Why do large organisms need a transport system?
With increasing size, the surface area to volume ratio decreases to a point where the needs of the organism cannot be met by the body surface alone. Specialised exchange surface needed.
What is the job of a transport system?
To absorb nutrients and respiratory gases and to remove excretory products. Take materials from cells to exchange surfaces and vice versa. MAterials have to be transported between exchange surfaces and environment. Also between different parts of organism.
What two factors does the presence of a specialised transport system depend on?
-How active organism is.
Lower SA:vol ratio and more active, more need for exchange system.
What are the 6 features of a transport system?
-Suitable medium to carry materials (blood) normally a liquid based on water- water readily dissolves substances.
-Form of mass transport in which transport medium is moved around in bulk over large distances.
-Closed system of tubular vessels containing transport medium and forms branching network.
-A mechanism for moving transport medium within vessels.
REQUIRES PRESSURE DIFFERENCE BETWEEN ONE PART OF SYSTEM AND ANOTHER.
+Muscular contraction either of body muscles or specialised organ.
+Plants use passive natural physical processes such as evaporation.
-Mechanism to maintain mass flow movement in ONE DIRECTION (valves)
-Means of controlling flow to suit changing needs of organism.
Outline the transport system in mammals.
Closed blood system, confined to vessels.
Heart (muscular pump) circulates blood.
DOUBLE CIRCULATORY SYSTEM.
Blood passes twice through heart for each complete circuit of body.
Why do mammals have a double circulatory system?
When blood passes through lungs, pressure is reduced. If was to pass straight to rest of body its low pressure would make circulation slow. Returned to heart to boost pressure. Substances delivered to rest of body quicker.
Why do mammals need substances delivered quickly?
High temperature so high rate of metabolism.
What are the three types of vessels in mammals circulatory system>
Arteries, veins capillaries.
What s the final journey of substances into the body and why is it rapid?
Into cells by diffusion. Large SA, short distance and steep diffusion gradient so rapid.
Leaving the aorta, what journey does blood take back?
UP TO: head and neck
DOWN TO: Hepatic arteries->LIVER
Stomach and intestines->hepatic portal vein->liver Renal artery->Kidneys
Head and neck and upper limbs-> vena cava
Liver-> Hepatic vein->vena cava
Kidneys->renal vein->vena cava
Lower limbs->vena cava
VENA CAVA-> Right atrium->Right ventricle->Pulmonary artery->LUNGS->Pulmonary vein-> Left atrium->Left ventricle->AORTA
carry blood away from heart and into arterioles.
Smaller arteries that control blood flow from arteries to capillaries.
Tiny vessels that link arterioles to veins
Carry blood from capillaries back to heart
Layers of arteries, arterioles and veins. (5)
-Tough outer layer- resists pressure changes from both within and outside
-Muscle layer- can contract and so control the flow of blood
-Elastic layer- helps to maintain blood pressure by stretching and springing back
-Thin inner lining (ENDOTHELIUM)- smooth to prevent friction and thin to allow diffusion.
-Lumen- not actually a layer but the central cavity of the blood vessel through which blood flows.
ARTERY SPECIFIC STRUCTURE
ELASTIC LAYER THICK
MUSCLE LAYER THICK
TOUGH OUTER LAYER
VEIN SPECIFIC STRUCTURE
ELASTIC LAYER MEDIUM
TOUGH OUTER LAYER
CAPILLARY SPECIFIC STRUCTURE
Structure of artery related to function (4)
-Muscle layer thick compared to veins:
constricted and dilated in order to control the volume of blood passing through them.
-Elastic layer is relatively thick compared to veins- important that blood pressure in arteries is kept high for blood to reach extremities of body.
Springs back (diastole).- helps maintain high pressure and smooth pressure surges created by beating of heart.
-Overall thickness of wall is large- resists vessel bursting under pressure.
-No valves (except leaving heart)- constant high pressure and therefore does not tend to flow backwards.
Function of artery
Transport blood rapidly under high pressure from the heart to tissues.
Function of arteriole.
carry blood, under lower pressure than arteries, from arteries to capillaries. Also control blood flow between two .
Structure of arteriole related to function. (2)
- The muscle layer is relatively thicker than in arteries- contraction allows constriction of lumen of the arteriole.
Restricts flow of blood and so controls its movement into the capillaries that supply the tissues with blood.
-Elastic layer is relatively thinner than in arteries- blood pressure lower.
Function of vein
Transport blood slowly, under low pressure, from tissues to the heart.
Structure of vein related to function. (4)
-Muscle layer relatively thin compared to arteries- veins carry blood away from tissues so constriction and dilation cannot control the flow of blood to the tissues.
-Elastic layer relatively thin compared to arteries- low pressure so won't burst, and too low for recoil action
-Overall thickness of wall small- no need for thick wall as no risk of bursting. Allows them to be flattened easily, aiding flow of blood between them.
-valves throughout- Ensure blood does not flow backwards. One way.
Function of capillary
Exchange metabolic material such as oxygen, carbon dioxide and glucose between blood and cells. Slow flow to allow time for exchange of materials.
Structure of capillaries related to function. (5)
Walls consist only of lining layer- extremely thin, short diffusion pathway, rapid diffusion between blood and cells.
-Numerous and highly branched
- large SA
-Narrow diameter- permeate tissues, no cell far from a capillary
-Narrow lumen- red blood cells squeezed flat against side of capillary. Brings them even closer to the cells to which they supply O2. Reduces diffusion distance.
-There are spaces between lining (endothelial) cells that allow white blood cells to escape in order to deal with infections within tissues.
What is the final journey of metabolic materials?
What is tissue fluid?
Watery liquid that contains glucose, amino acids, fatty acids, salts and oxygen. Tissue fluid supplies all of these substances to the tissues. In return, it receives CO2 and other waste materials from the tissues. Bathes all cells in body.
What is tissue fluid formed from?
From blood plasma, and composition of blood plasma is controlled by various homeostatic systems.
What is the path taken by blood from the heart? Vessels (simple)
Arteries- narrrower arterioles- even narrower capillaries
Hydrostatic pressure. Where is it created?
Pressure created by the blood on its path from the heart to capillaries. At arterial end of capillaries
What is the outwards pressure in vessels that forces tissue fluid out of blood plasma opposed by? (2)
-hydrostatic pressure of the tissue fluid outsidethe capillaries, which prevents outwards movement of liquid -the lower water potential of the blood, due to plasma proteins, that pulls water back into the blood within capillaries
Filtration under pressure- Outwards pressure only enough to force small molecules out of capillaries, leaving all cells and protein in the blood.
How does tissue fluid return to blood plasma?
-Loss of tissue fluid from the capillaries reduces the hydrostatic pressure inside them.
-As a result, by the time blood has reached the venous end of the capillary network its hydrostatic pressure is less that that of the tissue fluid outside it.
-Tissue fluid forced back into capillaries by the higher hydrostatic pressure outside them
-In addition, the osmotic forces resulting from the proteins the blood plasma pull water back into capillaries. `
How is the remainder of tissue fluid be carried back?
Via lymphatic system
System of vessels that begin in the tissues. Initially they resemble capillaries, but they gradually merge into larger vessels that form network throughout body. Larger vessels drain their contents back into the bloodstream via two ducts that join veins close to the heart.
How are the contents of the lymphatic system moved?
Hydrostatic Pressure of tissue fluid that has left capillaries. Contraction of body muscles that squeeze lymph vessels- valves ensure move in correct direction.