Lecture 18: Respiratory 1-structure, Function, Ventillation Flashcards
Be able to label the diagram on slide 7
Yep
What’s the difference between internal and external respiration?
Internal respiration:
- cellular respiration
- intracellular process: O2 is used by mitochondria to generate ATP through oxidative phosphorylation.
- CO2 and H2O produced as waste products
External respiration: involves 4 processes
- Pulmonary ventilation
- Gas exchange (lungs)
- Transportation of O2 and CO2
- Gas exchange
What are the functions of the upper respiratory tract?
- conducts air to and from lower respiratory tract
- warms and moistens air
- nasal cavities also filter and clean the air (nasal hairs, mucus and cilia)
- larynx also
- prevents airway collapse (cartilage)
- prevents food entering LRT (epiglottis)
- cough reflex
- initiated voice production
Divisions of the upper and lower respiratory tracts.
Ie what structures are contained in each?
Upper: -oral cavity, nasal cavity -pharynx -larynx (Conducting zone)
Lower respiratory tract:
- trachea
- bronchi
- bronchioles
- alveoli (respiratory zone)
Conducting zone:
What’s is responsible for?
- conducts air to and from the respiratory zone
- warms, humidifies and cleans air (contains goblet cells, secret mucus) and cilia
- NO GAS EXCHANGE
Trachea (LRT, conducting zone)
Functions
Keeps airways open during inspiration
-cartilage rings prevent airway collapse when lungs at low pressure during inspiration
Cleans air via mucus escalator
-cilia beats mucus and foreign particles towards pharynx for swallowing
Initiates cough reflex in response to irritants
Smoking paralyses the cilia so smokers must cough to remove mucus
Bronchi (LRT, conducting zone)
Functions:
- distribute air into and though out lungs
- keep airway open during inspiration- cartilage rings
- clean air via mucus escalator ➡mucus secreting goblet cells and cilia
- cough reflex
Bronchioles (LRT, conducting/ respiratory zones)
-bronchioles transit between conducting and respiratory zones
-small tubes of small muscle
-contain no cartilage
Function?
- Distribute air through lungs
- clean air via mucus escalator (goblet cells and cilia)
- can adjust airflow (diameter can change; regulated by ANS)
- respiratory bronchioles are involved in gas exchange
LRT: respiratory zone
What it do?
Site of gas exchange
- includes respiratory bronchioles and alveoli
- gas exchange maximised by:
- large surface area
- thin walls
- no cartilage
- no goblet cells (no mucus)
- sparse/ absent cilia
Alveoli (LRT, Respiratory zone)
Structure and function?
-tiny, sac-like structures
-arranged in clusters (alveolar sacs) located at the end of alveolar ducts
-functions is gas exchange
2 types of alveolar cells
Type 1:
Epithelial cells that form single layer structure over alveolus
Type 2 alveolar cells:
-synthesis surfactant
Respiratory membrane:
Separates air in alveoli from blood Comprised of: -type 1 alveolar epithelial cells -basement membrane -capillary endothelial cell Membrane is VERY thing
Look at summary of airway structure and function, best tool to study
Do it
Structure of the thoracic cavity
Lungs located within the thoracic cavity, encased by the chest wall
Each lung is encased in its own pleural sac
Pleura: lining made up of epithelial cells and connective tissue
What are the functions of the intrapleural fluid?
- Provides lubrication for friction free lung movement
- Generates surface tension that:
- prevents separation of pleurae
- helps hold lungs against chest wall in a semi-inflated state at rest
What is pulmonary ventilation?
How is airflow driven?
Getting air in and out of lungs.
By pressure gradients?
Boyle’s law:
When volume decreases pressure increases.
The pressure of a gas is defined as the force that gas excerts on the walls of its container
P1V1= P2V2
What are the 4 pressures that influence gas exchange?
Atmospheric pressure (Patm) Alveolar pressure (Palv) Intrapleural pressure (Pip) Transpulmonary pressure (Ptp)
- Atmospheric pressure
- Alveolar pressure
Describe each
- Atmospheric:
-760mm - Alveolar pressure:
-pressure inside alveoli changes during breathing due to:
A) change in lung volume
B) airflow into or out of lungs
As as atmospheric pressure is quite constant, alveolar pressure determines air flow
Intrapleural pressure (Pip) Transpulmonary pressure
Intrapleural pressure:
-pressure inside pleural cavity
-varies with respiration by is always less that (Palv)
-Pip is always negative due:
-inward recoil of lungs (inherent elastic properties + surface tension in alveoli)
-outwards recoil of rib cage (compressed at rest)
Remember that each lungs and its pleural sac is separate of the other so there are independant of each other.
Transpulmonary pressure:
Is the difference between Palv and Pip
Ptp= Palv- Pip
=0 - (-4) = +4mmHg
Always is positive under normal conditions
-Ptp is the force that keeps the lungs inflated
Pathophysiology: Pneumothorax
- is lung collapse due to presence of air in the pleural space
- intrapleural pressure will become the same as atmospheric pressure
- transpulmonary pressure becomes 0mmHg
- no force to keep lungs inflated, lungs collapse
Mechanics of pulmonary ventilation
Talk through the volume changes
- Muscles change volume of thorax
- Change in intrapleural pressure and transpulmonary pressure
- Change in lung volume
- Change in alveolar pressure
- Airflow
Muscles of pulmonary ventilation:
What muscles contract to expand the chest cavity?
What muscle contract to reduce the chest cavity?
Muscles of pulmonary ventilation:
What muscles contract to expand the chest cavity?
External intercostal muscles:
-pull ribs up and out when the contract
Diaphragm:
-pulls down when it contracts, increasing the size of the thoracic cavity
What muscle contract to reduce the chest cavity?
Internal intercostals:
-pull ribs inwards
Abdominal muscles:?
-pull ribs inwards when they contract
-causes intestines and liver to push upwards on diaphragm
Mechanisms of inspiration (breathing in) cellular level
- Increased AP firing in somatic neurons controlling inspiratory muscles
- diaphragm and external intercostals contract
- chest wall expands (diaphragm moves down, ribs move up and out)
- intrapleural pressure decrease, increasing transpulmonary pressure
- lung volume increases (suction created pulls lungs outwards)
- alveolar pressure decreases (due to increases lung volume)
- air flows into alveoli down pressure gradient until Palv= Patm
Expiration
Passive and active
Passive:
- occurs during quiet normal breathing
- doesn’t require energy
- involves relaxation of muscles that were contracted during inspiration
Active inspiration:
-strong fasted contraction of lungs. Important during exercise and disease
/involves internal intercostal and abdominal muscles contracting.
