The Circulatory System37-1BIO 1004Flora

Functions of Circulatory System Small Organisms vs. large organisms

(multi-cellular) Humans and other vertebrates have

closed circulatory systems Blood is enclosed in blood vessels

Human CS consists of blood vessels, heart, and blood that travels through them

The Heart Located in the center of the thoracic

cavity Surrounding the heart is protective

tissue called pericardium The thick layer of muscle that makes up

the heart is called myocardium The contraction of the myocardium is what

forces blood through the blood vessels

The Heart Cont. Dividing the right side of the heart from the left

side of the heart is a barrier called the septum Prevents the mixing of oxygen poor and oxygen

rich blood On each side of the septum are two chambers

Atrium – upper chamber that receives the blood Ventricle – pumps blood out of the heart

* The heart contains two atria and two ventricles

The Heart

Circulation Through the Body Heart functions as two separate pumps Right side of the heart pumps blood

from the heart to the lungs – called pulmonary circulation

Oxygen rich blood then flows into the left side of the heart and is pumped to the rest of the body – called systemic circulation

Circulation

Circulation Through the HeartThe Process Blood enters through right and left atria As heart contracts, blood flows into the

ventricles and then to body or lungs Valves – prevent blood from having a reverse

flow When ventricles contract, the valves close

preventing blood flow back into the atria There are also valves at the exits of the

ventricles that prevent blood from flowing back into the heart

Heart Beat The contraction of the heart begins in a

small group of cardiac muscle cells called the sinoatrial node/SA Node (located in right atrium)

Called the pacemaker because these cells set the pace for the heart by contracting

This signal is picked up by fibers called the atrioventricular node (AV node) and this allows the ventricles to contract

Blood Vessels Blood leaving the left side of the heart is

oxygen rich The aorta carries oxygen rich blood from

the heart to the body 3 types of blood vessels

Arteries Capillaries veins

Blood Vessels Arteries – large vessels that carry blood from

the heart to tissues in the body Except for pulmonary – all arteries carry

oxygen rich blood Arteries have thick walls that allow for the high

pressures of blood passing through these canals

Capillaries – smallest blood vessels Nutrient transport, oxygen transport to tissues,

and removal of waste products is done by the capillaries

Blood Vessels Cont. Veins – carry oxygen poor blood back to

the heart Thick walls to withstand pressure Lack of exercise will weaken vein walls

causing them to stretch, thus weakening the valves causing blood to pool in the veins Known as varicose veins

Blood Pressure Force of blood on the artery walls is known as

blood pressure Pressure is measured with a sphygmomanometer Systolic pressure – 1st # - force felt in arteries

when ventricles contract Diastolic pressure – force felt in arteries when

ventricles contract Kidneys also help regulate blood pressure

Hormones cause kidneys to remove more water when blood pressure is too high

Reduces volume and reduces pressure

Diseases Atherosclerosis – fatty deposits/plaque build

up on the inner walls of the arteries Often builds up in coronary arteries which

bring oxygen rich blood back to heart, and then the heart cells will die from lack of oxygen

Blood clots can break free and travel to the brain and then cause blockage – known as a stroke Brain cells die from lack of oxygen

Diseases Cont. High blood pressure – known as

hypertension Weakens and damages heart and blood

vessels Increases risk of heart attack and stroke

Diet Exercise NO smoking Low saturated fat Watch cholesterol Obesity causes heart to contract harder,

thus wearing out heart faster