Veins/ Arterys/ Capillaries

Arteries

Thick, elastic, muscular vessels that carry blood away from the heart under high pressure.

Arterioles

Small arteries that regulate blood flow and pressure by vasoconstriction or vasodilation.

Capillaries

Microscopic vessels (one cell layer thick) where gas, nutrient, and waste exchange occurs.

Venules

Small veins that collect blood from capillaries and direct it toward veins.

Veins

Thin-walled vessels with valves that carry blood toward the heart and act as volume reservoirs.

Lumen

The central space inside a blood vessel through which blood flows.

Angiogenesis

The formation of new blood vessels from existing ones.

Blood Pressure (BP)

The force of blood against vessel walls, generated by the heart’s contraction.

Cardiac Output (CO)

The volume of blood pumped per minute; increased CO raises blood pressure.

Peripheral Resistance

Opposition to blood flow due to vessel friction; increased resistance raises blood pressure.

Systolic Pressure

Arterial pressure during ventricular contraction.

Diastolic Pressure

Arterial pressure during ventricular relaxation.

Mean Arterial Pressure (MAP)

The average arterial pressure; MAP = DP + 1/3(SP - DP).

Elastic Rebound (Pressure Reservoir)

Arteries stretch during systole and recoil during diastole to maintain flow.

Vasoconstriction

Narrowing of blood vessels that increases resistance and blood pressure.

Vasodilation

Widening of blood vessels that decreases resistance and blood pressure.

Turbulence

Irregular, swirling blood flow caused by plaques or branching; increases resistance.

Aneurysm

A bulge or ballooning in a weakened artery wall that may rupture.

Capillary Exchange

Movement of fluids and solutes across capillary walls via diffusion, filtration, and reabsorption.

Diffusion

Movement of molecules from high to low concentration (O2, CO2, glucose).

Filtration

Fluid pushed out of capillaries by hydrostatic pressure (blood pressure).

Reabsorption

Fluid pulled into capillaries by colloid osmotic pressure (plasma proteins).

Hydrostatic Pressure (HP)

The physical force of fluid pushing against vessel walls.

Colloid Osmotic Pressure (COP)

The osmotic pull exerted by plasma proteins to draw water into the capillaries.

Net Filtration Pressure (NFP)

The difference between HP and COP that determines fluid movement.

Interstitial Tissue

The space between cells containing interstitial fluid.

Edema

Excess fluid buildup in interstitial tissue when filtration exceeds reabsorption.

Vasomotion

Rhythmic opening and closing of precapillary sphincters that regulate capillary blood flow.

Cardiac Center

Part of the medulla oblongata that regulates heart rate and cardiac output.

Vasomotor Center

Medullary center controlling vessel diameter via sympathetic stimulation.

Respiratory Center

Controls breathing rate and depth, influencing CO2, O2, and pH levels.

Baroreceptor Reflex

Detects changes in blood pressure (found in carotid sinuses, aortic sinuses, and right atrium).

Chemoreceptor Reflex

Detects changes in CO2, O2, and pH (found in carotid and aortic bodies).

Venous Return

Flow of blood back to the heart through the veins.

Valves (in veins)

Prevent backflow of blood and ensure one-way movement toward the heart.

Skeletal Pump (Muscular Compression)

Muscle contractions that squeeze veins and help move blood toward the heart.

Respiratory Pump

Pressure changes during breathing that aid venous return to the heart.

Foramen Ovale

Fetal opening between the right and left atria that bypasses the lungs.

Ductus Arteriosus

Fetal vessel connecting the pulmonary trunk to the aorta, bypassing the lungs.

Ductus Venosus

Fetal vessel that bypasses the liver, directing blood to the inferior vena cava.

Pulmonary Circuit

Blood pathway from right ventricle → pulmonary arteries → lungs → pulmonary veins → left atrium.

Continuous Capillaries

Capillaries with tight junctions allowing limited exchange (found in muscles, brain).

Fenestrated Capillaries

Capillaries with small pores allowing rapid exchange (found in kidneys, intestines).

Sinusoid Capillaries

Capillaries with large gaps allowing passage of large molecules and cells (found in liver, spleen).