The Urinary System eliminates waste Some waste products

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 DIGESTIVE SYSTEM RESPIRATORY SYSTEM § Acid-base balance in the blood § Blood pressure CARDIOVASCULAR SYSTEM URINARY SYSTEM water, solutes AND, kidneys also § Manage RBC production (erythropoietin) § Activate vitamin D elimination of excess water, salts, wastes

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. 1 b

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. 2 b

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

Kidneys filter blood, i. e. control plasma composition § 1/4 th 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. 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. 3 c

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

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

Participating… § The functional unit of the kidney is known as the _____ nephron. The three steps of urine formation are: 1. _______, 2. _______, and filtration reabsorption secretion 3. ______.

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 H 2 O

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 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 Figure 15. 7 in men

Participating… § The loop of Henle helps maximize the rewater. The urethra of ____ males absorption of_______ functions in both urinary and _______ reproductive systems and is longer than the urethra of females _____.

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

Maintaining Water and Electrolyte Balance Falling systemic blood pressure volume (+) Reduced filtrate volume or solute content in renal tubules Inhibits baroreceptors in blood vessels (+) (+) JG cells of kidneys (+) Sympathetic nervous system (+) Release Systemic arterioles Causes Renin Vasoconstriction Leads to Angiotensin II formed in blood (+) Hypothalamic osmoreceptors Results in Posterior pituitary Releases ADH (antidiuretic hormone) (+) Collecting ducts of kidneys Causes Peripheral resistance H 2 O reabsorption (+) Systemic arterioles Adrenal cortex Causes Secretes Vasoconstriction Aldosterone Results in Peripheral resistance Osmoreceptors in hypothalmus detect water content of plasma… Targets Kidney tubules Causes …stimulates thirst and release of ADH (antidiuretic hormone) = more H 2 O saved Na+ reabsorption (and H 2 O absorption) Results in Blood volume KEY: (+) = stimulates Rising blood pressure Renin-angiotension system Neural regulation (sympathetic nervous system effects) Effects of ADH release Figure 15. 11

Maintaining Water and Electrolyte Balance Falling systemic blood pressure volume (+) Reduced filtrate volume or solute content in renal tubules Inhibits baroreceptors in blood vessels (+) (+) JG cells of kidneys (+) Sympathetic nervous system (+) Release Systemic arterioles Causes Renin Vasoconstriction Leads to Angiotensin II formed in blood (+) Hypothalamic osmoreceptors Results in Posterior pituitary Releases ADH (antidiuretic hormone) (+) Collecting ducts of kidneys Causes Peripheral resistance H 2 O reabsorption (+) Systemic arterioles Causes Vasoconstriction Results in Peripheral resistance Low filtrate volume OR low b. p. = aldosterone release… Adrenal cortex …aldosterone Na+ reabsorption and H 2 O retention Secretes Aldosterone Targets Major BP control mechanism! Kidney tubules Causes Na+ reabsorption (and H 2 O absorption) Results in Blood volume KEY: (+) = stimulates Rising blood pressure Renin-angiotension system Neural regulation (sympathetic nervous system effects) Effects of ADH release Figure 15. 11

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

Buffers = chemicals that prevent drastic changes in p. H § Bind to H+ when p. H drops § Release H+ when p. H rises § Bicarbonate (remember this? ) = blood buffer H 2 CO 3 HCO 3 - + H+ HCl + Na. HCO 3 H 2 CO 3 + Na. Cl strong acid weak base weak acid salt Na. OH + H 2 CO 3 Na. HCO 3 + H 2 O strong base weak acid weak base water Figure 15. 12

Kidneys help control p. H by managing H+ and bicarbonate p. H of urine = 4. 5 to 8. 0 depending on body’s needs and diet In general: High protein diet = acidic urine; Vegetarian = alkaline urine

Participating… § Sensations of thirst are generated by the hypothalmus that also stimulates the release of ______ to stimulate the reabsorption of more ADH water Buffers _____ by the kidneys. ______ help prevent great fluctuation on blood p. H and are also maintained by the kidneys. Falling systemic blood pressure volume Reduced filtrate volume or solute content in renal (+) tubules (+) JG cells of kidneys Release Renin Leads to Inhibits baroreceptors in blood vessels (+) Sympathetic nervous system (+) Systemic arterioles Causes Vasoconstriction Results in Peripheral resistance Angiotensin II (+) formed in blood (+) Systemic arterioles Adrenal cortex Causes Secretes Vasoconstriction Aldosterone Results in Targets Peripheral resistance Kidney tubules Causes Na+ reabsorption (and H 2 O absorption) Results in Blood volume Rising blood pressure (+) Hypothalamic osmoreceptors (+) Posterior pituitary Releases ADH (antidiuretic hormone) (+) Collecting ducts of kidneys Causes H 2 O reabsorption KEY: (+) = stimulates Renin-angiotension system Neural regulation (sympathetic nervous system effects) Effects of ADH release