Organ system comprised of the heart, blood vessels (arteries, veins, capillaries), as well as the blood itself.
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Circulatory system functions
1. Transport O2 from lungs to respiring body parts. 2. Transport CO2 from respiring body parts to the lungs. 3. Transport nutrients from the gut to all body parts. 4. Transport urea from the liver to kidneys. 5. Transport hormones 6. Transport antibodies 7. Heat distribution, etc.
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Do small, unicellular organisms need and have a circulatory system? Why?
Small, unicellular organisms don’t have or need a circulatory system because of their high surface area : volume ratio, so substances can easily diffuse in and out of the cells. Their surface area is large enough (in proportion with their volume) to supply all the necessary oxygen and nutrients demanded by their volume.
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Supply rate
How much of needed substances an organism can get, it’s affected by the cell’s surface area.
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Demand rate
How much of needed substances an organism uses or requires, it’s affected by the cell’s volume.
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Do large, multicellular organisms need and have a circulatory system? Why?
Large, multicellular organisms need and have a circulatory system because of their low surface area : volume ratio, so substances cannot easily diffuse in and out of the cells. Their surface area is too small (in proportion with their volume) to supply all the necessary oxygen and nutrients demanded by their volume.
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In the circulatory system, … is pumped to a … to load … and to other … for …
blood, gas exchange organ, oxygen, body parts, unloading oxygen
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Single circulatory system
Circulatory system where blood travels 1 loop and is pumped from heart → gas exchange organ → rest of body, e.g. circulatory system in fish.
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Double circulatory system
Circulatory system where blood travels 2 loops and is pumped from heart → gas exchange organ → heart → rest of body.
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Double circulation system has 2 parts:
1. Pulmonary circulation 2. Systemic circulation
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Pulmonary circulation
Deoxygenated blood leaves heart through pulmonary arteries → blood becomes oxygenated after circulating through lungs → oxygenated blood from lungs returns to heart through pulmonary veins.
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Systemic circulation
Oxygenated blood leaves heart through aorta → blood circulates to rest of the body and unloads oxygen to regions that need it (e.g. respiring active tissue) → deoxygenated blood returns to heart through vena cava.
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The double circulatory system is more … than the single circulatory system, why?
efficient, Heart pumps blood to the heart twice in 1 circulation (from lungs to heart + from other body parts to heart) → Higher blood pressure maintained → Blood travels to organs faster (in single circulatory systems, such as for fish, blood loses pressure as it passes through the gills/gas exchange organ) → slower circulation to other organs
Hollow muscular organ that pumps blood around the body.
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Blood vessels
Tubular structures that carry blood around the body, including arteries/arterioles, veins/venules, and capillaries.
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Functions of blood vessels
1. Carry oxygenated and nutrient-rich blood to cells 2. Carry deoxygenated and nutrient- depleted blood containing bodily waste products away from cells 3. Maintain blood pressure 4. Enclose blood within blood vessels (bruising; blood vessels burst → internal bleeding → blood leaks/pools underneath skin into loose connective tissue → discolored bruised skin)
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Arteries
Blood vessels that carry blood away from the heart to other organs.
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Arterioles
Small branch of an artery leading/connecting into capillaries. They carry blood from arteries into organs.
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Arterioles VS Arteries structure
Similar structure but arterioles have more muscle fibres in their walls → Arterioles regulate blood pressure more efficiently than large arteries
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What allows arterioles to dilate and constrict?
Nerve endings in arteriole walls control dilation and constriction
Dilation → lumen widens → more blood flows into organs
Constriction → lumen narrows → less blood flows into organs
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… arteries carry … away from the … to the …, EXCEPT the … and … of an unborn …
ALL, oxygenated blood, heart, body, pulmonary artery, umbilical artery, baby
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Most blood vessels share a similar structure consisting of 3 distinct layers called …, this structure applies to … and …
tunics, arteries, veins
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Lumen
Central cavity of a tubular/hollow structure, it’s the open space containing the actual blood in a blood vessel.
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Tunica externa (a.k.a. tunica adventitia)
Outermost tunica (layer) of the blood vessel (specifically artery or vein) wall, made from loosely-woven collagen fibres. It provides basic structural support to blood vessels by preventing them from expanding too much or bursting due to internal blood pressure.
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Tunica media
Middle tunica (layer) of an artery or vein.
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The tunica media has 2 layers:
1. Smooth muscle cells 2. External elastic lamina
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Smooth muscle cells function in tunica media
Allow constriction or dilation of lumen to adjust blood flow. The tunica media’s smooth muscle tissue is regulated by nerve fibres.
Vasoconstriction → smooth muscle cells contract → narrower lumen diameter → less blood flows through
Vasodilation → smooth muscle cells relax → wider lumen diameter → more blood flows through
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External elastic lamina function in tunica media
External elastic membrane made from sheets of elastin, it allows arteries/veins to stretch under increased blood pressure, and separates the tunica media from the tunica adventitia.
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Elastin
Type of protein forming the main constituent of elastic connective tissue.
1 layer of thin, flattened endothelial cells lining blood vessels. It forms a smooth surface to reduce friction and enable blood flow.
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Loose connective tissue function in tunica intima
Helps keep the blood vessel in place.
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Internal elastic lamina function in tunica intima
Internal elastic membrane separating the tunica intima from the tunica media.
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Adaptations arteries have in terms of blood vessel structure
1. Narrow lumen (relative to wall thickness) → maintains high blood pressure 2. Thick layer of tunica media’s smooth muscle cells → helps conduct more vasoconstriction and vasodilation → regulates blood flow/pressure. 3. Tunica externa’s collagen → prevents artery from rupturing due to high blood pressure and controls vasoconstriction/vasodilation to regulate blood flow. 4. Elastic tissue to stretch and recoil (restore original shape) → helps maintain blood pressure.
1. Arteries closer to the heart require more elasticity due to exposure to higher blood pressure → they have more elastin to help with larger magnitudes/frequencies of stretching and recoiling. 5. More elastin than any other blood vessel → absorbs large pressure fluctuations as blood leaves the heart.
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Veins
Blood vessels carrying blood away from other organs to the heart.
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Venules
Small branch of veins, it branches out from capillaries and joins up with other venules to form veins, connecting the capillaries with veins.
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… veins carry … away from … to the …, EXCEPT the … and … of an unborn ...
all, deoxygenated blood, organs, heart, pulmonary vein, umbilical vein, baby
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Venous blood pressure … arterial blood pressure → … pressure on walls. Fluids move … a pressure gradient from a region of … pressure to a region of … pressure.
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Adaptations veins have in terms of blood vessel structure
1. Veins need to withstand less pressure than arteries → Thinner vein walls + less elastic tissue (don’t need to stretch/recoil as much), less smooth muscle cells (don’t need to constrict/dilate as much), and less connective tissue (won’t rupture) than arteries 2. Wider lumen than arteries (relative to wall thickness) → less resistance to blood flow → helps blood flow in correct direction despite low pressure 3. Low blood pressure in veins → Semi-lunar valves keep blood flowing in the correct direction
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Semi-lunar valves
Flaps of tissue (each tissue flap is called a “cusp” or “leaflet”) with a 1/2-moon shape (hence why they’re called semilunar).
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How do semi-lunar valves regulate direction of blood flow?
Semi-lunar valves open to allow blood to flow through (in 1 direction only) when blood pressure pushes open or against them. They close to prevent the back flow of blood, the blood will instead fill the pockets formed by their closure.
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Varicose veins
Damaged/weakened semi-lunar valves → blood pools in the wrong direction and collects in the veins → increased venous pressure → veins swell/bulge out
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Capillaries
Smallest type of blood vessel that carries blood through organs and connects arterioles to venules.
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Capillaries’ function
1. Transports oxygen, nutrients, and blood to body 2. Remove wastes like carbon dioxide, urea, etc 3. Connects arteries/arterioles and veins/venules
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Adaptations capillaries have in terms of blood vessel structure
1. Red blood cells fit perfectly inside capillaries’ lumen → close to capillary wall and surrounding cells → ↓ diffusion distance 2. Semipermeable membrane/wall → allows diffusion to occur 3. Only 1-cell thick walls (endothelium of tunica intima) → ↓ diffusion distance → faster diffusion 4. Blood vessel with smallest lumen → slowest blood flow → more time for substance (i.e. nutrients and gases) exchange. 5. Large lumen (relative to wall thickness) → ↑ surface area : volume ratio → faster diffusion
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Capillary bed
Interwoven network of capillaries that exchange nutrients, gases, waste products, and regulate blood pressure as well as temperature.
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Systole
State where the heart contracts to pump blood around the body.
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What happens to the heart valves during systole?
1. Closed atrioventricular valves → prevents blood blackflow 2. Ventricular pressure > arterial pressure → aortic and pulmonary valves open to let blood flow through to the aorta and pulmonary artery 3. Ventricular contractions → blood flows out of heart
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Diastole
State where the heart relaxes after contraction and is filled with blood.
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What happens to the heart valves during diastole?
1. Blood goes into atria → atrial pressure > ventricular pressure (more blood in atria and atria contract) → atrioventricular valves open to let ventricles get filled with blood 2. Ventricular pressure not yet > arterial pressure → aortic and pulmonary valves closed 3. Blood is filled into heart as it relaxes
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What tricuspid valve(s) (3 cusps/leaflets) is/are there?
What bicuspid valve(s) (2 cusps/leaflets) is/are there?
Mitral valve (left atrioventricular valve)
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Blood circulation cycle
Heart → pumps blood to aorta → branches into arteries → branches into arterioles → branches into a network of capillaries → joins to form venules → joins to form veins → joins to form superior and inferior vena cavae → drains blood back into heart
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Pulse
Rhythmic throbbing of the arteries as blood is propelled through them, typically felt in the wrist (in radial arteries supplying blood to the forearm and hands) or neck (in carotid arteries on each side of the neck).
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Radial pulse
Pulse felt on the wrist just underneath our thumb.
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Pulse rate
Measure of the heart rate through feeling how many pulses there are in the arteries per minute, it is the same as your heart rate.
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Resting heart/pulse rate for newborns/infants
100-160 bpm
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Resting heart/pulse rate for children who are 1-10 years old
70-120 bpm
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Resting heart/pulse rate for children over 10 years old and adults
60-100 bpm
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Resting heart/pulse rate for well-trained athletes
40-60 bpm
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Why can we feel our pulse?
Left ventricle contracts → Blood pumped out of heart through aorta and other arteries → arteries swell → arteries underneath or closer to skin can let us feel our pulse.
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Blood
Transport medium that circulates around the body, fluid tissue of circulatory system.
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Pulmonary means … ; Hepatic means … ; Renal means …
lung-related, liver-related, kidney-related
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Pulmonary artery
Artery carrying deoxygenated blood away from heart’s right ventricle to the lungs for oxygenation via gas exchange (diffusion of oxygen into blood and of carbon dioxide into lungs for exhalation).
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Pulmonary vein
Vein carrying oxygenated blood away from the lungs to the heart’s left atrium.
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Hepatic artery
Artery carrying blood away from heart to liver.
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Hepatic vein
Vein carrying blood away from liver to heart.
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Hepatic portal vein
Vein carrying blood from digestive system to liver.
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Mesentric arteries
Arteries carrying blood away from the heart to the digestive tract.
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Gastric artery
Artery carrying blood away from the heart to the stomach
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Renal artery
Artery carrying blood away from the heart to the kidneys.
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Renal vein
Vein carrying blood away from the kidneys to the heart.
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Superior vena cava
2nd largest bodily vein, it brings deoxygenated blood from the head, neck, arms, and chest (because oxygen is unloaded to respiring tissues in this area) to the right atrium of the heart.
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Inferior vena cava
Largest bodily vein, it brings deoxygenated blood from the legs, feet, and organs in the abdominal as well as pelvic regions (because oxygen is unloaded to respiring tissue in this area) to the right atrium of the heart.
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Right atrium
1 of the 4 cardiac chambers. It receives deoxygenated blood from the body and pumps this into the right ventricle.
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Interatrial septum
A thin wall of tissue separating the left and right atria of the heart, preventing mixture of oxygenated with deoxygenated blood.
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Tricuspid valve
An atrioventricular valve with 3 thin flaps of tissue (each tissue flap is called a “cusp” or “leaflet”) between the heart’s right atrium and right ventricle. It opens to let blood flow from the right atrium to the right ventricle (when atrial blood pressure > ventricular blood pressure). It closes tightly to prevent blood from flowing back from the right ventricle to the right atrium (when ventricular blood pressure > atrial blood pressure).
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Tricuspid valve regurgitation
When blood flows backward form the right ventricle back into the right atrium.
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Atrioventricular valve
Valve between the atria and ventricles.
Atrial blood pressure > ventricular blood pressure → atrioventricular valves open to allow blood flow
Atrial blood pressure < ventricular blood pressure → atrioventricular valves close to prevent blood backflow
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Right ventricle
1 of 4 cardiac chambers, it receives deoxygenated blood from the right atrium, and pumps it to the lungs to get oxygenated.
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Pulmonary valve
3 thin flaps of tissue (each tissue flap is called a “cusp” or “leaflet”) between the heart’s right ventricle and pulmonary artery. It opens to let blood flow from the right ventricle to the pulmonary artery, and closes tightly to prevent blood from flowing back from the pulmonary artery to the right ventricle.
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Left atrium
1 of the 4 cardiac chambers. It receives oxygenated blood from the lungs via the pulmonary vein and pumps this into the left ventricle.
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Bicuspid valve (a.k.a. mitral valve)
An atrioventricular valve with 2 thin flaps of tissue (each tissue flap is called a “cusp” or “leaflet”) between the heart’s left atrium and left ventricle. It opens to let blood flow from the left atrium to the left ventricle. It closes tightly to prevent blood from flowing back from the left ventricle to the left atrium.
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Left ventricle
1 of the 4 cardiac chambers. It receives oxygenated blood from the left atrium and pumps this to the rest of the body through the aorta.
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Aortic valve
3 thin flaps of tissue (each tissue flap is called a “cusp” or “leaflet”) between the heart’s left ventricle and aorta. It opens to let blood flow from the left ventricle to the aorta, and closes tightly to prevent blood from flowing back from the aorta to the left ventricle.
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Aorta
Main, largest artery in the body that carries oxygenated blood from the heart’s left ventricle to the respiring body parts. (O2 needed for respiration).
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Ascending aorta
Part of the aorta that sends oxygenated blood to the head, neck, chest, and arms.
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Descending aorta
Part of the aorta that sends oxygenated blood to the lower body.
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Pericardium
Fluid-filled, membranous sac surrounding the heart. It provides mechanical protection and lubrication for the heart as well as big vessels to reduce friction between them and surrounding structures.
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Chordae Tendinae
Thin strands of connective tissue that anchor the leaflets or cusps of each atrioventricular valve so they cannot open their flaps into the atrium but only in towards the ventricle → prevents unwanted back flow/regurgitation of blood from the ventricle to the atrium, instead of from the atrium to the ventricle
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Papillary muscles
Muscles attached to atrioventricular valves via the ventricular chordae tendinae, prevents valves from opening when ventricles contract to push blood out.
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Coronary artery
Artery on the heart (branching from the base of the aorta across the heart) that transports oxygenated, nutrient-rich blood away from the left ventricle to the myocardium (heart muscles)
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Myocardium
Middle, muscular layer constituting the heart’s walls.
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Coronary vein
Veins on the heart that transport deoxygenated, nutrient-depleted blood away from the myocardium (heart muscles) to the right atrium.
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… can become damaged or diseased often due to the accumulation of … containing … (a fatty substance) or due to ... Healthy … should have a … lining and allow …