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What is the primary function of arteries in the circulatory system?
Which statement accurately describes the structure of veins?
What is the main purpose of capillaries in the circulatory system?
In a closed circulatory system, how many times does blood pass through the heart for every circuit of the body in a double circulatory system?
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What role do arterioles play in the circulatory system?
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What is tissue fluid primarily composed of?
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How does hydrostatic pressure affect the movement of blood fluid in the circulatory system?
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Which component of blood helps in the exchange of nutrients and reducing friction in arteries?
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What causes water to move from the tissue fluid to the blood?
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Which component of the lymphatic system helps filter out bacteria and foreign material?
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What is the primary function of the lymph fluid?
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What initiates the contraction of the heart?
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What happens during atrial systole?
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What role does the atrioventricular node play in the cardiac cycle?
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What is true about the blood compared to tissue fluid?
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What happens to the tissue fluid that is not reabsorbed into the capillaries?
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What happens during ventricular systole?
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How does haemoglobin release oxygen?
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What is the primary role of the semilunar valves during cardiac diastole?
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What determines the affinity of haemoglobin for oxygen?
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Which part of the cardiovascular cycle describes the relaxation phase of the heart?
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How many oxygen molecules can one haemoglobin molecule carry?
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What process occurs when oxygen binds to haemoglobin in the lungs?
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What occurs to the heart's pressure during the elastic recoil phase?
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What distinguishes a double circulatory system from a single circulatory system?
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Which structure is primarily responsible for the metabolic exchange of substances?
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What is a key characteristic of veins in the circulatory system?
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How does hydrostatic pressure influence the movement of blood fluid in capillaries?
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What role do valves in veins serve within the circulatory system?
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What is the primary function of tissue fluid in the circulatory system?
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Which of the following correctly describes the structural adaptation of arteries?
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What primarily causes the movement of fluid back into the capillaries from the tissue fluid?
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What characterizes the tissue fluid in relation to blood regarding water potential?
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What is the primary purpose of the lymphatic system?
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Which structure initiates the electrical wave that triggers heart contraction?
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What is the result of the electrical wave reaching the atrioventricular node?
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During which stage of the cardiac cycle do the atrioventricular valves open?
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What is the role of Purkyne fibres in the cardiac cycle?
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What is true about the lymph fluid compared to tissue fluid?
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How does the myogenic nature of the heart contribute to its function?
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What happens to the atrioventricular valves during ventricular systole?
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What is the effect of increased partial pressure of oxygen on haemoglobin?
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How does cardiac diastole affect the heart chambers?
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What role do semilunar valves play during cardiac diastole?
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What occurs to haemoglobin after it releases oxygen in respiring tissues?
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How many oxygen molecules can a single haemoglobin molecule carry?
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What is the effect of respiratory processes on the partial pressure of oxygen?
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How does the affinity of haemoglobin for oxygen change as oxygen is used in tissues?
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Study Notes
Circulatory Systems
- Circulatory systems can be open or closed.
- Open circulatory systems are found in insects, where blood is not always contained in vessels.
- Closed circulatory systems are found in fish and mammals, where blood remains within blood vessels.
- Single circulatory systems have a heart with two chambers, and blood passes through the heart once per circuit of the body.
- Double circulatory systems have a heart with four chambers, and blood passes through the heart twice per circuit of the body.
Blood Vessels
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Arteries carry blood away from the heart.
- They have thick walls to withstand high blood pressure.
- They contain elastic tissue for stretching and recoiling, smoothing blood flow.
- They contain smooth muscle to control blood flow.
- They have a smooth endothelium to reduce friction.
- Arterioles are smaller branches of arteries, with thinner, less muscular walls. They feed blood into capillaries.
- Capillaries are the smallest blood vessels, where metabolic exchange occurs. They are only one cell thick for rapid exchange.
- Venules are larger than capillaries but smaller than veins.
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Veins carry blood back to the heart.
- They have a wide lumen to maximize blood volume.
- They have thin walls because blood pressure is low.
- They contain valves to prevent backflow of blood.
- They have little elastic tissue or smooth muscle, as there is no need for stretching or recoiling.
Tissue Fluid
- Tissue fluid is a liquid containing dissolved oxygen and nutrients, supplying tissues and removing waste products like carbon dioxide.
- It is formed due to hydrostatic pressure from blood being pumped through arteries and capillaries.
- Only small molecules can pass through capillary walls into the tissue fluid, like dissolved nutrients and oxygen.
- Osmotic pressure pushes some tissue fluid back into the capillaries.
- The lymphatic system collects excess tissue fluid and returns it to the bloodstream.
Lymphatic System
- The lymphatic system contains lymph fluid, similar to tissue fluid.
- Lymph fluid has less oxygen and nutrients than tissue fluid, but it carries waste products.
- It contains lymph nodes, which filter bacteria and foreign material from the fluid.
- Lymphocytes within lymph nodes destroy invaders as part of the immune system.
Mammalian Heart and Cardiac Cycle
- The heart is myogenic, meaning it can initiate its own contractions.
- The sinoatrial node (SAN) in the right atrium acts as the pacemaker, initiating electrical stimulation that makes the atria contract.
- The atrioventricular node (AVN) passes the excitation to the ventricles via the bundle of His and Purkyne fibres.
- The cardiac cycle has three stages:
- Atrial systole: Atrial contraction forces blood into the ventricles.
- Ventricular systole: Ventricular contraction closes atrioventricular valves and opens semilunar valves, allowing blood to leave the heart.
- Cardiac diastole: Atria and ventricles relax, blood is drawn back into the heart, and semilunar valves close to prevent backflow.
Haemoglobin
- Haemoglobin is a water-soluble globular protein with two alpha and two beta polypeptide chains, each containing a haem group.
- The haem group binds oxygen, allowing haemoglobin to carry oxygen in the blood.
- Each haemoglobin molecule can carry four oxygen molecules.
- Haemoglobin's affinity for oxygen varies depending on the partial pressure of oxygen.
- Higher partial pressure (more oxygen) increases affinity, leading to oxygen binding in the lungs (loading).
- Lower partial pressure (less oxygen) decreases affinity, leading to oxygen release in tissues (unloading).
- Dissociation curves show the relationship between haemoglobin saturation and partial pressure of oxygen.
Circulatory Systems
- Open circulatory system: found in insects. Blood is not confined to blood vessels.
- Closed circulatory system: found in fish and mammals. Blood is always contained within blood vessels.
- Single circulatory system: Blood passes through the heart once per circuit of the body. The heart has two chambers.
- Double circulatory system: Blood passes through the heart twice per circuit of the body; the heart has four chambers.
Blood Vessels
-
Arteries: carry blood away from the heart.
- Thick walls to withstand high pressure.
- Contain elastic tissue, which allows stretching and recoil to smooth blood flow.
- Contain smooth muscle to vary blood flow.
- Lined with a smooth endothelium to reduce friction and ease blood flow.
- Arterioles: branch off from arteries. Thinner, less muscular walls. Feed blood into capillaries.
- Capillaries: smallest blood vessels. Site of metabolic exchange. One cell thick for fast exchange of substances.
- Venules: larger than capillaries, but smaller than veins.
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Veins: carry blood towards the heart.
- Wide lumen to maximize blood volume.
- Thin walls because blood is under low pressure.
- Contain valves to prevent backflow of blood.
- Lack of pulse means little elastic tissue or smooth muscle.
Tissue Fluid
- Liquid containing oxygen and nutrients.
- Supplies tissues with essential solutes and collects waste products (e.g., carbon dioxide).
- Enables exchange of substances between blood and cells
- Formed due to hydrostatic pressure from blood flow in arteries, arterioles, and capillaries. This pressure forces fluid out of capillaries.
- Contains small molecules that can pass through capillary walls (e.g., oxygen, dissolved nutrients).
- Also influenced by osmotic pressure which draws some fluid back into the capillaries.
- Tissue fluid is less negative in water potential compared to blood. This leads to osmosis of water from tissue fluid to blood.
Lymphatic System
- Carries excess tissue fluid back to the circulatory system.
- Contains lymph fluid, similar to tissue fluid, but less oxygen and nutrients and more waste.
- Contains lymph nodes which filter bacteria and foreign material from the fluid with the help of lymphocytes.
Mammalian Heart
- Myogenic: Initiates its own contractions.
- Sinoatrial node (SAN): acts as the pacemaker of the heart. Located in the right atrium.
- Atrioventricular node (AVN): located between the atria. Passes the electrical excitation to the ventricles.
- Bundle of His: conducts the electrical wave to the apex of the heart.
- Purkyne fibres: carry the wave upwards, causing ventricular contraction.
Cardiac Cycle
- Atrial systole: atria contract, forcing blood into the ventricles.
- Ventricular systole: ventricles contract, shutting the atrioventricular valves and opening the semilunar valves, pushing blood out to the aorta (left ventricle) and pulmonary artery (right ventricle).
- Cardiac diastole: atria and ventricles relax. Elastic recoil lowers pressure in heart chambers, drawing blood from arteries and veins. Semilunar valves close to prevent backflow.
Haemoglobin
- Water-soluble globular protein.
- Consists of two alpha and two beta polypeptide chains, each containing a heme group.
- Heme group contains Fe2+ which binds to oxygen.
- Each haemoglobin molecule can carry four oxygen molecules.
- Affinity of haemoglobin for oxygen varies with partial pressure of oxygen.
- Loading: In the lungs, high partial pressure of oxygen leads to higher affinity of haemoglobin for oxygen.
- Unloading: In respiring tissues, low partial pressure of oxygen leads to lower affinity of haemoglobin for oxygen.
- Dissociation curves: illustrate the relationship between partial pressure and haemoglobin saturation.
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Description
This quiz covers the fundamentals of circulatory systems, including the differences between open and closed systems, as well as the structure and function of various blood vessels like arteries and capillaries. Test your understanding of how blood circulates in different organisms and the features of circulatory pathways.
