medicine

1. BODY FLUIDS

2. INTRODUCTION
FUNCTIONS OF BODY FLUIDS
• Facilitate in the transport [nutrients, hormones, proteins,& others]
• Aid in removal of cellular metabolic wastes
• Provide medium for cellular metabolism
• Regulate body temperature
• Provide lubrication of musculoskeletal jts. and all
• body cavities [parietal, pleural fluids]

3. THE BODY FLUIDS
• Distribution of total body water (TBW):
• - The total body water (TBW) is approximately 60% of body weight (42litres).
• - The percentage of TBW is highest in newborns (70%) and adult males(60%)
and lowest in adult females(50%).

5. • -TBW is distributed as follows :
• (1) Intracellular fluid (ICF):
• - This constitutes about 2/3 of the TBW (about 40% of the body weight).
• - It averages 28 litres.
• (2) Extracellular fluid (ECF):
• - This constitutes about 1/3 of TBW (about 20% of the body weight).
• - It averages 14 litres.
• - It includes the following subdivisions:
• Intravascular fluid (the plasma):
• - This constitutes about 5% of the body weight
• - It averages 3 litres.
• Interstitial fluid (= tissue fluid):
• - It constitutes about 15 % of the body weight.
• - It averages 11 litres.

6. • Solutes – dissolved particles
• Electrolytes – charged particles
• Cations – positively charged ions Na+, K+ , Ca++, H+
• Anions – negatively charged ions Cl -, HCO3, PO4
• Non-electrolytes – Uncharged Proteins, urea, glucose, O2, CO2

7. • Composition of the ICF & ECF:
• 1) The intracellular fluid contains large amount of potassium (K+) as the chief
cation with small amount of Mg+, Na+ & phosphates and proteins as the anions.
• 2) The extracellular fluid contains sodium (Na+) as the chief cation, with small
amount of Ca++ & K+ while chlorides (Cl-) & bicarbonate as the anions.

10. DIFFUSION
• Movement of solutes from an area of higher concentration to an area of lower
concentration in a solution and/or across a permeable membrane (permeable for
that solute)
• Movement occurs until near equal state
• It is passive process

11. OSMOLALITY
• Osmolality - amount of solute or particles in KG of water.
• Osmolality = solute/solvent
• Plasma osmolality = 2 x (Na) +
• (Glucose/18)+(Urea/2.8)
Normal value ( 275-290mOsm/L )

12. BODY FLUIDS CHARACTERISTICS
• Electrically neutral
• Osmotically maintained Specific no of particles per volume of fluid
• ECF Osmolality = ICF Osmolality
• Homeostasis must preserve narrow plasma osmolality Range for optimal cellular
functioning and viability

13. • To maintain homeostasis water intake must
• match with water excretion.
• Water balance
• • Daily Intake of Water
• – it is ingested in the form of liquids or water in the food
• – it is synthesized in the body as a result of oxidation of
• carbohydrates, adding about
• • Daily Loss of Body Water
• • Insensible Water Loss
• • evaporation from the respiratory tract and diffusion
• through the skin
• • Fluid Loss in Sweat
• • Water Loss in Feces
• • Kidneys

14. DISTURBANCE IN COMPOSITION
• Sodium (Na+)
• It is the most abundant cation of the extra cellular fluid. 90 % of total ECF cations
• Normal value is 135- 145mom/l
• Most important ion in regulating water balance
• Important in nerve and muscle function.
• Hyponatremia Defined as Sodium level < 135mmol/L
• Hypernatremia Na+ more than 145 mmol

15. TRANSPORT ACROSS CELL MEMBRANE
• Transport across cell membrane
• [I] Transport of small molecules (Micromolecules):
• A) Passive transport (diffusion):
• 1- Simple diffusion.
• 2- Facilitated diffusion.
• B) Active transport:
• 1- Primary active transport.
• 2- Secondary active transport.

16. • [II] Transport of large molecules (macromolecules):
• “Vesicular Transport”
• Endocytosis.
• Exocytosis.

17. PASSIVE
TRANSPORT=
DIFFUSION
• (1)Simple diffusion
• - Simple diffusion needs no energy.
• - occurs down an electrochemical gradient (“downhill”).
• - They are 3 pathways for passage through the cell membrane
by simple
• diffusion:
• A) Diffusion through lipid bilayer:
• - Lipid soluble molecules e.g. O2 & CO2 and steroid hormones.
• - Charged particles e.g. Na+ or K+ & glucose can not pass.
• B) Diffusion through protein channels:
• - Important for diffusion of ions & some water soluble
substances.
• - Highly selective i.e. there are specific channels for transport of
Na+, K+.
• C) Diffusion through aquaporin channels: ( Osmosis)
• - It is the net diffusion of H2O across a semipermeable
membrane by

18. (2) FACILITATED DIFFUSION
• l Characters:
• 1- Depend on the concentration gradient across the membrane.
• 2- Require no energy.
• 3-Require carrier “carrier protein”.
• lExample:
• - Transport of glucose into skeletal muscle and adipose cells by the GLUT4.
• 1- Glucose binds to a specific type of carrier protein called the glucose
• transporter (GluT) on the outside surface of the membrane.
• 2- As the transporter undergoes a change in shape, glucose passes
• through the membrane.
• 3- The transporter releases glucose on the other side of the membrane.

19. TYPES OF CARRIER PROTEINS
1- Uniport system:
• - A carrier that transports one substance in one direction e.g. D-glucose.
2- Co-transport or Symport system::
• - A carrier that transports two substances simultaneously in the same
• direction.e.g. Na+-sugar transporters (glucose, mannose, galactose).
3- Countertransport or Antiport system:
• - A carrier that transports one substance in one direction and another
• substance in the opposite direction. e.g. Na+ in & Ca++ out in nerve cell.

20. ACTIVE TRANSPORT
• - It is the net movement of molecules and ions across a membrane from the
• region of lower to the region of higher concentrations.
• - It requires energy (ATP) & carrier protein.
• (1) Primary active transport:
• - Active transport can move substances through cell membrane against concentration
gradient.
• - It requires energy (ATP) & carrier protein with ATP-ase activity.
• ■ Example: (Na+-K+ pump)
• - Sodium is more concentrated on the outside of the cell, whereas potassium is
• more concentrated on the inside of the cell. The Na + /K + pump helps to
• maintain these concentration differences by transporting 3Na + out of the cell
• and 2 K + into the cell.
• - Energy is provided by breakdown of ATP.

21. (2) SECONDARY ACTIVE TRANSPORT (COUPLED
TRANSPORT):
• - Transport of two or more solutes is coupled.
• - One of the solutes, usually Na+, moves down its concentration gradient
• (downhill), and the other solute moves against its concentration gradient
• (uphill).
• - Energy, as ATP, is not used directly, but it is supplied indirectly in the Na+
• concentration gradient across the cell membrane.
• - The Na+-K+ ATPase creates and maintains this Na+ gradient.
• ■ Example:
• - Na+-glucose cotransport in intestinal & renal cells.

22. ENDOCYTOSIS
• Definition:
• Transport of macromolecules or large particles from outside to inside cell “through vesicle
formation”
• Mechanism:
• - Portion of cell membrane invaginate to envelop a substance.
• - The membrane pinches off to form an intracellular vesicle.
• - Vesicle fuse with primary lysosomes forming secondary lysosomes that
• contain hydrolytic enzymes digesting the macromolecules contents of
• the vesicle.

23. TYPES OF ENDOCYTOSIS
1- Phagocytosis (cell eating):
• - For large particles e.g. bacteria.
• - Occurs only in macrophages.
2- Pinocytosis (cell drinking):
• - For water soluble macromolecules e.g. protein.
• - Occurs in all cells.
• 3- Receptor-mediated endocytosis:
• - Specific substances are ingested e.g. LDL.

24. EXOCYTOSIS
Definition:
• It is the process by which cells release their secretions to the exterior.
Mechanism:
• - Vesicles already present within the cell.
• - Vesicles fuses with the plasma membrane & release its contents into the
• fluid surrounding the cell.

25. •Thank you