Chapter 21: Body Fluids

Overview

Key Terms acidosis cation interstitial alkalosis dehydration intracellular anion edema kektoacidosis ascites effusion pH buffer extracellular polydipsia

Water and Its Functions Learning Outcomes 1. Compare intracellular and extracellular fluids. 2. List four types of extracellular fluids. 3. Name the systems that are involved in water balance. 4. Explain how thirst is regulated.

The Importance of Water Body fluid maintenance Thirst mechanism maintains volume Kidney activity regulates volume and composition. Hormones regulate fluid volume and electrolytes. Buffers, respiration, and kidney function regulate pH.

Fluid Compartments Intracellular fluid (ICF) Two-thirds to three-fourths of all body fluids Extracellular fluid (ECF) Interstitial fluid Blood plasma Lymph Fluid in special compartments

Figure 21-1 Main fluid compartments showing relative percentage by weight of body fluid. What are some avenues through which water is lost?

Water Balance Water gain from Beverages Food Cellular respiration Water loss from Kidneys Skin Lungs Intestinal tract

Sense of Thirst Control center for thirst Located in hypothalamus Regulates total fluid volume Excessive thirst—polydipsia

Figure 21-2 Daily gain and loss of water. In what way is the most water lost in a day? 10

Water and Its Functions ✓ Water and Its Functions Checkpoints 21-1 What are the two main compartments into which body fluids are grouped? 21-2 What are the four routes for water loss from the body? 21-3 Where is the control center for the sense of thirst located? 11

Electrolytes and Their Functions Learning Outcomes 5. Define electrolytes and describe some of their functions. 6. Describe the role of hormones in electrolyte balance.

Electrolytes and Their Functions Conduct electrical current in solution Positive ions (cations) Sodium Potassium Calcium Negative ions (anions) Phosphate Chloride

Figure 21-3 Distribution of some major ions in intracellular and extracellular fluids. What ions are highest in extracellular fluids? In intracellular fluids? 14

Electrolyte Balance Kidneys do majority of balancing Hormones involved Aldosterone (adrenal cortex) Antidiuretic hormone (ADH) (pituitary) Parathyroid hormone (parathyroid and thyroid glands) Calcitonin hormone (thyroid) Atrial natriuretic peptide (ANP) (from the heart)

Electrolytes and Their Functions ✓ Electrolytes and Their Functions Checkpoints 21-4 What is the main cation in extracellular fluid? In intracellular fluid? 21-5 What is the main anion in extracellular fluid? 21-6 What are some mechanisms for regulating electrolytes in body fluids? 16

Acid-Base Balance Learning Outcomes 7. Describe three methods for regulating the pH of body fluids. 8. Compare acidosis and alkalosis, including possible causes.

Acid–Base Balance pH scale measures hydrogen ion (H+) concentration Body fluids have normal pH of 7.35 to 7.45 Three-tenths of a point shift in either direction is fatal

Regulation of pH Buffer systems accept or release ions as needed Bicarbonate Phosphate Proteins Respiration provides short-term regulation Kidney function provides long-term regulation

Abnormal pH Acidosis pH less than 7.35 Depressed nervous system Alkalosis pH greater than 7.45 Excited nervous system Origins Respiratory—change in blood CO2 Metabolic—change in other acids

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✓ Acid-Base Balance Checkpoints 21-7 What are three mechanisms for maintaining the acid–base balance of body fluids? 21-8 What are the conditions that arise from abnormally low or high pH of body fluids? 22

Disorders of Body Fluids Learning Outcome 9. Describe three disorders involving body fluids.

Disorders of Body Fluids Edema Water intoxication Effusion Ascites Dehydration

Figure 21-4 Edema of the foot. 25

Figure 21-5 Simple test for dehydration. 26

Disorders of Body Fluids ✓ Disorders of Body Fluids Checkpoints 21-9 What is edema? 21-10 What is ascites? 27

Fluid Therapy Learning Outcome 10. Specify some fluids used in therapy.

Fluid Therapy Fluids administered intravenously Normal (0.9%) saline 5% dextrose in 0.45% saline 5% dextrose in water Ringer lactate solution Serum albumin 25% Nutritional solutions

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✓ Fluid Therapy Checkpoint 21-11 When might it be necessary to administer intravenous fluids? 31

Case Study Learning Outcome 11. Referring to the case, describe why elderly people are particularly susceptible to dehydration. 32

Word Anatomy Learning Outcome 12. Show how word parts are used to build words related to bodily fluids. 33

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