Circulatory systems Flashcards
(135 cards)
1
Q
What are the main functions of a circulatory system?
A
Distribution of nutrients, support for metabolism, distribution of water and electrolytes and transportation and distribution of hormones.
2
Q
What are the four principal components of a circulatory system?
A
A fluid that circulates, a propulsive mechanism that drives fluid, a system of tubes/channels and a system of one way valves or septa to ensure unidirectional flow.
3
Q
What are the two general types of circulation?
A
Open circulation system and closed circulation system.
4
Q
What are the characteristics of an open circulatory system?
A
Fluid is open to body cavities and cells, most molluscs/arthropods, lower pressure, less efficient.
5
Q
What are characteristics of a closed circulatory system?
A
Fluid enclosed within the system and does not contact cells directly, all vertebrates, higher pressure, more efficient.
6
Q
In what branch of the evolutionary tree do open and closed circulations occur?
A
On the same branch.
7
Q
What are primary features of an open circulation?
A
Incomplete system of vessels, fluid known as haemolymph, flows in vessels and freely through intercellular spaces, heart may propel through vessels.
8
Q
What does haemolymph do?
A
Bathes the internal organs and therefore directly reaches every cell of the body.
9
Q
What are characteristics of open circulation in insects?
A
Use tracheal systems to transport nutrients and CO2, circulation less efficient when respiratory gases are handled through separate system.
10
Q
What are the primary features of a closed circulation?
A
Complete and continuous vessels, fluid in blood, heart propels, intercellular spaces filled with interstitial fluid, lymph in lymphatic vessels.
11
Q
Where does diffusion occur in closed circulation?
A
Between blood vessels and interstitial fluid at capillary beds.
12
Q
What two things can vary in closed circulatory systems between species?
A
Pump (anatomy of the heart) and distribution vessels (circulation patterns).
13
Q
What are the main requirements of an efficient circulatory system?
A
Efficient O2 carriers in blood or haemolymph, efficient gas exchange, efficient delivery of nutrients and O2, efficient gas exchange in tissues.
14
Q
What are two ways of maintaining efficient delivery of nutrients and O2?
A
Diversification of oxygenated fluids to systemic organs and deoxygenated fluids to respiratory organs, fast flow of fluids.
15
Q
What’s the equation for flow rate?
A
changeP/ R (driving force/resistance).
16
Q
What’s the equation for resistance in regards to blood vessels?
A
8nL/pie x r^4
17
Q
How does driving force and resistance change based on closed and open systems?
A
Closed = high changeP and high R, whereas open = low changeP and low R.
18
Q
What can both systems maintain a high rate of?
A
High flow rates.
19
Q
What are functions of the mammalian cardiovascular system?
A
Distribution of O2 and nutrients, transportation of CO2 and removal of waste products, distribution of water electrolytes and hormones, thermoregulation, immune system infrastructure.
20
Q
What is the arrangement of the mammalian cardiovascular system?
A
Four-chambered heart, blood supplies to systemic vascular beds run in parallel, pulmonary circulation runs in series, high pressure system.
21
Q
What does the heart provide?
A
Force.
22
Q
What is the heart composed of?
A
Vena cava, pulmonary arteries, pulmonary trunk, pulmonary veins, atriums, tricupsid valve, ventricles, chordae tendinae, aorta, mitral valve, aortic valve, pulmonary valve, papillary muscle, interventricular septum, myocardium.
23
Q
What do blood vessels offer?
A
Resistance.
24
Q
What is cardiac output?
A
The total volume of blood pumped by the heart in one minute.
25
What is the equation for cardiac output?
CO(L/min) = HR(heart rate beats/min) x SV(stroke volume L/beat).
26
What generates the rhythm of the heart?
The heart generates its own spontaneous rhythm.
27
What do ECG waveforms represent?
Electrical activity in the whole heart.
28
What are the five areas of an ECG waveform?
PR interval, P wave, QRS complex, T wave, QT duration.
29
What is the PR interval of an ECG waveform?
Conduction through AV node.
30
What is the QT duration of an ECG waveform?
Ventricular depolarisation and repolarisation.
31
What is the P wave?
Depolarisation of atria.
32
What is the QRS complex?
Depolarisation of ventricles.
33
What is the T wave?
Repolarisation of ventricles.
34
What is heart rate modified by?
Autonomic nervous system and circulating hormones.
35
What slows and what accelerates HR respectively?
Parasympathetic stimulation and sympathetic/adrenergic stimulation.
36
What organ is a functional syncitium?
The heart.
37
What does functional syncitium mean?
Individual cells that maintain their identity but work together as a whole to complete necessary function.
38
What causes contractions in the heart?
Excitation.
39
What is EC coupling in cardiac myocytes?
The process that links the electrical excitation of the cell membrane (action potential) to the mechanical contraction of the heart muscle.
40
What do valves ensure?
One-way flow of blood.
41
What are the four valves of the heart?
Right side = pulmonary valve, tricuspid valve and left side = mitral valve, aortic valve.
42
What are the two phases of the cardiac cycle?
Systole and diastole.
43
What is systole?
Contraction of chamber and ejection of blood.
44
What is diastole?
Relaxation and filling.
45
What are the five events of the cardiac cycle?
Atrial systole, isovolumic contraction of ventricles, ventricular ejection, isovolumic relaxation of ventricles, passive ventricular refilling.
46
What two things is stroke volume modified by?
Intrinsic control (degree of stretch of cardiac muscles) and extrinsic control (sympathetic stimulation).
47
In what direction to arteries usually travel in and what do they carry.
Travel away from heart, usually carry oxygenated blood.
48
In what direction do veins usually travel and what do they carry?
Travel towards the heart, usually carry deoxygenated blood.
49
What organism has the smallest and which has the biggest heart?
Pygmy shrew has smallest, blue whale has biggest.
50
Where is the heart located in humans?
Posterior to sternum, within mediastinum of thorax between left and right lungs, orientate with apex left (left lung smaller), superior to diaphragm.
51
Where do arteries and veins leave and enter the heart?
At its superior aspect.
52
What is the heart protected by?
Several layers of pericardium which keeps the heart and great vessels in place.
53
What does the pericardium’s several layers function to do?
Anchor heart in place, prevent overexpansion, provide lubrication to permit free movement, limit potential spread of infection.
54
What external features of the heart can be seen?
Aorta, pulmonary trunk, coronary vessels.
55
What does the coronary arterial circulation provide?
Oxygen rich blood to the myocardium.
56
What can cause myocardial infarction and ischaemia/necrosis?
Thrombi in coronary vessels, relatively few interconnections between them, quickly vulnerable.
57
What area of the coronary arteries is a common site of blockage?
Left anterior descending coronary artery.
58
What kind of wall does the right atrium have?
A thin wall.
59
Where does the right atrium receive blood from?
The head, neck, thorax, upper limbs via superior vena cava, trunk pelvis and lower limbs via the inferior vena cava.
60
Where does blood from the coronary circulation enter the heart?
At superior vena cava via the coronary sinus.
61
What brings nutrient rich blood from the gastrointestinal system to the IVC?
Hepatic portal vein.
62
What is the Sino-atrial node in the right atrium?
Responsible for generating electrical activity to stimulate contraction.
63
What are the fossa ovalis in the right atrium?
The remnant of a hole in the inter atrial septum during foetal development.
64
What kind of wall does the right ventricle have?
Thick wall.
65
Where does the right ventricle receive blood from?
The right atrium.
66
What does the right ventricle do?
Ejects blood into pulmonary trunk which pumps blood towards the lungs for reoxygenation.
67
What are the two valves in the right ventricle and where are they located?
Tricuspid valve (AV, between atrium and ventricle), pulmonary valve (semilunar located between ventricle and trunk).
68
What wall does the left atrium have and where does it receive blood from?
Thin wall, blood from pulmonary veins.
69
What wall does left ventricle have and where does it receive blood from?
Thick wall, left atrium.
70
What is the role of the left ventricle?
Ejects blood into thoracic aorta which pumps blood across the body.
71
What are the two valves of the left ventricle?
Mitral/bicuspid (AV, between atrium and ventricle), aortic valve (SL, between ventricle and aorta).
72
What are the chordae tendinae (heartstrings)?
Extend from papillary muscles to leaflets of two AV valves and prevent backflow of blood during systole.
73
What is the passage of atria depolarisation during valvular regulation?
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, blood cannot flow to atria, blood ejected through open SL valves.
74
What does closure of SL valves prevent?
Backflow of blood into ventricles.
75
What are the three layers of the heart?
Endocardium (lining), myocardium (muscle), epicardium (visceral pericardium).
76
What are cardiac muscle fibres comprised of?
Row of cells with one or two centrally located nuclei linked end to end via intercalated discs.
77
What are the three types of cell-cell junctions that link the heart muscle cells at intercalated discs?
Adherens (actin cytoskeleton to allow sarcomere contraction), demosomes (intermediate filaments), gap junctions (cytosol to allow cell-cell communication).
78
What are four key components of vascular anatomy?
Common carotid artery, subclavian artery, abdominal aorta, brachial artery.
79
How many miles of blood vessels are there in the human body?
60,000 miles.
80
What three components do blood vessels always have?
Endothelium, smooth muscle, connective tissue.
81
What is the structure of the blood vessels described as histologically?
As having three concentric layers known as tunica.
82
What are the three concentric tunica layers of the blood vessels?
TI - tunica intima, TM - tunica media, TA - tunica adventitia.
83
What is the TI?
Endothelial cell layer plus connective tissue (basement membrane) in contact with lumen.
84
What is the TM?
Smooth muscle cells and connective tissue, much thicker in arteries than in veins, bordered by a distinctive inner boundary (internal elastic lamina) and outer boundary (EEL) made of elastic fibres.
85
What is the TA?
Connective tissue.
86
What blood vessels do not have all the tunica layers?
Smallest vessels - capillaries and sinusoids.
87
What kind of tunica media does the aorta have vs the superior vena cava?
Thicker vs thinner.
88
What is the endothelium lining?
Lines entire cardiovascular system, regulates passage of substances in and out by permitting transfer between vessels and surroundings, very thing layer (one cell), minimal barrier from one side to other.
89
What is tissue fluid?
Exchanges across endothelium, a filtrate of plasma that bathes cells, drained by lymphatic system, exchanges material with blood then cells access fluid.
90
What junctional complexes interconnect the one cell thick layers that endothelial cells form?
Tight junctions, Adherens junction, gap junctions.
91
What does the tight junction have a particular, important role in?
In sealing the intercellular space between two adjacent endothelial cells.
92
What do the smooth muscle cells of the tunica media facilitate?
The dynamic regulation of vessel diameter and therefore blood flow and resistance.
93
What are smooth muscle cells like?
Spindle shaped (long and thin with a thicker middle).
94
What kind of arrangement do smooth muscle cells have?
Helical rather than longitudinal, wrapping around the vessel.
95
What happens when smooth muscle cells contract?
Vessels are constricted - vasoconstriction.
96
What happens when smooth muscle cells are relaxed?
Vessels are dilated - vasodilation.
97
What is abdominal aortic aneurysm?
Chronic overstretching of the distal abdominal aorta.
98
What arteries are large elastic arteries?
The aorta and pulmonary trunk.
99
What are the characteristics of elastic arteries?
Wide lumen, very thick walls with a thick tunica media, large mounts of elastic fibres and collagen to prevent overexpansion.
100
What do elastic arteries incorporate into their tunica adventitia to provide oxygen to the smooth muscle cells in the vessel themselves?
Vasa vasorum.
101
What are muscular arteries and their characteristics?
Other named arteries like radial, carotid, brachial, feature thick tunica media of smooth muscle to manage high arterial pressure, smooth muscle cells orientated in circular not longitudinal direction.
102
What are arterioles?
End arteries, found before entrance to capillary beds, approx 100um in diameter.
103
What are characteristics of arterioles?
Smooth muscle cells orientated circularly and wrap around vessel, wrapping around entrance to beds act as a pump regulating blood flow, pressure high enough to get through capillaries, low enough to not rupture.
104
What are capillaries?
Thin, fragile blood vessels forming a dense tight network known as capillary bed, principal site of exchange.
105
What are sinusoids?
Specialised, widened capillaries that can permit a greater passage of erythrocytes, found in bone marrow, spleen, lymph nodes, liver.
106
What are the three types of capillary endothelium?
Continuous, fenestrated, discontinuous.
107
What is the continuous endothelium?
For solutes and gases, found in arterioles.
108
What is fenestrated endothelium?
Larger molecules, capillaries in endocrine glands.
109
What is discontinuous endothelium?
Found in sinusoids.
110
What are venules and what do they do?
Permit exit of deoxygenated blood from capillary beds, pressure lower so thick TM not needed, also fluid exchange here.
111
What are veins responsible for?
Collecting deoxygenated blood from venules and returning it to heart.
112
What are characteristics of veins?
Thinner tunica media than arteries but often wider lumen, limited pressure to return to heart, valves to promote unidirectional flow.
113
What causes varicose veins?
If valves weaken and become incompetent as blood can pool in the veins leading to distension.
114
What does increasing pressure on vessels do?
Can gently squeeze the blood superiorly against gravity in a stepwise way - adjacent arteries/ muscles.
115
What is deep vein thrombosis?
Blood pooling in deep veins that can become prone to clotting - dangerous condition.
116
What is the blood brain barrier and why is it important?
Interface between blood and tissues of brain parenchyma - regulation of substances into and out brain needs to be tightly regulated.
117
What are the several features that create a highly selective barrier into the brain, composing the BBB?
A strong endothelium, specialised tight junctions between endothelial cells, presence of additional cell barriers including astrocytes and pericytes.
118
What is the blood/haemolymph pressure?
Difference between pressure in system and ambient pressure.
119
What are the two components of the blood or haemolymph pressure?
Dynamic pressure produced by pump, hydrostatic pressure of fluid.
120
What is the resistance of the whole system in series?
Equals the sum of the individual resistances of all elements.
121
What are resistors in series?
Connected in a single path.
122
What does adding more resistors do in series?
Increases the total resistance of the system.
123
What are resistors in parallel?
Connected along multiple paths.
124
What is the total conductance of the system in parallel?
Sum of conductances of individual elements.
125
What does adding more resistors do in parallel?
Decreases the total resistance of the system.
126
What are the functions of arteries?
Conduit for blood to capillary beds, act as pressure reservoir to drive blood into arterioles, damp oscillations in pressure and flow, control differential distribution to different organs and tissues.
127
What are the functions of veins?
Conduit for blood to return to heart, act as blood reservoir, flow influenced by external factors.
128
What do changes in smooth muscle tone lead to?
Vasoconstriction and vasodilation.
129
What can alter smooth muscle tone?
Neurotransmitters, hormones, endothelium derived substances, metabolites and related factors, other locally produced factors (histamine), other factors (pressure/heat).
130
What does vasoconstriction and vasodilation of arteries do?
Regulate and distribute blood flow to different organs and tissues.
131
Where does the greatest resistance lie?
In the arterioles.
132
What is total fluid energy?
Potential energy acquired from beating of heart, kinetic energy of fluid itself, potential energy of fluid that it possesses because of position in gravitational field.
133
Where does the fluid flow from and to?
Fluid flows from where its total fluid energy is higher to where its total fluid energy is lower.
134
What are two components of blood/haemolymph pressure?
Dynamic pressure produced by the pump, hydrostatic pressure of fluid.
135
What happens to arterial pressure above and below heart?
Above - pressure decreases with height, below - fluid column effects increase in pressure.
