PATHOPHYSIOLOGY II – EXAM I
UNIT 1
Ch. 24: Fluid and Electrolyte Homeostasis and Imbalances, pp. 531-549
BODY FLUID HOMEOSTASIS
Body Fluid: Water within the body and the particles dissolved in it
● Lubricant + Solvent for Chemical Reactions (Metabolism)
● Transports Oxygen, Nutrients, Chemical Messengers, & Waste Products
● Important for Body Temperature Regulation
ALL age groups (Except Infants) → Two-thirds (⅔) BODY FLUID = INTRAcellular // One-third (⅓) = EXTRAcellular
● Extracellular Fluid (Outside the cells) (LOW in Potassium, Magnesium, and Phosphate)
○ Interstitial Compartment (Between the cells) (Few Proteins)
○ Vascular Compartment (Blood Vessels) (Rich in Protein — Albumin)
○ Dense Connective Tissue + Bone
○ Transcellular Fluids → Secreted by Epithelial Cells (ex.) Synovial, Cerebrospinal, Gastrointestinal
■ Sodium (Na +)
■ Chloride (Cl-)
■ Bicarbonate (HCO3-)
● Intracellular Fluid (Inside the cells) (LOW in Sodium/Chloride)
○ Potassium (K+)
○ Magnesium (Mg++)
○ Phosphates (PO4+)
○ Proteins
● Total Body Water = Total amount of water in ALL fluid compartments
○ Body Water Weight % — Age + Proportion of Body Fat
■ Adult Male = 60%
■ Adult Female = 50%
○ Total body water percentage decreases with age
○ ONE LITER (1L) = 1 kg (2.2lb)
● Fluid homeostasis : Interplay of fluid intake and absorption, fluid distribution, fluid excretion, and fluid loss through abnormal routes.
FLUID INTAKE AND ABSORPTION
Fluid Intake: Entry of fluid into the body by any route (PO, IV, GI)
Physiological Triggers of Thirst
● Osmoreceptor-mediated thirst: Increased osmolality (Concetratedness) of extracellular fluid
○ DECREASED → OLDER ADULTS → Risk for Insufficient Intake
● Baroreceptor-mediated + Angiotensin II-mediated Thirst: Decreased circulating blood volume
● Dryness of mucous membranes of mouth + Visceral signals
● Unless fluid intake occurs intravenously → Fluid must be ABSORBED → BEFORE reaching the vascular compartment *
Fluid Distribution: Once reaching the vascular compartment → Distribution into other fluid compartments
Interstitial fluid → Thick layer of fluid that surrounds the bodies cells (Extracellular)
Vascular fluid → Fluid within the vessels; carries blood and lymph
● Vascular ⇄ Interstitial Compartments → EXTRACELLULAR → FILTRATION → Permeable capillaries
○ VASCULAR → INTERSTITIAL
i. Capillary Hydrostatic Pressure: OUTWARD push → VASCULAR fluid → Capillary walls
ii. Interstitial Colloid Osmotic Pressure: INWARD-pulling of particles (proteins) → INTERSTITIAL fluid
○ INTERSTITIAL → VASCULAR
i. Capillary Colloid Osmotic Pressure: INWARD pulling of particles (proteins) → VASCULAR fluid
ii. Interstitial Fluid Hydrostatic Pressure: OUTWARD push → INTERSTITIAL fluid → Capillary walls
○ Hydrostatic = PUSH // Colloid = PULL
○ Two groups of people pushing on opposites sides of a swinging door → Strongest “Push” determines which direction door
will swing
,FIG 24.1 Factors that influence body fluid distribution. Fluid distribution between the vascular and interstitial compartments is the net result of
filtration across permeable capillaries. The distribution of fluid between the interstitial and intracellular compartments occurs by osmosis rather
than by filtration.
● Interstitial ⇄ INTRACELLULAR → OSMOSIS (Osmotic Pressure)
○ How? Cell membranes contain AQUAPORINS → Allow water to pass through
○ Cell membranes are PERMEABLE to Water → Water can move FREELY through the cell membrane
■ Electrolytes and other particles cannot permeate through the cell membrane
■ When there is a difference in particle concentration (osmolality) inside and outside cells because the particles
cannot move freely, the water crosses the membrane rapidly to equalize the osmolality. Osmosis occurs until the
intracellular osmotic pressure and the interstitial fluid osmotic pressure become equal.
FIG 24.3 Fluid homeostasis. Fluid homeostasis is the interplay of fluid intake and absorption, fluid distribution, fluid excretion, and fluid loss
through abnormal routes.
, Fluid Excretion
● Normal: Controlled by HORMONES
○ Urinary tract → URINE (Largest amount of fluid excreted)
○ Bowels → Fecal matter + Normal bowel function
○ Skin → Sweat + Insensible perspiration (Always occurring)
○ Lungs → As a person exhales
■ Antidiuretic Hormone (ADH): Increases blood pressure by regulating fluid loss
● Posterior Pituitary
● Stimuli: Increased osmolality (extracellular fluid), decreased circulating fluid volume, pain, nausea,
stress
● REABSORPTION → WATER → DILUTES BLOOD/Body fluids
○ Decreases Urine Volume → Increases Urine Concentration → Decreases Fluid Excretion
■ Aldosterone: Steroid hormone of the adrenal gland (above kidney) → SODIUM CONSERVATION
● Stimuli: Angiotensin II + Increased potassium ions in plasma
● Renal tubules reabsorb Sodium + Water → SALINE → Expanding the extracellular fluid volume
○ “Where salt goes, water flows.”
○ Decreases fluid excretion
○ ↑ Aldosterone = Urine volume → Smaller
○ ↓ Aldosterone = Urine volume → Larger
■ ADH = “Free Water” hormone → Dilution // Aldosterone = “Salt Water” Hormone → Expansion
■ Atrial Natriuretic Peptide (ANP): Regulates blood pressure through activity in the kidney that promotes the
excretion of water and sodium
● Cardiac ATRIAL cells → Released when ATRIA = Stretched
■ Brain Natriuretic Peptide (BNP): Marker of fluid overload in patients (CV)
● Diastolic pressure increases abnormally (Heart failure) → Released (VENTRICULAR cells)
■ ANP + BNP → Natriuresis (Sodium excretion in the urine) → Water excretion (Following Salt) = Saline
excretion (Maintain osmotic balance + Reduce blood pressure)
■ Renal Prostaglandins: Increase renal blood flow + filtration
■ Renal Sympathetic Nerves: Play a role in blood pressure
■ Urine volume → Dependent on adequate blood pressure to perfuse the kidneys and on the glomerular filtration
rate
● Abnormal Routes
○ Wounds, Burns, Open areas on skin, Fistulas (Drainage)
○ Hemorrhage (Bleeding)
○ GI → Diarrhea + Emesis (Vomiting)
○ GI Tubes (NG Suction)
○ Injury
○ Paracentesis
● INCREASED FLUID INTAKE = INCREASED FLUID EXCRETION = INCREASED URINE VOLUME
○ (Large volume of DILUTE urine)
● DECREASED FLUID INTAKE (or Abnormal Loss) = DECREASED FLUID EXCRETION
○ (Small volume of CONCENTRATED urine) + Thirst may cause an increase in fluid intake
Key Points:
● Fluid Homeostasis: Fluid Intake + Absorption, Fluid Distribution, Fluid Excretion // Fluid Loss through Abnormal Routes
○ Important regulators of fluid intake = Habit and Thirst
● Risk for fluid imbalance = Individuals who are unable to control their own fluid intake
○ Receiving fluids intravenously (IV), Immobile, Unconscious patients
● Fluid (Water/Particles) moves between Vascular → Interstitial (Extracellular) → FILTRATION (Capillaries)
○ Capillary hydrostatic pressure = Primary force promoting fluid movement → Capillaries (Vascular) → Interstitial fluid
○ Plasma colloid osmotic pressure = Primary force that causes interstitial fluid → Capillaries (Vascular)
● Water moves in and out of cells by OSMOSIS
○ Electrolytes do not move freely across cell membranes → Transported by membrane channels/carriers
● Healthy kidneys adjust fluid excretion in response to blood pressure and several hormones
○ Aldosterone → Kidneys → Conserve Saline (salt and water) → Expands extracellular fluid volume
○ ANP and BNP → Saline excretion
○ Antidiuretic hormone (ADH) → Kidneys → Retain Water → Concentrating Urine + Diluting Body fluids
○ Important indicators of body fluid balance = Urine volume and Concentration
UNIT 1
Ch. 24: Fluid and Electrolyte Homeostasis and Imbalances, pp. 531-549
BODY FLUID HOMEOSTASIS
Body Fluid: Water within the body and the particles dissolved in it
● Lubricant + Solvent for Chemical Reactions (Metabolism)
● Transports Oxygen, Nutrients, Chemical Messengers, & Waste Products
● Important for Body Temperature Regulation
ALL age groups (Except Infants) → Two-thirds (⅔) BODY FLUID = INTRAcellular // One-third (⅓) = EXTRAcellular
● Extracellular Fluid (Outside the cells) (LOW in Potassium, Magnesium, and Phosphate)
○ Interstitial Compartment (Between the cells) (Few Proteins)
○ Vascular Compartment (Blood Vessels) (Rich in Protein — Albumin)
○ Dense Connective Tissue + Bone
○ Transcellular Fluids → Secreted by Epithelial Cells (ex.) Synovial, Cerebrospinal, Gastrointestinal
■ Sodium (Na +)
■ Chloride (Cl-)
■ Bicarbonate (HCO3-)
● Intracellular Fluid (Inside the cells) (LOW in Sodium/Chloride)
○ Potassium (K+)
○ Magnesium (Mg++)
○ Phosphates (PO4+)
○ Proteins
● Total Body Water = Total amount of water in ALL fluid compartments
○ Body Water Weight % — Age + Proportion of Body Fat
■ Adult Male = 60%
■ Adult Female = 50%
○ Total body water percentage decreases with age
○ ONE LITER (1L) = 1 kg (2.2lb)
● Fluid homeostasis : Interplay of fluid intake and absorption, fluid distribution, fluid excretion, and fluid loss through abnormal routes.
FLUID INTAKE AND ABSORPTION
Fluid Intake: Entry of fluid into the body by any route (PO, IV, GI)
Physiological Triggers of Thirst
● Osmoreceptor-mediated thirst: Increased osmolality (Concetratedness) of extracellular fluid
○ DECREASED → OLDER ADULTS → Risk for Insufficient Intake
● Baroreceptor-mediated + Angiotensin II-mediated Thirst: Decreased circulating blood volume
● Dryness of mucous membranes of mouth + Visceral signals
● Unless fluid intake occurs intravenously → Fluid must be ABSORBED → BEFORE reaching the vascular compartment *
Fluid Distribution: Once reaching the vascular compartment → Distribution into other fluid compartments
Interstitial fluid → Thick layer of fluid that surrounds the bodies cells (Extracellular)
Vascular fluid → Fluid within the vessels; carries blood and lymph
● Vascular ⇄ Interstitial Compartments → EXTRACELLULAR → FILTRATION → Permeable capillaries
○ VASCULAR → INTERSTITIAL
i. Capillary Hydrostatic Pressure: OUTWARD push → VASCULAR fluid → Capillary walls
ii. Interstitial Colloid Osmotic Pressure: INWARD-pulling of particles (proteins) → INTERSTITIAL fluid
○ INTERSTITIAL → VASCULAR
i. Capillary Colloid Osmotic Pressure: INWARD pulling of particles (proteins) → VASCULAR fluid
ii. Interstitial Fluid Hydrostatic Pressure: OUTWARD push → INTERSTITIAL fluid → Capillary walls
○ Hydrostatic = PUSH // Colloid = PULL
○ Two groups of people pushing on opposites sides of a swinging door → Strongest “Push” determines which direction door
will swing
,FIG 24.1 Factors that influence body fluid distribution. Fluid distribution between the vascular and interstitial compartments is the net result of
filtration across permeable capillaries. The distribution of fluid between the interstitial and intracellular compartments occurs by osmosis rather
than by filtration.
● Interstitial ⇄ INTRACELLULAR → OSMOSIS (Osmotic Pressure)
○ How? Cell membranes contain AQUAPORINS → Allow water to pass through
○ Cell membranes are PERMEABLE to Water → Water can move FREELY through the cell membrane
■ Electrolytes and other particles cannot permeate through the cell membrane
■ When there is a difference in particle concentration (osmolality) inside and outside cells because the particles
cannot move freely, the water crosses the membrane rapidly to equalize the osmolality. Osmosis occurs until the
intracellular osmotic pressure and the interstitial fluid osmotic pressure become equal.
FIG 24.3 Fluid homeostasis. Fluid homeostasis is the interplay of fluid intake and absorption, fluid distribution, fluid excretion, and fluid loss
through abnormal routes.
, Fluid Excretion
● Normal: Controlled by HORMONES
○ Urinary tract → URINE (Largest amount of fluid excreted)
○ Bowels → Fecal matter + Normal bowel function
○ Skin → Sweat + Insensible perspiration (Always occurring)
○ Lungs → As a person exhales
■ Antidiuretic Hormone (ADH): Increases blood pressure by regulating fluid loss
● Posterior Pituitary
● Stimuli: Increased osmolality (extracellular fluid), decreased circulating fluid volume, pain, nausea,
stress
● REABSORPTION → WATER → DILUTES BLOOD/Body fluids
○ Decreases Urine Volume → Increases Urine Concentration → Decreases Fluid Excretion
■ Aldosterone: Steroid hormone of the adrenal gland (above kidney) → SODIUM CONSERVATION
● Stimuli: Angiotensin II + Increased potassium ions in plasma
● Renal tubules reabsorb Sodium + Water → SALINE → Expanding the extracellular fluid volume
○ “Where salt goes, water flows.”
○ Decreases fluid excretion
○ ↑ Aldosterone = Urine volume → Smaller
○ ↓ Aldosterone = Urine volume → Larger
■ ADH = “Free Water” hormone → Dilution // Aldosterone = “Salt Water” Hormone → Expansion
■ Atrial Natriuretic Peptide (ANP): Regulates blood pressure through activity in the kidney that promotes the
excretion of water and sodium
● Cardiac ATRIAL cells → Released when ATRIA = Stretched
■ Brain Natriuretic Peptide (BNP): Marker of fluid overload in patients (CV)
● Diastolic pressure increases abnormally (Heart failure) → Released (VENTRICULAR cells)
■ ANP + BNP → Natriuresis (Sodium excretion in the urine) → Water excretion (Following Salt) = Saline
excretion (Maintain osmotic balance + Reduce blood pressure)
■ Renal Prostaglandins: Increase renal blood flow + filtration
■ Renal Sympathetic Nerves: Play a role in blood pressure
■ Urine volume → Dependent on adequate blood pressure to perfuse the kidneys and on the glomerular filtration
rate
● Abnormal Routes
○ Wounds, Burns, Open areas on skin, Fistulas (Drainage)
○ Hemorrhage (Bleeding)
○ GI → Diarrhea + Emesis (Vomiting)
○ GI Tubes (NG Suction)
○ Injury
○ Paracentesis
● INCREASED FLUID INTAKE = INCREASED FLUID EXCRETION = INCREASED URINE VOLUME
○ (Large volume of DILUTE urine)
● DECREASED FLUID INTAKE (or Abnormal Loss) = DECREASED FLUID EXCRETION
○ (Small volume of CONCENTRATED urine) + Thirst may cause an increase in fluid intake
Key Points:
● Fluid Homeostasis: Fluid Intake + Absorption, Fluid Distribution, Fluid Excretion // Fluid Loss through Abnormal Routes
○ Important regulators of fluid intake = Habit and Thirst
● Risk for fluid imbalance = Individuals who are unable to control their own fluid intake
○ Receiving fluids intravenously (IV), Immobile, Unconscious patients
● Fluid (Water/Particles) moves between Vascular → Interstitial (Extracellular) → FILTRATION (Capillaries)
○ Capillary hydrostatic pressure = Primary force promoting fluid movement → Capillaries (Vascular) → Interstitial fluid
○ Plasma colloid osmotic pressure = Primary force that causes interstitial fluid → Capillaries (Vascular)
● Water moves in and out of cells by OSMOSIS
○ Electrolytes do not move freely across cell membranes → Transported by membrane channels/carriers
● Healthy kidneys adjust fluid excretion in response to blood pressure and several hormones
○ Aldosterone → Kidneys → Conserve Saline (salt and water) → Expands extracellular fluid volume
○ ANP and BNP → Saline excretion
○ Antidiuretic hormone (ADH) → Kidneys → Retain Water → Concentrating Urine + Diluting Body fluids
○ Important indicators of body fluid balance = Urine volume and Concentration
