Blood Vessels & Lymphatic Immunity PP’s(6) A&P2

Classes of Blood Vessels

Arteries

•Carry blood away from heart

•Arterioles

•Are smallest branches of arteries

•Capillaries

•Are smallest blood vessels

•Location of exchange between blood and interstitial fluid

•Venules

•Small veins

•Collect blood from capillaries

•Veins

•Return blood to heart

The Structure of Vessel Walls

Walls of arteries and veins have three layers

1.Tunica intima: Inner layer

2.Tunica media: Middle layer

3.Tunica externa: Outer layer

Tunica Intima

The Tunica Intima: Inner layer of blood vessel

•Includes: “ENDOTHELIUM”

•The inner endothelial lining

•Simple squamous cells (endothelial cells)

•Surrounding connective tissue layer

•In arteries, there is an outer layer of elastic fibers (Internal elastic membrane)

Tunica Media

The Tunica Media: Middle layer of blood vessel

•Concentric sheets of smooth muscle

•Contraction: LUMEN Decreases “VASOCONSTRICTION“

•Relaxation: LUMEN Increases “VASODILATION”

•Binds to inner and outer layers of vessel wall

•Thicker in arteries — (Muscular) than veins

•In arteries, external elastic membrane of the tunica media separates the tunica media from the tunica externa

Tunica Externa

The Tunica Externa: Outer layer of blood vessel

•Connective tissue sheath

•Stabilizes and anchors vessel to adjacent tissues

•In arteries

•Contains collagen and elastic fibers

•In veins

•Thicker than tunica media

•Contains collagen and elastic fibers and Smooth muscle cells

Vasa vasorum

(“vessels of vessels”)

•Small arteries and veins

•In walls of arteries and veins

•Supply cells of tunica media and tunica externa with blood

Arteries

Elasticity allows arteries to expand and constrict passively to adjust to changes in blood pressure

•Contractility

•Arteries change diameter actively

•Controlled primarily by sympathetic division of ANS

•Vasoconstriction

•The contraction of arterial smooth muscle

•Vessel diameter DECREASES

•Vasodilation

•The relaxation of arterial smooth muscle

•Vessel diameter INCREASES

Arteries (Heart > Capillaries, Arteries Change)

From elastic arteries

•To muscular arteries

•To arterioles

•Elastic Arteries (conducting arteries)

•Largest diameter (e.g., pulmonary trunk and aorta)

•Tunica media has many elastic fibers & fewer muscle cells

•Elasticity

•Withstand pressure changes

•Recoil evens out “pulse force”

Muscular Arteries

Branch off elastic arteries

•“Distribution arteries”

•Are medium sized (most arteries)

•Tunica media has many muscle cells, less elastic

•Significance?

Arterioles

Are small

•Have little or no tunica externa

•Have thin or incomplete tunica media

•Arteriole diameter can change according to local conditions and with sympathetic or endocrine stimulation

•Ex: Dilate when local tissues have low oxygen (Dilated arteries decrease resistance to increase blood flow)

•Constricted arteries oppose blood flow creating Resistance (R)

•Arterioles are resistance vessels that function to regulate blood flow

Aneurysm

A bulge in an arterial wall “HEMORRHAGIC STROKE”

•Is caused by weak spot in elastic fibers

•Pressure may rupture vessel leading to hemorrhage

•Most dangerous areas for aneurysm are the brain or the aorta

Capillaries

Smallest vessels with thin walls

•Microscopic capillary networks permeate all active tissues

•Capillary function

•Location of all exchange functions of cardiovascular system

•Materials diffuse between blood and interstitial fluid or blood and air

Capillary Structure

Endothelium inside a thin basement membrane

•No tunica media

•No tunica externa

•Two types of capillary

•Continuous capillary

•Fenestrated capillary

Continuous Capillaries

Have complete endothelial lining

•Most common: found in active tissues exceptepithelia and cartilage

•Functions of continuous capillaries

•Permit diffusion of water, small solutes, and lipid-soluble materials

•Block blood cells, plasma proteins, macromolecules

Specialized Continuous Capillaries

Are in CNS, thymus

•Have very restricted permeability due to tight junctions between endothelial cells

•For example, the blood–brain barrier

Fenestrated Capillaries

Have pores in endothelial lining

•Permit rapid exchange of water and large solutes between blood and interstitial fluid

•Are found in:

•Endocrine organs (pituitary, thyroid)

•Kidneys

•Intestinal tract

Sinusoids (Sinusoidal Capillaries)

Have gaps between adjacent endothelial cells and thin or absent basement membrane

•Liver

•Spleen

•Bone marrow

•Endocrine organs

•Permit free exchange of water and large plasma proteins between blood and interstitial fluid

•Macrophages monitor blood at sinusoids (remember RBC removal?)

•Liver secretes plasma proteins into the blood at sinusoids

Capillary Beds (Capillary Plexus)

Dozens of capillaries that connect an arteriole to a venule

•Precapillary Sphincter

•Circular band of muscle that guards entrance to each capillary

•Constricts to slow or stop blood flow (blood diverts to another capillary)

•Relaxes to allow blood to flow into capillary

Collaterals

Multiple arteries that contribute to one capillary bed

•Allow circulation if one artery is blocked

•Arterial anastomosis

•Fusion of two collateral arteries as they form an arteriole

•Arteriovenous anastomosis

•Direct connections between arterioles and venules

•Bypass the capillary bed when dilated

Vasomotion

Contraction and relaxation cycle of capillary sphincters

•Causes blood flow in capillary beds to constantly change routes

•Controlled locally by chemical and dissolved gas concentrations

•Ensures that all areas get adequate oxygen, glucose, waste removal, etc

Veins

Collect blood from capillaries in tissues and organs and return blood to heart

•Are larger in diameter than arteries

•Have thinner walls than arteries

•Have lower blood pressure

Venous Valves

Folds of tunica intima

•Muscular compression pushes blood toward heart

•Valves prevent blood from flowing backward

Venules

Very small veins

•Collect blood from capillaries

Medium-sized veins

•Thin tunica media and few smooth muscle cells

•Tunica externa with longitudinal bundles of elastic and collagen fibers

•Large Veins

•Thin tunica media

•Thick tunica externa (elastic and collagen)

•EX: ____________________

The Distribution of Blood

NOT distributed evenly

•Heart, arteries, and capillaries, pulmonary circuit

•30–35% of blood volume

•Venous system

•65-70% of blood volume

•20% of blood is in the large venous networks of the liver, bone marrow, and skin

Capacitance of a Blood Vessel

Relationship between blood volume and blood pressure (the tendency to stretch and shrink without great changes in pressure)

•Veins (capacitance vessels) stretch/shrink more than arteries

•Can accommodate large changes in blood volume without changing venous pressure (perfect reservoir)

Venous Response to Blood Loss

Vasomotor centers stimulate sympathetic nerves

1.Systemic veins constrict (venoconstriction)

2.Veins (esp. liver, skin, and bone marrow) redistribute venous reserve

Capillary blood flow

Determined by pressure (P) and resistance (R) in the cardiovascular system

•Proportional to pressure

•Increase Pressure __________________

•Inversely proportional to resistance

•Increase Resistance ________________

Pressure (P)

The heart generates P to overcome resistance  

•Absolute pressure is less important than pressure gradient

•The Pressure Gradient (P): The difference in pressure between two points

Blood Flow (F)

Is proportional to the pressure difference (P)

•Divided by R

Measuring Pressure

1.Blood pressure (BP)

•Arterial pressure (mmHg)

2.Capillary hydrostatic pressure (CHP)

•Pressure within the capillary beds (mmHg)

3.Venous pressure

•Pressure in the venous system (mmHg)

Order of Arteries/ Veins

A: Elastic Artery > Muscular Artery > Arteriole

V: Large Vein > Medium - Sized Vein > Venule

Circulatory Pressure

Circulatory Pressure: ∆P across the systemic circuit (about 100 mm Hg)

•Circulatory pressure must overcome total peripheral resistance , TPR

•R of entire cardiovascular system

•Determined by:

•Vascular resistance

•Blood viscosity

•Turbulence

Vascular Resistance

Due to friction between blood and vessel walls

•Depends on vessel length and vessel diameter

•Adult vessel length is constant

•Vessel diameter varies by vasodilation and vasoconstriction

•R increases exponentially as vessel diameter decreases

“Straw / tunnel”

Viscosity

Resistance to flow caused by molecules and suspended materials in a liquid

•Whole blood viscosity is about five times that of water

•Generally stable; Anemia, polycythemia may affect viscosity

Turbulence

Swirling action that disturbs smooth flow of liquid

•Occurs in heart chambers and great vessels

•Generally stable; Atherosclerotic plaques cause abnormal turbulence

An Overview of Cardiovascular Pressures

Cardiovascular Pressures and Velocity of blood flow are related to

•Vessel diameter

•Total cross-sectional area: area of all selected vessels combined (not just a single vessel)

Pressure and Resistance

Increase TOTAL arterial cross section area: BP decreases, flow rate decreases

•Capillaries: Largest cross section area, slowestflow (Importance?)

•Decrease venous cross section area: BP continues to decrease, but flow rate increases

Arterial Blood Pressure

maintains blood flow

•Must overcome TPR to ensure blood flows through circulation

•NOT constant

•Systolic pressure

•Peak arterial pressure during ventricular systole

•Diastolic pressure

•Minimum arterial pressure during ventricular diastole

Arterial Pressure

Pulse pressure

•Difference between systolic pressure and diastolic pressure

•Represents the force of the heart’s contraction

•Mean arterial pressure (MAP)

•Single blood pressure value

•MAP = diastolic pressure + 1/3 pulse pressure

Normal Arterial BP

120/80

•Hypertension

•Abnormally high blood pressure

•Greater than 130/80

•Increases workload on the heart leading to damage to the myocardium

•Hypotension

•Abnormally low blood pressure

•Numeric value varies, athletes “normal” BP may look very low

•Rare, most cases caused by over treating HTN

Venous Pressure and Venous Return

Venous Return: The amount of blood arriving at right atrium each minute

•Low effective pressure in venous system

•16 mmHg (18 mmHg at venules, 2 mmHg at Vena Cava) verses 65 mmHg in the arterial system

•Flow speed increases through venous system

•Veins get larger

•Cross sectional area decreases

Venous Return is assisted by

Muscular compression and one way valves

•Compression of veins by skeletal muscles in legs pushes blood toward heart

•One-way valves prevent back flow when muscles relax

•The respiratory pump

•Inhalation: decreases thoracic pressure, increasesabdominopelvic pressure, blood flows from high pressure to low pressure (blood pushed from abdominopelvic region to thoracic cavity)

•Exhalation: increases thoracic pressure, decreasesabdominopelvic pressure, pushes blood into right atrium

Capillaries

Pressure is low, cross sectional area and resistanceare high:

•Blood flows slowly through capillaries

•Maximal time for capillary exchange

•Capillary Exchange

•VITAL to homeostasis

•Moves materials across capillary walls by:

•Diffusion

•Filtration

•Reabsorption

Diffusion

Movement of ions or molecules from high concentration to lower concentration

•Diffusion routes across capillary walls

1.Water, ions, and small molecules (glucose)

•Diffuse between adjacent endothelial cells

•Through channels in plasma membranes

•Or through fenestrated capillaries

Diffusion Routes

2. Large, water-soluble compounds

Pass through fenestrated capillaries

3. Lipids and lipid-soluble materials such as _________

Diffuse through endothelial plasma membranes

4. Plasma proteins

Pass through large gaps in sinusoids

Filtration

Removal of solutes as a solution is driven across a porous membrane

•Driven by hydrostatic pressure

•Physical force of a liquid against a surface

•Pushes water from area of high pressure to lower pressure

•In capillaries:

•Water and small solutes forced across capillary wall into interstitial fluid

•Larger solutes left in bloodstream (______________)

Reabsorption

Movement back into the blood

•The result of osmosis

•Blood colloid osmotic pressure (BCOP)

•Equals pressure required to prevent osmosis in the blood

•The higher the solute concentration, the higher the solutions osmotic pressure

•Caused by suspended blood proteins that are too large to cross capillary walls

Interplay — Filtration and Reabsorption

1. Ensures that plasma and interstitial fluid are in constant communication and mutual exchange

2.Accelerates distribution of nutrients, hormones, and dissolved gases throughout tissues

3.Has a flushing action that carries bacterial toxins to lymphatic tissues and organs responsible for providing immunity to disease

Net hydrostatic / osmotic pressure

Control filtration and reabsorption through capillaries 

•Factors that Contribute to Net Hydrostatic Pressure

1.Capillary hydrostatic pressure (CHP)

2.Interstitial fluid hydrostatic pressure (IHP)

•Net capillary hydrostatic pressure tends to push water and solutes:

•Out of capillaries

•Into interstitial fluid

Net Capillary Colloid Osmotic Pressure

Is the difference between:

1.Blood colloid osmotic pressure (BCOP)

2.Interstitial fluid colloid osmotic pressure (ICOP)

•Pulls water and solutes:

•Into a capillary

•From interstitial fluid

Net Filtration Pressure (NFP)

Causes the movement of materials into or out of the capillary blood

•The difference between:

•Net hydrostatic pressure

•Net osmotic pressure

NFP = (CHP – IHP) – (BCOP – ICOP)

Capillary Exchange Occurs because…

…of Net Filtration Pressure

•NFP is not constant across capillary bed

•At arterial end of capillary:

•CHP is high, NFP is high/positive

•Fluid moves out of capillary, into interstitial fluid

•At venous end of capillary:

•BCOP is high, NFP is negative

•Fluid moves into capillary, out of interstitial fluid

Capillary Exchange & NFP

Transition point between filtration and reabsorption is closer to venous end than arterial end

•Capillaries filter more than they reabsorb

•24 L/day filtered, 20.4 L/day reabsorbed

•Excess fluid (3.6 L/day) enters lymphatic vessels

•After traveling through lymphatic system fluid enters circulatory system via subclavian vein.

Edema

Abnormal accumulation of interstitial fluid (swelling)

•Disruption in the normal balance between hydrostatic pressure and osmotic pressure

•Fluid moves out of blood and builds up in peripheral tissues

•Causes:

•Tissue damage: Damaged capillary wall – leakage of plasma proteins – increased relative interstitial osmotic pressure

•Starvation: Decreased plasma proteins – decreased blood colloid osmotic pressure

•Increased circulatory pressure- (Increased BP, HF, clots), increased capillary hydrostatic pressure

Tissue Perfusion

Blood flow through the tissues

•Carries O2 and nutrients to tissues / organs

•Carries CO2 and wastes away from tissues / organs

Is affected by:

1.Cardiac output

2.Peripheral resistance

3.Blood pressure

When tissue perfusion is inadequate

Regulatory mechanisms adjust cardiac output, peripheral resistance, and blood pressure to improve tissue perfusion

•Autoregulation

•Neural mechanisms

•Endocrine mechanisms

Autoregulation of Blood Flow

Local factors cause immediate, localized, adjustments in blood flow

•Dilate or constrict precapillary sphincters

•Local vasodilators INCREASE blood flow at tissue level

•Low O2 or high CO2 levels

•Low pH (lactic acid buildup)

•Nitric oxide (NO)

Autoregulation of Blood Flow within Tissues

Local vasoconstrictors

•Example: thromboxanes

•Released by activated platelets

•Constrict precapillary sphincters to DECREASE blood flow at the tissue level

Auto Regulation Involves…

…the constriction or dilation of precapillary sphincters

due to local release of vasodilator or vasoconstrictor

chemicals from the tissue.

Central Regulation Involves…

…neuroendocrine mechanisms that control the total systemic circulation. This regulation involves both the cardiovascular centers and the vasomotor centers.

Neural Mechanisms

Cardiovascular (CV) centers

•Cardioacceleratory center increases cardiac output

•Cardioinhibitory center reduces cardiac output

Vasomotor Center

•Exerts sympathetic control over blood vessel diameter

•Vasoconstriction

•Increased sympathetic stimulation (increased NE)

•Stimulates smooth muscle contraction in vessel walls

•Vasodilation

•Decreased sympathetic stimulation (decreased NE)

•Stimulated smooth muscle relaxation in vessel walls

Vasomotor center monitors…

…blood via baroreceptors and chemoreceptors

•Baroreceptor reflex

•Respond to changes in blood pressure

•Chemoreceptor reflex

•Respond to changes in chemical composition, particularly pH and dissolved gases

Baroreceptor Reflexes

Stretch receptors in walls of:

1.Carotid sinuses (maintain blood flow to BRAIN)

2.Aortic sinuses (monitor blood flow to the SYSTEMIC CIRCUIT)

Baroreceptor Reflexes & BP

When blood pressure rises, increased baroreceptor input to vasomotor center:

•Inhibits sympathetic neurons (DECREASE NE)

•Causes peripheral vasodilation (DECREASE BP)

•When blood pressure falls, decreased baroreceptor input to vasomotor center:

•Stimulates sympathetic neurons (INCREASE NE)

•  Causes peripheral vasoconstriction (INCREASE BP)

Chemoreceptor Reflexes

Peripheral chemoreceptors in carotid bodies (in neck) and aortic bodies (near aortic arch) monitor arterial blood composition

•Central chemoreceptors on surface of medullaoblongatata monitor chemical composition around the brain (CSF)

Hormones and Cardiovascular Regulation

Epi and NE from adrenal medullae

•Peripheral vasoconstriction (INCREASE BP)

•Coronary vasodilation to increase blood flow to the myocardium

•Angiotensin II produced due to decreased blood pressure or blood volume

•Potent vasoconstriction (INCREASE BP)

•Causes release of ADH, Aldosterone (promote fluid retention)

Antidiuretic Hormone (ADH)

Released by posterior lobe of pituitary gland due to decreased blood pressure or blood volume

•Elevates blood pressure and volume

•Promotes water retention at kidneys

•Vasoconstriction

Natriuretic Peptides

Muscle cells in the heart produce Atrial natriuretic peptide (ANP) and Brain natriuretic peptide (BNP)

•Produced in response to excessive diastolic stretching

•Actions: Increase sodium excretion, promote water loss, decrease thirst, cause vasodilation

•Effect: Lower blood volume and blood pressure to reduce stress on heart

Pathogens

Microscopic organisms that cause disease

•Viruses

•Bacteria

•Fungi

•Parasites

The lymphatic system Includes…

…cells, tissues, and organs responsible for defending the body against:

•Environmental pathogens

•Toxins

•Abnormal body cells, such as cancers

Immunity & Defenses

Immunity: Ability to resist infection or disease

Nonspecific Defenses (innate defenses)

•Block or attack any potential infectious organism

•Cannot distinguish one attack from another 

Specific Defenses (adaptive defenses)

•Lymphocytes

•Identify, attack, and develop immunity to a specificpathogen

The Lymphatic System Includes:

1. Lymph

•A fluid similar to plasma but much fewer proteins

•Originates as IF

2. Lymphatic vessels (lymphatics): Carry lymph from peripheral tissues to the venous system

3. Lymphoid tissues: High concentration of lymphocytes, macrophages

4. Lymphoid organs: High concentration of lymphocytes, macrophages enclosed in fibrous capsule

Function of the Lymphatic System

To aid in production of lymphocytes

•T-Cells Mature in lymphatic tissues, organs

•To drain excess interstitial fluid and return to the blood

•Maintain blood volume

•Ensure similar composition of interstitial fluid throughout the body

•Immunity

•Lymph passes through lymph nodes

•Immune cells activate immune response if needed

Lymphatic Vessels

Lymphatic Vessels: Vessels that carry lymph

•Lymphatic system begins with smallest vessels: Lymphatic capillaries (terminal lymphatics)

•Lymphatic Capillaries differ from blood capillaries in four ways

1.Start as pockets rather than tubes

2.Have larger diameters

3.Have thinner walls

4.Irregular outline in sectional view

Lymphatic Capillaries

•Endothelial cells loosely bound together with overlap

•Overlap acts as one-way valve

•Allows fluids, solutes, viruses, and bacteria to enter

•Prevents return into interstitial fluid/intercellular space

Lymph Flows…

…from lymphatic capillaries to larger lymphatic vessels

•Contain one-way valves

•Travel through body with veins as they head towards trunk

Major Lymph Collecting Vessels

Superficial lymphatics are located in:

•Skin

•Mucous membranes

•Serous membranes lining body cavities

Deep lymphatics are larger vessels that accompany deep arteries and veins in the

•Neck

•Limbs

•Trunk

Superficial & Deep Lymphatics

Superficial and deep lymphatics join to form larger vessels called lymphatic trunks

•Lymphatic trunks empty into two major collecting vessels

1.Thoracic duct

2.Right lymphatic duct

The Right Lymphatic Duct

Collects lymph from the right side of the body, superior to the diaphragm

•Empties into right subclavian vein

The Thoracic Duct

The base expands into cisterna chyli which receives lymph from abdomen, pelvis, lower limbs

•Collects lymph from left arm, left side of head, neck, chest

•Empties into left subclavian vein

Lymphedema

•Blockage of lymphatic drainage from a limb

•Causes buildup of interstitial fluid, swelling

•Risk of severe infection in the area because it is essentially cut off from the rest of the lymphatic system

•Most commonly a result of removal of Damage to lymph nodes during cancer treatment

Lymphocytes

Make up 20–30% of circulating leukocytes

•Most lymphocytes are not circulating

•Types of Lymphocytes

1.  T cells

•Thymus-dependent

2.  B cells

•Bone marrow–derived

3.  NK cells

•Natural killer cells

T Cells

Make up 80% of circulating lymphocytes

Cytotoxic T Cells    

•CD8 Cells

•Attack foreign cells or cells infected by viruses

Helper T Cells

•CD4 Cells

•Stimulate function of T cells and B cells

Antigen presentation: pathogens must be processed before cytotoxic and helper T-Cells can recognize an invader

Antigen Presentation 1

Antigen Presentation occurs in two ways:

•1. APCs: Dendritic cells, Langerhans cells, Macrophages, B-Cells

•Engulf foreign cells, extract antigens, display on cell surface on MHC II

•APC “presents” the antigen to Helper T-Cell

•Activated Helper T-Cell:

•Stimulates B-Cells to make antibodies

•Help activate cytotoxic T-Cells by releasing cytokines

•Trigger destruction of pathogens engulfed by macrophages

Antigen Presentation 2

Antigen Presentation occurs in two ways:

•2. Cells display MHC I proteins on cell surface

•When antigen on MHC is normal, no response stimulated

•When antigen on MHC is abnormal (virus infected / cancer cells)

•Cytotoxic T-Cells specific for that antigen are activated

•Apoptosis of target cell (& damage to viral RNA)

•Proliferation of T-Cells specific for that antigen

Memory & Suppressor T Cells

Memory T Cells

•Formed in response to foreign substance when T-cells are activated

•Remain in body to give “immunity” to that substance

Suppressor T Cells (Regulatory T Cells)

•Limit the immune response

•Important in preventing autoimmune diseases

B Cells

•Make up 10–15% of circulating lymphocytes

•Do not directly attack invaders, responsible for antibody mediated immunity / humoral (fluid) immunity—extracellular

•Differentiate into

•Plasma Cells: produce and secrete antibodies(immunoglobulin proteins)

•Memory B Cells:

•Remain in lymph nodes after primary infection

•Lead to production of antibodies quickly if secondary infection occurs

Antigens & Immunoglobulins

Antigens

•Molecule that triggers an immune response

•Immunoglobulins (Antibodies)

•Soluble proteins that bind to specific antigens

•Aid in their removal or destruction

B-Cell Activation

Antigen binds to several surface receptors on B-Cell

•Antigen is engulfed and processed

•Antigen is displayed on MHC II and presented to Helper T-Cell

•Helper T-Cell stimulates mitosis of sensitized B-Cells

Antibody Function:

Neutralize: Blocking pathogenic regions of antigen

•Complement fixation:

•Antibody binds to antigen

•Complement proteins bind to antibody

•Inflammation, improved phagocytosis, cytolysis

•Agglutination:

•Antibody binds to multiple antigen molecules

•Clumping prevents spread

Natural Killer (NK) Cells

Make up 5–10% of circulating lymphocytes

•Attack foreign cells, virus-infected cells, and cancer cells

•Bind to target cell

•Release perforins to perforate plasma membrane of target

•Cytolysis

Lymphocyte Production

“lymphopoiesis” involves:

• (RED) Bone marrow

•Thymus

•Peripheral lymphoid tissues

Hemocytoblasts

Hemocytoblasts in bone marrow, divide into two types of lymphoid stem cells

•Group 1

•Remains in bone marrow

•Produces B cells and NK cells

•Group 2

•Migrates to thymus

•Produces T cells in environment isolated by blood–thymus barrier

T Cells and B Cells

Are located throughout the periphery, especially in lymphoid tissue

•Retaining their ability to divide is essential to immune system function

•B cells differentiate with exposure to a type of hormone called a cytokine (interleukin)

•T cells differentiate with exposure to several thymichormones as well as interleukin

Pressure, Resistance, & Flow

Vasoconstriction ^ pressure + resistance

F~^P/R

If Pressure goes up, Flow goes up

If Resistance goes up, Flow goes down

“Flow proportional to Pressure OVER Resistance”

Constriction in Big Vessel = ^P+F when leading to smaller vessels

Constriction in Small Vessel = ^R,vF when receiving from bigger vessels

A: Capillary blood flow would increase^^

What would happen to capillary blood flow if the total peripheral resistance were decreased (assume pressure stays the same)? USE F~P/R

A(2): Vasoconstriction of the muscular arteries leading to the tissue (^P=^F)

Vasodilation of arterioles leading into the tissues capillary beds

Which of the following actions would lead to an increase in blood flow to a particular tissue?

…Resistance Vessels

Arterioles are also called?…

A: Vasodilation of arteries

Considering the neural mechanisms of cardiovascular regulation, a rise in systemic blood pressure would lead to?

A: Dilation of Precapillary Sphincters

Considering the Auto regulation, Hypoxia would lead to?…(Auto reg has to do w/ Capillary Sphincters)