respiratory physiology Flashcards
respiratory muscles
Diaphragm major inspiratory, dome-shaped skeletal muscle.
Other respiratory skeletal muscles active during more strenuous breathing.
quiet breathing
inspiration- active
Diaphragm contracts downwards pushing abdominal contents outwards.
External intercostals pull ribs outwards and upwards.
expiration- passive
elastic recoil
strenuous breathing, inspiration- active
inspiration- active
Greater contraction of diaphragm (1cm quiet breathing up to 10cm during strenuous breathing) and external intercostals.
Inspiratory accessory muscles active, e.g., sternocleidomastoid, alae nasi, genioglossus.
strenuous breathing, expiration-active
Abdominal muscles (rectus abdominus, internal oblique, external oblique and transversus abdominus).
Internal intercostal muscles oppose external intercostals by pushing ribs down and inwards.
nasal cavities, paranasal sinuses
- filter, warm, humidfy air, detect smells
pharynx
conducts air to larynx, a chamber with the digestive tract
larynx
protects opening to trachea and contains vocal chords
trachea and bronchi
- filters air, traps particles in mucus, cartilages keep airway open
lungs
responsible for air movement through volume changes during movement of ribs and diaphragm, include airways and alveoli
alveoli
acts as sites of gas exchnage between air and blood
filtering air
Upper airways to bronchioles
lined by pseudo-stratified, ciliated, columnar epithelium.
Inhaled particles stick to mucus. Mucus moved towards mouth by beating cilia.
cough reflex
Cough is protective reflex - rids airway of offending material.
Rapidly adapting pulmonary stretch receptors (RARs) are found in epithelium of respiratory tract.
RARs activated by dust, smoke, ammonia, oedema etc.
RARs afferents of vagus nerve.
cough reflex
- Stimulation of RARs by irritant.
– Afferent information sent via vagus nerve to brain.
– Brain sends information to diaphragm & external intercostals to induce strong contraction.
– air rushes into lungs.
– abdominal muscles
contract to induce expiration.
– glottis opens to
forcefully release air and
irritants.
respiratory tree
Airways branch into smaller and more numerous bronchioles until terminating in a group of alveoli.
Each division results in an increase in number, a decrease in diameter and an increase in surface area.
respiratory tree- conducting airways
Do not participate in gas exchange.
Form anatomic dead space.
Bronchi containing cartilage and nonrespiratory bronchioles.
Conducting airways 150mls in volume (30% of average breath).
respiratory tree- respiratory airways
bronchioles with alveoli where gas exchange occurs (from terminal bronchioles to alveoli).
The region is ~5mm long.
~2500ml volume.
type 1 and 2 epithelial cells
type 1- occupy 97% of surface area of alveoli. Primary site of gas exchange.
type 2- occupy 3%
surface area.
Produce pulmonary
surfactant (reduces
surface tension).
Alveolar macrophages:
removal of debris.
alveoli function
Alveoli perfectly designed for gas exchange:
- Large surface area: ~100m2
- Very thin walls (mean 0.5m)
- Good diffusion characteristics
blood circulation
Pulmonary circulation: brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart and then rest of body.
Bronchial circulation:
brings oxygenated
blood to lung
parenchyma.
Lymphatic system:defence and removal
of lymph fluid.
pulmonary circulation
Total blood volume in pulmonary circulation = 500mls (10% total).
At rest - 75mls blood in alveolar-capillary network.
Exercise – increases to 150-200mls due to recruitment of new capillaries secondary to an increase in pressure and flow.
Arteries: thin walled,
highly compliant,
larger diameter,
low resistance
(compared to
systemic circulation).
alveolar- capillary network
Gas exchange occurs through dense mesh-like network of capillaries and alveoli.
Distance between alveoli and red blood cell 1-2µm:
Type 1 alveolar epithelial cell, capillary endothelial cell and basement membrane.
Gas exchange occurs through dense mesh-like network of capillaries and alveoli.
Distance between alveoli and red blood cell 1-2µm:
Type 1 alveolar epithelial cell, capillary endothelial cell and basement membrane.
gas gradients
Gases move down their pressure gradients.
Pulmonary circuit: O2 enters blood, CO2 leaves
Systemic circuit: O2 leaves blood, CO2 enters.
gas concentration gradients
Similar volumes of CO2 and O2 move each minute.
Pressure gradient for O2 is much bigger than for CO2.
CO2 is more diffusible.
pulmonary and systemic capillary
Pulmonary Capillary
Alveolar Air Venous Blood
PO2 100 —-> 40 mmHg
PCO2 40 <—— 46mmHg
Systemic capillary
Tissues Arterial Blood
PO2 <40 <——- 100 mmHg
PCO2 >46 ——> 40 mmHg
