Chapter 17: Mechanics of Breathing Flashcards
what are the respiratory system functions?
- Exchange of gases between the atmosphere and the blood
- Contributing to the regulation of acid-base balance in the blood
- Vocalization
- Defense against pathogens and foreign particles in the airways
- Route for water and heat loss
- Enhancing venous return (respiratory pump)
what does internal respiration involve?
oxidative phosphorylation
what are the four processes of external respiration?
- Pulmonary ventilation
- Exchange between lungs and blood
- Transportation in blood
- Exchange between blood and body tissues
- *airways from pharynx to lungs
- conducting zone
- respiratory zone
respiratory tract
- consists of:
- larynx
- trachea
- bronchi
- secondary bronchi
- tertiary bronchi
- bronchioles
- terminal bronchioles
conducting zone
consists of glottis and epiglottis
larynx
- 2.5 cm diameter
- 10 cm long
- 15-20 C shaped bands of cartilage
trachea
- Three on right side to three lobes of right lung
- Two on left side to two lobes of left lung
secondary bronchi
20–23 orders of branching
tertiary bronchi
less than 1 mm in diameter
bronchioles
- Air passageway: 150 mL in volume (dead space)
- Increases air temperature to body temperature
- Humidifies air
functions of conducting zone
consists of goblet cells and ciliated cells
epithelium of conducting zone
secrete mucus
goblet cells
- Cilia move particles toward mouth
- Mucus escalator
ciliated cells
secrete saline and mucus
Epithelial cells lining the airways and submucosal
glands
move the mucus layer toward the pharynx, removing trapped
pathogens and particulate matter
cilia
creates 80 million bronchiooles
branching of airways
- Exchange of gases between air and blood
- Mechanism of action: diffusion
function of respiratory zone
what are the structures of the respiratory zone?
- Respiratory bronchioles
- Alveolar ducts
- Alveoli
- Alveolar sacs
surrounded by elastic fibers and a network of capillaries`
each cluster of alveoli
- Respiratory membrane
- Epithelial cell layer of alveoli
- Endothelial cell layer of capillaries
epithelium of respiratory zone
- site of gas exchange
- 300 million in the lungs
- rich blood supply from capillary sheet
alveoli
what are the types of alveoli?
- alveolar pores
- type I alveolar cells
- type II alveolar cells
- alveolar macrophages
- make up wall of alveoli
- single layer of epithelial cells
- for gas exchange
type I alveolar cells
secrete surfactant
type II alveolar cells
ingests foreign material
alveolar macrophage
- airtight, protects lungs
- consists of:
- rib cage
- sternum
- thoracic vertebrae
- muscles (internal and external intercostals, diaphragm)
chest wall
- membrane lining of lungs and chest wall
- sac around each lung
pleura
- filled with intrapleural fluid
- volume = 15 mL
intrapleural space
how does air move in and out of the lungs?
bulk flow
what drives the flow of air?
pressure gradient
in what direction does air move?
from high to low pressure
pressure in lungs less than atmospheric pressure
inspiration
pressure in lungs greater than atmospheric pressure
expiration
Atmospheric pressure=
Patm
- Pressure of air in alveoli
- Palv
intra-alveolar pressure
- pressure inside pleural sac
- Pip
intrapleural pressure
what are the pulmonary pressures?
- Atmospheric pressure
- intra-alveolar pressure
- intrapleural pressure
- 760 mm Hg at sea level
- Decreases as altitude increases
- Increases under water
atmospheric pressure
are given relative to atmospheric pressure (set Patm= 0mmHg)
other lung pressures
- pressure of air in alveoli
- given relative to atmospheric pressure
- varies with phase of respiration
intra-alveolar pressure
when is intra-alveolar pressure negative (less than atmospheric)?
during inspiration
when is intra-alveolar pressure positive (more than atmospheric)?
during expiration
drives ventilation
Difference between Palv and Patm
- pressure inside pleural sac
- varies with phase of respiration
intrapleural pressure
- Always negative under normal conditions
- Always less than Palv
pressure inside pleural sac
what is the intrapleural pressure at rest?
-4mm Hg (vacuum)
prevents wall and lungs from pulling apart
surface tension of intrapleural fluid
keeps the lung adhered to the chest wall, in a normal lung at rest
pleural fluid
creates an inward pull
elastic recoil
tries to pull the chest wall outward
elastic recoil of the chest wall
-If the sealed pleural cavity is opened to the
atmosphere, air flows in. –The bond holding the lung to the chest
wall is broken, and the lung collapses
-air in thorax
pneumothorax
what is movement of air in and out of the lungs due to?
pressure gradients
describes mechanisms for creating pressure gradients
mechanics of breathing
force for flow=
pressure gradient (mechanics of breathing)
remains constant during breathing cycle
atmospheric pressure
do alveolar pressure changes affect gradients?
yes
pressure is inversely related to volume
Boyle’s law
related to airway radius and mucus
resistance to air flow (R)
flow =
mechanics of breathing
Patm-Palv/R
how can you change alveolar pressure?
by changing its volume
V=1/P
relationship says that if the volume of gas increases, the pressure decreases and vice versa
PV=nRT
ideal gas equation
P1V1=P2V2
boyle’s law expresses the inverse relationship between pressure and volume
what are the determinants of intra-alveolar pressure?
- factors determining intra-alveolar pressure
- lungs expand-alveolar volume increases
- lungs recoil-alveolar volume decreases
what are the factors determining intra-alveolar pressure?
- quantity of air in alveoli
- volume of alveoli
- alveolar volume increases
- Palv decreases
- pressure gradient drives air into lungs
lungs expand
- alveolar volume decreases
- Palv increases
- pressure gradient drives air out of lungs
lungs recoil
moves
sternum upward and outward
expansion of ribs during inspiration
when does the diaphragm and external intercostals contract?
during inspiration
when do the chest wall and lungs expand?
during inspiration
when do the external intercostals and diaphragm relax?
expiration
when do the internal intercostals and abdominals contract?
only for active expiration
when do the chest cavity and lungs contract?
during expiration
when do the ribs and sternum depress?
during expiration
what are the factors affecting pulmonary ventilation?
- lung compliance
- airway resistance
-Change of volume (V) that results from a given force or pressure (P) exerted on the lung
=ΔV/ΔP
-ease with which lungs can be stretched
lung compliance
when is it easier to inspire?
when there is a larger lung compliance
requires more force from inspiratory muscles to stretch
low compliance lung
what are the factors affecting lung compliance?
- elastance (elastic recoil)
- surface tension of lungs
- Low elastance → high compliance
- Balloon vs plastic bag
elastance
- Thin layer of fluid lines alveoli
- arises due to attractions between water molecules
- Greater tension → less compliant
surface tension of lungs
how can surface tension be overcome?
-surfactant secreted from type II cells
- detergent that decreases surface tension
- more concentrated in smaller alveoli
- increases lung compliance, makes inspiration easier
surfactant
what happens when airways get smaller in diameter?
-they increase in number, keeping overall resistance low
what does an increase in resistance result in?
- make it harder to breath
- contraction activity of smooth muscle
- mucus secretion
what is the role of bronchiolar smooth muscle in airway resistance?
- bronchoconstriction
- bronchodilation
- contractile state of bronchiolar smooth muscle under extrinsic and intrinsic controls
smooth muscle contracts, causing radius to decrease
Bronchoconstriction
smooth muscle relaxes, causing radius to increase
Bronchodilation
what is involved in the extrinsic control of the bronchiole radius?
- autonomic nervous system
- hormonal control
-parasympathetic
-contraction of smooth
muscle
-bronchoconstriction
autonomic nervous systems
- epinephrine
- relaxation of smooth muscle
- bronchodilation
hormonal control
what is involved in the intrinsic control of the bronchiole radius?
- CO2: bronchodilation
- histamine: bronchoconstriction
- Released during asthma and allergies
- Also increases mucus secretion
Histamine: bronchoconstriction
what is involved in total lung capacity?
- tidal volume
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- 500 mL
- single,unforced breath
tidal volume (Vt)
- 3000mL
- after breathing in, volume you can still inspire
inspiratory reserve volume (IRV)
- 1000mL
- after breathing out, volume you can still expire
expiratory reserve volume (ERV)
- 1200 mL
- volume left after ERV
residual volume (RV)
= VT + IRV = 3500 mL
Inspiratory capacity (IC)
- maximum volume expired after maximum inspiration
- VC = VT + IRV + ERV = 4500 mL
vital capacity
= volume remaining after resting tidal volume
-FRC = ERV + RV = 2200 mL
functional residual capacity
- volume air in lungs after maximum inspiration
- TLC = VT + IRV + ERV + RV = 5700 mL
total lung capacity
- difficulty expelling air
- associated with increased airway resistance
- residual volume increases (making it more difficult to expire)
- vital capacity decreases
obstructive pulmonary diseases
what are some major obstructive pulmonary diseases?
- COPD (chronic bronchitis and emphysema)
- asthma
- difficulty expanding lungs
- involve structural damage to the lungs
restrictive pulmonary diseases
what happens when the lungs are damaged structurally due to restrictive pulmonary diseases?
- decrease in lung compliance
- total lung capacity decreases
- vital capacity decreases
- pulmonary fibrosis (fibrous scar tissue)
- asbestos
maximum-volume inhalation followed by exhalation as fast as possible
forced vital capacity (FVC)
what does a low FVC indicate?
restrictive pulmonary disease
percentage of FVC that can be exhaled within certain time frame
forced expiratory volume (FEV)
percentage of FVC that can be exhaled within 1 second
FEV1
what is a normal FEV1?
80%
what does a FEV <80% indicate?
obstructive pulmonary disease
total volume of air entering and leaving the respiratory system each minute
minute ventilation
= VT × RR
minute ventilation
Normal respiration rate =
12 breaths/minute
Normal VT =
500 mL
Normal minute ventilation =
500mL x 12 breaths/min= 6000 mL/min
Air in conducting zone does not participate in gas exchange
anatomical dead space
- equals the anatomical dead space
- about 150 mL
conducting zone
-Volume of fresh air reaching the gas exchange areas per minute
=(VT × RR) – (DSV × RR)
-normal is 4200 mL/min
alveolar ventilation
why are the conducting airways known as anatomic dead space?
because they don’t exchange gases with the blood
