Chapter 8 Flashcards
Why do multicellular organisms need transport systems ?
High metabolic rate- the demand for oxygen is too high to be supplied by diffusion over long distances
Size- the distance to inner cells is too far for diffusion to supply these cells with the oxygen needed
Surface area to volume ratio-. As an organism gets bigger the surface area to volume ratio becomes much smaller
What is an open circulatory system
Insects have open circulatory systems
The heart pumps fluid called haemolymph through short vessels into a large cavity called the haemocoel
Here the haemolymph bathes the organs and tissues to diffuse substances
The heart relaxes and the haemolymph is sucked back via pores called Ostia
What is a single closed circulatory system ?
The blood is enclosed in vessels and only passes through the heart once for each complete circuit of the body. Fish has single closed circulatory systems
What is a double closed circulatory system?
The blood is enclosed in vessels and passes through the heart twice for each complete circuit
What are arteries
Blood vessels which carry blood under high pressure away from the heart with thick muscular walls made of elastic fibres, smooth muscle and collagen
The elastic fibres allow them to stretch and recoil
What are arterioles
Arteries branch into arterioles which have less smooth muscle and elastin
They can constrict and dialate to control the flow of blood to organs
What are Capillaries?
Link arterioles and venules they are only one cell thick and have a large surface area for diffusion
What are venules?
Venules link capillaries to veins they have very thin walls with a little smooth muscle
What are veins?
Veins take blood under low pressure back to the heart. They have little elastic fibre or muscle tissue and large lumen to help flow. They have valves to prevent backflow
What is the composition of blood?
It is 55% plasma which carries glucose, amino acids, hormones, proteins and mineral ions
It is 45% erythrocytes (red blood cells), platelets and leucocytes (white blood cells)
How are tissue fluids formed ?
1) at the arteriole end of the capillary bed the blood has a higher hydrostatic pressure than the tissue fluid so fluid moves out of the blood into the tissue fluid
2) moving down the oncotic pressure caused by plasma proteins means water has a tendency to move into the blood by osmosis
3) at the venule end the hydrostatic pressure is much lower so fluid moves back into the capillaries
4) not all fluid re enters, the excess passes into a lymph vessel and becomes lymph where it is moved towards the main lymph vessel in the thorax and returned to the blood
What is tissue fluid made up of?
Water, dissolved solutes, few white blood cells and few proteins
What is lymph made up of?
Water, dissolved solids and white blood cells
Draw a diagram of the structures of the heart
Diagram
Explain the process of the cardiac cycle
1) SYSTOLE- Ventricles relax and atria contract decreasing thier volume increasing pressure causing the atrioventricular valves to open pushing blood into the ventricles
2) atria relax and ventricles contract decreasing thier volume and increasing thier pressure which forces the atrioventricular valves closed and the semi lunar valves open forcing blood out the pulmonary artery/ aorta
3) DIASTOLE The atria and ventricles relax the high pressure in the pulmonary artery and aorta cause the semi lunar valves to close preventing backflow . The low pressure caused the atrioventricular valves to open and the atria and ventricles to fill with blood
