Bio 209 Ch 21
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What is a Lumen?
An interior opening which blood flows through
What are the three layers of the blood vessels?
Tunica Interna (internal)
Tunica Media (middle)
Tunica Externa (external)
What is Vasoconstriction?
Contraction of the BV, causing a decrease in BV diameter
What is Vasodilation?
Widening of BV, causing increase of BV diameter
What is the function of Elastic Arteries?
Conduct blood from heart to muscle arteries
Allows stretching and recoiling during during ventricular systole and ventricular diastole
What is the function of Muscular Arteries?
Distribute blood throughout the body
Controls flow of blood by vasoconstriction and vasodilation
What is the function of Arterioles?
Deliver blood to capillaries
Regulate blood flow by changing resistance and controlling amount of blood entering capillaries
Regulate BP by vasoconstriction and vasodilation
What are some examples of Elastic Arteries?
What are some examples of Muscular Arteries?
Union of arterial branches that supply the same body region
Opposition of blood flow due to friction between blood and BV wall
In what way does vasoconstriction affect resistance and blood flow to the capillaries?
Resistance increases & Blood flow decreases to capillaries
In what way does vasodilation affect resistance and blood flow to the capillaries?
Resistance decreases and Blood flow increases to the capillaries
What is metarteriole?
Precapillary sphincters into capillaries
What is a Precapillary Spincter?
Smooth muscle cell at the junction of a metarteriole and capillary
How do Precapillary Spincters control blood flow to capillary?
Contraction and relaxation of the smooth muscles either decreases blood flow or increases blood flow
Describe the structure of capillaries
Smallest blood vessels consisting of tunica interna with endothelial cells supported by a basement membrane
What are the functions of a capillary?
Exchange substances between blood and interstitial fluid
Body tissues that have higher metabolic rate (brain & kidneys) have more capillary networks
Flow of blood from a metarteriole through capillaries to postcapillary venules
Alternation contraction and relaxation of smooth muscles in metarterioles and precapillary spincters
What are Continuous Capillaries?
Capillaries usually found in brain, muscles, connective tissues and lungs that diffuse substances through intracellular clefts
What are Fenestrated Capillaries?
Capillaries usually found in kidneys, small intestines, choroid plexus of the brain and endocrine glands in which substances diffuse through intracellular clefts and fenestrations (small pores in capillaries)
What are Sinusoidal Capillaries?
Capillaries usually found in spleen, liver and pituitary that have large fenestration and intracellular clefts that allow proteins and sometimes blood cells to pass through
Define Portal System
Pathway of blood is usually Hearth, Arteries, Arterioles, Metarteriole, Capillaries, Venules, Veins, Heart (HAAMCVVH)
Blood passes from one capillary bed to another by a portal vein
How does the pumping action of the heart aid venous return of blood towards the heart?
Because when atria relaxes, the pressure decrease causing blood to move from an area of higher concentration to lower concentration
How does contraction of skeletal muscle aid venous return towards the heart?
Muscles help blood move through veins and venous valves prevent backflow of blood
What is a Blood Reservoir?
Veins and Venules are examples of Blood Reservoirs
Where would blood mostly be found?
60% of blood (at rest) is found in Systemic Veins and Venules
How do substances enter and leave the capillaries?
- Diffusion: movement of substances from an area of high concentration to low concentration
- Transcytosis: movement of larger substances by endocytosis and exocytosis
- Bulk Flow: movement of large amounts of ions, molecules or particles in a fluid move together in the same direction from an area of high pressure to low pressure
Describe the pressure that promotes Filtration
- Blood Hydrostatic Pressure (BHP): pressure that blood exerts against the capillary walls
- Interstitial Fluid Osmotic Pressure (IFOP): force caused by proteins in interstitial fluid that are too large to pass through intracellular clefts or fenestrations (pulls fluids out of capillaries)
Describe the pressure that promotes Absorption
- Blood Colloid Osmotic Pressure (BCOP): force caused by proteins in plasma that are too large to pass through intercellular clefts or fenestrations (causes fluid to move into capillaries from tissues)
- Interstitial Fluid Hydrostatic Pressure (IFHP): pressure of water in interstitial fluid
How much fluid that leaves the capillaries reabsorbed at the venous end?
- 85% is reabsorbed
- Remaining fluid enters lymph
What is the cause of edema?
- Excess filtration (due to high BP or increased permeability of capillaries)
- Inadequate reabsorption (due to decreased concentration of plasma proteins related to liver disease, malnutrition, burns, kidney disease)
What is Blood Flow?
Volume of blood that flows through any tissue per minute
Blood Pressure is the hydrostatic pressure of blood exerted on blood vessel walls
What causes BP?
Contraction of ventricles
Define Systolic Pressure
Highest BP in the arteries attained during ventricle systole
Define Diastolic Pressure
Lowest BP attained during ventricular diastole
Define Mean Arterial Pressure (MAP)
Average BP in the arteries
How does blood volume affect blood pressure?
- BP depends on the total volume of blood volume of the body
- - Decreasing BV causes a decrease in BP
Define Systemic Vascular Resistance (SVR)
Refers to all the vascular resistance of systemic BV
What are the sources of SVR?
- - Diameter of BV
- - Blood viscosity
- - Total BV length
What is Venous Return?
Volume of blood flowing from systemic venous vessels to heart
What are some mechanisms that aid venous return?
- - Veins have low resistance
- - Skeletal muscle pumps contract and move blood in veins toward heart (milking)
- - Respiratory pump contracts diaphragm
Why is blood velocity slowest in capillaries?
Blood flow is slowest where cross-sectional area is greatest - slowest in capillaries and gives time for substances to diffuse across capillaries
Define Circulation Time
The time required for a drop of blood to flow through the pulmonary and systemic circulations
What role does the cardiovascular play in controlling BP?
- - Receives input from higher brain and receptors
- - Integrates input and initiates output to effectors (heart & BV)
How does Baroreceptor Reflexes control BP?
- In the case of High BP:
- - Frequency of impulses increases and sent to Medulla
- - Decreases HR and force of contraction, causing vasodilation
- - Decreased CO & SVR causes BP to decrease and returns to normal
- In the case of Low BP:
- - Frequency of impulses decreases and sent to Medulla
- - Increased HR and force of contraction, causing vasoconstriction
- - Increased CO & SVR causes BP to increase and returns to normal
What is Orthostatic Hypotension?
A decrease in BP and blood flow to head caused by going from a prone to erect position
What effect does Renin-Angiotensin-Aldosterone have on BP?
Renin produces Angiotensin II
Angiotensin II increases BP by vasoconstriction (increased SVR) and increases secretion of Aldosterone (increases BV by reabsorption of water and Na)
What effect does Epinephrine & Norepinephrine have on BP?
Increases HR and force of contractgion (increases CO) and causes vasoconstricion and vasodilation of arterioles of skin/abdominal organs and arterioles in skeletal muscles/heart
What effect does ADH have on BP?
Increases BP by reduction of urine and causing vasoconstriction (increased SVR)
What effect does ANP have on BP?
Reduces blood pressure by causing vasodilation (decreased SVR) and increases loss of water and salt in uring
What is Autoregulation?
Regulation of vasomotion to meet the metabolic demands of tissues
How does Autoregulation control blood flow?
- Physical Changes:
- - Warming causes vasodilation
- - Cooling causes vasoconstriction
- - Myogenic response: stretching of BV walls causing forceful contractions
Vasodilating & Vasoconstricting chemicals released by tissue cells
What is Shock?
State in which tissues don't receive enough O and nutrients to meet metabolic needs, caused by inadequate blood flow to tissues
What is the difference between Hypovolemic & Cardiogenic Shock?
Hypovolemic: caused by low BV (hemorrhage, diarrhea, vomitting)
Cardiogenic: caused by poor heart function (insufficient blood flow to tissues)
What is the difference between Vascular & Obstructive Shock?
Vascular: caused by massive vasodilation
Obstructive: caused by obstruction of blood flow (blood clot)
What is a Pulse?
Traveling pressure wave caused by the expansion and recoil of elastic arteries after ventricular systole
What is a Sphygmomanometer?
Device used to measure BP
What are Korotkoff Sounds?
Sounds heard when measuring BP with sphygmomanometer
What is Pulse Pressure?
Difference between systolic and diastolic pressure
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