Lesson 15: Gas exchange in multi-celled animals

1 atmosphere

Standard unit of pressure equal to the air pressure at sea level.

760 mmHg

The pressure exerted by a 760‑millimeter column of mercury; equal to 1 atmosphere.

Alveoli

Tiny air sacs in the lungs where oxygen and carbon dioxide are exchanged with the blood.

Asthma

A chronic condition in which airways become inflamed and narrowed, making breathing difficult.

Barometer

An instrument used to measure atmospheric pressure.

Bicarbonate

The main form in which carbon dioxide is transported in the blood.

Bohr shift

A decrease in hemoglobin’s affinity for oxygen when carbon dioxide levels or acidity increase.

Bronchi

Two large air passages that branch from the trachea into the lungs.

Bronchioles

Small branching airways inside the lungs that lead to the alveoli.

Bronchitis

Inflammation of the bronchi, causing coughing and difficulty breathing.

Buccal cavity

The mouth cavity; in some animals, it helps move air into the lungs.

Carbonic acid

A weak acid formed when carbon dioxide reacts with water in the blood.

Chloride shift

The movement of chloride ions into red blood cells as bicarbonate ions leave, maintaining charge balance.

Chronic obstructive pulmonary disease

A group of lung diseases (including emphysema and chronic bronchitis) that block airflow.

Cilia

Tiny hair‑like structures that move mucus and trapped particles out of the airways.

Concurrent exchange

A gas‑exchange system where blood and water flow in the same direction, limiting efficiency.

Countercurrent exchange

A system where blood and water flow in opposite directions, maximizing gas exchange.

Deoxyhemoglobin

Hemoglobin that is not bound to oxygen.

Diaphragm

A dome‑shaped muscle below the lungs that contracts to draw air into the lungs.

Diffusion

The movement of molecules from an area of higher concentration to lower concentration.

Emphysema

A lung disease where alveoli are damaged, reducing surface area for gas exchange.

Epiglottis

A flap of cartilage that prevents food from entering the trachea during swallowing.

Exhalation

The process of breathing out air from the lungs.

External intercostal muscles

Muscles between the ribs that contract to expand the chest during inhalation.

Fick’s law of diffusion

The rate of diffusion depends on surface area, concentration difference, and distance.

Gas exchange

The process of oxygen entering the blood and carbon dioxide leaving the blood.

Glottis

The opening between the vocal cords that leads into the trachea.

Hemocyanin

An oxygen‑carrying protein containing copper, found in arthropods and mollusks.

Hemoglobin

An iron‑containing protein in red blood cells that carries oxygen.

Inhalation

The process of breathing air into the lungs.

Larynx

The voice box; keeps the airway open and produces sound.

Lung cancer

A disease caused by uncontrolled cell growth in lung tissue.

Lungs

Paired organs that perform gas exchange between air and blood.

Negative pressure breathing

Breathing method where air is pulled into the lungs by expanding the chest cavity.

Opercular cavities

Spaces in fish that hold water as it passes over the gills.

Operculum

A bony flap that covers and protects fish gills.

Oxyhemoglobin

Hemoglobin bound to oxygen.

Oxyhemoglobin dissociation curve

A graph showing how hemoglobin’s oxygen binding changes with oxygen concentration.

Papulae

Small surface projections that increase surface area, aiding gas exchange in some animals.

Parabronchi

Tiny tubes in bird lungs where gas exchange occurs.

Partial pressure

The pressure exerted by an individual gas in a mixture of gases.

Pharynx

A shared passageway for air and food behind the mouth and nasal cavity.

Positive pressure breathing

Breathing method where air is forced into the lungs (e.g., amphibians).

Trachea

The windpipe that carries air from the larynx to the bronchi.

Ventilation

The movement of air into and out of the lungs.