3.2: Transport in animals Flashcards
What are the factors that influence a need for a transport system?
Size:
Cells inside a large organism are further from its surface
The diffusion pathway is increased - diffusion rate is reduced - too slow to supply all the requirements
Surface area to volume ratio
Small organism - sufficient area of body surface where exchange can occur
Large organism - smaller area of body surface
Level of metabolic activity
Animals that are very active need good supplies of oxygen (for respiration - food) and nutrients in cells to supply the energy for movement
- Animals that keep themselves warm need energy
What are features of a good transport system?
- Fluid or medium to carry oxygen, water and nutrients around the body - blood
- A pump to create pressure and push the fluid around the body - heart
- Exchange system enable substances to enter and leave the blood - Capillaries
- Tube of vessels to carry the blood by mass flow
- Two circuits - one to pick up oxygen and another to deliver it to the tissues
What is a single circulatory system?
Blood flows through the heart once for each circuit of the body
Heart -> gills -> body -> heart ->
Blood has low pressure (as it flows towards the body) and it doesn’t flow quickly
What is a double circulatory system?
Two separate circuits
- Pulmonary circulation - blood to lungs to pick up oxygen + low pressure as it may damage capillaries in lungs
- Systemic circulation - oxygen and nutrients around the body to tissues + blood can be made to flow more quickly by increasing blood pressure in the heart
What is an open circulatory system?
Blood fluid circulates through the body cavity - not always held within blood vessels
- Blood pressure is low and blood flow is slow
- Circulation of blood may be affected by body movements or lack of
What is a closed circulatory system?
Blood stays entirely inside vessels, tissue fluid bathes the tissues + cells
- Higher pressure - blood flows more quickly
- More rapid delivery of oxygen and nutrients
- More rapid removal of carbon dioxide and other wastes
- Transport is independent of body movements
What are arteries?
Blood vessels that carry blood away from the heart
Adapted to carry blood at high pressure
What are arterioles and their structure?
Carry blood from arteries into capillaries
- Smaller that arteries
- Larger lumen
- Walls have more smooth muscle and less elastin as they do not need to withstand high pressure
What are capillaries?
Site of diffusion between blood and body tissues
Form extensive network between arterioles and venules
What are venules and their structure?
Carry blood from capillaries into veins
- Smaller than veins
- They have very thin walls
- Very little smooth muscle
- Has valves
What are veins?
Blood vessels that return blood to the heart
Adapted to carry at low pressure
What are adaptations of arteries?
- Collagen - provides strength to prevent the vessel form bursting and to maintain vessel shape
- Elastic fibres - contain elastin that lets them stretch and recoil to minimise changes in pressure
- Thick smooth muscle layer - contracts/relaxes to constrict/dilate the lumen and control blood flow
What controls blood flow in the arteries and how does it do it?
Smooth muscle
Does this by vasoconstriction and vasodilation
What is vasoconstriction?
Smooth muscle contracts, constricting the blood vessel and decreasing blood flow
What is vasodilation?
Smooth muscle relaxes, dilating the blood vessel and increasing blood flow
What are adaptations of capillaries?
- Lumen is very narrow - allows red blood cell to be close to body cells
- Wall are thin - substances can be exchanged across a short diffusion distance by diffusion
- Highly branched - this provides a large surface area for diffusion
What are adaptations of veins?
- Collagen - provides strength to prevent the vessel from bursting and maintain vessel shape
- Little smooth msucle and elastic fibre - not much is needed due to low blood presssure and thinner walls allow veins to be easily compressed, aiding the flow of blood
- Valves - pocket valves shut to prevent the backflow of blood when veins are squeezed by surrounding skeletal msucle tissues
What does blood consist of?
- Plasma - mostly water, transports substances in solution
- Red blood cell - carry oxygen
- White blood cell - immune cells
- Platelets - involved in clotting
What are the functions of blood?
5x
- Transports O2 and CO2
- Transports nutrients from digestion
- Transports waste for excretion
- Transports hormone
- Transports food from storage
What is tissue fluid?
Fluid where cells are soaked in to facilitate substance exchange between cells and blood
What is tissue fluid not made out of?
- No red blood cell
- Fewer white blood cellss
- Fewer proteins
How is the formation of tissue fluid determined?
It is determined by the filtration pressure which is determined by osmotic and hydrostatic pressure
What is osmotic pressure?
Tendancy of H2O moving into blood by osmosis
Generated by plasma proteins that decrease water potential in the blood
Always -3.3kPa
What is hydrostatic pressure?
Pressure generated by heart contraction
Changes due to location:
- Arteriol = +4.6kPa
- Venous = +2.3kPa