Circulatory System Flashcards
How does plasma contribute to homeostasis of the body
Maintaining optimum pH of blood through buffers
Maintaining water potential of blood: Blood solutes affect water potential and is largely due to presence of sodium ions and plasma proteins. Regulates movement of water between blood and tissues.
Maintains temperature of the blood as water in the blood plays a part in distribution of heat
What is the function and adaptations of red blood cells
Functions to transport oxygen and carbon dioxide
Adaptations:
Presence of haemoglobin
Circular, flattened biconcave disc shape
No nucleus
Elastic and can turn bell-shaped
Why are red blood cells elastic
In order to squeeze through blood vessels smaller than itself in diameter without breaking
Function of white blood cells
Function to protect the body against disease-causing organisms
Shape and functions of phagocytes
Irregular in shape with lobed nucleus so it can move, changes shape and squeezes through capillary walls
Function: Engulf and ingest foreign particles by phagocytosis
Phagocytosis is process of engulfing and ingesting foreign particles. In process of fighting bacteria, phagocytes are killed with bacteria forming pus.
Shape and functions of lymphocytes
Round in shape, large nucleus
Function: When pathogens or disease causing organisms enter bloodstream, they stimulate lymphocytes to produce antibodies to protect body against bacteria by:
Agglutination, causes bacteria to clump together and attract phagocytes to engulf clump bacteria by phagocytosis. Antibodies neutralise toxin produced by bacteria
Describe platelets
They function to prevent excessive blood loss from body and entry of pathogens, either by formation of platelet plug or initiating blood clotting. They are small cell fragments without nucleus
Importance of blood clotting
Seals the wound to prevent entry of bacteria and further loss of blood
Describe blood clotting
When blood vessels are damaged, damaged tissue and platelets produce thrombokinase which converts prothrombin into thrombin(enzyme). Thrombin converts soluble fibrinogen into insoluble fibrin threads that trap red blood cells and whole mass forms a clot or scab
How does body prevent excessive blood clotting
Undamaged blood vessels contain anti-clotting substance called heparin. When thrombokinase is released in damaged tissues, it neutralises heparin so clotting can take place
Why is blood typing important
If the wrong type of blood is transfused, this would cause agglutination(binding of antibodies in recipients plasma to antigens on donated RBCs) or clumping of red blood cells and could lead to death as clumps may block small blood vessels and prevent flow of blood. Red blood cells become cross-linked to one another and trigger immune system to rupture RBCs and released haemoglobin may cause kidney damage
Why is blood group O universal donor
There are no antigens on donor’s red blood cells and thus recipients antibodies would not cause agglutination of donor’s blood
How is blood typing done (using anti-A serum)
If blood agglutinates when serum is used, RBCs contain antigen A
Why is there a need for transport system
In simple unicellular organism, movement of materials in and out of cell occurs by diffusion as no part of cell is far from external environment
In multicellular organism, transport system is needed to carry materials from one part of the body to another, as cells are located deep in body far from external environment
What are advantages of double circulation
Complete separation of oxygenated and deoxygenated blood in double circulation
Blood passes through heart twice in one complete circuit: pulmonary circulation at lower pressure and systemic circulation at higher pressure
Describe reason for complete separation of oxygenated and deoxygenated blood in double circulation
Ensures only oxygenated blood reach tissue cells. Efficiency of transport of oxygenated blood
Describe reason for blood passing through heart twice in one complete circuit
Blood enters lung at lower pressure compared to blood leaving the heart. This ensures blood flows slowly at lungs, allowing sufficient time for blood to be well oxygenated before it returns to heart.
Systemic circulation has higher pressure so oxygenated blood is distributed to rest of body tissues more quickly. Helps to maintain high metabolic rate in animals
Describe following for artery:
Structure
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow
Thick, elastic muscular wall. Semi-lunar valves absent except in pulmonary artery and aorta
Small lumen relative to diameter of blood vessel
High blood pressure
Blood flows rapidly, pulses reflecting rhythmic beating action of heart
Flows away from heart to organs
Describe adaptations of artery
Function: Transport blood away from heart
Arterial wall can withstand high pressure generated by contraction of ventricles
Elastic tissue in wall enables it to stretch and recoil under high pressure. Helps to push blood in spurts along artery and give rise to pulse
Muscular tissue in wall allows for constriction and dilation to regulate volume of blood flowing through
When artery constricts/dilates, lumen becomes narrower/wider and less/more blood flows through it per unit time
Describe following for arteriole:
Structure
Function
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow
Elastic and muscular walls, arteries branch to form arterioles
Transports blood away from heart
Small lumen
Lower blood pressure than artery
Blood flows slower compared to arteries
Flows from heart to organs
Describe following for capillary:
Structure
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow
Capillary wall is one-cell thick, single layer of endothelial cells and intercellular clefts
Very small lumen
Blood pressure falls along capillaries due to increase in total cross-sectional area
Blood flows slowly to allow more time for exchange of substances to take place
Flows around cells within organs
Describe function and adaptation of capillary
Allow for exchange of nutrients and waste between blood and tissue fluid
One-cell thick wall allows oxygen, food and waste products to easily diffuse through walls
Presence of intercellular clefts increase rate of diffusion of materials
Extensive network surrounding cells enable efficient exchange of materials with tissue cells
Describe following for venule:
Structure
Function
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow
Thin and elastic muscular wall
Delivers blood to vein
Large lumen
Very low blood pressure
Blood flows slowly
Flows from organs towards heart
Describe following for vein:
Structure
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow
Thinner elastic and muscular wall, semi-lunar valves present except vena cava and pulmonary vein
Large lumen
Very low blood pressure
Blood flows slowly, skeletal muscles next to veins assist flow of blood back to heart by compressing veins when muscle contracts
Describe function and adaptations of vein
Transports blood towards the heart
Large lumen offers low resistance to blood flow - blood can flow smoothly back to heart
Semi-lunar valves prevent the backflow of blood under low blood pressure to ensure flow of blood in one direction
Describe transfer of materials between capillaries and tissue fluid
Tissues and cells surrounded by fluid that supplies cells with requirements - tissue fluid. Fills intercellular spaces and acts as medium for materials to diffuse between blood and cells of body
For materials to get into cells, must diffuse into tissue fluid before diffusing into cells
Where are pulmonary artery, pulmonary vein, aorta and vena cava located
Pulmonary vein -> left ventricle -> aorta
Vena cava ->right ventricle -> pulmonary artery
Describe ventricular systole
Ventricles contract, pressure rises and pressure of blood pushes av valves upwards forcing them shut. This produces ‘lub’ sound. Pressure in ventricles higher than aortic/pulmonary artery pressure, semi-lunar valves open, blood in ventricles enter aorta/pulmonary artery
(Addition of atrial diastole)
Atria relaxes and blood from pulmonary vein/vena cava starts filling the atria
Describe ventricular diastole
Ventricles relax, pressure within chamber falls, resulting in back flow of blood from aorta/ pulmonary artery towards the ventricles. Blood starts to flow backwards and closes the semi-lunar valves, this produces ‘dub’ sound. As ventricles continue to relax, pressure falls quickly. When ventricular pressure drops below atrial pressure and atria contracts to force remaining blood through open AV valves into ventricles
Define blood pressure
Blood pressure is force that blood exerts on the walls of blood vessels.
Describe pulse
When ventricles contract, blood is pumped into aorta and into arteries. Sudden increase in pressure causes arteries to dilate. Following dilation, arterial walls recoil, forces the blood to move along in series of waves. This gives rise to pulse.
Describe coronary heart disease
Condition of cholesterol and fatty deposits on inner surface of coronary arteries called atherosclerosis. Plaque narrows lumen of arteries, resulting in less oxygen and nutrients supplied to heart muscles. When coronary arteries are completely blocked, myocardial infarction may result. heart tissue does not get oxygen and nutrients, tissue dies, resulting in damage to heart. Infarction may disrupt the conduction system of the heart and cause sudden death to patient. May experience agina (pain/discomfort in region of heart with insufficient blood)
Factors increasing risk of heart attack
Family history
Being male
Age
Smoker
High intake of saturated fats/sugar/alcohol
Lack of exercise
High blood pressure
