respiratory and circulatory systems · respiratory and circulatory systems chapter 30 . the heart...
TRANSCRIPT
Respiratory and Circulatory Systems
Chapter 30
THE HEART AND CIRCULATION 30.3
Key Concept
• The heart is a muscular pump that moves the blood through two pathways
Heart Structure
• Made of cardiac tissue
• Efficient pump
• Works continuously without tiring
NORMAL HUMAN HEART
Heart Structure
• Four chambers: – 2 atria – 2 ventricles
• Valves prevent the backflow of blood
• Muscles squeeze the chambers in a powerful pumping action
Heart Beat
• Consists of 2 contractions: – SA node, or
pacemaker, stimulates atria to contract
– AV node stimulates ventricles to contract
Blood Flow
• Blood flows through the heart in a specific pathway
Blood Flow
• Oxygen-poor blood enters right atrium, then right ventricle
• Right ventricle pumps blood to lungs
• Oxygen-rich blood from lungs enters left atrium, then left ventricle
• Left ventricle pumps blood to body
Pulmonary Circulation
• Occurs between the heart and lungs – oxygen-poor blood
enters lungs – excess carbon dioxide
and water expelled
– blood picks up oxygen – oxygen-rich blood
returns to heart
Systemic Circulation
• Occurs between the heart and the rest of the body – oxygen-rich blood goes to
organs, extremities
– oxygen-poor blood returns to heart
• The two pathways help maintain a stable body temperature
BLOOD VESSELS AND TRANSPORT 30.4
Key Concept
• The circulatory system transports materials throughout the body
Blood Vessels
• Arteries carry blood away from the heart – blood under great
pressure
– thicker, more muscular walls
Blood Vessels
• Veins carry blood back to the heart – blood under less pressure
– thinner walls, larger diameter
– valves prevent backflow
Blood Vessels
• Capillaries move blood between veins, arteries, and cells.
Blood Pressure
• A measure of the force of blood pushing against artery walls – systolic pressure: left ventricle contracts
– diastolic pressure: left ventricle relaxes
• High blood pressure can precede a heart attack or stroke
Blood Pressure
Circulatory Disease
• Some choices lead to an increased risk of circulatory diseases. – smoking – long-term stress – excessive weight – lack of exercise – diet low in fruits
and vegetables, high in saturated fats
Circulatory Disease
• Affects mainly the heart and arteries – artery walls become thick and inflexible
– plaque blocks blood flow in arteries