B3 - Blood and The Circulatory Cycle Flashcards
What does blood contain?
Red blood cells Platelets Plasma White blood cells Haemoglobin
How are red blood cells adapted to their function?
Size: they are small in diameter and relatively thick. This means:
• They can just fit through capillaries, one at a time.
• Each has a large surface area compared to its volume (SA/V ratio) so a lot of oxygen can diffuse through the outer surface and into the centre of the cell.
Shape: they are biconcave discs. This increases the amount of surface compared to the inside volume even more.
No nucleus: before each red blood cell leaves the bone marrow, where it is made, and enters the blood, its nucleus breaks down. This leaves more room for lots of haemoglobin.
What is haemoglobin? What does it do?
- It is a carrier protein
- In the lungs the haemoglobin in red blood cells reacts with oxygen, forming oxyhaemoglobin.
- At respiring tissues the oxyhaemoglobin breaks down to haemoglobin and oxygen. The oxygen is delivered to the respiring cells.
What are platelets? What do they do?
Platelets are small cells that help your blood to clot when you cut yourself. This
• stops you bleeding
• prevents bacteria from entering the wound.
How does blood travel around in your body in terms of vessels and pressure?
• Blood leaves the heart at high pressure in arteries.
• It returns from the body tissues to the heart in veins.
• At capillaries glucose and oxygen leave the blood and enter cells, whilst waste carbon dioxide leaves the cells and enters capillaries.
Blood in your body moves from areas of high pressure to areas of low pressure.
Describe the properties of arteries.
- a thick muscular and elastic wall
- small lumen
- can withstand the high pressure generated by the heart pumping blood into them
Describe the properties of veins.
- a thinner wall
- larger lumen
- the blood is under low pressure
- to prevent blood flowing backwards, the veins have valves.
Describe the properties of cappilaries.
In tissues and organs - form a network, so no cell is very far from it. The blood flows slowly through capillaries and exchanges materials with the tissues. Capillary walls are permeable.
What diffuses in and out of capillaries?
Some of the blood plasma is forced out through holes in capillary walls and it bathes the cells. It then passes back into the capillaries and then into the veins.
• Glucose and oxygen pass (by diffusion) from this
plasma into the cells, for respiration.
• Amino acids pass into the cells to be made into
proteins the cell needs.
• Carbon dioxide and lactic acid pass from respiring
cells into the plasma.
How does blood circulate in your heart?
Blood goes from the left side of the heart to the body; back to the right side of the heart; from the right side of the heart to the lungs; back to the left side of the heart; and again to the body.
What do the different chambers do?
The left and right atria receive blood from veins. The left and right ventricles pump blood into arteries.
How are the chambers adapted for their function?
The right side of the heart pumps blood to the lungs = thinner wall + generates less pressure = delicate lungs are not damaged.
The left side of the heart pumps blood to the rest of the body
wall is thick and muscular = can generate higher pressures = fast delivery of oxygen to the body tissues and taking away waste quickly.
What is plasma? Function?
Plasma is the straw-coloured liquid part of the blood. Over 90% of it is water.
Dissolved in it and being carried are:
• digested food, such as amino acids and glucose, from the gut to body cells
• cholesterol, from the liver to cells
• hormones, from the glands where they are made to their target cells
• antibodies
• excess water from the gut, to the kidneys to be removed
• waste products such as carbon dioxide from respiring cells to the lungs, and lactic acid from muscles to the liver
• excess heat, from respiring cells to the skin.
