Functions of Cardiovascular system

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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

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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

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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

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• 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

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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

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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

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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

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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 (
  (30-40)
• platelets - thrombocytes - clot blood
• life span of 5-9 days

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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 WBCs 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)

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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

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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

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• 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

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