CHAPTER 18

DISORDERS OF BLOOD FLOW AND BLOOD PRESSURE

CHAPTER 18

DISORDERS OF BLOOD FLOW AND BLOOD PRESSURE

Essentials of Pathophysiology

PRE-LECTURE QUIZ

True/False

F  HDL is known as the “bad cholesterol.”

T Most abdominal aneurysms are asymptomatic.

F Essential (primary) hypertension is characterized by chronic elevation in blood pressure that results from some other disorder, such as kidney disease.

 F Orthostatic or postural hypotension is an abnormal rise in blood pressure that occurs when assuming the standing position from the supine position.

 T Venous insufficiency leads to tissue congestion and edema

in the lower extremities. 

PRE-LECTURE QUIZ

The __________ controls the transfer of molecules across the vascular wall, plays a role in platelet adhesion and blood clotting, and functions in the modulation of blood flow and vascular resistance.

__________, with its associated risk for the development of atherosclerosis, is a major cause of cardiovascular disease. 

__________ phenomenon is a functional disorder caused by intense vasospasm of the arteries and arterioles in the fingers and, less often, in the toes. 

__________ dissection is an acute, life-threatening condition that involves hemorrhage into the vessel wall with longitudinal tearing or separation of the vessel wall to form a blood-filled channel. 

The body uses neural mechanisms and humoral mechanisms to effect the __________-term regulation of blood pressure, which occurs over minutes or hours and is intended to correct temporary imbalances in blood pressure.

Endothelium

Aortic

Hyperlipidemia

Raynaud

Short

ARTERY STRUCTURE

Arranged in tunics or coats

Tunica intima: Endothelium

Tunica media: smooth muscle

Tunic adventitia: collagen and elastic fibers

ARTERY STRUCTURE

Tunica intima: endothelium

Tunica media: smooth muscle

Tunica adventitia: collagen and elastic fibers

QUESTION

Which vessel layer can expand to accommodate pressure changes?

a. Tunica intimab. Tunica mediac. Tunica adventitiad. Tunica externa

ANSWER

b. Tunica mediaThe tunica media is composed of smooth muscle, which can

stretch/expand to accommodate changes in blood pressure.Is this answer arguable?

VASCULAR ENDOTHELIUM Nutrients and O2 pass into tissues Wastes and CO2 pass from tissues

into blood Creates compounds that cause

vasodilation or vasoconstriction Creates growth factors that can

stimulate smooth muscle Forms a smooth lining of the blood

vessels that resists clot formation Creates compounds to promote clot

formation in injured areas

ATHEROSCLEROSIS

Lipids get into the vascular endothelium

White blood cells try to clear them away foam cells

WBCs and vascular endothelium release growth factors that promote plaque formation

Plaques block the arteries

LIPOPROTEINS

The more protein, the higher the density

The more lipid, the lower the density

LIPOPROTEINS

The more protein, the higher the density

The more lipid, the lower the density

i.e. protein is heavier than lipids

QUESTION

Tell whether the following statement is true or false.

LDL is considered to be “good” cholesterol.

ANSWER

FalseRationale: LDL (low-density lipoprotein,

which has more lipids and less protein) is the “bad” cholesterol. HDL (high-density lipoprotein) has more protein and less fat, and is considered “good” cholesterol.

LIPID TRANSPORT IN THE BODY

Dietary lipids absorbed as chylomicrons

Adipose and muscle cells take up lipids from chylomicrons

Chylomicron remnants are intermediate-density lipoproteins, IDL

LIPID TRANSPORT IN THE BODY (CONT.)

IDLs become low-density lipoproteins (“bad cholesterol”)

These can deliver fat to the liver and to other tissues

LDL receptors are necessary for the liver to take them up

Some LDLs are taken up by scavenger cells like macrophages

FATTY STREAKS AND ATHEROSCLEROTIC PLAQUES

FATTY STREAKS AND ATHEROSCLEROTIC PLAQUES

ATHEROSCLEROSIS

Atherosclerosis develops because scavenger cells encounter the fatty deposits in the artery lining and Try to destroy the fats by oxidizing them

º Oxidized fats injure the endotheliumº Clots form and release growth factorsº Smooth muscle grows over the fatty core

Try to remove the fats by eating them Become “foam cells” in the core of the plaque

LIPID TRANSPORT IN THE BODY

High-density lipoproteins (“good cholesterol”) are made in the liver

They go out to the peripheral tissues and pick up lipid

Then they carry it back to the liver

SCENARIO

A man has several genetic defects in his lipoprotein receptors…

His liver lacks LDL receptors

His muscle cells lack receptors for the apoproteins on chylomicrons

His scavenger cells have extra LDL receptors

Question:

Why might he develop atherosclerosis?

STABLE PLAQUES Have thick fibrous caps

Partially block vessels

Do not tend to form clots or emboli

UNSTABLE PLAQUES Have thin fibrous caps

Plaque can rupture and cause a clot to form

May completely block the artery

The clot may break free and become an embolus

QUESTION What immediate threat do unstable plaques

present?a. Clot formation will increase pressure in the

vessel.b. Plaque may lead to angina (chest pain).c. Clots may break loose and block blood

flow to key organs.d. All of the above constitute immediate

threats.

ANSWER c. Clots may break loose and block blood

flow to key organs.Rationale: If a clot breaks loose, becoming

an embolus, it may lodge in a blood vessel to the brain, heart, or lungs. When blood flow is significantly decreased or blocked altogether, the result is tissue death—in the examples here, stroke, heart attack, or pulmonary embolus. The other choices represent more long-term/chronic problems.

SCENARIOA woman complains of pain in her left leg. Her foot is cool and pale She reports that it is often red and warm

when she is sitting down The pain occurs when she is walking to

church on Sundays The skin on her left leg is shinier than on

her right legQuestion: What could have caused all this? How?

ANEURYSMS

Wall of artery weakens and stretches

Risk of rupture and hemorrhage

Risk of clot formation

AORTIC ARCH ANEURYSM

CAROTID ARTERY ANEURYSM

DISCUSSION

How would each of the following affect blood pressure?

Vasodilation Decreased stretching of baroreceptors Hypoxemia Inhibiting angiotensin-converting enzyme Beta blockers Alpha-2 agonists Calcium-channel blockers

Lower resistance lowers BP

Reflex raises BP

Calls for more blood flow raises BP

Blocks formation of Angiotesion II Lowers BPSlows HR Lowers BP

Decreases Sympathetic response Lowers BP

Decreases vascular resistance Lowers BP

VARICOSE VEINS

SCENARIO

A woman complains of pain in her left leg… Her foot is cool and pale She reports that it is often red and warm

when she is sitting down The pain occurs when she is walking to

church on Sundays The skin on her left leg is shinier than on

the right legQuestion: What could have caused all this? How?

ANEURYSMS

Wall of artery weakens and stretches

Risk of rupture and hemorrhage

Risk of clot formation