Health and Med Science: Circulatory System

Circulatory system

• Consists of heart, blood vessels, and blood

• Transports O2 and nutrients to body cells, and CO2 and metabolic materials away from body cells

Heart

• Muscular, hollow organ (“pump” of the body)

• Size:  closed fist 

• Location: in mediastinal cavity, between lungs, behind sternum, above diaphragm

Layers of the heart

Endocardium, myocardium, pericardium

Endocardium

smooth layer of cells lining the inside of the heart and blood vessels;  allows for smooth flow of blood.

Myocardium

thickest layer; muscular middle layer

Pericardium

• double-layered membrane (sac); covers outside of the heart

  • Pericardial fluid: lubricating fluid between 2 layers to prevent friction and damage to membranes as heart beats and contracts

Septum

•  muscular wall that separates the heart into right and left side; prevents blood from moving between right and left sides of heart

  • Interatrial septum: upper part of septum; between atria

  • Interventricular septum:  lower part of septum; between ventricles

Divisions of heart

Right atrium, right ventricle, left atrium, left ventricle

Right atrium

receives blood as it returns from body cells

Right ventricle

receives blood from right atrium and pumps blood into pulmonary artery (carries blood to lungs for O2)

Left atrium

receives oxygenated blood from lungs

Left ventricle

receives blood from left atrium and pumps blood into aorta (transports blood to body cells)

Valves

keep blood flowing in right direction

• Tricuspid valve, Pulmonary valve, Mitral valve (bicuspid), Aortic valve

Tricuspid valve

between right atrium and right ventricle; closes when right ventricle contracts, allowing blood to flow to lungs and prevent blood from flowing back to right atrium

Pulmonary valve

between right ventricle and pulmonary artery; closes when right ventricle finished contracting, preventing blood from flowing back into right ventricle

Mitral valve (bicuspid)

between left atrium and left ventricle; closes when left ventricle contracting, allowing blood to flow into aorta and prevents from flowing back into left atrium

Aortic valve

between left ventricle and aorta; closes when left ventricle finished contracting, allowing blood to flow into aorta and prevent blood from flowing back into left ventricle

Diastole

brief period of rest

Systole

period of ventricular contraction.

• comes after diastole

Cardiac Cycle

atria contract and push blood into ventricles → atria relax (blood from body returns and enters right atrium; blood returns from lungs and enters the left atrium) → as atria fill, systole begins (ventricles contract) → right ventricle pushes blood to pulmonary artery to lungs for O2; left ventricle pushes blood to aorta and out to body

Right side of heart low in O2 and high in CO2 → goes to lung; CO2 released to lungs, O2 taken into blood → oxygenated blood carried to left side of heart by pulmonary veins → left side of heart high in O2 and low in CO2 → out to body

Sinoatrial (SA) node

group of nerve cells located in right atrium (“pacemaker”); sends out electrical impulse, which spreads out over the muscles in atria; atrial muscles contract and push blood into ventricles

Atrioventricular (AV) node

group of nerve cells located between atria and ventricles; sends electrical impulse thru bundle of His

Bundle of His

nerve fibers in septum; divides into right and left bundle branch (carries impulse down thru ventricles)

Purkinje fibers

bundle branches subdivide; network of nerve fibers throughout ventricles → ventricles contract

Electrical impulse occurs…

every 0.8 seconds

Arrhythmia

• Arrhythmia:  abnormal heart rhythms and can be mild to life-threatening; occurs when something interferes with normal electrical conduction pattern of heart

  • Cardiac monitors and EKG used to diagnose arrhythmias

  • Tx depends on type and severity of arrhythmia; defibrillators tx life-threatening

Arteries

carry blood away from heart; more muscular and elastic because they receive blood as it is pumped from heart

Aorta

largest artery; receives blood from left ventricle of heart; immediately begins branching into smaller arteries

Arterioles

smallest branches of arteries; join with capillaries

Capillaries

connect arterioles with venules (smallest veins); thin walls containing only one layer of cells; thin walls allow O2 and CO2 and metabolic products from cells to enter capillaries

Veins

• blood vessels that carry blood back to heart; venules join together and get bigger to form

• thinner and less muscular than arteries

• most have valves (keep blood from flowing backwards)

2 largest veins

Superior vena cava and Inferior vena cava

Superior vena cava

brings the blood from the upper part of the body

Inferior vena cava

brings blood from lower part of the body

Both vena cavae drain into…

right atrium

Plasma

90% water, with many dissolved substances (fibrinogen and prothrombin – necessary for clotting; nutrients like vitamins, carbohydrates, proteins; mineral salts or electrolytes like potassium, calcium, sodium; gases like CO2 and O2; metabolic and waste products; hormones, enzymes

Erythrocytes

red blood cells (RBCs); produced in red bone marrow (1 million/min); live approx. 120 days; broken down in liver/spleen; 1 drop of blood = 4.5-5.5 million or 25 trillion in body; mature form- lacks a nucleus and shaped like a disc with a thinner center

Hemoglobin

contained in RBCs; complex protein composed of protein molecule globin and iron compound heme; carries both O2 and CO2; O2 gives red color; with a lot of O2 = bright red; with less O2 and more CO2 = much darker red with bluish

Leukocytes

white blood cells (WBCs); formed in bone marrow and lymph tissue; live about 3-9 days; normal count 5,000 – 10,000 per drop of blood; pass thru capillary walls and enter body tissue; MAIN FUNCTION = fight infection; phagocytosis = engulf, ingest and destroy germs

Neutrophils

phagocytize by secreting enzyme called lysozyme

Eosinophils

remove and defend from allergic reactions by producing antihistamines

Basophils

inflammatory response; produce histamine (a vasodilator) and heparin (anticoagulant)

Monocytes

phagocytize bacteria and foreign materials

Lymphocytes

provide immunity by developing antibodies; protects against cancer cells

Thrombocytes

platelets; lack a nuclei and vary in shape size; formed in bone marrow; live 5-9 days; normal count is 250,000 – 400,000 in a drop of blood;  important for clotting process

Anemia

• Inadequate number of RBCs, hemoglobin, or both

• Sx: pallor, fatigue, dyspnea, rapid heart rate

• Cause:  hemorrhage (acute blood-loss anemia) Blood transfusions tx this typy

  • Iron deficiency anemia:  inadequate amount of iron to form hemoglobin in RBCs; tx: iron supplements and increased iron intake in diet (green leafy vegetables and others)

Aplastic anemia

• injury to or destruction of bone marrow – leads to poor or no formation of RBCs

  • Causes:  chemo, radiation, toxic chemicals, viruses

  • Tx:  eliminate cause, blood transfusion, bone marrow transplant; unless damage reversed, fatal

Pernicious anemia

• formation of abnormally large and inadequate number of RBCs

  • Cause:  lack of intrinsic factor (usually present in stomach) that results in inadequate absorption of Vit B12

  • Tx:  Vitamin B12 injections

Sickle cell anemia

• chronic, inherited;  occurs primarily in African Americans

  • Tx:  transfusion of packed cells and supportive therapy during crisis

  • Genetic counseling can lead to prevention if carriers don’t have children

Aneurysm

• Ballooning out of (saclike formation) artery wall

• Cause:  disease, congenital defect and injury can weaken arterial wall

• Sx:  some pain and pressure, some none

• Common sites:  cerebral, aortal, abdominal arteries

• If rupture, hemorrhage = death

• Tx:  surgical removal of damaged area of blood vessel and replace with plastic graft or other vessel

Arteriosclerosis

• Hardening or thickening of arterial walls, resulting in loss of elasticity and contractility

• Causes: aging

• Sx: high blood pressure, can lead to aneurysm or cerebral hemorrhage

• Fatty plaques (cholesterol) are deposited on the walls of the arteries; narrows the arterial opening → reduces or eliminates blood flow 

• Emboli: when plaqes break loose and circulate thru blood stream

• Prevention:  low-cholesterol diet, meds to lower cholesterol, exercise

• Tx:  angioplasty (removes or compresses deposits), stent, bypass surgery

Congestive heart failure (CHF)

• Heart muscles do not beat adequately to supply the blood needs of the body

• Sx: edema; dyspnea; pallor or cyanosis; distention of the neck veins; a weak, rapid pulse; cough accompanied by pink, frothy sputum

• Tx: cardiac drugs, diuretics, elastic support hose, O2, bedrest, and /or low-sodium diet

Embolus

• Foreign substance circulating in bloodstream; can be air, blood clot, bacterial clumps, a fat globule, or others

• Can cause a blockage

Hemophilia

• Inherited; almost exclusively in males, but carried by females

• Blood is unable to clot b/c of lack of plasma protein required for clotting

• Tx:  transfusing whole blood (plasma); administer missing protein factor

Hypertension

• High blood pressure

• Systolic pressure greater than 140 and diastolic pressure greater than 90 mm of mercury

• Risk factors: family hx; race (higher in African Americans); obesity; stress; smoking; aging (higher in postmenopausal women); diet hig in saturated fat

• No cure; Tx: controlled with antihypertensive drugs, diuretics, limited stress, avoidance ob tobacco, and/or low-sodium or low-fat diet

• If untreated – can cause permanent heart, blood vessels, kidneys damage

Leukemia

• Malignant disease of bone marrow or lymph tissue; causes high number of immature WBCs

• Sx:  fever, pallor, swelling of lymphoid tissues, fatigue, anemia, bleeding gums, excessive bruising, joint pain

• Tx:  vary with type of leukemia; chemo, radiation, bone marrow transplant

Myocardial Infarction

• Heart attack; when coronary artery  is blocked and cuts off supply of blood to heart

• Infarct: affected heart tissue dies

• Sx:  severe crushing pain that radiates to arm, neck, jaw; pressure in chest; perspiration and cold, clammy skin; dyspnea; change in blood pressure

• If heart stops, CPR

• Tx:  immediate tx with thrombolytic (clot busting), may open blood vessel and restore blood flow to heart – must be used in first several hours, but not if bleeding  presnet; complete bed rest, pain meds, vasodilators, O2, anticoagulants, control arrhythmias; long term – control blood pressure, diet low in cholesterol and saturated fat; avoid tobacco and stress, regular exercise and weight control

Phlebitis

• Inflammation of vein, frequently in leg

• Thrombophlebitis: thrombus (clot) forms on inflammation

• Sx:  pain, edema, redness, and discoloration of site

• Tx:  anticoagulants, pain meds, elevation fo affected area, antiembolism or support hose, surgery to remove clot

Varicose veins

• Dilated, swollen veins that have lost elasticity and cause stasis (decreased blood flow)

• Occur in legs and result from pregnancy, prolonged sitting or standing, hereditary factors

• Tx:  exercise, antiembolism or support hose, avoidance of prolonged sitting or standing, and tight-fitting  or restrictive clothing; surgery