8.2 - Blood Vessels Flashcards
Why do multicellular organisms require transport systems?
- large size - small SA:V ratio - subsequently high metabolic rates
- demand for oxygen is high - need a specialised system to ensure a strong supply to all respiring tissues
Summarise the different types of circulatory system
• Open = blood can diffuse out of vessels eg. Insects
• closed = blood confined to vessels eg. Fish , mammals
Single = blood passes through pump once per circuit of the body
Double = blood passes through heart twice per circuit of the body
What are the 3 layers of the arteries?
- tunica externa
- tunica media
- tunica intima
Explain the structure of the tunica intima
- made up of an endothelial layer - layer of connective tissue and a layer of elastic fibres
- endothelium is one cell thick and lines the lumen - very smooth and reduces friction for free blood flow
Explain the structure of the tunica media
• made up of smooth muscle cells and a thick layer of elastic tissue
• very thick
• layer of muscle cells strengthen the arteries so they can withstand high pressure- enables them to contract and narrow the lumen for reduced blood flow
• elastic tissue - helps maintain blood pressure- stretches and recoils to even out any fluctuations in pressure
Explain the structure of the tunica externa
• covers the exterior of the artery and it’s mostly made up of collagen
• collagen - strong protein protects blood vessels from damage by overstretching
Why do arteries have narrow lumens?
Helps maintain a high blood pressure
Is a pulse present in arteries?
Yes
What is the structure of the arterioles?
• have a muscular layer that means they can contract and partially cut off blood flow to specific organs
• lower proportion of elastic fibres and a large number of muscle cells
• presence of muscle cells allows them to contract and close their lumen to stop and regulate blood flow
What is the structure of the veins?
• tunica media is much thinner in veins
• no need for a thick muscular layer as veins don’t have to withstand high pressure
• large/ wide lumen - helps ensure that the blood returns to the heart at a adequate speed
• rate of blood flow is slower
• large lumen means the volume of blood delivered per unit of time is equal
• contain valves
Is there a pulse in veins?
No
What is the structure of the venules?
• few or no elastic fibres and a large lumen
• blood is at low pressure after passing through the capillaries there is no need for a muscular layer
• connect capillaries to the veins
What is the structure and function of capillaries?
- thin walls that are leaky - allowing substances to leave the blood to reach the body’s tissues
- Form networks called capillary beds which are important exchange surfaces
- very small diameter ( lumen )
- forces blood to travel slowly - provides more opportunity for diffusion to occur
- large number of capillaries branches between cells
- substances can diffuse between the blood bs cells quickly as there is a short diffusion distance
- wall is made from a single layer of endothelial cells
- only one cell thick - reduces the diffusion distance for oxygen and carbon dioxide between the blood and tissues of the body
- cells of the wall have gaps called pores which allow blood plasma to leak out and form tissue fluid
Describe the single circulatory system in fish
• deoxygenated blood is pumped to the gills from the heart
• gills are the exchange site where oxygen and carbon dioxide are exchanged with the atmosphere and the blood
• oxygenated blood flows from the gills to the rest of the body
• travels through the Capillaries in organs - delivering oxygen and nutrients
• blood returns to the heart
• heart only has one atrium and one ventricle
Describe the process of the double circulatory system in mammals
• left side - oxygenated blood
• right side - deoxygenated blood
• blood on the right side of the heat leaves and travels to the lungs
• blood returns on the left side of the heart before being pumped around the rest of the body
What are the advantages of a double circulatory system?
• when blood enters a capillary network the pressure and speed drops significantly
• blood only passes through one capillary network before returning to the heart
• maintains higher blood pressure and average speed of flow
• increased pressure and speed helps to maintain a steeper concentration gradient which allows for the efficient exchange of nutrients and waste with the surrounding tissues
Explain the circulatory system in insects
• one main vessel - dorsal vessel
• tubular heart in the abdomen pumps haemolymph ( blood ) into the dorsal vessel
• dorsal vessel delivers the haemolymph into the haemocoel body cavity
• haemolymph surrounds the organs and eventually renters the heart via on way valves called ostia
Define closed circulatory system
Where the blood is enclosed in blood vessels and does not come into direct contact with the cells of the body beyond the blood vessels
State some similarities between a mammals and a fish circulatory system
- both have a heart
- both have closed systems
- both carry oxygen using haemoglobin
State some differences between the circulatory systems of mammals and fish’s
- fish have 1 ventricle , 2 chambers and no septum
- mammals have 2 ventricles , 4 chambers and a septum in the heart
- fish have a single circulatory system
- mammals have a double circulatory system
- blood pressure to the organs in a fish is lower
- blood pressure is maintained at higher pressure in mammals
- blood passes through 2 sets of capillaries before returning to the heart in fish
- blood passes through 1 set of capillaries before returning to the heart in mammals
- as fish are cold blooded they have a low oxygen demand and low metabolic rate
- as mammals need to maintain a constant body temperature they have a high oxygen demand and high metabolic rate
