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