List the 4 components of the urinary system
- Kidney
- Ureter
- Bladder
- Urethra
Anatomy of the kidney
- Vascular supply
- Efferent arteriole → outgoing blood
- Afferent arteriole → incoming blood
- Peritubular capillaries
- Vasa recta
Anatomy of the kidney
- Location of the medulla
- Loops of Henle
- Collecting ducts
Anatomy of the kidney
- Location of cortex
Where glomeruli are on outside edge
Anatomy of the kidney
- Location of the calices
Where the collecting ducts dump
Anatomy of the kidney
- Location of the renal pelvis
Trunk that will empty into the ureter
Microscopic anatomy of the nephron in anatomical order starting w/ the glomerulus and ending w/ collecting ducts
Afferent arteriole → efferent arteriole → blood filtered in glomerulus → proximal convoluted tubules → loops of Henle → distal convoluted tubules → collecting ducts
List the 3 functions of the kidney
- Excretion
- Homeostatic regulation
- Endocrine
List 2 plasma constituents that are not normally filtered through the glomerulus
- High molecular weight plasma proteins
- Cells
Rate in mL/minute that substances are filtered through the kidney’s glomeruli
GFR
Normal GFR in mL/minute
125-130 mL/min
Two clinical uses for the measurement of GFR
- Measure of number of functioning nephrons
- Sensitive and specific marker of changes in overall renal function
Three forces which determine normal glomerular filtration pressure
- Hydrostatic of blood
- Fluid pressure (glomerular hydrostatic pressure)
- Plasma oncotic pressure (colloid)
Net movement of substance against a concentration or electrical gradient requires energy expenditure
Mechanism of active tuberular absorption
Substance moves by simple diffusion as a result of a concentration or electrical gradient; no energy expenditure
Mechanism of passive tuberular absorption
List 10 substances reabsorbed in teh PCT
- Na+
- HCO3-
- Glucose
- Amino acids
- Proteins
- Phosphate
- Sulfate
- Mg2+
- Ca2+
- Uric acid
What is the specific renal threshold for glucose?
About 160 mg/dL
Countercurrent mechanism
- Major purpose
Purpose is to remove water from the filtrate on the way down the descending loop making it very salty at the bottom of the loop. Then, on the way up the ascending loop, active reabsorption of sodium and chloride ions occurs. OR like a water heater, allows for the reabsorption of H2O, Na, Cl, and urea with less energy expenditure
Countercurrent mechanism
- Location in the nephron
Loops of Henle
Countercurrent mechanism
- Differentiation in the histology of the descending and ascending limbs
- Descending: permeable to water so there is passive water and urea reabsorption
- Ascending: impermeable to water so there is active reabsorption of sodium and chloride
Countercurrent mechanism
- Movement of Na, Cl, urea, and H2O in or out of the renal tubules
- Sodium: out
- Chloride: out
- Urea: in
- Water: out
List 3 distinct regulatory functions of the DCT
Responisble for acid-base, water, and electrolyte balance control in the nephron so…
- Sodium reabsorption
- Potassium secretion
List 4 substances that are normally reabsorbed in the DCT?
Reabsorption of sodium, chloride, bicarbonate, and water
List 4 substances that are normaly secreted in the DCT
Secretion of potassium, hydrogen ions, ammonium, and uric acid
Specific hormone that exerts its effect on the DCT
Aldosterone
What substances are normally reabsorbed in the collecting ducts?
↑ or ↓ water adsorption is controlled here
What hormone exerts its effect on the collecting duct?
Antidiuretic hormone (ADH/vasopressin)
- Presence causes water reabsorption by widening pores
- Absence causes ↓ water readsorption
Juxtaglomerular apparatus (JGA) - Function
Regulated the function of each nephron
Juxtaglomerular apparatus (JGA) - Location
Found b/w the vascular pole of the glomerulus and the returning DCT of the same nephron
Juxtaglomerular apparatus (JGA) - Specific functions of granular cells
Secrete renin, which is an enzyme that is the starting point for the renin-angiotensin-aldosterone system (RAAS)
Juxtaglomerular apparatus (JGA) - Specific functions of macula densa cells
Regulate [Na] and [Cl] by sensing (NaCl) in the DCT
Juxtaglomerular apparatus (JGA) - Specific functions of mesangial cells
Receive stimulation from sympathetic nervous system to modulate actions of the JGA
Juxtaglomerular apparatus (JGA) - Importance of its location
Location is critical to its function in regulating renal blood flow and the glomerular filtration rate
3 basic procedures involved in renal excretion
- Filtration
- Reabsorption
- Secretion
In FILTRATION, are substances being conserved in the blood or are they excreted in the urine?
Going into forming urine from blood
In REABSORPTION, are substances being conserved in the blood or are they excreted in the urine?
Capillary system taking substance into the blood
In SECRETION, are substances being conserved in the blood or are they excreted in the urine?
From blood to the secretion
Hypothalamic and ADH regulation of water balance
- 3 stimuli for the water output area of the hypothalamus
- ↑ in extracellular water osmolarity
- ↑ in angiotensin II
- ↓ in baroreceptor and distension receptor activity
Hypothalamic and ADH regulation of water balance
- Primary stimulus for ADH release
High blood pressure osmolarity
Hypothalamic and ADH regulation of water balance
- Effect that ADH causes on the collecting ducts of the kidney
↑ pore size → absorb more water
Sodium regulation
- Renal handling of sodium in every major portion of the nephron
Sodium is exchanged w/ H+ all along the nephron
Sodium regulation
- Effect of the renin-angiotensin-aldosterone system
↑ Na+ reabsorption
Sodium regulation
- Where aldosterone exerts its effect in the nephron
Control regulation in DCT
Renin-angiotensin-aldosterone system
- Specific site in the nephron where renin is produced
Juxtaglomerular apparatus
Renin-angiotensin-aldosterone system
- 3 specific stimuli for renin release
- ↓ renal perfusion pressure
- Sympathetic nerve stimulation
- ↓ [Na] in DCT
Renin-angiotensin-aldosterone system
- Biochemical conversions from angiotensinogen to angiotensin II
- Renin converts angiotensinogen to angiotensin I in the liver
- Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II in the lungs
Renin-angiotensin-aldosterone system
- Organs in which the conversion of angiotensinogen to angiotensin II occurs
Liver to the lung
Renin-angiotensin-aldosterone system
- 4 physiological effects of angiotensin II
- Most powerful vasoconstrictor
- Affects water intake of hypothalamus
- Affects water output and causes the release of ADH from hypothalamus
- Causes aldosterone release from adrenal cortex
Renin-angiotensin-aldosterone system
- Effect of aldosterone on serum sodium and potassium levels
DCT retains more sodium and secretes potassium (therefore ↓ potassium)
Effect of BNP on sodium levels in the blood
BNP causes Na+ excretion
The condition that may be assessed via BNP measurements
CHF
The two substances that the kidney regulates to maintain acid-base balance and whether these substances are normally reabsorbed or secreted
- Reabsorption of bicarbonate
- Secretion of hydrogen ions
4 renal mechanisms by which the kidney maintains acid-base balance and the site in the nephron where these occur
- React w/ filtered bicarbonate ions
- React w/ filtered buffers to form titrateable acids
- Reacts w/ secreted ammonia to form ammonium ions
- Exchange w/ Na+
Renal regulation of H+ and [HCO3-] according to
- Mechanism for the reaction of H+ w/ filtered HCO3-
?
Renal regulation of H+ and [HCO3-] according to
- Mechanism for the reaction of H+ w/ phosphate buffers
?
Renal regulation of H+ and [HCO3-] according to
- Mechanism for the reaction of H+ w/ secreted ammonia
?
Renal regulation of H+ and [HCO3-] according to
- Mechanism for free H+ excretion
?
List the 3 important hormonal functions of the kidney
- Vitamin D metabolism
- EPO production and release
- Renin production in JGA that results in hormone release
Microscopic structure which regulates the function of each nephron; named for its proximity to the glomerulus
JGA
An enzyme that is the starting point for the RAAS
Renin
Responsible for filtration of the blood; it’s selective permeability does not allow large molecular weight compounds to be filtered
Glomerulus
