The document summarizes the key functions and characteristics of the body's fluid compartments. It discusses: - Body fluids facilitate transport of nutrients, waste removal, and cellular metabolism. Total body water is 60% of weight, with two-thirds being intracellular fluid and one-third extracellular fluid. - Extracellular fluid contains sodium as the main cation while intracellular fluid contains potassium. Both fluids contain bicarbonate, chloride, and proteins as main anions. - Transport of molecules across cell membranes can occur passively via diffusion or actively via carrier proteins and active transport pumps requiring ATP. Endocytosis and exocytosis allow transport of larger particles into and out of cells.

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