Chapter 25: Body Fluids and Compartments (Discussion 1) Flashcards
Liquid Intake (2)
Ingest H2O & Foods
Synthesis from oxidation of carbs
Liquid Output (4)
Insensible H2O loss (diffusion through skin/evaporation from respiratory membranes)
Sweat
Kidneys (urine)
Feces
Body Fluid Composition
3/5 of the body
2/3 Intracellular Fluid (ICF) = 28 L
1/3 Extracellular Fluid (ECF) = 14L
Extracellular Fluid Composition
Plasma (3L)
Interstitial Fluid (1L)
Transcellular:
a. Synovial (joints)
b. Peritoneal (abdominal cavity lining)
c. Pericardial (around heart)
d. Cerebrospinal fluid (brain and spine)
e. Intraocular
Blood Composition
Plasma, cells, proteins
Blood volume - 5 L
Hematocrit
% of blood composed of red blood cells (RBCs)
Men: 0.4
Women: 0.36
Anemia
Decreased hematocrit
Polycythemia
Increased hematocrit
Donnan Effect
Large, impermeable proteins (- charge) in plasma attract cations, slightly higher cation concentration in plasma than interstitium
ICF Ions
K+ Ca++ Mg++ PO4 -3 Protein (mostly - charge)
ECF Ions
Na+ (originally sea water)
HCO3-
Cl-
Osmosis
Diffusion of water across a semi-permeable membrane to region of higher solute concentration
Cell membranes mostly permeable to water/impermeable to ions.
Osmotic pressure (pi)
Amount of pressure needed to oppose osmotic forces
Tonicity
Defined w/ relationship to other side of membrane
It is the solute concentration of the ECF in relation to the solute concentration inside the cell
Isotonic
Same concentration –> no change
Hypotonic
Lower concentration than cell –> increase cell volume
Hypertonic
Higher concentration than cell –> decrease cell volume
What ions account for most solute in ECF
Na and Cl (~140 mEq/L)
Hyponatremia
Decrease Na in plasma
Caused by hypo-osmotic overhydration or hypo-osmotic dehydration
Hypo-osmotic Overhydration
Excess H2O
Excess ADH (causes H2O reabsorption in kidneys), or drinking a ton of water
↑ICF and ↑ECF volume
Hypi-osmotic Dehydration
Loss of NaCl
Diarrhea, vomiting, excess diuretics, Addison’s disease (↓ aldosterone [aldosterone helps reabsorb NaCl])
↓ECF and ↑ICF volume
Hypernatremia
Increase Na in plasma
Hyper-osmotic Overhydration
Increase in NaCl
↑ aldosterone (Conn’s syndrome)
↑ECF ↓ICF
Hyper-osmotic Dehydration
Decrease in H2O
Dehydration (sweating), central diabetes insipidus (No ADH), “Nephrogenic” diabetes insipidus (kidneys don’t respond to ADH)
↓ICF and ↓ECF volume
Edema
Excess fluid buildup in tissues
IC edema
↓nutrition or ↓metabolism in tissue
–> Damaged ion pumps –> ↑ ICF [ion] –> osmosis of H2O into cell
–> Inflammation –> ↑cell membrane permeability
Filtration Rate
Kf x (Pcapillaries – PIF - πc+ πIF)
Kf: capillary filtration coefficient
Filtration = Kf x NFP
Increase in Pcapillaries
Excessive H2O retention (kidneys)
Increase venous pressure (heart failure)
Decrease in πc
Nephrotic syndrome (↓plasma [protein])
Liver cirrhosis: ↓plasma protein production; Portal vein compressed –> ↑Pc –> fluid build-up in abdomen (ascites)
Increase in πIF
Lymphatic blockage - prevent IF flow
Due to: infection, cancer, surgery
Safety Factors Against Edema (3)
- Low tissue compliance
Functional at negative pressure (IF is actually more of gel w/o any free fluid)
IF normally ~-3 mmHg
- Increase lymphatic flow (can increase x10-50)
Safety factor of ~7 mmHg - IF “protein washdown” as filtration increases
Safety factor of ~7 mmHg
Effusion
Edema in potential spaces
Potential Spaces
Pleural Cavity
Pericardial
Peritoneal (abdominal effusion is called ascites)
Synovial - joint and bursae (small fluid sacks in joints)
