40- Lung Volumes and Capacities

whats the conducting zone

portion of resp system that extends from nose to terminal bronchioles and brings air into and out of lungs

structures included in conducting zone

Nose, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles.

functions of conducting zone

• Conducts, humidifies, warms, and filters air before it reaches the gas exchange surfaces.

• Contains ciliated epithelium and mucus-producing cells for particle clearance.

• Has cartilage (in trachea and bronchi) to prevent airway collapse.

• No alveoli → no gas exchange (this area = anatomic dead space)

whats the respiratory zone

part of the lung “where gas exchange occurs.

structures included in resp zone

• Respiratory bronchioles, alveolar ducts, and alveoli

functions of resp zone

• Site of O₂ and CO₂ exchange between air and blood.

• Walls lined by type I and type II alveolar cells (type II secretes surfactant).

• No cartilage or cilia.

• Contains large surface area and thin diffusion distance to facilitate rapid gas exchange.

location of cilia 

lining of conducting airways (trachea to terminal bronchioles)

function of cilia

• Sweep mucus and trapped particles upward toward the pharynx → part of the mucociliary escalator.

• Help keep alveoli sterile.

location of smooth muscle in resp

Bronchi and bronchioles (especially bronchioles)

• conducting zone transition to resp bronchioles

function of smooth muscle in resp

Regulates airway diameter → controls airflow resistance.

Contracts with parasympathetic (ACh) and relaxes with sympathetic β₂-receptors (Epi/NE) or β₂-agonists.

location of cartilage in resp sys

Trachea and bronchi only

function of cartilage in resp sys

Provides rigid support so airways don’t collapse during inspiration when intrathoracic pressure falls.

• Absent in bronchioles, which rely on smooth-muscle tone instead.

define pores of kohn

The pores of Kohn are small openings between adjacent alveoli that allow air to pass from one alveolus to another.

function of pores of kohn

• Their role is to provide collateral ventilation, which helps equalize pressure among alveoli and maintains inflation if a bronchiole becomes obstructed.

• They also permit the spread of infection or debris between alveoli.

what zone are pores of kohn found

Respiratory zone (within alveolar walls)

description and physio meaning to vesicular sounds (normal)

Soft, low-pitched; heard over most lung fields

gentle rustling, fades on expiration

description and physio meaning to bronchial sounds (normal)

Loud, high-pitched; heard over substernal notch

louder, espiratory lasts longer, silent internal

description and physio meaning to bronchovesicular sounds (normal)

normal

heard over 1 and 2 intercostal space anteriorly and between scapulae posteriorly intermediate intensity

description and physio meaning to fine crackles sounds (abnormal)

Discontinuous popping during inspiration

Opening of collapsed small airways; seen in fibrosis, pneumonia, pulmonary edema

description and physio meaning to wheezes sounds (abnormal)

Continuous musical tones, mainly on expiration

Narrowed airways (bronchospasm / asthma / COPD).

description and physio meaning to rhonchi sounds (abnormal)

Low-pitched, gurling, continuous

Airflow through mucus; may clear with coughing

description and physio meaning to coarse crackles sounds (abnormal)

discontinuous, low pitched, louder and longer