9/23a Pulmonary Physiology I (Biomedical Sciences) Flashcards
· Describe the basic anatomy of the key components of the pulmonary system · Describe the physiological mechanisms underlying ventilation · Describe the physical factors that contribute to impairments in ventilation · Describe the defense mechanisms of the pulmonary system · Describe the physiological mechanisms involved in the exchange of oxygen and carbon dioxide between the environment and arterial blood
Functions of the pulmonary system
- Main function: gas exchange of O2 and CO2 between cells and the environment; adapt to changing demands; pulmonary processes
- Speech
- Metabolic Functions - blood reservoir
Anatomical components of gas exchange
- Pump - thoracic cavity/wall is the home of the pump. The motion and changes in volume drive ventilation
- Airways - conduction and respiratory zones
- Control System - sensors, processors, effectors
the importance of the pump
- the motion and changes in volume of the thoracic cavity drive ventilation.
- the volume changes drive pressure gradients
- the movement is driven by muscle
- Inspiration (primary, secondary/accessory)
- Expiration (passive) - Lung
primary muscles of inspiration
- diaphragm completes 2/3 of vital capacity
2. intercostal muscles are important to stabilize the thoracic cavity
secondary/accessory muscles of inspiration
- sternocleidomastoid
2. scalenes
muscles of expiration
- usually passive, diaphragm relaxes
2. force exhalation is helped by the abs contracting and pushing the diaphragm superiorly
Anatomy of the lungs
lobes of the lung are split by fissures
- right lung: 3 lobes
- superior
- middle
- inferior - left lung: 2 lobes
- superior
- inferior - pleura
- visceral lines surface of the lung
- parietal lines inside
- intrapleural space is in between the two above filled with fluid that acts as a lubricant as the thoracic wall moves over the surface of the lung
two components of the airways
- conduction zone: bulk air flow to the site of gas exchange
- respiratory zone: diffusion/gas exchange
conduction zone
bulk air flow to the site of gas exchange
- no gas exchange, so often called anatomical dead space
- diameter is regulated by ANS (opposite of vasculature); want airways to open up and decrease resistance from airflow when symp NS hits
- beta2 receptors excited by NE > dilation via sympathetic
- muscarinic receptors excited by Ach > constriction via parasympathetic - large areas (like trachea and bronchi) are supported by cartilage rings that help keep airways open and prevent collapse
Respiratory zone
diffusion/gas exchange
- alveoli are where gas exchange takes place (50-100m^2 of surface area, but the volume itself is really SMALL, membrane is really thin, surrounder by pulmonary capillaries)
- Pulmonary capillaries vasoconstrict in response to hypoxia (low oxygen in lungs) to direct blood away from that region and match delivery of blood via perfusion - Acinus - respiratory bronchiole with corresponding ducts and sacs
- Bronchioles and Ducts - no supported by cartilage rings, but they are embedded in the parenchyma
sensors of the respiratory system
part of the control system
- mechanoreceptors in the airways
- chemoreceptors in aortic and carotid arteries sense pO2, pCO2, and pH
processors of the respiratory system
medulla and pons cause a change through effectors
effectors of the respiratory system
signal that indicates ventilation needs to increase, it sends increase activity to the nerves and muscles of ventilation and potentially the smooth muscle for bronchodilation
- muscles of ventilation
- smooth muscle in airways
what is an example of the pulmonary system adapting to changing demands?
during rest, VO2 is 250 ml/min and minute ventilation is 5 L/min
during exercise, VO2 is 5000 ml/min and minute ventilation is 100 L/min
what are the main pulmonary processes?
- ventilation
- gas exchange
- gas transport to tissues
- ventilation-perfusion matching
- defense systems
how are lung volumes and capacities measured?
spirometry
What are the different lung volumes and capacities
- TV = tidal volume
- IC = inspiratory capacity
- VC = vital capacity
- I/ERV = Inspiratory/Expiratory Reserve Volume
- FRC = Functional Residual capcacity
- RV = Residual Volume
- TLC = Total Lung Capacity
Tidal Volume
volume of normal breathing = 0.5 L and it is measured pretty easily.
Normal volume of air displaced between normal inhalation and exhalation when extra effort is NOT applied
6-8 mL/kg Ideal Body Weight
Inspiratory Capacity
the volume of air that can be inspired following a normal, quiet expiration
IC = TV + IRV
Inspiratory Reserve Volume
the additional/maximal amount of air that can be inhaled after a normal inspiration (tidal volume)
Vital Capacity
the greatest amount of air that can be expelled from the lungs after taking the deepest possible breath
VC = ERV + RV + FRC
Expiratory Reserve Volume
the additional amount of air that can be expired from the lungs by determined effort after normal expiration
Residual volume
not measured easily
amount of air that remains in a persons lungs after full exhaling
Functional Residual Capacity
volume of air in the lungs at the bottom of a normal exhalation (no motion of the system, resting point of lung + thorax)
elastic recoil pressure of the lung inward equals the elastic recoil pressure of the chest wall outward, alveolar and mouth pressure are both ZERO and there is no airflow
are the capacities normally sums of multiple compartments?
yes
How does air get into the lungs?
- Ventilation = bulk flow of air into and out of the lungs
- Air flows from high pressure to low pressure
- Pin = Alveolar Pressure; Pout = Barometric Pressure
- —-to get air to flow inward, Pin < Pout and it is expelled until pressure is equalized
how does air get out of the lungs
Pin > Pout –> volume decreases
-Mechanical ventilation is a form of positive pressure ventilation, use a pump to decrease the outside pressure
Properties of the thorax
Passive
- volume is large at equilibrium, Pin = Pout, expanding forces = collapsing forces
- Outside forces can cause the thorax to collapse or expand
- once outside force stops acting, thorax will return to equilibrium
- Collapsing > Expanding = crushed tennis ball half
- Expanding > Collapsing = expanded tennis ball half
Properties of the lungs
BALLOON
1. volume can’t be eliminated, but it can be decreased close to 0
2. Outside forces cause the lung to expand and as soon as it stops acting, lung collapses back to equilibrium
3. Lungs have compliance (slinky)
(change in Volume/ change in Pressure)
High compliance vs low compliance
Very compliant = very stretchy, and as volume of lung decreases (slinky at full length)
low compliance = less stretchy, more stiff, and as volume of lung increases (slinky being pulled at last two rings)
Do muscles have to work more to stretch when the lung is at a large volume or a small volume?
LARGE volume
Properties of the lungs and thorax
Passive!
- pleura membrane covers/lines the inside of the pleural cavity and the outside of the lungs
- in between pleural membrane there is a fluid that acts as a cohesive force and allows the lung to be attached to the chest wall (microscope slide comparison)
- thorax wants to expand at equilibrium
- lung wants to collapse at equilibrium
- together, lung expands from thorax and chest wall gets to collapse from their own equilibriums to a new equilibrium (tugging force - pulling apart (-) force)
what pressure keeps the alveoli open?
Pip = Intrapleural pressure (-5 at equilibrium) is what holds the alveoli open
total lung capacity
the larges volume the lungs can attain
Process of ventilation
- Intrapleural lung pressure = -5cm/water at rest, lung pressure at rest = 0, the difference between Palveoli and Pintrapleaural space = +5cm/water
- Begin inhalation/tidal volume, alveoli get pulled open, volume increases in thoracic cage and causes alveoli to expand, decreases pressure and air flows in
- Air continues to flow in until Palveoli = Pout
- Now, pressure increases inside the lungs as we start to exhale
- Air continues to flow out until Palveoli = Pout
