HBHD 13e Ch21

Copyright © 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 21
Body Fluids

Copyright © 2015 Wolters Kluwer • All Rights Reserved
Overview

Key Terms
acidosis cation interstitial
alkalosis dehydration intracellular
anion edema ketoacidosis
ascites effusion pH scale
extracellular polydipsia

Body Fluids
Learning Objectives
1. Compare intracellular and
extracellular fluids.
2. List four types of extracellular
fluids.
3. Define electrolytes, and
describe some of their functions.
4. Name four systems that are
involved in water balance.
5.Explain how thirst is regulated.
6.Describe the role of hormones in
electrolyte balance.

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

Disorders of Body Fluids
Learning Objective
9. Describe four disorders
involving body fluids.

Fluid Therapy
Learning Objective
10. Cite instances in which fluids are
administered therapeutically, and cite
four fluids that are used.

Case Study
Learning Objective
11. Referring to the opening case
study, explain the dangers of
overhydrating.

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

Body Fluids (cont.)
• Fluids make up over half of the body mass.
• Body fluid primarily composed of water, electrolytes,
nutrients, gases, wastes, and special substances.

Body Fluids (cont.)
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?

Body Fluids (cont.)
Water and Its Functions
•Water is important as:
– A solvent
– A transport medium
– A participant in metabolic reactions

Body Fluids (cont.)
Electrolytes and Their Functions
•Compounds that separate into positively and negatively
charged ions in solution
– Cations (positively charged)
– Anions (negatively charged)
•Major ions
– Cations
• Sodium
• Potassium
• Calcium
• Magnesium

Body Fluids (cont.)
Electrolytes and Their Functions (cont.)
•Major ions (cont.)
– Anions
• Bicarbonate
• Chloride
• Phosphate

Figure 21-2 Distribution of some major ions in intracellular
and extracellular fluids.
What ions are the most concentrated in extracellular fluids?
In intracellular fluids?

Body Fluids (cont.)
✓
Checkpoints
21-1 Where are intracellular fluids located? Extracellular
fluids?
21-2 What is interstitial fluid?
21-3 What are cations and anions?

Regulation of Body Fluids
• Negative feedback mechanisms maintain composition
and volume of body fluids.
• Constancy maintenance of body fluids:
– Thirst mechanism
– Kidney activity
– Regulation of body fluid pH

Regulation of Body Fluids (cont.)
Water Balance
•Average adult takes in about 2,300 mL of water daily
•Same volume of water lost through the:
– Kidneys
– Skin
– Lungs
– Intestinal tract

Control of Water Intake
•Thirst mechanism
– Mouth dryness
– Polydipsia
•Control center located in the brain’s hypothalamus

Figure 21-3 Daily gain and loss of water.
In what way is the most water lost in a day?

Control of Urine Output
•Kidneys
•Sodium’s role in water balance
•Hormones
– Aldosterone
– Antidiuretic hormone (ADH)
– Angiotensin II (ATII)
– Atrial natriuretic peptide (ANP)

Figure 21-4 Aldosterone.
How would the overconsumption of potassium-rich
foods like bananas alter aldosterone secretion?

✓
Checkpoints
21-4 What are four routes for water loss from the body?
21-5 What hormone from the adrenal cortex promotes
sodium reabsorption in the kidney?
21-6 What pituitary hormone increases water
reabsorption in the kidney?

Acid–Base Balance (cont.)
• pH scale measures hydrogen ion (H+
) concentration.
• Body fluids are slightly alkaline, 7.35 to 7.45.
Regulation of pH
• Carbonic acid lowers blood pH.
• Lungs exhale CO2
.
• Body systems act together to maintain pH balance.
– Buffer systems
– Respiration (short-term regulation)
– Kidney function (long-term regulation)

Figure 21-5 pH Regulation.
Which organ generates bicarbonate ions?

• Acidosis
– pH less than 7.35
– Depresses the nervous system
– Causes:
• Ketoacidosis
• Kidney failure
• Prolonged diarrhea
• Intense, long-term exercise
• Inadequate carbohydrate metabolism
 Uncontrolled diabetes mellitus
 Starvation
 Ingestion of a low-carbohydrate diet

• Alkalosis
– pH greater than 7.45
– Excites the nervous system
– Possible causes:
• Hyperventilation
• Ingestion of too much antacid
• Prolonged vomiting

✓
Checkpoints
21-7 What are three mechanisms for maintaining the
acid–base balance of body fluids?
21-8 What condition arises from abnormally
low pH of body fluids? From high pH of body fluids?

Disorders of Body Fluids (cont.)
• Edema
– Interference with venous return
– Kidney failure
– Lack of plasma protein
– Increased permeability of the capillary wall
– Blockage in the lymphatic system
• Hyponatremia (water intoxication)
• Effusion
– Ascites

Figure 21-6 Edema of the foot.

• Dehydration
− Vomiting
− Diarrhea
− Drainage from burns, wounds
− Excessive perspiration
− Inadequate fluid intake

Figure 21-7 Simple test for dehydration.

✓
Checkpoints
21-9 What is the term for accumulation of excess
interstitial fluid?
21-10 What term describes low blood sodium
concentration?
21-11What is the term for effusion of fluid into the
abdominal cavity?

Fluid Therapy (cont.)
• Fluids administered intravenously
– Isotonic solution
– Hypertonic solution
– Hypotonic solution
• Normal (0.9%) saline
• 5% dextrose in 0.45% saline (hypertonic)
• 5% dextrose in water (slightly hypotonic)
• Ringer lactate solution (electrolytes)
• Serum albumin 25% (hypertonic)
• Nutritional solutions

Fluid Therapy (cont.)
✓
Checkpoints
21-12 What is the percentage of sodium chloride in normal
saline?
21-13 What is another name for dextrose?

Case Study (cont.)
Exercise-Associated Hyponatremia (Overhydration)
Symptoms
•Edema
− In severe cases, cerebral edema may cause coma, death
− Weight gain due to fluid retention
•Hypotension (low blood pressure)
•Reduced blood sodium concentration
Treatment
•Sodium tablets
•Diuretic

Word Anatomy (cont.)

HBHD 13e Ch21

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HBHD 13e Ch21