The urinary system's function is to filter blood and create urine as a waste by-product. The organs of the urinary system include the kidneys, renal pelvis, ureters, bladder and urethra. The body takes nutrients from food and converts them to energy. After the body has taken the food components that it needs, waste products are left behind in the bowel and in the blood. The kidney and urinary systems help the body to eliminate liquid waste called urea, and to keep chemicals, such as potassium and sodium, and water in balance. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys, where it is removed along with water and other wastes in the form of urine.The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.Bladder. This triangle-shaped, hollow organ is located in the lower abdomen. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder's walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to two cups of urine for two to five hours. Upon examination, specific "landmarks" are used to describe the location of any irregularities in the bladder. These are: Trigone: a triangle-shaped region near the junction of the urethra and the bladder Right and left lateral walls: walls on either side of the trigone Posterior wall: back wall Two sphincter muscles. These circular muscles help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder. Nerves in the bladder. The nerves alert a person when it is time to urinate, or empty the bladder. Urethra. This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to rel

1. Module ΙV
Urinary system

3. • Urinary system is also known as the renal
system
• It consist of kidneys, ureters, urinary bladder
and urethra
• 2 kidneys : which secrete urine
• 2 ureters : which convey the urine from the
kidneys to the urinary bladder
• 1urinary bladder: where urine collects and is
temporarily stored
• 1 urethra :urine is discharged from the urinary
bladder to the exterior

4. KIDNEYS
• The kidneys lie on the
posterior abdominal wall,
one on each side of the
vertebral column
• Bean shaped ,reddish
brown organs
• 11 cm long, 6cm wide,
3cm thick and 150 g
weigh

5. • Renal capsule: covered by a tough capsule
fibrous connective tissue. Which encloses and
protects kidney against infections and trauma
• Renal cortex : reddish brown layer of tissue
contains most of the nephrons
• Medulla: inner layer of the kidney ,consisting of
pale conical shaped striations, the renal pyramids,
renal calyces and renal pelvis. Site for salt, water
and urea absorption
• Renal pyramid: triangular shaped unit in the
medulla. Houses the loop of henle and collecting
duct of the nephron

6. • Renal column : area b/w the pyramids, located
in the medulla. Used as a space for blood vessel
• Renal papillae: tips of the renal pyramids.
release urine in to the calyces
• Renal calyces: collecting sacs that surround the
renal papillae. Transport urine from renal
papillae to renal pelvis
• Renal pelvis : cavity which lies in the center of
the kidney and which extends into the ureter.
Collects urine from all of the calyces in the
kidney

7. • Renal arteries: transport oxygenated blood from
the heart and aorta to kidneys for filtration
• Renal veins: transport the filtered, deoxygenated
blood from kidneys to the posterior venacava and
finally the heart
NEPHRON
• Functional unit of kidney
• Each kidney is formed of about 1 million
nephrons

8. Types of nephron
• Two types of nephron
• Cortical nephron : 80-85 % of nephrons are
cortical nephrons. Renal corpuscles are in outer
cortex and loops of henle lie mainly in cortex
• Juxtamedullary nephrons : 15-20% of
nephrons are juxtamedullary nephrons. Renal
corpuscles close to medulla and long loops of
henle extend into deepest medulla

10. • Renal corpuscle:head of the nephron. It is
composed of bowman's capsule and glomerulus
• Bowman's Capsule: large double walled cup. It lies
in the renal cortex . Sac that encloses glomerulus.
Transfers filtrate from the glomerulus to the
proximal convoluted tubule
• Glomerulus: site for blood filtration. Surrounded by
bowman's capsule . Removes both useful and non
useful material
• Proximal convoluted tubule: active segment of
nephron. It reabsorb most useful substance of the
fiterate.Sodium(65%),bicarbonate(90%),chloride(50
%)and glucose (nearly100%). It lies in renal cortex

11. • Loop of henle: U-shaped tube consist of descending
and ascending limb .
• Descending limb full permeable to water and
completely impermeable to solutes (salt particles)
• Receives filtrate from the pct allow water to be
absorbed and passes salty filtrate to the next
segment
• Ascending limb imperable to water and actively
transport salt to the interstitial fluid of the pyramids
in the medulla
• Passing filterate becomes dilute

12. • Distal convoluted tubule: highly coiled part of the
nephron. receives dilute fluid from the ascending
limb of the loop of henle.
• Collecting duct : save water for the body
BASIC RENAL PROCESS
• There are 3 basic renal process
• Glomerular filtration
• Tubular reabsorption
• Tubular secretion

13. • Glomerular filtration: the filtration of plasma from
glomerular capillaries into the bowman’s space is
termed glomerular filtration
• During filtration blood enter the afferent arteriole
and flows in to glomerulus where filtrate blood
components such as water and nitrogenous waste will
move towards glomerulus and non filterable
components such as cells, albumin will exit efferent
arteriole. These filtrate components accumulate in
the glomerulus to form the glomerular filtrate.
• Efferent arteriole is narrower than afferent helps in
building hydrostatic pressure

14. • Flow of blood in the glomerulus creates hydrostatic
pressure which forces molecules through
glomerular filtration membrane
• Tubular reabsorption: process by which solutes
and water are removed from the tubular fluid and
transported into the blood .
• Removes useful solutes from the filtrate ,returns
them in to blood
• Tubular secretion: Substances move in to distal
and collecting tubule s from the blood in the
cappillaries around these tubules
• removes additional wastes from the blood and adds
them to the fitrate

16. Tubular reabsorption

17. Micturition
• Process by which urine is
voided from the urinary
bladder
• It is reflex process
• Two sphincters, or valves
the internal and external
urethral sphincter control
the flow of urine from the
bladder

18. • Bladder continues to collect urine untill about
200ml have accumulated
• Stretching of the bladder wall activates stretch
receptors
• Impulses transmitted to the sacral region oof the
spinal cord and back to the bladder via
splanchnic nerves cause the bladder to go in to
reflex contractions
• As the contraction s become stronger, stored in
urine is forced past the internal urethral
sphincter in to the upper part of the urethra

19. • It is then that a person feels the urge to void
because the lower external sphincter is skeletal
muscle is voluntarily controlled, choose to keep it
closed and postpone bladder emptying temporarily
• If it is convenient the external sphincter can be
relaxed so that urine is flushed from the body
• when one chooses not to void, the reflex
contractions of the bladder will stop with in a
minute and urine will continue to accumulate in
the bladder
• After 200 to 300 ml more have been collected ,
the micturition reflex occurs again

20. Plasma clearance
• Amount of plasma cleared off a substance in
given unit of time. It is also known as renal
clearence
• C=UV/P
• C is plasma clearance
• U is urine conc.
• V is volume of urine
• Plasma conc.

21. • Determination of clearance value for certain
substances helps in assessing the following renal
functions
a. Glomerular filtration rate
b. Renal plasma flow
c. Renal blood flow
• Glomerular filtration rate describes the flow rate
of filtered fluid through the kidney
• A substance that is completely filtered but neither
reabsorbed nor secreted should be used to
measure GFR
• Inulin is the ideal substance used to measure GFR

22. • Inulin clearance- a known amount of inulin is
injected into the body. After sometime, the conc of
inulin in plasma and urine and the volume of urine
excreted are estimated
• To measure renal plasma flow ,a substance which is
filtered and secreted but not reabsorbed should be
used. such a substance is para-aminohippuric acid
(PAH). PAH clearance indicates the amount of
plasma passed through kidneys
• Renal blood flow is volume of blood delivered to the
kidneys per unit time
• Renal blood flow can also be calculated
RBF=RPF÷1-Hematocrit

23. BODY FLUIDS
• Body is formed by solids and fluids
• Fluid part is more than two third of the whole body
Significance of body fluids
• Homeostasis-body cells survive in fluid medium
called internal environment. internal environment
contains substances such as glucose, amino acids,
lipids, vitamins etc.. Essential for growth &
function of cell. water not only form the major
constituent of internal environment and play an
important role in homeostasis

24. • Transport mechanism- body water transport
medium by nutrients and other essential
substances enter the cells and unwanted
substances come out.
• Metabolic reaction-water inside the cells
forms the medium for various metabolic
reaction which are necessary for growth &
functional activity of the cells
• Temperature regulation- water maintaining
normal body temperature

25. COMPARTMENT OF BODY FLUIDS
• Total water in the body is 40L
• It divided in to 2 major compartments
• Intracellular fluid(ICF) – Its volume is 2.2L and it
forms 55% of the total body water
• Extracellular fluid (ECF)-Its volume is 18L and it
forms 45% of the total body water
• ECF is divided in to 5 subunits
• Interstitial fluid and lymph
• Plasma
• Fluid in bones
• Fluid in dense connective tissues like cartilage
• Transcellular fluids

26. Acid –base balance
• For normal function of body and normal enzyme
activity a normal hydrogen ion conc. (normal pH) is
essential.
• pH is the –ve log of hydrogen ion conc.
• A hydrogen ion is a single free proton release from
hydrogen atom
• pH of arterial blood =7.4
• pH of venous blood =7.85
• pH of urine=8.0
• Acidosis- pH of body fluid less than normal
• Alkalosis-pH of body fluid more than normal

27. Acids
• Acids are molecules that release H+ ion in
solutions
• Strong acids dissociate rapidly and release large
amount of H+ion
• HCL H+ + CL-
• Weak acids have less tendency to dissociate and
release less amount of H+ ion
• H2CO3 H++ HCO3
-

28. Bases
• Bases are molecules that can accept H+ ion
• Strong bases react strongly with H+ ion
• H + + OH- H2O
• Weak bases bind weakly with H+ion
• H++ HCO3 H2CO3

29. Buffer
• A buffer is any substance that can reversibly
bind H+
• The general form of buffering reaction
• Buffer+H+ Hbuffer
• Resists sudden changes in pH

30. Renal Control of Acid-Base Balance
• The kidneys control acid-base balance by
excreting either acidic or basic urine
• Excreting acidic urine reduces the amount of
acid in extracellular fluid
• Excreting basic urine removes base from the
extracellular fluid

31. • The kidneys regulate extracellular fluid H+
concentration through three fundamental
mechanisms:
(1)secretion of H+
(2) reabsorption of filtered HCO3
(3) production of new HCO3

32. Secretion of hydrogen ions and
reabsorption of bicarbonate ions by the
renal tubules
• About 80 to 90 percent of the bicarbonate
reabsorption and H+ secretion occurs in the
proximal tubule

33. Mechanism of Hydrogen ion secretion
and Bicarbonate Reabsorption

34. • The secretory begins when co2 either diffuses
into the tubulr cells or is formed by metabolism
in the tubular epithelial cells
• co2 under the influenze of the enzyme carbonic
anhydrase combine with h2o to form H2CO3,
which dissociates into HCO3 and H+
• H+ secreted from the cell into tubular lumen by
sodium hydrogen counter transport
• When an Na+ moves from the lumen of the
tubule to the interior of the cell,it first combines
with a carrier protein in the luminal border of cell
membrne
• Na+ moves into the cell down a conc. gradient
that has been established by the Na-k atpase
pump in the basolateral membrane

35. • The gradient for Na+ moves in to the cell
provides energy for moving H+ in the opposite
direction from the interior of the cell to the
tubular lumen
• The HCO3 generated in the cell then moves
downhill across the basolateral membrane to
interstitial fluid and peritubular capillary blood
• The net result is every H+ secreted into
tubular lumen ,an HCO3 enters the blood

36. Primary Active Secretion of H+ in the
Intercalated Cells of Late Distal and
Collecting Tubules

37. • It occurs at the luminal membrane of the
tubular cell where H+ is transported directly
by a specific protein a hydrogen transporting
ATPase
• The energy required for pumping the H+ is
derived from the breakdown of ATP to
adenosine diphosphate
• Primary active secretion of H+ occurs in a
special type of cell called intercalated cells of
the distal tubule and collecting duct.

38. • Hydrogen ion secretion in these cells is
accomplished in to 2 steps
• 1) the dissolved CO2 in this cell combines
with H2O to form H2CO3
• 2) the H2CO3 then dissociates, which is
reabsorbed in to blood plus H+ which is
secreted into the tubule by means of the
hydrogen ATPase mechanism

39. Excretion of Excess H+ and Generation
of New Bicarbonate by the Ammonia
Buffer System

40. • Ammonium ion is synthesised from glutamine
which comes mainly from the metabolism of liver.
• The glutamine delivered to the kidneys is
transported into the epitheliel cells of proximal
tubule
• Once inside the cell each molecule of glutamine is
metabolised ina series of reaction to ultimately
form twoNH4+ and twoHCO3-
• The NH4+ is secreted in to the tubular lumen by a
counter transport mechanism in exchange of
sodium, which is rebsorbed
• The HCO3 is transported across the basolateral
membrane along with the reabsorbed Na+ to the
interstial fluid and taken by the peritubular
cappilaries

41. • For each molecule of glutamine metabolised
in the proximal tubules two NH4+ are secreted
into the urine and two HCO3 are reabsorbed
in to the blood
• The HCO3 generated by this process
constitutes new bicarbonate