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HS130: Anatomy and Physiology II
Unit 7 Seminar:
The Urinary System
Dr. Daudi K. Langat
Adjunct Professor, Kaplan University
Welcome to today’s Seminar! We will
begin at the top of the hour.
Housekeeping issues
(Unit 9 Writing Assignment)
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A reminder that the Unit 9 Assignment due date is coming up soon (it is
worth 100 points!)
You will continue with your voyage. Your “Fantastic Voyage!” is continuing
inside a 55 year old man eating a hamburger, french fries and a root beer.
You go through the following systems:
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Digestive tract to review the digestion to completion
Absorption at the distal ilieum to the superior mesenteric Vein.
Urinary system, to the left kidney (trace your path from the superior mesenteric
vein to the left renal artery, via the hepatic portal vein, heart and lungs
Go into the nephron and follow the urinary pathway to the outside
Wrap up your report by explaining the integration of the body systems in
maintaining homeostasis. You must include at least the circulatory, digestive and
urinary systems in your explanation.
References should be in APA format. Review the other PowerPoint entitled
“APA Style Formatting” for more information.
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Instructions for Unit 9 Assignment
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APA Formatting
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Seminar Topic:
This week we will discuss the major components of the
urinary system and the formation of urine.
Chapter 17
The Urinary System
KIDNEYS
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Location—under back muscles, behind parietal
peritoneum, just above waistline; right kidney usually a little
lower than left.
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Kidney Internal structure
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Cortex —outer layer of kidney substance
Medulla—inner portion of kidney
Pyramids —triangular divisions of medulla
Papilla —narrow, innermost end of pyramid
Pelvis —expansion of upper end of ureter; lies inside kidney
Calyces —divisions of renal pelvis
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KIDNEYS
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Microscopic structure—nephrons are microscopic units of
kidneys; consist of the following (Figure 17-3):
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Renal corpuscle
• Bowman’s capsule —the cup-shaped top
• Glomerulus —network of blood capillaries surrounded by Bowman’s
capsule
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Renal tubule
• Proximal convoluted tubule —first segment
• Loop of Henle —extension of proximal tubule; consists of descending
limb, loop, and ascending limb
• Distal convoluted tubule —extension of ascending limb of loop of
Henle
• Collecting tubule —straight extension of distal tubule
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KIDNEYS
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Functions
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Excretes toxins and nitrogenous wastes
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Regulates levels of many chemicals in blood
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Maintains water balance
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Helps regulate blood pressure via secretion of renin
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FORMATION OF URINE
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Occurs by a series of three processes that take place in successive
parts of nephron
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Filtration —goes on continually in renal corpuscles; glomerular blood
pressure causes water and dissolved substances to filter out of glomeruli
into Bowman’s capsule; normal glomerular filtration rate 125 mL per
minute
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Reabsorption —movement of substances out of renal tubules into blood
in peritubular capillaries; water, nutrients, and ions are reabsorbed; water
is reabsorbed by osmosis from proximal tubules
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Secretion —movement of substances into urine in the distal and
collecting tubules from blood in peritubular capillaries; hydrogen ions,
potassium ions, and certain drugs are secreted by active transport;
ammonia is secreted by diffusion
Control of urine volume —mainly by posterior pituitary hormone’s
ADH, which decreases it
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Formation of urine
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Functions of the Nephron Components
PART
FUNCTION
Renal Corpuscle
• Filtration of water and dissolved substances from the plasma
• Receives the glomerular filtrate
Glomerulus
Renal tubule
Proximal convoluted tubule
• Reabsorption of glucose, amino acids, creatinine, lactic, citric, uric and
ascorbic acids, PO42-, SO42-, Ca2+, K+, Na+ ions by active transport.
• Reabsorption of proteins by pinocytosis
• Reabsorption of water by osmosis
• Reabsorption of chloride ions and other negatively charged ions by
electrochemical attraction
• Active secretion of substances such as penicillin, histamine, creatinine
and hydrogen ions
Descending limb of the
nephron loop
• Reabsorption of water by osmosis
Ascending limb of nephron
loop
• Reabsorption of Na+, K+, Cl- ions by active transport
Distal convoluted tubule
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Collecting duct
• Reabsorption of water by osmosis
Reabsorption of Na+ ions by active transport
Reabsorption of water by osmosis
Active secretion of hydrogen ions
Secretion of K+ ions both actively and by electrochemical attraction
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URETERS
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Structure —narrow, long tubes with
expanded upper end (renal pelvis) located
inside kidney and lined with mucous
membrane
Function—drain urine from renal pelvis to
urinary bladder
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URINARY BLADDER
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Structure (Figure 17-7)
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Elastic muscular organ, capable of great expansion
 Lined with mucous membrane arranged in rugae, as is
stomach mucosa
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Functions
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Storage of urine before voiding
Voiding
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URETHRA
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Structure
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Narrow tube from urinary bladder to exterior
Lined with mucous membrane
Opening of urethra to the exterior called
urinary meatus
Functions
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Passage of urine from bladder to exterior of the
body
Passage of male reproductive fluid (semen)
from the body
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Comparison of male and female urinary
systems
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MICTURITION
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Passage of urine from body (also called urination or
voiding)
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Regulatory sphincters
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Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)
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Bladder wall permits storage of urine with little increase in
pressure
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Emptying reflex
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Initiated by stretch reflex in bladder wall
Bladder wall contracts
Internal sphincter relaxes
External sphincter relaxes, and urination occurs
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PROBLEMS WITH MICTURITION
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Urinary retention —urine produced but not
voided
Urinary suppression —no urine produced but
bladder is normal
Incontinence —urine is voided involuntarily
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May be caused by spinal injury or stroke
Retention of urine may cause cystitis
Cystitis —bladder infection
Overactive bladder —need for frequent urination
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Called interstitial cystitis
Amounts voided are small
Extreme urgency and pain are common
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Major Disorders of the Urinary System
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Hydronephrosis
Calculi (stones)
Neurogenic bladder
Tumors
Urethritis
Infection
 Cystitis
 Pyelonephritis
Renal Failure
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GOODNIGHT EVERYBODY!!
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