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Ch 20 Cardiovascular System-Blood Vessels-Posner class-BSC2086

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Blood is carried   in a closed system of vessels that begins and ends at the heart  
The three major types of vessels are   arteries, capillaries, and veins Arteries carry blood  
veins carry blood   toward the heart  
Capillaries contact   tissue cells  
Capillaries directly serve   cellular needs  
The three tunics that arteries and veins are composed of   tunica interna (intima), tunica media, and tunica externa  
central blood-containing space surrounded by tunics   Lumen  
the tunica intima   reduces friction between the blood and the  
the tunica media   controls vasoconstriction and vasodilation  
the tunica externa ________, _______ & ______the blood vessel to surrounding structures   protects, reinforces and anchors  
Elastic or conducting arteries contain what? & what does this allow?   large amounts of elastin, which allows these vessels to withstand and smooth out the pressure fluctuation due to the pumping action of the heart.  
Muscular or distributing arteries deliver blood to   specific body organs  
What type of arteries have the most tunica media of all the vessels?   Muscular or distributing arteries.  
These vessels are active in vasoconstriction   Muscular or distributing arteries  
Arterioles   the smallest arteries  
Arterioles regulate blood flow into capillary beds   vasoconstriction or vasodilation.  
Capillaries   the smallest blood vessels  
Capillaries allow for exchange of substances between   the blood and interstitial fluid  
There are three structural types of capillaries   continuous, fenestrated, and sinusoids  
Continuous capillaries   allow passage of fluids and small solutes  
Most common type of capillaries   Continuous capilaries  
Fenestrated capillaries   are more permeable to fluid and solutes than continuous capillaries  
Fenestrated capillaries are found   wherever active capillary absorption or filtrate formation occurs (e.g., small intestines, endocrine glands, and kidneys)  
Sinusoidal capillaries are   leaky capillaries with large lumens;  
Sinusoidal capillaries allow   large molecules (proteins and blood cells) to pass between the blood and surrounding tissues  
Where are Sinusoidal capillaries found?   in the liver, bone marrow, lymphoid tissue, and in some endocrine organs  
How does Blood flow within Sinusoidal capillaries?   sluggishly, allowing for modification in various ways  
Capillary Beds are   Microcirculatory networks  
Capillary Beds consist of   1.Vascular shunts 2.True capillaries  
True capillaries   function as the exchange vessels  
Vascular shunts   metarteriole-thoroughfare channel connecting an arteriole directly with a postcapillary venule  
precapillary sphincter   A cuff of smooth muscle that surround each capillary at the matearteriole and acts as to regulate blood flow into the capillary  
Venules and Veins are found in what system?   Venous System  
Where are Venules formed?   where capillaries converge  
Venules allow   fluid and white blood cells to move easily between the blood and tissues  
When venules converge what are formed?   Veins are formed  
Veins are formed   when venules converge  
Veins   are relatively thin walled with large lumens  
Veins contain about ____% of the blood supply   65%  
Veins have much _________blood pressure and _______walls than arteries   lower, thinner  
To return blood to the heart, veins have special adaptations What are they and describe each   1.Large-diameter lumens, which offer little resistance to flow 2.Valves (resembling semilunar heart valves), which prevent backflow of blood  
Vascular Anastomoses   Merging blood vessels, more common in veins than arteries  
Arterial anastomoses provide   alternate pathways (collateral channels) for blood to reach a given body region  
If one branch is blocked (regarding Arterial anastomoses)   the collateral channel can supply the area with adequate blood supply  
Blood Flow   Actual volume of blood flowing through a vessel, an organ, or the entire circulation in a given period:  
Blood Flow is measured in   ml per min.  
Blood Flow is relatively   constant when at rest  
Blood Pressure (BP)   Force per unit area exerted on the wall of a blood vessel by its contained blood  
Blood Pressure (BP) is Expressed in   millimeters of mercury (mm Hg)  
What is the "opposition to flow"?   Resistance  
Resistance   Measure of the friction between blood and the vessel walls  
Resistance comes from 3 sources   blood viscosity, total blood vessel length, blood vessel diameter  
If Blood Pressure increases, blood flow _________   increases  
if BP decreases   blood flow_______  
If resistance increases, blood flow¬¬¬¬¬________   decreases  
Peripheral resistance is   the most important factor influencing local blood flow  
vasoconstriction (or vasodilation) can dramatically   alter local blood flow, while the BP remains unchanged  
Systemic Blood Pressure   The pumping action of the heart generates blood flow (through the vessels along a pressure gradient, always moving from higher- to lower-pressure areas)  
Systemic Blood Pressure results when   flow is opposed by resistance  
Three things about Systemic pressure   Is highest in the aorta, Declines throughout the length of the pathway, Is 0 mm Hg in the right atrium  
Arterial BP reflects two factors of the arteries close to the heart   1.Their elasticity (compliance or distensibility) 2.The amount of blood forced into them at any given time  
Arterial Blood Pressure occurs in   elastic arteries near the heart  
Arterial BP is   pulsatile (BP rises and falls)  
systolic pressure   When the left ventricle contracts, blood is forced into the aorta producing a peak in pressure (120 mm Hg)  
Diastolic pressure   pressure that occurs when the blood can not flow back into the heart and the aorta recoils (the diameter is smaller) (70-80 mm Hg)  
Pulse pressure   the difference between systolic and diastolic pressure  
Mean arterial pressure (MAP)   pressure that propels the blood to the tissues  
Is Capillary BP low or high?   low  
Low capillary pressure is desirable because   high BP would rupture the fragile, thin-walled capillaries  
low capillary BP is sufficient to   exchange between the blood and tissues  
Venous BP   steady and changes little during the cardiac cycle  
The pressure gradient in the venous system is   only about 20 mm Hg  
A cut vein has ¬¬¬¬¬______blood flow; a lacerated artery flows   even; in spurts  
Blood pressure varies directly with changes in (2 things)   blood volume and cardiac output  
blood volume and cardiac output are determined mainly by (3 things)   venous return, neural and hormonal controls  
What two ways are Short-Term Mechanisms controlled?   Neural Controls and chemical controls  
Neural controls of peripheral resistance do two things   1. Alter blood distribution to respond to specific demands 2. Maintain MAP by altering blood vessel diameter  
The vasomotor center   a cluster of sympathetic nerons in the medulla that controls changes in the diameter of the blood vessels  
Baroreceptors   detect stretch impulses to the vasomotor center, inhibits its activity and promotes vasodilation of arterioles and veins (Baroreceptor Reflexes)  
Chemoreceptors   detect a rise in CO2 content of the blood and stimulate the cardioacceleratory and vasomotor centers increased cardiac output and vasoconstriction  
The cortex and hypothalamus modify arterial pressure?   via the medullary centers  
Blood pressure is regulated by   chemoreceptor reflexes sensitive to oxygen and carbon dioxide  
Chemoreceptors sensitive to oxygen and carbon dioxide are found in the   carotid and aortic bodies  
Reflexes that regulate blood pressure are integrated in the   medulla  
Higher brain centers (cortex and hypothalamus) can modify BP via   relays to medullary centers  
Chemicals that Increase Blood Pressure   Adrenal medulla hormones, Antidiuretic hormone (ADH), Angiotensin II, Endothelium-derived factors  
Adrenal medulla hormones   norepinephrine and epinephrine increase blood pressure  
Antidiuretic hormone (ADH)   causes intense vasoconstriction in cases of extremely low BP  
Angiotensin II   kidney release of renin generates angiotensin II, which causes intense vasoconstriction  
Endothelium-derived factors   promote vasoconstriction and are released in response to low blood flow  
Chemicals that Decrease Blood Pressure   Atrial natriuretic peptide (ANP), Nitric oxide (NO), Inflammatory chemicals, Alcohol  
Atrial natriuretic peptide (ANP)   causes blood volume and pressure to decline  
Nitric oxide (NO)   has brief but potent vasodilator effects  
Inflammatory chemicals   histamine, prostacyclin, and kinins are potent vasodilators  
Alcohol   causes BP to drop by inhibiting ADH  
2 Long-Term Mechanisms (Renal Regulation)   Direct Mechanism and Indirect renal mechanism  
Long-term mechanisms   control BP by altering blood volume  
Increased BP (Direct Mechanism)   stimulates the kidneys to eliminate water, thus reducing blood volume dec in BP  
Decreased BP (Direct Mechanism)   stimulates the kidneys to increase blood volume and BP  
Indirect renal mechanism   involves the renin-angiotensin mechanism, a dec in BP systemic vasoconstriction  
Efficiency of the circulation can be assessed by   taking pulse and blood pressure measurements  
Vital signs   pulse and blood pressure, along with respiratory rate and body temperature  
Pulse   pressure wave caused by the expansion and recoil of elastic arteries  
Where is Radial pulse taken?   on the radial artery at the wrist  
How often is radial impulse used?   routinely  
Pulse varies with (3 things)   health, body position, and activity  
Systemic arterial BP is measured by what method?   the auscultatory method  
3 steps of the auscultatory method   1.A sphygmomanometer is placed on the arm superior to the elbow, 2. Pressure is increased in the cuff until it is greater than systolic pressure in the brachial artery, 3. Pressure is released slowly and the examiner listens with a stethoscope  
Systolic pressure   The first sound heard and is recorded  
Diastolic pressure   The pressure when sound disappears is recorded  
The 2 Alterations in Blood Pressure   Hypotension and Hypertension  
Hypotension   low BP in which systolic pressure is below 100 mm Hg  
Hypertension   condition of sustained elevated arterial pressure of 140/90 or higher  
2 types of elevation in In Hypertension are   Transient elevations and Chronic (persistent) elevation  
In Hypertension, Transient elevations are   normal  
In Hypertension, Transient elevations can be caused by what 3 things   fever, physical exertion, and emotional upset  
Chronic (persistent) elevation is a major cause of (4 things)   heart failure, vascular disease, renal failure, and stroke  
3 types of Hypotension   Orthostatic, Chronic, and Acute  
Orthostatic hypotension   temporary low BP and dizziness when suddenly rising from a sitting or reclining position  
Chronic hypotension   hint of poor nutrition and warning sign for Addison’s disease  
Acute hypotension   important sign of circulatory shock  
What type of hypotension causes a threat to patients undergoing surgery and those in intensive care units?   Acute hypotension  
2 types of Hypertension   Primary (essential) and Secondary  
Hypertension may be ________ or _________   transient, persistent  
Risk factors in primary hypertension include   diet, obesity, age, race, heredity, stress, and smoking  
Secondary hypertension is due to identifiable disorders, including   excessive renin secretion, arteriosclerosis, and endocrine disorders  
Blood flow (has another name)   tissue perfusion  
Blood flow, or tissue perfusion, is involved in (4 things)   Delivery of oxygen and nutrients to, and removal of wastes from, tissue cells, Gas exchange in the lungs, Absorption of nutrients from the digestive tract, Urine formation by the kidneys  
Blood flow is precisely the right amount to provide   proper tissue function  
2 things about Blood velocity   1.Changes as it travels through the systemic circulation, 2. Is inversely proportional to the cross-sectional area  
Slow capillary flow (regarding blood velocity) allows adequate time for   exchange between blood and tissues  
Autoregulation   Local Regulation of Blood Flow  
Autoregulation   automatic adjustment of blood flow to each tissue in proportion to its needs  
Autoregulation is controlled   intrinsically by modifying the diameter of local arterioles  
Stimuli for autoregulation   declining tissue oxygen level  
2 things Hemoglobin delivers to tissues   nitric oxide (NO) and oxygen  
Nitric oxide induces vasodilation at the capillaries to help   get oxygen to tissue cells  
Myogenic control involves   the localized response of vascular smooth muscle to passive stretch.  
Inadequate blood perfusion or excessively high arterial pressure are __________ and provoke ________ _________   autoregulatory, myogenic responses  
myogenic responses   stimulation of vascular smooth muscle  
Vascular muscle responds directly to (two things)   1. Increased vascular pressure with increased tone which causes vasoconstriction 2. Reduced stretch with vasodilation which promotes increased blood flow to the tissue  
Increased vascular pressure with increased tone causes   vasoconstriction  
Reduced stretch with vasodilation promotes   increased blood flow to the tissue  
Long-Term Autoregulation is evoked (is initiated) when   short-term autoregulation cannot meet tissue nutrient requirements  
Long-Term Autoregulation May develop (time period)   over weeks or months  
Involves an increase in what 2 things?   1. the size of existing blood vessels 2.the number of vessels in a specific area  
angiogenesis   an increase in the size of existing blood vessels and an increase in the number of vessels in a specific area  
Angiogenesis takes place   As the number of vessels to a region increases, When existing vessels enlarge, When a heart vessel becomes partly occluded, Routinely in people in high altitudes, where oxygen content of the air is low  
Blood flow to skeletal muscles varies in what 2 ways?   the level of activity and fiber type  
What happens when muscles become active?   muscular autoregulation occurs almost entirely in response to decreased oxygen concentrations  
What happens during physical activity as vasodilation occurs   Muscle blood flow can increase tenfold or more  
Blood flow to the brain is tightly regulated to meet_______ requirements, as neurons are _______   neuronal; intolerant of ischemia (decreased blood flow)  
Why is Blood flow to the brain is tightly regulated   It must meet neuronal requirements  
Why must blood flow meet neuronal requirements?   because neurons are intolerant of ischemia  
Ischemia   decreased blood flow  
Metabolic controls, brain tissue is extremely sensitive to what 2 metabolic controls?   declines in pH, and increased carbon dioxide (causes marked vasodilation)  
If brain tissue has an increase in carbon dioxide, what does it cause?   causes marked vasodilation)  
3 functions of Blood flow through the skin   1. Supplies nutrients to cells in response to oxygen need, 2. Helps maintain body temperature, 3. Provides a blood reservoir  
In the skin, autoregulatory events control   oxygen and nutrient delivery to the cells  
In skin neural mechanisms control   the body temperature regulation function  
Examples of what causes temperature to rises   heat exposure, fever, vigorous exercise  
As tempuratures rises   Hypothalamic signals reduce vasomotor stimulation of the skin vessels & Heat radiates from the skin  
As temperature decreases   blood is shunted to deeper, more vital organs  
Blood flow in the pulmonary circulation is   unusual  
The pathway Blood flow in the pulmonary circulation is   short  
Arteries/arterioles are more like   veins/venules  
Why are Arteries/arterioles more like veins/venules   both are thin-walled, with large lumens  
   
The autoregulatory mechanism of blood flow to the lungs are the _________that in most tissues   opposite  
Low oxygen levels in the blood flow to lungs cause   vasoconstriction  
High oxygen levels in the blood flow to lungs promote   vasodilation  
The autoregulatory mechanism of blood flow to the lungs(vasoconstriction & vasodilation) Allows   proper oxygen loading in the lungs  
Small vessel coronary circulation is influenced by what two things?   1. Aortic pressure, 2. The pumping activity of the ventricles  
During ventricular systole   Coronary vessels compress, Myocardial blood flow ceases, Stored myoglobin supplies sufficient oxygen  
During ventricular diastole   oxygen and nutrients are carried into the heart  
What 4 things diffuse between the blood and interstitial fluid along concentration gradients   Oxygen, carbon dioxide, nutrients, and metabolic wastes  
Oxygen and nutrients pass from   the blood to tissues  
Carbon dioxide and metabolic wastes pass from   tissues to the blood  
Water-soluble solutes pass through   clefts and fenestrations  
Lipid-soluble molecules diffuse directly through   endothelial membranes  
Direction and amount of fluid flow depends upon the difference between________ pressure & ____________ pressure   Capillary hydrostatic pressure (HPc), Capillary colloid osmotic pressure (OPc)  
HPc   pressure of blood against the capillary walls:  
HP tends to force ______ through_________ __________   fluids; capillary walls  
HP Is greater at the arterial or venule end of a bed?   arterial  
OPc created by   nondiffusible plasma proteins, which draw water toward themselves  
NFP   considers all the forces acting on a capillary bed  
NFP (formula) (HPc – HPif) – (OPc – OPif)    
At the arterial end of a bed,_______ forces dominate   hydrostatic (fluids flow out)  
At the venous end of a bed, _________forces dominate   osmotic (fluids flow in)  
More fluids enter the tissue beds than return blood, and the excess fluid is returned to the blood via the   lymphatic system  
Circulatory shock   any condition in which blood vessels are inadequately filled and blood cannot circulate normally  
Circulatory Shock Results in   inadequate blood flow to meet tissue needs  
Three types of Circulatory Shock include   Hypovolemic, Vascular, Transient, Cardiogenic  
Hypovolemic shock   results from elevated heart rate and intense vasoconstrictionlarge-scale blood loss  
Vascular shock   normal blood poor circulation and a drop in blood pressurevolume but extreme vasodilation  
Transient vasular shock   can be due to vasodilation of cutaneous bloodprolonged exposure to heat (sunbathing) vessels  
Cardiogenic shock   the heart cannot sustain normal blood flow – usually related to myocardial damage (heart attacks)  
The vascular system has two distinct circulations   Pulmonary circulation & Systemic circulation  
Pulmonary circulation   short loop that runs from the heart to the lungs and back to the heart  
Systemic circulation   routes blood through a long loop to all parts of the body and returns to the heart  
The endothelial lining of blood vessels arises from   mesodermal cells mesodermal cells collect in  
Blood islands form   rudimentary vascular tubes  
The heart pumps blood by the fourth week of development thru______ ________ tubes   rudimentary vascular tubes  
2 types of Fetal shunts   foramen ovale and ductus arteriosus  
During development Fetal shunts bypass   nonfunctional lungs  
During development The ductus venosus bypasses   the liver  
During development The umbilical vein and arteries circulate   blood to and from the placenta  
At birth, what two things close?   fetal shunts and bypasses  
what are trouble-free during youth?   Blood vessels  
Vessel formation occurs   1. As needed to support body growth  
For wound healing 2.To rebuild vessels lost during menstrual cycles3. What 3 things occure With aging?   varicose veins, atherosclerosis, and increased blood pressure  
   
   
   
   


   


 
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