Anatomy and Physiology Chapter 26 - Countercurrent Exchange

dilute vs. concentrated urine

dilute: when there is more water and less solute

• lower ADH > fewer aquaporins > less water reabsorbed > more dilute urine

concentrated: when there is more solute and less water

• higher ADH > more aquaporins > more water reabsorbed > more concentrated urine

diuretics

inhibit ADH or act on collecting duct

vasa recta

long, straight capillaries paralleling the nephron loops of juxtamedullary nephrons for countercurrent exchange; flows in the opposite direction of the nephron

urinalysis

use to diagnose certain diseases or disorders and check for durg usage

• specific gravity: density of the substance compared to the density of water

• untreated diabetes mellitus = glucose in urine

• proteinuria = preeclampsia, kidney inflammation, etc.

• some genetic conditions alter urine without causing harm such as beeturia and odor from eating asparagus

the flow of the urinary tract from structure to structure starting from kidneys

kidneys > minor calyx > major calyx > renal pelvis > ureters > urinary bladder > urethra

3 things about the urinary tract

• bladder has detrusor muscles to retain urine

• trigone is where ureters attach to prevent backflow

• male’s is longer than females

3 things about micturition

• peristaltic contractions move urine from kidneys to bladder

• opening to bladders is slit shape to prevent backflow

• internal and external urinary sphincters

4 things about fluid balance

1. water gains: digestive system for reabsorption

2. water losses: metabolism, urinary system, and integumentary system

3. water movement: between ECF and ICF affected by hydrostatic or net colloid osmotic pressure

4. fluid shifts: rapid water movement between ECF and ICF (hypertonic vs. hypotonic)

electrolyte balance

all lost = all gained affected by water concentrations

• main gainers: food and drink

• main losers: urine, sweat, and feces

*most common is Na+ and K+ is the most dangerous

5 minerals used for electrolyte balance

1. Na+

2. K+

3. Ca²+: bones, nervous system, and muscular system

4. Mg: in skeleton

5. PO₄³-: bone mineralization

4 electrolyte disorders

1. hyperatremia: too much water and less Na+

2. hypoatremia: too much Na+ and less water

3. hyperkalemia: more K+

4. hypokalemia: less K+

3 classes of acids

1. fixed acids: don’t leave solution and remain in body fluids until eliminated

2. metabolic acids: participants or by-products of metabolism

3. volatile acids: leave as gases in lungs (H2CO3 via water and CO2 interaction)

3 types of buffer systems

1. phosphate buffer system: buffer the pH of ICF and of urine

2. protein buffer system: regulation of pH in the ECF and ICF

   1. amino acids buffers

   2. hemoglobin buffer systems

3. carbonic acid-bicarbonate buffer system: freely reversible so change in any 1 component affects others, but can’t protect from increased or decreased CO2 pH changes

   1. lungs: controlled by breathing rate; exhaling CO2 removes acids, while retaining increases acid

   2. kidneys: reabsorb HCO3- ions to increase acid or excrete H+ in urine to decrease acid

acidosis vs. alkalosis

acidosis:

• respiratory acidosis: high CO2 that can’t be eliminated so low blood pH; solved by increasing respiration

• metabolic acidosis: increase in acid or low HCO3- and has impaired H+ secretion; solved like respiratory, but problem is overload of HCO3- with H+ metabolism

alkalosis:

• respiratory alkalosis: low CO2 raises pH; solved by hyperventilation

• metabolic alkalosis: decrease in acid or high HCO3- by vomiting; solved by decreasing breathing rates and increases HCO3- in urine