TOPIC 1.CLASSIFICATION KINGDOM FUNGI
Formation of tissue fluid
At the venous end of the capillary,
blood pressure is low; water potential is also low. The pressure of the tissue
fluid is higher. This forces the tissue fluid back into the capillaries.
Diffusion also helps in the re-entry of tissue fluid to the capillary. However,
some tissue fluid remains within the cells. This later enters the lymphatic
system to form lymph.
The capillaries join to form
venules. Venules join to form veins. The veins transport blood back to the
heart. Veins in the lower part of the body unite to form the inferior vena cava
while veins in the upper part of the body unite to form the superior vena cava.
These two large veins join to form the vena cava which transports blood to the
right auricle of the heart.
Importance of blood circulation
- It enables the transportation of cell requirements such as oxygen and nutrients to all the body tissues.
- It ensures that waste products from the cells are removed in order to prevent accumulation. Accumulation of waste products is harmful to the body.
- Blood circulation is important for the regulation of body temperature. Body heat is transported to all parts of the body through this system.
- Blood circulation also transports hormones from the organs that produce them to the organs where they are needed. For example, insulin from the pancreas is a hormone necessary for the regulation of blood sugar levels
Blood pressure
Blood pressure is measured by
considering the systolic pressure and the diastolic pressure.
Systole
occurs when the ventricles contract and pump blood into the arteries.
Diastole
is the phase when the auricles contract to pump blood into the ventricles.
The pressure developed during these
actions can be felt in the arteries. It is measured in millimeters of mercury
(mmHg).
For example, if the pressure during
systole is 120 mmHg and the pressure during diastole is 80 mmHg, the blood
pressure is 120/80 mmHg. This is the average blood pressure in a normal human
being. A sphygmomanometer is the instrument used to measure blood
pressure.
Diseases and disorders of the human
circulatory system
The diseases and disorders of the
human circulatory system are increased by eating habits and lifestyles. Eating
food with high levels of cholesterol and fat causes narrowing of blood vessels
due to deposition in blood vessels. Lifestyles such as smoking, lack of
exercise, stress and taking alcohol also put one in danger of developing heart
problems such as coronary heart disease and high blood pressure.
Arteriosclerosis
Arteriosclerosis is the hardening of
arteries. It happens when there are fat deposits on the wall of the artery or
when fibrous tissues form in the artery wall or artery walls degenerate;
Arteriosclerosis hinders the
arteries from pulsating normally. The lumen is narrowed, affecting the
efficiency of blood flow
