Transport in Animals Flashcards
Why is there a need for transport systems in multicellulr organisms
Large organisms have small surface area to volume ratios and therefore diffusion alone would not happen at a fast enough rate to supply the organism with all the substances, like oxygen it requires to survive. The transport system allows for a short diffusion distance, while also maintaining the concentration gradient to allow for a high metabolic rate of the organism
Features of a good transport system
- A fluid or medium to carry the nutrients, oxygen and waste products
- A pump to create pressure tat will push the fluid around the body
- Exchange surfaces that enable substances to enter the blood and leave it again when they are needed
- Two circuits - one to pick up deoxygenated blood and one to deliveroxygenated blood
What are the different types of circulatory system
Closed system is where blood is transported in vessels, and therefore open is when its not
Single circulatory system is where blood only pumps through the heart once in a single circuit, but in double it pumps through twice
(also single circuits tend to have 1 artia and 1 ventricle, while double have 2 atria and 2 ventricles)
Open Vs Closed circulation
Open circulation systems:
Blood is not held within blood vessels. Instead blood fluid circulates in the body cavity = tissues and cells are bathed directly in blood
blood pressure is low so blood flow is slow + circulation of blood may be affected by body movements
Closed Circulation
Blood is enclosed within vessels - tissue fluid bathes the tissues and cells
blood is at higher pressure so flow is quicker and there is a more rapid deliver of oxygen and nutrients / removal of waste products + transport is independant of body movements
Open Circulatory system - insects
in some animals, movements of the body help to circulate the blood - without movements blood will stop moving and so transport stops
In other animals (insects) there is a long muscular tube (muscular pumping organ) that lies under the dorsal/upper surface of the body . Haemolymph/Blood from the body enters the heart through pores called ostia. The heart pumps this blood towards the head by peristalsis. At the forward end of the heart, the blood pours into the body cavity and circulation continues when animal is at rest, but body movements may still affect circulation
- larger insects have open ended tubes attached to the heart which direct blood towards active parts of the body (such as leg or wing muscles)
Advantages of double circulation
- comparing fish to mammals
in the single circulatory system of a fish:
(fish are less metabolically active and do not need to maintain high body temperatures - therefore they need less energy and their systems deliver sufficient oxygen for their needs)
- blood pressure drops as blood passes through capillaries in gills
- low blood pressure means slow blood flow around the body so the rate at which oxygen and nutrients are delivered to respiring tissues and waste is removed is limited
in the double circulatory system of a mammal:
(mammals are very active and need to maintain their body temperature - require lots of nutrients and oxygen for activity + removal of waste products)
- blood pressure must not be too high in the pulmonary circulation - could damage the capillaries
- heart can increase pressure after passing the lungs so travels fast through the body
- systematic circulation carries blood at higher pressure than pulmonary circulation
Blood vessels
Arteries - blood is transported away from the heart
Arterioles - small blood vessels that distribute blood from an artery to capillary
Capillaries - where exchange of substances occurs
Venules - small blood vessels that collect blood from capillaries and lead into veins
Vein - blood is transported towards the heart
All types of blood vessels contain a single layer of cells known as the endothelium - thin layer that is smooth to reduce friction between the wall and blood
Arteries
Arteries transport blood away from the heart and therefore have a small lumen to maintain the high blood pressure and a thick wall to withstand the pressure
Tunica intima - thin layer of elastic tissue which allows the wall to stretch and recoil to help maintain blood pressure
Tunica media - thick layer of smooth muscle which can relax and contract to control the size of the lumen and thus control blood flow
Tunica adventitia - thick layer of collagen for structure and support
Arterioles
Small blood vessels that distribute the blood from an artery to the capillaries. Their walls contain a layer of smooth muscle. Contraction of this muscle will constrict diameter of vessel, increasing resistance to flow and reduce rate of flow of blood. Constriction can be used to divert blood flow.
Capillaries
Allow for the exchange of materials between the blood and tissue fluid
- Have thin walls that are a single layer of flattened endothelial cells - one cell thick to allow for short diffusion distance
- Walls are leaky - allow blood plasma and dissolved substances to leave the blood
- Lumen is very narrow and diameter is similar to that of RBC’s - RBC’s are squeezed as they pass along which reduces the diffusion distance but increases resistance and reduce rate of flow
Venules
Blood flows from capillaries into venules which it transports to the vein
- thin layers of muscle and elastic tissue outside the endothelium, and a thin layer of collagen
Veins
Veins carry blood under low pressure to the heart so have a large lumen to ease blood flow and thin walls
- Walls have thinner layers of elastic, smooth muscle and collagen since they do not need to stretch, recoil or contract to reduce blood flow
- Contain valves to prevent backflow
Walls are thin, vein can be flattened by action of surrounding skeletal muscle. Contraction of this applies pressure to blood, forcing it to move along in a direction determined by valves.
What is hydrostatic pressure?
The pressure that a fluid exerts when pushing against the sides of a vessel/container
What is oncotic pressure?
The pressure created by the osmotic effects of the solutes.
What is blood plasma
Found within blood. Contains many blood cells and dissolved substances such as O2, CO2, minerals, glucose, amino acids, hormones and plasma proteins. Cells include the red blood cells (erythrocytes), various white blood cells (leucocytes) and fragments called platelets.
