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Functions of Cardiovascular system

Functions of Cardiovascular system. system circulates blood throughout body transports energy substrates (glucose, FA, ect.), electrolytes and hormones to tissues removes waste products lactate, CO 2 & H 2 O thermoregulation. Heart. heart rate mass: average 1.0% untrained horse 0.94%

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Functions of Cardiovascular system

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  1. Functions of Cardiovascular system • system circulates blood throughout body • transports energy substrates (glucose, FA, ect.), electrolytes and hormones to tissues • removes waste products • lactate, CO2 & H2O • thermoregulation

  2. Heart • heart rate mass: • average 1.0% • untrained horse 0.94% • trained 1.1% • greyhound • heart size of a clenched fist • located in the chest • weighs about 1% of its BW

  3. Heart • located in thoracic cavity • approx. 9-10 lbs (1% of BW) • split into left and right halves • both contain an atria and a ventricle • left side circulates blood to systemic system • right side circulates blood to the pulmonary system • systole - contraction • diastole - relaxation

  4. aorta has elastic walls • pulse • expand during systole • recoil during diastole • arteries/arterioles have muscular walls allowing for vasoconstriction and vasodilation • blood pressure increases when the walls of the arteries constrict

  5. Capillaries • Constructed of permeable walls • sight of gas, nutrient and waste product exchange • pulmonary capillaries discard CO2 and extract O2 from the alveoli of the lungs • capillaries are very small in diameter • RBC flow through single file (blood is sluggish if the PCV is high) • conditioning (training) can increase capillary density 50% • provides more efficient O2 delivery

  6. Venous System • venules and veins have lower blood pressure than arteries • horse legs have valves to provide unidirectional blood flow in veins • venous flow depends on muscle contractions • activity provides better venous blood movement • inactive - blood pools in extremities • “stocking-up” • accumulation of fluid in legs

  7. Blood • 10% of horse BW of about 40 liters at rest • pulmonary circulation 20% • heart, arteries and arterioles 15% • venules and veins 60% • blood is comprised of plasma and cells • plasma: • 55% of the total blood volume • 91% water and 9% solids (proteins) • albumin, globulin and fibrinogen

  8. Blood Cell Composition • red blood cells (RBC) - erythrocytes - contain hemoglobin • manufactured from bone marrow • life span of 100-120 days • white blood cells (WBC) - leukocytes - fight infection • manufactured in the spleen • renewed every 10 days • 5 types • neutrophils (50-60%), eosinophils (2-5%), basophils (<1%), monocytes (5-6%), lymphocytes (30-40%) • platelets - thrombocytes - clot blood • life span of 5-9 days

  9. Blood Analysis • blood scan: 5 minutes • for major changes from normal (PCV, total protein, hemoglobin and estimate white blood cell count) • full blood count: 30 minutes • main count of WBC’s to detect infection, stress, allergies, ect. • blood profile: 24 hours • detailed RBC count, individual WBC counts, enzymes, electrolytes, ect. • Plasma - fluid spun from unclotted blood • serum - blood is allowed to clot and fluid is spun from the clot (contains no fibrinogen)

  10. Spleen • About 1% of BW • splenic contraction • 1/3 to 1/2 RBC stored in spleen at rest • hematocrit or packed cell volume (PCV) • rest 35-45% • maximum 60-65% • hemoglobin content of extra RBC in the blood acts as a pH buffer, enabling horses to tolerate extremely high blood lactate concentrations

  11. Function During Exercise • Heart rate - bpm • resting HR 25-45 bpm • maximal HR 240 bpm • desirable cardiovascular features • large, muscular heart • low resting HR • high maximal HR

  12. HR: 20-110 • not very predictable • intensity of work • 120 (low),160 (moderate), 200 (intense) • steady state 2-3 minutes • regulated by sympathetic nervous activity and/or hormones • steady state constant during sub-maximal work • continual increase in HR with intense exercise (warm-up) • monitor HR - indication of any problems

  13. Fatigue • 170 bpm 24 min • 205 bpm 4 min • cardiovascular drift

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