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Phys TT2

Terms in this set (44)

Types of body fluid distribution (3)
- Intracellular
- Extracellular
- Plasma

50 - 70% of body mass is water
Extracellular Fluid
- 20% of body mass
- Major cation is Na+
Intracellular Fluid
- 40% of body mass, major cation is K+
What is the primary determinant of water requirement?
Caloric Intake
____ animals need more water (+ cals) than ___ animals
smaller, larger
Pathways for Water Movement (3)
- Lipid pathway: Diffusion of water across lipid bilayer
- Water pathway: Aquaporins
- Pores/Intercellular gaps: Specialized capillaries and lymphatics
Lipid pathway
- pathway for water movement
- Diffusion of water across lipid bilayer
Higher [water] + large surface area cunteract general low permeability
Water Channels
- Pathway for water movement
- Aquaporins
- Found in tissues where there is a high, regulated water flux (kidneys, gut, rbc)
Pores/Intercellular gaps
- Pathway for water movement
- Specialized capillaries and lymphatics (e.g. glomerulus)
Osmotic Pressure
Hydrostatic pressure required to oppose the movement of water through a semi-permeable membrane in response to an osmotic gradient
- Most impt one
Osmotic Gradient
The difference in particle []'s on 2 sides of a membrane
Osmolarity
The [] of solutes in a solution that exert an osmotion
Osmolality VS Osmolarity
Osmolality: mmoles of solute/kg of water. Typically measured by a machine

Osmolarity: mmoles of solute/L of water. Calculated by [] of specific ions in solution (Na+, Glucose, Urea)

Difference in the context of the cell is minor so often use terms interchangeably
Osmolarity VS Tonicity
Osmolarity: teh [] of all the solutes that are in the solution. Those that can readily cross a membrane and those that cannot


Tonicity: The [] of solutes that cannot readily cross membranes, thus influencing water movement

Fluid will move across a membrane until the tonicities on each side are the same
ECF particles determining volume
- Sodium
- Anions (Chloride, Bicarbonate)
- Glucose
ICF particles determining volume
- Potassium
- Anions (Chloride, Bicarbonate)
The total body content of ____ is the major determinant of _____ (intravascular + extravascular) volume
Sodium, ECF
Physical Pressure (P)
- Hydrostatic
- Generated by the heart and circulatory system
- Usu. greater inside the vessel VS outside, so it tends to force fluid out
- Counterbalanced a little by ohysical pressure in the interstitial fluid (Pif)
Oncotic pressure (pie)
- The osmotic pressure generate by proteins dissolved in plasma.
- Dont tend to leave the vascular system so they typically "pull" fluid back into vasculature
Starling forces
P + pie
- Often determine the net movement of fluid into and out of capillaries bc ion [] are usu stable and balanced.
- Renal system balances the ions in several complex pathways
The sum of the __ effects of __ + the ____ effects of ____ leads to an effective osmolarity of approx. ____ mOsm/L
osmotic, ions, oncotic, proteins, 300 mOsm/L
Dehydration
- Failure to sustain fluid requirements
- lack of sufficient body fluid
- can be due to excessive loss (diarrhea, sweat, feces, urine) OR insufficient intake
- % loss in body weight
Clinical signs usu seen but not specific to dehydration
- Tachycardia
- Sunken eyes
- Delayed CRT
- Blood pressure decreased
Lab signs of dehydration
- PCV increased
- Total plasma protein Increased
<5% dehydrated
not clinically detectable
5-6% dehydration
subtle loss of skin elasticity
6-8% dehydration
- Skin tent delayed
- CRT slightly increased
- Dry MM
10-12% dehydration
- Skin tent stands in place
- CRT increased
- eyes sunken
- dry mm
- Shock (tachycardia, cold extremities, weak pulses)
12-15% dehydration
Death imminent
Fluid Therapy Composition of Fluids
- Balanced
- Unbalanced
- Crystalloids
- Colloids
Balanced FT
ion [] are similiar to ECF
Unbalanced FT
ion [] are diff from ECF
Crystalloids
Solutions containing ions and solutes capable of moving freely b/w diff fluid containing body compartments
Colloids
Solutions containing larger molecular weight molecules that remain in plasma exert an osmotic effect to retain volume of fluids in th evascular space (dextrans, hetastarch, etc).
Isotonic solutions post IV Admin
- 0.9% NaCl, LRS
- Increase in ECF volume
- No osmotic driving force to move fluid to ICF, therefore ICF unchanged
hypotonic solution post IV Admin
- 0.45% NaCl
- Decrease in ECF osmolality
- Fluid moves to ICF due to osmotic effects volume of both ECF and ICF increased
Hypertonic solutions post IV Admin
- 7.5% NaCl
- Large increase in ECF osmolarlity
- High osmotic driving force to move fluid from ICF to ECF
Kidney Function
1. Primarily an Excretory organ
2. Maintenance of ECF volume and BP (fluid balance)
3. Endocrine functions
The kidney as an excretory organ
Eliminates byproducts of protein and nucleic acid metabolism (dietary, muscle), drugs, toxins, metabolites
- BUN: Blood urea nitrogen, product of amino acid degradation
- Cr: Creatinine, SDMA (symmetric Dimethyl Arginine), products of muscle and cellular metabolism, etc
- Many others excreted (toxins and drugs, ketones, sulphates, etc)
Endocrine Functions of Kidney
- Vitamin D metabolism
- Erthropoietin (EPO) production
- Renin-Angiotensin-Aldosterone system (renin production)
Juxtaglomerular Apparatus
Afferent and efferent arterioles, mesangial and JG cells, and macula densa - renin release

Part of nephron
Macula densa
A specialized portion of distal tubular epithelial cells adjacent to JG cells

Part of nephron
Kidneys remove _____ _____ from plasma in direct proportion to the level of renal function
nitrogenous wastes
Kidneys removing wastes from plasma is impt bc .... (2)
1. The molecules that accumulate when the kidney is failing are toxic to cells and tissues leading to clinical disease

2. The level of these molecules in the blood can be used to assess renal function
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