Vascular Physiology Flashcards
(179 cards)
1
Q
Humans have
A
A closed circulatory system
2
Q
How are vessels that form a continuous space bound?
A
Plasma membranes and basement membranes
3
Q
__carry blood away from the heart
A
Arteries
4
Q
____ carry blood to the heart?
A
Veins
5
Q
What lies between arteries and veins?
A
Capillaries
6
Q
__are the site of material exchange
A
Capillaries
7
Q
What are the three layers that line the walls of veins and arteries?
A
Tunica intimia, tunica media, and tuinca externa
8
Q
What is the tunica intima composed of
A
Endothelium (simple squamous epithelium) Subendothelial layer (basement membrane and loose connective tissue
9
Q
What is tunica media composed of
A
circularly arranged smooth muscle cells
10
Q
What is tunica externa composed of?
A
loose connective tissue with nerves blood vessels (vasa vasorum) and lymphatic vessels
11
Q
How do the walls of veins and arteries differ?
A
Arteries have internal and external elastic lamina on either face of the tunica media
The tunica media in arteries are thicker
Tunica intima of veins folds that extend into the lumen and form valves
12
Q
What are the different types of arteries?
A
Elastic (conducting) arteries
Muscular (distributing) arteries
Arterioles
13
Q
Which type of artery is nearest the heart?
A
Elastic (conducting) artery
14
Q
Which type of artery makes up the bulk of the larger arteries of the body?
A
Muscular (distributing) artery
15
Q
Which type of artery is the smallest?
A
Arterioles
16
Q
Which type of artery feeds directly into capillaries?
A
Arterioles
17
Q
What are the different types of veins?
A
Venules; and Veins
18
Q
Which type of vein allows for the passage of leukocytes?
A
Venules
19
Q
Which type of vein prevents the back flow of blood?
A
Veins
20
Q
What is the smallest vessel?
A
Capillaries
21
Q
Which vessel only consists of Tunica intima?
A
Capillaries
22
Q
What smooth muscle like cells are on the outer wall of the capillary?
A
Pericytes
23
Q
What are the three types of capillaries?
A
Continuous capillaries; Fenestrated capillaries; Sinusoidal capillaries
24
Q
What are the most common type of capillary:
A
Continuous capillaries
25
What do the tight junctions in continuous capillaries do?
They prevent movement of cell sized bodies out of the lumen by active transport
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Where are fenestrated capillaries found?
they are found wherever passive flow of materials out of the capillary is required
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What allow small solutes to move freely in fenestrated capillaries?
Holes or fenestrations
28
Where are fenestrated capillaries found in the body?
Kidneys; Intestines; and Endocrine Organs
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Where are sinusoidal capillaries found?
Wherever protein sized molecules and even cells must permeate the walls
30
Where are the large openings in sinusoidal capillaries found ?
The endothelium and basement membrane
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Where are sinusoidal capillaries found in the body?
In bone marrow; some endocrine glands; the choroid plexi; the liver; and lymphoid organs
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What are the interweaving networks where capillaries are found called?
Capillary beds
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Where do capillaries in a bed arise from?
A single metarteriole that passes through tthe bed (vascular shunt)
34
What are precapillary sphincters?
bands of smooth muscle that can close off the proximal end of each capillary and divert to the shunt
35
What is an anastomosis?
Any arrangement of blood vessels that allows an alternate pathway for blood to take around a blockage.
36
What do arterial anastomoses involve?
alternate supply of organs by arteries
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What are vascular shunts?
arteriovenous anastomoses
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Which type of anastomoses is the most common?
Venous anastomoses
39
What are the physical properties that are the most important to physiology ?
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Blood Flow (F)
Blood Pressure (P)
Resistance (R)
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40
What is blood flow?
The rate at which a given volume of blood flows through a region in a given time
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What is blood pressure?
the force exerted by the blood on a given area of a vessel wall
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What is resistance?
The force exerted that opposes the flow of blood along a given stretch of blood vessels
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What is an important factor in the perfusion of the tissues?
Blood flow
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As perfusion increases the rate at which oxygen and nutrients reaches the tissues ?
increases
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What is equivalent to CO
the systematic flow of blood
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What does blood pressure determine?
how rapidly material exchange across the capillary walls will take place
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What determines the blood flow along vessels?
The difference in blood pressure form one point to the next along a given length of vessels
48
How does fluid flow?
from areas of high pressure to areas of low pressure
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What determines resistance?
Blood Viscosity; Vessel Length; and Vessel diameter
50
What is the main regulator of resistance?
Vessel diameter
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What does vessel length do?
increasing length increases surface area and thus friction between the blood and the wall
52
What is blood viscosity?
the resistance to flow by the fluid itself
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What allows for the diameter of a vessel to change?
Smooth Muscle
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Why is resistance important?
for regulation of local blood flow
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What causes resistance?
Fluid
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When a vessel is dilating what happens to the resistance?
it decreases
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When a vessel is constricting what happens to the resistance?
it increases
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What is the change in blood pressure most important for?
Systematic movement of blood
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When resistance is up flow is
decreased
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When pressure is up flow is
increased
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Why can't blood pressure be high through out the whole system?
because blood will not flow
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Where does blood pressure reach it's maximum ?
In the Aorta
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When does blood pressure reach its maximum?
During the contraction of the left ventricle (Systole)
64
The beating of the heart and the pressure caused by smooth muscle in teh vessel walls are largely irrelevant to what?
The pressure differences in the venous system
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When diastole occurs blood pressure is where?
at its lowest
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When systole occurs blood pressure is where?
at its highest
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What determines arterial blood pressure?
The elasticity of the vessels and the volume of blood forced into them by the heart
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What dampens the pulse of vessels?
its elasticity
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How do you maintain blood pressure?
smooth muscle in the arteries pushes on the blood
70
What is normal for systolic pressure?
120 mm Hg
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What is normal for diastolic pressure?
80 mm Hg
72
What is the difference between systolic and diastolic pressure
Pulse Pressure
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What is the mean arterial pressure
the diastolic pressure plus one third of the pulse pressure
74
Is the capillary blood pressure generally steady?
Yes
75
What is the normal pressure at the arterial end?
35 mm Hg
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What is the normal pressure at the venous end?
15 mm Hg
77
What is an important determinant of fluid flow?
pressure change
78
What is the force behind flow in venous system?
Action of skeletal muscles (muscular pump); and the pressure changes in the thoracic cavity (respiratory pump)
79
What is the rate and direction of flow determined by?
Hydrostatic pressure; colloid osmotic pressure
80
What allows for materials to move faster that what diffusion would normally allow?
Bulk Fluid Flow
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What is hydrostatic pressure?
the pressure of fluid pressing against the vessel wall
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What is Capillary hydrostatic pressure?
the pressure of fluid pressing against the inside wall of the capillary
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What is interstitial hydrostatic pressure?
the pressure of the fluid between the systemic cells pressing against the outside wall of the capillary
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Does HPc and HPif work in the same direction
NO
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What is colloid osmotic pressure?
pressure that results from the osmotic movement of water from areas of low solute concentration to areas of high solute concentration
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What is capillary osmotic pressure?
the force of water moving into the capillary
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What is interstitial osmotic pressure?
the force of water moving into the interstitial space between the systemic cells
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What is the net filtration pressure
the net force acting to move fluid into or out of the capillary
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What is the equation that you should know?
NFP = (HPc - HPif) - (OPc - OPif)
90
Why is OPc always higher than OPif ?
The concentration of protein in plasma is always higher than that in the interstitial space.
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HPc at the arterial end of the bed is ___ than HPif
higher
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HPc at the venous end of the bed is ___ than HPif
lower
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NFP is ___ at the arterial end?
Positive
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NFP is ___ at the venous end?
Negative
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Why does blood flow through different tissues vary?
Metabolic activity of the tissue and other functional requirements
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Blood flow decreases with what?
capillaries
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What does slow flow allow?
It allows gasses and nutrients time to exchange across the capillary walls
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How do tissues control their own blood flow? (autoregulation)
Metabolic controls; myogenic controls; angiogenesis
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What does lack of nutrients or oxygen cause?
endothelial cells to release nitric oxide (NO) a powerful local vasodilator
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What cause vasodilation and leakiness of capillaries?
K+ H+ lactic acid; adenosine; and prostaglandins
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What is the sympathetic nervous system is responsible for?
Vasoconstriction
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What responds to lack of oxygen or nutrients by relaxing?
Precapillary Sphincters
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What responds to increased pressure on the walls by constricting?
Smooth muscles
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What does excess pressure in one area do?
It redirects blood flow to poorly perfused areas
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How is long term deficiency of perfusion corrected?
Growth of numbers and size of vessels
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Where does angiogenesis occur?
The heart
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When does angiogenesis occur
Coronary vessels are occluded and when people living at high altitude and when people are exposed to abnormally high oxygen concentrations (burn victims)
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What areas have special perfusion requirements and regulatory mechanisms?
Skeletal muscles; Brain' Skin; Lungs; heart
109
How much blood flow do resting muscles receive?
25%
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What do exercising muscles do?
they use oxygen and release wast products that increase capillary dilation
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What does sympathetic activation constrict?
vessels in the skin and digestive viscera to redirect flow to muscles
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How are adrenergic controls overridden?
By local controls in the skeletal muscles
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What are neurons intolerant of?
Ishemia
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What is the potent vasodilator in the brain?
Carbon dioxide
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What protects the delicate structures in the brain and how?
Myogenic controls act to dampen fluctuations in the blood pressure in the vessels of the brain to protect delicate structures
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Besides blood flow to the skin supplying cells with nutrients, what else does it do?
Blood flow helps to regulate the temperature of the body and provide a reservoir of blood
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How are temperature reflexes controlled?
In the hypothalamus
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How is heat retained through skin cells?
Vascoconstriction
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How do skin vessels aid in radiating heat?
Vasodilation
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Why is low pressure needed to perfuse lungs?
Because the resistance in pulmonary veins is low
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What is the opposite of the systemic tissues?
Autoregulation mechanisms
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What does low oxygen cause?
constriction in the lungs; redirecting blood to better oxygenated areas
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What does high oxygen cause?
dilation in the lungs; allowing blood to pick up oxygen in high oxygen regions
124
When does blood flow to the heart tissues?
During diastole
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What maintains oxygen during systole?
Myoglobin in heart muscles
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During strenuous exercise what causes vasodilation?
Built up carbon dioxide and lack of oxygen
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How much oxygen delivered in blood do the heart muscles use ?
65%
128
How much oxygen delivered in blood do other tissues besides the heart use ?
25%
129
How is blood flow to the tissues regulated?
Vessel diameter
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What does overall blood pressure needed to do?
Maintain adequate perfusion and capillary hydrostatic pressure
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Does MAP remain constant?
Yes
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What is flow equivalent to? (F)
CO (Cardiac Output)
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How can you regulate blood pressure?
Change CO (cardiac output) (which entails changing the fluid volume) or we can change R (resistance) (which entails changing vessel diameter)
134
What does short term control of blood pressure involve?
Neural Controls and Hormonal controls
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What does neural controls consist of ?
Medullary vasomotor center; Baroreceptors; Chemoreceptors
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What does Hormonal controls consist of?
Adrenal medulla; atrial natriuertic peptide; antidiuretic hormone; angiotensin II
137
What does the vasomotor center in the medulla oblongata control?
Vascular constriction through the sympathetic fibers
138
What does constant low level sympathetic activity produce?
a constant level of constriction known as vasomotor tone
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Where does the vasomotor center receive inputs from?
baroreceptors; chemoreceptors; and higher brain centers
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What are baroreceptors?
stretch receptors that are sensitive to blood pressure changes
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Where are baroreceptors located?
in the cartoid sinus and the aortic arch
142
What do baroreceptors do?
they inhibit the vasomotor center and cause vasodilation and decrease cardiac output by decreasing venous return
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What are chemoreceptors sensitive to?
they are sensitive to changes in oxygen H+ and carbon dioxide
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Where are Chemoreceptors located ?
in the aortic arch and carotid bodies of the neck
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What is the function of Chemoreceptor?
Regulate respiration
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What can lead to sympathetic activation ?
Changes in emotional state regulated by higher brain centers and increase blood pressure
147
What hormones released by the adrenal medulla enhance sympathetic activation and vasoconstriction
Epinephrine and Norepine
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What does generalized vasoconstriction do?
It diverts blood flow the to the skeletal and cardiac muscle and improves venous return and increases cardiac output
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What does increased stretching of the atria stimulate?
Release of atrial natriuetic peptide (ANP)
150
What does Atrial Natriuetic Peptide affect?
Long term blood pressure regulation
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What does Atrial Natriuetic Peptide produce?
Vasodilation and decreasing perpheral resistance
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What does decreasing peripheral resistance do?
It decreases blood pressure
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What does the Antidiuretic hormone (vasopressin) do?
It increases blood volume over the long term and in cases of extreme blood loss to produce intense vasoconstriction to maintain blood flow to the brain and the heart
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What does decreased kidney perfusion cause?
Kidneys to release renin
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What does renin with some extra steps do?
Angiotensin II release
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What is an Angiotensin II ?
Potent vasconstrictor
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What does Angiotensin II do?
Stimulates aldosterone and antidiuretic hormone production which increases blood volume
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Where is long term regulation of blood pressure accomplished?
The Kidneys and by direct influence on the filtration pressure in the glomerulus
159
What does long term regulation involve?
It involves changing blood fluid volume
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What is hypotension?
Low BP in which systolic pressure is below 100 mm Hg
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What is hypertension?
A condition of sustained elevated aterial pressure of 140/90 or higher
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How are transient elevations caused?
Fever, physical exertion and emotional upset
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What is chronic elevation a major cause of?
a major cause of heart failure vascular disease renal failure and stroke
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What is orthostatic hypotension?
temporary low BP and dizziness when suddenly rising from a sitting or reclining position
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What is chronic hypotension?
hint of poor nutrition and warning sign for Addison's disease
166
What is acute hypotension?
important sign of circulatory shock and is a threat to patients undergoing surgery and those in ICU
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What are the two types of hypertension?
Transient and persistent
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What are the risk factors for Primary or Essential hypertension?
Diet, obesity, age, race, heredity, stress and smoking
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What causes hypertension?
Identifiable disorders including excessive renin secretion, arteriosclerosis, and endocrine disorders
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What are the three types of Circulatory shock?
Hypovolemic shock, vascular shock, cardiogenic shock
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What causes hypovelemic shock?
Large scale blood loss
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What is vascular shock?
Poor circulation resulting from extreme vasodilation
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What is cardiogenic shock?
the heart cannot sustain adequate circulation
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Where does the endothelial lining of blood vessels come from
Mesodermal cells which collect in blood islands
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What are blood islands?
they form rudimentary vascular tubes through which the heart pumps blood by the fourth week of development
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What are fetal shunts?
foramen ovale and ductus arteriosus
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How does the placenta get blood?
the umbilical vein and arteries
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how does vessel formation occur?
As needed to support body growth; for wound healing; or to rebuild vessels lost during menstrual cycles
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With again what do vessels turn into?
Varicose veins, atherosclerosis, and increased blood pressure may come
