Respiratory system Flashcards
Systems purpose:
Gas exchange, oxygen needed for cellular respiration to produce energy in the mitochondria (produces CO2)
Inhalation
diaphragm contracts pulling downward, allowing lungs to expand and draw in oxygen
Exhalation
diaphragm relaxes, lungs return to normal shape & CO2 rich air is expelled
Conducting zone
- Upper airway structures (nasal cavity, pharynx, larynx, trachea, bronchi, and most bronchioles)
- Continuous passage for air to move in & out
Nasal cavity
- Inhaled gas enters body through nasal cavity
- Contains: mucous (with lysosomes) & hair to trap inhaled particles
- 4 sinuses (air filled spaces) allow air circulation to warm & moisten air
Pharynx
- Nasopharynx (from nose)
- Oropharynx (from mouth)
- Laryngopharynx (to larynx)
Larynx
- Inhaled breath meets fork in the road (oesophagus or trachea)
- Trachea is protected by Cartlidge structure called epiglottis, acts like a toilet lid, with the help of muscle and connective tissue protect the trachea and vocal chords when we swallow
Trachea
- Windpipe
- 20 C-shaped rings of tough cartilidge, lined with smooth muscle containing nerves to the autonomic nervous system
- Can dilatate (sympathetic) or restrict (parasympathetic) based on input from the nervous system
- Splits into right (wider & more vertical than left) and left primary bronchi (lined with cells:
- Mucous secreting cells which trap particles and move them up the mucociliary escalator
- Bronchi branch off forming bronchiole tree
Physiological changes traveling down the bronchiole tree
- As it branches off cartilage decreases and disappears by bronchioles
- Epithelium also changes down the branches;
Pseudostratified -> columnar -> cuboidal - Smooth muscle gradually increases & forms a complete layer in the bronchioles which are primarily muscle and tissue
- Last part of the conducting zone terminal bronchi
Respiratory zone
- Respiratory bronchioles, alveolar ducts, alveolar sacs
- Main site of gas exchange
Alveolar walls
- no cilia, smooth muscle, cartlidge, primarily pneumocytes
- Type I cells and type II cells
- Alveoli macrophages clear any remaining pathogens before air enters bloodstream
- Alveoli and capillary walls & their fused basement membranes
- Gas exchange occurs
Type I cells
- Simple squamous epithelium
- gas exchange
Type II cells
- Scattered cuboidal epithelium
- secrete surfactant (lowers surface tension preventing collapse) & antimicrobial proteins
Inhalation pathway
Inhaled air passes through –> nasal cavity –> pharynx –> larynx –> trachea –> primary bronchus
–> bronchioles –> respiratory bronchioles –> respiratory bronchioles –> alveoli –> respiratory membrane –> capillaries
Exhalation pathway
Inhaled air passes through
Process of respiration (respiratory system)
- Pulmonary ventilation (breathing) - movement of air in and out
- External respiration, O2 & CO2 exchange between blood and lungs
Process of respiration (cardiovascular system)
- Transport O2 and CO2 in blood
- Internal respiration, CO2 & O2 exchange between systemic blood vessels and tissues
Boyles law
- Pressure is inversely proportional to volume
- Pressure or volume changing impacts the other
- Decreased volume = increases pressure and other way around
Ventilation
- Cyclic movement
- Gas into and out of lungs caused by change in volume facilitated by skeletal muscle contraction
- Leads to change in pressure causing flow of gasses
- In inhalation the lungs expand due to diaphragm contraction decreasing pressure in the lungs making air flow in
- Opposite in exhalation
- Air flows in and out dependant on concentration gradient creating a ventilation cycle
At rest –> inhalation –> exhalation –> repeat
Muscles involved
Diaphragm, external intercostals, internal intercostals & some abdominals
Gas exchange (in alveoli and capillary)
- Uses concentration gradient until equilibrium
- CO2 out O2 in
- The body manipulates these principles to achieve respiration
What is gas exchange affected by
- Effected by: surface area, thickness of respiratory membrane & solubility of gasses
Respiratory volume
The volume of gas in the lungs at any given time during the respiratory cycle
Lung capacity
The volume of air in the lungs on maximum effort of inspiration (average = 6L)
Tidal volume (TV)
The volume of air inspired/expired in a breath
Inspiratory reserve volume (IRV)
The volume of air that can be forcefully inspired after a normal tidal inspiration (add on air)
Expiratory reserve volume (ERV)
The volume of air that can be forcefully expired after a normal tidal expiration (add on air)
Residual volume (RV)
The volume of air remaining after a forceful expiration
Inspiratory capacity (IC)
The volume that can be inspired after a normal expiration IC = TV + IRV
Functional residual capacity (FRC)
The volume of air remaining after a normal expiration FRC = RV + ERV
Vital capacity (VC)
The volume of air that can be moved in/out in a single breath VC = TV + IRV + ERV
Total lung capacity (TLC)
Total amount of air in lungs TLC = TV + IRV + ERV + RV
Compliance
- Used to measure the ability of the lungs to expand
- If easy to inflate something then compliance is high
- If hard to inflate something then compliance is low
- Compliance = lung volume/pressure
Elasticity
- The resistance to the lungs expanding
- The reciprocal of compliance
- If compliance is low, elastic recoil is high, meaning the lungs are stiffer & there is greater tendency of lung collapse
- Elasticity = 1/compliance = pressure/lung volume
Factors influencing compliance
- Elastic recoil of lung tissue
- Elastin fibres making up the pulmonary interstitium (region between alveoli) return lung to original length after expansion
- 1/4 to 1/3 of elastic recoil
- Surface tension of the air alveolar interface
- Inner surface of alveoli are covered in fluid exerting a force inwards
- To prevent the alveoli from collapsing there in a transpulmonary pressure (reduced by surfactant)
Surfactant
- Pulmonary surfactant is 90% phospholipid & 10% protein
- Reduces surface tension at air liquid interface
- Produced by alveolar type II cells
- Reduces pressure required to keep alveoli expanded - increases compliance
- Decreases work required by respiratory muscles
