Circulatory System
- Created by: Emily Cartwright
- Created on: 29-05-14 13:45
View mindmap
- Circulatory System
- Single-celled organisms such as amoeba can obtain nutrients and excrete waste simply by diffusion across the cell membrane. They can do this because;
- They have a short diffusion pathway, so the rate of diffusion will satisfy demand
- They have a slow metabolic rate, so demand is low
- In multi-cellular organisms, diffusion through the membrane is too slow to satisfy the needs of an organism because;
- They have a low SA:Vol ratio
- They have a high metabolic rate
- Some cells are deep within the body, creating a long diffusion pathway
- They have a tough outer surface so gases cannot diffuse through their skin
- Mass Flow
- Multicellular organisms have developed a specialised transport system to carry materials from their specialised exchange organs to their body cells
- In mammals this is the circulatory system. It uses blood to carry gases, nutrients, hormones and waste products around the body
- This bulk movement of blood is called mass flow
- In mammals this is the circulatory system. It uses blood to carry gases, nutrients, hormones and waste products around the body
- A mass flow system has the following features;
- A suitable medium to carry materials
- A closed system of vessels that contain blood and form a branching network to distribute it to all parts of the body
- A pump e.g. the heart for moving blood within the vessels
- Valves to maintain the flow in one direction
- A respiratory pigment which increases the volume of oxygen that can be transported
- Multicellular organisms have developed a specialised transport system to carry materials from their specialised exchange organs to their body cells
- Types of circulatory system
- Open circulatory system
- e.g Insects and Snails
- Blood doesn't flow through vessels
- It is pumped at low pressure out of a large dorsal, tube shaped heart running the length of the body into a fluid filled body cavity, haemocoel
- Blood bathes the tissues directly and exchange of materials takes place. There is little control over the direction of circulation of the blood
- Blood then returns to the heart slowly
- In the heart, valves and waves of contraction of the muscle move the blood forward to the head region where the open circulation is started again
- There is no respiratory pigment in the blood as it does not transport oxygen. This is transported directly to the tissue via the tracheae
- In the heart, valves and waves of contraction of the muscle move the blood forward to the head region where the open circulation is started again
- Blood then returns to the heart slowly
- Blood bathes the tissues directly and exchange of materials takes place. There is little control over the direction of circulation of the blood
- It is pumped at low pressure out of a large dorsal, tube shaped heart running the length of the body into a fluid filled body cavity, haemocoel
- Blood doesn't flow through vessels
- e.g Insects and Snails
- Closed circulatory system
- e.g. Mammals
- Blood is contained in vessels
- Blood is pumped by a muscular heart and is under pressure, so had a rapid flow rate
- Organs are not in direct contact with the blood, but are bathed in tissue fluid seeping out from this walled capillaries
- The blood contains a respiratory pigment which carries oxygen
- Organs are not in direct contact with the blood, but are bathed in tissue fluid seeping out from this walled capillaries
- Blood is pumped by a muscular heart and is under pressure, so had a rapid flow rate
- Blood is contained in vessels
- Earthworms
- Even though the earthworm is a relatively simple organism, it also has a closed circulatory system
- It has dorsal and ventral vessels running the length of the body and is connected by 5 pseudohearts
- Blood moves through the vessels by the pumping action of the pseudohearts
- It has dorsal and ventral vessels running the length of the body and is connected by 5 pseudohearts
- Even though the earthworm is a relatively simple organism, it also has a closed circulatory system
- e.g. Mammals
- Open circulatory system
- Single and double circulatory systems
- Closed circulatory systems are of two types depending on whether blood passes through the heart once or twice
- Single
- Fish have a single circulatory system
- The heart pumps deoxygenated blood to the gills
- Oxygenated blood is carried to the tissues. From there, deoxygenated blood returns to the heart
- Blood only passes through the heart once in one circuit of the body
- Oxygenated blood is carried to the tissues. From there, deoxygenated blood returns to the heart
- The heart pumps deoxygenated blood to the gills
- Fish have a single circulatory system
- Double
- In each circuit, blood passes through the heart twice
- Once through the right side of the heart - pulmonary circulation - consists of all of the vessels concerned with pumping blood between the heart and lungs
- Once through the left side of the heart - systemic circulation - which consists of all of the vessels concerned with pumping blood between the heart and the body
- Once through the right side of the heart - pulmonary circulation - consists of all of the vessels concerned with pumping blood between the heart and lungs
- The right side of the heart pumps deoxygenated blood to the lungs
- Oxygenated blood then returns to the left side of the heart
- The left side of the heart pumps oxygenated blood to tissue and deoxygenated blood returns to the right side of the heart
- Oxygenated blood then returns to the left side of the heart
- Advantages
- Sustained high blood pressure in the systemic circulation
- Circulation is faster in the systemic circulation
- Oxygenated and deoxygenated blood are kept seperate
- Increased oxygen distribution, which can maintain a higher metabolic rate
- In each circuit, blood passes through the heart twice
- Single
- Closed circulatory systems are of two types depending on whether blood passes through the heart once or twice
- Structure of the heart
- The heart is made of specialised cardiac muscle which has it's own blood supply and which is able to continuously contract and relax on it's own
- The heart muscle needs a good supply of blood to provide it with the nutrients and oxygen needed for contraction
- This is achieved by a dense capillary network that revieves blood from coronary arteries. The blood returns to the heart via the coronary vein
- The heart muscle needs a good supply of blood to provide it with the nutrients and oxygen needed for contraction
- The heart is, in effect two pumps side by side
- The left side of the heart receives oxygenated blood from the lungs and pumps it to the head and body, where oxygen is used in the tissues for respiration
- He right side of the heart recieves deoxygenated blood from the head and body and pumps it to the lungs to pick up oxygen
- The two sides of the heart are separated by a thick wall called the intervertricular septum
- The deoxygenated blood never mixes with the oxygenated blood
- The two sides of the heart are separated by a thick wall called the intervertricular septum
- He right side of the heart recieves deoxygenated blood from the head and body and pumps it to the lungs to pick up oxygen
- The left side of the heart receives oxygenated blood from the lungs and pumps it to the head and body, where oxygen is used in the tissues for respiration
- The heart is made of specialised cardiac muscle which has it's own blood supply and which is able to continuously contract and relax on it's own
- Single-celled organisms such as amoeba can obtain nutrients and excrete waste simply by diffusion across the cell membrane. They can do this because;
Comments
No comments have yet been made