Chapter 8 Respiration and Circulation Solutions

Open circulation

Closed circulation

1. In open circulation, blood flows through large open spaces and channels called lacunae and haemocoels among the tissues.

1. In closed circulation, blood flows through a network of blood vessels all over the body.

2. Tissues are in direct contact with the blood.

2. Blood does not come in direct contact with tissue.

3. Blood flows with low pressure and usually does not contain any respiratory pigment like haemoglobin.

3. Blood flows with high pressure and contains respiratory pigment like haemoglobin.

4. Exchange of material takes place directly between blood and cells or tissues of the body.

4. Exchange of material takes place between blood and body tissues through an intermediate fluid called lymph.

5. Volume of blood flowing through a tissue cannot be controlled as blood flows out in open space.

5. Volume of blood can be regulated by the contraction and relaxation of the smooth muscles of the blood vessels.

6. Open circulatory system is found in arthropods and some molluscs.

6. Closed circulatory system is found in annelids, echinoderms and all vertebrates.

Arteries

Veins

1. The blood vessels that arise from the heart and carry blood away from heart are called arteries.

1. The blood vessels that bring blood to the heart are called veins.

2. Arteries are thick walled blood vessels, situated in deep layers in the body.

2. Veins cure thin walled blood vessels, situated superficially in the body.

3. Arteries do not have valves.

3. Veins have valves.

4. Tunica adventitia, the outermost layer of arteries is thick and elastic.

4. Tunica externa, the outermost layer of veins is thin.

5. Tunica media is very thick and contain elastic fibres.

5. Tunica media is thin layer and contain involuntary muscle fibres.

6. The lumen of arteries is small.

6. The lumen of the veins is very spacious.

7. With the exception of pulmonary arteries, all other arteries carry oxygenated blood.

7. With the exception of pulmonary veins, all other veins carry deoxygenated blood.

8. Blood in the arteries show high blood pressure.

8. Blood in the veins show lesser blood pressure.

Blood

Lymph

1. Contains blood plasma with proteins and all three types of blood cells namely RBCs, WBCs and blood platelets.

1. Contains blood plasma without blood proteins, RBCs and platelets and contains lymphocytes.

2. Red in colour due to presence of RBCs.

2. Light yellow in colour and does not contain RBCs.

3. Carries oxygen in the body.

3. Does not carry oxygen.

4. The flow of blood in blood vessels is fast.

4. The flow of lymph in lymph capillaries is slow.

5. Lymphocytes are present.

5. Lymphocytes are present, more in number than those present in the blood.

Blood capillary

Lymph capillary

1. Reddish, easy to observe.

1. Colourless, difficult to observe.

2. Joined to arterioles at one end and to venules at another end.

2. Blind (closed at the tip).

3. Narrower than lymph capillaries.

3. Wider than blood capillaries.

4. Wall consists of normal endothelium and basement membrane.

4. Wall consists of thin endothelium and poorly developed basement membrane.

5. Contains red blood.

5. Contains colourless lymph.

6. Have relatively high pressure.

6. Have relatively low pressure.

Intrinsic process

Extrinsic process

1. The intrinsic pathway requires only clotting factors found within the blood itself – in particular, clotting factor XII (Hageman factor) from the platelets.

1. The extrinsic pathway is initiated by factors external to the blood, in the tissues adjacent to damaged blood vessel – in particular, it is initiated by clotting factor III, thromoboplastin from the damaged tissues.

2. It is a longer, multistep process and it takes a little longer for the blood to clot by this mechanism.

2. It involves fewer chemical reaction steps and produce a clot a little more quickly than the intrinsic pathway.