The circulatory system has two circuits: the pulmonary circuit and the systemic circuit. The pulmonary circuit pumps deoxygenated blood to the lungs and oxygenated blood back to the heart. The systemic circuit pumps oxygenated blood to the body cells and deoxygenated blood back to the heart. Capillaries connect arteries and veins and are responsible for exchanging substances between blood and tissue fluid. Arteries transport oxygenated blood away from the heart while veins transport deoxygenated blood toward the heart. The human heart has four chambers with two atria receiving blood and two ventricles pumping blood through the pulmonary and systemic circuits.

1. TRANSPORT
SYSTEMS IN
ANIMALS

2. DOUBLE CIRCULATION
• The circulatory systems has two distinct
circuits.
• The pumps of the two circuits serve
different tissues but are combined into a
single organ, the heart.
• The two circuits are called:
1. Pulmonary circuit
2. Systemic circuit

3. DOUBLE CIRCULATION
1. Pulmonary circuit
The heart pumps deoxygenated blood to
the lungs and oxygenated blood back to the
heart.
2. Systemic circuit
The heart pumps oxygenated blood to the
body cells and the deoxygenated blood
back to the heart.

4. DOUBLE CIRCULATION

5. FUNCTIONS OF CAPILLARIES
Capillaries: Connect arteries and veins
–they are structurally suited  they are
responsible for exchange of substances
between the blood in the capillaries &
interstitial tissue fluid

6. FUNCTIONS OF ARTERIES
• Arteries: transports oxygenated
blood except for the pulmonary
artery.
• Main artery is the Aorta which
pumps oxygenated blood away from
heart to the rest of body.
• Other arteries:
• Renal artery (kidney)
• Hepatic artery (liver)

7. FUNCTIONS OF VEINS
• Veins: transports deoxygenated
blood except for the pulmonary
vein.
• Main vein is called the vena cava
which pumps deoxygenated blood
towards the heart from the rest of
the body.
• Other veins:
• Renal vein (kidney)
• Hepatic vein (liver)

9. THE HUMAN CIRCULATORY SYSTEM:
HEART AND ASSOCIATED VESSELS

10. THE HUMAN CIRCULATORY SYSTEM:
HEART AND ASSOCIATED VESSELS
 Mammals have a 4-chambered heart with 2 atria
and 2 ventricles
 The left side of the heart pumps and receives only
oxygen-rich blood,
 while the right side receives and pumps only
oxygen-poor blood
 The mammalian cardiovascular system meets the
body’s continuous demand for O2.
 Blood begins its flow when deoxygenated blood
flow from the body into the right atrium.

11.  Blood then flows from the right atrium into the
right ventricle through the tricuspid valve
 The blood is then pumped into lungs, through the
semilunar valve via the pulmonary artery.
 In the lungs, the blood loads O2 and unloads CO2.
 Oxygen-rich blood from the lungs enters the heart
via the pulmonary vein at the left atrium
 Blood then flows into the left ventricle through the
bicuspid valve.
 This blood is then pumped through semilunar
valve into the aorta with takes blood to the entire
body.

12.  Deoxygenated blood returns to heart through
superior vena cava (blood from head, neck, and
forelimbs) & inferior vena cava (blood from
trunk and hind limbs) which flows into the right
atrium.
 The atrioventricular (AV) valves ( which are
the tricuspid and the bicuspid valves)
separate each atrium & ventricle
 The semilunar valves control blood flow to the
aorta & the pulmonary artery.

13. THE EXTERNAL STRUCTURE:HUMAN
HEART

14. THE INTERNAL STRUCTURE:HUMAN HEART