Lecture 10: Respiratory Structure and Function Flashcards
What is the respiratory and non-respiratory function of the lungs?
Respiratory function:
-Gas transport for metabolism
-Moves O2 from the air into pulmonary blood and clearance of CO2
Non-respiratory function:
-Lungs receive 100% of the cardiac output from the right heart
-Filter blood, chemical processing, maintenance and defences (part of the first line of defence)
-Facilitate venous return (respiratory pump) ie playing with pressure in thoracic cavity
What are the definitions for respirations, ventilation, gas exchange, and cellular respiration?
Respiration: interchanges of gases b/w the atmosphere and the cells of the body
Ventilation (breathing): transport of air to and from the lungs
Gas exchange: O2/CO2 exchange b/w the air in the lungs and cells in the body
Cellular respiration: oxidation of cellular molecules that produces CO2, water, and ATP
What is the overall gas transport process?
- Ventilation: movement of bulk airflow, delivering air to the respiratory zone where gas exchange takes place
2.Gas exchange/lung diffusion: Gas exchange b/w respiratory zone and blood- O2 moves across to blood and red blood cells; reverse process for CO2
- Circulation/Transport (blood <-> tissues): Requires adequate function of the pulmonary and systemic circulation
- Tissue diffusion: Erythrocyte/plasma <-> tissue cells = passive diffusion
- Internal respiration: metabolism using O2 and producing CO2
What are the structures of ventilation?
-Air transported through the airways from the atmosphere to the respiratory zone of the lungs
-Airway = system of tubular structure
*Nasal and oral cavities (turbulance)
*Pharynx and larynx
* Trachea
*Bronchi
*Bronchioles
-Bronchioles connect to alveoli where gas exchange takes place
What is the main function of the airways?
Main functions
-Delivering gas to the respiratory zone (alveoli)
-Conditioning of the inhaled air (air WARMED to core body temp prevents temp shock in alveoli) Gas is also HUMIDIFIED so saturated with vapour to prevent dehydration of the respiratory epithelium in alveoli, FILTRATED to prevent foreign objects and microorganisms to enter the lungs (reduces risk of infection and injury)
What is the structure of the airways?
Structure
Nasal/oral cavities
-Inner surface= mucus membrane that warms and humidifies air
-Some species = hair in nostrils acts as first filter
-Epithelium contains ciliated cells and mucus cells (goblet) that trap foreign objects move music towards the pharynx to be swallowed
Pharynx
-Connection between nasal/oral cavity and larynx
Larynx
-Connects pharynx and the trachea (glottis and epiglottis = cartilage prevents food entering the trachea)
-Contains the vocal cords
Trachea
-Flexible tube kept open by cartilage rings
-Inner surface lined with ciliated and mucus cells
-Mucus traps particles and coordinated cilia movements push back towards the pharynx
-If collapses no air moving in or out and will die
Bronchi
-Process cartilage plates to maintain the shape
-Starts with 1 tube per lung=primary bronchi
-Branches off to narrower tubes with less cartilage
Bronchioles
-Lack cartilage= depend upon lung recoil to maintain potency but has SMOOTH muscle
-Bronchi and bronchiole also posses ciliated and mucus producing epithelial cells
What happens as the airway cross-sectional area as it moves from the trachea to respiratory zone?
Cross-sectional area INCREASES DRAMATICALLY
-Geometric increase in # of small airways
-Reduces velocity of airflow to virtually ZERO
-Movement of gas in respiratory zone by DIFFUSION only
-Velocity = flow/cross section area
What function does the body have for airway clearance?
-Cilia and goblet cells work to move thin sheet of mucus from lower parts of the lungs to the throat region, spit or swallow
-Defensins: airway “lysol” destroy bacteria, first line of defence (2nd line is immune system proper) breakdown cell membrane of bacteria
What happens in the Alveoli = respiratory zone?
-Clusters around terminal bronchioles
-Formed by a single layer of epithelial cells an adult human covers 75-80m2
-Surrounded by capillary network, air serrated from body by 2 layers of cells (epithelium and endothelium): best for gas exchange
-Some epithelial cells (type 2) produce fluid = surfactant which reduces surface tension
-If small particles reach alveoli=”phagocytize” by macrophages (immune defence)
Why is the thoracic cavity important and what role does it play in respiration?
-Space w/in the thoracic cage b/w the thoracic vertebra, ribs/intercostal muscles and sternum
-Contains the diaphragm which separates the thoracic and abdominal cavity composed of a sheet of skeletal muscles and tendon
-Contains the mediastinum which divides the thoracic cage in 2 halves (from spine to sternum) connective tissue (steady) containing vessels, nerves, trachea
-Each lung fills 1 half
-Pleural membranes: wet epithelial surfaces, cover the lungs
-Intrapleural space filled with small amount of fluid=lubrication for friction free movements
How does pressure relate to ventilation?
-Follows the laws of physic: flow from high to low pressure = depends on delta P which was also the case for cardio
-Play with pressure in thoracic cavity bc can’t control atmospheric pressure
-Resistance to flow (R) due to friction of air particles with each others and with the ducts
-As for blood flow: F (flow) = delta P/R
-If R increases, delta P must increase to maintain air flow
-If delta P decreases R must decreases to maintain air flow
What are the mechanics of the ventilation pump? What is inspiration and expiration?
-Compression/expansion of the lungs by respiratory muscles = controls delta p
Inspiration = active mechanism
-Diaphragm contracts -> expands thoracic volume, creates negative P -> lung expands -> increase in alveolar volume-> neg P gradient facilitates flow down airways
Expiration= passive mechanism (at rest)
-End of inspiration- inspiratory muscles relax, allows lung to spontaneously recoil -> increase P in alveoli -> create P gradient from alveoli to atmosphere
-At rest diaphragm most important muscle
What is Boyle’s law of gases and how does it relate to inspiration and expiration?
Boyle’s law of gases: P1V1=P2V2
-If volume (V) increase=P decrease
-If V decrease = P increase
-Inspiration = P alveolar < P atmosphere = propels air through the airway until P alveolar = P atmosphere
-Expiration (muscle relax,lungs recoil): Alveolar > P atmosphere = airflow outward until equilibrium reached
What are special cases?
Horses
-End of expiration active –> beginning of inspiration passive (recoil)
Locomotion (walking/running)
-More than just the diaphragm and intercostal muscles involved
-Muscles take active part in expiration (specs up)
-Galloping: synchronized with breathing
Diving Animals
-Voluntary apnea (up to 1hr)
-String conducting airways
-When under water, compressed gas pushed towards the air ways (no gas exchange) = prevents entry of gas in the blood
-Don’t usually dive with full lungs
What are factors that influence ventilation? First one
-Airflow concept similar to blood flow (F=delta P/R)
-Resistance in airways normally small -> delta P major factor
- Air ways resistance:
-Mostly in nasal cavity (decreases, obstruction)
-During exercise, animals mainly use mouth to reduce resistance (except horses they flare nostrils)
-Degree of turbulence: more turbulence = more resistance. parallel branches results in increased cross/section (surface area) which compensates for increased resistance
-ANS controls smooth muscle in bronchiole:
*SNS relaxes cells= increases diameter
*PSN contracts cells= reduces diameter
*Note opposite from. cardio, goal is to bring more air in during stress so SNS is alarm and wants to promote ventilation so relax
