1. Blood Vessels and the Heart

2. Blood Vessels Three Types Arteries: carry blood away from the heart
Thick walled, smaller vessels are called arterioles
Veins: carry blood towards the heart
Thin walled, smaller vessels are called venules
Contains valves
Capillaries: connect the arteries to the veins
Smallest of the blood vessels
RBC’s travel single file through capillaries
Branch like system to increase surface area for diffusion
Site of gas exchange

4. Arterial System Transports blood under pressure.
Blood moves in a pulse-like wave.
Contraction & relaxation of arterioles
is the major determinant of the
overall blood pressure.

5. Venous System
Thinner walls, larger diameters & less muscle than arteries.
Contains 70% of total blood volume.
Most veins work against gravity.
Valves allow one-way flow.
Contraction of skeletal muscles
pushes blood toward heart.

6. Pathways of Blood Pulmonary Circuit Systemic Circuit
Right side of heart.
Low-pressure system.
Takes deoxygenated blood to the
lungs and back to the heart
Systemic Circuit
Left side of heart.
High-pressure system.
Takes oxygenated blood to the body and returns deoxygenated blood back to the heart

8. Pulmonary Circuit Right atrium receives oxygen-poor blood from:
Superior vena cava.
Inferior vena cava.
Blood flows through the
tricuspid valve or the
right atrioventricular (AV)
valve to the right ventricle.
Blood from
body
Blood from
body

9. Pulmonary Circuit
Blood flows through the pulmonary semi-lunar valve & enters the pulmonary trunk, which divides into the left & right pulmonary arteries.
Divides into capillaries where external gas exchange
(respiration system) occurs.
Oxygenated blood enters the left & right pulmonary veins,
returning blood to the
left atrium.

10. Systemic Circuit
Blood flows through the left AV-valve or bicuspid (mitral) valve to the left ventricle.
Left ventricular walls are two times thicker than in the right ventricle.
Blood travels through the
aortic semi-lunar valve
to the aorta.

11. Systemic Circuit
Aorta branches into smaller systemic arteries, which branch into arterioles & then capillaries.
Internal gas exchange occurs.
Capillaries rejoin as venules & then veins.
Deoxygenated blood returns to the right atrium via the superior & inferior vena cava.

12. Coronary Circulation Delivers oxygenated blood to the heart muscle.
Consists of the left & right coronary artery.