Blood Vessels and Their Functions

Blood Vessels

• There are three types of blood vessels: arteries, capillaries, and veins.
• Arteries carry oxygenated blood away from the heart to the body's tissues, except for the pulmonary arteries, which carry deoxygenated blood to the lungs.
• Capillaries facilitate the exchange of oxygen, carbon dioxide, nutrients, and waste products between the blood and tissues.
• Veins carry deoxygenated blood from the tissues back to the heart, except for the pulmonary veins, which carry oxygenated blood from the lungs to the heart.

Blood Vessel Colors

• Blue represents deoxygenated blood.
• Red represents oxygenated blood.

Blood Flow Sequence

• The sequence of blood flow is: arteries → arterioles → capillaries → venules → veins.

Comparing Arteries and Veins

• Arteries carry blood away from the heart, while veins carry blood towards the heart.
• Arteries have high pressure, while veins have low pressure.
• Both arteries and veins have three tunics (intima, media, and externa) in their walls, but arteries have a thicker tunica media with more smooth muscle and elastic fibers.
• Arteries do not have valves, except for the pulmonary artery and aorta, which have semilunar valves. Veins have valves to prevent backflow of blood.

Microscopic Vessels

• Capillaries, arterioles, and venules are microscopic vessels.

Vasoconstriction and Vasodilation

• Vasoconstriction is the narrowing of blood vessels, resulting in increased blood pressure.
• Vasodilation is the widening of blood vessels, resulting in decreased blood pressure.

Importance of Arterioles

• Arterioles are critical in regulating blood flow to capillaries and controlling blood pressure by constricting or dilating.

Perfusion

• Perfusion is the process of delivering blood to the capillary bed in the tissues.
• It ensures that tissues receive sufficient oxygen and nutrients and that waste products are removed efficiently.

Blood Pressure

• Blood pressure is the force exerted by circulating blood on the walls of blood vessels.
• It is measured using a sphygmomanometer.
• The brachial artery is the most commonly used blood vessel for measuring blood pressure.

Blood Pressure Components

• Systolic pressure (top number) is the highest pressure in the arteries when the heart beats.
• Diastolic pressure (bottom number) is the lowest pressure in the arteries when the heart is at rest.

Normal Blood Pressure

• Normal blood pressure is 120/80 mmHg.

Pulse

• Pulse is the rhythmic expansion and recoil of arteries resulting from heart contractions.
• It can be felt where arteries are close to the skin, such as the radial artery (wrist), carotid artery (neck), brachial artery (inner elbow), femoral artery (groin), and popliteal artery (behind the knee).