Chapter 15

Cardiovascular System

Organs

• Heart - begins beating in the 4th week of development.– Pumps 7,000 liters of blood each day.– Contracts 2.5 billion times in a lifetime.

• Closed Vessel System– Arteries - carry blood away from the heart.– Veins - carry blood toward the heart.– Capillaries - attach arteries and veins.

Function

• Circulates blood to every cell in the body and removes waste.

The Heart

• Location and Size– Size of a man’s fist (14

cm long and 9 cm wide)– Lies within the

mediastinum - behind sternum (rests on diaphragm).

– 2/3 of the heart is on the left side of the body.

– Apex is the lower, left “point” of the heart.

• Stethoscope is placed here to count the beats.

The Heart • Coverings

– Pericardium - sac around the heart - loose-fitting• Fibrous - tough white outer

covering, • Serous parietal - smooth

lining of the fibrous sac.– Epicardium - covers surface

of the heart - smooth• Also called serous visceral

pericardium– Pericardial space - area

between pericardium and epicardium• Contains fluid - pericardial

fluid• Lubricates beating heart• Pericarditis - inflammation

of pericardium due to infection - linings stick together, very painful.

The Structure of the Heart

• The wall of the heart:– Epicardium – reduces

friction.– Myocardium – thick

contractile middle layer, high in mitochondria.

– Endocardium – delicate inner layer.

The Structure of the Heart Continued

• Cavities– Upper – atria– Lower – ventricles

• Larger and thicker walled

• Carry heavier pumping burden

• Left is thickest – has to pump blood to all parts of the body

The Structure of the Heart Continued

• Valves and Openings• Blood flows in one direction.

– Cuspid valves – between cavities.

• Bicuspid (mitral) valve - left cavities.

• Tricuspid valve - right cavities.

– The semi-lunar valve moves blood out of the heart to the aorta and pulmonary artery.

– A murmur is an abnormal sound that identifies the leakage of blood through valves in the wrong direction.

The Structure of the Heart Continued

• Blood Supply– Ventricles get blood from the right and left

coronary arteries. – Atria get blood from the small branch

coronary artery. – Anastomosis is branching of the main arteries

“detours”– Myocardial infarction - death of the heart

muscles due to a clot (heart attack).

Blood Vessels

• Structure– Outer – fibrous tissue,

keeps firm– Middle – muscle,

constriction, and dilation. – Inner – endothelium -

capillaries

Blood Vessels Continued

• Function– Transportation of nutrients to cells

• Capillaries perform this function• Arteries = distributors arterioles capillaries

venules veins • Veins = carry and pool blood

Blood Vessels Continued

• Main Blood Vessels– ascending aorta– aortic arch– subclavian– common carotid – common iliac

Ascending

Aorta

Blood Vessels Continued

Blood Vessels Continued

• Portal Circulation– Organs that do not pour blood into inferior

vena cava.– Blood sent to the liver by the portal vein.

Blood Vessels Continued

• Fetal Circulation– Gets oxygen and food from mother, not own

lungs and digestive tract.– Additional vessels

• Umbilical arteries (2) – carry fetal blood to placenta

• Placenta – exchanges oxygen and other substances between mother and fetus

• Umbilical vein – returns oxygenated blood to liver of fetus

• Foramen ovale – opening between right and left atria bypass lungs, closes with first breath.

Shed at birth