Syllabus Point:
In animals, the transport of materials within the internal environment for exchange with cells is facilitated by the structure of open and closed circulatory systems according to the different metabolic requirements of organisms and differing environments.
Learning Objectives
- To be able to explain the principal functions of animal circulatory systems
- To understand and be able to explain the difference between closed and open circulatory systems
- To be able to identify and explain the function of the major organs or parts of circulatory sytems from diagrams
Why circulate?
- The circulatory system is used to transport water, nutrients and gases through the body.
- When animals are only a few cell layers thick - they can transport some substances via simple diffusion.
- For larger, more complex organisms, bulk flow is the only way to transport substances.
- In endotherms, the circulatory system also helps to distribute heat and maintain temperature.
- Finally, in complex organisms, hormones are circulated via circulatory systems.
Essential Features in Animal Circulatory Systems
- A circulatory fluid in which materials are transported, such as blood.
- A system of vessels or spaces for the fluid to move throughout the body.
- A pump, such as the heart, that pushes the circulatory fluid through the vessels or spaces.
1. Circulatory Fluid:
In vertebrates the fluid that circulates within the body is called blood.
In invertebrates, this fluid is known as hemolymph.
Blood contains:
Hemolymph contains:
In invertebrates, this fluid is known as hemolymph.
Blood contains:
- Plasma. Which is the liquid portion containing:
- Water
- Proteins
- Salts
- Lipids
- Glucose
- Red Blood Cells - Responsible for carrying gases. Contain lots of Hemoglobin (a protein responsible for distributing oxygen and carbon dioxide).
- White Blood Cells - Responsible for immune-response.
- Cell fragments called Platelets - Responsible for blood clotting.
- READ and take notes on Page 267 Table 11.1
Hemolymph contains:
- Mostly water, as well as...
- Ions, carbohydrates, lipids, glycerol, amino acids, hormones.
- Can contain pigments, but usually quite bland (tinged with yellow or green).
Required Reading: Pages 266 - 269
Question Set 11.1 on Page 269.
For extra detail watch the videos at: https://www.khanacademy.org/science/health-and-medicine/advanced-hematologic-system/hematologic-system-introduction/v/what-s-inside-of-blood
Question Set 11.1 on Page 269.
For extra detail watch the videos at: https://www.khanacademy.org/science/health-and-medicine/advanced-hematologic-system/hematologic-system-introduction/v/what-s-inside-of-blood
2. The blood vessels (or spaces for fluid movement)
In a Closed Circulatory System...
- Circulatory fluid (blood) is confined to a series of paths or vessels.
- Fluid movement through these paths are driven by a pump (heart), so all vessels connect to this organ.
- Three main types of Circulatory Vessels:
- Arteries: take blood away from the heart. Have very thick walls. They stretch when the blood is pushed from the heart and then recoil to push the blood on further.
- Veins: carry blood back to the heart. Have valves to keep blood flowing in one direction under low pressure.
- Capillaries: vessels found between veins and arteries.Walls are only one cell thick to allow for diffusion. These vessels are about the same diameter as a red blood cell so that the cell membranes touch, allowing for diffusion.
In an open circulatory system...
- Some animals have a heart and a few vessels to pump circulatory fluid, but it is not fully contained and instead washes freely over internal organs.
- No formal arteries, capillaries or veins.
- This is an open-circulatory system.
- E.g. Some insects have a series of small hearts that pump fluid from the back to the front of the animal.
- This is not as efficient as a closed system and so the animals which have an open circulatory system tend to be smaller.
Why is a closed circulatory system more efficient?
- The blood transfers faster in the closed system, thus oxygen, nutritients, and wastes transport fast also (better for animals with a faster metabolism).
- Specialized cells help carry nutrients more effectively.
- The blood and the tissue fluid are distinguished easily - keeping conditions in tissues more stable.
3. The Circulatory Pump (heart)
Invertebrates have tubular hearts with holes (ostia) in the sides to expel hemolymph (circulatory fluid) into the hemocoel (body cavity)
Vertebrate hearts can be 2 chambered, 3 chambered or 4 chambered.
2-Chambered Hearts:
The heart consists of one atrium and one ventricle.
Fish have two chambered hearts, this means they do not have double circulation (single circulation).
3-Chambered Heart:
The heart consists of two atriums and one ventricle.
This type is more advanced than that of fish, but not as advanced as mammals.
The ventricle has an incomplete partition which divides it into 2 sub chambers.
Animals with 3 chambered hearts have incomplete double circulation.
4-Chambered Heart:
Two atrium (atria) and two ventricles.
Complete double circulation (no mixing of oxygenated and deoxygenated blood)
BENEFIT: Purely oxygenated blood is sent to body cells as opposed to mixed blood.
Vertebrate hearts can be 2 chambered, 3 chambered or 4 chambered.
2-Chambered Hearts:
The heart consists of one atrium and one ventricle.
Fish have two chambered hearts, this means they do not have double circulation (single circulation).
- The deoxygenated blood enters the atrium.
- It is pumped into the ventricle
- The ventricle pumps the blood out
- The blood goes towards the gills
3-Chambered Heart:
The heart consists of two atriums and one ventricle.
This type is more advanced than that of fish, but not as advanced as mammals.
The ventricle has an incomplete partition which divides it into 2 sub chambers.
Animals with 3 chambered hearts have incomplete double circulation.
- Deoxygenated blood enters the right atrium
- Moves into the right sub chamber of the ventricle.
- Due to incomplete separation it leaks into and fills the left ventricle.
- The blood then moves up from the ventricle into the lungs for oxygenation.
- This comes back down and fills the third chamber, shutting it off.
- The blood then moves into the left ventricle and from there the rest of the body.
4-Chambered Heart:
Two atrium (atria) and two ventricles.
Complete double circulation (no mixing of oxygenated and deoxygenated blood)
BENEFIT: Purely oxygenated blood is sent to body cells as opposed to mixed blood.
- The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle.
- The right ventricle pumps the oxygen-poor blood to the lungs.
- The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle.
- The left ventricle pumps the oxygen-rich blood to the body.
Single circulation Incomplete Double Circulation Complete Double Circulation
The Lymphatic System
The lymphatic system works very closely with the circulatory system and can also be considered a means of substance transport.
What is the function of the lymphatic system?
What is the lymphatic system?
The lymphatic system consists of...
What is the function of the lymphatic system?
- It is responsible for the removal of interstitial fluid from tissues.
- It absorbs and transports fatty acids and fats as chyle from the digestive system
- It transports white blood cells to and from the lymph nodes into the bones
- The lymph transports antigen-presenting cells, such as dendritic cells, to the lymph nodes where an immune response is stimulated.
What is the lymphatic system?
The lymphatic system consists of...
- Adenoids
- Tonsils
- Lymphatic Vessels
- Thymus Gland
- Lymphatic Ducts
- Lymph nodes
- Spleen
- Peyer's patches (in small intestine)
- Appendix
- Bone Marrow
- Interstitial Fluid
- The lymphatic system can be thought of as a drainage system.
- As blood circulates, blood plasma leaks into tissues through the capillaries.
- There is more fluid entering the tissue via capillaries than there is leaving the tissue via capillaries.
- The portion of blood plasma that escapes into the tissue and is left behind is called interstitial fluid.
- It contains oxygen, glucose, amino acids, and other nutrients needed by tissue cells.
- Although most of this fluid seeps back into the bloodstream, some is left behind.
- The lymphatic system removes this fluid and these leftover materials from tissues.
- It returns the fluid via the lymphatic vessels to the bloodstream.
How the drainage happens:
- The interstitial fluid and proteins in the tissue passes into tiny lymphatic capillaries.
- The fluid is now called lymph, and drains into larger vessels, until they reach ducts.
- The right lymphatic duct, drains the upper right portion of the body, the thoracic duct, drains the rest of the body.
- Lymph is drained from these ducts into lymphatic veins.
- Lymph is transported along the system of vessels by muscle contractions
- Valves prevent lymph from flowing backward.
Now you should...
Watch the clips above. (Ignore the immune system aspect of the first clip)
Required Reading: Chapter 12
Complete Question Sets from Chapter 12
WACE Study Guide pp.132 (5.4 Circulatory Systems)
Required Reading: Chapter 12
Complete Question Sets from Chapter 12
WACE Study Guide pp.132 (5.4 Circulatory Systems)
chpt_11_answers.pdf | |
File Size: | 1087 kb |
File Type: |