6.2 - the blood system Flashcards
1
Q
who discovered the circulation of blood and that the heart pumped blood?
A
- William Harvey
- found that blood had unidirectional flow, veins returned blood to heart and valves prevented backflow of blood
- blood flowed too high to be consumed by body
2
Q
what are arteries?
A
- type of blood vessel that carries blood from the heart to the tissue of body.
3
Q
how does an artery work?
A
- blood flows through the lumen (middle)
- ventricles of the heart pump high volumes of blood at high pressures
- so the walls of arteries are elastic and have muscle cells that facilitate and control this blood flow.
- elastin fibres in walls to help propel the blood through artery
- contraction of muscle in walls controls overall flow
- tough walls from elastic and muscular tissue, needed for pressure
- blood pulsates from contractions
- coronary arteries supply heart with blood
4
Q
whats the structure of the artery wall?
A
- several layers
- tunica externa is a tough outer layer of connective tissue
- tunica media is a thick layer containing smooth muscle and elastic fibres made of protein elastin
- tunica intima is the internal layer of smooth endothelium that lines the lumen of the artery
5
Q
how does arterial blood pressure work?
A
- blood enters artery at high pressure form heart
- peak pressure is called systolic pressure
- This pushes the wall of artery out, widening the lumen and stretching the elastic fibres in the wall, storing potential energy.
- end of a heartbeat, the pressure in arteries falls and the stretched
elastic fibres squeeze the blood in the lumen, saving energy and preventing the minimum pressure (called diastolic pressure) from getting too low. - lumen narrows when circular muscles contract, vasoconstriction
- vasodilation causes an increase in
blood flow and decreases blood pressure.
6
Q
what is a capillary?
A
- tiny blood vessel
- they branch and connect to form a network of capillaries
- they transport blood to most tissue of the body except the lens and cornea of the eye
- link arteries and veins in the tissue
7
Q
structure of a capillary?
A
- wall consists of one very thin layer of endothelium cells coated with a protein gel and pores between the cells
- wall is very permeable and plasma can leak out from the lumen to form tissue fluid
- Tissue fluid contains oxygen, glucose and other things found in plasma but not plasma proteins
- tissue fluid flows between cells in tissue so they can absorb useful substances and secrete waste
- tissue fluid then re-enters the capillary network
- blood pressure in capillaries is extremely low due to the excessive branches of capillaries (lower volume).
- slows the movement of blood for efficient exchange of materials
8
Q
what is the structure veins?
A
- blood from capillaries enters veins to be transported back to the atria of the heart
- blood pressure is low in veins
- walls contain less muscle and elastic fibres bc less pressure
- the lumen of veins becomes wider
as they can dilate so to hold more blood than arteries. - Gravity and skeletal muscle contractions allow for blood to flow through veins.
- Muscle contractions act as a pump during movement to move blood.
9
Q
what do valves do?
A
- low pressure in veins can flow backwards to the capillaries and not enough blood is returned to the heart.
- To prevent this, veins have valves which are 3 cup-shaped flaps of tissue without muscle.
- Valves open when blood flows towards the heart as it pushes the flaps to the side of the vein
allowing blood to flow freely. - If blood flows back, it is caught in the flaps of the pocket valve, which fills with blood and is blocking
the lumen of the vein. - As a result, blood is circulated in one direction.
10
Q
what is a single circulation system?
A
- when blood flows in one direction to the gills to be oxygenated before flowing to the organs and heart
11
Q
what is the double circulation system?
A
- a separate circulation for gas exchange
- blood capillaries in lungs cant have high pressure, so pumped to lungs at low pressure
- blood from lungs goes back to heart oxygenised to pump to other organs at high pressure
- There is pulmonary circulation to and from the lungs, and systemic circulation to and from the other organs
- Blood is delivered under different pressures and separately in the two
circulations in mammals
12
Q
explain the heart structure.
A
- right side pumps to the pulmonary circulation
- left side pumps to systemic circulation
- atriums collect blood from veins and pumps it into the ventricle
- ventricle pumps blood into the arteries of each circulation
- Each side of the heart has two sets of valves: an atrioventricular valve between the atrium and ventricles, and semilunar valves between the
ventricles and arteries - Deoxygenated blood flows into the right side and oxygenated blood flows through the left side
13
Q
what is Atherosclerosis?
A
- a chronic disease caused by elevated serum cholesterol levels (in blood) that result in lipids deposited in walls of arteries
- releases growth factors that stimulate the muscle and fibrous tissues in the artery wall to thicken
14
Q
what is the sinoatrial node? (SA node)
A
- a group of specialised muscle cells in the wall of the right atrium with the fastest contraction rate
- they have few proteins but many membranes that cause other cells to contract, it initiates heartbeat
- Contractions of the heart muscle can occur without external stimulation from motor neurons
- This contraction is called myogenic, where the muscle generates the contraction
- The membrane of the heart muscle cell depolarises, when the cell contracts, and this activates adjacent cells to also contract
15
Q
SA node initiating heartbeat.
A
- it sets the pace for the regular beating (sinus rhythm) of the heart and is often referred to as the pacemaker
- each impulse will spread across the wall f the heart, and stimulates the chamber to contract
- defective SA node can be replaced with an artificial pacemaker where electrodes are implanted into the wall of the heart to initiate each heartbeat
