Circulatory_System

Circulatory System

The system that pumps and directs blood through blood vessels to deliver nutrients and oxygen to tissues and remove waste.

Cardiovascular System

Consists of the heart and blood vessels, responsible for systemic and pulmonary circulation.

Atria

The two upper chambers of the heart where blood enters before traveling to the ventricles.

Ventricles

The two lower chambers of the heart that pump blood out to the lungs and the rest of the body.

Myocardium

The cardiac muscle that makes up the bulk of the heart wall, thicker in the ventricles than in the atria.

Pericardium

A fibrous sac surrounding the heart, lined by a serous mesothelium.

Endothelium

A simple squamous epithelium lining blood and lymphatic vessels.

Lymphatic System

A network that returns proteins and interstitial fluid to the bloodstream; does not contain blood.

Pulmonary Circulation

The passage of blood from the heart to the lungs and back to the heart.

Systemic Circulation

The flow of blood from the heart to the rest of the body and back to the heart.

Arteries

Blood vessels that carry blood away from the heart.

Capillaries

The smallest blood vessels, where exchange of oxygen, carbon dioxide, nutrients, and wastes occurs.

Veins

Blood vessels that carry blood back to the heart.

Atrioventricular Valves

Valves between the atria and ventricles that prevent backflow into the atria.

Semilunar Valves

Valves that prevent backflow of blood from the arteries into the ventricles.

Sinoatrial Node

The heart's natural pacemaker that initiates electrical impulses and regulates the heartbeat.

Baroreceptors

Sensory receptors that monitor blood pressure changes, located in carotid arteries and the aortic arch.

Chemoreceptors

Sensory receptors that monitor blood CO2 and O2 levels and pH.

Vasa Vasorum

Small vessels that supply blood to the walls of larger blood vessels.

Precapillary Sphincters

Smooth muscle cells that regulate blood flow into capillary beds.

Continuous Capillaries

Capillaries with a continuous endothelial lining; found in muscle and nervous tissue.

Fenestrated Capillaries

Capillaries with pores in the endothelium, allowing for greater substance exchange; found in kidneys.

Sinusoids

Discontinuous capillaries with larger diameters and gaps between endothelial cells; allow for extensive exchange.

Valves in Veins

Thin folds of tunica intima that help prevent backflow of blood in veins.

Lymphatic Capillaries

Capillaries that collect lymph fluid from tissues and return it to blood circulation.

Pericytes

Contractile cells associated with capillaries that help regulate blood flow.

Connective Tissue in Blood Vessels

Provides structural support and strength to blood vessels; includes collagen and elastic fibers.

Smooth Muscle in Blood Vessels

Muscle tissue that regulates the diameter of blood vessels, affecting blood flow and pressure.

Interstitium

The space between cells in a tissue, where lymphatic capillaries begin.

Postcapillary Venules

The primary site at which white blood cells exit the circulation.

Cardiac Skeleton

Connective tissue framework of the heart that separates atrial and ventricular musculature.

Functional Role of Endothelium

Acts as a semipermeable barrier and secretes factors that regulate clotting and vascular tone.