Chapter 2 Notes
Chapter 2 Notes AGRI 313
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This 6 page Class Notes was uploaded by Angela Notetaker on Monday February 15, 2016. The Class Notes belongs to AGRI 313 at Fort Hays State University taught by Dr. Keener in Fall 2016. Since its upload, it has received 23 views. For similar materials see Anatomy & Physiology of Domestic Animals in Agricultural & Resource Econ at Fort Hays State University.
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Date Created: 02/15/16
Body Water Properties and Functions Body Water Water constitutes approximately 60% of total body weight. ◦ Water is the most abundant constituent of the body fluids. Water provides lubrication necessary for: ◦ Minimizing friction associated with fluid flow. ◦ Cell movement ◦ Movement of body parts Physiochemical Properties of Solutions Simple diffusion Facilitated diffusion Active transport Simple Diffusion Refers to random movement of molecules, ions, and suspended colloid particles from an area of higher concentration to an area of lower concentration. Energy is not required Cell membranes are generally the barrier to diffusion. Facilitated Diffusion Diffusion occurs aided by a carrier for substances from an area of higher concentration to an area of lower concentration. Energy is not required. Protein channels provide structural pathways for water and water soluble substances. ◦ Exclusion of substances through the pores may be due to: ▪ Size ▪ Charge ▪ Protein channels specificity Active Transport Involves specific protein channels that act as carrier proteins for transport of substances in a direction opposite to their natural diffusion direction. Requires a carrier Requires energy Osmosis Process of diffusion of water through a semipermeable membrane from a solution of higher water concentration to a solution of lower water concentration. Semipermeable membrane-permeable to water but not solutes ◦ Comparing water concentration of solutions, the highest water concentration has the lowest solute concentration. Osmotic Pressure Pressure that would have to be applied to the compartment with the lowest water concentration to prevent net diffusion of water from the compartment with the highest water concentration ◦ In the body, osmosis is not prevented when imbalances exist. The number of particles in a solution determines its osmotic pressure ◦ The greater the number of particles, the higher the osmotic pressure (the lower the concentration of water) Water diffuses to the area of greatest osmotic pressure ◦ (lowest concentration of water) Effective Osmotic Pressure Selectively permeable membrane-allows for certain solutes (as well as water) to diffuse through them. ◦ The membranes of the body vary in their permeabilities and allow certain solutes (as well as water) to diffuse through them. Tone of a solution-established by those particles in solution for which the membrane is not permeable. Water diffuses to the greatest effective osmotic pressure Tone of a Solution vs Erythrocytes The tone of a solution that can be infused into the blood of animals is usually compared with the solution inside the red blood cells (erythrocytes). The solution of erythrocytes is in osmotic equilibrium with plasma (the fluid portion of blood). Intravenous Solution Classification Hypotonic Solution ◦ The infusing solution has a lower effective osmotic pressure than the erythrocyte solution. ▪ More solute particles are located within the erythrocyte than in the solution being infused. ▪ Less water or fluid located in the erythrocyte than in the solution being infused. Water diffuses into the RBC, causing it to expand and eventually lyse (burst). Water diffuses to the greatest effective osmotic pressure. Isotonic Solution ◦ The infusing solution has the same effective osmotic pressure as the solution within the erythrocyte. ▪ Water does not diffuse either direction involving the infusing solution or the erythrocyte. Hypertonic Solution ◦ The infusing solution has a higher effective osmotic pressure than the solution within the erythrocyte. ▪ More solute particles are located in the infusing solution than in the erythrocyte. ▪ More water located within the erythrocyte than in the infusing solution. ▪ Water diffuses out of the RBC into the infusing solution causing the RBC to crenate (shrink). ▪ Water diffuses to the greatest effective osmotic pressure. Erythrocyte Damage Hemolysis Crenation Hemoglobinemia Hemoglobinuria Hemolysis Refers to the rupture of erythrocytes with release of hemoglobin (red coloration). Crenation Refers to the water loss from an erythrocyte resulting a wrinkled appearance. Hemoglobinemia Refers to a red or port wine discoloration of plasma. Plasma is typically colorless to light yellow. Hemolysis of erythrocytes releases hemoglobin (red coloration). Hemoglobinuria Refers to a red discoloration of the urine resulting from the severe hemolysis of erythrocytes. Hemoglobin enters the kidney tubules and through overwhelming of the filtration process remains in the urine resulting in discolored urine. Total Body Water Is the sum of the body water that is contained in arbitrary divisions of its distribution between the intracellular and extracellular compartments. Total Body Water is variable and depends mostly on the amount of fat in the body. ◦ Increased body fat, means increased intracellular fat resulting in decreased intracellular water. Obese animals may have water equivalent to 45% of their body weight. ◦ Decreased body fat, decreased intracellular fat, increased intracellular water. Lean animals may have water equivalent to 70% of their body weight. ▪ The average animal has water equivalent to 60% of its body weight Fluid Compartments Intracellular fluid (40%) ◦ Approximately two-thirds of the body water is found within the cells Extracellular fluid (20%) ◦ All other fluid outside of the cells ▪ Interstitial fluid ▪ Intravascular fluid ▪ Transcellular fluid Interstitial Fluid Interstitial fluid ◦ Fluid outside of the capillaries immediately surrounding the cells ◦ Occupies the interstitial space along with intercellular substances (collagen, elastic fibers, fibroblasts, plasma cells, mast cells, and amorphous ground substance) ◦ Amorphous ground substance-hyaluronic acid-highly hydrated gel that holds tissue fluid in its interstices. Because of the gel form, fluid does not flow or accumulate in the lower portions of the body. Intravascular Fluid Liquid portion of blood known as plasma. ◦ Approximately 92% of the plasma volume is water. ◦ The remaining 8% of plasma volume is mostly protein. ▪ There also many ions and molecules in plasma. Transcellular Fluid Fluid found in body cavities. ▪ Usually minimal ◦ Includes: ▪ Fluid in the digestive tract Greatest amount found in ruminants ▪ Intraocular fluid ▪ Cerebrospinal fluid Water Balance Body water content remains relatively constant. Water turnover is the amount of water gained to balance the amount lost or excreted. Water Gain Water gain can be accomplished by ingestion or metabolic water. ◦ Metabolic water is derived from the energy production during oxidative phosphorylation in the mitochondria. ▪ More energy is required for metabolism of fat than protein or carbohydrate, thus resulting in increased water production from fat versus protein or carbohydrate. In domestic animals, metabolic water formation averages about 5% to 10% of daily water gain. Water Loss Water loss occurs due to insensible or sensible loss. ◦ Insensible loss is associated vapor losses from the skin and exhaled breath. ◦ Sensible losses are visible losses associated with urine, feces, and body excretions. Water Requirements Basal daily needs for water (to maintain water balance) are related to caloric expenditure. Basal metabolism conditions (resting animal, thermally neutral environment, fasting state). Caloric expenditure is related linearly to body surface area. Water Requirements Relative to Body Weight In emergency situations, body water is utilized from the Extracellular Fluid (interstitial, intravascular and transcellular fluid), which comprises 20% of the body weight. ◦ In comparison an 1100 lb. cow contains 220 lbs. of water in the extracellular fluid. ◦ A 110 lb. calf contains 22 lbs. of water in the extracellular fluid. ▪ The cow has considerably more reserve than the calf. ▪ Uncontrolled water loss such as diarrhea depletes the calf’s reserve much faster than the cow. Dehydration Condition that occurs when water losses exceed water gains. Immediate source of depletion in the body is the extracellular fluid, followed by a shift from the intracellular fluid to the extracellular fluid. 10% body water loss is severe Electrolytes are lost through the kidney in proportion to the amount of water loss. Fluid therapy requires adequate rehydration with electrolyte supplementation. Thirst Stimulus Thirst is the conscious desire for water. When water loss exceeds water gain: ◦ A thirst mechanism is stimulated which recognizes the need for water intake greater than that provided by food and metabolic water. ◦ The kidneys are stimulated to conserve water. Thirst Mechanism Thirst center is located in the hypothalamus of the brain. ◦ Thirst cells are stimulated by an increased osmoconcentration (loss of water and increased salt concentration). ▪ Osmoconcentration is a consequence of dehydration. ◦ Angiotensin II also stimulates thirst cells. ▪ Kidney hormone produced in response to decreased blood pressure which stimulates changes to increase blood pressure through salt retention, peripheral vasoconstriction, or water ingestion. Kidney Stimulation Thirst stimulates production of the kidney hormone Angiotensin II. ◦ This hormone is formed in response to low blood pressure. ◦ Angiotensin II stimulates salt retention, peripheral vasoconstriction, and water ingestion. Covered more thoroughly in Ch. 11 Adaptation to Water Lack Bos Indicus cattle have greater sweating capabilities than other breeds Camels can endure approximately 30% dehydration. ◦ They can store body heat during the day resulting in an increased body temperature, then dissipate the excess heat at night. Results in decreased water evaporation. ◦ They can rapidly ingest water (up to 25% of body weight) without detrimental effects. Adaptation to Water Lack Sheep can also endure up to 30% dehydration. ◦ They have wool which provides protection against solar heat gain ◦ Excrete dry feces and concentrate urine ◦ Have ability to pant, which provides evaporative heat loss Donkeys can also endure up to 30% dehydration. ◦ Have the ability to sweat, providing evaporative heat loss Both sheep and donkeys can rapidly ingest water (up to 25% of body weight) without detrimental effects.
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