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Inquiry into LifeTwelfth Edition
Chapter 16
Lecture PowerPoint to accompany
Sylvia S. Mader
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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16.1 Urinary System
Functions of the Urinary System
Excretion of Metabolic Wastes
Urea, Creatinine, Uric acid
Maintenance of Water-Salt Balance NaCl, K+, HCO3
-, Ca2+
Maintenance of Acid-Base Balance
Excretion of H+, reabsorption of HCO3-
Secretion of Hormones Renin, Erythropoietin
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The Urinary System
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16.1 Urinary System
Organs of the Urinary System Kidneys
Located in lumbar region
Behind peritoneum
Covered by tough capsule of fibrous connective tissue
Concave side has a depression called a hilum
Location of renal artery and vein
Ureters Conduct urine from kidney to bladder
Three-layered wall
Mucosa, smooth muscle, outer connective tissue
Conveys urine by peristalsis
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16.1 Urinary System
Organs of the Urinary System
Urinary Bladder
Stores urine
Has three openings
Two for the ureters, one for the urethra
The bladder wall is expandable
Two sphincter muscles control the release of urine into the
urethra
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16.1 Urinary System
Organs of the Urinary System
Urethra
A small tube that leads from the urinary bladder to anexternal opening
Its function is to remove urine from the body
The urethra is longer males than females
The urethra also transports semen in males
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16.1 Urinary System
Urination
Stretch receptors in
wall of bladder
Send impulses whenbladder fills to 250 ml
Motor impulses from
spinal cord
Bladder contraction
Micturition occurs
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16.2 Anatomy of the Kidney
and Excretion
There are three regions to a kidney
The renal cortex
The renal medulla
The renal pelvis
Nephrons are the functional units of the kidney
Each kidney has over one million nephrons
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Gross Anatomy of the Kidney
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16.2 Anatomy of the Kidney
and Excretion
Anatomy of a Nephron
A nephron is composed of a system of tubules
Each nephron has its own blood supply
From renal artery, afferent arteriole leads into the glomerulus
Blood leaves the glomerulus via an efferent arteriole
Efferent arteriole takes blood to peritubular capillaries
These surround rest of the nephron
Blood then goes to renal vein
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Nephron Anatomy
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16.2 Anatomy of the Kidney
and Excretion
Parts of a Nephron
Glomerular capsule (Bowmans capsule)
Cuplike structure
Inner layer has podocytes Form pores for passage of small molecules
Proximal convoluted tubule (PCT)
Cuboidal epithelial cells with microvilli
Increased surface area for absorption
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16.2 Anatomy of the Kidney
and Excretion
Parts of a Nephron
Loop of Henle
U-shaped tube
Simple squamous epithelium
Distal Convoluted tubule (DCT)
Lack microvilli
Designed for tubular excretion rather than reabsorption
Collecting Ducts
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Processes in Urine Formation
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16.2 Anatomy of the Kidney
and Excretion
Urine Formation
Glomerular Filtration
Blood enters the afferent arteriole and glomerulus
Blood pressure forces water and small molecules into theglomerular capsule (filtration)
Large molecules and formed elements cannot leave the
capillaries
Remaining processes must reabsorb desirable substances
and allow wastes to pass
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16.2 Anatomy of the Kidney
and Excretion
Urine Formation
Glomerular Filtration
Filterable Blood
Components
Nonfilterable Blood
Components
Water Blood cells and
platelets
Nitrogenous wastes Plasma proteins
Nutrients
Salts
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16.2 Anatomy of the Kidney
and Excretion
Urine Formation Tubular Reabsorption
Molecules are reabsorbed both actively and passively
Sodium reabsorbed by active transport
Chloride follows passively Water absorbed by osmosis
Only molecules recognized by carrier proteins are activelyreabsorbed
Glucose is an example
There is a limited number of carrier proteins Excess glucose ends up being excreted
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16.2 Anatomy of the Kidney
and Excretion
Urine Formation
Tubular Reabsorption
Reabsorbed Filtrate
Components
Nonreabsorbed
FiltrateComponents
Most water Some water
Nutrients Much nitrogenous
wastesRequired salts (ions) Excess salts (ions)
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16.2 Anatomy of the Kidney
and Excretion
Urine Formation
Tubular Secretion
Hydrogen ions, potassium, creatinine, many drugs
Actively transported from the blood
Urine Contains
Filtered substances that have not been reabsorbed
Substances that have been actively secreted
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16.3 Regulatory Functions
of the Kidneys
Reabsorption of Water
Excretion of hypertonic urine depends on
reabsorption of water from the loops of the nephrons
and the collecting ducts
Reabsorption of water requires
Reabsorption of salt
Establishment of solute gradient
Reabsorption of water
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16.3 Regulatory Functions
of the Kidneys
Reabsorption of Water
Reabsorption of Salt Regulated by the absorption and excretion of ions
Na+, K+, HCO3-, Mg2+
More than 99% of Na+ filtered at the glomerulus is returnedto the blood
67% is reabsorbed at the proximal tubule
25% is reabsorbed at the ascending limb of the nephron loop
The rest is reabsorbed from the distal convoluted tubule andthe collecting duct
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16.3 Regulatory Functions
of the Kidneys
Reabsorption of Water
Reabsorption of Salt Hormonal Regulation at the Distal Convoluted Tubule
Occurs when blood pressure at the glomerulus is low
Juxtaglomerular Apparatus secretes renin
Renin is an enzyme that changes angiotensinogen intoAngiotensin I
Angiotensin I is then converted into Angiotensin II
Angiotensin II stimulates the adrenal cortex to release aldosterone
Aldosterone promotes the excretion of K+ and the reabsorption ofNa+
The reabsorption of Na+ is followed by the reabsorption of H2O
Blood volume and blood pressure increase
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16.3 Regulatory Functions
of the Kidneys
Reabsorption of Water
Reabsorption of Salt Hormonal Regulation at the Distal Convoluted Tubule
Atrial naturietic hormone (ANH)
Another hormone regulating sodium
Secreted by right atrium of heart in response to stretching
Indicates increased blood volume
Inhibits renin secretion by juxtaglomerular apparatus
Inhibits aldosterone release
Promotes sodium excretion - natriuresis
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Juxtaglomerular Apparatus
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16.3 Regulatory Functions
of the Kidneys
Establishment of Solute Gradient
A long loop of nephron has two parts
Descending limb and ascending limb
Salt diffuses out of lower part of ascending limb Upper part of ascending limb actively transports more salt out
This creates high osmotic pressure (high solute concentration)within the tissues of the renal medulla
Urea contributes to high solute concentration in medulla
Leaks from lower collecting duct This results in a concentration gradient favoring reabsorption of
water
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Reabsorption of Water
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16.3 Regulatory Functions
of the Kidneys
Reabsorption of Water
Water leaves distal convoluted tubule because of the
osmotic gradient
Water also leaves descending limb of loop of thenephron
Countercurrent multiplier
As filtrate enters collecting duct it is hypotonic to cells
of renal cortex
Permeability of collecting duct under hormonal control
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16.3 Regulatory Functions
of the Kidneys
Reabsorption of Water Permeability of collecting duct is under hormonal
control
Antidiuretic hormone (ADH) is produced by the posteriorpituitary gland
In the absence of ADH, a dilute urine is produced
In the presence of ADH, the collecting duct become more
permeable to water and a concentrated urine is produced
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16.3 Regulatory Functions
of the Kidneys
Diuretics Increase flow of urine
Alcohol
Shuts off ADH
Dehydration causes hangover
Caffeine
Increases glomerular filtration rate
Decreases tubular reabsorption of sodium
Diuretic drugs
Many inhibit active transport of sodium at loop of the nephron or thedistal convoluted tubule
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16.3 Regulatory Functions
of the Kidneys
Acid-Base Balance
Normal pH for most body fluids is 7.4
Alkalosis: pH is greater than 7.4 Acidosis: pH is less than 7.4
Several Mechanisms Maintain a pH of ~ 7.4
Acid-Base buffer system Respiratory Center
The Kidneys
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16.3 Regulatory Functions
of the Kidneys
Acid-Base Balance Acid-Base Buffer Systems
Chemical or combination of chemicals
Can take up excess H+ or OH-
Prevents large changes in pH
When H+ added to blood the following occurs
H+ + HCO3- H2CO3
When OH- added to blood the following occurs
OH- + H2CO3 HCO3- + H2O
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16.3 Regulatory Functions
of the Kidneys
Acid-Base Balance
Respiratory Center
Increasing breathing rate removes CO2 Removes hydrogen ions
Forces reaction to the right
H+ + HCO3- H2CO3 H2O + CO2
Respiratory system adjusts proportion of
bicarbonate and carbonic acid
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16.3 Regulatory Functions
of the Kidneys
Acid-Base Balance
The Kidneys
Only kidneys can remove many acids and bases
Slower acting than respiratory system but more powerful
Reabsorbs bicarbonate ions
Excretes hydrogen ions
In urine ammonia can absorb hydrogen ions
Phosphate provides another means of buffering hydrogen
ions in urine
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Acid-Base Balance
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16.4 Disorders of the Urinary System
Disorders of the Kidneys Pyelonephritis: Infections of the kidneys
Kidney infections usually result from bladder infections
Most are curable with antibiotics if diagnosed in time
Some infections can cause severe damage
Kidney Stones
Hard granules that form in the renal pelvis
Composed of substances such as calcium, phosphate, uric acid andprotein
Excess animal protein in the diet, imbalanced urinary pH, and
urinary tract infections may be contributing factors May pass unnoticed in the urine,large stones can be very painful
The presence of albumin or blood cells in the urine are earlysigns of kidney damage
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16.4 Disorders of the Urinary System
Disorders of the Kidneys Hemodialysis
Artificial kidney machine or continuous ambulatory peritonealdialysis (CAPD)
Dialysis Diffusion of dissolved molecules through a membrane
Selective permeability
Blood is cleansed
pH is adjusted
Water and salt balance maintained
In CAPD the peritoneum is the dialysis membrane
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An Artificial Kidney Machine
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16.4 Disorders of the Urinary System
Disorders of the Bladder and Urethra Bladder Infections
Urine leaving the bladder is usually bacteria-free
The urethra is normally colonized with bacteria
Sometimes bacteria make their way to the bladder
Usually treatable with antibiotics
Bladder Stones
Occur as a result of bladder infections or prostate enlargement
May actually be kidney stones that were carried to the bladder
Can be removed surgically or broken apart by lithotripsy
Bladder Cancer
Smoking greatly increases the risk
Some types are very malignant necessitating removal of thebladder.
Recommended