Respiratory System

Nasal cavity

The part of the respiratory system that warms, filters, and moistens air.

Pharynx

A shared area of the respiratory and digestive system.

Epiglottis

A flap of cartilage that covers the trachea when swallowing.

Larynx

Cartilage and mucous membranes that produce sound and speech.

Trachea

The airway containing cartilage rings that keeps it open; lined with cilia and mucus-producing cells.

Ribs

Bone connective tissue that protects the lungs.

Intercostal muscles

Skeletal muscles that contract to raise the ribs, increasing lung volume for inhalation.

Pleural membrane

Lines the lungs and ribs, secreting pleural fluid.

Pleural fluid

A lubricant that holds the lungs to pleural membranes.

Diaphragm

A skeletal muscle that contracts downwards to increase thoracic cavity volume.

Bronchioles

Fine tubes extending from the bronchi that regulate airflow to the lungs.

Bronchus

Two large airways that branch from the trachea.

Alveoli

Small grape-like structures at the terminals of bronchioles where gas exchange occurs.

Inspiration

The process of inhaling air into the lungs, involving diaphragm and intercostal muscle contraction.

Expiration

The process of exhaling air from the lungs, involving diaphragm and intercostal muscle relaxation.

Pulmonary arteries

Arteries that carry deoxygenated blood from the heart to the lungs.

Pulmonary veins

Veins that carry oxygenated blood from the lungs to the heart.

Passive diffusion

Movement of gases from high concentration to low concentration, requiring no energy. occurs directly across cell membranes.

Gas exchange

The process of swapping oxygen and carbon dioxide in the lungs.

Concentration gradient

The difference in concentration of gases between the air in alveoli and blood in capillaries.

Alveoli features for gas exchange

• many small alveoli

• thin alveoli walls

• extensive blood capillary network

• moist surface

many small alveoli

creates large surface area, increasing rate of diffusion

thin alveoli walls

one cell thin creates less diffusion distance, increased rate of diffusion

extensive blood capillary network

wrapped around the alveoli, large surface area for gas exchange between blood & alveoli

moist surface

allows gases to dissolve for increased rate of diffusion

maintaining concentration gradient

• constant blood flow / heart beat

• constant breathing / ventilation of lungs

• cellular respiration

constant blood flow / heart beat

• constant flow of low O₂ blood + high CO₂ concentration

constant breathing / ventilation of lungs

• replaces O2 and expels CO2

• air in lungs always has high O₂ concentration and low CO₂ concentration

cellular respiration

• uses O₂ and CO₂ as waste, returns to lungs in deoxygenated blood