1. Urinary System
Presented By: Milani, Mandeep, Karthiga, Gladyz, Elisa

2. KIDNEYS-Location and Structure
 Although many believe that the kidneys are located in the lower back, this
is not their location.
 These small, dark red organs with a kidney bean shape lie against the
dorsal body wall in a retroperitoneal position (beneath the parietal
peritoneum) in the superior lumbar region.
 The kidneys extend from the T12 to the L3 vertebra; thus they receive
some protection from the lower part of the rib cage.
 Because it is crowded by the liver, the right kidney is positioned slightly
lower than the left.
 It is convex laterally and has a medial indentation called the renal hilus.
 Atop each kidney is an adrenal gland, which is part of the endocrine
system and is a distinctly separate organ functionally.
 A fibrous, transparent renal capsule encloses each kidney and gives a
fresh kidney a glistening appearance.
 The adipose capsule, surrounds each kidney and helps hold it in place
against the muscles of the trunk wall.

3.  When a kidney is cut lengthwise,
three distinct regions become
apparent, as can be seen in this
picture.
 The outer region, which is light in
color, is the renal cortex.
 Deep to the cortex is a darker
reddish-brown area, the renal
medulla.
 The broader base of each pyramid
faces toward the cortex; its tip, the
apex, points toward the inner
region of the kidney.
 The pyramids are separated by
extensions of cortex like tissue,
the renal columns.

4.  Medial to the hilus is a flat,
basinklike cavity, the renal pelvis
 Pelvis is continuous with the ureter
leaving the hilus.
 Extension of the pelvis, calyces
(calyx), form cup-shaped areas
that enclose the tips of the
pyramids.
 The calyces collect urine, which
continuously drains from the tips
of the pyramids into the renal
pelvis.
 Urine then flows from the pelvis
into the ureter, which transport it
to the bladder for temporary
storage.

5. Blood supply
 The kidneys continuously cleanse
the blood and adjust its
composition, so it is not surprising
that they have a very rich blood
supply
 One-quarter of the total blood
supply of the body passes through
the kidneys each minute.

6.  The arterial supply of each kidney
is the renal artery
 As the renal artery approaches the
hilus, it divides into Segmental
arteries.
 Once in side the pelvis, the
segmental arteries break up into
lobar arteries
 Each of which gives off several
branches called interlobar
arteries then branch off the
arcuate arteries and run outward
to supply the cortical tissue.
 The venous blood draining from
the kidney flows through veins that
trace the pathway of the arterial
supply but in a reverse direction-
interlobular veins to arcuate
veins to interlobar veins to the
renal vein, which emerges from
the kidney hilus

7. Nephrons and Urine Formation
 Each kidney contains over a
million tiny structures called
nephrons.
 Nephrons are the structural and
functional units of the kidneys
and, as such, are responsible for
forming urine.
 Each nephron consists of two
main structures: a glomerulus,
which is a knot of capillaries, and
a renal tubule.
 The cup- shaped of the renal
tubule is called the glomerular, or
Bowman’s, capsule.
 The inner layer of the capsule is
made up of highly modified
octopus- like cells called
podocytes

8.  Extends from the glomerular
capsule, it coils and twists before
forming a hairpin loops and then
again becomes coiled and twisted
before entering a collecting tubule
called the collecting duct.
(these different regions of the
tubule have specific names)
 These different regions of the
tubule have specific names.
 Most nephrons are called cortical
nephrons because they are
located almost entirely within the
cortex.
 The collecting ducts, each of
which receives urine from many
nephrons, run downward through
the medullary pyramids, giving
them their striped appearance.

9.  The afferent arteriole, which arises
from an interlobular artery, is the
“feeder vessel,” and the efferent
arteriole receives blood that has
passed through the glomerulus.
 The glomerulus, specialized for
filtration, is unlike any other capillary
bed in the entire body.
 The second capillary bed, the
peritubular capillaries, arises from
the efferent arteriole that drain the
glomerulus.
 Unlike the high-pressure glomerulus,
these capillaries are low- pressure,
porous vessels that are adapted for
absorption instead of filtration.
 The peritubular capillaries drain into
interlobular veins leaving the cortex.

10. Urine Formation
 It is a result of three processes:
 FILTRATION
 TUBULAR REABSORPTION
 TUBULAR SECRETION

11. Filtration
 Glomerulus Acts as a Filter
 Water and solutes smaller than proteins are forced through the capillary walls
and pores of the glomerular capsule into the renal tubule.
 Both proteins and blood cells normally too large to pass through the filtration
membrane and when either one of these appear in urine it is evident there is
a problem with the glomerular filters

12. Con’t
 Also, systemic blood pressure has to be normal in order for filtration to
happen
 If the arterial blood pressure falls too low, the glomerular pressure becomes
inadequate to force substances out of the blood and into the tubules, and
filtrate formation stops

13. Homeostatic Imbalance
 Oliguria: an abnormal low urinary output if it is between 100 and 400 ml/day
 Anuria if it is less than 100ml/day
 Low urinary output indicates that glomerural blood pressure is too low to
cause filtration
 However, Anuria may also result from transfusion reactions and acute
inflammation or from crush injuries of the kidneys

14. Con’t
 Blood from afferent arteriole flows into the glomerulus (capillaries)
 Due to blood pressure in the glomerulus, filtration occurs
 Water and small molecules (such as salts, amino acids, urea, uric acid,
glucose) move from the blood plasma into the capsule
 Small molecules that escape being filtered and the nonfilterable components
leave the glomerulus by the Efferent arteriole
 This produces a filtrate of blood, called glomerular filtrate

15. Filterable Blood Nonfilterable Blood
Components Components
 Water  Formed elements (blood cells and
 Nutrients platelets)
 Salts  Plasma Proteins
 Ions
 Nitrogenous Waste

16. Tubular Reabsorption
 As the filtrate moves along the tubule some of the molecules and ions are
actively and passively (by diffusion) reabsorbed into the capillary bed from
the tubule
 Active transport: transport of molecules against a concentration gradient
(from regions of low concentration to regions of high concentrations) with the
aid of proteins in the cell membrane and energy from ATP

17. Con’t
 About 99% of filtered water and many useful molecules (such as salts, urea,
nutrients, glucose, amino acids, sodium Ion Na+, chloride ion Cl-) returned
to the blood
 Reabsorption of water is by osmosis
 Most of the reabsorption occurs in the proximal convoluted tubules, but the
distal and the collecting duct are also active

18. Tubular Secretion
 More substances such as ions (hydrogen ion, creatinine, some drugs
(penicillin), toxic substances, are actively secreted from the capillary network
to tubules
 The fluid (urine), from filtration that was not reabsorbed and from tubular
secretion, then flows into the collecting duct, then renal pelvis
 Substances found in urine are water, salts, urea, uric acid, ammonia,
creatinine (NOT large molecules (proteins, blood cells), glucose
 Also, if all those substances weren't reabsorbed by tubules (glucose, water,
salts, urea) than the body would continually lose water, salt and nutrients

20. Characteristics of Urine
 Nephrons filter 125 ml of body fluid per minute; filtering the entire body fluid
component 16 times each day
 In a 24 hour period nephrons produce 180 liters of filtrate, of which 178.5
liters are reabsorbed.
 The remaining 1.5 liters forms urine

21. Con’t
 Freshly voided urine is generally clear and pale to deep yellow
 The more solutes are in a urine, the deeper yellow its color; whereas dilute
urine is a pale, straw color
 When formed, urine is sterile, and its odor is slightly aromatic
 Ph is slightly acid (around 6)
 Urine weight more than distilled water (because it has water plus solutes)

22. Ureters
•It is a slender tube each 25-30 cm long
and 6mm in diameter
•Each tube descends beneath the
peritoneum, from the hilum of a kidney,
to enter the bladder at its dorsal surface

23. Con’t
 The ureters is a passageway that carry urine from the kidneys to the bladder
 Although it may seem like urine may drain to the bladder by gravity, but the
ureters do play an active role in urine transport
 Smooth muscle layers in their walls contract to propel urine into the bladder
by peristalsis (even if a person is laying down)
 Once urine has entered the bladder, it is prevented from flowing back into the
ureters by small valvelike folds of bladder mucosa that flap over the ureter
openings

24. Homeostatic Imbalance
 When urine becomes extremely concentrated, solutes such as uric acid salts
form crystals that precipitate in the renal pelvis
 These crystals are called renal calculi, or kidney stones
 The crystals may grow into a stone ranging in size from a grain of sand to a
golf ball. Most stones form in the kidneys.
 Very small stones can pass through the urinary system without causing
problems. However, larger stones, when traveling from the kidney through
the ureter to the bladder, can cause severe pain called colic.
 Most stones (70 to 80 percent) are made of calcium oxalate. A smaller
number are made of uric acid or cystine

25. Con’t
 For treatment, surgery is a choice
 However, a newer noninvasive procedure (lithotripsy) may be used
 Uses ultrasound waves to break the stones into small fragments (about the
size of grain of sand)
 They then can be eliminated painlessly in the urine

26. Urinary Bladder
 The urinary bladder stores urine until it is expelled from the body
 The bladder is located in the pelvic cavity, behind the public symphysis and
beneath the peritoneum
 The bladder has three openings---two for the ureters and one for the
urethra, which drains the bladder

27. Con’t
 The smooth triangular region of the bladder base outlined by these three
openings is called the tridone
 The trigone is important clinically because infections tend to persist in this
region
 In males the prostate gland surrounds the neck of the bladder were it empties
into the urethra
 The bladder wall contains three layers of smooth muscle called the detrusor
muscle and its mucosa is a special type of epithelium: transitional epithelium
 When the bladder is empty it is collapsed, 5-7.5 cm long at most and its walls
are thick and thrown into folds

28. Con’t
 As urine accumulates, the bladder expands and rises superiorly in the
abdominal cavity Fig 15.7
 Its muscle wall stretches and the transitional epithelial layer thins, allowing
the balder to store more urine without substantially increasing its internal
pressure
 A full bladder is about 12.5 cm long and hold about 500 ml of urine, but it is
capable of holding more than twice that amount
 When the bladder is really distended, or stretched by urine, it becomes firm
and pear shaped and may be felt just above the public symphysis
 Although urine is formed continuously by the kidneys, it is usually stored in
the bladder until its release is convenient

29. Urethra

30. The anatomy of the urethra
 The epithelium of the
urethra starts off as
transitional cells as it exits
the bladder. Further along
the urethra there are
stratified columnar cells,
then stratified squamous
cells near the
external meatus (exit hole).
 There are small mucus-
secreting urethral glands,
that help protect the
epithelium from the
corrosive urine

31. The female urethra
 Female urethra
 In the human female, the urethra is
about 1 1/2-2 inches (3-5 cm)
long and opens in the vulva
between the clitoris and the vaginal
opening.
 Because of the short length of the
urethra, women tend to be more
susceptible to infections of the
bladder (cystitis) and the urinary
tract.

32. 
 The female urethra is a narrow
membranous canal, extending
from the internal to the external
urethral orifice.
 It is placed behind the symphysis
pubis, imbedded in the anterior
wall of the vagina, and its direction
is obliquely downward and
forward; it is slightly curved with
the concavity directed forward.
 Its lining is composed of stratified
squamous epithelium, which
becomes transitional near the
bladder.
 The urethra consists of three coats:
muscular, erectile, and mucous,
the muscular layer being a
continuation of that of the bladder.
 The release of urine is controlled
by two sphincters.
 Internal urethral sphincter
 External urethral sphincter

33. Male urethra
 The male urethra extends from the
internal urethral orifice in the urinary
bladder to the external urethral
orifice at the end of the penis.
 It presents a double curve in the
ordinary relaxed state of the penis.
 Its length varies from 17.5 to 20
cm.; and it is divided into three
portions, the prostatic,
membranous, and cavernous, the
structure and relations of which are
essentially different.
 Except during the passage of the
urine or semen, the greater part of
the urethral canal is a mere
transverse cleft or slit, with its upper
and under surfaces in contact; at the
external orifice the slit is vertical, in
the membranous portion irregular or
stellate, and in the prostatic portion
somewhat arched.

34.  1. The prostatic portion (pars
prostatica), the widest and most
dilatable part of the canal, is about
3 cm. long.
 2. The membranous portion
(pars membranacea) is the
shortest, least dilatable, and, with
the exception of the external
orifice, the narrowest part of the
canal It extends downward and
forward, with a slight anterior  3. The cavernous portion
concavity, between the apex of the (pars cavernosa; penile or
prostate and the bulb of the spongy portion) is the longest
urethra, perforating the urogenital part of the urethra, and is
diaphragm about 2.5 cm. below contained in the corpus
and behind the pubic symphysis. cavernosum urethræ. It is about
15 cm. long, and extends from
the termination of the
membranous portion to the
external urethral orifice.

35. The structure of the male urethra

The structure of the urethra (tube)  These muscle fibres are arranged
itself is a continuous mucous in a circular configuration that
membrane supported by separates the mucous membrane
submucous tissue connecting it and submucous tissue from the
to the other structures through surrounding structure - which is
which it passes. the tissue of the corpus
spongiosum (labeled simply "penis"
 The mucous coat is continuous in the diagram above).
with the mucous membrane of the
bladder, ureters and kidney. In the  Unlike the female urethra, the male
membranous and spongy sections urethra has a reproductive function
(2. and 3. above), the mucous in addition to it's urinary function -
membrane is arranged in it conveys semen out of the body
longitudinal folds when the tube is at ejaculation. For further
empty. information about this function red
the section about the male
 The submucous tissue consists reproductive system.
of a vascular (i.e. containing many
blood vessels) erectile layer
surrounded by a layer of smooth
(involuntary) muscle fibres.

36. The Function of the Urethra
 Gender differences:
 The females only carries urine.
 The males carries urine and is
a passageway for sperm cells.

37. Micturition of the urethra
Male and female
 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.

38. Fluid, Electrolyte, and Acid-Base
Balance
Blood composition depends on three major factors:
2. Diet
3. Cellular metabolism
4. Urine output
In general, the kidneys have four major roles to play, which help keep the blood
composition relatively constant.
7. Excretion of nitrogen containing wastes
8. Maintaining water in the blood
9. Maintaining electrolyte balance in the blood, and
10. Ensuring proper blood pH

39. Maintaining Water and Electrolyte Balance
of Blood
Body Fluids and Fluid Compartments:
Of the hundreds of compounds present in your body, the most abundant is
water.
Males weighing 154 pounds will have an average of 60% of their body weight,
nearly 40L, as water. Females about 50%. (based on nonobese individuals).
The more fat present in the body, the less total water content per kg of body
weight .
Female body contains slightly less water per kg of weight because it contains
slightly more fat than the male body.

40. In a newborn, water may account for up to 80% of body weight. That percentage
increases if the infant is born premature.
The percentage of body water decreases rapidly during the first 10 years of life.
In elderly individuals, the amount of water per kg of body weight increases
(because old ages is often accompanied by a decrease in muscle mass -65%
water- and in increase in fat -20% water-)
Water is the universal body solvent within which all solutes (including the very
important electrolytes) are dissolved.
*picture pg 619 body weight

41. Body Fluid Compartments:
Total body water can be subdivided into two major fluid compartments called
“extracellular” and “intracellular” fluid compartments.
Extracellular: consists mainly of the liquid fraction of whole blood called the
plasma, found in the blood vessels and the interstitial fluid that surrounds
the cell. In addition, lymph, cerebrospinal fluid, humors of the eye, and the
specialized joint fluids are also considered extracellular fluid.
Intracellular: largest volume of water by far. Located inside of the cells.
+diagram page 618

42. Mechanisms that maintain fluid
balance
3 sources of fluid intake: the liquids we drink, the water in the food we eat, and
the water formed by catabolism of foods.
Fluid output from the body occurs through four organs: the kidneys, lungs, skin,
and intestines. The fluid output that changes the most is that from the
kidneys.
The body maintains fluid balance mainly by changing the volume of urine
excreted to match changes in the volume of fluid intake

43. Regulation of Fluid Intake
When fluid loss from the body exceeds fluid intake, salivary excretion decreases,
producing a “dry mouth” feeling, and the sensation of thirst. The individual
then drinks water, thereby increasing fluid intake and compensating for
previous fluid losses. This tends to restore fluid balance.
Water is continually lost from the body through expired air and diffusion through
the skin.
Although the body adjusts fluid intake, factors that adjust fluid output, such as
electrolytes and blood proteins, are far more important.
 (chart from yellow text!!!)

44. Balance between
typical fluid
intake and output
in a 70 kg adult.
(Values are ml per
24 hours.)

45. What are electrolytes?
Electrolyte: substance that dissociates into ions in solution, rendering the
solution capable of conducting an electric current.
Electrolyte balance: homeostasis of electrolytes

46. The types and amounts of solutes in the body, especially electrolytes such as
sodium, potassium, and calcium ions, are vitally important to overall
homeostasis.
Very small changes in electrolyte balance (solute concentrations in various fluid
compartments) cause water to move from one fluid compartment to another.
This alters blood volume and blood pressure, but it can also severely impair
the activity of irritable cells like the nerve and muscle cell.
Chart from text book!

47. Importance of Electrolytes in Body Fluids
Compounds such as ordinary table salt, or sodium chloride (NaCl) that have
molecular bonds that permit them to break up, or dissociate, in water
solution to separate particles (Na+ and Cl-) are electrolytes. The dissociated
particles of an electrolyte are ions and carry an electrical charge.
Important positively charged ions include sodium (Na+), Calcium (Ca++),
potassium (K+), and magnesium (Mg++). Important negatively charged ions
include chloride (Cl-), bicarbonate (HCO3-), phosphate (HPO4-), and many
proteins. Although blood plasma contains a number of important
electrolytes, by far the most abundant one is sodium chloride (table salt).

48. A variety of electrolytes have important nutrient or regulatory roles in the body.
For example, Iron required for hemoglobin production. Iodine must be available
for synthesis of thyroid hormones.
Electrolytes are also needed for many cellular activities such as nerve conduction
and muscle contraction.

49. Electrolytes influence the movement of water among the three fluid
compartments of the body.
To remember how ECF electrolyte concentration affects fluid volumes, remember
this one short sentence:
“Where sodium goes, water soon follows”
For example, concentration of sodium in interstitial fluid spaces rises above
normal, the volume of IF soon reaches abnormal levels too (edema) which
results in tissue swelling.

50. Reabsorption of water and electrolytes by the kidney is regulated primarily by
hormones.
When blood volume drops for any reason, (ie due to hemorrhage or excessive
water loss sweating or diarrhea), arterial blood pressure drops, which in turn
decreases amount of filtrate formed by kidneys. In addition, highty sensitive
cells in the hypothalamus called somoreceptions react to the change in blood
composition. (That is. Less water and more solutes.)

51. Sodium imbalance, potassium imbalance,
calcium imbalance p 627 yellow book

52. Maintaining Fluid Homeostasis
1. Overall fluid balance requires that fluid output equal fluid intake.
2. The type of fluid output that changes most is urine volume.
3. Renal tubule regulation of salt and water is the most important factor in
determining urine volume.
4. Aldosterone controls sodium reabsorption in the kidney.
5. The present of sodium forces water to move (Where sodium goes, water
soon follows).
The aldosterone mechanism helps restore normal ECF volume when it decreases
below normal.

53. The kidney acts as the chief regulator of sodium levels in body fluids.
Many electrolytes such as sodium not only pass into and out of the body but also
move back and forth between a number of body fluids during each 24 hour
period.
During this 24 hour period, more than 8 liters of fluid containing 1000 to 1300
mEq of sodium are poured into the digestive system as part of saliva, gastric
secretions, bile, pancreatic juice, and IF secretions.
This sodium is almost completely reabsorbed in the large intestine. Very little
sodium is lost in the feces. Precise regulation and control of sodium levels are
required for survival.
Chart in yellow text

54. Capillary Blood Pressure and Blood
Proteins
Capillary blood pressure = “water pushing” force
If capillary blood pressure increases, more fluid is pushed (filtered) out of blood
into the IF.
This effect transfers fluid from blood to IF. This fluid shift changes blood and IF
volumes.
IT DECREASES BLOOD VOLUME BY INCREASING IF VOLUME.
If, on the other hand, capillary blood pressure decreases, less fluid filters out of
blood into IF.

55. Plasma proteins act as a water-pulling or water-holding force. They hold water
in the blood and pull it into the blood from IF.
e.g. if the concentration of proteins in blood decrease appreciably, less water
moves into blood from IF. As a result, blood volume decreases and IF volume
increases.
Of the 3 main body fluids, IF volume varies the most.
Plasma volume usually fluctuates only slightly and briefly. If a pronounced
change in its volume occurs, adequate circulation cannot be maintained.

56. Fluid Imbalances
Dehydration: seen most often. In this potentially dangerous condition, IF volume
decreases first, but eventually, if treatment has not been given, ICF and
plasma volumes also decrease below normal levels.
Prolonged diarrhea or vomiting may result in dehydration due to the loss of body
fluids. Loss of skin elasticity is a clinical sign of dehydration.
Overhydration: less common than dehydration; giving intravenous fluids too
rapidly or in too large of an amount can put too heavy a burden on the heart.

57. Sources
 Mader, S.S (2006) Inquiry into Life
 Marieb, E.N (2006) Essentials of Human Anatomy & Physiology
 http://www.kidney.ca/page.asp?intNodeID=22132