Question | Answer |
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 |
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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 vasoconstrictionlarge-scale blood loss |
Vascular shock | normal blood poor circulation and a drop in blood pressurevolume but extreme vasodilation |
Transient vasular shock | can be due to vasodilation of cutaneous bloodprolonged 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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