lecture 14 - respiratory system 1 Flashcards
functions of the respiratory system?
exchange of gases
regulation of body pH
protection from inhaled pathogens and irritants
vocalisation
overview of the gas exchange system?
ventilation/external respiration
internal transport
internal respiration
what is ventilation?
exchange of air between the atmosphere and the lungs
external respiration
what is internal transport?
movement of gas from lungs to the blood circulation
what is internal respiration?
gas exchange at the cellular level
what are the right and left lungs separated by?
the heart and the mediastinum
whats the hilum?
triangular depression on the mediastinal surface of each lung where the primary bronchi, blood, sympathetic vessels and nerves enter and exit the lung
whats the cardiac notch?
groove in the mediastinal surface of of the left lung where it comes into contact with the heart
wheres the start of the respiratory system?
the nasal cavity
how many lobes are the lungs divided into?
right - 3 lobes
left - 2 lobes
what are the conducting systems?
not involved in gas exchange - main role is to move air in
comprised of:
• upper respiratory tract
• lower respiratory tract
lead from external environment to exchange surfaces
warm, humidify and filter inspired air
what is the upper respiratory tract made of?
- nasal cavity
- pharynx
- larynx
what is the lower respiratory tract made of?
- trachea
- bronchi
- bronchioles
what is the respiratory zone?
comprised of alveoli and capillary system
gas exchange surface
what does the nose and naval cavity do?
- inhaled air is warmed and humidified
- filters debris
- secretes antibacterial substances
- has olfactory receptors for smell
- enhances resonance of voice
what does the pharynx (throat) do?
- warm, humidify and filter inspired air
- soft palate component moves posteriorly during swallowing to prevent food from entering nasopharynx and nasal cavity
- protects against mechanisms stress (air and food)
what does the larynx do?
- prevents food and liquids entering the respiratory tract
* sound production
the bronchial tree
lower respiratory tract conducting system
trachea branches into 2 primary bronchi - left and right
5 secondary bronchi
18 tertiary bronchi
divide into bronchioles
terminal division into a cluster of alveoli
how does the structure of airways relate to the function
as conducting systems divide the cross sections area increases exponentially
large SA for gas exchange at alveoli
epithelial cells of the lower conducting system
- goblet cells
- ciliated cells
- mucocilary escalator
what do goblet cells do?
secrete mucus to form a continuous mucus layer over the surface of the respiratory tract
what do ciliated cells so?
produce saline
sweep mucus upwards to pharynx
what does the mucociliary escalator do?
removes noxious particles from the lungs
saline secretion essential for functioning mucociliary escalator
how is cystic fibrosis causes?
defect in CFTR (cystic fibrosis transmembrane regulator channel)
results in decreased fluid component of mucus
thick, sticky mucus layer cannot be cleared
bacteria can colonise causing recurrent lung infections
how is the trachea kept open?
C-shaped cartilage rings
what is the posterior surface of the trachea covered with?
elastic connective tissue and smooth muscle
allows oesophagus to expand during swallowing
what are the 3 main histological changes that occur as the bronchi divide?
cartilage changes to complete rings, to progressively fewer, irregular plates
epithelium gradually changes to columnar cells in smaller bronchi
amount of smooth muscle increases
structure of bronchioles
non-ciliated epithelium
smooth muscle layer
no cartilage
branch into 2 alveolar ducts
where do alveolar ducts end?
in alveolar sacs - grape like clusters of alveoli which are surrounded by elastic fibres and a network of capillaries
vasculature of the alveoli
extensive capillary network provides large SA for exchange
pulmonary artery supplies deoxygenated blood
pulmonary vein carries oxygenated blood away
structure of alveoli
single epithelial layer
supported by elastic fibres
large SA
what are the 2 types of alveoli?
type 1 alveolar cell
• 90% of alveoli
• very thin
• for gas exchange
type 2 alveolar cell
• smaller
• thicker
• produce surfactant
what do macrophages do?
protect alveolar structures from non-filtered small particles
what does ventilation involve?
diaphragm
respiratory muscles
pressure changes
what is inhalation?
active contraction of the diaphragm
what is expiration?
passive relaxation of the diaphragm
what do the repsiraoty muscles do?
external intercostal muscles and scalenes raise rib cage upwards and outwards
in quiet breathing, expiration is passive
in forced breathing, intercostal muscles are active and accessory muscles play a role
what is the mechanics of breathing?
movement of the thoracic cage and diaphragm during breathing
inspiration - increase is thoracic volume
expiration - decrease in thoracic volume
what is Boyle’s law?
describes the relationship between pressure and volume
states that as:
• volume increases, pressure decreases
• volume decreases, pressure increases
what pressure gradients influence ventilation?
atmospheric pressure
intrapulmonary pressure
intrapleural pressure
what is atmospheric pressure?
pull of gravity of air around us creates atmospheric pressure
what is intrapulmonary pressure?
air pressure in the alveoli
rises and falls with inspiration and expiration
always eventually equalises with atmospheric pressure
what is intrapleural pressure?
pressure in the pleural cavity
rises and falls with inspiration and expiration
doesn’t equalise with atmospheric pressure
what are pleural sacs?
go around each lung - not fully: gap where bronchi and blood vessels enter and leave the lung
double membraned
in-between the 2 membranes there is a pericardial cavity
what does the pericardial cavity do?
creates a tiny layer of fluid
helps keep the membranes together
what is the outer layer of the plural sac?
parietal pleura
fused to ribcage, diaphragm and other local structures
what is the inner layer of the plural sac?
visceral pleura
continuous with the surface of the lungs
what do pleural fluid do?
acts as a lubricant to allow lung to move within thorax
maintains lung inflation at rest
summary of inspiration
- contraction of inspiratory muscles
- increase thoracic volume
- decrease intrapleural pressure
- increase lung volume
- decrease alveolar pressure
- air into lungs
summary of expiration
- relaxation of inspiratory muscles
- decrease thoracic volume
- increase intrapleural pressure
- decrease lung volume
- increase alveolar pressure
- air out of lungs to functional residual capacity
summary of forced expiration
- contraction of expiratory muscles
- decrease thoracic volume
- increase intrapleural pressure
- decrease lung volume
- increase alveolar pressure
- air out of lungs below functional residual capacity
