Transport Systems In Multicellular Animals Flashcards
What are the three main reasons multicellular animals need transport systems?
- Metabolic rate
- SA:V
- Transporting molecules e.g. food, hormones, enzymes and waste products
Why is metabolic rate a reason?
- Large multicellular organisms have high metabolic rates
- They require a high volume of substances and produce a lot of waste
- Diffusion alone wouldn’t be able to intake and expel all these substances
Why is SA:V a reason?
- In larger organisms, diffusion of substances would occur far too slowly to enable them to survive
- This is because their surface area to volume ratio is too small
Why is transporting materials a reason?
- Hormones and enzymes are often produced in by a gland in one part of the body and are required in another part of the body
- The circulatory systems are used to transport these materials
- Waste products of metabolism also need to be removed and disposed of from a particular part of the body
What does the circulatory system comprise of?
- Heart
- Fluid in which substances are transported
- Vessels through which the fluid can flow
What is an open circulatory system?
- Consists of a heart that pumps a fluid called haemolymph through short vessels and into a large cavity called the haemocoel
- In the haemocoel the haemolymph directly bathes organs and tissues enabling the diffusion of substances
What is meant by a close circulatory system?
System where the blood is fully enclosed within the blood vessels at all times
What is meant by a single circulatory system?
System where the blood passes through the heart only once in each complete circuit of the body
What is meant by a double circulatory system?
System where blood passes through the heart twice. Once in the pulmonary circuit between heart and lungs and then again in the systemic circuit between the heart and other organs
What are the advantages of a single circulatory systems?
-Less complex, does not require complex organs
What are the disadvantages of a single circulatory system?
- Low blood pressure
- Slow movements of blood
- Activity level of the animal tends to be low
What are the advantages of a double circulatory system?
- The heart can pump blood further around the body
- High pressure
- Fast flow of blood
What are the disadvantages of a double circulatory system?
- Over complicated
- Heart requires more energy due to 4 chambers
What are the five types of blood vessels?
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
Arteries are arterioles carry oxygenated blood except:
- Pulmonary artery
- Umbilical artery
What are the parts of the body with no blood flow?
- Cornea of the eye
- Lens of the eye
- Epithelium
- Cartilage
What are the three layers to blood vessels?
- Tunica externa-outer layer
- Tunica media-middle layer
- Tunica intima-inner layer
What is the tunica externa consisted of?
-Composed of collagen fibres and elastic fibres
What is the tunica media composed of?
- Smooth muscle cells
- Elastic tissue
- Collagen fibres
What is the tunica intima composed of?
-ONE layer of endothelial cells
composition depends on the blood vessel:
-Elastic arteries have a single layer of endothelium and then a supporting layer of elastin-rich collagen
-Muscular arteries only have a single layer of endothelium cells
What kind of blood do arteries and arterioles carry?
Oxygenated blood under very high pressure
Why do arterioles have more muscle and less elastic fibres than a big artery?
Because they need the muscles to contract and relax in order to lower the pressure of the blood before it enters the capillaries otherwise they would burst due to high pressure
What is an aneurysm?
A bulge or weakness in a blood vessel that can be fatal when it bursts
How can people screen their risk of an aneurysm?
- By monitoring the ratio of collagen:elastin. People at risk of an aneurysm will have a much higher amount of collagen compared to elastin
- In large aneurysms the ratio can increase to 7.91:1 compared to the normal value of 1.85:1
What are the adaptations of blood capillaries?
- Large surface area to allow metabolic demands to be met
- Cross sectional area is small to reduce rate of blood flow from the arteriole to allow enough time for exchange of materials
- Endothelium is one cell thick to provide a short pathway for diffusion
What are the three types of capillaries?
- Continuous capillaries
- Fenestrated capillaries
- Sinusoidal capillaries
What are continuous capillaries?
-The endothelial cells provide an uninterrupted lining, found in skeletal muscle
What are fenestrated capillaries?
Have pores known as fenestrae in the endothelial cells that are 60-80nm in diameter, found in endocrine glands
What are sinusodal capillaries?
A special type of open-pore capillary also known as a sinusoid that have wider 30-40um diameters and wider openings in the endothelium, found in the liver
What are the adaptations of arteries?
- Folded endothelium which helps artery contract and recoil to withstand high pressure of blood.
- Smooth muscle which contract and relaxes to change shape of lumen
- Narrow lumen to maintain blood pressure
- Thick wall withstands pressure
What are the adaptions of veins?
- Contain valves to prevent back flow of blood
- Large lumen as there is a large blood volume
- Less small muscle as blood is under low pressure
What are venules composed of?
Only collagen, no elastin fibres or smooth muscle
What’s the difference between valves and large valves?
Large valves will have active muscles moving the blood
What are varicose veins?
Where the vein wall becomes weakened and valves can no longer close properly. Allowing the back flow of blood causing the vein to become enlarged and bumpy. Usually happens to superficial veins (near skin surface)
What is vasoconstriction?
When the blood vessel constricts and becomes narrower by small muscles in the walls
Causes blood pressure to rise
What is vasodilation?
When the blood vessel dilates and becomes wider
Causes blood pressure to lower
What is blood composed of?
- Erythrocytes |
- Leucocytes | 45%
- Platelets. |
- Plasma 55%