Physiology

• Body fluid compartments consist of the extracellular matrix, extracellular fluid, and intracellular fluid
• Extracellular matrix:

  • Immediate environment that surrounds each individual cell
  • Provides a scaffold for cellular attachments
  • Transmits information in the form of chemical messengers to regulate activity, migration, growth, and differentiation
• Extracellular fluid:

  • Fluid outside the cell
  • Consists of plasma and interstitial fluid
  • Plasma makes up about 20-25% of the fluid portion of blood
  • Interstitial fluid makes up the remaining 75-80%
  • Interstitium is the space containing interstitial fluid
• Intracellular fluid:

  • Fluid located inside the cells
  • Contains many different proteins important in regulating cellular events such as growth and metabolism
• Rule: 60-40-20-5

  • All solutes and water that enter or leave the body do so via extracellular fluid
  • Intracellular and extracellular fluids are in osmotic equilibrium
  • Water moves between these compartments only when an osmotic pressure gradient exists
  • Equilibrium of intracellular and extracellular fluid osmolality occurs primarily by shifts in water and not shifts in solute
• Compartmentalization:

  • The composition of extracellular fluid is very different from that of intracellular fluid
  • Maintained by barriers between the compartments
  • Properties of the barriers determine which substances can move between compartments
• • Aqueous solution containing organic molecules, ions, cytoskeletal elements, and organelles
  • Region outside the nucleus
• Cellular structure:

  • Nucleus:
  • Spherical/oval structure usually near the center of the cell
  • Stores and transmits genetic information
  • Forms a fine network of threads known as chromatin
  • Nuclear envelope:
  • Surrounds the nucleus as a barrier
  • Contains RNA molecules that determine the structure of proteins synthesized in the cytoplasm
  • Nucleolus:
  • Most prominent structure in the nucleus
  • Associated with specific regions of DNA containing genes for forming RNA found in ribosomes
  • Cytoplasm:
• Membranous endoplasmic reticulum:

  • Most extensive cytoplasmic organelle with a network of tubular and flat vesicular structures
  • Rough ER has ribosomes bound to its surface and appears as flattened sacs
  • Smooth ER has no ribosomal particles on its surface and has a branched tubular structure
• Golgi complex:

  • Consists of flattened membranous sacs and vesicles
  • Transport vesicles sort modified proteins for secretion
  • Secretary vesicles contain proteins to be secreted from the cell
• Lysosome:

  • Digests damaged cellular structures, food particles, and unwanted matter
  • Contains acidic fluid and various digestive enzymes
  • Primary lysosomes have degradative enzymes
  • Secondary lysosomes result from the fusion of primary lysosomes with food vacuoles
• Peroxisome:

  • Dense oval bodies enclosed by a single membrane
  • Found primarily in liver and kidney cells
  • Consumes molecular oxygen and is involved in fatty acid breakdown
• Mitochondria:

  • Elongated, rodlike structure with outer and inner membranes
  • Inner membrane is folded into sheets known as Cristae
  • Contains enzymes for energy production processes
• Non-membranous ribosome:

  • Protein factories of a cell
  • Synthesize protein molecules from amino acids using genetic information carried by RNA messenger molecules
• Vaults:

  • Associated with nuclear pores
  • Function in regulating a cell's sensitivity to certain drugs
• Centrosomes/centrioles:

  • Composed of fused microtubules
  • Generate spindle fibers during cell division
• Cytoskeleton:

  • Filamentous network associated with maintaining and changing cell shape and producing cell movement
  • Actin filaments, intermediate filaments, and microtubules are components of the cytoskeleton