Blood Vessels and Circulation Flashcards
(93 cards)
1
Q
Arteries
A
Carry blood away from the heart
2
Q
Arterioles
A
Smallest artery branches leading to capillaries
3
Q
Capillaries
A
Where diffusion between blood and interstitial fluid takes place
4
Q
Venules
A
Unite to form larger veins that return blood to heart
5
Q
Path of blood
A
Heart > arteries > arterioles > capillaries > venules > veins > heart
6
Q
Where does blood leave the heart through?
A
Pulmonary trunk (right ventricle) > pulmonary arteries > lungs
Aorta (left ventricle) > systemic arteries > all other organs
7
Q
Vessel wall structure in arteries and veins
A
- Tunica intima
- Tunica media
- Tunica externa
8
Q
Tunica intima
A
- Inner layer
- Endothelial lining and a surrounding layer of connective tissue with a variable number of elastic fibres
- Thick layer of elastic fibres (internal elastic membrane) in arteries
9
Q
Tunica media
A
- Middle layer
- Concentric sheets of smooth muscle tissue in a framework of loose connective tissue
- Typically thickest layer
- Smooth muscle cells encircle endothelium that lines the lumen
10
Q
What separates tunica media and tunica externa?
A
External elastic membrane
11
Q
Tunica externa
A
- Outer layer
- Connective tissue sheath
12
Q
Vasa vasorum
A
Blood vessels in the walls of large vessels
13
Q
Why do large vessels contain vasa vasorum?
A
Because the vessel walls are too thick for diffusion
14
Q
Differences between arteries and veins
A
- Artery walls thicker
- Arteries keep shape in sectional view
- Arteries have folds in sectional view
- Veins have valves
15
Q
3 main types of arteries
A
- Elastic
- Muscular
- Arterioles
16
Q
What gives arteries their elasticity and contractility?
A
Thick, muscular walls
17
Q
Vasoconstriction
A
When stimulated, arterial smooth muscles contract, constricting the arteries
18
Q
Vasodilation
A
When arterial smooth muscles relax, the diameter of the lumen increases
19
Q
What do vasoconstriction and vasodilation affect?
A
- Afterload on heart
- Peripheral blood flow
- Capillary blood flow
20
Q
Elastic arteries
A
Pulmonary trunk and aorta and their major branches
21
Q
Muscular arteries
A
Distribute blood to the body’s skeletal muscles and internal organs
22
Q
Arterioles
A
Smaller than muscular arteries
23
Q
Resistance vessels
A
Arterioles
24
Q
Aneurysm
A
Bulge in the weakened wall of an artery
When local blood pressure exceeds the capacity of the elastic component of the arterial walls
25
Types of capillaries
1. Continuous capillaries
2. Fenestrated capillaries
3. Sinusoids
26
Continuous capillaries
- The endothelium is a complete lining of the lumen
| - Tight junctions and desmosomes connect endothelial cells
27
Fenestrated capillaries
Contain pores in the wall due to an incomplete or perforated endothelial lining
28
Sinusoids
Discontinuous endothelium
29
Capillary bed
Interconnected collective network
30
Precapillary sphincter
Surrounds the entrance of a capillary and controls arterial blood flow to the tissues
31
Thoroughfare channel
Central passageway in the arteriole system
32
What happens when a precapillary sphincter constricts?
Blood is diverted into other branches of the network
33
Collaterals
Multiple arteries that supply blood to a capillary bed
34
Arterial anastomosis
The fusion of two collateral arteries that supply an arterial bed
35
Arteriovenous anastomoses
Direct connections between arterioles and venules
36
What happens when an arteriovenous anastomosis is dilated?
Blood bypasses the capillary bed and flows directly into venous circulation
37
Angiogenesis
Formulation of new blood vessels from preexisting vessels
38
Vascular endothelial growth factor (VEGF)
Directs angiogenesis
39
Types of veins
1. Venules
2. Medium sized veins
3. Lagre veins
40
Venules
- Smallest veins
| - Collect blood from capillary beds
41
Medium sized veins
Similar in size to muscular arteries
42
Large veins
Includes superior and inferior venae cavae and their branches within the abdominopelvic and thoracic cavities
43
Venous valves
In limbs, in venules and medium sized veins
44
What makes up valves?
Folds of the tunica intima
45
Varicose veins
Occurs when valves weaken or become stretched, blood pools in the veins
46
Which vessels are capacitance?
Veins
47
Why do veins act as blood resevoirs?
Because they have high capacitance
48
Venoconstriction
If serious hemorrhaging occurs, sympathetic nerves stimulate smooth muscle cells in the walls of medium sized veins in the systemic system to constrict
This decreases the amount of blood within the venous system, increasing the volume within the arterial system and capillaries
49
Capillary hydrostatic pressure (CHP)
Pressure of blood within capillary walls
50
Venous pressure
Pressure of the blood within the venous system
51
Total peripheral resistance
The resistance of the entire cardiovascular system
52
Vascular resistance
The forces that oppose blood flow in the blood vessels
53
What is the most important factor in vascular resistance?
Friction between blood and vessel walls
54
Two factors affecting amount of friction
1. Increasing vessel length increases friction
| 2. Narrower vessel more resistance to blood flow
55
Viscosity
Resistance to flow caused by interactions among molecules and suspended materials in a liquid
More viscous = more resistance
56
Turbulence
Eddies and swirls
57
Systolic pressure
Peak blood pressure measured during ventricular systole
58
Diastolic pressure
Minimum blood pressure at the end of the ventricular diastole
59
Pulse pressure
Difference between systolic and diastolic pressures
60
Mean arterial pressure (MAP)
Diastolic pressure + (pulse pressure/3)
61
Hypertension
Abnormally high blood pressure
62
Hypotension
Abnormally low blood pressure
63
Is hypertension or hypotension more common?
Hypertension
64
Stage 1 hypertension
Systolic: 140-159
Diastolic: 90-99
65
Pre-hypertension
Systolic: 120-139
Diastolic: 80-89
66
Why is there a risk of fainting when knees are locked?
Leg muscles are immobilised and unable to assist pushing blood against gravity back up to heart
67
Respiratory pump
Inhale: thoracic cavity expands, reducing pressure, air enters lungs, blood pushed into inferior vena cava and right atrium
Exhale: thoracic cavity decreases, increasing pressure, air forced out of lungs, blood pushed into right atrium
68
Capillary exchange
Chemical and gaseous exchange between blood and interstitial fluids across capillary walls
69
Filtration
Removal of solutes as a solution flows across a porous membrane
70
Reabsorption
Occurs as the result of osmosis
71
Osmotic pressure (OP)
Pressure that must be applied to prevent osmotic movement across a membrane
72
Bulk flow
The continuous net movement of water out of the capillaries, through peripheral tissues and back to the bloodstream by way of the lymphatic system
73
Forces acting across capillary walls
At the arterial end of the capillary, CHP is greater than BCOP do fluid moves out of the capillary (filtration)
Near the venule, CHP is lower than BCOP, so fluid moves into capillary (reabsorption)
74
Net filtration pressure (NFP)
Difference between net hydrostatic pressure and net osmotic pressure
75
Tissue perfusion
Blood flow through tissues
76
Factors affecting tissue perfusion
1. Cardiac output
2. Peripheral resistance
3. Blood pressure
77
Vasomotion
Changes in vessel diameter
78
Autoregulation
Causes immediate, localised homeostatic adjustments
79
Neural mechanisms
Respond to changes in arterial pressure or blood gas levels senses at specific sites
Short term adjustments to cardiac output and peripheral resistance to maintaining BP
80
Endocrine mechanisms
Hormones that enhance short term adjustments and that direct long term changes in cardiovascular performance
81
Vasodilators
Factors that promote dilation of precapillary sphincters
82
Local vasodilators
Cause the capillary sphincters to relax so blood flow increases to the area when dissolved oxygen concentration decreases within a tissue
83
Cardiovascular (CV) centre
Centre in the medulla oblongata that is responsible for adjusting cardiac output and peripheral resistance to maintain blood flow
84
Vasomotor centre
- In CV centre
- Group of neurons responsible for controlling vasoconstriction
- Group of neurons responsible for controlling vasodilation
85
Cardioacceleratory centre
Increases cardiac output through sympathetic innervation
86
Cardioinhibitory centre
Decreases cardiac output through parasympathetic innervation
87
Baroreceptor reflexes
Monitor the degree of stretch within expandable organs
88
Where are baroreceptors located?
Carotid sinuses, aortic sinuses and right atrium
89
Chemoreceptor reflexes
Respond to changes in oxygen or CO2 levels in blood
90
What triggers chemoreceptor reflexes?
Sensory neurons located in the carotid bodies and the aortic bodies
91
Endocrine mechanisms
1. Antidiuretic hormone - peripheral vasoconstriction and water conservation
2. Angiotensin II - decreases renal BP
3. Erythropoietin - causes vasoconstriction
4. Natriuretic peptides - reduce blood volume and BP
92
Light exercise
1. Extensive vasodilation
2. Venous return increases
3. Cardiac output rises
93
How does exercise lower cholestrol?
By stimulating enzymes that help move LDLs from the blood to the liver where it's converted to bile and excreted
