Pathophysiology 1 - Chapter 15 and 16

What does the circulatory circuit do?

• In charge of absorption and delivery of nutrients

• Oxygen uptake and delivery

• Removal of waste products from tissues to excretory organs.

How long does it take to move 5 L of blood through the entire circuit?

~1 minute

Lymphatic circulation does what?

• collect excess fluid and that comes from vascular network

What do arteries contain in comparison to veins?

Elastic tissue, there is only elastic tissue in large veins

What does the intima layer function in?

Endothelial cells in direct contact with the blood as it flows through vessel

• periodically protrudes into the lumen, creating valves that prevent backflow

Media layer

smooth muscle tissue

• thickest section in arteries

Adventitia layer

collagenous connective tissue

• thickest section in veins

True or False: Blood flow is measured as a given number of liters or mililiters per second, minute, or hour

True

Anatomy of capillaries

single thickness of endothelial cells attached to a basement membrane

Principle of flow is known as

hemodynamics of the circulatory system

• governs quantity of blood passing by a given point in specific period

Blood flow definition

Movement along a pressure gradient within the vascular bed

Describe how pressure works

Blood moves from areas of higher pressures (arteries) to an area of lower pressure (veins); the greater the pressure difference, the greater the blood flow

Resistance definition

Opposing forces that deter blood flow; as resistance increases, blood flow decreases  

What are the determinants of vascular resistance?

• Vessel length

• Vessel radius (diameter)

• Blood viscosity

*elastic flexibility of the tube is also a factor

True or False: The longer the blood vessels, the higher the resistance and lower the flow

True

Flow =

Pressure/Resistance

Blood pressure =

flow (cardiac output) x resistance

Resistance =

Pressure/Flow

The _____ the blood vessel, the higher the resistance, the lower the flow

narrower

Laminar flow

fastest blood flow in the center of stream

Turbulent flow

an interruption in the forward current of blood flow by crosswise flow

turbulent flow may manifest as

• bruit

• thrill

• thrombus formation (blood clot affecting flow)

  • ex. of pathologic cause of turbulence

What is clinically important in capillaries?

Capillary fluid pressure and plasma colloid osmotic pressure

Capillary fluid pressure is the

Blood pressure inside the capillary (force that pushes fluid out of vessel)

What are the controls of blood flow?

Extrinsic (central control) and Intrinsic (local control)

Describe extrinsic blood flow

• smooth muscle cells are innervated by nerve fibers from the sympathetic nervous system

• all blood vessels except small venules and capillaries contain smooth muscle cells

• arteries > veins more smooth muscle

• smooth muscle cells have a1 adrenergic receptors that respond to the SNS neurotransmitter, noradrenaline results in vasoconstriction

• skeletal muscle blood vessels contain B2 adrenergic receptors which respond to epinephrine (adrenaline) = vasodilation

Describe intrinsic blood flow

• autoregulation 

  • when vascular smooth muscle is stretched, it contracts in response causing vasoconstriction

• endothelial cells also play an important role in vessel dilation and constriction

  • produces nitric oxide gas which causes dilation by relaxing neighboring smooth muscle cells

Autoregulation

is ability of blood vessels within organs to maintain a relatively constant blood flow regardless of changes in arterial pressure

What happens when systemic vascular resistance is increased?

It causes the heart to work harder to meet metabolic demands of the body

Blood vessel obstruction in the arterial system obstruction manifests as

distal ischemia

Blood vessel obstruction in the venous system obstruction manifests as

edema

Thrombosis is initiated by alterations in one or more of the following

• blood flow: slow or turbulent flow

• blood vessel wall: damage or inflammation to the intimal wall of vessel

• blood coagulability: emergence of a hypercoagulable state

Thrombus

stationary blood clot formed within a vessel or a chamber of the heart

Clot is composed of

aggregated platelets, clotting factors and fibrin that adhere to the vessel wall

Arterial thrombosis is classified as

a clot within an artery reduces flow and increases turbulence which enhances thrombus enlargement and formation of more thrombi

Decreased distal flow can cause ischemia which can cause

• arterial occlusion

• myocardial infarction

• stroke

True or False: Venous thrombosis symptoms may be absent or maybe life-threatening secondary to pulmonary embolism

True

Describe venous thrombosis

clot in a vein altering venous return which impairs the removal of metabolic waste and produces swelling

Plebitis

inflammation that occurs in a vein

Thromboplebitis

Inflammation that occurs in a vein that is accompanied with a clot

Embolus

a traveling clot that is propelled forward in the bloodstream to a distant point where it lodges to produce a new site of obstruction

Pulmonary embolism

clot goes through the right heart and then most commonly lodges in the lung arteries

clots dislodged from the left side of the heart usually end up in the brain artery can cause this

Ischemic stroke

Emboli can be produced by other causes

• fat aggregates

• metastasizing tumor cells inside the bloodstream forming aggregate

• bacterial emboli

• air bubbles (from IV)

Pulmonary Embolism clinical manifestation

• may be asymptomatic or present vague signs and symptoms

• sudden shortness of breat

• chest pain

• sudden death

Stroke manifestation depending on the area of the brain affected

• loss of cognitive function

• motor changes

• various levels of sensory loss

vasospasms can cause

distal hypoxia or hemorrhagic stroke

Atherosclerosis means

hardening of the arteries

What is atherosclerosis an underlying condition of?

• hypertension

• renal disease

• cardiac disease

• peripheral arterial disease

What is the pathologic origin for the vast majority of arterial disease?

atherosclerosis

Leading cause of death in the US and western europe

atherosclerosis

Where does atherosclerosis mostly develop in

large and medium size arteries

• mainly coronary (associated with most mortality; coronary artery disease)

Where are aneurysms mostly found?

In cerebral circulation and the thoracic and abdominal aorta

Aneurysms are classified as true or false aneurysms, true aneurysms include

• saccular: one sided balloon

• fusiform: both sides balloon out

Alterations in venous flow can be accompanied with

edema, venous stasis, inflammation, ulcers, and pain

Describe Raynaud Syndrome

• extreme vasoconstriction producing cessation of flow to fingers and toes

  • color changes: pale (cyanosis), red (hyperemia)

  • numbness and cold triggers

• treatment: enhances circulation through relaxation, calcium-channel blockers, sympatholytic drugs, prostaglandins

Incompetent valves can produce

• varicose veins: superficial veins affected

• chronic venous insufficiency: deep veins affected

• deep vein thrombosis: could lead to life threatening PE

True or False: lymphedema is most common in the US because of lymph node removal and radiation

True

Primary lymphedema

results from congenital anomaly or dysfunction of the lymphatic system

Secondary lymphedema

associated with a disease process or latrogenic

• ex. lymph node removal treatments

Systemic arterial blood pressure is the physiologic result of

cardiac output and resistance to the ejection of blood from the heart

systemic vascular resistance (SVR)

resistance to ejection into arterial circulation

SVR can be altered by

constricting or relaxing arterial smooth muscle

Cardiac output =

stroke volume x heart rate

Stroke volume

volume of blood pumped out of ventricle with each contraction

Systolic pressure

exerted when blood is ejected from ventricles (high)

Diastolic pressure

sustained pressure when ventricles relax (lower)

BP is directionally proportional to blood volume and is controlled by

hormones

What is used clinically as part of cardiovascular assessment?

Mean Arterial Pressure Map (MAP) which is calculated average pressure within the circulatory system

Out of the Korokthoff sounds, which is classified as the systolic and diastolic pressure

• Systolic: Initation of a clear tapping sound

• Diastolic: Disappearance of sound

Guidelines for hypertension grade 1

• Systolic BP: 130-139 mmHg

• Diastolic BP: 80-89 mmHg

Guidelines for hypertension grade 2

• Systolic BP: ≥ 140 mmHg

• Diastolic BP: ≥ 90 mmHg

What is the short term regulation mechanism mediated by?

The sympathetic branch of the autonomic nervous system

What are long term regulation mechanisms based on?

interplay of neural, hormonal, and renal interactions

• intimately connected with the body’s fluid volume

What activates the vasomotor center directly and indirectly?

By various stimuli or indirectly via pressure-sensitive baroreceptors (which monitor MAP variations)

Beta receptors of the heart increase or decrease heart rate?

Increase

Stimulation of SNS results in

the release of neurotransmitters: noradrenaline and adrenaline

a1 receptors on smooth muscle of arterioles get activated which causes

vasoconstrictions

When the kidney is stimulated by low arterial pressure, what happens?

It releases renin, which activates angiotensinogen to become angiotensin I

When Angiotensin I gets in contact with ACE, it gets converted to

angiotensin II, a potent vasoconstrictor and stimulates the release of aldosterone by the adrenal cortex

Aldosterone function

a hormone that causes reabsorption of sodium and water passively follows

What is the most common primary diagnosis in the US?

Hypertension

Hypertension increases morbidity and mortality associated with

heart disease, kidney disease, peripheral vascular disease, and stroke

Hypertensive crisis

Systolic over 180 and/or diastolic over 120, with patients needing prompt changes in medication if there are no other indications of problems, or immediate hospitalization if there are signs of organ damage

True or False: Primary essential hypertension, majority of the cases are caused unknown

True

• Idiopathic

• BP consistently above 130/90 mmHg

What does the silent killer refer to?

The damage has already occurred to organs before diagnosis is made

What constitutes a hypertensive emergency?

sudden increase in either or both systolic or diastolic blood pressure with evidence of end-organ damage

Most common cause of adult secondary hypertension

Hyperaldosteronism

• adenoma of adrenal cortex

Secondary hypertension refers to

Hypertension attributed to a specific identifiable pathology or condition

End organ damage

A function of stage and duration of hypertension

• renal failure, stroke, heart disease

Increased myocardial work =

heart failure

glomerular damage =

kidney failure

Microcirculation affects the

eyes

Increased pressure in cerebral vasculature can =

hemorrhage (stroke, brain)

In the western world there is a __% lifetime risk for the development of hypertension

90%