The Circulatory System Flashcards
How many chambers does the heart have
4
3 main types of blood vessels
Arteries - blood away from heart
Veins - blood to heart
Capillaries - where the exchange between the blood and the cells takes place
Where does the right side of the heart send blood
To the lungs
Where does the left side of the heart send blood
Around the rest of the body
Blood always flows from a region of what to what
Higher pressure to lower pressure
What do valves do
Prevent blood from flowing backwards
Do heart valves need energy to work
No it’s the blood pressing on the valve that makes them open and close
What is the cardiac cycle (basic)
Sequence of events that occurs during one heartbeat
Explain the cardiac cycle
1) blood flows into the two atria
2) the atria contracts to push the blood into the ventricles
3) the ventricles contract forcing blood into the aorta and the pulmonary artery
4) the blood flows down the arteries and leaves the heart. The whole cycle starts again
Are the ventricles more powerful than the atria
Yes
The heart valves pop shut automatically
T to prevent back flow into the atria.
Why are ventricle walls thicker
They need to push the blood further
What happens to valves as soon as the ventricles relax
The valves at the top of the heart pop shut to prevent back flow of blood as the blood in the arteries is now under a bit of pressure
What do most muscles require to contract
A nerve impulse from the central nervous system
T or f
The heart produces its own electrical impulse
True
Where is the hearts pacemaker
A group of specialised cells called the Sino-atrial node in the wall of the right atrium
Where does the impulses form the hearts pacemaker spread across
The atria
Why does the heart muscle need oxygen and glucose
So it can respite and release the energy it need to function
What is the heart muscle supplied with blood from
The coronary arteries
What do the two main coronary arteries come of
The aorta
T or f
The coronary arteries are thick
False
What are arteries subdivided into
Smaller vessels called arterioles
What are arterioles subdivided into
Capillaries
What do capillaries join up to form
Veins
Describe arteries
Thick wall compared to diameter of the lumen
There’s an outer layer of fibrous tissue, them a thick layer of elastic tissue and smooth muscle
E. Then a very thin layer of folded endothelial tissue
Explain what happens when the ventricles contract and blood enters the arteries at high pressure.
This stretches the folded endothelium and elastic wal
S. When the ventricles relax, it’s the elastic recoil of the artery wall that keeps the blood pressure up. I,portantborgans like the kidneys wouldn’t be able to function if the blood pressure dropped too far between the heartbeats
Describe arterioles
Narrower than arteries and they have a high proportion of smooth muscle fingers and a lower proportion of elastic tissue
What happens when the circular muscle fibres of an arterioles contract
The diameter of the lumen is reduced so less blood flows through that vessel. This means that arterioles can control the amount of blood flowing into a particular organ
Describe a capillary
The waLls consist of a single layer of endothelial cells
Some capillaries have tiny gaps between the endothelial cells
How are capillaries well suited to thei jobs
They have very thin walls and the gaps between the cells allow water and substances like glucose and oxygen to diffuse quickly from the blood into the cells. Waste products such as carbon dioxide and urea diffuse from the cells into the blood.
Organs contain thousands of capillaries so altogether there’s a huge surface area for the exchange of substances
Blood flows quiche slowly though capillaries. This allows more time for diffusion to occur
Describe the vein
Large lumen and a relatively thin wall containing some elastic tissue and smooth muscle.
Veins also have valves that prevent the blood flowing backwards
When the leg muscle contracts what happens to the veins
They contract and bulge and press on the walls of the veins, pushing the blood up the veins . When the muscle relax, the valves close. This action helps the blood return to the heart
What is the bloods main function
To transport materials to and from the cells
Why do red blood cells have haemoglobim
It can carry oxygen
What is made when oxygen combines with haemoglobin
Forms oxyhemoglobin
