BIOL 1030 – TOPIC 20 LECTURE NOTESTopic 20: Circulatory System (Ch. 42)Ι. circulation required for all animals that are more than a few cells thick so that cells can get oxygen and nutrients and get rid of wastesΙΙ. two main types of circulatory systems, open and closedA. open systems1. no distinction between circulating fluid and extracellular fluid of body (lymph)2. hemolymph is the circulating fluid3. less efficient for transport (little pressure, slower)4. may still have heart(s) for pumping and some vessels5. examples: arthropods, mollusksB. closed systems1. circulating fluid (blood) distinct from lymph2. at least one heart always present3. blood vessels – tubular network for blood flow from heart of body and back• arteries carry blood away from heart• veins return blood to heart• capillaries between arteries and veins are the thinnest vessel and allow exchanges with body tissues4. lymph system - when blood reaches capillaries, liquid seeps out of blood, most is mopped up, but much remains behind and needs to be mopped up or an edema (swelling) will form, lymph vessels return liquid to bloodΙΙΙ. vertebrate circulatory systems functionsA. transportation of gasses, nutrients, wastesB. regulation of temperatureC. transportation of hormonesD. protection (immune defense; blood clotting)Ις. blood plasmaA. metabolites, wastes and hormones including carbon dioxideB. ions - mostly sodium, chloride, and bicarbonate, lower total ion concentration than sea waterC. proteins - albumin, globulins (carry lipids and steroid hormones and fibrinogen) serum = fluid after fibrinogen clots out1 of 3BIOL 1030 – TOPIC 20 LECTURE NOTESD. formed elements – blood cellsς. blood cellsA. erythrocytes - red blood cells1. 5 million/cm32. 45% of blood (hematocrit)3. mammals - anucleate, donut shaped cell that carries hemoglobin4. live 120 days before replacement in humans5. formed in bone marrowB. leukocytes - white blood cells1. 1% of cells in blood2. larger, nucleated, can migrate out of capillaries3. no hemoglobin4. granular leukocyte - neutrophils (most common), eosinophils, and basophils5. nongranular leukocytes - monocytes and lymphocytes (T and B cells involved in immune response)6. neutrophils accumulate at injury and then joined by monocytes that change into macrophages7. phagocytosis by neutrophils and macrophages eliminate disease-causing organismsC. platelets1. megakaryocytes in marrow break off bits of their cytoplasm to form platelets, which are actually cell fragments, not cells2. accumulate at wound and form a plug by sticking to each other and tissues3. plug reinforced by fibrin (formed by fibrinogen in complex chain of events)ςΙ. blood vesselsA. structure - endothelium then elastic fibers then smooth muscle layer then connective tissue (except capillaries)B. arteries1. large ones - very elastic to absorb force of heart2. small ones (arterioles) - more muscular - to control blood flow (vasoconstriction and vasodilation)C. capillaries1. only endothelial lining (one-cell thick)2. about one red blood cell wide3. all exchange occurs here4. little blood pressure after exit2 of 3BIOL 1030 – TOPIC 20 LECTURE NOTESD. veins and venules (smaller veins, just after capillaries)1. less muscular than arteries2. blood pressure greatly reduced in venous system - possibility for retrograde (back) flow3. valves - present in ascending veins to halt retrograde flow4. descending veins - no valves, gravity helps5. skeletal muscles help move blood - contract leg muscles to avoid fainting, which is typically caused by blood pooling in the legs6. varicose veins - veins expanded too much and no longer workςΙΙ. the mammal heartA. 4 chambersB. right side - atrium receives blood from body, pumps to ventricle, which pumps to lungsC. left side - atrium receives blood from lungs, pumps to ventricle, which pumps to bodyD. atria both pump at the same time, then after about 100 ms delay both ventricles pump; both sides must pump the same volume, but the left pumps at greater pressure because it is going through greater resistanceE. valves prevent backflowF. sinoatrial node (SA node) - pacemaker - starts impulse at atria and sends impulse to atrioventricular (AV) nodeG. AV node shunts impulse to the apex (bottom) of the heart through Purkinje fibers - modified cardiac muscle cells that look like neurons (unique to mammals)H. shunted impulse squeezes the heart from the bottom up - more efficient just like squeezing the toothpaste from the bottom of the tube is more efficientI. heart rate increases under exercise to get enough oxygen to muscles3 of
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