Download Grade 11 College Biology – Unit 3

Grade 10 Applied Science - Biology
Human Circulatory System
The CIRCULATORY SYSTEM is the transport system of the body. It has FOUR functions:
 Transport of oxygen and carbon dioxide
 Distribution of nutrients and transport of wastes
 Maintenance of body temperature
 Circulation of hormones
The system consists of THREE general components:
 FLUID in which materials are transported
 System of BLOOD VESSELS or spaces throughout the body in which the fluid moves
 A pump, the HEART, that pushes the fluid through the open spaces.
The heart and blood vessels are commonly called the CARDIOVASCULAR SYSTEM
The circulatory system is a complex network of tissues and organs throughout your body; yet, no cell is
further than TWO cells away from a blood vessel. Thus, there are 96,000 km of blood vessels in your
body to nourish your 100 trillion cells. The heart is no larger than your fist with of mass of about 300
grams; yet, the heart beats about 72 times/minute.
Every minute, 5 L of blood cycles from your heart to the lungs, picks up oxygen and returns to the heart.
Then, the heart pumps the oxygen-enriched blood and nutrients to the tissues of your body.
Why is oxygen so important to
your life?
The circulatory system is two
systems (see the attached
diagram).
 PULMONARY CIRCUIT –
The right side of the heart
pumps blood to the lungs
and returns oxygenatedblood to the left side of the
heart
 SYSTEMIC CIRCUIT –
The left side of the heart
that pumps the oxygenate
blood to all parts of the
body and carries
deoxygenated blood back
to the heart.
HEART STRUCTURE
The left and right sides of the heart are separated by a wall of muscle called the SEPTUM
Each side (or pump) consists of a thin-walled ATRIUM and a thick-walled VENTRICLE. The atria
receives blood for the veins and pumps it into the ventricles. When the heart muscles contract, a valve of
the heart prevents blood from flowing backwards.
HEART PHYTHMS, SOUNDS and PRESSURE
The heart has two specialized bundles of nerves that control its beating.
 SINOATRIAL (SA) NODE – acts as a pacemaker
 ATRIOVENTRICULAR (AV) NODE – passes the nerve impulses to the ventricles to cause them
to contract in unison.
The heart sound is the closing of the valves. When the atria are relaxed (called DIASTOLE), they fill with
blood. As the atria push blood into the ventricles, the ventricles contract to force blood into the arteries.
This contraction is SYSTOLE. The increase in pressure forces the AV valves to close…creates the LUBB
sound. As the ventricles relax, the pressure inside decreases closing the semilunar valves and
preventing a backward flow of blood. This closing is the DUBB sound.
BLOOD PRESSURE is the pressure exerted on the walls of the arteries when the ventricles of the heart
contract. Blood pressure is measured in mm Hg.
Blood pressure is measured with a SPHYGMOMANOMETER. A stethoscope is used to listen to the
sound of blood entering the artery as air is slowly released from the sphygmomanometer. The pressure
on the gauge of the sphygmomanometer when the sound is first heard is the SYSTOLIC BLOOD
PRESSURE. As the cuff of the sphygmomanometer is deflated, the sound disappears. This is the
DIASTOLIC BLOOD PRESSURE. If your blood pressure is too high, it put stress on the walls of the
arteries which may result in a stroke or heart attack. High blood pressure is called HYPERTENSION.
Low blood pressure is HYPOTENSION can lead to dizziness, blurred vision or loss of consciousness.
BLOOD VESSELS
 ARTERIES carry blood away from the heart
 The AORTA is the largest artery of the body and closest to the heart
 From the arteries, blood flows into smaller blood vessels called ARTERIOLES, and then, smaller
vessels called CAPILLARIES.
 As the capillaries merge, they become larger vessels called VENULES which merge into VEINS.
The veins have valves that only open in one direction to allow blood to flow only to the heart.
Contractions of the muscles surrounding the veins also help blood to flow to the heart
BLOOD COMPONENTS (Use Page 89 in the textbook to complete this table)
Component
Description
Function
Plasma
Red Blood
Cells
White Blood
Cells
Platelets
Do Questions 1-5 on Page 93 in the textbook