Exam 1 Flashcards
The urinary system is composed of four main components:
the kidneys, where urine is formed from the filtration of blood
the ureters that carry the urine to the bladder
the bladder that stores the urine produced
the urethra that delivers the urine for excretion outside the body
Primary function of kidneys
Removal of waste products
Acid-base balance
Retention of essential nutrients
Water, electrolyte balance
Hormone production
Production of vitamin D
Functional Unit of Kidney
Nephron
Two types of nephrons
Cortical nephrons
Juxtamedullary nephrons
This is controlled in the nephron by the following renal functions:
-renal blood flow
-glomerular filtration
-tubular reabsorption
-tubular secretion
% of the blood leaving the left ventricle of the heart enters the kidneys via the renal arteries.
20-25
Afferent arteriole means
Blood enters
Efferent arteriole means
Blood exits
the major exchanges of water and salts take place
Loop of Henle
Factors that influence filtration
Cellular structure of capillary walls
Hydrostatic pressure
Oncotic pressure
Renin-Angiotensin-Aldosterone system (RAAS)
Three cell layers of glomerulus
Capillary wall membrane
Basement membrane
Visceral epithelium
Shield of Negativity
cations and neutral pass thru repels anion plasma proteins
Hydrostatic pressure:
Pressure exerted by liquid = enhances filtration
Oncotic pressure:
Pressure exerted by the presence of unfiltered plasma proteins in glomerular capillaries
“the osmotic pressure of a substance in solution caused by the presence of colloids”
Systemic BP ↓
Less blood flowing into kidney
Toxic materials accumulate in blood
Systemic BP↑
Need to prevent over-filtration
Constrict afferent arteriole
How does the RAAS system work? Ex: Low sodium
Low sodium in systemic blood = less water retention within the circulatory system
Less water (retention) in systemic blood = low blood volume
Low blood volume = decrease in blood pressure
Macula densa senses changes in filtrate volume and and Na+ levels
Signals juxtaglomerular cells to release renin
As Na+ and BP increase, production of renin
decrease
High ADH↑
↑Increases permeability of tubule/collecting duct
↑in reabsorption of water
↓urine volume
More concentrated urine
Low ADH↓
↓permeability of tubule/duct
↓ in reabsorption of water
↑urine volume
More dilute urine
substances move from blood (peritubular capillaries) to the tubular filtrate (urine)
Tubular Secretion
Three major mechanisms in kidney to maintain blood pH homeostasis
Excretion of H+ ions in exchange for reabsorption of Bicarbonate (HCO3-)
Excretion of H+ ions combined with phosphate (HPO42-)
Excretion of H+ ions bound to ammonia (NH3) to produce ammonium ion (NH4+)
Glomerular filtration tests include
Inulin Clearance
Creatinine Clearance
Calculated Glomerular filtration
Tubular reabsorption tests include
Osmolarity
Free water clearance
Creatinine clearance test is used to:
Determine the extent of nephron damage in known cases of renal disease
Monitor the effectiveness of treatment
Determine the feasibility of administering medications
Specific Gravity
Measurement depends on number of particles present and density of the particles
Diabetes mellitus
high levels of sugar in the blood type 1,2
a defect in the pancreatic production of insulin or a defect in the function of insulin
Diabetes insipidus
disease where kidneys are unable to conserve water, rare
Two mechanisms:
1. Decreased ADH production
2. Inability of renal tubules to respond to ADH
a decrease in ADH production or a renal tubule dysfunction (inability to respond)
Ratio ≠ 3:1
renal tubules do not have functional ADH receptors/ unable to respond to ADH
Ratio = 3:1
decreased/inadequate ADH production
Urine Composition
95% water, 5% solutes
Factors that influence urine volume:
Fluid intake
Fluid loss from non-renal sources
Variations in the secretion of antidiuretic hormone
Kidney’s need to excrete increased amounts of dissolved solids
Refrigeration pro and con:
Pro: decreases bacterial growth
Con: can cause precipitation of amorphous materials- obscures microscopic sediment
Ideal Preservative Should:
Bactericidal
inhibit urease
preserve formed elements
not hinder chemical tests
Best specimen for routine screening tests
1st morning
