Post on 13-Jan-2016
Chapter 17The Urinary System
Structures we’ll talk about tonight…
•Kidneys•Ureters•Bladder•Urethra
KidneysLocation—under back muscles, behind
parietal peritoneum, just above waistline; right kidney usually a little lower than left
Internal structure Renal cortex—outer layer of kidney substanceRenal medulla—inner portion of kidneyRenal pyramids—triangular divisions of medullaRenal papilla—narrow, innermost end of
pyramid
KidneysRenal Microscopic structure—nephrons are
microscopic units of kidneysThey help with the formation of urine
Cortical nephrons—85% of totalJuxtamedullary nephrons—specialized role in
concentrating urineThey consist of:
Bowman’s capsule—the cup-shaped topGlomerulus—network of blood capillaries
surrounded by Bowman’s capsule
KidneysNephron parts continued:
Proximal convoluted tubule—first segmentLoop 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
What are the functions of the kidneys?
What happens when you only have 1?
KidneysFunctions
Excretes toxins and nitrogenous wastesRegulates levels of many chemicals in bloodMaintains water balanceHelps regulate blood pressure
Not much changes when you only have 1 kidney!
Formation of Urine Occurs by a series of three processes that
take place in successive parts of nephronFiltration—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
Formation of Urine 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
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
Formation of UrineControl of urine volume –
Antidiuretic hormone (ADH) = “water-retaining hormone” or “urine-decreasing hormone”
Aldoesterone = “salt- and water-retaining hormone”
Atrial natriuretic hormone (ANH) = opposite effect of aldosterone
Influence of water on urine productionPredict the
changes that would occur in the urine of a runner who had just completed a marathon.
Predict the changes that would occur in the urine production of a person who just ate a jumbo bag of popcorn with extra salt.
Practical ApplicationMarathon runner Bag of salty popcornProteinuria will
probably occurProbably dehydratedUrine production less
than normalSalt loss via sweat –
impact on hormone production?
What if they drank a lot of water during the marathon? Sports drinks?
Decreased salt reabsorption with the greatly increased salt intake.
Larger amount of salt excreted through the urine.
What urine can tell usUrinalysis—examination of the physical,
chemical, and microscopic characteristics of urine; may help determine the presence and nature of a pathological condition
What sort of info can we obtain in doing a urinalysis?
Ureters Structure—narrow long tubes with expanded
upper end (renal pelvis) located inside kidney and lined with mucous membrane and muscular layer
Function—drain urine from renal pelvis to urinary bladder
Urinary BladderStructure
Elastic muscular organ, capable of great expansion
Lined with mucous membrane arranged in rugae, like stomach mucosa
FunctionsStorage of urine before voidingVoiding
UrethraStructure
Narrow tube from urinary bladder to exteriorLined with mucous membraneOpening of urethra to the exterior called urinary
meatusFunctions
Passage of urine from bladder to exterior of the body
Passage of male reproductive fluid (semen) from the body
MicturitionPassage of urine from body (also called
urination or voiding)Regulatory sphincters
Internal urethral sphincter (involuntary)External urethral sphincter (voluntary)
Bladder wall permits storage of urine with little increase in pressure
MicturitionEmptying reflex
Initiated by stretch reflex in bladder wallBladder wall contractsInternal sphincter relaxesExternal sphincter relaxes, and urinationEnuresis—involuntary urination in young child
MicturitionUrinary retention—urine produced but not
voidedUrinary suppression—no urine produced but
bladder is normalIncontinence—urine is voided involuntarily
May be caused by spinal injury or strokeNeurogenic bladder—paralysis or abnormal function of
the bladder, preventing normal flow of urine out of the body
Types include urge, stress, and reflex
Renal and Urinary DisordersObstructive disorders interfere with normal
urine flow, possibly causing urine to back up and cause hydronephrosis or other kidney damageRenal calculi (kidney stones) may block ureters,
causing intense pain called renal colicTumors—renal cell carcinoma (kidney cancer)
and bladder cancer are often characterized by hematuria (blood in the urine)
Renal and Urinary DisordersUrinary tract infections (UTIs) are often
caused by gram-negative bacteriaUrethritis—inflammation of the urethraCystitis—inflammation or infection of the urinary
bladderPyelonephritis—inflammation of the renal pelvis
and connective tissues of the kidney; may be acute (infectious) or chronic (autoimmune)
Hydronephrosis—enlargement of renal pelvis and calyces
Renal and Urinary DisordersGlomerular disorders result from damage to
the glomerular–capsular membrane of the renal corpuscles
Nephrotic syndrome accompanies many glomerular disorders
Proteinuria—protein in the urineHypoalbuminemia—low plasma protein
(albumin) level; caused by loss of proteins to urine
Edema—tissue swelling caused by loss of water from plasma as a result of hypoalbuminemia
Renal and Urinary Disorders
Acute glomerulonephritis is caused by delayed immune response to a streptococcal infection
Chronic glomerulonephritis is a slow inflammatory condition caused by immune mechanisms and often leading to renal failure
Renal and Urinary DisordersKidney failure or renal failure occurs when the
kidney fails to functionAcute renal failure—abrupt reduction in kidney
function that is usually reversibleChronic renal failure—slow, progressive loss of
nephrons caused by a variety of underlying diseasesEarly in this disorder, healthy nephrons often
compensate for the loss of damaged nephrons
Renal and Urinary Disorders
Loss of kidney function ultimately results in uremia (high BUN levels) and its life-threatening consequences
Complete kidney failure results in death unless a new kidney is transplanted or an artificial kidney substitute is used