Urinary System physiology

What are the 11 components of the urine?

Water

Urea

Uric acid

Creatinine

Ammonia

Sodium

Potassium

Chlorides

Phosphates

Sulphites

Oxalates

What are the three steps of urine formation?

Filtration

Selective reabsorption

Secretion

What is the structure of the afferent arteriole?

Large diameter to increase blood pressure in capillaries

What is the function of the afferent arteriole?

Drives filtration outwards through capillary walls into capsule

What is the structure of the efferent arteriole?

Divides into peritubular capillary network which wraps around the rest of the nephron

What is the function of the peritubular capillary network?

Allows exchange of substances between the filtrate and the bloodstream

What is filtration?

Passage of water and other small molecules through the semipermeable walls of the glomerulus and glomerulus capsule

Why does filtration take place?

Difference between blood pressure in the glomerulus and filtrate pressure in glomerular capsule

What is the function of glomerular hydrostatic pressure?

Pushes fluid out of the blood into the nephron

What is the function of the blood osmotic pressure?

Pulls fluid back into blood

What is capsular hydrostatic pressure?

Pressure from fluid already in the capsule

What is the glomerular filtrate rate?

Volume of filtrate formed by both kidneys each minute

What is a healthy adult GFR?

125 mL/min

What is auto regulation?

Mechanism where renal blood pressure is maintained across systolic blood pressure

What controls the renal auto regulation?

Smooth muscle in renal blood vessel independent of nervous control

What are the two sections of the loop of henle?

Descending limb

Ascending limb

What is the function of descending limb?

Reabsorbs water

What is the function of the ascending limb?

Reabsorbs sodium and chloride

What is the function of the distal convoluted tubule?

Reabsorbs electrolytes, diluting the filtrate

What is the function of the collecting duct?

Adjusts water reabsorption based on body needs using antidiuretic hormone

What are the four hormones involved in selective reabsorption?

Parathyroid

Antiduretic

Aldosterone

Atrial natriuretic peptide

What is the function of the parathyroid hormone?

Regulates calcium and phosphate reabsorption

What is the function of the antidiuretic hormone?

Increases permeability of distal convoluted tubules and collecting ducts to water

What are the two functions of the aldosterone hormone?

Increases sodium and water reabsorption

Increases potassium excretion

What are the two functions of the atrial natriuretic peptide hormone?

Decreases sodium and water reabsorption in the proximal convoluted tubules and collecting ducts

Inhibits ADH and aldosterone

What are the three ways electrolyte levels are balanced?

Sweating

Digestive loss

RAAS system

What does the RAAS system stand for?

Renin Angiotensin Aldosterone System

How does renin raise blood pressure when triggered?

Renin converts angiotensinogen to angiotensin 1

ACE converts angiotensin 1 to angiotensin 2

How does angiotensin 2 raise blood pressure?

Stimulates aldosterone which increases sodium and water reabsorption

How does negative feedback effect renin?

Reduces renin as blood volume rises

What two hormones control calcium balance and how?

Parathyroid hormone raises calcium

Calcitonin lowers calcium

What are the three substances that combine with hydrogen ions and what are the products?

Bicarbonate to make carbonic acid

Ammonia to make ammonium

Phosphate to make dehydrogenase phosphate

What are the three steps of the process of micturition?

Urine accumulation activates stretch receptors in bladder

Impulses generated to spinal cord and micturition reflex initiated

Stimulates involuntary contraction of dextrusor and relaxation of internal urethral sphincter expelling urine