Circulatory System Flashcards
What does double circulatory system mean?
Blood goes thru the heart twice for each complete circuit of the body
What are the two circuits that get blood pumped thru?
Pulmonary
Systematic
What size is the pulmonary circuit and what is the adv of its pressure?
Relatively small and pumped at low pressure
Allows blood to pass rel slowly thru capillaries in lungs allowing more time for g.e
What does high pressure of systematic circuit ensure?
Higher pressure ensures blood is pumped to all organs in body at pressure sufficient to deliver metabolites and remove waste
Also, pressure maintains blood/tissue fluid balance in each organ
Describe the structure of artery:
Thick wall: outer thin layer of fibrous tissue with thick middle layer of smooth muscle and elastic tissue with inner layer of squamous endothelium
Narrow Lumen
Rounded Shape
What is the blood pressure of the arteries like?
High in pulses
What does elastic tissue in arteries allow?
Allows stretch and recoil as blood pulses out of heart thru arterial syst following contr of ventr muscles
What does elastic tissue recoil help?
Helps push blood along artery maintaining blood pressure
What is the function of muscle tissue in arteries?
Provides support but also can constrict (vasoconstrict)/ dilate (vasodil) prov >/< blood to an organ
What is function of contr of muscle and narrowing of lumen in artery?
Helps maintain bp
What is the blood pressure like in veins?
Low
Descr the str of the veins:
Thin wall- outer layer of fibrous tissues, thin middle layer cont some muscle- v little elastic tissue with an inner layer of squamous endothelium
What is adv of large lumen in veins?
Little res to blood flow- essential as low bp in veins
What are the functions of the valves?
Prev backflow of blood.
How does amount of muscle tissue in veins compare to arteries?
Much less in veins
What is the function of the squamous endothel on inner layer?
Creates smooth surface reducing friction as blood flows thru
Describe the structure of capillaries?
Microscopic vessels with one cell thick walls consisting of squamous endothelium
What is adv of small size of cap?
Allows ext netw of cap, prov lsa for dif of mat (no cell far from a cap)
What is adv of thin wall of cap?
Fac. exch. of mat with surr cells and tissues thru being permeable to water and solutes and provides a short dif dist
Referring to graph descr blood from aorta to arterioles:
Remains at high pr thru aorta and arteries- still close to heart
Pulse effect in bp unmatched by pulse in blood vel due to smoothing effects of elastic and muscle tissue in art wall
What causes red in pressure between aorta and arteries?
As main arteries branch into large no. smaller arterioles increases csa
What is the cause of the reduction in pressure between caps and veins?
Facilitates exchange of mat between blood and surr tissue fluid as blood flows from cap
Why does pressure reduce when blood leaves cap?
Overall csa of bv decrease as cap unite-> venules-> veins
What does the large lumen in each vein ensure?
Ensures friction between blood and wall of vein is reduced to ext blood vel can increase even tho bp is still low
What sep two sides of heart?
Septum
Why are atria rel thin?
B/c removes blood from lungs (LA)/ body (RA) and pumps blood to ventr (directly below them)
Why is LV thicker than RV?
Lungs only few cm from heart so RV doesnt pump as far and with force LV has to pump blood around the body
What is function of atrioventricular valve?
Tricuspid and bicuspid: lie between atria and ventr and prevents backflow of blood into atria when ventr contract
What is function of semilunar (arterial valves)?
Lie at base of aorta and pulm artery and prev backflow of blood from arties to ventricles
What is the funct of the papillary muscles?
Anchor AV valves and they are embedded in ventricle wall
What is the funct of the chordae tendinae?
Link muscle and valves
What are the adaptations of the c.tendinae?
Extremely tough and flexible- not elastic
Ensures when ventr contract ( with high pressure in ventr forcing AV valves shut), prev valves turning inside out which would allow blood to flow back to atria
What is the funct of the semi-lunar valves?
Pocket valves in artery walls only close when bp in arteries less than bp in veins
Descr the function of the aorta:
Major art carrying ox blood out of LV
Art. branch leading from aorta carry blood to all major organs of bod except lungs
Descr function of pulm artery:
Carries deox blood from RV -> Lungs
Descr function of Vena Cava:
Brings deox blood back from body returning blood to RA
Descr function of Pulm Vein:
Transp ox blood from lungs -> LA
What are the functions of the CA?
Branch off aorta shortly after it leaves heart and travels over heart muscle continually supplying metabolic needs
What are the atria like in diastole?
Atrial walls relaxed
Blood enters atria from venae cavae and pulm vein
What are the ventr like in diastole?
Ventr walls also relaxed and semilunar valves closed as arterial pressure > ventric- prevents backflow of blood back to ventr
As AV valves open, blood enters ventr from atria
What are atria like in atrial systole?
Atrial walls contract forcing more blood in ventr
AV valves remain open as pressure in atria still greater than ventr pressure
Blood continues to enter atria from VC and pulm vein
What are ventr like in atrial systole?
Walls of ventr remain relaxed
Ventr vol cont to increase- fill with blood
Semilunar valves remain closed
What are atria like in ventricular systole?
Atrial walls relax
What are the ventr like in ventricular systole?
Ventric walls contract
AV valves close as ventr pressure > atrial pressure
Chordae tendinae prev AV valves blowing inside out
As ventr pressure reaches its peak, semilunar valves forced open forcing blood into arteries
By end of ventric systole, ventr at smaller vol
What does myogenic mean?
Heart can beat on its own and doesnt req external stimulation
Where does the process of the heartbeat start?
Starts with el signal orig from area of muscle in wall of RA called sinoatrial node (SAN)/ pacemaker
What does the SAN do?
Sends out a wave of el. act. over atria causing contraction (atrial systole)
Wave of el.act. travels rapidly causing atria to contract simultaneously
What is found between atria and ventr- what does this do?
Layer of non-conductive tissue- prev wave of excitation passing directly thru to ventr
What is the only way el activ passes thru to ventr? What does this lead to?
Via AV node that conducts v slowly. Thus, contraction in ventr (ventr systole) is delayed rel to atria
What does delay in ventr systole ensure?
Ensures when ventric systole begins atrial systole is complete and ventr are filled with blood
How does el. act. pass down septum of ventr?
In special tissue called Bundle of His to bottom of the ventr
What does el. act. in B.O.H cause?
Stim. spreads up thru walls of ventr in special tissue called Purkinje fibres, causing contraction of ventr walls and forcing blood up thru arteries (ventric systole)
What are cell fragments imp in?
Imp role in clotting process and in repairing minor breaks in bv
What is the funct of plasma?
Transp blood cells, gluc and aa, and other products of dig, ions carbon d, urea, heat, prothromb, fibrinogen and clotting factors etc
How are RBC ad for role in Number?
about 5 million in each mm3 of blood
How are RBC ad for role in small size?
haem mol close to cell surf to aid diffusion- makes it easier to flow thru narrow capillaries
How are RBC ad for role in shape?
High sa/v ratio due to biconcave shape
How are RBC ad for role in having no nucl/organelles?
More room for haem
How are RBC ad for role in having haemoglobin?
to carry 02. Being in RBC affect Wp of blood less and makes it less viscous
Also more can be packed in than dissolved in plasma
Descr WBC vs RBC
WBC larger than RBC with a nucleus
Much less numerous
Descr polymorphs (microphages):
Most common- 70 %
They have distinctive multi-lobed nucl and granular cytoplasm
Phagocytic- can pass between squamous epithel cap cells and destroys bact and other foreign bodies by phagocytosis at sites of inf
Descr monocytes
Largest but least common WBC (5%)
Bean shaped nucleus
Phagocytic and move out of blood at sites of inf and dev in phagocytic macrophage cells which destroy bacteria and other foreign material
Longer lived than polymorphs
Descr lymphocytes
around 20-25% of WBC
v large nucleus leaving only a small amount of cytoplasm
2 cells inv:
B-cells- inv in antibody prod
T- cells: inv in cell mediated immunity (destroying inf and foreign cells)
What is tissue fluid imp in?
Prov stable env for cells
and osmoreg of cells
and fac transp of subst between blood and body cells
How is hydrostatic pressure created?
As blood travels thru arties, the arterioles and then into arterial end of cap netw, narrowing of vessels creates this
What is hydr pressure strong enough to do?
Strong enough to force l. and small mol out of cap
What 2 forces oppose hydrostatic pressure?
- low Wp blood due to presence of plasma proteins that tends to pull tissue fluid back by osmosis
- hydrostatic pressure of tissue opposes inward flow of l. from cap.
At which end of the cap netw does hydrostatic pressure of blood exceed these 2 forces: What does this result in?
At arterial end
Liquid rich in oxygen and other materials are filtered out of blood and into tissue fluid that bathes the cells
Oxygen, glucose and other mat then enters cells by diffusion
How does tissue fluid get back into cap?
L. filtered out at arterial end returned to cap after tissues supplied with essential metabolites
Why does tissue fluid return to cap?
Loss of fluid from capillary causes red in hydrostatic pressure and by the time the blood reaches venule end, hydrostatic pressure of tissue fluid > hydrostatic pr of blood
What is the return of the tissue fluid aided by?
Aided by dif in Wp between blood in cap and tissue fluid
Why is conc grad reduced at venule end?
Much of filtered l has returned
What is the function of blood clotting?
Reduces blood loss and prevents entry of pathogens
Descr the clotting process:
Insoluble fibrin forms a mesh that traps BC to form a clot-> a scab is formed as it dries which prevents blood loss and entry of microbes
What is blood clotting process aided by?
As soon as bv damaged vasoconstricts reduces blood flow to damaged area
What happens immed when damage to tissue/ bv present?
Platelets activ rel. clotting fibres inc. thromboplastin (thrombokinase) which can form a plug to seal minor damage/ reduces rate of blood loss if greater damage
What is req for the conversion of Prothrombin to Thrombin?
Ca ions, Vit K, Factors VIIA and Xa (clotting factors)
What is converted after prothrombin to thrombin?
Fibrinogen -> Fibrin
What is an atheroma?
Build up of fatty deposits that form within wall of artery
What is an atheroma caused by?
Smoking, l/o exercise, > salt and high blood chol levels
What is step 1 in the dev of an atheroma?
Squamous end cells that line artery lumen bec damaged- can be caused by toxins in blood from tobacco some/ high bp that applies greater force on the artery walls
What is step 2 in the dev of an atheroma?
Following dam to endothelial lining, atheroma builds up w/i wall of artery (beneath endothelium)
What is step 3 in the dev of an atheroma?
Macrophages (having dev from moncytes) migrate from blood into dam artery wall and inv in accum of mat w/i wall partic chol inc dead muscle cells, salts and fibrous tissue
In due course, atheroma builds up into hardened plaques
What is step 4 in the dev of an atheroma?
As they increase in size and toughness atheromas (plaques) bulge into lumen of artery that restricts blood flow
Fibrous mat causes artery to bec less elastic and less able to reg blood flow thru vasodil/ vasoconstr
Hardening and narrowing of arteries increases bp causing further atheromas and plaques to form
What is atherosclerosis?
Caused by thickening of artery wall thru dev of atheromas and plaques
Artery wall bec less elastic, artery lumen narrower and increase in bp
What is thrombosis?
Form of blood cots within bv
When is thrombosis partic problematic?
In narrow art i.e C.A arteries narrowed as result of heart disease
More likely to happen if artery wall bed damaged i.e atheroma/atherosclerosis
What happens if coronary thrombosis occurs?
Area of heart affected fails to receive blood: oxygen and glucose for resp and cells die if blockage prolonged
What happens if a large area of the heart is affecred (i.e near origin of CA rather than tip)?
myocardial infarction ( heart attack)
How does an angiograph work?
Contrast dye which will show up on angiograph imaging is added to blood via thin tube (catheter) that is inserted into bv until reaches part of bod under inv. so contrast agent placed only where needed]
What can an angiograph identify?
Extent of bv narrowing, blockage or damage
