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Essentials of Human Anatomy & Physiology
Elaine N. Marieb
Seventh Edition
Chapter 14
The Digestive System
and Body Metabolism
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The Digestive System and Body
Metabolism
 Digestion
Breakdown of ingested food
 Absorption
 Passage of nutrients into the blood
 Metabolism
 Production of cellular energy (ATP)
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Slide 14.1
Organs of the Digestive System
 Two main groups
 Alimentary canal – continuous coiled hollow
tube
 Accessory digestive organs
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Organs of the Digestive System
Figure 14.1
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Organs of the Alimentary Canal
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus
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Slide 14.3
Mouth (Oral Cavity) Anatomy
 Lips (labia) – protect
the anterior opening
 Cheeks – form the
lateral walls
 Hard palate – forms
the anterior roof
 Soft palate – forms
the posterior roof
 Uvula – fleshy
projection of the
soft palate
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Figure 14.2a
Slide 14.4
Mouth (Oral Cavity) Anatomy
 Vestibule – space
between lips and
gums
 Oral cavity – area
contained by the
teeth
 Tongue – attached at
hyoid and styloid
processes of the
skull, and by the
lingual frenulum
Figure 14.2a
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Slide 14.5
Mouth (Oral Cavity) Anatomy
 Tonsils
 Palatine tonsils
 Lingual tonsil
Figure 14.2a
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Slide 14.6
Processes of the Mouth
 Mastication (chewing) of food
(mechanical)
 Mixing masticated food with saliva
 Initiation of swallowing by the tongue
 Allowing for the sense of taste
 (Add this bullet)Chemical breakdown of
carbohydrates
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Slide 14.7
Pharynx Anatomy
 Nasopharynx –
not part of the
digestive system
 Oropharynx –
posterior to oral
cavity
 Laryngopharynx –
below the oropharynx
and connected to
the esophagus
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Figure 14.2a
Slide 14.8
Pharynx Function
 Passageway for air and food
 Food is propelled to the esophagus by
two muscle layers
 Longitudinal inner layer
 Circular outer layer
 Food movement is by alternating
contractions of the muscle layers
(peristalsis)
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Slide 14.9
Esophagus
 Runs from pharynx to stomach through
the diaphragm
 Conducts food by peristalsis
(slow rhythmic squeezing)
 Passageway for food only
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Layers of Alimentary Canal Organs
 Mucosa
 Innermost layer
 Moist membrane
 Surface epithelium
 Small amount of connective tissue
(lamina propria)
 Small smooth muscle layer
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Layers of Alimentary Canal Organs
 Submucosa
 Just beneath the mucosa
 Soft connective tissue with blood vessels,
nerve endings, and lymphatics
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Layers of Alimentary Canal Organs
 Muscularis externa – smooth muscle
 Inner circular layer
 Outer longitudinal layer
 Serosa
 Outermost layer – visceral peritoneum
 Layer of serous fluid-producing cells
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Layers of Alimentary Canal Organs
Figure 14.3
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Stomach Anatomy
 Left side of the abdominal cavity
 Food enters at the cardioesophageal
sphincter
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Stomach Anatomy
 Regions of the stomach
 Cardiac region – near the heart
 Fundus
 Body
 Pylorus – funnel-shaped terminal end
 Food empties into the small intestine at
the pyloric sphincter
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Stomach Anatomy
 Rugae – internal folds of the mucosa
 External regions
 Lesser curvature
 Greater curvature
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Stomach Anatomy
Figure 14.4a
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Stomach Functions
 Storage tank for food
 Site of food breakdown (mechanical)
 Chemical breakdown of protein begins
 Delivers chyme (processed food) to the
small intestine
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Small Intestine
 Body’s major digestive organ
 Site of nutrient absorption into the blood
 Muscular tube
 Suspended from the posterior
abdominal wall by the mesentery
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Subdivisions of the Small Intestine
“Dogs Just Itch!”
 Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
 Jejunum
 Attaches to duodenum
 Ileum
 Extends from jejunum to large intestine
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Chemical Digestion in the Small
Intestine
 Source of enzymes that are mixed with
chyme
Intestinal cells
Pancreas
 Bile enters from the gall bladder
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Chemical Digestion in the Small
Intestine
Figure 14.6
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Villi of the Small Intestine
 Fingerlike
structures formed
by the mucosa
 Increase surface
area
Figure 14.7a
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Microvilli of the Small Intestine
 Small projections of the
plasma membrane
 Found on absorptive cells
Figure 14.7c
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Structures Involved in Absorption of
Nutrients
 Absorptive cells
 Blood capillaries
 Lacteals (specialized
lymphatic capillaries)
Figure 14.7b
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Absorption in the Small Intestine
 Water is absorbed along the length of
the small intestine
 End products of digestion
 Most substances are absorbed by active
transport through cell membranes
 Lipids are absorbed by diffusion
 Substances are transported to the liver
by the hepatic portal vein or lymph
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Propulsion in the Small Intestine
 Peristalsis is the major means of
moving food
 Segmental movements
 Mix chyme with digestive juices
 Aid in propelling food
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Large Intestine
 Larger in diameter, but shorter than the
small intestine
 Frames the internal abdomen
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Large Intestine
Figure 14.8
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Functions of the Large Intestine
 Absorption of water
 Eliminates indigestible food from the
body as feces
 Does not participate in digestion of food
 Goblet cells produce mucus to act as a
lubricant
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Structures of the Large Intestine
 Cecum – saclike first part of the large
intestine
 Appendix
Accumulation of lymphatic tissue that
sometimes becomes inflamed
(appendicitis)
Hangs from the cecum
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Structures of the Large Intestine
 Colon
 Ascending
 Transverse
 Descending
 S-shaped sigmoidal
 Rectum
 Anus – external body opening
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Structures of the Large Intestine
 Colon
 Ascending
 Transverse
 Descending
 S-shaped sigmoidal
 Rectum
 Anus – external body opening
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Food Breakdown and Absorption in
the Large Intestine
 No digestive enzymes are produced
 Resident bacteria digest remaining
nutrients
 Produce some vitamin K and B
 Release gases
 Water and vitamins K and B are absorbed
 Remaining materials are eliminated via
feces
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Propulsion in the Large Intestine
 Sluggish peristalsis
 Mass movements
 Slow, powerful movements
 Occur three to four times per day
 Presence of feces in the rectum causes
a defecation reflex
 Internal anal sphincter is relaxed
 Defecation occurs with relaxation of the
voluntary (external) anal sphincter
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Accessory Digestive Organs
 Salivary glands
 Teeth
 Pancreas
 Liver
 Gall bladder
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Salivary Glands
 Saliva-producing glands
 Parotid glands – located anterior to ears
 Submandibular glands
 Sublingual glands
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Saliva
 Mixture of mucus and serous fluids
 Helps to form a food bolus
 Contains salivary amylase to begin
starch digestion
 Dissolves chemicals so they can be
tasted
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Teeth
 The role is to masticate (chew) food
 Humans have two sets of teeth
 Deciduous (baby or milk) teeth
 20 teeth are fully formed by age two
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Teeth
 Permanent teeth
 Replace deciduous teeth beginning
between the ages of 6 to 12
 A full set is 32 teeth, but some people do
not have wisdom teeth
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Classification of Teeth
 Incisors
 Canines
 Premolars
 Molars
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Classification of Teeth
Figure 14.9
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Regions of a Tooth
 Crown – exposed part
 Neck
 Region in contact with the
gum
 Connects crown to root
 Root
 Attached to the bone
 Root canal carrying blood
vessels and nerves
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Figure 14.10
Slide
Pancreas
 Produces a wide spectrum of digestive
enzymes that break down all categories of food
 Enzymes are secreted into the duodenum
 Alkaline fluid introduced with enzymes
neutralizes acidic chyme
 Endocrine products of pancreas
 Insulin
 Glucagons
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Liver
 Largest gland in the body
 Right side of the body under the
diaphragm
 Four lobes suspended from the
diaphragm
 Connected to the gall bladder via the
common hepatic duct
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Bile
 Produced by cells in the liver
 Composition
 Bile salts
 Bile pigment (mostly bilirubin from the
breakdown of hemoglobin)
 Cholesterol
 Phospholipids
 Electrolytes
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Role of the Liver in Metabolism
 Several roles in digestion
 Detoxifies drugs and alcohol
 Degrades hormones
 Produce cholesterol, blood proteins
(albumin and clotting proteins)
 Plays a central role in metabolism
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Gall Bladder
 Sac found in hollow fossa of liver
 Stores bile from the liver by way of the
cystic duct
 Bile is introduced into the duodenum in
the presence of fatty food
 Gallstones can cause blockages
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Processes of the Digestive System
 Ingestion – getting food into the mouth
 Propulsion – moving foods from one
region of the digestive system to
another
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Processes of the Digestive System
 Peristalsis – alternating
waves of contraction
 Segmentation – moving
materials back and forth
to aid in mixing
Figure 14.12
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Processes of the Digestive System
 Mechanical digestion
 Mixing of food in the mouth by the tongue
 Churning of food in the stomach
 Segmentation in the small intestine
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Processes of the Digestive System
 Chemical Digestion
 Enzymes break down food molecules into
their building blocks
 Each major food group uses different
enzymes
 Carbohydrates - simple sugars
 Proteins - amino acids
 Fats - fatty acids and alcohols
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Processes of the Digestive System
 Absorption
 End products of digestion are absorbed in
the blood or lymph
 Food must enter mucosal cells and then
into blood or lymph capillaries
 Defecation
 Elimination of indigestible substances as
feces
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Processes of the Digestive System
Figure 14.11
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Control of Digestive Activity
 Mostly controlled by reflexes via the
parasympathetic division
 Chemical and mechanical receptors are
located in organ walls that trigger
reflexes
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Control of Digestive Activity
 Stimuli include:
 Stretch of the organ
 pH of the contents
 Presence of breakdown products
 Reflexes include:
 Activation or inhibition of glandular
secretions
 Smooth muscle activity
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Nutrition - Take a Class!
 Nutrient – substance used by the body for
growth, maintenance, and repair
 Categories of nutrients
 Carbohydrates: simple sugars, starches, fiber
 Lipids: triglycerides, phospholipids, fatty acids
 Proteins: amino acids
 Vitamins
 Mineral
 Water
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Body Energy Balance
 Energy intake = total energy output
(heat + work + energy storage)
 Energy intake is liberated during food
oxidation
 Energy output
 Heat is usually about 60%
 Storage energy is in the form of fat or
glycogen
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Essentials of Human Anatomy & Physiology
Elaine N. Marieb
Seventh Edition
Chapter 15
The Urinary System
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Functions of the Urinary System
 Elimination of waste products
 Nitrogenous wastes
 Toxins
 Drugs
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Functions of the Urinary System
 Regulate aspects of homeostasis
 Water balance
 Electrolytes
 Acid-base balance in the blood
 Blood pressure
 Red blood cell production
 Activation of vitamin D
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Organs of the Urinary system
 Kidneys
 Ureters
 Urinary bladder
 Urethra
Figure 15.1a
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Slide 15.2
Location of the Kidneys
 Against the dorsal body wall
 At the level of T12 to L3
 Right kidney is slightly lower
 Attached to ureters, renal blood vessels,
and nerves at renal hilus
 Atop each kidney is an adrenal gland
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Slide 15.3
Coverings of the Kidneys
 Renal capsule
 Surrounds each kidney
 Adipose capsule
 Surrounds the kidney
 Provides protection to the kidney
 Helps keep the kidney in its correct location
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Slide 15.4
Regions of the Kidney
 Renal cortex –
outer region
 Renal medulla –
inside the cortex
 Renal pelvis –
inner collecting
tube
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Figure 15.2b
Slide 15.5
Kidney Structures
 Medullary pyramids –
triangular regions in
the medulla
 Renal columns –
extensions of cortexlike material inward
 Calyces – cupshaped structures;
funnel urine towards
renal pelvis
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Slide 15.6
Blood Flow in the Kidneys
Figure 15.2c
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Slide 15.7
Nephrons
 The structural and functional units of the
kidneys
 Responsible for forming urine
 Main structures of the nephrons
 Glomerulus
 Renal tubule
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Slide 15.8
Glomerulus
 A specialized
capillary bed
 Attached to
arterioles on both sides
(maintains
high pressure)
Sits within a capsule
Figure 15.3c
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Renal Tubule
 Glomerular
(Bowman’s)
capsule
 Proximal
convoluted
tubule
 Loop of Henle
 Distal
convoluted
tubule
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Figure 15.3b
Slide
Types of Nephrons
 Cortical nephrons
 Located entirely in the cortex
 Includes most nephrons
Figure 15.3a
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Types of Nephrons
 Juxtamedullary nephrons
 Found at the boundary of the cortex and
medulla
Figure 15.3a
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Peritubular Capillaries
 Arise from efferent arteriole of the
glomerulus
 Normal, low pressure capillaries
 Attached to a venule
 Cling close to the renal tubule
 Reabsorb (reclaim) some substances
from collecting tubes
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Urine Formation Processes
1. Filtration
2. Reabsorption
3. Secretion
Figure 15.4
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Filtration
 Nonselective passive process
 Water and solutes smaller than proteins
are forced through capillary walls
 Blood cells cannot pass out to the
capillaries
 Filtrate is collected in the glomerular
capsule and leaves via the renal tubule
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Reabsorption
 The peritubular capillaries reabsorb several
materials
 Some water
 Glucose
 Amino acids
 Ions
 Some reabsorption is passive, most is active
 Most reabsorption occurs in the proximal
convoluted tubule
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Materials Not Reabsorbed
 Nitrogenous waste products
 Urea
 Uric acid
 Creatinine
 Excess water
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Secretion – Reabsorption in
Reverse
 Some materials move from the
peritubular capillaries into the renal
tubules
 Hydrogen and potassium ions
 Creatinine
 Materials left in the renal tubule move
toward the ureter
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Formation of Urine
Figure 15.5
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Characteristics of Urine Used for
Medical Diagnosis
 Colored somewhat yellow due to the
pigment urochrome (from the
destruction of hemoglobin) and solutes
 Sterile
 Slightly aromatic
 Normal pH of around 6 (varies 4.5-8)
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Ureters
 Slender tubes attaching the kidney to
the bladder
 Continuous with the renal pelvis
 Enter the posterior aspect of the bladder
 Runs behind the peritoneum
 Peristalsis aids gravity in urine transport
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Urinary Bladder
 Smooth, collapsible, muscular sac
 Temporarily stores urine
Figure 15.6
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Urinary Bladder
 Trigone – three openings
 Two from the ureters
 One to the urethrea
Figure 15.6
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Urinary Bladder Wall
 Three layers of smooth muscle
(detrusor muscle)
 Mucosa made of transitional epithelium
 Walls are thick and folded in an empty
bladder
 Bladder can expand significantly without
increasing internal pressure
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Urethra
 Thin-walled tube that carries urine from
the bladder to the outside of the body by
peristalsis
 Release of urine is controlled by two
sphincters
 Internal urethral sphincter (involuntary)
 External urethral sphincter (voluntary)
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Urethra Gender Differences
 Length
 Females – 3–4 cm (1 inch)
 Males – 20 cm (8 inches)
 Location
 Females – along wall of the vagina
 Males – through the prostate and penis
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Urethra Gender Differences
 Function
 Females – only carries urine
 Males – carries urine and is a passageway
for sperm cells
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Micturition (Voiding)
 Both sphincter muscles must open to
allow voiding (emptying the bladder)
 Internal urethral sphincter relaxes due to
stretched bladder
 Activation required by nerve impulse
 External urethral sphincter must be
voluntarily relaxed
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Maintaining Water Balance
 Normal amount of water in the human
body
 Young adult females – 50%
 Young adult males – 60%
 Babies – 75%
 Old age – 45%
 Water is necessary for many body
functions and levels must be maintained
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Distribution of Body Fluid
 Intracellular fluid
(inside cells)
 Extracellular
fluid (outside
cells)
 Interstitial fluid
 Blood plasma
Figure 15.7
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The Link Between Water and Salt
 Changes in electrolyte balance causes
water to move from one compartment to
another
 Alters blood volume and blood pressure
 Can impair the activity of cells
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Maintaining Water Balance
 Water intake must equal water output
 Sources for water intake
 Ingested foods and fluids
 Water produced from metabolic processes
 Sources for water output
 Vaporization out of the lungs
 Lost in perspiration
 Leaves the body in the feces
 Urine production
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Maintaining Water Balance
 Dilute urine is produced if water intake
is excessive
 Less urine (concentrated) is produced if
large amounts of water are lost
 Proper concentrations of various
electrolytes must be present
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Regulation of Water and Electrolyte
Reabsorption
 Regulation is primarily by hormones
 Antidiuretic hormone (ADH) prevents
excessive water loss in urine
 Aldosterone regulates sodium ion content of
extracellular fluid
 Cells in the kidneys and hypothalamus
are active monitors
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Maintaining Water/Electrolyte Balance
Figure 15.9
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Maintaining Acid-Base Balance in
Blood
 Blood pH must remain between 7.35
and 7.45 to maintain homeostasis
 Alkalosis – pH above 7.45
 Acidosis – pH below 7.35
 Most ions originate as byproducts of
cellular metabolism
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Maintaining Acid-Base Balance in
Blood
 Most acid-base balance is maintained
by the kidneys
 Other acid-base controlling systems
 Blood buffers
 Respiration
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Blood Buffers
 Molecules react to prevent dramatic
changes in hydrogen ion (H+)
concentrations
 Bind to H+ when pH drops
 Release H+ when pH rises
 Three major chemical buffer systems
 Bicarbonate buffer system
 Phosphate buffer system
 Protein buffer system
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Developmental Aspects of the
Urinary System
 Functional kidneys are developed by
the third month
 Urinary system of a newborn
 Bladder is small
 Urine cannot be concentrated
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Developmental Aspects of the
Urinary System
 Control of the voluntary urethral
sphincter does not start until age 18
months
 Urinary infections are the only common
problems before old age
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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Aging and the Urinary System
 There is a progressive decline in urinary
function
 The bladder shrinks with aging
 Urinary retention is common in males
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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