Pulmonary System

Primary functions include

Air distribution

Gas exchange

Regulate blood pH

Protection

Speech

Smell

Nose and nasal cavity

Warms, humidifies and filters air

produce mucus

Pharynx (throat)

Passageway for air and food

Connects nasal cavity and mouth to larynx
and esophagus

Larynx

Voice box
Made of cartilage

Epiglottis

Flap of skin on trachea

Moves when swallowing and speaking

Closes off trachea when swallowing food

Trachea

Windpipe
Conducts air into lungs
Larynx to bronchi

Cartilage rings

Prevents trachea from collapsing

Smooth and C-shaped

Bronchial tree

Bronchi

Bronchioles

Bronchi

Tubes that branch off trachea and enter lungs

Ciliated

Has cartilage

Bronchioles

Smaller airways that branch into microscopic alveolar ducts

Terminate into alveoli

Alveoli

Tiny air sacs where gas exchange with blood occurs

Weibel Model

Used to describe branching architecture of airways in the lungs

Describes how structure influences airflow and gas exchange

What generation is the trachea?

Z0

What generations make up the upper bronchial?

Z1-16

Conducting zone

Gets air in and out

Upper bronchial

Transitional and respiratory zones

Gas exchange

Z17-23

What angle are the bronchial tree branches?

35 degrees

Lungs

3 lobes in left

2 lobes in right

Visceral pleural

Inner layer membrane of lung

Parietal pleura

Outer layer of lung

Intrapleural fluid

Separates the two pleural membranes, lubricates them for smooth movement

What enables coordinated movement of lungs and thoracic wall during normal breathing?

Changes in hydrostatic pressure of the intrapleural fluid

Rib cage

forms the top and sides of the thoracic cavity

Intercostal muscles

Positioned between the ribs

Diaphragmatic

Muscle located at the base of the thoracic cavity

How are the lungs attached to the thoracic wall?

Via the pleural cavity

Boyle’s Law

At constant temperature, pressure of amount of a gas is inversely related to its volume

Inspiration

Inhalation

Expiration

Exhalation

What is atmospheric pressure?

760 mmHg

What if atmospheric pressure is greater than lung pressure?

Air flows in (inspiration)

What if atmospheric pressure is less than lung pressure?

Air flows out (expiration)

What if the thorax increases in size?

Decrease in pressure

Air flows in

What if the thorax decreases in size?

Increase in pressure

Air flows out

What happens when the diaphragm contracts?

Downward movement

Thoracic cavity expands

Air enters

What happens when the diaphragm relaxes?

Upward movement

Thoracic cavity decreases

Air expelled

Tidal volume (TV)

Amount of air exhaled normally after a typical inspiration
(normal= about 500 mL)

Inspiratory reserve volume (IRV)

Amount of air that can be forcibly inhaled over and above normal (deep breath; about 3000 mL)

Expiratory reserve volume (ERV)

Additional amount of air forcibly expired after tidal expiration (1000-1200 mL)

Residual volume (RV)

Amount of air that stays trapped in the alveoli (~1.2 liters)

Vital capacity

Largest volume of air an individual can move in and out of lungs
Sum of IRV + TV + ERV

How does gas exchange occur?

Diffusion across respiratory membrane

Driven by differences in partial pressures of gases between alveoli and blood

What two gases contribute to the gradient?

O2 and CO2

Eupnea

normal, quiet breathing (12-20 breaths per minute)

Hyperpnea

increase in breathing to meet an increased demand for O₂ by body

Hyperventilation

increase in pulmonary ventilation in excess of need for oxygen

Leads to hypocapnia

Hypocapnia

Reduced CO2 levels in blood

Hypoventilation

decrease in pulmonary ventilation

Leads to hypoxia and hypercapnia

Insufficient gas exchange in lungs

Hypoxia

Reduced O2 in blood

Hypercapnia

Increased CO2 in blood

Apnea

Temporary cessation of breathing

Asthma

Chronic inflammation of airways, making them narrow and more difficult to breathe through

Leading chronic disease in children

Cause of asthma

Likely combination of genetic and environmental factors

Later asthma more associated with environmental

Hygiene hypothesis

lack of immune system exposure increases risk of developing allergic disease

Curschmann’s spirals

Accumulation of mucus in bronchi

Block exchange of air

Asthma exacerbation

worsening of asthma symptoms that occurs gradually or suddenly

Asthma attack

acute, severe episode of asthma exacerbation

What role do Th2 cells play in Asthma pathogenesis?

Asthma is often due to excessive reaction of Th2 cells against specific allergens

Th2 releases cytokines such as IL-4, IL-5, IL-13

IL-4

stimulates B cells to produce IgE antibodies

IL-5

recruits and activates eosinophils

Airway inflammation

IL-13

Involved in mucus production

Airway obstruction

Bronchoconstriction

Smooth muscles around bronchioles start to spasm

Narrow airways

Airway Inflammation

Swelling, increased mucus secretion and bronchoconstriction

May lead to structural changes

Airway Hyperreactivity

Inflamed airways become overly sensitive to various stimuli

Are inflammatory changes irreversible?

Yes, if they are not long term

Chronic obstructive pulmonary disease (COPD)

Airways become obstructed and lungs don’t empty properly, leaving air trapped inside lungs

Not fully reversible

Most common cause of COPD

Tobacco smoke leads to chronic inflammation

Spirometry

Measures flow of air through lungs

Estimates amount of air in lungs

Forced vital capacity (FVC) is the

maximum amount of air you can forcefully and completely blow out after taking a deep breath in

Forced expiratory volume (FEV1)

amount of air you can blow out in one second

COPD Diagnosis

Having a FEV1/FVC ratio <70% is indicative of airflow obstructive patterns and suggests presence of COPD

Management of COPD

Incentive spirometer
Encourages deep breaths, improving lung function

Chronic Bronchitis

persistent inflammation of the airways leads to narrowing of bronchial tubes and overproduction of mucus

Clinical features of chronic bronchitis

Chronic cough with mucus

Sputum production

Difficulty breathing

Emphysema

Inflation or swelling of alveoli

Hypoxemia

Pathophysiology of Emphysema

Proteases released from inflammatory chemicals break down collagen and elastin contributing to structural changes and reducing tissue elasticity

Who is at high risk for emphysema?

Individuals with AAT (protease inhibitor) deficiency

What happens when an emphysema patient exhales?

The airway collapses, trapping air

Symptoms of Emphysema

Dyspnea or SOB

Barrel-shaped chest

Small amount of sputum cough

Hypoxic Vasoconstriction

Poor gas exchange in one lung area causes vasoconstriction of pulmonary arteries, shunting blood to areas with better exchange

Increased workload on right side to heart can cause it to enlarge and fail

Hypoxic Vasoconstriction in Emphysema

Widespread poor gas exchange

Leads to pulmonary hypertension