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ch 20-Cardiovasc BV

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

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
Created by: salonge1010