A&P 2 Test 4

What is the main function of the urinary system?

Rid the body of metabolic waste

What are the 4 functions of the kidneys?

Filter blood to excrete bad things, regulate blood factors, secrete EPO, regulate calcium

What things do the kidneys excrete?

Metabolic waste, drugs, hormones

What factors of the blood do the Kidneys regulate?

Volume, pressure, osmolarity, acid/base balance

How do the kidneys regulate calcium?

Calcitriol synthesis

Where are the Kidneys located?

Posterior abdominal wall

Which vertebrae do the Kidneys sit in between?

T12 and L3

What is the outer layer of the kidneys called?

Cortex

What is the layer deep to the cortex in the kidneys?

Medulla

What is the function of the ureters?

Collect urine and sent to bladder

What is peristalsis?

Wave of contractions that send urine to bladder

What is the functional unit of the kidney

Nephron

How many nephrons are there in a kidney?

1.2 million

What are the three functions of a nephron?

Filter blood, reabsorb useful ions, form urine

What are the two parts of the nephron?

Renal corpuscle and tubule

What is the glomerulus?

Cluster of capillaries found at entry point of nephron

What does the glomerulus do?

Delivers blood to be filtered

What is the material filtered from the capillaries called?

Filtrate

Where does the filtrate go after the glomerulus?

Renal tubule

What does the glomerular capsule do?

Contains the glomerulus

What is the main function of the renal tubule?

Form urine from filtrate

What two things does the renal tubule cross between?

Cortex and medulla

What does the proximal convoluted tubule do?

Receives filtrate from glomerulus

Where is the PCT located?

Cortex

What does the nephron loop do?

Receives filtrate from PCT

What does the nephron loop descend into?

Medulla

What does the distal convoluted tubule do?

Receives filtrate from nephron loop

Where is the DCT located?

In cortex

Where does urine undergo the last step of being formed from filtrate?

DCT

What does the collecting duct recieve?

Receives urine from many nephrons

What does the collecting duct deliver?

Delivers urine out of nephron to renal sinus

What are the three stages of urine formation?

Glomerular filtration, tubular reabsorption, tubular secretion

Where does glomerular filtration happen?

Renal corpuscle

Where does tubular reabsorption and secretion happen?

Renal tubule

Is glomerular hydrostatic pressure moving fluid in or out of the capillary?

Out

Is blood colloid osmotic pressure moving fluid in or out of the capillary?

In

Is capsular hydrostatic pressure moving blood in or out of the capillary?

In

What is the main purpose of glomerular filtration?

Filter blood to form filtrate

What is the main purpose of Tubular reabsorption?

Remove solutes and water from filtrate and return it to the blood

What is the purpose of tubular secretion?

Remove additional substances from the blood and add to filtrate

What is filtrate composed of?

Glucose, amino acids, small proteins, fatty acids, ions, water

What size particles remain in the capillaries during glomerular filtration?

Large

Do RBCs remain in the capillaries or get filtered during glomerular filtration?

Remain in capillaries

What are the layers that make up the filtration barrier?

Endothelium of capillaries, podocytes, fused basement membrane

What is a key feature of the endothelium of capillaries?

Fenestrated capillaries

What are fenestrated capillaries?

Capillareis with small holes in their endothelial cells

What are podocytes?

Cells that wrap around the capillary

What are pedicels?

Extensions of podocytes that interdigitate with adjacent podocytes

What is the fused basement membrane between in the glomerular filtration membrane?

Podocytes and endothelium

Why does filtration happen in glomerular filtration?

Hydrostatic pressure in capillaries is greater than pressure in glomerular capsule

Which glomerular filtration pressure is the most adjustable?

Glomerular blood hydrostatic pressure

What is the definition of glomerular filtration rate (GFR)?

Amount of filtrate formed per minute by all nephrons in both kidneys

What is the typical range for GFR in mL/min?

90-120

How much filtrate is created per day in liters?

180

What percentage of filtrate is reabsorbed by the blood?

99%

How much urine is typically excreted per day in liters?

1-2

What happens if GFR is too high?

Fluid flows too quickly through renal tubule

Why is a high GFR bad?

Reabsorption of necessary ions, water and proteins is inhibited

Why is low GFR bad?

Wastes not removed efficiently from blood

What regulates GFR?

Glomerular blood hydrostatic pressure

What is the relationship between GFR and GBHP?

Higher GBHP the higher GFR

What are the three homeostatic mechanisms that regulate GFR?

Renal autoregulation, sympathetic nervous system, hormonal control

How does renal autoregulation work?

Nephrons adjust blood flow with no external influence through vasoconstriction and vasodilation of the afferent and efferent arterioles

Would vasoconstriction of the afferent arteriole increase or decrease GFR?

Decrease

Would vasodilation of the afferent arteriole increase or decrease GFR?

Increase

Would vasoconstriction of the efferent arteriole increase or decrease GFR?

Increase

Would vasodilation of the efferent arteriole increase or decrease GFR?

Decrease

What are the two mechanisms that drive renal autoregulation?

Myogenic mechanism and tubuloglomerular feedback

What is the main purpose of the myogenic mechanism?

Adjust the diameter of afferent arterioles based on blood pressure

What does the myogenic mechanism do if the systemic blood pressure is high?

Constricts afferent arterioles to stop too much blood from entering glomerulus

What does the myogenic mechanism do if the systemic blood pressure is low?

Dilates afferent arterioles to allow for enough blood to enter the glomerulus

What is the main purpose of the tubuloglomerular feedback?

Recieve feedback on ion concentration in filtrate in renal tubule and adjust filtration rate

What does the tubuloglomerular feedback do if the GFR is high?

Puts more NaCl in filtrate

Why does the tubuloglomerular feedback put NaCl in the filtrate?

So that sensory cells in nephron loop can sense it

What are the sensory cells in the nephron loop?

Macula densa

What happens when the NaCl excreted by the tubuloglomerular feedback reaches the granular cells?

Constricts afferent arterioles which reduces blood flow and slows GFR

What type of nerve fibers innervate the renal blood vessels?

Sympathetic

When do renal arteries constrict?

Stress and exercise

What does constriction of the renal arteries do?

Reduces GFR and urine output while redirecting blood from kidneys to vital organs

What is the definition of reabsorption in regards to a nephron?

Removal of useful molecules and ions from filtrate and send them back to the blood

In the PCT what percentage of filtrate is reabsorbed?

65%

Where is PCT filtrate reabsorbed?

Peritubular capillaries

What percentage of nephron loop filtrate is reabsorbed?

25%

Where is the nephron loop filtrate reabsorbed?

Vasa recta

What is reabsorbed due to hormonal influences in the DCT?

water, Na, Cl

Where is water, Na, and Cl reabsorbed in the DCT?

Peritubular capillaries

What is the definition of secretion?

Removal of additional molecules and ions from capillaries into tubule

Can things be secreted into the glomerulus?

No

What percent of sodium is reabsorbed in the PCT?

70%

What percent of glucose, amino acids, proteins, and vitamins are reabsorbed in PCT?

100%

What drives osmosis in the PCT?

Sodium

Is there high or low concentrations of sodium in PCT filtrate?

High

Is there high or low concentration of sodium in epithelial cells lining PCT?

Low

What are the two symports in the PCT?

Sodium, glucose and sodium amino acids

Which way to the symports in the PCT move things?

Into blood

What does the antiport move in the PCT?

Sodium into blood and hydrogen out

What happens at the basal section of epithelial cells in the PCT?

Sodium potassium pump keeps sodium from building up in the cell and then sodium diffuses into blood

What is solvent drag?

When water diffuses and brings many other ions along with it

Where does tubular secretion happen?

Throughout renal tubule

What are the three big purposes of tubular secretion?

Acid base balance, waste removal, drug removal