The document provides an overview of the circulatory system, including comparisons of open and closed systems, circulatory pathways in vertebrates, and the composition and functions of the human circulatory system. It details the mechanisms of blood flow, types of blood vessels, and capillary exchange, emphasizing the differences between single-loop and double-loop systems across various organisms. Additionally, it outlines the roles of the heart, arteries, veins, and lymphatic system in circulation and immune response.

1. TOPIC 3:
CIRCULATORY
SYSTEM : PART 1
Learning outcomes:
1. Compare open and closed circulatory system
2. Identify different circulatory pathways in
vertebrates
3. Explain the composition of human circulatory
system and its functions
4. Describe capillary exchange in the tissues
5. Explain the human circulation system
6. Describe blood circulation in human heart
7. Describe the composition and functions of
blood
8. Explain the function of lymphatic system
9. Explain the roles of immune system

2. Circulatory system
Simple
Open
Closed
Single looped
Double looped

3. COMPARE and CONTRAST

4. Circulatory system
Simple
Open
Closed
Single looped
Double looped

5. Simple Circulatory Systems
• Nutrients can diffuse directly
across the cells into cavity.
• No vessels or blood are required
for transportation of nutrients,
waste or gases
• Hydra and planarians are so small
– diffusion provides for the
movement of fluids, gases, and
wastes.
• Nematodes and echinoderms
– movement of the organism
provides for the movement of
the internal fluids.

6. Circulatory system
Simple
Open
Closed
Single looped
Double looped

7. Open Circulatory Systems
• More complex organisms
• A circulatory system involves a heart that
pumps fluid through the organism.
• In an open circulatory system,
1. A tubular heart pumps hemolymph
through channels and cavities
throughout the body.
2. Heart pumps hemolymph through
channels and cavities throughout the
body and into the hemocoel.
3. Hemolymph flow from the heart into
the hemocoel when the heart contract
4. When heart relax: hemolymph drown
though ostia (pore) back into the heart
5. Hemolymph returned to the heart by
passive flow.

8. Circulatory system
Simple
Open
Closed
Single looped
Double looped

9. Closed Circulatory Systems
• A closed circulatory system,
or cardiovascular system,
includes a strong heart and
blood vessels.
• The heart pumps the blood
to the body and receives
the blood returned to the
heart.

10. Closed Circulatory Systems
• There are three types of blood
vessels.
1. Arteries carry blood away from
the heart.
2. Veins return blood to the heart.
3. Capillaries are a fine network of
vessels between the arteries and
capillaries where fluid, gas, and
waste exchange take place.

11. Circulatory system
Simple
Open
Closed
Single looped
Double looped

12. Comparison of Circulatory Pathways in
Vertebrates
There are two
different types of
circulatory pathways in
vertebrate animals.
In fish, the circulatory
pathway is a single
loop with a two-
chambered heart.

13. 1. Blood entering the
heart and collects in
the atrium before
entering ventricle
2. Ventricle pumps
blood to the gills
3. Gases exchange
occurs in gills,
oxygen-rich blood
carry in a vessel to
capillary bed
4. Gases exchange
occurs in body
capillaries, and
oxygen-poor blood
returned to the heart

14. Circulatory system
Simple
Open
Closed
Single looped
Double looped

15. Comparison of Circulatory Pathways
• All other vertebrates have a double circulatory system.
– The systemic circuit includes the blood vessels that carry
blood to the body.
– The pulmonary circuit includes the blood vessels that send
blood to the lungs.
• The double circulatory system helps terrestrial organisms
breathe air.

16. Comparison of Circulatory Pathways
 The amphibian and reptilian
heart has three chambers.
 In amphibians, there are two
atria and a single ventricle.
 In reptiles, the ventricle has a
partial dividing wall (septa).

17. The right circuit
delivers oxygen-poor
blood from the heart
to the lung (also
known as pulmonary
circuit).
In the left circuit,
oxygen-enriched
blood leaves the
heart into capillary
beds in organ and
tissues (also known
as systemic circuit)

18. Comparison of Circulatory Pathways
• The hearts of birds and
mammals have four
chambers.
• The right side pumps to the
pulmonary circuit.
• The left side pumps to the
systemic circuit.

19. Transport in Humans
• The mammalian cardiovascular system
pumps blood through the arteries to the
capillaries.
• After gases, nutrients, and wastes are
exchanged in the capillaries, the blood
returns to the heart in the veins.
Heart  Artery  Arterioles  capillaries
Venules Veins  Heart

20. Blood Vessels: Arteries
• Arteries carry blood (oxygenated blood)
away from the heart.
• The blood pressure is a measure of the
pressure of arterial blood flow.
• The structure of arteries includes muscle
tissue that allows them to expand as the
blood pressure changes.

21. Blood Vessels: Arteries
This flexible arterial
structure includes
smooth muscle and
elastic fibers.
The arterioles are
small arteries that
help regulate blood
pressure.

22. Blood Vessels: Capillaries
• Arteries branch into
microscopic vessels
called capillaries.
• The capillaries have
only a thin layer of
epithelial cells to
facilitate exchange of
substances with the
tissues.

24. Blood Vessels: Venules & Veins
• Venules are vessels that
drain blood from the
capillaries into veins.
• Veins have a larger
diameter than arteries, but
have thinner walls and
move blood under a lower
pressure.

25. Blood Vessels: Venules & Veins
• The flow of blood through
veins is driven by the
contraction of skeletal
muscle.
• The veins also have valves
which prevent backflow of
blood.

26. Capillary Exchange in the Tissues
• Two forces control the
movement of fluid through
the capillary wall.
– The osmotic pressure
drives tissue fluid into
the blood.
– The blood pressure
drives fluid from blood
into the tissues.

27. Capillary Exchange in the Tissues
 A network that distributes
lymph fluid throughout the
body.
 The interstitial fluid bathes the
tissues and is taken up by
lymphatic capillaries.
 The fluid is now called lymph.
 Lymph eventually enters the
lymph nodes.
 In lymph nodes, pathogens
present in lymph encounters
macrophages and lymphocytes

28. Human cardiovascular system
• The human cardiovascular system
is a double circuit.
The Pulmonary Circuits
• The pulmonary circuit circulates
blood to the lungs for gas
exchange.
– The pulmonary arteries carry
blood from the right side of the
heart to the lungs.
– The pulmonary veins returned
oxygenated blood to the left
side of the heart.

29. The Systemic Circuits
• The systemic circuit
distributes the oxygenated
blood to the body.
• Oxygenated blood from the
left side of the heart is
distributed to the body
through the aorta.
• After passing through the
arteries, capillaries and
veins, the vena cava returns
the blood to the right side of
the heart.

30. End part 1
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