Blood Vessels

Types of Blood Vessels Artery – carries blood away from the heart Artery – carries blood away from the heart Vein – A vessel that carries blood towards the heart Vein – A vessel that carries blood towards the heart Capillaries – microscopic vessels that carry blood from small arteries to small viens Capillaries – microscopic vessels that carry blood from small arteries to small viens

The Pathway of Blood ArteryArterioleCappillaryVenuoleVein

Blood Vessel Structure Tunica Intima (endothelium) Tunica Intima (endothelium) Tunica Media (smooth muscle; elastic connective tissue) Tunica Media (smooth muscle; elastic connective tissue) Tunica Adventitia (fibrous type of vessel connective tissue) Tunica Adventitia (fibrous type of vessel connective tissue)

Arteries Tunica Intima – Smooth lining Tunica Intima – Smooth lining Tunica Media – Allows constriction and dilation of vessels; thicker than in veins; muscle innervated by autonomic fibers Tunica Media – Allows constriction and dilation of vessels; thicker than in veins; muscle innervated by autonomic fibers Tunica Adventitia – Provides flexible support that resists collapse or injury; thicker than in veins; thinner than tunica media Tunica Adventitia – Provides flexible support that resists collapse or injury; thicker than in veins; thinner than tunica media

Veins Tunica Intima – Smooth lining with semi-lunar valves to ensure one way blood flow Tunica Intima – Smooth lining with semi-lunar valves to ensure one way blood flow Tunica Media – Allows constriction and dilation of vessels; thinner than in arteries; muscle innervated by autonomic fibers Tunica Media – Allows constriction and dilation of vessels; thinner than in arteries; muscle innervated by autonomic fibers Tunica Adventitia – Provides flexible support that resists collapse or injury; thinner than in arteries; thicker than tunica media Tunica Adventitia – Provides flexible support that resists collapse or injury; thinner than in arteries; thicker than tunica media

Cappillaries Tunica Intima – Makes up the entire wall of the capillary; thinness permits transport across vessel wall Tunica Intima – Makes up the entire wall of the capillary; thinness permits transport across vessel wall Tunica Media – Absent Tunica Media – Absent Tunica Adventitia – Absent Tunica Adventitia – Absent

Micrograph of Blood Vessel Structure This light micrograph of a cross section of tissue contains an artery (left) and a vein (right). Note the prominence of the smooth muscle (tunica media) in the artery compared to the vein

Function of Capillaries Most important vessels functionally Most important vessels functionally Very tiny (on average, only 1mm long) Very tiny (on average, only 1mm long) According to one estimate, 1 cubic cm of muscle tissue contains more than 100,000 capillaries According to one estimate, 1 cubic cm of muscle tissue contains more than 100,000 capillaries Primary exchange vessels Primary exchange vessels The small size and large number ensures slow blood flow The small size and large number ensures slow blood flow

Microcirculation

Function of Arteries Arteries serve mainly as “distributors,” carrying blood to the arterioles, which then carry blood to the capillaries Arteries serve mainly as “distributors,” carrying blood to the arterioles, which then carry blood to the capillaries Arterioles are important in maintaining normal blood pressure and circulation (resistance vessels) Arterioles are important in maintaining normal blood pressure and circulation (resistance vessels) Precapillary sphincters function as valves regulating blood flow into the capillaries Precapillary sphincters function as valves regulating blood flow into the capillaries

Function of Veins Function both as collectors and reservoir vessels (ability to hold blood) Function both as collectors and reservoir vessels (ability to hold blood) Capacitance -- Great ability to strech, therefore, they can hold large amounts of blood with almost no change in blood pressure Capacitance -- Great ability to strech, therefore, they can hold large amounts of blood with almost no change in blood pressure Valves maintain the one way flow of blood Valves maintain the one way flow of blood

The reservoir function of veins Pooled blood is moved toward the heart as valves are forced open by pressure from volume of blood from below. Closure of valves prevents backflow. Pooled blood is moved toward the heart as valves are forced open by pressure from volume of blood from below. Closure of valves prevents backflow.

Circulatory Routes Systemic Circulation – blood is pumped from the left side of the heart to all the tissues of the body Systemic Circulation – blood is pumped from the left side of the heart to all the tissues of the body Pulmonary Circulation – blood is pumped from the right side of the heart to the gas exchange tissues of the lungs Pulmonary Circulation – blood is pumped from the right side of the heart to the gas exchange tissues of the lungs

Blood Flow Through the Circulatory System

Main Arteries of the Body

The Aorta

Arteries of the Head and Neck

Arteries at the Base of the Brain

Major Arteries of the Upper Extremity

Major Arteries of the Loser Extremity

General Principles About Veins Veins branch into vessels of increasing size Veins branch into vessels of increasing size Vessels vary considerable in size and location from person to person Vessels vary considerable in size and location from person to person Veins found deep in the body are called deep veins and those found near the surface are called superficial veins Veins found deep in the body are called deep veins and those found near the surface are called superficial veins

Major Veins of the Body

Major Veins of the Head and Neck

Major Veins of the Upper Extremity

Principal Veins of the Thorax

Inferior Vena Cava and its Abdominopelvic Tributaries

Disorders of the Cardiovascular System

Mitral Valve Prolapse

Coronary Bypass

Partial Blockage of Artery in Atherosclerosis

Balloon Angioplasty

Varicose Veins