Circulation and Gas Exchange

Respiratory system

Draws in gases from the environment, intakes O2 and outputs CO2.

Circulatory system

Transports O2, CO2, nutrients, hormones, and blood cells.

Ventilation

Movement of air or water through organs of gas exchange, like lungs or gills.

Gas exchange

Diffusion of O2 and CO2 at respiratory tissue surface.

Circulation

Transport of diffused gases throughout the body.

Cellular respiration

O2 is the final electron acceptor of the ETC; CO2 is a byproduct of glycolysis and citric acid cycle.

Pulmonary circulation

Carries deoxygenated blood from the heart to the lungs and oxygenated blood back to the heart.

Systemic circulation

Oxygen-rich blood moves through arteries to tissues throughout the body.

Endothelium

Epithelial tissue that lines the interior surface of blood vessels and lymphatic vessels.

Arteries

Transport blood away from the heart, oxygenated in the systemic loop and deoxygenated in the pulmonary loop.

Veins

Transport blood to the heart, deoxygenated in systemic loop and oxygenated in pulmonary loop.

Capillaries

Tiny vessels with walls only one-cell thick, the only site of exchange between blood and tissues.

Heart

Muscular organ that contracts to generate pressure waves that push blood through blood vessels.

Atria

Chambers of the heart that receive blood from veins.

Ventricles

Chambers of the heart that receive blood from atria and pump blood into arteries.

Atrioventricular valves

Valves that prevent backflow from ventricle to atrium.

Semilunar valves

Valves that prevent backflow from arteries to ventricles.

Heart murmur

Abnormal sound due to blood moving back across a valve, often from damage or infection.

Pulmonary artery

Delivers deoxygenated blood from the heart to the capillary beds in the lungs.

Pulmonary veins

Deliver oxygenated blood from the lungs back to the heart.

Aorta

Delivers oxygenated blood from the heart to the tissues.

Venae cava

Deliver deoxygenated blood to the heart from capillary beds in the body's tissues.

Pharynx

Throat area behind the mouth, shared passage for air, food, and water.

Trachea

Brings air from pharynx to lungs, supported by c-shaped cartilage rings.

Lungs

Organs of respiration that inhale air to absorb O2 and exhale CO2.

Alveoli

Grape-like ends of bronchioles where gas exchange occurs.

Surfactant

Mix of phospholipids and proteins produced by some alveoli to reduce surface tension.

Diaphragm

Sheet of muscle that separates thoracic and abdominal cavities.

Plasma

Special extracellular matrix that composes the liquid part of blood.

Platelets

Small cell fragments involved in blood clotting.

Thrombus

Clot that forms in a blood vessel blocking blood flow.

White blood cells (leukocytes)

Immune system cells that help identify and fight infections.

Red blood cells (erythrocytes)

Carry O2 from the lungs via hemoglobin; lack nuclei at maturity.

Erythropoietin

Hormone secreted by the kidney to stimulate RBC production in bone marrow.

Hemoglobin

Protein made of 4 polypeptide subunits that binds oxygen.

Myoglobin

Primary pigment of skeletal muscles that binds O2 tighter than hemoglobin.

Sickle-cell disease

Abnormal form of hemoglobin that aggregates in RBCs, distorting shape.

Lymphatic system

Network of vessels that carries lymph toward the heart.

Lymph

Clear fluid that circulates through the lymphatic system.

Lymph nodes

Organs of the lymphatic system that are critical to immune function.