Chapter 16 Lecture Outline See separate PowerPoint slides for all figures and tables preinserted into PowerPoint without notes. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1
16.1 The Urinary System 2
A. Introduction 1. Excretion the removal of metabolic wastes from the body 2. Kidneys are the primary organ of excretion 3. Filter blood to produce urine 3
B. Functions of the urinary system 1. Excretion of metabolic wastes a. Urea 1) By-product of amino acid metabolism 2) Ammonia combines with carbon dioxide to produce urea in the liver 3) Less toxic than ammonia b. Creatinine result of the metabolic breakdown of creatine phosphate 4
Metabolic wastes, cont c. Uric acid 1) Result from the breakdown of nucleotides 2) Insoluble 3) Gout occurs if excess uric acid collects in the joints d. Urochrome 1) Waste product from liver breakdown of hemoglobin 2) Gives yellow color to urine 5
2. Preservation of water-salt balance a. Blood volume is closely associated with the salt (NaCl) balance of the body 1) Salts have the ability to cause osmosis 2) The more salts there are in the blood, the greater the blood volume b. Kidneys also maintain other ions in the blood 1) Potassium 2) Bicarbonate 3) Calcium 6
3. Maintenance of blood pressure a. Kidneys influence cardiac output regulating blood volume b. Kidneys influence peripheral resistance by producing renin 1) Activates angiotensin 2) Angiotensin constricts blood vessels 3) Aldosterone release increases blood volume 7
4. Maintenance of acid-base balance a. Kidneys excrete hydrogen ions from the blood into the urine b. Kidneys reabsorb bicarbonate ions and return them to the blood 8
5. Secretion of hormones a. Release renin when blood supply decreases 1) Activates angiotensin which causes release of aldosterone b. Erythropoietin (EPO) 1) Released when the oxygen-carrying capacity of the blood is reduced 2) Stimulates red blood cell production c. Kidneys help activate vitamin D 1) Precursor to calcitrol 2) Promotes calcium absorption from the digestive tract 9
C. Organs of the urinary system 1. Kidneys a. Bean-shaped, reddish-brown, paired organs b. Located in the lumbar region c. Retroperitoneal covered by the parietal peritoneum d. Held in place by the renal fascia and adipose tissue e. Covered by the renal capsule f. Hilum indention on medial surface where renal artery enters and renal vein and a ureter exit 10
The Urinary System 11
2. Ureters a. Extend from the kidneys to the posterior, inferior surface of the bladder b. Peristalsis moves urine into the bladder c. Wall layers: 1) Mucosa (mucous membrane) inner layer 2) Smooth muscle middle layer 3) Fibrous connective tissue outer layer 12
3. Urinary bladder a. In the pelvic cavity b. Stores urine c. Trigone area at the base of the bladder outlined by three openings 1) Two for the ureters 2) One for the urethra d. Detrusor muscle 1) Middle layer of circular fibers 2) Two layers of longitudinal muscle e. Mucosa of transitional epithelium and rugae f. Sphincters 1) Internal sphincter around the opening to the urethra 2) External sphincter composed of skeletal muscle 13
4. Urethra a. Extends from the urinary bladder to an external opening b. In males 1) Averages 20 cm when penis is not erect 2) Encircled by the prostate gland 3) Carries urine during urination and sperm during ejaculation c. In females 1) About 4 cm long 2) Prone to bacterial infection 14
D. Urination 1. Also called micturition 2. Stretch receptors in the bladder are stimulated when the bladder contains about 250mL of urine 3. Nerve impulses from the lumbar and sacral spinal cord cause the bladder to contract and the sphincters to relax 15
16.2 Anatomy of the kidney and excretion 16
A. Three regions of the kidney 1. Renal cortex outer layer that also dips into the medulla 2. Renal medulla contains the renal pyramids 3. Renal pelvis continuous with the pelvis 17
Gross anatomy of the kidney 18
B. Anatomy of a nephron 1. Blood supply a. Afferent arteriole (from the renal artery) b. Glomerulus c. Efferent arteriole d. Peritubular capillary network & vasa recta (to the renal vein) 19
2. Parts of a nephron a. Renal corpuscle 1) Glomerular capsule (Bowman s capsule) inner layer of podocytes 2) Glomerulus b. Renal tubule 1) Proximal convoluted tubule (PCT) cuboidal epithelium with microvilli 2) Loop of Henle simple squamous 3) Distal convoluted tubule (DCT) cuboidal with no microvilli 4) Collecting duct 20
Nephron anatomy 21
C. Urine formation 1. Glomerular Filtration a. Whole blood enters the afferent arteriole and the glomerulus b. Glomerular blood pressure causes blood to be filtered 1) Water 2) Nitrogenous wastes 3) Nutrients 4) Salts (ions) 5) Creatinine and urochrome c. Nonfiltered components leave the glomerulus by the efferent arteriole 1) Formed elements (blood cells and platelets) 2) Plasma proteins 22
2. Tubular reabsorption a. Involve both passive and active processes b. Occurs in the PCT c. Molecules and ions are reclaimed from the filtrate and moved back into the blood 1) Water 2) Nutrients (i.e. glucose and amino acids) 3) Required salts (ions) 4) Some urea and uric acid 23
Tubular reabsorption, cont d. Substances that are not reabsorbed 1) Some water 2) Nitrogenous wastes 3) Excess salts (ions) 4) Creatinine and urochrome 5) Molecules with no carriers e. Every substance has a maximum rate of transport based on the number of carrier molecules 24
3. Tubular secretion a. Substances are removed from the blood into the tubule filtrate 1) Hydrogen ions 2) Potassium ions 3) Creatinine 4) Drugs b. Active process c. Occurs in the DCT 25
Steps in urine formation 26
16.3 Regulatory functions of the kidneys 27
A. Fluid and electrolyte balance 1. Total water intake should equal total water loss 2. How water enters the body a. Liquids we drink b. Foods c. By-product of metabolism 3. How water exits the body a. Urine b. Sweat c. Exhaled air d. Feces 28
4. Electrolytes are also gained and lost 5. Water content of the body a. Average male is 60% water by weight b. Average female is 50% water by weight c. Two-thirds of body water is intracellular d. One-third of body water is extracellular plasma, tissue fluid, and lymph 29
Location of fluids in the body 30
Fluid balance 31
B. Reabsorption of water 1. Reabsorption of salt leads to the reabsorption of water due to osmosis 2. Most reabsorbed in the PCT 3. Excretion of hypertonic urine is dependent on the reabsorption of water from the loop of Henle and the collecting duct a. Loop of Henle 1) Descending limb is permeable to water which leaves by osmosis 2) Ascending limb actively transport salt into the renal medulla but is impermeable to water 32
Loop of Henle, cont 3) Countercurrent mechanism movement of salt out of the ascending limb draws water out of the descending limb b. Collecting duct water moves out by osmosis and is influenced by hormones 4. Vasa recta area of the peritubular capillaries absorbs salt and water equally to minimize loss of solutes from the medulla 33
5. Antidiuretic hormone (ADH) a. Released from the posterior pituitary gland in response to increased solute concentration of the blood detected by receptors in the hypothalamus. b. Causes aquaporins in the wall of the collecting duct to open and water to be reabsorbed c. Decreases the amount of urine 34
Reabsorption of water 35
C. Reabsorption of electrolytes 1. The major electrolytes a. Sodium b. Potassium c. Bicarbonate ion d. Other ions calcium and monohydrogen phosphate ions 2. The kidneys a. Greater than 99% of filtered sodium is reabsorbed back into the blood b. 67% is reabsorbed at the PCT c. 25% is reabsorbed at the ascending limb of the loop of Henle d. The rest is reabsorbed from the DCT and the collecting duct 36
3. Aldosterone a. Promotes the excretion of potassium b. Promotes the reabsorption of sodium and water c. Kidneys release renin when blood pressure is too low to promote glomerular filtration d. Sensor cells are in the juxtaglomerular apparatus e. Renin converts angiotensinogen to angiotensin I f. Angiotensin I is converted to angiotensin II g. Angiotensin II stimulates the release of aldosterone 37
Juxtaglomerular apparatus 38
4. Atrial natriuretic hormone (ANH) a. Secreted by the atria of the heart when blood volume is high b. Inhibits the secretion of renin and aldosterone c. Promotes the excretion of sodium and water 39
5. Diuretics a. Chemicals that increase the flow of urine b. Examples: 1) Alcohol 2) Caffeine 3) Diuretic drugs 40
D. Acid-base balance 1. Normal ph range 7.35-7.45 a. Acidosis below 7.4 b. Alkalosis above 7.4 2. Acid-Base Buffer Systems a. Buffer a chemical that can take up excess hydrogen or hydroxide ions b. An important buffer in the blood is a combination of carbonic acid and bicarbonate ions 41
Acid-base balance, cont 3. Respiratory Regulation of Acid-Base Balance a. Increasing the breathing rate rids the body of hydrogen ions b. Breathing readjusts the proportion of carbonic acid and bicarbonate ions in the blood 42
4. Renal Regulation of Acid-Base Balance a. Can rid the body of a wide range of acidic and basic substances b. Slower acting than other two systems c. Have a more powerful effect on ph d. Reabsorb bicarbonate ions and excrete hydrogen ions as needed to maintain a normal ph e. Ammonia and phosphate ions are buffers for hydrogen ions in the urine 43
Acid-base balance 44
16.4 Problems with kidney function 45
A. Introduction 1. Water accounts for about 95% of urine volume 2. Remaining 5% consists of electrolytes and various solutes 3. Urine usually does not contain proteins and blood cells 4. Urinalysis is an examination of the physical, chemical, and microscopic properties of the urine 5. Composition of urine changes if disease has altered body metabolism or if kidney function is abnormal 46
Composition of Urine 47
B. Illnesses affecting urinary function 1. Diabetes mellitus 2. Hypertension 3. Inherited conditions C. Infections affecting urinary function 1. Urethritis - urethra 2. Cystitis - bladder 3. Pyelonephritis kidneys D. Renal calculi 48
E. Glomerular damage 1. May allow large substances to be filtered a. Albumin, white blood cells, and possibly red blood cells b. Detected by a urinalysis 2. Extensive damage can cause uremia 49
F. Hemodialysis 1. Utilizes either an artificial kidney machine or continuous ambulatory peritoneal dialysis (CAPD) 2. Dialysate dialysis solution 3. Used to extract waste products, toxic chemicals, and drugs from patient s blood 4. Used to add needed substances to the patient s blood 5. Three- to six-hour treatment twice a week 50
Artificial kidney machine 51
G. Renal transplantation 1. A functioning kidney from a donor is received by a patient with renal failure 2. Possibility of organ rejection 3. One-year survival rate is 97% if the kidney is from a relative and 90% if it is from a nonrelative 4. Patient must take anti-rejection medication for the rest of his or her life 52
16.5 Effects of aging 53
A. Effects of Aging 1. Total renal function may decrease to only 50% 2. Kidneys decrease in size and have fewer nephrons 3. Kidney stones are more common 4. Infections are more common 5. Enlargement of the prostate in males 6. Incontinence 54
16.6 Homeostasis 55
A. Homeostasis 1. Excretion removal of metabolic wastes a. Sweat glands water, salt, urea b. Liver urochrome, urea c. Lungs carbon dioxide and water d. Kidneys are the primary organ of excretion urea, creatinine, uric acid 2. Kidneys are the primary organs of homeostasis a. Water-salt balance blood pressure, capillary exchange b. Acid-base balance along with blood buffers and the respiratory system 56
Homeostasis, cont 3. The kidneys assist the endocrine and cardiovascular systems by producing erythropoietin and renin 4. Regulation of blood calcium levels assist the skeletal, nervous, and muscular systems 5. Regulation of blood sodium, potassium, and other ions 57
Human Systems work Together 58