Ch26 The Heart And Blood Vessels Flashcards
Why do we need a circulatory system?
Small organisms (amoeba) have no circulatory system
-diffusion work to transport nutrients in organisms that are only a few cells thick
Larger organisms need a circulatory system to supply cells with materials they require
Two types of circulatory systems
Open blood system
Closed circulatory system
Open blood system
Heart pumps blood into open ended blood vessels
Eg crab, lobsters, insects, snails
Closed circulatory system
Blood remains in a continuous system of blood vessels
Eg. Humans
Advantages of a closed system
- Blood can be pumped around the body faster
- allows nutrients and oxygen to reach cells faster, which allows the animal to be more active - Allows blood flow to different organs to be increased or decreased
- eg. more blood can be supplied to leg muscles when running
Composition human circulatory system
Blood
The heart
Blood vessels
3 types of blood vessels
Arteries
Veins
Capillaries
Arteries
Carry blood away from the heart
Divide into smaller vessels called arterioles
Veins
Carry blood to the heart
Small veins -> venules
Capillaries
Link arteries and veins
Artery structure
- Carry blood under high pressure
- Have a thick muscle layer
- Have a narrow lumen
Veins structure
- Carry blood under low pressure
- Have a thinner muscle layer
- Have a wide lumen
Middle of arteries and veins
Lumen
3 layers in the walls of arteries and veins
- Outer layer of tough, inelastic protein (collagen)
- prevents wall from over-expansion - Middle layer of muscle and elastic fibres
- allows vessels to expand during exercise or when we are hot - Inner, single layer of cells -> endothelium
Venous bleeding
Steady flow
Maroon coloured blood
Arterial bleeding
Spurting
Bright red blood
Blood pressure
The force exerted by the blood against the walls of the blood vessels (mainly arteries)
Valve function
Prevent backflow in veins
Blood pressure in arteries
Highest in arteries when the heart contracts
What causes a pulse
As the heart contracts, blood pressure is highest in arteries and this pressure causes the artery to expand slightly and is detected as a pulse
Blood pressure in veins
Blood pressure in veins is low, blood flow is slow
How do skeletal muscles help blood flow
When skeletal muscles contract, they squeeze on the veins pushing blood along
Arterioles
Connect arteries and capillaries
Venules
Connect capillaries and veins
Capillaries
Tiny vessels whose walls are made of a single layer of endothelial cells
Artery points
-Carry blood away from the heart
-Blood under high pressure
-Thick walls
-small lumen
-blood flow in pulses
-valves absent
-blood high in oxygen (except pulmonary artery)
Veins
-Carry blood to the heart
-Blood under low pressure
-Thin wall
-Large lumen
-Blood flows smoothly (no pulse)
-Valves present
-Blood low in oxygen (except pulmonary vein)
Draw diagram of a heart
Atria
- Have thin walls as they only pump blood a short distance to the ventricles
Ventricles
-right ventricle pumps blood to lungs
-left ventricle pumps blood to head and body
Which ventricle is thicker and why
Wall of Left ventricle is thicker as blood travels further from here
What are atria and ventricles separated by
Atria and ventricles are separated by valves which are held in place by tendons
3 valves
Tricuspid
Bicuspid
Semilunar
Tricuspid valve
Right side valve - 3 flaps
Prevents back flow into right atrium
Bicuspid valve
Left side valve - 2 flaps
Prevents backflow into left atrium
Semilunar valves
Allow blood into aorta and pulmonary artery
Prevents backflow into heart
Deoxygenated blood flow in the heart
-enters through vena cava
-enters right atrium
-moves into right ventricle
-leaves through the pulmonary artery ( to lungs )
Oxygenated blood flow in the heart
-enters through the pulmonary veins
-into left atrium
-moves into left ventricle
-leaves through aorta (to head and body)
Double circulation
The septum in the heart separates oxygenated and deoxygenated blood
-pulmonary circuit
-systemic circuit
Pulmonary circuit
Pumps blood to the lungs and back to the heart
Systemic circuit
Pumps blood to the head and body and back to the heart
Longer so, the walls of the left ventricle are thicker
Advantages of double circulation
-allows separation of oxygen-rich and oxygen-poor blood
-ensures blood pressure is high enough to reach all parts of the body
Portal system
A blood pathway that begins and ends in capillaries
-the hepatic portal vein connects the stomach and intestines to the liver (8cm)
How is heart muscle supplied with blood
By coronary arteries
- they branch from the aorta just above the semi-lunar valves
How is blood drained from heart muscle
By the coronary veins
- they return blood directly to the right atrium
Blockage of coronary arteries
Causes chest pain - angina
Sometimes causes heart attack
