1. The lymphatic system is part of the circulatory system, comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph directionally towards the heart.
2. The lymphatic system consist of
1. lymophatic vessels
2. lymphatic capillaries
3. lymph nodes
4. spleen
5. thymus

Haemophilia

1. Haemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation.
2. As a result, minor injuries and internal bleeding can results in death owing to excessive loss of blood.

Thrombosis

1. Thrombosis is the formation of a blood clot (thrombus) inside a blood vessel, obstructing the flow of blood through the circulatory system.
2. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss.
3. However, when a blood vessel is not injured, blood clots may form in the body under certain conditions such as a defective blood vessel causes the blood clotting factors to be released into the blood.
4. When a blood clot can cause obstruction to the blood flow.
5. If clotting occurs in the coronary artery, it is called coronary thrombosis. Coronary thrombosis can cause a heart attack.
6. If it occurs in the artery in the brain, it will cause a stroke.
7. Thrombosis may also cause atherosclerosis, which is the deposition of fat and cholesterol on the walls of arteries.

1. When a blood vessel is damaged, platelets will gather around the wound and coagulate.
2. At the same time, an enzyme called thrombokinase will be released.
3. Thrombokinase will convert the inactive prothrombin to the active thrombin.
4. The thrombin will then catalyses the soluble fibrinogen to the insoluble fibrin.
5. Fibrin will form a fibrous network to trap the blood cells and form the blood clot.

Hemostasis 

1. Hemostasis is a process which causes bleeding to stop and keep blood within a damaged blood vessel. It is the first stage of wound healing.
2. Blood clotting is an important part of hemostasis, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel.

Significant of Blood Clotting

1. Pressure is how much force exerted on one unit area of a surface.
2. Blood pressure is the pressure exerted by the blood on the walls of the blood vessels.
3. Sometime, it is also called the arterial blood pressure as it is the pressure in the arteries.

Normal Blood Pressure

1. When measuring blood pressure, we measure the
1. systolic pressure (highest pressure measured in the aorta and the arteries during ventricular contraction)
2. diastolic pressure (lowest pressure measured after the contraction of the heart while the chambers of the heart refill with blood.)
2. For an adult, the normal systolic pressure is 120 mm Hg whereas the diastolic pressure is 80 mm Hg.
3. However, blood pressure may varies throughout the day.

Factors Affecting Blood Pressure

1. Blood pressure can be affected by the following factors:
1. Rate of heart beat
   Higher heart rate, higher blood pressure.
2. Volume of blood in the body
   Bigger volume, higher blood pressure.
3. Rate and volume of blood flow
   Higher rate and volume of blood flow, higher rate of heart pumping, higher blood pressure.
4. Resistance of blood vessels
   Higher resistance (smaller blood vessels, rough blood vessel wall), higher blood pressure. 

Regulation of Blood Pressure

1. The circulation of blood in human is due to the pumping of the heart.
2. The cardiac muscles contract to produce heartbeat which pumps the blood to the whole body.

The Cardiac Cycle

( Image by Madhero88 shared under the Creative Commons Attribution 3.0 Unported license. )

1. The heartbeat is initiated by the sinoatrial node (also called the SAN or pacemaker) .
2. The SAN consists of specialised cardiac muscle fibres that generates nerve impulses.
3. From the SAN, the electrical impulses spread to the atrioventricular node (AVN) located at the base of the right atrium (See image above).
4. Special muscle fibres called His Bundle and the Purkinje fibres then sends the impulses to the ventricles and then stimulates both ventricles to contract simultaneously and pumps the blood out of the heart.

Contraction of the Skeletal Muscles Around Veins

1. The blood pressure in the vein is low and hence make it hard for the blood to flow back to the heart.
2. Therefore, there are skeletal muscles presence around the veins to help blood circulation.
3. When the skeletal muscles contract, blood is forced to move along the veins.
4. The valves in the veins prevent the back flow of the blood and hence direct the blood back to the heart.

Structure

Contraction of Heart

1. The wall of the heart is made up of cardiac muscle, which is myogenic.
2. Myogenic contraction is the contraction of muscle without nervous stimulation.
3. Contraction of heart is started by sinoatrial node (also known as the pacemaker)

1. Three types of blood vessels
1. artery
2. vein
3. capillary
2. Artery: Carries blood from the heart to other parts of the body.
3. Vein: Carries blood from other parts of the body back to the heart.
4. The arteries divides into smaller branches called arterioles.
5. The veins receives blood from smaller branches called venules.
6. Capillaries: Blood vessels connect the arterioles and venules.
7. Around the capillaries are body cells.

	Artery	Vein	Capillary
Main function	Carries oxygenated blood from the to ather parts of the body	Carries dexoygenated blood from the other parts of the body to the heart.	Connect arterioles and venules. Allows exchange of materials between the blood and the cells.
Blood	Carries oxygenated blood except pulmonary artery	Carries deoxygenated blood except pulmonary vein
Valves	No valves except pulmonary artery	All have valves except pulmonary vein	No valves
Blood pressure	High	Low	Very low
Blood flow	Rapid	Slow	Very slow
Diagram
Wall	Thick muscular wall	Thin wall and less muscular	Thin wall, only one-cell thick
Size of lumen	Small lumen	Big lumen	Very small lumen
Branches	Arterioles	Venules	No