By:

Dr shahrokhi

CELL is the functional unit of the body

- The body made of ~ 100 trillion plus cells, all surrounded by fluid,

( extra-cellular fluid, ECF) PROTOPLASM - is the different substances that make-up the cell

-Has 5 basic components; WATER, ELECTROLYTE, PROTEINS, LIPIDS, and

CARBOHYDRATES.

WATER: 60% to 75%

ELECTROLYTES:

important (inside the cell) are K+, Mg 2+, Phosphate, Bicarbonate, and small quantities of Na+, Cl- and Ca 2+

PROTEINS: -Constitutes ~ 10% -20% of cell mass.

-2 types ;i) STRUCTURAL PROTEINS ii) GLOBULAR PROTEINS

LIPIDS : most important are phospholipids and cholesterol which make-up ~2% of total cell mass

Phospholipids and cholesterol are mainly insoluble in water and are used to form cell membrane

CARBOHYDRATE : structural role is limited . Major role is nutrition - especially in the form of dissolve glucose in the surrounding extra- cellular fluid .

Composition of the human bodyWater: 60%Protein: 18%

Fats: 18%Minerals: 4%

CytoplasmComponents:Cytosol – gel-like fluidStorage substancesCell organellesCytoskeleton – network of filaments and

fibers

The internal environment

The cell is surrounded by tissue fluid (Internal Environment).

The composition of the internal environment should remain constant within narrow limits.

HomeostasisMaintaining constancy of internal

environment.

Dynamic constancy. Within a certain normal range.

Regulatory mechanisms:Intrinsic:

Within organ being regulated.Extrinsic:

Outside of organ, such as nervous or hormonal systems.

Negative Feedback

Figure 1.5

• Action of effectors amplifies the changes.

• Is in same direction as change.• Examples:

– Oxytocin (parturition).

– Voltage gated Na+ channels (depolarization).

– blood clotting

Positive Feedback

Feed Forward ControlWhen response has to occur rapidly, the

brain uses a principle called feed forward control.

Seen mainly in nervous system. Eg:

Conditioned reflexAdaptive control.

Body Water ContentInfants have low body fat, low bone mass, and

are 73% or more waterTotal water content declines throughout lifeHealthy males are about 60% water; healthy

females are around 50%This difference reflects females’:

Higher body fat Smaller amount of skeletal muscle

In old age, only about 45% of body weight is water

INTRACELLULAR FLUID (ICF)

EXTRACELLULAR FLUID (ECF)

Interstitial fluid

Transcellular fluid - cerebrospinal, pericardial , synovial

Major Compartments for Fluids

Extracellular fluid :It is the internal environment that

immediately surround the units of life of the whole body

Intravascular: within the vascular system

Interstitial: lies between the cellsTranscellular : secreted by epithelial

lining e.g., CSF, pleural fluid ,peritoneal fluid, joint fluid,….

Large volumes are present in disease states, pleural effusion , ascites.

Large losses in diarrhea and vomiting leads to dehydration and electrolyte disturbances.

Fluid Compartments

Figure 26.1

Intracellular fluid

Extra cellular fluid

ICF Plasma ISF CATIONS mmol/L

Na 10145140

K 14544

Ca 155

Mg 4022ANIONS mmol/L

Cl 3105110

HCO3 102831

HPO3 13866

Proteins 45174

Osmolality

mOsmol/L

302.2302.9301.8

Electrolyte Composition of Body Fluids

Figure 26.2