chapter 18 disorders of blood flow and blood pressure essentials of pathophysiology
TRANSCRIPT
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