urinary system.ppt

Functions of the Urinary System
Slide
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Elimination of waste products
Nitrogenous wastes
Toxins
Drugs

Functions of the Urinary System
Slide
 Regulate aspects of homeostasis
Water balance
Electrolytes
Acid-base balance in the blood
Blood pressure
Red blood cell production
Activation of vitamin D

Organs of the Urinary system
Slide 15.2
 Kidneys
 Ureters
 Urinary bladder
 Urethra
Figure 15.1a

Location of the Kidneys
Slide 15.3
 Against the dorsal body wall
 At the level of T12 to L3
 The right kidney is slightly lower than
the left
 Attached to ureters, renal blood vessels,
and nerves at renal hilus
 Atop each kidney is an adrenal gland

Coverings of the Kidneys
Slide 15.4
 Renal capsule
Surrounds each kidney
 Adipose capsule
Surrounds the kidney
Provides protection to the kidney
Helps keep the kidney in its correct location

Regions of the Kidney
Slide 15.5
 Renal cortex –
outer region
 Renal medulla –
inside the cortex
 Renal pelvis –
inner collecting
tube
Figure 15.2b

Kidney Structures
Slide 15.6
 Medullary pyramids – triangular regions
of tissue in the medulla
 Renal columns – extensions of cortex-
like material inward
 Calyces – cup-shaped structures that
funnel urine towards the renal pelvis

Blood Flow in the Kidneys
Slide 15.7
Figure 15.2c

Nephrons
Slide 15.8
 The structural and functional units of the
kidneys
 Responsible for forming urine
 Main structures of the nephrons
Glomerulus
Renal tubule

Glomerulus
Slide
 A specialized
capillary bed
 Attached to
arterioles on both
sides (maintains
high pressure)
Large afferent
arteriole
Narrow efferent
arteriole Figure 15.3c

Glomerulus
Slide
 The glomerulus
sits within a
glomerular capsule
(the first part of the
renal tubule)
Figure 15.3c

Renal Tubule
Slide
 Glomerular
(Bowman’s)
capsule
 Proximal
convoluted
tubule
 Loop of Henle
 Distal
convoluted
tubule
Figure 15.3b

Types of Nephrons
Slide
 Cortical nephrons
Located entirely in the cortex
Includes most nephrons
Figure 15.3a

Types of Nephrons
Slide
 Juxtamedullary nephrons
Found at the boundary of the cortex and
medulla
Figure 15.3a

Peritubular Capillaries
Slide
 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

Urine Formation Processes
Slide
 Filtration
 Reabsorption
 Secretion
Figure 15.4

Filtration
Slide
 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

Reabsorption
Slide
 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

Materials Not Reabsorbed
Slide
 Nitrogenous waste products
Urea
Uric acid
Creatinine
 Excess water

Secretion – Reabsorption in
Reverse
Slide
 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

Formation of Urine
Slide
Figure 15.5

Ureters
Slide
 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

Urinary Bladder
Slide
 Smooth, collapsible, muscular sac
 Temporarily stores urine
Figure 15.6

Urinary Bladder
Slide
 Trigone – three openings
Two from the ureters
One to the urethrea
Figure 15.6

Urinary Bladder Wall
Slide
 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

Urethra
Slide
 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)

Urethra Gender Differences
Slide
 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

Urethra Gender Differences
Slide
 Function
Females – only carries urine
Males – carries urine and is a passageway
for sperm cells

Micturition (Voiding)
Slide
 Both sphincter muscles must open to
allow voiding
The internal urethral sphincter is relaxed
after stretching of the bladder
Activation is from an impulse sent to the
spinal cord and then back via the pelvic
splanchnic nerves
The external urethral sphincter must be
voluntarily relaxed

Maintaining Water Balance
Slide
 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

Distribution of Body Fluid
Slide
 Intracellular fluid
(inside cells)
 Extracellular
fluid (outside
cells)
Interstitial fluid
Blood plasma
Figure 15.7

The Link Between Water and Salt
Slide
 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

Slide
 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

Slide
 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

Regulation of Water and Electrolyte
Reabsorption
Slide
 Regulation is primarily by hormones
Antidiuretic hormone (ADH) prevents
excessive water loss in urine
Aldosterone regulates sodium ion content of
extracellular fluid
 Triggered by the rennin-angiotensin
mechanism
 Cells in the kidneys and hypothalamus
are active monitors

Maintaining Acid-Base Balance in
Blood
Slide
 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

Maintaining Acid-Base Balance in
Blood
Slide
 Most acid-base balance is maintained
by the kidneys
 Other acid-base controlling systems
Blood buffers
Respiration

Blood Buffers
Slide
 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

The Bicarbonate Buffer System
Slide
 Mixture of carbonic acid (H2CO3) and
sodium bicarbonate (NaHCO3)
 Bicarbonate ions (HCO3
–) react with
strong acids to change them to weak
acids
 Carbonic acid dissociates in the presence
of a strong base to form a weak base and
water

Respiratory System Controls of
Acid-Base Balance
Slide
 Carbon dioxide in the blood is converted to
bicarbonate ion and transported in the
plasma
 Increases in hydrogen ion concentration
produces more carbonic acid
 Excess hydrogen ion can be blown off with
the release of carbon dioxide from the lungs
 Respiratory rate can rise and fall depending
on changing blood pH

Renal Mechanisms of Acid-Base
Balance
Slide
 Excrete bicarbonate ions if needed
 Conserve or generate new bicarbonate
ions if needed
 Urine pH varies from 4.5 to 8.0

Developmental Aspects of the
Urinary System
Slide
 Functional kidneys are developed by
the third month
 Urinary system of a newborn
Bladder is small
Urine cannot be concentrated

Developmental Aspects of the
Urinary System
Slide
 Control of the voluntary urethral
sphincter does not start until age 18
months
 Urinary infections are the only common
problems before old age

Aging and the Urinary System
Slide
 There is a progressive decline in urinary
function
 The bladder shrinks with aging
 Urinary retention is common in males

urinary system.ppt

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