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3.4 – The Circulatory System

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1 3.4 – The Circulatory System
Importance of Circulation (Internal Transport) carries oxygen and nutrients to the cells for cellular respiration carries wastes away from cells (with lymph and excretory system) carries chemical messages from endocrine organs to target tissues carries immune cells to infection sites distributes heat maintains levels of body fluids (with kidneys), pH the human heart beats about 70 times/minute non-stop from when you first draw breath until you die, pumping enough blood to fill 2 large ships km of blood vessels are never more than 2 cells away from the human body’s

2 Parts of the Circulatory System
Blood more than ½ of blood is plasma consisting of water, protein, nutrients, urea, mineral salts, vitamins, gases, and heat plasma proteins help maintain homeostasis globulins produce antibodies to defend against pathogens fibrinogens are important in blood clotting

3 rest of blood is composed of formed elements consisting of red blood cells, white blood cells, and platelets Red Blood Cells (Erythrocytes) primary function is transport of O2 and CO2 anucleate, biconcave disk provides greater surface area for gas exchange live for about 120 days  at least are produced each day in bone marrow, produced by nucleated stem cells each RBC contains haemoglobin molecules (haeme = iron-containing pigment, globin = protein structure) 4 Fe molecules attach to protein structure and bind to oxygen  oxyhaemoglobin complex gives blood it’s red colour  once oxygen is given up, the protein changes shape and appears bluish

4 White Blood Cells (Leucocytes)
much less numerous than RBC (1 in 700) nucleated, classified by shape of nucleus and appearance of granules in the cytoplasm granulocytes and agranulocytes are both produced in the bone marrow, but agranulocytes are modified in the lymph tissue

5 Platelets also anucleate and produced in nucleated stem cells in the bone marrow (small fragments of cytoplasm break off from a megakaryocyte) irregularly-shaped platelets move through the smooth blood vessels until they strike a sharp edge (i.e. a tear), where they initiate blood-clotting reactions

6 The Heart made up of cardiac muscle, nerve, and connective tissue
a fluid-filled membrane called the pericardium surrounds the heart  fluid bathes the heart, preventing friction between its outer wall and the covering membrane the heart consists of two separate pumps separated by the septum pumping action is synchronized  the right side collects deoxygenated blood from the body tissues and pumps it to the lungs for gas exchange (pulmonary circuit)  the left side receives oxygenated blood from the lungs and pumps it to the body cells (systemic circuit)

7 Blood Vessels Arteries arteries carry blood away from the heart
they have thick walls with distinct layers outer and inner connective tissue middle muscle and elastic connective tissue thick and elastic to withstand pressure generated by pulses of blood as they are pumped out of the heart arteries branch into arterioles which have a middle layer of smooth muscle

8 Capillaries composed of a single layer of cells, capillaries are the site of fluid and gas exchange between blood and body cells most are mm long and less than mm in diameter (RBC must pass through in single file)(Fig. 3, P. 252) capillary beds are easily damaged by high BP or impact (bruising occurs as blood enters space between tissue) O2 and CO2 diffuse across capillary walls proteins cross by active transport (exocytosis and endocytosis) water-soluble ions and vitamins pass through spaces between endothelial cells

9 Veins deoxygenated blood collects in small veins (venules) as capillaries merge

10 BP in venules is reduced to 15-20 mm Hg
thinner walls of veins contain smooth muscle that rhythmically massage blood back to the heart

11 Disorders and Diseases of the Circulatory System
cardiovascular disease includes hypertension (sustained high blood pressure), arteriosclerosis, atherosclerosis, heart attack (destruction of the heart muscle), and stroke (interrupted blood flow to the brain) factors affecting health of the heart: high blood cholesterol smoking diabetes mellitus hypertension sedentary lifestyle rapid weight gain or loss congenital factors Hypertension increased resistance to blood flow results in weakening and rupture of blood vessels increased connective tissue to support weak vessels makes them less elastic which further increases blood pressure sometimes hereditary , but usually diet-related (i.e. salt ) 11

12 Coronary Artery Disease
Artherosclerosis lipid droplets join together and form blockages in arteries calcium and other minerals form on top of the fat to form a fibrous net of plaque (artherosclerosis, the most common type of arteriosclerosis = “artery disease”) narrowing the artery diameter increases blood pressure blood clots form around deposits inadequate blood supply to the heart results in diseases that kills more Canadians than any other

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