The Urinary System eliminates waste . . . Some waste products of urine = Nitrogenous wastes (from protein breakdown) Extra electrolytes Certain toxins and drugs

. . . to help regulate these very important things: Water balance Electrolytes Acid-base balance in the blood Blood pressure DIGESTIVE SYSTEM RESPIRATORY SYSTEM CARDIOVASCULAR SYSTEM URINARY SYSTEM water, solutes elimination of excess water, salts, wastes AND, kidneys also Manage RBC production (erythropoietin) Activate vitamin D

Organs of the Urinary System Kidneys – primary functional organs! Ureters – drain urine to bladder Urinary bladder – store urine Urethra – drain urine from body These are really just fancy plumbing

Kidneys are fairly well protected… Located against dorsal body wall Protected (somewhat) by lower ribs Anchored and protected (with fat) by 3 surrounding membranes Figure 15.1b

Kidney Features Renal hilum – indentation where ureters and blood vessels enter/exit kidney Adrenal glands on top

Regions of the Kidney Renal cortex—outer region Renal medulla—inside cortex Medullary pyramids and renal columns Renal pelvis—inner collecting tube (moves urine to ureters) Figure 15.2b

Participating… The major functional organs of the urinary system are the ____________ that are surrounded by ____ protective membranes. The primary functions of the urinary system include which of the following? Maintenance of blood pressure Maintenance of water and electrolyte balance Maintenance of acid-base balance Writing your name in the snow kidneys 3

Kidneys filter blood, i.e. control plasma composition 1/4th of blood supply passes through kidneys per minute! Renal artery = arterial blood supply (to be filtered) Renal vein = filtered blood drainage Filtration occurs across capillaries = glomerulus in between

Nephron =. functional unit of kidney, i. e Nephron = functional unit of kidney, i.e. actual site of urine formation Main structures of nephrons = Glomerulus – leaky knot of capillaries Renal tubule – collects urine, manages urine composition Glomerulus empties plasma into renal tubule, let’s take a closer look at making urine!

Step 1 of urine formation = glomerular filtration High pressure inside glomerulus forces plasma into glomerular capsule (a.k.a. Bowman’s capsule) Normally, cells too big to pass, just plasma Glomerular capsule = beginning of renal tubule Figure 15.3c

Step 2 = tubular reabsorption of valuable nutrients Immediately after filtration, nutrients move back into blood Capillaries surrounding renal tubule = peritubular capillaries H2O, glucose, amino acids, electrolytes re-enter blood Most reabsorption occurs across Proximal Convoluted Tubule (PCT)

Step 3 = tubular secretion Some waste must be actively transported into tubules Includes extra H+ (pH control)

Participating… The functional unit of the kidney is known as the __________ . The three steps of urine formation are: 1. ______________, 2. ______________, and 3. ___________. nephron filtration reabsorption secretion

What the?... Let’s review: Urine Formation Figure 15.4

Characteristics of Urine In 24 hours, 1.0 to 1.8 liters of urine are produced Solutes (unneeded waste) normally found in urine Na+, K+, H+ Urea, uric acid, creatinine Ammonia Bicarbonate ions 99% of filtrate gets back into blood via reabsorption!!

Abnormal Urine Constituents can help diagnose problems… Table 15.1

2 types of nephrons… Cortical nephrons – found in cortex, most common Juxtamedullary nephrons – penetrate the medulla via the Loop of Henle Loop of Henle helps reabsorb H2O

Collecting Ducts receive urine from multiple nephrons Deliver urine into calyces and renal pelvis Renal pelvis delivers urine to ureters

Ureters direct flow to Bladder Bladder emptied out by urethra Urethra is short in females, also close to anus = urinary tract infections This holds up to 1 liter! Urination (micturition) is controlled by voluntary external sphincter Figure 15.6

In males, urethra also part of reproductive system Urethra = passage for urine and semen in men Figure 15.7

Participating… The loop of Henle helps maximize the re-absorption of_______ . The urethra of ________ functions in both urinary and ______________ systems and is longer than the urethra of __________. water males reproductive females

Kidneys help control plasma composition of blood Remove nitrogenous waste (not reabsorbed) Maintain water and electrolyte balance Ensure proper pH

Maintaining Water and Electrolyte Balance Falling systemic blood pressure volume Reduced filtrate volume or solute content in renal tubules JG cells of kidneys (+) (+) = stimulates Renin-angiotension system Neural regulation (sympathetic nervous system effects) Effects of ADH release Renin Release Leads to Angiotensin II formed in blood Systemic arterioles Vasoconstriction Peripheral resistance Adrenal cortex Aldosterone Kidney tubules Na+ reabsorption (and H2O absorption) Blood volume Rising blood pressure Causes Results in Secretes Targets Releases Inhibits baroreceptors in blood vessels Sympathetic nervous system Hypothalamic osmoreceptors Posterior pituitary ADH (antidiuretic hormone) Collecting ducts of kidneys H2O reabsorption KEY: Osmoreceptors in hypothalmus detect water content of plasma… …stimulates thirst and release of ADH (antidiuretic hormone) = more H2O saved Figure 15.11

Maintaining Water and Electrolyte Balance Falling systemic blood pressure volume Reduced filtrate volume or solute content in renal tubules JG cells of kidneys (+) (+) = stimulates Renin-angiotension system Neural regulation (sympathetic nervous system effects) Effects of ADH release Renin Release Leads to Angiotensin II formed in blood Systemic arterioles Vasoconstriction Peripheral resistance Adrenal cortex Aldosterone Kidney tubules Na+ reabsorption (and H2O absorption) Blood volume Rising blood pressure Causes Results in Secretes Targets Releases Inhibits baroreceptors in blood vessels Sympathetic nervous system Hypothalamic osmoreceptors Posterior pituitary ADH (antidiuretic hormone) Collecting ducts of kidneys H2O reabsorption KEY: Low filtrate volume OR low b.p. = aldosterone release… …aldosterone  Na+ reabsorption and H2O retention Major BP control mechanism! Figure 15.11

Kidneys help control plasma composition of the blood Remove nitrogenous waste (not reabsorbed) Maintain water and electrolyte balance Ensure proper pH

Buffers = chemicals that prevent drastic changes in pH Bind to H+ when pH drops Release H+ when pH rises Bicarbonate (remember this?) = blood buffer H2CO3 HCO3- + H+ HCl + NaHCO3  H2CO3 + NaCl strong acid weak base weak acid salt NaOH + H2CO3  NaHCO3 + H2O strong base weak acid weak base water Figure 15.12

Kidneys help control pH by managing H+ and bicarbonate pH of urine = 4.5 to 8.0 depending on body’s needs and diet In general: High protein diet = acidic urine; Vegetarian = alkaline urine

Angiotensin II formed in blood Peripheral resistance Participating… Sensations of thirst are generated by the ____________ that also stimulates the release of _________ to stimulate the reabsorption of more _________ by the kidneys. ____________ help prevent great fluctuation on blood pH and are also maintained by the kidneys. hypothalmus ADH water Buffers Falling systemic blood pressure volume Reduced filtrate volume or solute content in renal tubules JG cells of kidneys (+) (+) = stimulates Renin-angiotension system Neural regulation (sympathetic nervous system effects) Effects of ADH release Renin Release Leads to Angiotensin II formed in blood Systemic arterioles Vasoconstriction Peripheral resistance Adrenal cortex Aldosterone Kidney tubules Na+ reabsorption (and H2O absorption) Blood volume Rising blood pressure Causes Results in Secretes Targets Releases Inhibits baroreceptors in blood vessels Sympathetic nervous system Hypothalamic osmoreceptors Posterior pituitary ADH (antidiuretic hormone) Collecting ducts of kidneys H2O reabsorption KEY: