3.2 - Transport in Animals Flashcards
Def of double circulatory system
System in which the blood flows through the heart twice for each circuit of the body
Def of single circulatory system
System in which blood flows through the heart once for each circuit of the body
Def of transport
Movement of substances such as oxygen, nutrients, hormones, waste and heat around the body
What three factors influence need for a transport system?
Size
SA:V ratio
Level of metabolic activity
Influence of size on requiring transport system
Cells inside a large organism are further from its surface - diffusion pathway/distance is increased
So diffusion rate is reduced
So simple diffusion is too slow to supply all requirements
(Outer layer of cells will use up supplies, less will reach cells deeper inside body)
Influence of SA:V ratio on requiring transport system
Larger animals have a smaller SA:V ratio
Each gram of tissue has smaller area of body surface for exchange
So simple diffusion will not transport required amount of substances into body
Influence of metabolic activity on requiring transport system
Animals need energy from food
Releasing energy from food by aerobic respiration requires energy
The more active an animal is, the better supply of nutrients and oxygen is needed to supply energy for movement
(Animals that keep themselves warm, such as mammals, need even more energy)
Two features of a good transport system
Effective
Efficient
Features of an effective transport system
A fluid or medium to carry nutrients, oxygen and waste around the body - blood in humans
Pump to create pressure to push fluid around body - heart in humans
Exchange surfaces - enable substances to enter blood and leave it again where they are needed - capillaries in humans
Example of single circulatory system
Fish
Blood flows through one circuit of heart once for each circuit of the body
Heart - gills - body - heart
Example of a double circulatory system
Mammals
Two separate circuits - blood flows through heart twice for each circuit of body
One circuit carries blood to lungs to pick up oxygen - pulmonary circulation
Other circuit carries oxygen and nutrients around body to tissues - systemic circulation
Heart - body - heart - lungs - heart
Comparison of a double to single circulatory system - single system
Blood pressure drops as blood passes through tiny capillaries of gills
Blood has a low pressure as it flows towards the body, and doesn’t flow very quickly
Rate at which oxygen and nutrients delivered to respiring tissues, and CO2 and urea are removed, is limited.
Comparison of a double to single circulatory system - double system
Blood pressure must not be too high in pulmonary circulation, otherwise may damage capillaries in lungs
Heart can increase pressure of blood after has passed through lungs, so blood is under higher pressure as flows to body and flows quicker
Systemic circulation carries blood at higher pressure than pulmonary circulation
Why do fish have a single circulatory system?
Not as metabolically active as mammals
Don’t maintain their body temperature
Therefore need less energy
So single circulatory system delivers sufficient oxygen and nutrients for their needs
Why do mammals have double circulatory systems?
Mammals are quite active
Mammals maintain their body temp.
Energy for activity and supplying heat needed to keep body warm supplied from food
Energy released form food in respiration
To release a lot of energy, cells need a food supply of nutrients and oxygen
Cells need good removal of waste products
Features of an efficient transport system
Tubes or vessels to carry blood by mass flow
Two circuits - one to pick up oxygen and another to deliver oxygen to the tissues
Def of arteries
Vessels that carry blood away from the heart
Def of arterioles
Small blood vessels that distribute blood from an artery to the capillaries
Def of capillaries
Very small vessels with very thin walls found mainly in lungs
Def of closed circulatory system
System where blood is held in vessels
Def of open circulatory system
System where blood is not held in vessels
Def of veins
Vessels that carry blood back to the heart
Def of venules
Small blood vessels that collect blood from capillaries and lead into veins
Example of open circulatory system
In insects
Open circulatory system structure and process
Blood enters via a body cavity
Tissues and cells are bathed directly in blood
Open circulatory system process in insects
Blood from heart enters body through pores called Ostia
Heart then pumps blood towards head by peristalsis
At forward need of heart blood pours out into body cavity
(Circulation can continue when insect is at rest
Body movements may still affect circulation)
Disadvantage of open circulatory systems
Blood pressure is low, blood flow is slow
Circulation of blood may be affected by body movements or lack of body movements
Where are closed circulatory systems found?
Larger animals like mammals
Advantages of closed circulatory systems
Higher pressure so blood flows more quickly
More rapid delivery of oxygen and nutrients
More rapid removal of CO2 and other waste products
Transport is dependent of body movements
Direction of blood flow in arteries
Away from the heart and around the body
Structure of artery walls
Thick so can withstand high pressure
Small lumen to maintain high pressure
Inner wall is folded - allows lumen to expand as blood flow increases
Three layers of artery wall
Inner layer - thin layer of elastic tissue which allows walls to stretch and recoil to maintain blood pressure
Middle layer - thick layer of smooth muscle
Outer layer - relatively thick layer of collagen and electric tissue
Provides strength to withstand high pressure
Recoil to maintain the pressure
Arterioles
Small blood vessel that distribute blood from ey to the capillaries
Contain a layer of smooth muscle
Contraction of muscle constricts diameter of arteriole
This increases resistance to blood flow and reduces rate of flow of blood
Constriction of arteriole walls can be used to divert flow of blood to regions of body that demand more oxygen
Structure of Capillaries
Very thin walls - one cell thick
Allow exchange of materials between blood and tissue fluid
Narrow lumen, same diameter of a red blood cell(they can squeeze against walls of capillaries as they pass along capillary)
Helps transfer of oxygen as reduces diffusion path to the tissues
Increases resistance and reduces rate of flow
Walls consist of a single layer of squamous epithelial cells - reduces diffusion distance for exchange of materials
Walls are leaky/permeable - allow blood plasma and dissolved substances to leave the blood
Venule structure
Blood flows into them from capillaries
Venule wall consists of thin layers of muscle and elastic tissue outside endothelium
Has a thin outer layer of collagen