The Cardiovascular System Flashcards
Three major types of vessels are?
Arteries, capillaries, and veins
Arteries?
Carry blood away from the heart
Veins?
They carry blood toward the heart
Capillaries?
They contact tissue cells and directly serve cellular needs
Arteries and veins are composed of what three tunics?
Tunica interna, tunica media, tunica externa
Elastic (conducting) arteries
Thick-walled arteries near the heart; the aorta and its major branches
- Large lumen allow low-resistance conduction of blood - contain elastin in all 3 tunics - Withstand and smooth out large blood pressure fluctuation - Serve as pressure reservoirs
Pressure is what at the vena cava?
0 mm Hg
Muscular arteries
Distal to elastic arteries; deliver blood to body organs
Have thick tunica media with more smooth muscle
Active in vasoconstriction
Arterioles
Smallest arteries; lead to capillary beds
Control flow into capillary beds via vasodilation and constriction
Capillaries structure
Are the smallest blood vessels
Walls consisting of a thin tunica interna one cell thick
Allow only one single RBC to pass at a time
Pericytes on the outer surface stabilize their walls
Continuous capillaries
- Abundant in the skin and muscles
- endothelial cells provide an uninterrupted lining
- adjacent cells are connected with tight junctions
- intercellular clefts allow the passage of fluids
Continuous capillaries of the brain
Have tight junctions completely around the endothelium constitutes the blood-brain barrier
Fenestrated(pores) capillaries
Are found wherever active capillary absorption or filtration formation occurs (example small intestines, endocrine glands and kidneys)
characterized by an endothelium riddled with pores
greater permeability and than continuous capillaries
Sinusoid or sinusoidal capillaries
Are highly modified, leaky, fenestrated capillaries with large lumens
found in the liver, bone marrow, lymphoid tissue, and spleen allow large molecules (proteins and white blood cells) to pass between the blood and surrounding tissue
blood flows sluggishly allowing for modification in various ways
Capillary beds
A microcirculation of interwoven networks of capillaries consisting of: vascular shunts-metarteriole & true capillaries
Vascular shunts- metarteriole
Thoroughfare channel connecting an arteriole directly with a post capillary venule
True capillaries
10 to 100 per capillary bed, capillaries branch off the metarteriole and return at the distal end of the bed
Precapillary sphincter
“Close up”
cuff of smooth muscle that surrounds each true capillary
regulates blood flow into the capillary
blood flow is regulated by vasomotor nerves and Local chemical conditions
Venules
Are formed when capillary beds unite
allow fluid and WBCs to pass from the bloodstream to tissues
Postcapillary venules
Smallest venules, composed of endothelium and a few pericytes
Large venules have one or two layers of smooth muscle (tunica media)
Capacitance vessels
(Blood Reservoirs) that contain 65% of the blood supply
Venous sinuses
Specialized, flattened veins with extremely thin walls (example coronary sinus of the heart and dural sinuses of the brain)
Arterial anastomoses
Provide alternate pathways (collateral channels) for blood to reach a given body region
Varicose veins
Veins with incompetent (leaky) valves
Straining causes?
Hemorrhoids- varicose veins of the anus
Blood flow
It’s the actual volume of blood flowing through a vessel, an organ or the entire circulation.
- Measured in ml per min
- Is equivalent to cardiac output (CO), considering the entire vascular system
- is relatively constant when at rest.
- Varies widely through individual organs
Blood pressure
Is force per unit area exerted on the wall of the blood vessel by its contained blood
- expressed in millimeters of mercury (mm Hg)
- measured in reference to systemic arterial BP in large arteries near the heart
Resistance factors that remain relatively constant are?
Blood viscosity and blood vessel length
Blood viscosity
“Stickiness” of the blood; the stickier the blood, the greater the resistance encountered
Blood vessel length
The longer the vessel, the greater the resistance encountered
Resistance
Opposition to flow
-Measure of the amount of friction blood encounters
Three important sources of resistance are?
Blood viscosity, total blood vessel length, &
blood vessel diameter (the only one that fluctuates)
This steepest change in blood-pressure occurs in
The arterioles
Systemic pressure is highest in the
Aorta
The pumping action of the heart generates blood flow through the vessels along a ____ _____ always moving from ____ to ____ pressure areas
Pressure gradient; higher to lower
Systolic pressure
Pressure exerted on arterial walls during ventricular contraction
Diastolic pressure
Lowest level of arterial pressure during a ventricular cycle
Pulse pressure
The difference between systolic and diastolic pressure
Mean arterial pressure (MAP)
Pressure that propels the blood to the tissues
(constant)
different in each part of the body
MAP =
Diastolic pressure + 1/3 pulse pressure
Venous blood pressure alone is too low to promote adequate blood return and is aided by
Respiratory pump
muscular pump
Respiratory “pump”
Pressure changes created during breathing suck blood for the heart by squeezing local veins
Muscular “pump”
Contraction of skeletal muscles “milk” blood toward the heart
Valves prevent ____ during venous return
Back flow
Maintaining blood pressure requires?
Cooperation of the heart, blood vessels and kidneys
supervision of the brain (SNS & PNS)
The main factors influencing blood-pressure are?
Cardiac output (CO) Peripheral resistance (PR) Blood volume
Short term controls of blood pressure
Are mediated by the nervous system and blood-borne chemicals
Counteract moment to moment fluctuations and blood pressure by altering peripheral resistance
Long-term controls regulate?
Blood volume
Neural controls of peripheral resistance do what?
Alter blood distribution in response to demands
Maintain MAP by altering blood vessel diameter
Neural controls
Vasomotor center
Baroreceptor-initiated reflexes
Vasomotor center
A cluster of sympathetic neurons in the medulla that oversees changes in blood vessel diameter
Maintains blood vessel tone by innervating smooth muscles of blood vessels especially arterioles
Cardiovascular center
Vasomotor center plus the cardiac centers that integrate blood pressure control by altering cardiac output and blood vessel diameter
Short term mechanisms
Sympathetic activity causes
Vasoconstriction and a rise in BP if increased
BP to decline to basal levels if decreased
Baroreceptor-initiated reflexes
Increased blood pressure stimulates the cardioinhibitory center to
Increase vessel diameter (vasodilation)
Decrease heart rate, cardiac output, peripheral resistance and blood pressure
Chemoreceptors
Regulates BP reflexes sensitive to oxygen and carbon dioxide
Catecholamines
Aka adrenal medulla hormones
Epinephrine and norepinephrine increase BP
Antidiurectic hormone
Causes intense vasoconstriction in cases of extremely low BP
Angiotensin II
Kidney release of renin generates angiotensin II, which causes vasoconstriction
Endothelium-derived factors
Endothelin and prostaglandin-derived growth factor (PDGF) are both vasoconstrictors
Atrial Natriuretic peptide (ANP)
Causes blood volume and pressure to decline
Nitric oxide (NO)
Is a brief but potent vasodilator
Inflammatory chemicals
Histamine, prostacyclin and kinins are potent vasodilators
Alcohol
Causes BP to drop by inhibiting ADH
Long-term controls of blood pressure
Increase BP stimulate the kidney to eliminate water thus reducing BP
Decrease BP stimulates the kidneys to release blood volume and BP
Baroreceptors Adapt to chronic higher or low BP therefore they are ineffective against?
Hypertension
Direct renal mechanism
Alters blood volume
Blood volume or BP increases -> urine output decreases
Indirect renal mechanism
Involves renin angiotensin mechanism
Vital signs
Pulse and blood pressure, along with respiratory rate and body temperature
Radial pulse
Routinely used; is taking on the radial artery at the wrist
Ausculatory method
Measure the systemic arterial blood pressure indirectly
Blood pressure cuff does this
Sphygmomanometer
Blood-pressure cuff
When measuring blood pressure the first sound heard is recorded as
Systolic pressure
When measuring blood pressure and sound disappears it is recorded as
Diastolic pressure
Blood-pressure sounds are called?
Korotkoff sounds
Orthostatic hypotension
Temporary low BP and dizziness when suddenly rising from a sitting or reclining position
Hypotension
Low BP in which systolic pressure is below 100 mm Hg
Chronic hypotension
Hint of poor nutrition and warning signs for Addison’s disease
Acute hypotension
Important sign of circulatory shock
Threat to patients undergoing surgery and those in intensive care units
Secondary hypertension
Due to identifiable disorders, including excessive renin secretion, arteriosclerosis and endocrine disorders (Cushing’s disease)
10% of cases
Primary hypertension
No underlining cause, the risk factors include diet, obesity, age, race, heredity, stress and smoking
90% of cases
At the arterial end of a bed
Hydrostatic forces dominate (fluids flow out)
Circulatory shock
Any condition in which blood vessels are Inadequately filled and blood cannot circulate normally
Results in inadequate blood flow to meet tissue needs
Hypovolemic shock
Low blood volume: results from large-scale blood loss
Vascular shock
Normal blood volume but circulation is poor: due to extreme vasodilation
Anaphylactic shock and septic shock
Anaphylactic shock
Vascular shock
Body wide vasodilation triggered by massive histamine release
Septic shock
Vascular shock
Body wide vasodilation caused by bacterial toxins
Cardiogenic shock
Pump failure: the heart cannot sustain adequate circulation
Blood flow through the heart
Small vessels coronary circulation is influenced by aortic pressure, pumping of the ventricles
Under resting conditions blood flow through the heart may be controlled by myogenic mechanisms
Bloodflow or tissue perfusion is involved in
Delivery of oxygen and nutrients to and removal of waste from tissue cells
Gas exchange in the lungs
Absorption of nutrients from the digestive tract
Urine formation by the kidney
Blood velocity
Change as it travels through the systemic circulation
Is oppositely proportional to the cross-sectional area
For example: If it is Small it flows faster
if it is large it flows slower
Why is capillary flow slow?
Allows adequate time for exchange between blood and tissue
Autoregulation
Automatic adjustment of blood flow to each tissue in proportion to its requirements at any given point in time
Angiogenesis
The number of blood vessels in a region that will increase
Metabolic controls
Declining tissue nutrients and oxygen levels are stimuli for autoregulation
Hemoglobin delivers nitric oxide as well as oxygen to tissues
Nitric oxide induces thousand vasodilation of the capillaries to help get oxygen to tissue cells
Other autoregulatory substances include: potassium, hydrogen ions, adenosine, lactic acid, histamines, kinins, prostaglandin
Myogenic controls
Smooth muscle
Inadequate blood perfusion or excessively high arterial pressure
Are autoregulatory
Provoke myogenic responses stimulation of vascular smooth muscle
Long-term autoregulation
Is evoked when short-term autoregulation cannot meet tissue nutrient requirements
May evolve over weeks or months to enrich local blood flow
Angiogenesis
Blood flow: skeletal muscles
Resting muscle blood flow is regulated by myogenic and general neural mechanisms in response to oxygen and carbon dioxide levels
When muscles become active hyperemia is directly proportional to greater metabolic activity of the muscle
Arterioles in muscle have cholinergic, and alpha and beta andrenergic receptors
Blood flow: skeletal muscle regulation
During exercise sympathetic nervous system increases activity
Norepinephrine causes vasoconstriction of blood vessels and digested viscera and skin
Intrinsic metabolic control cause vasodilation and skeletal muscle to occur
Low levels of epinephrine bind to beta receptors
Cholinergic receptors are occupied
Blood flow: brain
Blood flow to the brain is constant and neurons are intolerant of ischemia
Metabolic controls- brain tissue is extremely sensitive to decline pH and increased carbon dioxide causes marked vasodilation
Myogenic controls protect the brain from damaging changes in blood pressure
MAP below 60mm Hg can cause
Syncope
MAP above 160 can result in
Cerebral edema
Blood flow through the skin
Supplies nutrients to cells in response to oxygen need
Help maintain body temp
Provide a blood reservoir
Blood flow to venous plexuses below the skin surface
Varies from 50 ml/min to 2500 ml/min Depending on body temp
Is controlled by SNS reflexes initiated by temperature receptors and the CNS
Bloodflow or tissue perfusion is involved in
Delivery of oxygen and nutrients to and removal of waste from tissue cells
Gas exchange in the lungs
Absorption of nutrients from the digestive tract
Urine formation by the kidney
Why is capillary flow slow?
Allows adequate time for exchange between blood and tissue
Vascular muscle responds directly to
Increased vascular pressure with increased tone which causes vasoconstriction
Reduce stretch with vasodilation which promotes increased blood flow to the tissue
Long-term autoregulation
Is evoked when short-term autoregulation cannot meet tissue nutrient requirements
May evolve over weeks or months to enrich local blood flow
Angiogenesis
Blood flow: skeletal muscles
Resting muscle blood flow is regulated by myogenic and general neural mechanisms in response to oxygen and carbon dioxide levels
When muscles become active hyperemia is directly proportional to greater metabolic activity of the muscle
Arterioles in muscle have cholinergic, and alpha and beta andrenergic receptors
Blood flow: skeletal muscle regulation
During exercise sympathetic nervous system increases activity
Norepinephrine causes vasoconstriction of blood vessels and digested viscera and skin
Intrinsic metabolic control cause vasodilation and skeletal muscle to occur
Low levels of epinephrine bind to beta receptors
Cholinergic receptors are occupied
Blood flow: brain
Blood flow to the brain is constant and neurons are intolerant of ischemia
Metabolic controls- brain tissue is extremely sensitive to decline pH and increased carbon dioxide causes marked vasodilation
Myogenic controls protect the brain from damaging changes in blood pressure
MAP below 60mm Hg can cause
Syncope
MAP above 160 can result in
Cerebral edema
Blood flow through the skin
Supplies nutrients to cells in response to oxygen need
Help maintain body temp
Provide a blood reservoir
Blood flow to venous plexuses below the skin surface
Varies from 50 ml/min to 2500 ml/min Depending on body temp
Is controlled by SNS reflexes initiated by temperature receptors and the CNS
Bloodflow or tissue perfusion is involved in
Delivery of oxygen and nutrients to and removal of waste from tissue cells
Gas exchange in the lungs
Absorption of nutrients from the digestive tract
Urine formation by the kidney
What precisely is the right Amount to provide proper tissue function
Blood flow- no more, no less
Blood velocity
Change as it travels through the systemic circulation
Is oppositely proportional to the cross-sectional area
For example: If it is Small it flows faster
if it is large it flows slower
Why is capillary flow slow?
Allows adequate time for exchange between blood and tissue
Autoregulation
Automatic adjustment of blood flow to each tissue in proportion to its requirements at any given point in time
____ remains constant, while ____ regulate the amount of blood delivered to various areas according to need
MAP ; local demands
Tunica interna
Endothelial layer that line the lumen of all vessels
Tunica media
Controls vasoconstriction/ vasodilation of vessels
Tunica externa
Protects and reinforces vessels
Vaso vasorum a network of tiny blood vessels
