LO 19

Question 1

Describe average body water

Answer 1

1. References to “average” body water volume based on a healthy, nonobese, 70-kg male
2. Water is 60% of body weight in males; 50% in females
3. Volume averages 40 L in a 70-kg male (154 pounds)

Question 2

Why does total body water vary?

Answer 2

1. Total body weight of individual- Large variation
2. Fat content of body - The more fat the less water (adipose tissue is low in water content)
3. Gender - Female body has about 10% less water than male body; Related to reproduction
4. Age - In a newborn infant, water may account for 80% of total body weight; In older adults, water per pound of weight decreases (muscle tissue —high in water—replaced by fat, which is lower in water)
5. The percentage of body water decreases rapidly during the first 10 years of life.

Question 3

List the fluid from least to most in the body: plasma, interstitial, intracellular

Answer 3

1. Plasma (approx 3L)
2. Interstitial (approx 12L)
3. Intracellular (25L)

Question 4

What percent of total water content are extracellular fluid and intracellular fluid

Answer 4

1. Extracellular - 34%
2. Intracellular - 66%

Question 5

Describe extracellular fluid (ECF)

Answer 5

1. Outside of cells
2. Called internal environment of body
3. Surrounds cells and transports substances to and from
4. 3 types - Plasma (Liquid part of whole blood); Interstitial fluid (Surrounds the cells); Transcellular fluid (Lymph, joint fluids, cerebrospinal fluids, eye humors)

Question 6

Describe intracellular fluid (ICF)

Answer 6

1. Inside cells
2. Largest fluid compartment
3. The cytosol within cells
4. Gives structure and support to cell organelles
5. Serves as solvent to facilitate intracellular chemical reactions for chemical metabolism

Question 7

Describe the mechanisms that maintain fluid balance

Answer 7

1. Sources of fluid intake - Liquids we drink, water in food, and metabolic water (produced by cells as byproduct)
2. Sources of fluid output - Water vapor in breath, sweating, urine, and water in feces, tear loss
3. Three main factors affect plasma, IF, and ICF volumes: Regulating fluid output; Regulating fluid intake; Exchanging fluid among compartments and around the body

Question 8

What happens if the water content of the body changes?

Answer 8

1. Cellular activities are jeopardized
2. We must maintain a normal volume and composition in the extracellular fluid (ECF) and the intracellular fluid (ICF) via homeostasis

Question 9

What are the sources of fluid intake?

Answer 9

1. Liquids we drink (60%)
2. Water in foods we eat (30%)
3. Water from breakdown of foods (10%)
4. Average adult needs about 2,500 ml (10 cups) of fluid per day!

Question 10

How does the body regulate fluid intake?

Answer 10

When fluid is lost salivary secretion is decreased, dry mouth feeling, motivated to drink water, fluid balance restored

Question 11

How does the body regulate fluid output?

Answer 11

1. Fluid output, mainly urine volume, adjusts to fluid intake
2. 3 main factors for controlling volumes of plasma, IF and ICF:
   1. Concentration of electrolytes in ECF (Important concept: Water ‘follows’ sodium)
   2. Capillary blood pressure
   3. Concentration of proteins in blood

Question 12

Describe electrolytes

Answer 12

1. Compounds that dissociate in a water solution into separate particles called ions e.g. ordinary table salt (NaCl 🡪 Na+ and Cl-)
2. Can conduct electrical current
3. Fluid balance is largely regulated by electrolytes

Question 13

Describe ions

Answer 13

The dissociated particles of an electrolyte that carry an electrical charge (positive or negative)

Question 14

List the important positively charged ions (cations)

Answer 14

1. Sodium (Na+)
2. Potassium (K+)
3. Calcium (Ca++)
4. Magnesium (Mg++)

Question 15

List the important negatively charged ions (anions)

Answer 15

1. Chloride (Cl–)
2. Bicarbonate (HCO3–)
3. Phosphate (HPO4-)
4. many proteins

Question 16

Each body fluid compartment has different levels of the various important ions, which helps ____________

Answer 16

Control water & electrolyte balance between them

Question 17

Describe the balance of ions in extracellular fluid

Answer 17

ECF (plasma + IF): Sodium (Na+) & Chloride (Cl–)

Question 18

Describe the balance of ions in intracellular fluid

Answer 18

ICF: Potassium (K+), Phosphate (HPO4- -) and negatively charged proteins

Question 19

What are the functions of the important elements and ions in the body?

Answer 19

1. Iron 🡪 hemoglobin
2. Iodine 🡪 thyroid hormones
3. Potassium (K+) 🡪 nerve conduction
4. Bicarbonate (HCO3-) 🡪 acid-base balance
5. Calcium (Ca++) 🡪 bone formation, blood clotting, muscle contraction
6. Chloride (Cl-) 🡪 HCl production

Question 20

How does sodium impact fluid volume?

Answer 20

1. Electrolytes influence the movement of water among the 3 fluid compartments of the body.
2. ECF electrolyte concentration affects fluid volumes.
3. “Where sodium goes, water soon follows”

Question 21

What body secretions contain Na+?

Answer 21

1. Saliva
2. Gastric secretions
3. Bile
4. Pancreatic juices
5. Intestinal secretions

Question 22

___________ is the most abundant & important cation of plasma and is the chief method of fluid regulation in the kidneys

Answer 22

Sodium (Na+)

Question 23

How do aldosterone and sodium interact?

Answer 23

Aldosterone (from adrenal cortex) increases Na+ reabsorption in kidney tubules, this increases water reabsorption and in turn increases ECF

Question 24

Why are saline IVs given in cases of severe blood loss

Answer 24

1. increases the amount of Na+ in blood
2. fluid/water will move from IF to plasma
3. blood volume increases
4. blood pressure stabilizes

Question 25

_________ is when the amount of Na+ in IF increases above normal

Answer 25

Edema

Question 26

_________ are depressions in swollen subcutaneous tissue that do not rapidly refill

Answer 26

Pitting edema

Question 27

Describe Antidiuretic Hormone (ADH)

Answer 27

1. Released from posterior pituitary gland to increase kidney tubule reabsorption of sodium and water from tubular urine back into blood 2. This function increases ECF (and total body fluid) by decreasing urine volume (Figure 19-5)

Question 28

Describe the regulation of fluid intake

Answer 28

1. ECF electrolyte concentration influences ECF volume 2. Increase in ECF directly increases ECF volume, this Increases the movement of water out of ICF and by increasing ADH secretion, which decreases urine volume

Question 29

Describe the exchange of fluid by blood

Answer 29

1. Capillary blood pressure pushes water out of blood, into interstitial fluid 2. Oppositely blood plasma protein (BPP) concentration pulls water into blood from interstitial fluid 3. Hence, these two forces regulate plasma and interstitial fluid volume under usual conditions

Question 30

Describe Blood Plasma Proteins (BPP)

Answer 30

1. Act as a ‘water-holding’ or ‘water-pulling’ force - Hold water in blood and Pull water into blood from IF 2. Decrease in concentration of BPP results in less water ‘pulled’ into blood from IF 3. IF volume varies more than plasma volume 4. The two forces of capillary blood pressure and the concentration of blood plasma proteins regulate plasma and IF volume under ‘normal’ conditions

Question 31

Describe dehydration

Answer 31

1. Total volume of body fluids less than normal 2. Interstitial fluid volume shrinks first, and then if treatment is not given, ICF volume and plasma volume decrease 3. Dehydration occurs when fluid output exceeds intake for an extended period 4. Loss of skin elasticity (turgor) is a clinical sign of dehydration

Question 32

Describe overhydration

Answer 32

1. Total volume of body fluids greater than normal 2. Overhydration occurs when fluid intake exceeds output 3. Various factors may cause this (e.g., giving excessive amounts of intravenous fluids or giving them too rapidly may increase intake above output) 4. Water intoxication may result from rapidly drinking large volumes of water or giving hypotonic solutions to persons unable to dilute and excrete urine normally 5. The danger of overhydration is that it puts a heavy burden on the heart.