Module 9 Section 1

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Module 9:

Section 1:

 

• Blood
  • plasma
  • erythrocytes
  • leukocytes
  • platelets
• Blood vessels
  • arteries
    • arterioles
    • aorta
    • carotid
    • subclavian
    • organ
    • iliac
  • veins
    • venules
    • vena cava
  • capillaries
• The heart
  • right side
    • vena cava
    • right atrium
    • right ventrical
    • tricuspid valve
    • pulmonic valve
    • pulmonary arteries
  • left side
    • pulmonary veins
    • left atrium
    • left ventrical
    • mitral valve
    • aortic valve
    • aorta
  • coronary arteries
• Physiology
  • systole
  • diastole
  • pulse rate
  • sympathetic / parasympathetic
  • bleeding
    • vessel constriction
    • coagulation
    • platelets
• Cardiovascular diseases
  • hypertension
    • common medications
  • carotid artery disease
    • amaurosis fugax
    • ophthalmodynamometry
  • arteriosclerosis and atherosclerosis
    • cholesterol
    • common cholesterol reducing drugs
  • endocarditis
  • mitral valve prolapse

   

Most cells in the body come into contact with blood, through which they receive nutrients, oxygen, and the materials to fight infection. Waste matter from the cells is carried away by the blood.  It is interesting that a good portion of the eye does not have a direct blood supply.  The cornea and the lens receive nutrients from the aqueous humor.  The cornea receives most of its oxygen from direct contact with air.   Blood Blood is made up of plasma and cells. Plasma is more than 90% water and is the transport medium of the blood.  Plasma also contains glucose, fats, proteins, and electrolytes (sodium, calcium, potassium, and magnesium).  There are three types of cells which are transported by the plasma. Erythrocytes (red blood cells) carry oxygen via hemoglobin to the tissues and carry away the carbon dioxide waste product. Leukocytes (white blood cells) are specialized cells which fight infection. Platelets are cells which clump together to plug a hole in a damaged blood vessel to stop bleeding.

Blood vessels Blood is transported to tissues by muscular tubes (blood vessels) called veins and arteries.  Arteries carry oxygen rich blood from the lungs and heart to the tissues.  Veins carry blood containing carbon dioxide and waste products away from the cells, back to the heart and lungs.  Veins branch into smaller vessels called venules. Arteries branch into arterioles.  Cells are served by the smallest branches of blood vessels called capillaries. Veins from the upper half of the body drain into the superior vena cava.  Blood from the lower half of the body drains into the inferior vena cava. The aorta carries blood from the heart to the body. The aorta branches into the: right common carotid — serves the brain and the right eye. left common carotid — serves the brain and the left eye. right and left subclavian arteries — serve the arms. organ branches — serve lungs, kidneys, intestines, and other organs. iliac arteries — serve the lower body.

 

The Heart The heart is really two pumps in one.
The right side pump The right side of the heart receives blood from the tissues of the body and pumps it to the lungs where carbon dioxide is released and oxygen is taken on. The blood arrives from the superior and inferior vena cava veins and collects in the right atrium. From the right atrium blood is pumped through the one-way tricuspid valve into the right ventricle. The right ventricle pumps blood through the pulmonic valve into the pulmonary arteries and onward to the lungs.
The left side pump The pump that is the left side of the heart receives oxygenated blood from the lungs via the pulmonary veins into the left atrium.  The left atrium collects the blood and then pumps it through the mitral valve into the left ventricle.  From the left ventricle blood is pumped through the aortic valve into the aorta and onward to the tissues of the body.
The heart muscle itself is fed by the coronary arteries which branch off of the aorta as it leaves the heart.  When these arteries are severely narrowed or blocked, a heart attack results.

 

Physiology Blood is pumped through the blood vessels when the ventricles contract. The atria are holding tanks. When the ventricles relax, blood refills the ventricles from the atria and the ventricles are loaded for another contraction. Contraction is termed systole.  This is the high point of the blood pressure within the vessels, and the systolic blood pressure is the top number of the blood pressure reading.  Relaxation is termed diastole.  This is the low point of the blood pressure, and diastolic pressure is the bottom number of the blood pressure reading.  An average blood pressure reading in the normal range is around 120/80.  A pressure reading of 140/90 is considered to be borderline high. The average resting heart rate (pulse rate) is about 70 per minute.  Heart rate is controlled by the autonomic nervous system, meaning it is under automatic control and we don’t have to think about it.  Sympathetic nerve impulses make the heart beat faster (e.g., fright).   Parasympathetic nerve impulses slow the heart rate. Bleeding occurs when the integrity of a blood vessel is compromised by disease or injury. There is a threefold bodily response to bleeding: Blood vessel constriction — the vessel walls constrict to narrow the outlet. We aid this process by putting pressure on a bleeding vessel to stop the bleeding. Blood clotting (coagulation) — a chemical reaction occurs to thicken the blood.  Coumadin (warfarin) is a common medication that acts to prevent clotting in patients who have artificial heart valves or who are at risk for stroke.  These patients will need a longer application of pressure to stop bleeding. Platelets — when a blood vessel is injured, platelets stick to the injury site to plug up the leak.

 

Common Cardiovascular diseases Hypertension High blood pressure is present in one in six adult Americans and is more common in blacks than in whites.  There is no known cause for 90 percent of the cases and the disease is without symptoms.  If left untreated , there is increased risk of heart attack, stroke, and kidney failure.  The disease can affect the eyes, causing retinal damage in the form of vessel narrowing and hemorrhages.

Above:  the posterior pole of a 36 year old white female.  Notice the small hemorrhages in the retina surrounding the macula.  This lady was experiencing spikes of high blood pressure.  She was a heavy smoker on birth control pills, a bad combination.  She stopped smoking and discontinued the birth control pills.  The hemorrhages in her posterior pole subsequently disappeared.

Hypertension is commonly treated with medications.  It is helpful for you,  as a history-taker,  to be familiar with the names of common blood pressure medications,  which are grouped in the following categories: All hypertensive drugs are not listed,  just the more common ones.  For more information,  search "hypertension". Diuretics cause the body to excrete water and salt Diuril (chorothiazide) Esidrix (hydrochlorothiazide, HCTZ) HydroDiuril (hydrochlorothiazide, HCTZ) Lasix (furosemide) Aldactone (spironolactone) Triamterene (generic) ACE inhibitors reduce the chemical that causes arteries to constrict Capoten (captopril) Vasotec (enalapril) Accupril (quinipril) Lotensin (benazepril) Prinivil (lisinopril) Zestril (lisinopril) Beta-blockers block the effects of adrenaline, decreasing contractions, and they widen blood vessels Atenolol (generic) Betapace (sotalol) Corgard (nadolol) Inderal (propranolol) Inderide (propranolol, HCTZ) Lopressor (metoprolol) Tenormin (atenolol) Toprol (metoprolol) Ziac (bisoprolol and HCTZ) Vasodilators expand blood vessels Apresoline (hydralazine) Minipress (prazosin) Catapres (clonidine) Calcium channel blockers decrease contractions and widen vessels Cardizem (diltiazem) Dilacor  (diltiazem) Norvasc (amlodipine) Calan (verapamil) Procardia (nifedipine) Adalat (nifedipine) Plendil (felodipine)   Carotid artery disease The left and right carotid arteries travel up the neck and supply the brain and the eyes. Restriction or blockage of these arteries may cause a stroke or cerebral atrophy.  Plaque may break off from carotid walls, travel to the eye, and cause permanent vision loss from a central retinal artery occlusion. Patients with carotid artery insufficiency may have 2-15 minute unilateral episodes of visual loss termed amaurosis fugax ("fleeting darkness"). Bruits (sounds) detected (using a stethoscope) from a carotid artery is a diagnostic sign.  Ophthalmodynamometry may be performed to measure a possible pressure difference between the two carotid arteries.   Arteriosclerosis and Atherosclerosis Arteriosclerosis is a thickening and hardening of the artery walls.  It is usually preceded by atherosclerosis, which is a buildup of fatty tissue on the artery walls.  It is associated with high cholesterol levels and is made worse by high blood pressure and smoking.  This buildup can completely obstruct the artery or narrow the artery enough to be in danger of blocking from a clot.  The result can be a heart attack, a stroke, or an artery occlusion in the eye. Some common cholesterol reducing drugs are: Lescol (fluvastatin) Lipitor (atorvastatin) Mevacor (lovastatin) Pravachol (pravastatin) Questran (cholestyramine) Tricor (fenofibrate) Zocor (simvastatin)   Endocarditis Endocarditis may be a staph or strep bacterial infection of the lining or valves of the heart.  It may be secondary to infections of the teeth, tonsils, or sinuses.  Endocarditis can cause heart failure and stroke, and is treated with systemic antibiotics.  It may cause conjunctival and retinal hemorrhages (Roth’s spot).   Mitral Valve Prolapse MVP occurs when part of the mitral valve stretches into the atrium and does not completely block the flow of blood back into the atrium upon contraction of the ventricle.  About 5% of the population has this disorder which causes a heart murmur and is associated with abnormal platelet function.  The abnormal formations of platelets can block circulation to other parts of the body, including the eyes.

 

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