Chapter 15Chapter 15

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Dee Unglaub Silverthorn, Ph.D.

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^UMAN

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^HYSIOLOGY

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^HYSIOLOGY

PowerPoint^® Lecture Slide Presentation by

Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University

AN INTEGRATED APPROACH

T H I R D E D I T I O N

Chapter 15 Chapter 15

Blood Flow and the Control of Blood Pressure

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About this Chapter About this Chapter

• How various blood vessels are constructed and role in circulation

• Components of "blood pressure", role and measurement

• Product exchange at the capillary beds

• Lymph vessels, distribution and role in circulation

• How blood pressure and circulation are regulated

• Key components of cardiovascular disease

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• Arteries: blood from heart

• Strong & Elastic

• Conduct blood to capillaries

• Sphincters

• Capillaries: exchange with cells

• Veins

• Return blood to heart

• Valves

The Blood Vessels and the Cardiovascular System The Blood Vessels and the Cardiovascular System

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The Blood Vessels and the Cardiovascular System The Blood Vessels and the Cardiovascular System

Figure 15-1: Functional model of the cardiovascular system

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• Endothelium

• Elastic tissues

• Rebounds

• Evens flow

• Smooth muscles

• Fibrous tissue

• Tough

• Resists stretch

Make Up of Blood Vessels: Arteries and Arterioles Make Up of Blood Vessels: Arteries and Arterioles

Figure 15-2: Blood vessels

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• Endothelium: one cell thick

• Continuous

• Fenestrated

• Basement membrane

Make Up of Blood Vessels: Capillaries Make Up of Blood Vessels: Capillaries

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Make Up of Blood Vessels: Capillaries Make Up of Blood Vessels: Capillaries

Figure 15-16: Types of capillaries

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• Thinner walls

• Larger diameter

• Closer to skin

• Less muscle

• Less elastic

Make Up of Blood Vessels:

Veins and Venules (Contrasted to Arteries) Make Up of Blood Vessels:

Veins and Venules (Contrasted to Arteries)

Figure 15-3: Metarterioles

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• Normal body maturation and growth

• Endometrium

• Endurance training

• Abnormal growth to service cancerous tissue

• Wound repair and consequences

• Failure to regrow in heart tissues after heart attack

• Failure to regrow in brain after stroke Angiogenesis: Growth of New Blood Vessels

Angiogenesis: Growth of New Blood Vessels

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• Pulsatile: surges in arteries

• Elastic rebound evens & maintains pressure

Blood Pressure:

Generated by Ventricular Contraction Blood Pressure:

Generated by Ventricular Contraction

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Blood Pressure:

Generated by Ventricular Contraction Blood Pressure:

Generated by Ventricular Contraction

Figure 15-4: Elastic recoil in the arteries

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Blood Pressure (BP): Measurements Blood Pressure (BP): Measurements

• "Blood pressure"

• Systolic over diastolic

• About 120/80 mmHg

• Sphygmomanometer

• "Estimate of pressure"

• Korotkoff sounds

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Blood Pressure (BP): Measurements Blood Pressure (BP): Measurements

Figure 15-7: Measurement of arterial blood pressure

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• Pulse pressure = Systolic–Diastolic

• Mean arterial pressure (MAP) = Diastolic + 1/3 pulse pressure

More Blood Pressures:

Pulse and Mean Arterial Pressures More Blood Pressures:

Pulse and Mean Arterial Pressures

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More Blood Pressures:

Pulse and Mean Arterial Pressures More Blood Pressures:

Pulse and Mean Arterial Pressures

Figure 15-5: Pressure throughout the systemic circulation

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Factors Controlling MAP :

The Driving Pressure for Blood Flow Factors Controlling MAP :

The Driving Pressure for Blood Flow

• Blood volume

• Cardiac output

• Resistance

• Distribution

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Factors Controlling MAP :

The Driving Pressure for Blood Flow Factors Controlling MAP :

The Driving Pressure for Blood Flow

Figure 15-10: Factors that influence mean arterial pressure

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Slide Source Hypertension Online www.hypertensiononline.org

-Blockers ACE Inhibitors

AT1 Blockers

Direct renin inhibitors

1-Blockers

2-Agonists All CCBs Diuretics Sympatholytics

Vasodilators

-Blockers

Non-DHP CCBs Diuretics

Blood Blood

Pressure

Pressure == ^Cardiac^Cardiac_Output_Output 

ACE = angiotensin-converting enzyme; AT₁ = angiotensin type 1;

CCBs = calcium channel blockers; DHP = dihydropyridine

Antihypertensive Drug Classes: Action Sites Antihypertensive Drug Classes: Action Sites

Total Peripheral Total Peripheral

Resistance Resistance

AntihypertensiveAntihypertensive Drug ClassesDrug Classes

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Slide Source Hypertension Online www.hypertensiononline.org

Classes of Antihypertensive Drugs Classes of Antihypertensive Drugs

• Aldosterone receptor antagonists (blockers)

• Angiotensin II antagonists

• Angiotensin-converting enzyme inhibitors

 -Blockers

 1-Selective – Nonselective

 -Blockers

 -1/-2

 -1 predominant

 /

– Intrinsic sympathomimetic activity

• Calcium channel antagonists – Nondihydropyridine

– Dihydropyridine

• Central 2 agonists

• Direct renin inhibitors

• Direct vasodilators

• Diuretics

– Thiazide-type – Loop-type

– Potassium-sparing

• Ganglionic blockers

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Arteriole Resistance: Control of Local Blood Flow Arteriole Resistance: Control of Local Blood Flow

• Myogenic auto regulation

• Paracrines:

• Hyperemia

• Sympathetic nerves – CNS

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Distribution of Blood in the Body Organs Distribution of Blood in the Body Organs

Figure 15-13: Distribution of blood in the body at rest

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• Lowest Velocity

• Hydrostatic

pressure drops

Capillary Blood Flow:

Greatest Total Cross Sectional Area Capillary Blood Flow:

Greatest Total Cross Sectional Area

Figure 15-17: The velocity of flow depends on the total cross- sectional area

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Capillary Exchange:

Colloidal Osmotic Pressure is Constant Capillary Exchange:

Colloidal Osmotic Pressure is Constant

• Proteins stay in capillary

• Water, oxygen, glucose – move out

• CO2, N wastes, water – move in

• Bulk flow out on arterial side, in on venous side

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• High on arterial side – bulk flow out

• Low on venous side – bulk flow in

• Fenestrations &/or leaky joints speed exchange

Capillary Exchange: Hydrostatic Pressure Declines Capillary Exchange: Hydrostatic Pressure Declines

Figure 15-18a: Fluid exchange at the capillary

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• Net filtration – net absorption = net out flow

• About 2 L/day collected by lymph vessels Net Out Flow Into ECF

Net Out Flow Into ECF

Figure 15-18b: Fluid exchange at the capillary

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Lymphatic System: Structure and Roles (overview) Lymphatic System: Structure and Roles (overview)

• Lymphatic structures

• Capillaries with valves

• Lymph vessels

• Lymph nodes & organs

• Immune defense: lymphocytes

• Transport of fats

• Collects excess ECF

• Returns to plasma

• Edema

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Lymphatic System: Structure and Roles (overview) Lymphatic System: Structure and Roles (overview)

Figure 15-19: The lymphatic system

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Lymphatic System: Overview Lymphatic System: Overview

• Consists of two semi-independent parts

• A meandering network of lymphatic vessels

• Lymphoid tissues and organs scattered throughout the body

• Returns interstitial fluid and leaked plasma proteins back to the blood

• Lymph – interstitial fluid once it has entered lymphatic vessels

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Figure 20.2a

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Lymphatic System: Overview Lymphatic System: Overview

Figure 20.1a

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Lymphatic Capillaries Lymphatic Capillaries

• Similar to blood capillaries, with modifications

• Remarkably permeable

• Loosely joined endothelial minivalves

• Withstand interstitial pressure and remain open

• The minivalves function as one-way gates that:

• Allow interstitial fluid to enter lymph capillaries

• Do not allow lymph to escape from the capillaries

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Lymphatic Capillaries Lymphatic Capillaries

• During inflammation, lymph capillaries can absorb:

• Cell debris

• Pathogens

• Cancer cells

• Cells in the lymph nodes:

• Cleanse and “examine” this debris

• Lacteals – specialized lymph capillaries present in intestinal mucosa

• Absorb digested fat and deliver chyle to the blood

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Lymphatic Trunks Lymphatic Trunks

• Lymph is delivered into one of two large trunks

• Right lymphatic duct – drains the right upper arm and the right side of the head and thorax

• Thoracic duct – arises from the cisterna chyli and drains the rest of the body

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Lymph Transport Lymph Transport

• The lymphatic system lacks an organ that acts as a pump

• Vessels are low-pressure conduits

• Uses the same methods as veins to propel lymph

• Pulsations of nearby arteries

• Contractions of smooth muscle in the walls of the lymphatics

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Regulation of Blood Pressure and Heart Rate Regulation of Blood Pressure and Heart Rate

• Medullary cardiac control center (Brainstem)

• Cardioacceleratory Center

• Cardioinhibitory Center

• Baroreceptor reflex

• Carotid

• Aortic

• Kidney: blood volume

• Hypothalamus & Cortex: stress, blushing, etc.

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Regulation of Blood Pressure Regulation of Blood Pressure

Figure 15-22: The baroreceptor reflex: the response to increased blood pressure

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• Risk Factors:

• Smoking

• Obesity

• Diabetes

• Genes

• Diseases:

• Hypertension

• Stroke

• "Heart Attack"

Cardiovascular Diseases: #1 killer Cardiovascular Diseases: #1 killer

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• LDL build up

• Plaque

•  Flow

• Rupture

• Clot

• Blocked flow

• Tissue death

Mechanism of Atherosclerosis Mechanism of Atherosclerosis

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We now understand that atherosclerosis is a chronic inflammation of arteries, which develops over decades in response to the biologic effects of risk factors.

Atherogenesis begins as a qualitative change to intact endothelial cells; when subjected to oxidative, hemodynamic, or biochemical stimuli (from smoking, hypertension, or

dyslipidemia) and inflammatory factors, they change their permeability to promote the entry and retention of blood-borne monocytes and cholesterol-containing LDL particles.

Inflammation and biochemical modifications ensue, causing endothelial and smooth-

muscle cells to proliferate, produce extracellular matrix molecules, and form a fibrous cap over the developing atheromatous plaque.

Plaques lead to clinical symptoms by producing flow-limiting stenoses (causing stable angina) or by provoking thrombi that interrupt blood flow on either a temporary basis (causing unstable angina) or a permanent one (causing myocardial infarction).

Physical disruption (rupture) of the plaque exposes procoagulant material within the core of the plaque to coagulation proteins and platelets, triggering clotting.

How Atherosclerosis Develops

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• Blood vessels, anatomy & role in circulation

• Measuring blood pressures, MAP & pulse pressure

• Role of resistance in BP and distribution of blood

• Autoregulation, baroreceptros, medullary cardiac control center and CNS regulation of blood pressure & distribution

Summary Summary

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• Hydrostatic & colloidal osmotic pressures direct bulk flow in capillary exchange by diffusion, fenestrations & leaky joints

• Role of lymphatic system to return excess ECF to plasma

• Atherosclerosis common to several cardiovascular diseases

Summary Summary