chapter 7 - the circulatory system Flashcards
function of blood
- transport: oxygen and nutrients to cells, carbon dioxide and waste away from cells
- protection: clotting prevents fluid loss, white blood cells prevent the body against disease
- regulation: helps maintain stable body temperature, pH, water and electrolyte levels
what are the components of blood
- plasma
- formed elements (erythrocytes, leucocytes and platelets)
explain what plasma is
- makes up 55% of blood volume
- 91% of plasma is water
- 9% is made up of dissolved substances (nutrients: monosaccharides, amino acids, fatty acid and glycerol) (gases: oxygen and carbon dioxide) (ions, hormones, wastes, salts)
explain what white blood cells are
- leucocytes
- larger than rbc but there are much fewer
- remove dead or injured cells and invading micro organisms
- live for minutes (infection) to years (no infection)
- granulocytes: have a granular cytoplasm and a lobed nucleus
- monocytes and lymphocytes (spherical nucleus and a-granular cytoplasm)
explain what red blood cells are
- erythrocytes
- biconcave discs (thicker edges - increased volume for haemoglobin molecules) (thinner middle - increases SA for oxygen exchange)
- no nucleus (allows for more haemoglobin for oxygen to attach to)
- produced in bone marrow, destroyed in liver and spleen
- live for approximately 120 days
explain what platelets are
- thrombocytes
- very small cell fragments with no nucleus
- formed in red bone marrow
- important for normal blood clotting
- lasts for approximately 7 days
what are arteries
- carry blood away from the heart (oxygenated except for pulmonary artery)
- contain smooth muscle and elastic fibres, thick and muscular
- walls extend and recoil
- doesn’t contract to pump (reduces diameter of artery wall)
- doesn’t contain valves (high blood pressure)
- vasoconstriction: reduces blood flow to an organ
- vasodilation: increases blood flow to an organ
what are veins
- carry blood towards the heart (deoxygenated except for pulmonary vein)
- do not contain muscle, thin, inelastic walls
- contains valves to prevent backflow (low bp)
- cannot change diameter of the vessel
what are arterioles
- tiny arteries (same characteristics)
- carry blood from arteries to capillaries
what are venules
- tiny veins (same characteristics)
- carry blood away from capillaries to the veins
what are capillaries
- carry blood between the cells
- microscopic blood vessels that form networks
- one cell layer thin (allows for easy exchange of gases and materials)
- carries both oxygenated and deoxygenated
- doesn’t have valves
explain the transport of oxygen
- oxygen is not soluble in water, 3% is dissolved in plasma, 97% is carried in oxyhaemoglobin (oxygen + haemoglobin = HbO2)
- oxygenated blood: high oxyhaemoglobin
- deoxygenated blood: no oxyhaemoglobin
explain the transport of carbon dioxide
- 8% dissolved in plasma
- 22% combined with the globin part of haemoglobin (carbaminohaemoglobin)
- 70% is carried in plasma as bicarbonate ions
- CO2 + O2 –> H2CO3 –> HCO3 (bicarbonate ion)
factors that allow for efficient exchange of gases
- moist
- large surface area
- thin (one cell layer thin)
- networks of capillaries
explain the transport of nutrients and waste
- inorganic nutrients transported as ions (Na, Ca, K, Cl, I)
- organic nutrients required by the body (glucose, amino acids, vitamins, fatty acids and glycerol)
- wastes / metabolic wastes need to be removed (urea, creatinine, uric acid)
what is the cardiac cycle
- a sequence of events that occur during one heart beat (both sides of the heart operate at the same time
- one heart beat is 0.8 seconds
what is systole, atrial systole and ventricular systole
- pumping of blood (muscles contract)
- atria contract, blood is forced into ventricles (0.1 seconds)
- ventricles contract, blood is forced into arteries (0.3 seconds)
what is diastole, atria diastole and ventricular diastole
- filling (muscles relax)
- both atria fill with blood (0.4 seconds)
- ventricles relax (fill with blood) (0.4 seconds)
two things that affect blood flow
- output of blood from the heart (cardiac output)
- diameter of blood vessels supplying the tissues
what is cardiac output
- stroke volume (mL) x heart rate (beats/min)
- stroke volume: volume of blood forced from a ventricle with each contraction
- heart rate: number of times the heart beats per minute
how is cardiac output regulated
- sinistral node (SA node): works as a pacemaker (influenced by the nervous system)
- cardiovascular regulating centre: carries nerve impulses to SA node causing heart rate to speed up or slow down
how is the diameter of blood vessels constricted during blood flow
- vasoconstriction and vasodilation (contraction and relaxation of artery walls to regulate blood flow)
- change of blood flow = change in diameter of blood vessels
how is diameter of blood vessels regulated
- cardiac output and diameter changes of other BV
- factors influencing: cardiovascular regulating centre (brain, CNS) and hormones (adrenaline, epinephrine)
steps that occur to (simple) injury of blood vessels
1 walls of blood vessels constrict 2 reduces blood flow 3 rough surface inside walls 4 platelets stick 5 attract other platelets 6 plug is formed 7 helps reduce blood flow 8 platelets release vasoconstrictors 9 stops bleeding
steps that occur in blood clotting (coagulation), serious injuries to blood vessels
1 clotting factors
2 leads to a series of reactions
3 formation of fibrin (threads of insoluble protein)
4 formation of mesh work
5 trap blood cells, platelets and plasma (clot)
6 clot retraction (occurs slowly)
7 network of threads contract (become closer, denser and stronger)
8 pull edges of damaged BV together
9 serum is squeezed out
10 clot dries / forms a scab
11 prevents entry of micro-organisms
what is the lymphatic system
- network of lymph capillaries joined to lymph vessels and nodes
- function: collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system
what are lymph vessels
- blood leaks out of capillaries due to high blood pressure in arteries
- lymph vessels returns the blood through venous ends (veins) or the lymphatic system
similarities and differences between blood capillaries and lymph capillaries
- BC: circulate and carry blood around the body, smaller and less permeable
- LC: one way only (blind ends), circulates blood away from tissues, larger, more permeable
what area lymph nodes
- occur along lymphatic vessels
- structure: bean shaped (1-25mm), contain lymphoid tissue (macrophages, lymphocytes, plasma cells, crisscrossed network of fibres)
- function: lymph enters through vessels - filters - leaves to next node - eventually drains into blood capillaries
