Chapter 26 Flashcards
Organs of urinary system
- Kidneys
- Ureters
- Urinary bladder
- Urethera
Function of urinary system
Maintains homeostasis by managing the volume and composition of fluid reservoirs, primarily blood
Function of kidneys
Eliminates liquid waste (urea) and help maintain homeostasis
Function of ureters
Carry urine from the kidneys to the bladder
Function of urinary bladder
Stores urine
Function of urethra
Allows urine to pass outside body
Nephron
Functional units that make kidneys work the way they do
How urinary system affects circulatory system
Because of erythropoietin production
How kidneys are involved in homeostatic regulatory functions
- Blood ionic composition
- Blood pH
- Blood volume
- BP
- Blood osmolarity
- Hormones
Main importance of kidneys
Regulating blood volume and blood pressure
Renal hilum
Where vessels, nerves, and ureters pass
Structures that enter the hilum
- Renal artery
- Renal vein
- Ureter
- Nerves
- Lymphatics
3 layers of connective tissue surrounding the kidney
- Renal fascia: anchors to other structures
- Adipose capsule: protects/anchors
- Renal capsule: continuous with ureter
Where nephrons are located
Renal pyramids
Number of nephrons in human body
~ 2 mil, 1 mil in each kidney
Percent of resting cardiac output kidneys receive
20%-25%
Glomerular capillaries
Knot/cluster of capillaries inside renal corpuscle
Main functions of nephron and kidney
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Counter current multiplication
Forms and maintains vertical water osmotic gradient
Effect of hormones on kidney function
Renin released, activates enzyme causing blood vessels to constrict, increase BP, releasing diff hormone/enzyme
Glomerular filtration rate (GFR)
Estimates how much blood passes through the glomeruli each minute/fluid going through kidneys?
How blood pressure and GFR are related
Increased blood volume and increased blood pressure will increase GFR
Function of macula densa
Maintenance of body fluid, electrolyte homeostasis, and blood pressure
Obligatory water reabsorption
Reabsorption of water in the early sections of the nephron regardless of the state of the body’s hydration
Function of juxtaglomerular (JGA) in blood pressure control
Helps control blood pressure in kidneys in conjunction with ANS ; consists of macula densa and juxtaglomerular cells
Parts of nephron
- Renal corpuscle: filters blood
- Renal tubule: filtrate is altered by absorption and secretion
Flow of fluid through a nephron
- Glomerular (Bowman’s) capsule
- Proximal convoluted tubule
- Descending limb of the loop of Henle
- Thin ascending limb of the loop of Henle
- Thick ascending limb of loop of Henle
- Distal convoluted tubule
Differences in two types of nephrons
Cortical nephrons
- Have a glomerulus located nearer to the outer parts of the cortex
- Loops of Henle are short
Juxtamedullary nephrons
- Have a glomerulus near the junction of the cortex and medulla
- Loops of Henle penetrate deep into the medulla
Two parts of renal corpuscle
Glomerulus and glomerular (Bowman’s) capsule
Podocytes
Wrap around capillaries
What glomerular filtration membrane consists of
- Glomerular endothelial cell layer with fenestrations
- Basement membrane of the glomerulus
- Slit membrane b/w podocytes
What can pass through the layers of glomerular filtration membranes
Water and ions
Can’t pass through the layers of filtration membrane
Molecules, glucose
Two types of nephrons
Cortical and juxtamedullary
More common type of nephron
Cortical
Type of nephron that produces more concentrated urine
Juxtamedullary
Relationship between three processes involved in urine formation
Excretion of solute = Glomerular filtration + secretion - reabsorption
Structural differences in two types of nephrons
Juxtamedullary has thick and thin long nephron loop
Cortical has short loops of Henle that extend into outer region of medulla
Juxtaglomerular apparatus (JGA)
Consists of macula densa and juxtaglomeruler cells, helps to control blood pressure in kidneys
Average number of liters of blood in body
5 L
Average amount of urine formed in a day
1.5 - 2 L
Number of liters of blood that can be filtered a day
180 L (filtering the same 5 L)
What body producing 1.5 - 2 L of urine a day indicates
Rest of fluid is being reabsorbed into blood
Glomerular filtration rate (GFR)
Amount of filtrate formed by both kidneys each minute
Problem that occurs if GFR is too high/low
Substances pass too quickly and are not reabsorbed
Nearly all reabsorbed except some waste products
Two areas that fluid moving from one area to another depends on
Glomerular capillaries and surrounding capsule
3 pressures involved in process of glomerular filtration
- Glomerular blood hydrostatic pressure (GBHP): forces fluid from glomerulus into capsule
- Capsular hydrostatic pressure (CHP): forces fluid into glomerulus from capsule
- Blood colloid osmotic pressure (BCOP): pulls fluid into the glomerulus from the capsule
How to calculate net filtration pressure (NFP)
NFP = GBHP - CHP - BCOP
Included in glomerular filtrate of renal filtration
Water, nitrogenous waste, nutrients
Effect that increase/decrease in blood pressure has on GFR
Directly correlated, increase = increase, decrease = decrease
Adjusting these 2 things will regulate GFR
Amount of blood flowing into the glomerulus, surface area of glomerulus
How adjustments that regulate GFR can be made
- Renal autoregulation
- Neural regulation
- Hormonal regulation
Paracellular reabsorption vs. transcellular reabsorption
Passive fluid leakage b/w cells
vs.
Directly through tubular cells
Obligatory water reabsorption vs. facultative water reabsorption
Water follows solutes that are reabsorbed
vs.
Regulated by ADH
Where majority of reabsorption occurs in tubule
Proximal convoluted tube (PCT)
Substances reabsorbed in PCT
Water, ions, glucose, amino acids
Reabsorbed in descending/ascending limb of loop of Henle
Water, little obligatory water reabsorption
Part of tubule impermeable to water
ascending limb
Reabsorbed in early DCT
NaCl symporters reabsorb ions, PTH stimulates reabsorption of Ca
Reabsorbed in late DCT and collecting duct
Principle cells –> Na
Aquaporin 2 –> Water
Intercalated cells –> K, HCO3, H
Osmolarity of both blood and initial glomerular filtrate
300 mOsm/L
- but as filtrate passes through nephron tubule, its osmolarity changes b/c conc. gradient in interstitial fluid in medulla
How osmolarity of filtrate changes
Incr. in descending limb of loop
Decr. in ascending limb of loop
Decr. more in collecting duct
Why osmolarity of filtrate changes
Water is reabsorbed from descending limb of loop, salt is reabsorbed from ascending limb of loop, but is relatively impermeable to water, so solutes leave the ascending limb, but water doesn’t
How osmolarity of interstital fluid of medulla changes as you go deeper into medulla
Increases
How juxtamedullary nephrons affect surface area for water reabsorption
Provide much more, produces more concentrated urine
What regulation of osmolarity of body fluids depends on
- Formation of medullary osmotic gradient
- Amount of ADH in collecting duct
Allow for formation of concentrated urine
What production of medullary gradient depends on
- Differences in water and solute permeability and reabsorption in diff. limbs of the loop
- Urea cycling in the medulla
- Countercurrent exchange in vasa recta
Vasa recta and function
Long, hairpin shaped blood vessels that run parallel to loop of Henle
* Maintain concentration gradient by adding/removing solute and water from medulla
Urea cycling
???
Importance of urea recycling
Greatly incr. medullary osmotic gradient values to final amounts
2 solutes that contribute the most to high osmolarity of the interstitial fluid of the medulla
Sodium chloride, medulla
Ureter function
Transport tubes that move urine from kidneys to urinary bladder
Bladder
Temporarily store urine until convenient to discharge from body
Urethra
Drainage tube that transports stored urine from body
Micturition
Urinating
Difference in urethra in men and women
Men: 5x longer, 3 segments, common duct for urinary and genital systems
Women: One short tube, two different systems for urinary and genitals
