1. 6.2 The blood system
Essential idea: The blood system continuously transports substances to cells and simultaneously collects waste products.

2. Understandings:
Arteries convey blood at high pressure from the ventricles to the tissues of the body.
Arteries have muscle cells and elastic fibres in their walls.
The muscle and elastic fibres assist in maintaining blood pressure between pump cycles.
Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood inthe capillary.
Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.
Valves in veins and the heart ensure circulation of blood by preventing backflow.
There is a separate circulation for the lungs.
The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
The sinoatrial node acts as a pacemaker.
The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles.
The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
Epinephrine increases the heart rate to prepare for vigorous physical activity.

3. Applications and skills:
Application: William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.
Application: Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
Application: Causes and consequences of occlusion of the coronary arteries.
Skill: Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
Skill: Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure.

4. Warm Up How does blood move around your body?
What path does it follow?
TODAY’S FOCUS – HEART AND BLOOD VESSELS
What are the major structures of the circulatory system?

5. body
Aorta
lungs
Pulmonary Artery
Vena Cava
Pulmonary Vein
Right Atrium
Left Atrium
Right Ventricle
Left Ventricle
blood flow

6. beating heart pulmonary artery (to left lung) aorta superior vena cava
left atrium
pulmonary artery (to left lung)
semilunar valves
pulmonary veins (from left lung)
atrioventricular valve
left ventricle
thicker muscle of left ventricle
descending aorta (to lower body)
right ventricle
inferior vena cava
superior vena cava
pulmonary artery (to right lung)
pulmonary veins (from right lung)
right atrium
beating heart
Figure taken from Biology, Life on Earth 10th Ed. Pearson

7. How Does The Vertebrate Heart Work?
The cardiac cycle
Oxygenated blood is pumped to the body
Deoxygenated blood is pumped to the lungs
Blood fills the atria and begins to flow passively into the ventricles
Deoxygenated blood from the body enters the right ventricle
Oxygenated blood from the lungs enters the left ventricle
Atria contract, forcing blood into the ventricles
Then the ventricles contract, forcing blood through the arteries to the lungs and the rest of the body
The cycle ends as the heart relaxes
Fig. 20-4

8. How Does The Vertebrate Heart Work?
The heart’s pacemaker and its connections
The sinoatrial node electrical signal starts the atrial contraction
Unexcitable tissue separates the atria and ventricles
AV node
The signal spreads, causing the atria to contract
excitable fibers
The atrioventricular node transmits the signal to the ventricles with a slight delay
The signal travels to the base of the ventricles
Excitable fibers transmit the signals to ventricular cardiac muscle, causing contraction from the base upwards

9. lung capillaries atria ventricle body capillaries
Figure taken from Biology, Life on Earth 10th Ed. Pearson

10. Anatomy of Circulatory Systems
arteries - vessels that carry blood away from the heart
capillaries - smallest blood vessels (microscopic) penetrate tissues
extracellular fluid - fluid surrounding capillaries; dissolved substances in the blood are exchanged
veins – vessels that move blood back toward the heart

11. capillary network arteriole venule cross section capillary valve
smooth muscle
connective tissue
artery
vein
Figure taken from Biology, Life on Earth 10th Ed. Pearson

12. jugular vein
aorta
superior vena cava
carotid artery
lung capillaries
pulmonary artery
heart
kidney
femoral vein
intestine
inferior vena cava
liver
femoral artery

13. circulatory systems transport…
oxygen from the lungs or gills to the tissues
carbon dioxide from the tissues to the lungs or gills
nutrients from the digestive system to the tissues
waste products & toxins to the liver & kidney for excretion
hormones from the glands and organs that produce them to the tissues on which they act