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Flashcards in Blood and Circulation Deck (12):

Describe the composition of the blood

Red blood cells - biconcave, no nucleus. They transport oxygen and contain mainly haemoglobin - loads oxygen in the lungs and unloads oxygen in other regions of the body
Lymphocytes - same size as red, large spherical nucleus. They produce antibodies to destroy microorganisms - act as memory cells to give us immunity.
Phagocytes - much larger cells with a large spherical nucleus. They engulf bacteria that have infected our bodies
Platelets - fragments of other cells. They release chemicals to make blood clot
Plasma - liquid part. carries blood cells, nutrias, hormones, carbon dioxide, and urea


What is the role of plasma?

Plasma is the liquid part of the blood, which is mainly water. It carries blood cells around the body, carries dissolved nutrients, hormones, carbon dioxide and urea. It also distributes heat around the body.


Explain how adaptations of red blood cells make them suitable for the transport of oxygen

They are biconcave shaped to allow efficient exchange of oxygen in and out of the cell. Each red blood cell has a high surface area to volume ratio to give a large area for diffusion. They have a thin cell surface membrane which allows oxygen to diffuse through easily. They have no nucleus. This gives them more space to carry more haemoglobin, therefore transporting more oxygen. There are millions in each mm3 of blood.


Describe how the immune system responds to disease

Phagocytes produce pseudopodia, they surround and enclose the microorganism in a vacuole. Once inside, the phagocyte secretes enzymes into the vacuole to break the microorganism down.
Lymphocytes produce antibodies, they recognise antigens on the surface of pathogens. The antibodies stick to the surface antigens and destroy the pathogen by causing bacterial cells to burst open. They stay in our blood and develop into memory cells so if the same microorganism re-infects, the memory lymphocytes start to reproduce and produce antibodies so that the pathogens can be quickly dealt with.


Describe the process of a vaccination (paper 2)

A person is injected with an age that carries the same antigens and multiply exactly as if that microorganism had entered the bloodstream. They produce memory cells and make the person immune to disease.


What are platelets? (paper 2)

They are fragments of large cells made in the bone marrow. If the skin is cut, expose to the air stimulates the platelets and damaged tissue to produce a chemical which causeless fibrinogen to change into fibrin. The fibrin forms a network around the wound so red blood cells become trapped. This forms a clot which prevents further loss of blood and entry of pathogens.


Describe the structure of the heart and how it functions

When blood enters the atria, it cannot pass in the ventricles because the atrioventricular vales are closed. The walls of the atria contract which increases the pressure of the blood in the atria which forces open the atrioventricular valves. Blood can pass into the ventricles.
When the ventricles are full, they contract which increases the pressure of the blood which closes the valves. Blood cannot return to the atria.
The ventricles continue to contract and the pressure continues to increase. This forces open the semi-lunar valves at the base of the aorta and pulmonary artery. Blood is ejected into these two arteries. The pulmonary artery carries blood to the lungs - Aorta has branches that carries blood to all other parts of the body.


Explain how the heart rate changes during exercise

When we exercise, out muscles much release more energy. They need an increased supply of oxygen for aerobic respiration to deliver the extra oxygen, both the heart rate and stroke volume increase. Our muscles produce more carbon dioxide. Sensors in the aorta and the carotid artery detect this increase so they send nerve impulses to the medulla which responds by sending nerve impulses along the accelerator nerve. The accelerator nerve increases the heart rate and it also causes the heart to beat with more force and so increases the blood pressure.


Describe the structure and roles of arteries, veins and capillaries

Arteries - carry blood from the heart to organs. The blood puts a lot of pressure on the walls of the arteries so the walls must be thick with muscle fibres and elastic tissue.
Veins - carry blood from organs to the heart. The pressure of the venous blood is much lower than arteries which puts less pressure on the walls of the veins so they need a thin wall with little muscle and elastic tissue. Veins also have "watch-pocket valves" which prevent the back flow of blood.
Capillaries - carry blood through organs, bringing it close to every cell. Substances are transferred between the blood and the cells so the wall of the capillary is one cell thick .


Describe the general structure of the circulation system

Arteries carry blood away from the heart, veins carry blood towards the heart and capillaries carry blood through organs.


Why do simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell?

They have a high surace area to volume ratio as they only have one cell so has a efficient rate of diffusion so Relies on Diffusion to Transport it with Necessary Substances that it Needs Quickly through the Membrane such as Oxygen and Glucose.


What is the need for a transport system in multicellular organisms?

Since multicellular organisms (animals and plants) have a smaller SA:volume ration and substances would have to travel a large distance to reach every single cell, diffusion would be very slow, unable to support the organism.

Therefore, they’ve developed transport systems (e.g. circulatory and ventilation system) to quicken the process of getting necessary molecules in/out of the body to support themselves.