Human Physiology - 6.2 The Blood System Flashcards
Blood is composed of:
- Plasma (made up of H2O, blood proteins + nutrients)
- Erythrocytes
- leukocytes
- Platelets (clotting)
Erythrocytes =
red blood cells
Leukocytes =
white blood cells
2 main functions of blood
- Transport
- Degence against infectious diseases
- transport - function of blood
- erythrocytes transport oxygen from the lungs to cells
- blood plasma transports nutrients, CO2, antibodies, urea
- Heat is transported from parts of the body that produce it, to the skin, where it is lost to the environment
- Degence against infectious diseases
- Blood clotting
- Leukocytes (white blood cells) defend the body against infectious diseases
high and low pressure in the heart
- blood going out of the heart = high pressure
- blood going into the heart = low pressure
Double circulation =
found in mammals and birds (with 3 chambered heart) where there is a separate circulation for the lungs
Structure of the heart
(refer to diagrams)
- 4 chambered organ = 2x atria + 2x ventricles
atria =
acts as a reservoir, by which blood returning to the heart is collected via veins (and passed on to ventricles)
Ventricles =
act as pumps, expelling the blood from the heart at high pressue via arteries
Systemic circulation =
left side of the heart pumps oxygenated blood around the body
= much thicker muscular wall as it must pump blood much further
pulmonary circulation =
right side of the heat pumps deoxygenated blood to the lungs
myocardium -
muscular wall
DIAGRAM WARNING!
when looking at a heart diagram - often wrong way around (ie left = right and right = left) ==> done so when you hold it to your chest it is correct
William Hervey (theory + experiments)
showed that:
= arteries and veins were part of a single blood circuit
= arteries pumped blood from the heart to the lungs and body tissues
= veins returned blood to the heart from the lungs and body tissue
before William Hervey
==> previously it was thought that the heart just warmed blood and that arteries and veins were SEPARATE blood circuits
Blood vessels = 3 types
- arteries
- veins
- capillaries
Arteries =
- carries oxygenated blood away from the heart
- convey blood at high pressure from the ventricles to the tissues of the body
- thick walls (3 LAYERS (TUNICA))
- Thick outer layer (of longitudinal collagen and elastic fibres to avoid bulges and leaks
- thick middle layer (large amounts of elastic and muscle fibres to help pump the blood on after each heart beat by maintaining blood pressure between pump cycles
- narrow lumen (to help maintain high pressure)
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/62-the-blood-system/arteries.html
Veins =
- carries deoxygenated blood toward the heart (and oxygenated blood from the lungs to the heart)
- veins collect blood at low pressure from the tissues of the body and return into atria of the heart
- valves in veins and the heart ensure circulation of blood by preventing backflow
- thin inner layer (with a few circular elastic and muscles fibres because blood does not flow in pulses so the beins wall cannot help pump i
- wide lumen (needed to accommodate the slow-flowing blood)
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/62-the-blood-system/veins.html
Capillaries =
- small vessels (carry materials to and from cells)
- wall = consists single layer of HTIN cells (so the distance for diffusion in/out is small)
- pores between cells in the wall allow some of the plasma to leak out and form tissue fluid (phagocytes can also squeeze out
- VERY NARROW LUMEN (so that capillaries fit into small spaces (many small capillaries have a larger surface area than fewer wider ones)
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/62-the-blood-system/capillaries.html
general heart structure outline
right side = pumping blood to the lungs
left side = pumping blood to all other organ
walls of the heart - CARDIAC MUSCLE
Myogenic
contraction of cardiac muscle –> it can contract on its own, without being stimulated by a nerve
atria =
collecting chambers in the heart - collect blood from the veins
ventricles =
pumping chambers - they pump blood out into the arteries at high pressure
valves =
ensure that the blood always flows in the correct direction
the action of the heart
- walls of the atria contract
- walls of the ventricles contract
- ventricles stop contracting
the action of the heart - walls of the atria contract…
pushing blood from the atria into the ventricles through the atrioventricular valves which are open - the semilunar valves are closed - so the ventricles fill with blood
the action of the heart - walls of the ventricles contract…
powerfully and the blood pressure rapidly rises inside them –> causing the atrioventricular valves to close, preventing back-flow of blood to the atria and causing the semilunar valves to open = allowing blood to be pumped out into the arteries –> at the same time the atria start to refill as they collect blood from the veins
the action of the heart - ventricles stop contracting…
as the pressure falls inside them the semilunar valves close = preventing the back-flow of blood from the arteries to the ventricles. When the ventricular pressure drops below the atrial pressure, the atrioventricular valves open. Blood entering the atrium from the veins then flows on to start filling the ventricles –> the next heartbeat begins when the walls of the atria contract again
muscle fibres
help to form a rigid arterial wall that is capable of withstanding the high blood pressure without rupturing
Muscle fibres can also contract to narrow the lumen, which increases the pressure between pumps and helps to maintain blood pressure throughout the cardiac cycle
elastic fibres
allow the arterial wall to stretch and expand upon the flow of a pulse through the lumen
The pressure exerted on the arterial wall is returned to the blood when the artery returns to its normal size (elastic recoil)
The elastic recoil helps to push the blood forward through the artery as well as maintain arterial pressure between pump cycles
Vessel comparison
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/62-the-blood-system/vessel-comparison.html
heart structure =
REFER TO DIAGRAM +
https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/62-the-blood-system/heart-structure.html
Cardiac Cycle
describes the series of events that take place in the heart over the duration of a single heart beat
Systole
contraction (when heart muscle contracts and blood is squeezed out of the heart and through the arteries –> PRESSURE IS HIGH)
Diastole
relaxation (when the heart is not contracted, blood from the veins fills the atria and the ventricles –> PRESSURE IS LOW, the heart is not pushing blood into the arteries.)
High blood pressure indicates =
blood may be having difficulty moving through vessels due to the build-up of fatty deposits inside arteries or thickening of artery walls
cardiac muscle =
walls of the heart ==> can contract on its own (without being stimulated by a nerve)
myogenic =
contraction of cardiac muscle
Coronary arteries =
blood running through the capillaries in the muscular wall of the heart are supplied by…
(also brings nutrients, oxygen and thus energy)
Coronary occlusion =
partial or complete obstruction of blood flow in coronary
If coronary arters become occluded…
the region of heart tissue nourished by the blocked artery will die and cease to function ==> leading to heart attack
Causes of coronary occlusion - atheroslerosis
= the hardening and narrowing of the artiers due to the desposition of cholesterol
atheromas (fatty deposits) = develop in the arteries and signif. reducde the diameter of the luman
atherosclerotic plaques
The restricted blood flow increases pressure in the artery leading to damage to the arterial wall. the damaged region is repaired with fibrous tissue which tissue which significantly reduces the elasticity of the vessel wall —> as the smooth lining of the artery is progressively degraded, lesions form…
Thrombus
plaque ruptures, blood clotting is triggered forming ____ = can block the artery ===> heart attack
Risk Factors for Coronary Heart Disease
There are several risk factors for coronary heart disease (CHD), including:
A GODDESS
Age – Blood vessels become less flexible with advancing age
Genetics – Having hypertension predispose individuals to developing CHD
Obesity – Being overweight places an additional strain on the heart
Diseases – Certain diseases increase the risk of CHD (e.g. diabetes)
Diet – Diets rich in saturated fats, salts and alcohol increases the risk
Exercise – Sedentary lifestyles increase the risk of developing CHD
Sex – Males are at a greater risk due to lower oestrogen levels
Smoking – Nicotine causes vasoconstriction, raising blood pressure
consequences of coronary occlusion
atherosclerosis can lead to blood clots which cause coronary heart disease when they occour in coronary arteries —> if it becomes completely blocked, an acture myocardial infraction can occour
myocardial infraction =
heart attack
treatment for blockages of coronary arteries =
by by-pass surgery or creating a stent
Pacemaker nerve =
region the controls the heart beat.
is located on the wall of the right atrium
each time the pacemaker nerve sends out a signal both atria contract. Once the atria have contracted then the AVN or VAN nerve in the ventricle is stimulated to cause the ventricles to contract
nerves and hormones can transmit messages to the pacemaker to control the heart rate
accelerator nerve (sympathetic nerve)
carries messages from the brain to the pacemaker that tell the pacemaker to speed up the beating of the heart
Decelerator nerve (parasympathetic nerve - vagus nerve)
carries messages from the brain to the pacemaker that tell the pacemaker to slow down the beating
Adrenalin (epinephrine)
if there is a danger then ___ produced by the adrenal gland near the kidney, is carried to the pacemaker by the bloodstream, tells the pacemaker to speed up the beating of the heart for flight or fight
Exercise and blood flow
blood flow must increase in order to provide the working muscle with more oxygenated blood. Chemical factors such as a decrease in oxygen concentration and an increase in CO2 or lactic acid concentration in the blood also make the blood vessels to expand to increase blood flow
when the muscles are active they respire more quickly nd cause several changes to the blood, such as decreased O concentration, increased CO2 concentration, decreased pH and increased temperature. All of these changes are detected by various receptor cells around the body, but the pH changes are the most sensitive and therefore the most important
