uriniary system Flashcards
What are the three main functions of the Urinary System?
- Excretion: removal of organic wastes from body fluids
- Elimination: discharge of waste products
- Homeostatic regulation: of blood plasma volume and solute concentration
What organs are involved in the urinary tract?
- Ureters
- Urinary bladder
- Urethra
What is the process of eliminating urine called?
Urination or Micturition
How does the urinary system help regulate blood pressure?
By adjusting volume of water lost in urine and releasing erythropoietin and renin
What ions does the urinary system regulate?
- Sodium
- Potassium
- Chloride
- Calcium (through synthesis of calcitriol)
What are the two functional components of a nephron?
- Vascular component
- Tubular component
How much blood do the kidneys receive each minute?
~1200 ml
What is the role of the renal artery?
To supply blood to the kidneys
What structure filters blood in the kidneys?
Glomerulus
What is the juxtaglomerular apparatus?
A structure associated with renal capillaries and involved in regulating blood pressure and filtration rate
What is the first part of the nephron’s tubule?
Proximal convoluted tubule (PCT)
What happens in the proximal convoluted tubule?
Active removal of ions and organic substrates, producing osmotic water flow out of tubular fluid
What is the function of the Loop of Henle?
To concentrate urine by reabsorbing water and ions
What is the final adjustment of tubular fluid composition made by?
DCT and Collecting Ducts
What determines final urine concentration?
Exposure to ADH (Antidiuretic Hormone)
What are the two types of nephrons?
- Cortical nephrons
- Juxtamedullary nephrons
Fill in the blank: The kidneys are covered in a _______.
tough fibrous capsule
True or False: The left kidney lies inferior to the right kidney.
False
What is the total number of nephrons in the kidneys?
About 2 million
What is the function of the vasa recta?
To absorb solutes and water reabsorbed by loop of Henle and the ducts
What does the efferent arteriole do?
Recombines glomerular capillaries and leads to peritubular capillaries
What is the renal pelvis?
The area where collecting ducts drain into, continuous with the ureter
How does the urinary system help stabilize blood pH?
By controlling loss of hydrogen ions and bicarbonate ions in urine
What is the average filtration rate of the kidneys?
~180 L/day (~120 ml/min)
What is the normal range for glomerular filtration rate (GFR)?
~120-125 ml/min or 180 l/day
What is the significance of a high turnover in glomerular filtration?
Essential to clear blood of toxic or waste materials
How often is the entire extracellular fluid exposed to filtration?
Around 10 times a day
What does eGFR stand for?
Estimated Glomerular Filtration Rate
What are important factors affecting GFR?
- Autoregulation
- Renin-Angiotensin-Aldosterone System (RAAS)
- Pathologies
What happens to GFR when it becomes dependent on arterial pressure?
It becomes problematic
What two types of pressure regulate GFR?
- Hydrostatic pressure
- Oncotic pressure
What is tubulo-glomerular feedback?
A mechanism that regulates glomerular filtration rate
What is the role of the Renin-Angiotensin-Aldosterone System (RAAS)?
Control of renal blood flow and glomerular filtration
Why is it important to keep blood flow and GFR within narrow limits?
To preserve perfusion in emergency situations like hypotensive shock
What protects glomerular capillaries from increases in blood pressure?
Regulation independent of renal nerves and circulating hormones
What is the myogenic response?
A response that helps regulate blood flow and GFR
What favors ultrafiltration in the glomerular capillaries?
Hydrostatic pressure in capillaries
What opposes movement of water and solutes across the capillary wall?
- Oncotic pressure
- Hydrostatic pressure in Bowman’s capsule
What factors regulate glomerular filtration?
- Hydrostatic pressure gradient
- Oncotic pressure exerted by plasma proteins
- Capillary wall structure
Fill in the blank: Hydrostatic pressure in Bowman’s capsule _______ filtration into the renal tubule.
opposes
What happens to GFR when the afferent arteriole relaxes?
Increased GFR due to increased blood flow
What effect does constriction of the efferent arteriole have on GFR?
Increases GFR due to increased hydrostatic pressure
Name one substance that increases hydrostatic pressure in the afferent arteriole.
Prostaglandins
What is the effect of nitric oxide on glomerular filtration?
Increases blood flow into glomerular capillaries
What is the effect of angiotensin II on GFR?
Constriction of efferent arteriole increases GFR
True or False: A decrease in hydrostatic pressure within the glomerular capillaries leads to increased GFR.
False
What role does atrial natriuretic peptide (ANP) play in GFR regulation?
Increases hydrostatic pressure in the afferent arteriole
What is tubulo-glomerular feedback’s role in kidney function?
Regulates GFR based on the flow rate of filtrate
What is the primary function of the renal tubule?
Biological plumbing
What are the main components of renal tubule function?
- Pressure
- Flow
- Tubing
- Filters
- Reservoirs
- Control Systems
What percentage of ions in filtrate is reabsorbed in the proximal tubule?
100% of ions in filtrate
What is the sodium reabsorption rate in the proximal tubule?
~60% of Na reabsorbed
How does water follow sodium in the proximal tubule?
Water follows the Na by passive diffusion via paracellular and cellular pathways
What is the sodium reabsorption rate in the thick ascending limb of Henle’s loop?
~15-25% of Na reabsorbed
Is the thick ascending limb of Henle’s loop permeable to water?
No, it is impermeable to water
What is the Na/K/Cl cotransporter in the thick ascending limb responsible for?
Electroneutral transport of 1 Na+, 1 K+, and 2 Cl-
What role does the Na-H exchanger play in the thick ascending limb?
Coupled to H+ transport, affecting pH
What is the function of the Na-K pump in the thick ascending limb?
Maintains Na+ gradient for reabsorption
What is the sodium reabsorption mechanism in the distal convoluted tubule?
Transcellular via Na/Cl cotransporter and Na-K pump
What is the effect of Na reabsorption and counter current flow in the nephron?
Produces a hyper-osmotic area
What is the osmotic gradient within the renal medulla used for?
Allows for the production of dilute urine (~150 mOsm/l) and concentrated urine (~1200 mOsm/l)
How does vasopressin affect water reabsorption?
Upregulates water permeability in the distal tubule
What is the primary mechanism of glucose reabsorption in the kidneys?
Na/glucose transporter via secondary active transport
What are the types of glucose transporters in the proximal tubule?
- SGLT2 (early proximal)
- SGLT1 (late proximal)
- GLUT2 (basolateral early)
- GLUT1 (basolateral late)
What is the absorption mechanism for urea in the kidneys?
- Paracellular absorption in proximal tubule
- Urea transporter UT2 in thin descending limb
- Urea transporter UT1 reabsorbs in collecting duct
- Urea transporter UT4 facilitates diffusion
What is the absorption rate of amino acids in the proximal tubule?
99% reabsorbed
What is the absorption mechanism for calcium in the proximal tubule?
- 80% paracellular (high Ca2+ permeability)
- 20% transcellular
What is the absorption rate of calcium in the thick ascending limb?
- 50% paracellular (lumen positive voltage)
- 50% transcellular
