Body Fluids, Type and Regulation
Body
Fluids
Body Fluids
- Total
amount of fluid in the human body is approximately 70% of body weight - Body fluid
has been divided into two compartments –
§ Intracellular fluid
(ICF)
Ø Inside the cells
Ø 55% of total body water
§ Extracellular fluid
Ø Outside the cells
Ø 45% of total body water
Composition of body fluids
- Organic substances
§ Glucose
§ Amino
acids
§ Fatty
acids
§ Hormones
§ Enzymes
- Inorganic substances
§ Sodium
§ Potassium
§ Calcium
§ Magnesium
§ Chloride
§ Phophate
§ Sulphate
Extracellular fluid
·
Interstitial fluid
§ Present between the cells
§ Approximately 80% of ECF
·
Plasma
§ Present in blood
§ Approximately 20% of ECF
·
Also includes
§ Lymph
§ synovial fluid
§ cerebrospinal fluid
§ pleural, pericardial and peritoneal fluids
1)
Extracellular fluids:
a) Interstitial Fluid: also known as
intercellular fluid and tissue fluid is fluid between the cells of
multi-cellular organisms which delivers materials to the cells, intercellular
communication, and removal of metabolic waste.
·
It represents the largest portion of
the ECF compartment.
·
Interstitial fluid consists of
a water solvent containing amino acids, sugars, fatty acids, coenzymes, hormones,
neurotransmitters, salts, as well as waste products from the cells.
- This
fluid presents as gel-like extracellular matrix. - The
plasma and the interstitial fluid integrate through pores in the
blood capillaries which allow water and most dissolved substances except
protein to diffuse. - Oxygen,
nutrients, and regulatory molecules travelling in the blood must first
pass into the interstitial fluid before reaching the body cells. Waste
products and hormone secretions from the cells must first pass into the
interstitial fluid before reaching the blood plasma. - The
exchange of material across the capillaries occurs at high rate by diffusion
in both directions. - The
composition of tissue fluid depends upon the exchanges between the cells
in the biological tissue and the blood. This means that tissue fluid has a
different composition in different tissues and in different areas of the
body. - The
composition of tissue fluid depends upon the exchanges between the cells
in the biological tissue and the blood. This means that
tissue fluid has a different composition in different tissues and in
different areas of the body - Acting
as a media for intercellular communication.
Barriers separate ICF, interstitial fluid and
plasma
·
Plasma
membrane
§ Separates
ICF from surrounding interstitial fluid
·
Blood
vessel wall
§ Separate
interstitial fluid from plasma
2) Blood plasma:
·
It is the fluid portion of the blood.
·
The blood transports oxygen from the
lungs to the body cells and carbon dioxide from the body cells to the lungs.
·
Blood also transports nutrients
derived from food in the intestine to the body cells, other nutrients between
organs.
3) Lymph
- Clear and colorless fluid
- 96% water and 4% solids
- Solids –
§ Proteins
Ø 2-6% of solids
Ø albumin, globulin, fibrinogen, prothrombin, clotting
factors, antibodies, enzymes
§ Lipids
Ø 5-15%
Ø Chylomicrons
Ø Lipoproteins
§ Carbohydrates
Ø Glucose mainly
§ NPN
(Non protein Nitrogen)
Ø Urea and creatinine
§ Electrolytes
Ø Sodium, calcium, potassium, chloride, bicarbonates
Functions of Lymph
- Return
protein from tissue spaces into blood - Removal of
bacteria, toxins and other foreign bodies from tissues - Maintain
structural and functional integrity of tissue - Route for
intestinal fat absorption - Transport
lymphocytes
2)
Intracellular Fluid:
The cytosol or intracellular fluid is the
liquid found inside the cells.
Physiological Function: The
cytosol has no single function and instead it is the site of multiple
cell processes including metabolic processes (such as glycolysis, gluconeogenesis,
PPP). It is also involved in signal transduction from the cell membrane
to sites within the cell.
The body fluid composition of tissue varies by
- Tissue type:
lean tissues have higher fluid content than fat tissues. - Gender: males have
more lean tissue and therefore more body fluid. - Age: lean tissue
is lost with age and body fluid is lost with it.
Body fluid composition:
- Water
- Dissolved solutes
a)
Organic substances – protein, glucose
b)
Inorganic substances – electrolytes e.g Na+, K+
Since
water passes freely across cell membrane, the volume of the various fluid
compartments are determined by unique solutes that are confined to each space.
For
the total extracellular fluid compartment it is sodium and for the
intracellular space, it is potassium.
Electrolytes of the body fluids:
- Electrolytes
are salts and minerals that can conduct electrical impulses in the body. - Common
human electrolytes are sodium, chloride, potassium, calcium, and bicarbonate. - Electrolytes
in body fluids are charged, - It can be:
- Cation – positively charged electrolyte, e.g .Na+, k+, Ca+2
- Anion – negatively charged electrolyte, e.g, Cl– , HCO3– po4-3
- The chief extracellular
cation is Na+ - The chief intracellular
cations are k+
§ Cl– is the predominant anion outside
cells whereas phosphates constitute the bulk of intracellular anions.
Electrolytes:
·
Control the
fluid balance of the body
·
Important
a)
In muscle
contraction
b)
In energy
generation – and almost every major biochemical reaction in the body.
Movement of body fluids:
Membrane transport
processes:
1) Passive transport
- It is the
movement of substances across a membrane from higher to lower concentration
(down a concentration gradient) - It does not
require metabolic energy.
Simple diffusion –
- It is the
movement of substances from a region of high concentration to a region of low
concentration. - Generally,
simple diffusion of water, gases, and other small uncharged molecules across
plasma membranes can occur in the absence of transport proteins.
Facilitated diffusion –
- It is a
transport of substances across a biological membrane - From an
area of higher concentration to an area of lower concentration by a carrier
proteins.
2) Active transport:
- It is the
movement of substances across a membrane against gradient (from low
concentration to high concentration). - Active
transport requires energy and involves specific carrier proteins.
Movement of fluids due to
1) Hydrostatic pressure
2) Osmotic pressure
1) Hydrostatic pressure:
It is physiological
processes that regulate fluids intake & output as well as movement of water
& substances dissolved in it between the body compartments
2) Osmotic pressure:
The pressure exerted by the
flow of water through a semi-permeable membrane separating two solutions with
different concentration of solute.
Osmosis:
It is diffusion of a solvent
(usually water molecules) through a semi-permeable membrane from an area of low
solute concentration to an area of high solute concentration.
Osmotic pressure:
- It is pressure which forces
the water to move from where there is little dissolved solute to where there is
lots dissolved solutes. - It is
determined by the number of particles per unit volume of fluids - The amount
of osmotic pressure exereted by a solute is proportional to the number of
molecules or ions. - Osmoles is the unit used to express the concentration in
term of numbers of particles.
Regulation
of body fluids and electrolytes
·
Fluid
intake and output are balanced.
Water Balance:
Water balance exists when
water intake equals water output.
Water Intake:
- The volume
of water gained each day varies from one individual to the next. - About 60%
of daily water is gained from drinking, - Another 30%
comes from moist foods, and 10% from the water of metabolism
Regulation of Water Intake:
- The thirst
mechanism is the primary regulator of water intake. - The thirst
mechanism derives from the osmotic pressure of extracellular fluids and a
thirst center in the hypothalamus. - Once water
is taken in, the resulting distention of the stomach will inhibit the thirst
mechanism.
Water Output:
- Water is
lost in urine, feces, perspiration, evaporation from skin (insensible perspiration), and from the
lungs during
breathing. - The route
of water loss depends on temperature, relative humidity, and physical exercise.
Regulation of Water Output:
- The distal convoluted
tubules and collecting ducts of the nephrons regulate water output. - Antidiuretic hormone from the posterior pituitary causes a
reduction in the amount of water lost in the urine. - When
drinking adequate water, the ADH mechanism is inhibited, and more water is
expelled in urine.
Disorders of water balance:
- Dehydration: water loss exceeds water intake
- Hypotonic hydration: ECF is diluted (there is increase in water,
causing ECF sodium levels to lower (hyponatremia), increase in osmosis occurs
and tissue cells swell (oedema).
Electrolytes
Electrolytes, charged
ions capable of conducting electricity, are present in all body fluids and
fluid compartments. Just as maintaining the fluid balance is vital to a normal
body function, so is maintaining electrolyte balance.
Although the concentration
of specific electrolytes differ between fluid compartments, a
balance of cations (positively charged ions) and anions (negatively charged
ions) always exists.
Electrolytes are important
for
- Maintaining
fluid balance. - Contributing
to acid–base regulation. - Facilitating
enzyme reactions. - Transmitting
neuromuscular reactions.
Electrolyte Balance:
An electrolyte balance
exists when the quantities of electrolytes gained equals the amount lost.
Regulation of Electrolyte Intake:
- A person
ordinarily obtains sufficient electrolytes from food eaten. - A salt
craving may indicate an electrolyte deficiency.
Electrolyte Output:
- Losses of electrolytes occur
through sweating, in the feces, and in urine.
Body Fluids, Type and Regulation Complete Notes PDF
