Chapter #21: Blood Vessels & Circulation Flashcards
The largest blood vessels attached to the heart
-Pulmonary trunk
-Aorta
Types of Blood Vessels
-Arteries
-Arterioles
-Capillaries
-Venules
-Veins
Arteries
carry blood away from (comes out of left ventricle)
Arterioles
smallest branches of arteries that lead to capillary beds
Capillaries
-Smallest blood vessels with thin walls
-Location of exchange between blood and interstitial fluid
Venules
smallest branches of veins that collect blood from capillaries
Veins
return blood to heart
How many layers do blood vessel walls have?
three layers
What are the three layers of vessel walls?
- Tunica intima (inner layer)
- Tunica media (middle layer)
- Tunica externa (outer layer)
** know diagram on slide 9
Tunica Intima
-inner layer
-includes: the endothelial lining and internal elastic membrane (in arteries which contain elastic fibers)
-usually rippled due to muscle constriction (in arteries)
-usually rippled due to vessel constriction (in veins)
Order of blood exchange
arteries –> arterioles –> capillaries –> venules –> veins
Why are elastic fibers important in the internal elastic membrane in your arteries?
-stretch and return back to normal size
-expansion/contraction of the vessel to absorb shock and keep capillaries from bursting
-closer the vessels are to the heart, the more elastic fibers they’ll have due to the absorbance of shock
Tunica Media
-middle layer
-contains smooth muscle
-external elastic membrane (in arteries)
Tunica Externa
-outer layer
-Anchors vessel to adjacent tissues
-Contains: collagen fibers, elastic fibers, smooth muscle cells (in veins)
Differences between arteries and veins
-Arteries have thicker walls and higher blood pressure than veins
-A constricted artery has a small, round lumen
-A vein has a large, irregular lumen
-The endothelium of a constricted artery is folded
-Arteries are more elastic than veins
-Veins have valves
Structure and function of arteries
-Elasticity allows arteries to absorb pressure waves that come with each heartbeat
-Contractility
-Vasoconstriction
-Vasodilation
Contractility in arteries
-Arteries change diameter
-Controlled by sympathetic division of ANS
Vasoconstriction in arteries
Contraction of arterial smooth muscle
Vasodilation in arteries
-Relaxation of arterial smooth muscle
-Enlarges the lumen
Effects of Vasoconstriction and vasodilation
-Afterload on heart
-Peripheral blood pressure
-Capillary blood flow
Afterload on heart
-if vessels are constricted, the afterload will be greater
-the force against which the left ventricle has to push into the arteries
Peripheral blood pressure
everything from the heart past your aorta
from arteries to capillaries, arteries change:
-from elastic arteries
-to muscular arteries
-to arterioles
Elastic Arteries
-conducting arteries
-Large vessels (e.g., pulmonary trunk and aorta)
-Tunica media has predominantly elastic fibers
-Elasticity evens out pulse force
Muscular arteries
-distribution arteries
-Most arteries are medium-sized muscular arteries
-Tunica media has predominantly muscle cells
Arterioles
-resistance vessels
-Small vessels (smallest of the arterial system)
-Have no tunica externa
-Have thin or incomplete tunica media
Aneurysm
-A bulge in an arterial wall
-Caused by weak spot in elastic fibers
-Pressure may rupture vessel
Capillaries
-Smallest vessels with thin walls
-Microscopic capillary networks permeate all active tissues
Capillary function
-Location of all exchange functions of cardiovascular system
-Materials diffuse between blood and interstitial fluid
Capillary structure
-Endothelial tube, inside thin basement membrane
-No tunica media
-No tunica externa
-Diameter is similar to that of a red blood cell
Capillary beds
-capillary plexus
-Connect one arteriole and one venule
-Precapillary sphincter
-ex) when you’re running, the capillary bed will open at your quads and close at your liver
**know diagrams on slides 22 & 23
Precapillary Sphincter
-part of capillary beds
-Guards entrance to each capillary
-Opens and closes, causing capillary blood to flow in pulses
-allows things in or out; contains smooth muscle tissue
Collaterals
-Multiple arteries that contribute to one capillary bed
-Allow circulation if one artery is blocked
Arterial anastomosis
Fusion of two collateral arteries
Arteriovenous anastomoses
-Direct connections between arterioles and venules
-Bypass the capillary bed
Veins
Collect blood from capillaries and return it to heart
Compared to arteries, veins have
-Larger diameters
-Thinner walls
-Lower blood pressure
Venules
-Very small veins
-Collect blood from capillaries
Medium-sized veins
-Very few smooth muscle cells
-longitudinal bundles of elastic fibers
Large veins
-Have all three tunica layers
-Thick tunica externa
-Thin tunica media
Venous valves
-Folds of tunica intima
-Prevent blood from flowing backward
-Compression of veins pushes blood toward heart (how blood returns back to the heart)
-When walls of veins near the valves weaken, varicose veins or hemorrhoids may result
when you contract your muscles to walk, which valves open and close?
-valve opens superior to contracting muscle
-valve closes inferior to contracting muscle
Capacitance of a blood vessel
-The ability to stretch
-Veins (capacitance vessels) stretch more than arteries
–Act as blood reservoirs (veins act as a blood bank)
venoconstriction
-Systemic veins constrict in response to blood loss
–Increasing amount of blood in arterial system and capillaries
3 ways to measure pressure
- Blood Pressure (BP)
- Capillary Hydrostatic Pressure (CHP)
- Venous Pressure
Blood Pressure (BP)
arterial pressure (mm Hg)
Capillary Hydrostatic Pressure (CHP)
pressure within the capillary beds
Venous pressure
pressure in the venous system
Circulatory pressure
-Must overcome total peripheral resistance
–Resistance of entire cardiovascular system
Total peripheral resistance (TPR) is affected by
-Vascular resistance
-Blood viscosity
-Turbulence
**know diagrams 35-38
Vascular resistance
-Increases total peripheral resistance (TPR)
-Due to friction between blood and vessel walls
-Depends on vessel diameter
–Vessel diameter varies by vasodilation and vasoconstriction
—R (resistance) increases as vessel diameter decreases
Blood viscosity
-R (resistance) caused by thickness of the liquid
-Whole blood viscosity is about four times that of water
Turbulence
-Swirling action that disturbs smooth flow of liquid
-Occurs in heart chambers and great vessels
-Atherosclerotic plaques cause abnormal turbulence
Factors that cause vasoconstriction
- Dehydration
- Cold temperatures
Types of Arterial blood pressure
- Systolic Pressure
- Diastolic Pressure
- Pulse Pressure
- Mean Arterial Pressure (MAP)
Systolic Pressure
-Peak arterial pressure during ventricular systole (left ventricle)
-90% of the time, this is the pressure you’re looking at
Diastolic Pressure
-Minimum arterial pressure at end of ventricular diastole
-diastole = relaxation
Pulse Pressure
Difference between systolic and diastolic pressure
Mean arterial pressure (MAP)
Diastolic pressure + one-third pulse pressure
Hypertension
-Abnormally high blood pressure
-Greater than 140/90
Hypotension
-Abnormally low blood pressure
-not getting enough circulation to the body & brain
2 types of strokes
- Ischemic stroke: no blood gets to tissue
- Hemorrhagic stroke: blood vessel ruptures
Elastic rebound
-arterial walls
–stretch during systole
–rebound (recoil to original shape) during diastole
–keep blood moving during diastole
Return of blood to the heart is assisted by
-Skeletal muscular compression of veins
–When leg muscles are immobilized, blood supply to the brain is reduced, and fainting may result
-The respiratory pump
–Thoracic cavity expands during inhalation, decreasing venous pressure in the chest
Capillary exchange
-Vital to homeostasis
-Materials move across capillary walls by:
1. Diffusion
2. Filtration
3. Reabsorption
-Capillaries filter more than they reabsorb
–Excess fluid enters lymphatic vessels
Interplay between filtration and reabsorption
1.Ensures that plasma and interstitial fluid are in constant communication and mutual exchange
2. Accelerates distribution of nutrients, hormones, and dissolved gases throughout tissues
3. Assists in the transport of insoluble lipids and tissue proteins that cannot cross capillary walls
4. Carries bacterial toxins and other chemical stimuli to lymphatic tissues and organs
CHP
Capillary Hydrostatic Pressure
BCOP
Blood colloid osmotic pressure
NFP
Net filtration pressure
What does it mean if CHP>BCOP
-fluid is forced out of the capillary
-filtration into tissue cells
-flows into lymphatic vessels
-return to circulation
What does it mean if CHP = BCOP?
-no net movement of fluid
What does it mean if BCOP > CHP?
-fluid moves into capillary
-reabsorption
Tissue perfusion
-Blood flow through the tissues
-Carries O2 and nutrients to tissues and organs
-Carries CO2 and wastes away
Vasomotion/autoregulation
-Contraction and relaxation cycle of precapillary sphincters
-Causes blood flow in capillary beds to constantly change routes
Ways to control cardiac output and blood pressure
- Autoregulation
- Neural mechanisms
- Endocrine mechanisms
Autoregulation
-Causes immediate, localized homeostatic adjustments
-more based on chemicals around capillaries
Neural mechanisms
-Respond quickly to changes at specific sites
-nerves going to blood vessels
-Cardiovascular (CV) center of the medulla oblongata: Increases or decreases cardiac output
–cardiovascular center is more dependent on CO2 levels instead of O2
Endocrine mechanisms
-Direct long-term changes
-regular output of epinephrine, norepinephrine, cortisols, etc.
-E and NE from adrenal medullae stimulate cardiac output and peripheral vasoconstriction
Autoregulation of blood flow within tissues
-Vasodilators are factors that promote dilation of precapillary sphincters, increasing blood flow
-Local vasodilators include
–Low O2 or high CO2 levels
–Nitric oxide (NO)
Vasomotor center
-control of vasoconstriction
-control of vasodilation
Control of vasoconstriction
-Controlled by adrenergic nerves (NE)
-Stimulate contraction in arteriole walls
Control of vasodilation
-Controlled by cholinergic nerves (NO)
-Relax smooth muscle
Vasomotor tone
Produced by constant action of sympathetic vasoconstrictor nerves
Reflex control of cardiovascular function
-Cardiovascular centers monitor arterial blood
–Baroreceptor reflexes
–Chemoreceptor reflexes
Baroreceptor reflexes
Respond to changes in blood pressure
Chemoreceptor reflexes
-Respond to changes in chemical composition, particularly pH and dissolved gases
-Peripheral chemoreceptors in carotid bodies and aortic bodies monitor blood
-Respond to changes in pH, O2, and CO2
-Coordinate cardiovascular and respiratory activities
Stroke volume
amount of blood being pumped from left ventricle
When blood pressure rises, CV centers
-Decrease cardiac output (stroke volume)
-Cause peripheral vasodilation
When blood pressure falls, CV centers
-Increase cardiac output (stroke volume)
-Cause peripheral vasoconstriction
Atrial baroreceptors (cardiovascular regulation)
monitor blood pressure at the end of the systemic circuit
** Know diagram on slide 55 & 56
Antidiuretic hormone (ADH)
-posterior lobe of pituitary
-Elevates blood pressure
-Reduces water loss at kidneys
What happens to your heart rate if oxygen is too low?
heart rate will increase
what happens to your heart rate is CO2 is too high?
heart rate will increase to get rid of it
What happens to your heart rate if pH is too high?
heart rate will increase
How do ADHs (antidiuretic hormones) increase blood pressure?
tell your kidneys to stop peeing and keep water in the body
Angiotensin II
Released in response to a decrease in renal blood pressure
The cardiovascular response to heavy exercise
-Activates sympathetic nervous system
-Cardiac output increases to maximum
–About four times resting level
-Restricts blood flow to “nonessential” organs (e.g., digestive system)
-Redirects blood flow to skeletal muscles, lungs, and heart
-Blood supply to brain is unaffected
The cardiovascular response to hemorrhaging
-Entire cardiovascular system adjusts to
–Maintain blood pressure
–Restore blood volume
Short-term elevation of blood pressure
- Carotid and aortic reflexes
- Sympathetic nervous system
- Hormonal effects
Carotid and aortic reflexes
-Increase cardiac output (increasing heart rate)
-Cause peripheral vasoconstriction
Sympathetic nervous system
-Further constricts arterioles
-Venoconstriction improves venous return
Hormonal effects
-Increase cardiac output
-Increase peripheral vasoconstriction
