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1

- balance and constancy
- keeping the internal environment compatible with life (pH 6.8-8.0)

Homeostasis

2

Body Fluid Compartments

60% Body weight is Water
40% Body weight is Intracellular Fluid
20% Body weight is Extracellular Fluid

15% Body weight (75% ICF) Interstitial Fluid
5% Body weight Plasma

3

Babies are made up of __ water

75%

4

- fluid inside the normal body cavities
- includes intraocular fluid, synovial fluid, water in gallbladder and water in urinary bladder

Transcellular Fluid

5

Extracellular Fluid is divided into

1. Transcellular Fluid
2. Insterstitial Fluid
3. Plasma

6

Constituents of ECF and ICF

• Made up of Ions and Proteins
– CATIONS: Positively-charged molecules
– ANIONS: Negatively-charged molecules

7

- Number 1 Cation in the ECF
- main determinant of plasma osmolarity (where sodium goes, water follows)

Sodium

8

- Number 1 Cation in the Intracellular Fluid (ICF)

Potassium

9

Number 1 Anion in the ECF

Chloride

10

Number 1 Anion in the ICF

Phosphate and organic Anions

11

• Flow of water from a solution of low solute concentration to a solution of high solute concentration across a semi-permeable membrane

Osmosis

12

Transport of Water

- Movement of water is via OSMOSIS (utilize water channels)
- It is based on concentration gradient

13

Movement of Solute and Solvent

Solute - move from high concentration to low concentration
Solvent - move from low concentration to high; hypertonic to hypotonic

14

– Number of osmotically active particles in a solution
– One osmole = 6.02 x 10^23 of solute particles

OSMOLE (Osm)

15

Normal value of Osmolarity

300

16

– Osmoles per kilogram of water (according to weight of water)
– more accurate because it doesn't vary according to temperature

OSMOLALITY

17

– Osmoles per liter of water (according to volume)
– “Pogi Points”
– Equal to molar solute concentration x number of particles that the solute dissociates into once dissolved
– Approximately 300mOsm/L in the body compartments
– PLASMA OSMOLARITY: Mainly determined by Sodium
concentration

OSMOLARITY

18

The higher the osmolarity, the __ the ability to attract water

higher

19

Osmolarity vary according to temperature. Water tends to expand in high temperature. The higher the temperature, the __ the serum osmolarity

lower

20

At human body temperature (37.5C), the difference between the osmolarity and osmolality is __

Less than 1%

21

– Not completely semi-permeable membrane
– Takes into account effect of solute permeability

Effective Osmolarity or Tonicity

22

TYPES OF SOLUTIONS

– Hypertonic solution
– Isotonic solution
– Hypotonic solution

23

What is the difference between:
Isotonic, Hypotonic, Hypertonic
Isoosmotic, Hypoosmotic, Hyperosmotic

“…TONIC”: impermeant solutes; may cause change in cell
volume.

“…OSMOTIC”: permeant solutes; may NOT cause change in
cell volume

24

What will happen if you have a RBC that is 300 mOsm/L when you place in hypotonic solution (209mOsm/L)?

Water will move from outside to inside. The cell will swell.

25

What will happen if you have a RBC that is 300 mOsm/L when you place in hypertonic solution (360mOsm/L)?

Water will move from inside of RBC to outside causing RBC to SHRINK.

26

Volume and Osmolarity of ECF and ICF in Abnormal States

• Water moves because of changes in TONICITY, and not
VOLUME
– ISOTONIC INFUSION
– HYPERTONIC INFUSION
– HYPOTONIC INFUSION

27

– Due to loss of sodium in the ECF or gain of excess water in the ECF
– E.g. diarrhea, vomiting, diuretics, Addison’s Disease, Syndrome of Inappropriate Anti-Diuretic Hormone Secretion (SIADH)

HYPONATREMIA

28

– Due to excess sodium in the ECF or loss of water in the ECF
– E.g. Diabetes Insipidus(Central and Nephrogenic), Dehydration secondary to exercise or fever

HYPERNATREMIA

29

• Contributes to homeostasis
• Composed of the kidneys, ureters, bladder, urethra

RENAL SYSTEM

30

Functions of the Kidneys

1. Excretion of waste products and foreign chemicals
– (Urea, Uric Acid, Creatinine, Bilirubin, hormone metabolites)

2. Regulation of water, electrolyte balances

3. BP Regulation
– Excretion of variable amounts of H2O and NaCl
– Production of Renin

4. Regulation of Acid-Base Balance
– Excretion of acids
– Urinary buffer systems

5. Produce Erythropoietin (EPO)

6. Hormone Secretion
– Active form of Vit D, kinins, renin

7. Gluconeogenesis