- watery excretions humidify incoming air to make it suitable for passing through airways
- nasal conchi is a membrane which protects the nasal cavity.
- slow movements of air create turbulent flow allowing humidifying to occur more quickly
Larynx & pharynx
Larynx- deciphers between food and water
Pharynx- filters air that we breath
Trachea
- 10-12cm diameter 2cm
- tube made up of smooth
Muscle. - cartilaginous rings every cm allows airways to be open at all time
- horseshoe structure to prevent food from being stuck
- internal lining- pseudo stratified (single layer), epithelial (surface of body), columnar, goblet cells (mucous production)
- mucous lines wall of trachea
- cilia move pathogens up and swallow again to reach stomach to be destroyed
Cells of alveoli
- simple squamous epithelium (type 1) - wall of alveoli. These are unusually thin to optimise gas exchange.
- macrophages - remove debris and microbes from inner surface of alveoli to protect from inflammation which would prevent efficient gas exchange
- surfactant secreting cells (type 2 cells) produce surfactant which is a watery substance. This lowers the surface tension on the alveolar surface which is produced by the cohesive nature of water, thus it acts as a detergent by interacting with water molecules Tor deuce cohesiveness to allow efficient inflation and deflation of alveoli.
Ventilation perfusion
Perfusion is adjusted to changes in ventilation.
Eg. Decreased blood flow, reduced PO2 in blood vessels, vasoconstriction of pulmonary vessels, decreased blood flow, blood flow matches airflow
Inspiration
ACTIVE PROCESS
- diaphragm and external intercostal muscles contract
- external intercostal muscles elevate the rib cage; the sternum moves anteriorly
- diaphragm flattens and moves inferiorly
- thoracic cavity volume increase
- intrapulmonary pressure drops to -1mmHG
- air flows into lungs down its pressure gradient until intrapulmonary pressure is 0
Expiration
PASSIVE PROCESS
- Inspiratory muscles relax (diaphragm rises; rib cage defends due to recoil of costal cartilages)
- thoracic cavity volume decreases
- elastic lungs recoil passively; intrapulmonary volume decreases
- intrapulmonary pressure rises to +1 mmHG
- air flows out of lungs down its pressure gradient until intrapulmonary pressure is 0
Thoracic cavity
Lined with serous membrane, allowing lung to attach to it, so they can move simultaneously.
Visceral membrane- attached to lung
Parietal membrane- attached to thoracic wall
Intrapleural fluid found between the lungs and thoracic wall to prevent lungs from collapsing.
Intrapleural pressure is negative within pleural cavity due to surface tension of alveolar fluid, elasticity of the lungs, elasticity of the thoracic wall
Forced inspiration
Greater contraction of diaphragm and external intercostal muscles, aiding muscles also help to lift rib cage upwards
Heavy expiration
Active process
Abdominal muscles squeeze listing the diaphragm and reducing thoracic volume. Internal intercostals push on thoracic wall
Respiratory volumes
Tidal volume- 500ml- amount of air inhaled or exhaled with each breath under resting conditions
Inspiratory reserve volume- 3300ml amount of air that can be forcefully inhaled after tidal volume
Excitatory reserve volume- 1000ml - amount of air that can be forcefully exhales after tidal volume
Respiratory capacity
Total lung capacity - 6000ml- max amount of air contained in the lungs at full capacity
Vital capacity- 4800ml - maximum amount of air that can be inspired or expired
Alveolar and tissue respiration
Tissues- O2 from systemic capillaries into cells, CO2 from cells into systemic capillaries
Alveoli- O2 from alveoli into pulmonary capillaries, CO2 from pulmonary capillaries into alveoli
Influenced by surface area, partial pressure gradient and rate of blood flow
Ficks equation
Mass/time (diffusion) = K (Kroghs diffusion constant) X area (surface area of respiratory membrane) X change in concentration gradient // thickness of respiratory membrane
Anything which increases alveolar thickness will reduce diffusion
CO2 More soluble than O2,
Impacts on capacity to diffuse from alveoli to blood - need moreO2 to account for amount of CO2
Alveolar pressures
Partial pressure of alveoli differ from those in the atmosphere due to
- humidification of inhaled air
- mixing of old and new air- first 150ml of 500 ml is dead space
- gas exchange between alveoli and pulmonary capillaries