Chapter 16 Lecture Outline See separate PowerPoint slides for all figures and tables preinserted into PowerPoint without notes. Copyright 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1 The Urinary System and Excretion 16.1 Urinary System

2 Introduction Excretion the removal of metabolic wastes from the body Kidneys are the primary organ of excretion Filter blood to produce urine

3 Functions of the Urinary System In producing urine, the kidneys carry out the following functions: 1. Excretion of metabolic wastes 2. Preservation of water-salt balance in blood and body fluids 3. Maintenance of blood pressure 4. Maintenance of acid-base balance 5. Secretion of hormones

4 Functions of the Urinary System, cont. 1. Excretion of metabolic wastes a. Urea- By-product of amino acid metabolism Ammonia combines with carbon dioxide to produce urea in the liver Less toxic than ammonia b. Creatinine - Results from metabolic breakdown of creatine phosphate

5 Functions of the Urinary System, cont. c. Uric acid - Results from the breakdown of nucleotides Insoluble Gout d. Urochrome - Waste product from liver breakdown of hemoglobin

Gives yellow color to urine 6 Functions of the Urinary System, cont. 2. Preservation of water-salt balance Blood volume is closely associated with the salt (NaCl) balance of the body Salts have the ability to cause osmosis The more salts there are in the blood, the greater the blood volume

Kidneys also maintain the balance of other ions in the blood: Potassium Bicarbonate Calcium 7 Functions of the Urinary System, cont. 3. Maintenance of blood pressure Kidneys influence cardiac output,

regulating blood volume Kidneys influence peripheral resistance by producing renin Activates angiotensin - constricts blood vessels Aldosterone release increases blood volume 8 Functions of the Urinary System, cont.

4. Maintenance of acid-base balance Kidneys excrete hydrogen ions from the blood into the urine Kidneys reabsorb bicarbonate ions and return them to the blood 9 Functions of the Urinary System, cont. 5. Secretion of hormones a. Renin released when blood supply to kidney decreases

Activates angiotensin, which causes release of aldosterone b. Erythropoietin (EPO) - Released when the oxygen-carrying capacity of the blood is reduced Stimulates RBC production c. Kidneys help activate vitamin D Precursor to calcitriol promotes calcium absorption from the digestive tract 10

Functions of the Urinary System, cont. Work of the kidneys, by the numbers Kidneys filter 180 L of blood a day 125ml/min 7.5L/hr Only 1% of that leaves the body as urine; the rest is reabsorbed into the blood 11 Organs of the Urinary System

1. Kidneys Bean-shaped, reddish-brown, paired Located in the lumbar region Retroperitoneal Held in place by the renal fascia and adipose tissue Covered by the renal capsule Hilum indention on medial surface where renal artery enters and renal vein and a ureter exit 12

The Urinary System 13 Organs of the Urinary System, cont. 2. Ureters Extend from the kidneys to the posterior, inferior surface of the bladder Peristalsis moves urine into the bladder

Wall layers: Mucosa inner layer Smooth m.t. middle layer Fibrous c.t. outer layer 14 Organs of the Urinary System, cont. 3. Urinary bladder - in the pelvic cavity Trigone area at the base of the bladder, outlined by three openings: Two for the ureters; One for the urethra

Detrusor muscle all the muscles in the wall of the bladder Middle layer of circular fibers Two layers of longitudinal muscle Mucosa of transitional e.t. and rugae Sphincters Internal sphincter around the opening to the urethra; smooth m.t. External sphincter skeletal m.t. 15 Organs of the Urinary System, cont.

4. Urethra - Extends from the urinary bladder to an external opening Males Averages 20 cm when penis is not erect Encircled by the prostate gland Carries urine during urination and sperm during ejaculation Females About 4 cm long Prone to bacterial infection 16

Urination Also called micturition Stretch receptors in the bladder are stimulated when the bladder contains about 250mL of urine Parasympathetic nerve impulses from the lumbar and sacral spinal cord cause the bladder to contract and the sphincters to relax Brain has control over this reflex after about three years old

17 Urination 18 Chapter 16 Animation Slides To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please Note: Once you have used any of the animation

functions (such as Play or Pause), you must first click on the slides background before you can advance to the next slide. Copyright McGraw-Hill Education. Permission required for reproduction or display. 19 Micturition Reflex 20 The Urinary System and Excretion

16.2 Anatomy of the Kidney and Excretion 21 Introduction Three regions of the kidney: 1. Renal cortex 2. Renal medulla Contains the renal pyramids 3. Renal pelvis continuous with the

ureters 22 Gross Anatomy of the Kidney 23 Anatomy of a Nephron Each kidney contains more than one million nephrons, the microscopic functional units of the kidneys

Two types of nephrons: Cortical shorter; located primarily in the renal cortex Juxtamedullary extend deep into the medulla Two parts to a nephron 1. Renal corpuscle 2. Renal tubule 24 Anatomy of a Nephron, cont. 1. Renal corpuscle

a. Glomerular (Bowmans) capsule inner layer of podocytes, which have pores for filtration to allow substances to leave the glomerulus and enter the glomerular capsule b. Glomerulus 25 Anatomy of a Nephron, cont. 2. Renal tubule a. Proximal convoluted tubule (PCT)

Simple cuboidal e.t. with microvilli (brush border) b. Loop of Henle simple squamous e.t. Descending and Ascending Loops c. Distal convoluted tubule (DCT) Simple cuboidal e.t. with no microvilli d. Collecting tubules many of these merge into a collecting duct Collecting ducts are located in the renal medulla 26

Anatomy of a Nephron Blood supply Afferent arteriole (from the renal a.) Glomerulus Efferent arteriole Peritubular capillary network to

venules, then to the renal vein 27 Nephron Anatomy 28 Nephron Anatomy 29

Urine Formation The 1. 2. 3. three steps of urine formation are: Glomerular filtration Tubular reabsorption Tubular secretion 30

Urine Formation 1. Glomerular Filtration Blood enters the afferent arteriole, then the glomerulus High glomerular blood pressure causes blood to be filtered: Water and small solutes leave the glomerulus, enters glomerular capsule What gets filtered? Water, nitrogenous wastes, nutrients, salts (ions), creatinine, urochrome

What isnt filtered? Formed elements, plasma proteins Stays in the blood; leave the glomerulus by the efferent arteriole: 31 Urine Formation, cont. Glomerular filtrate fluid in the glomerular capsule There are a lot of substances in the filtrate that do not end up in the urine These are things the body needs, so are

reabsorbed back into the blood Urine tests can detect drugs and other substances that an individual ingests 32 Urine Formation, cont. 2. Tubular reabsorption occurs in PCT Involves passive and active processes Brings useful substances back into the blood from the filtrate Water, nutrients (glucose, amino acids),

needed salts, some urea and uric acid Na+ reabsorbed first, Cl- follows, then water Substances that are not reabsorbed: Some water, nitrogenous wastes, excess salts, creatinine, urochrome, and molecules with no carriers 33 Urine Formation, cont.

Every substance has a maximum rate of transport based on the number of carrier molecules there are E.g. glycosuria: In diabetes mellitus, excess glucose in the blood means there is excess glucose in the tubular fluid; the transporters are overwhelmed, and sugar ends up in the urine Sugar in the filtrate draws water in by

osmosis; excess urination and thirst/dehydration results 34 Urine Formation, cont. 3. Tubular secretion occurs in DCT Substances are removed from the blood and move into the tubular fluid What is secreted? Hydrogen ions, potassium ions, creatinine, drugs Active process

The final product, urine, contains substances that have been filtered but not reabsorbed plus substances that have been secreted 35 Steps in Urine Formation 36 The Urinary System and Excretion 16.3 Regulatory Functions of the

Kidneys 37 Introduction The kidneys regulate fluid and electrolyte balance, and acid-base balance 38 Fluid and Electrolyte Balance Water

content of the body Average male is 60% water by weight Average female is 50% water by weight Two-thirds of body water is intracellular One-third of body water is extracellular plasma, tissue fluid, and lymph

Other locations: cerebrospinal fluid, synovial fluid 39 Fluid and Electrolyte Balance, cont.

Total water intake should equal total water loss How water enters the body: Liquids we drink Foods By-product of metabolism

How water exits the body: Urine Sweat Exhaled air Feces Electrolytes are also gained and lost 40 Location of Fluids in the Body 41

Fluid Balance 42 Reabsorption of Water Reabsorption of salt leads to the reabsorption of water due to osmosis Most water is reabsorbed in the PCT

Excretion of hypertonic urine is dependent on the reabsorption of water from the loop of Henle and the collecting duct 43 Reabsorption of Water, cont. Loop of Henle Descending limb is permeable to water, which leaves by osmosis Ascending limb actively transports salt into the renal medulla but is impermeable to

water Collecting duct water moves out by osmosis and is influenced by hormones 44 Reabsorption of Water at the Loop of Henle and Collecting Duct 45 Reabsorption of Water, cont.

Antidiuretic hormone (ADH) Produced by the hypothalamus, released from the posterior pituitary gland in response to increased solute concentration of the blood Causes aquaporins in the wall of the collecting duct to open water reabsorbed via diffusion ADH increases water reabsorption decreases the amount of urine produced

Blood volume increases blood pressure increases 46 Reabsorption of Electrolytes Electrolytes are molecules that can ionize and carry an electrical current The major electrolytes: Sodium nerve conduction, blood osmolarity Potassium nerve conduction Bicarbonate ion how carbon dioxide is carried in the blood

Other ions calcium and monohydrogen phosphate ions bone formation, metabolism 47 Reabsorption of Electrolytes, cont. The kidneys Greater than 99% of filtered sodium is reabsorbed back into the blood 67% is reabsorbed at the PCT 25% is reabsorbed at the ascending limb of the loop of Henle

The rest is reabsorbed from the DCT and the collecting duct 48 Reabsorption of Electrolytes, cont. Aldosterone Promotes excretion of potassium Promotes reabsorption of sodium and therefore water Kidneys release renin when blood pressure is too low to promote glomerular filtration

Blood pressure sensor cells are in the juxtaglomerular apparatus 49 Juxtaglomerular Apparatus 50 Reabsorption of Electrolytes, cont. Renin is an enzyme that converts angiotensinogen to angiotensin I

Angiotensin I is converted to angiotensin II Angiotensin II stimulates the release of aldosterone from the adrenal cortex Aldosterone increases reabsorption of sodium, which increases the reabsorption of water Blood volume and blood pressure increase 51 Reabsorption of Electrolytes, cont. Atrial natriuretic hormone (ANH)

Secreted by the atria of the heart when blood volume is high, which stretches the walls of the atria Inhibits the secretion of renin and aldosterone Promotes the excretion of sodium (natriuresis) and water Decreases blood volume and blood pressure 52 Reabsorption of Electrolytes, cont.

Diuretics - Chemicals that increase urine flow Examples: Alcohol inhibits the secretion of ADH Caffeine increases the glomerular filtration rate and decreases tubular reabsorption of sodium Diuretic drugs decrease water reabsorption, which decreases blood volume and blood pressure 53

Acid-Base Balance Normal pH range, where enzymes work optimally 7.35-7.45 Acidosis below 7.4 Alkalosis above 7.4

Ingested foods and metabolism bring acids and bases into the body pH of body fluids stays within normal range via three main mechanisms: 1. Acid-base buffer systems 2. The respiratory center 3. The kidneys 54 Acid-Base Balance, cont. Renal Regulation of Acid-Base Balance

Can rid the body of a wide range of acidic and basic substances Slower acting than other two systems but has a more powerful effect on pH Reabsorbs bicarbonate ions and excretes hydrogen ions as needed to maintain a normal pH Ammonia and phosphate ions are buffers for hydrogen ions in the urine

55 Acid-Base Balance 56 The Urinary System and Excretion 16.4 Problems with Kidney Function 57

Introduction Water accounts for about 95% of urine volume; remaining 5% consists of electrolytes and various solutes Urine usually does not contain proteins and

blood cells Urinalysis is an examination of the physical, chemical, and microscopic properties of the urine Composition of urine changes if disease has altered body metabolism or if kidney function is abnormal 58 Composition of Urine

59 Introduction, cont. Some conditions cause progressive renal disease and failure: Diabetes mellitus Hypertension Inherited conditions

60 Introduction, cont. Infections affecting urinary function: Urethritis urethra Cystitis bladder Pyelonephritis kidneys Renal calculi kidney stones Most made of calcium salts Most caused by genetics 61

Introduction, cont. Glomerular damage May allow large substances to be filtered Albumin, white blood cells, and possibly red blood cells may be found in the urine Detected by a urinalysis Extensive damage can cause uremia high levels of wastes in the blood

62 Hemodialysis Utilizes either an artificial kidney machine or continuous ambulatory peritoneal dialysis (CAPD) Peritoneum is the dialysis membrane Dialysate dialysis solution

Used to extract waste products, toxic chemicals, and drugs from patients blood Used to add needed substances to the patients blood 63 Hemodialysis, cont.

Substances in greater concentration in the blood than the dialysate will diffuse out of the blood; substances in greater concentration in the dialysate will diffuse into the blood Three- to six-hour treatment twice a week 64 Artificial Kidney Machine

65 Renal Transplantation A functioning kidney from a donor is received by a patient with renal failure Possibility of organ rejection One-year survival rate is 97% if the kidney is from a relative and 90% if it is from a nonrelative Patient must take anti-rejection medication for the rest of his or her life

66 The Urinary System and Excretion 16.5 Effects of Aging 67 Effects of Aging

Total renal function may decrease to only 50% Kidneys decrease in size and have fewer nephrons Kidney stones are more common Infections are more common Enlargement of the prostate in males Incontinence

68 The Urinary System and Excretion 16.6 Homeostasis 69 Homeostasis Excretion removal of metabolic wastes Sweat glands water, salt, urea

Liver urochrome, urea Lungs carbon dioxide and water Kidneys are the primary organ of excretion urea, creatinine, uric acid 70 Homeostasis, cont. Kidneys are the primary organs of homeostasis Water-salt balance blood pressure, capillary exchange Acid-base balance along with blood

buffers and the respiratory system 71 Homeostasis, cont. The kidneys assist the endocrine and

cardiovascular systems by producing erythropoietin and renin Regulation of blood calcium levels assists the skeletal, nervous, and muscular systems Regulation of blood levels of sodium, potassium, and other ions 72

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