Circulatory Systems Flashcards
(90 cards)
1
Q
What are the important functions of the circulatory system?
A
- distribution of nutrients
- support for metabolism (O2 delivery + transportation of metabolic waste)
- distribution of water and electrolytes
- transportation and distribution of hormones
2
Q
What type of current does open circulatory systems use?
A
Water currents in open circulatory systems help transport nutrients and provides fresh water - cilia is used for this purpose
3
Q
What are the 4 key principle components of a circulatory system?
A
- a fluid that circulates through the system (bulk flow and pressure differences/gradient)
- a propulsive mechanism that drives the fluid flow by applying a force
- a system of tubes or channels through fluid can flow
- can be a system of valves or septa that ensure unidirectional flow of fluid
4
Q
What is an open circulatory system? Is it efficient?
A
- fluid is open to body cavities + cells
- most molluscs, arthropods and annelids
- lower pressure system so less efficient
5
Q
What is a closed circulatory system? is it efficient?
A
- fluid is enclosed within the system and does not contact cells directly
- all vertebrates, cephalopod molluscs and some annelids
- higher pressure system so more efficient
6
Q
What are the key features of closed circulation, what bathes cells and what is a key difference?
A
- complete and continuous circulation of blood vessels
- fluid in vessels is blood
- hearts propel blood through vessels
- intercellular spaces filled with insterstitual fluid (composition differs from blood)
- lymph in lymphatic vessels
- key distinction is blood remains in vessels and therefore separates from cells of the body
7
Q
What is an open circulatory system and what bathes cells?
A
Incomplete system of vessels
- circulating fluid, known as haemolymph
- flows freely, percolating interceller spaces
- hearts may propel haemolymph
-haemolymph bathes directly in the cells
- insects use tracheal system to transport CO2
- circulation can be less effiecnt when respiratory gases are handled through a separate system
8
Q
Where does diffusion occur in closed circulation systems?
A
Diffusion occurs between blood vessels and interstitial fluid at the capillary beds.
9
Q
What is the sequence of vessels from greater arteries to greater veins?
A
Greater arteries, arteriole branches, arterioles, capillaries, venules, Venus branches, greater veins
10
Q
What is a ‘pump’? What are ‘distribution’ vessels?
A
Pump - anatomy of the heart varies/number of chambers and arrangement of inflow/outflow vessels
Distribution vessels - circulation patterns vary - single/double
11
Q
What are the requirements of an efficient circulatory system?
A
- efficient O2 carriers (protein/cells) in the blood
- efficient gas exchange in the respiratory system
- efficient delivery of nutrients and O2
- diversification of oxygenated fluids to systemic organs and deoxygenated fluids to respiratory organs, fast flow of fluids
- efficient gas exchange in tissues (o2 in/ Co2)
12
Q
What are the 2n important functions of circulation in mammals?
A
Thermoregulation (blood flow, internal temp)
Immune system infrastructure (fight infection)
13
Q
How is flow rate measured? How does the values differ between closed circulatory system and open circulatory systems?
A
Flow rate = deltaP/R
P = driving force
R = resistance
Closed circulatory system: deltaP high, R low
Open circulatory systems: deltaP low, R high
- both systems can maintain high flow rates
14
Q
Briefly outline the circulatory systems in humans?
A
- 4 chambered heart (uni-directional flow)
- pulmonary circulation runs in series
- blood supplies to systemic vascular beds runs in parallel (high pressure system)
Heart - (systemic arteries) - body - (systemic veins) - heart - (pulmonary arteries, low oxygen CO2 rich blood) - lungs - (pulmonary veins, oxygen rich, low CO2 blood) - heart
15
Q
What is cardiac output and the equation for it? (Including units?)
A
Cardiac output is the total volume of blood pumped by the heart in 1 minute
Cardiac output (L/min)= heart rate (beat/min) x stroke volume (mL/beat)
Human = 70bpm x 70mL = 4.9 l/min
16
Q
How does cardiac output change during extreme exercise?
A
Heart has to be able to adapt relative to respiratory system, reserves are necessary for maximum efficiency
17
Q
Name the key features of the heart?
A
- superior vena cava
- sino atrial node
- left atrium
- bundle of his
- bundle branches
- left ventricle
- papillary muscle
- chordae tendinae
- purkinje fibres
- right ventricle
- atrioventricular node
- right atrium
18
Q
What is meant by ‘myogenic’?
A
- the heart if myogenic (has its own electrical potential)
19
Q
What does an ECG wave form represent?
A
Represents the sum of electro activity
PQRST
P-R = depolarisation of atria
QRS = depolarisation of ventricles
ST = re polarisation of ventricles
20
Q
What systems can modify heart rate?
A
- autonomic system (sympathetic + parasympathetic)
- circulating hormones
- parasympathetic stimulation slows HR
- sympathetic/adrenergic stimuli on accelerates HR
21
Q
How does calcium play a key role in contraction of the heart?
A
- the heart if a functional syncitum
- ca2+ has a central function acts as a trigger for contraction when it enters the cell
- excitation causes contraction
- slight lag time between action potential nad contractile force
22
Q
How does coordinated electrical activity generate coordinated contractile activity?
A
- contraction is highly organised
- atria contract followed by ventricles
- relaxation is also coordinated to allow filling
23
Q
How do valves ensure one way flow of blood?
A
Atria contract and eject blood into relaxed ventricles
- AV valves close as ventricle contracts
- aortic and pulmonary valves open to allow blood out of ventricle
24
Q
What are the 2 main phases of the cardiac cycle?
A
Systole : contraction of chamber and ejection of blood
Diastole: relaxation and filling
*valves ensure one way flow of blood
25
What are the 5 main vents of the cardiac cycle?
1) atrial systole (ventricular diastole)
2) isovolumic contraction of ventricles (ventricular systole)
3) ventricular ejection
4) Isovolumic relaxation of the ventricles
5) passive ventricular refilling
26
What 2 things modify stroke volume?
- Intrinsic control (degree of stretch of cardiac muscle - starlings law)
- extrinsic control (sympathetic stimulation - modulation of calcium availability)
27
Where do arteries and veins travel to and from?
Arteries: travel away from the heart (usually carry oxygenated blood)
Veins: travel towards the heart (usually carry deoxygenated blood)
28
What is the position of the heart in humans? What is it protected by?
In humans, the heart is located -
- posterior (behind) the sternum
- within the mediastinium of the thorax (chest) between the right and left lungs
- orientated with the apex (top) pointing to the left (causing smaller left lung)
- superior (above) the diaphragm
- great vessels (entry+exit) leave the heart at its superior aspect
- protected by several layers of the pericardium
(Which keeps the heart and great vessels in place)
29
What is Starlings law?
- increased ventricular filling causes an increase in the force of contraction of the ventricular muscle
- stroke volume increase with venous return
30
What are the functions of the pericardium?
- anchor the heart in place
- prevent overexpansion
- provide lubrication to permit free movement
- limit potential spread of infection
31
What is the superior vena cava?
Drains blood from upper limbs and from head and neck, returning blood to heart
32
What is the aorta?
Largest blood vessel where blood is being injected out into the systemic circulation (thicker because of high pressure)
33
What is the phrenic nerve?
Supplies the diaphragm with action potential impulses that causes contraction
34
What is situs invertis?
Organs of the body are flipped (so heart is on right etc, 1 in 10,000 people)
35
What are the 2 additional important feathers of the right atrium?
1) the sino atrial node - responsible for generating electrical activity to stimulate contraction
2) Fossa ovalis - the ruminant of a hole (foramen ovale) in the inter-atrial septum during foetal development)
36
What are the key functions of coronary arteries and veins? Potential problems?
- main function is drainage
- supplies the myocardial muscle with a good supply of oxygen (coronary = crown)
- thrombi (clots) in these vessels are the predominant cause of myocardial infarction. With relatively few interconnections (anastomoses) between these vessels, the myocardium is quickly vulnerable to ischaemia and necrosis without adequate blood supply
- the left anterior descending coronary artery is a common site of blockage
37
What does the right atrium have and where does it receive blood from?
The right atrium has a thin wall and receives blood from -
- he head, neck, thorax and upper limbs via the superior vena cava (blood from the coronary circulation also enters here via the coronary sinus
- the trunk, pelvis and lower limbs (plus nutrient rich blood draining the gastrointestinal system) via the inferior vena cava (ICV) (nutrient rich-blood from the gastrointestinal system is also brought to the IVC by the portal circulation)
38
What does the right ventricle have and what does it do?
The right ventricle has a thick wall and recieves blood form the right atrium
- the right ventricle ejects blood into hte pulmonary trunk, which pumps blood towards the lungs for reoxygenation
- the tricuspid valve is an atrioventricular valve (AV) located between the right atrium and the right ventricle
- the pulmonary valve is a semilunar valve (SL) located between the right ventricle and the pulmonary trunk
39
What does the left atrium have and what does it recieve?
The left atrium has a thin wall and recieves blood from 4 pulmonary veins - 2 from each lung
40
What does the left ventricle have and what does it receive?
The left ventricle has a very thick wall and receives blood from the left atrium
- the left ventricle ejects blood into the thoracic aorta, which pumps blood across the systemic circulation
- the mitral (or bicuspid) valve is an atrioventricular (AV) valve located between the left atrium and right ventricle
- the aortic valve is a semilunar (SL) valve located between the left ventricle and the aorta.
41
What are the chordae tendinae?
Attach to muscles in ventricles to the cusps of the valves (stringy structures)
- extend from papillary muscles to the leaflets of the 2 AV valves and prevent the backflow of blood during systole
42
What is the process of valvular regulation?
- atrial depolarisation
- conduction down bundle of His and purkinje fibres
- ventricular depolarisation
- papillary muscles depolarise and contract
- chordae tendinae pulled under tension
- AV valves pulled shut despite high pressure in ventricle
- blood cannot backflow into atria
- blood ejected through open SL valves
- similarly closure of the SL valves prevents backflow of blood into the ventricles
43
What sounds does blood make if there is a problem?
Blood makes a whooshing noise instead of lub-dub when there is turbulence or regurgitation or backflow through veins
44
What are the 3 layers of the heart and their function?
Endocardium - lining (connective tissue based)
Myocardium - muscle layer
Epicardium - visceral pericardium
45
What are cardiac muscle fibres?
- cardiac muscle fibres comprise rows of cells with one or two centrally located nuclei linked end to end via intercalated discs
- these cells can branch and join other fibres
46
What are the 3 types of cell-cell junctions that link the heart muscle cells at intercalated discs?
1) Adherens junctions - link the actin cytoskeleton to allow sarcomere contraction
2) Desmosome - link intermediate filaments to provide strength
3) Gap junction — link cytosol to allow cell-cell communication
47
How many blood vessels are there in he human body? What are the 3 key components that make up blood vessels?
1) Endothelium (1 cell thick)
2) Smooth muscle (support and structure)
3) connective tissue
48
From head to toe, what are the 6 important blood vessels in the body?
- common carotid artery (neck)
- subclavian artery (below the clavical)
- brachial artery (arm in Latin)
- radial artery (wrist)
- abdominal aorta (abdomen)
- femoral artery (femurs, thighs)
49
What are the 3 layers surrounding blood vessels?
Tunica intima
Tunica media
Tunica adventitia
50
What is the tunica intima? (TI)
Endothelial cell layer plus connective tissue (basement membrane) in contract with lumen
51
What is the tunica media (TM)? What is it bordered by?
- smooth muscle cells and connective tissue
- much thicker in arteries than in veins
- bordered by distinctive inner boundary (internal elastic lamina) and outer boundary (external elastic lamina) made of elastic fibres
52
What is tunica adventitia (TA)?
Connective tissue
53
Compare tunica media in aorta and superior vena cava?
- aorta has thicker tunica media (higher pressure)
- superior vena cava has thinner tunica media
Key distinguishable features
54
What does the tunica intima have and what does this do?
The tunica intima comprises endothelium and underlying basement membrane
- endothelium lines the entire cardiovascular system
- regulates passage of substance in and out of the body by permitting transfer between vessels and their surroundings
- being a very thin layer (usually one cell thick), endothelial cells provide a minimal barrier from 1 side to the other
- JC - junctional complex
55
What are the 3 types of junctions between endothelial cells?
Endothelial cells form a one-cell thick layer interconnected by several junctional complexes including -
- tight junction
- adherens junction
- gap junction
* the tight junction in particular has an important role in sealing the para-cellular space between 2 adjacent epithelial cells
56
What is tissue fluid?
Tissue fluid is exchanged across the endothelium-
- a filtrate of plasma that bathes cells
- is drained by the lymphatic system
- blood exchanges materials with tissue fluid then cells access that fluid
57
What do the smooth muscle cells of the tunica media facilitate, how do they do this?
The smooth muscle cells of the Tunica Media facilitate the dynamic regulation of vessel diameter and therefore blood flow and resistance
- smooth muscle cells are spindle shaped (long and thin with a thicker middle)
- have a circular (rather than longitudinal) arrangement, wrapping around the vessel
- contract = vessels contricted - vasoconstriction
- relax = vessels dilated - vasodilation
58
What is an abdominal aortic aneurysm?
Leads to rupture
Chronic overstretching of the distal abdominal aorta
59
Describe the aorta and pulmonary trunk in their relation to being elastic arteries?
- wide lumen
- very thick walls with a thick tunica media
- large amounts of elastic fibres (for stretch + recoil) and collagen to prevent overexpansion
- incorporate vasa vasorum into their tunica adventitia to provide oxygen to the smooth muscle cells in the vessels themselves because media is too thick for diffusion of oxygen
60
What are muscular arteries and what do they feature?
- all other named arteries are known as muscular arteries (good examples include radial artery, carotid artery and brachial artery)
- feature a thick tunica media of smooth muscle to manage high arterial pressure
- smooth muscle cells orientated in a circular not longitudinal direction
61
What are arterioles?
End arteries, found just before entrance to capillary beds
- small vessels, approx 100um in diameter (bigger is an artery, smaller is a capillary)
- smooth muscle cells orientated circularly and wrap around vessel
- smooth muscle wrapping around entrance to capillary beds act as a sphincter, regulating blood flow
- pressure needs to be high enough to push blood through capillaries but not high enough that they rupture
62
What are capillaries?
Capillaries are thin, fragile blood vessels forming a dense, tight network known as a capillary bed
- these are the principal sites of exchange between blood and tissue fluid
- their diameter is smaller than the diameter off an erythrocyte - which is why enucleation is helpful
63
What is the order of vessels from the heart back to the heart?
Heart
Elastic arteries
Muscular arteries
Arterioles
Capillaries
Venules
Veins
heart
64
What are sinusoids and where are they found?
Sinusoids are specialised, widened capillaries that can permit a greater passage of erythrocytes-
- found in bone marrow, spleen, lymph nodes and liver
65
What are the 3 different types of capillary endothelium?
Continuous
- most capillaries
- solutes, gases
Fenestrated
- capillaries in endocrine glands
- larger molecules (hormones)
Discontinuous
- sinusoids
- RBCs/WBCs
66
What are venules?
Permit the exit of deoxygenated blood from capillary beds
- pressure is lower so a thick tunica media is not needed
- although predominantly occurring in capillary beds, fluid exchange also occurs in venules
67
What are veins?
Named veins are responsible for collecting deoxygenated blood from venules and returning it to the heart via the vena cavae
- have a thinner tunica media than arteries but often a wider lumen
- with limited pressure to return blood to the heart, valves are used to promote unidirectional flow
68
What are varicose veins?
Issues with valves/ pooling blood
69
What does increasing the pressure on a vessel do?
Increasing pressure on a vessel can gently squeeze the vein and push blood against gravity
- artery adjacent
- vein adjacent
70
What is the blood brain barrier?
The regulation of substances into and out of the brain needs to be tightly regulated. The interface between blood in capillaries and the tissue of the brain parenchyma is known as the blood brain barrier
71
What features does the blood brain barrier have?
The blood brain barrier comprises several features to create a highly selective barrier into the brain, including -
1) A strong, continuous endothelium
2) Specialised (very tight) tight junction between endothelial cells
3) The presence of additional cell barriers including astrocytes and pericytes
72
What is transendothelial migration?
Cancer cell metastasis across a blood brain barrier is a serious issue in breast and lung cancers
73
What is the study of haemodynamics?
Pressure, resistance and flow in the circulation
74
What are the 2 key features of any circulation system?
- system of fluid filled vessels containing blood or haemolymph
- heart(s) propels blood through vessels
75
What is blood (or haemolymph) pressure?
Difference between the pressure in the system and the ambient pressure (transmural pressure)
76
What are the 2 components of blood or haemolymph pressure?
Dynamic pressure produced by the pump
Hydrostatic pressure of the fluid in columns
77
What is the equation for flow rate (Q)?
Flow rate (Q) = deltaP /R
Pressure gradient/ resistance
78
What is the equation for resistance (R)?
R = 8nL / Pi r^4
8 x fluid viscosity x vessel length / vessel radius
79
What can changes in smooth muscle tone lead to?
- vasoconstriction (contraction)
- vasodilation/vasodilatation (relaxation)
80
What is meant by ‘resistors in series’?
Connected in a single path
- the resistance of the whole system equals the sum of individual resistances of all elements
- adding more resistors increases the total resistance of the system
81
What is meant by ‘resistance in parallel’?
Connected along multiple paths
- adding more resistors decreases the total resistance of the system
82
What are the key functions of arteries?
- conduit for blood capillary beds
- act as pressure reservoir to drive blood into arterioles
- damp oscillations in pressure + flow
- control differential distribution to different organs and tissues
83
What are the key functions of veins?
- conduit for blood to return to heart
- act as a blood reservoir
- flow influenced by external factors
84
What are the 2 intrinsic control factors of smooth muscle tone?
Neurotransmitters
- eg noradrenaline, acetylcholine
Hormones
- adrenaline, vasopressin, atrial natiuretic peptide
85
What are the 4 factors of intrinsic control of smooth muscle tone?
Endothelium derived substances
Metabolites and related factors
- hypoxia, h+ and CO2
Other locally produced factors
- histamine, prostaglandin
Other factors
- pressure, heat
86
What is the distribution of blood in the circulatory system controlled by? Where is the greatest change is pressure?
- vasoconstriction and vasodilation of arteries regulate and distribute blood flow to different organs and tissues
- greatest resistance lies in arterioles (sudden drop in capillaries)
87
What do the numbers mean in blood pressure?
In blood pressure, the high number is the systolic number and the heart is contracted and the low number is the diastolic pressure when the heart is relaxed
88
What does an arterial pulse pressure wave look like?
Pulse pressure - difference in troph and peak value
Peak value is systolic pressure
Troph pressure is diastolic pressure
Notch in peak value caused by closure of aortic valve
89
What are the 2 components of blood or haemolymph pressure? What does pressure increase in proportion to?
- dynamic pressure produced by the pump
- hydrostatic pressure of the fluid in vessels
Pressure increases in proportion to the height (h) of the fluid column
90
What are the effects of gravity on arterial pressure?
- above the heart, arterial pressure decreases with height
- below the heart, fluid-column effects increase the arterial pressure
- blood pools in legs veins when upright - Venus return is compromised
