pgu1 intruduction to urinary system

8/9/2019 PGU1 Intruduction to Urinary System

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UrinaryUrinary SSystemystem

IntroductionIntroduction

Dr Sami Abdo Radman


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Urinary systemUrinary system

Includes:

Two kidneys,

Two ureters, The urinary bladder,

Two sphincter muscles, and

The urethra


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Urinary System Anterior/Posterior Views


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Costovertebral Angle (renal angle)

Costovertebral Angle

T12

T11

L112th Rib

R. Kidney L. Kidney


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Kidney anatomy

Kidney is reddish-brown

Lie in the superior lumber region of the posteriorabdominal wall

weight about 300 g Looks like a bean

Approximately 4 inches x 2 inches

Extend from the level of the 11th or 12th thoracicvertebra to the 3rd lumber vertebra

Hilus indentation where blood vessels andstructures enter or exit the kidney


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Kidney anatomy

Two parts :

Cortex: Glomerular apparatus

Medulla:

Consists of about 1 million

filtering units called nephrons(basic structural and functional

unit)


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Renal Medulla

Dark, triangular structure

Form small cone shaped

regions called renal

pyramids Each pyramid is separated

by renal columns

The lower ends of the

pyramids point to the renal

pelvis

5-11 pyramids in each

kidney


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Renal pelvisRenal pelvis

The major function of the renal pelvis is toact as a funnel for urine flowing to the ureter.

The renal pelvis represents the funnel-likedilated proximal part of the ureter.

It is the point of convergence of two or three

major calices. Eachrenal papilla is surrounded by a branch

of the renal pelvis called a calyx.

Infection of renal pelvis is called pyelitis


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UretersUreters

Urine is collected in the renal pelvis

renal pelvis connects to the ureters,

which carry urine to the bladder. The ureters are about 200 to 250 mm

long.

Smooth musculartissue in the walls ofthe ureters peristaltically force the urine

downward.


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Urinary bladderUrinary bladder

The urinary bladderis a hollow muscular organshaped like a balloon.

It is located in the pelvic fossa and held in place byligaments attached to the pelvic bones.

Located behind the symphasis pubis The bladder stores urine - up to 500 ml of urine

comfortably for 2 to 5hours.

Sphincters (circular muscles) regulate the flow of

urine from th

e bladder. Internal urethral sphincter= in the beginning of urethrasmooth muscle not under ourvoluntary control

External urethral sphincter= skeletal muscle we cancontrol it


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UrethraUrethra

The urethra has an excretory function in both sexes,to pass urine to the outside

A reproductive function in the male, as a passage for

sperm. The external urethral sphincteris a striated smooth

muscle that allows voluntary control overurination.

Urethral sphincters:

Internal External

In males the internal and external urethral sphinctersare more powerful, able to retain urine for twice as

long as females


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Nephron

Each kidney contains about 1 million

nephron units

The number does not increase after birt

h

They cannot be replaced if damaged

2 parts

Renal curpuscles (Glomerulus, Bow

manscapsule)

Renal Tubules


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Renal curpuscles

Glomerular capsule (Bowmans Capsule) C shaped capsule surrounding the

glomerulus

Glomerulus cluster of capillaries Renal Tubules

Proximal convoluted tubule

Loop ofHenle ascending and descendinglimb

Distal Convoluted tubule

Collecting duct


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Renal Vasculature

Receives blood from the renal artery

Renal artery branches into the afferent arterioles

Afferent arterioles feed into Bowmans capsule

The efferent arterioles exit Bowmans capsule

The efferent arterioles form the peritubular

capillaries

The peritubular capillaries empty into thevenules, large veins, and then into the renal

veins

.


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Function of urinary systemFunction of urinary system

Excretion

Keeping homeostasis

Keeping acid-base balance PH

Regulation of blood pressure (rennin)

Formation of RBCs (erythropoiesis) by secretion of erythropoetin)

Vitamin D synthesis

Excreted products:

Product of the metabolism (It clears urea, a nitrogenous wasteproduct)

Water

Hormones Vitamins

Toxic substances


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Regulation of blood volume:The kidneys conserve or eliminate water from the blood,wh

ich

regulates th

e volume of blood in th

e body . Regulation of blood pressure:

Adjusting the volume of blood in the body (by regulatingthe quantity ofwater in the blood

Action of the enzyme renin. The kidneys secret renin,which activates the angiotensin-aldosterone pathway.

Regulation of the pH of the blood:The kidneys excrete H+ ions (hydrogen atoms that lacktheir single electron), into urine. At the same time, thekidneys also conserve bicarbonate ions (HCO3-), whichare an important buffer ofH+.

pH 7.4.


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The process of separating wastes from the

body fluids and eliminating them, is known

as excretion


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Formation of Urine

Three processes are involved in urine

formation

Glomerular filtration

Tubular reabsorption

Tubular secretion


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(1)GlomerularFiltration

The diameter of the afferent (incoming) arteriole isgreater than the diameter of the efferent arteriole

The pressure of the blood inside the glomerulus isincreased due to the difference in diameter of the

incoming and out-going arterioles. This increased blood pressure helps to force the

following components of the blood out of the glomerularcapillaries:

Most of the water ;

Most/all of t

he salts ; Most/all of the glucose ;

Most/all of the urea .


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Blood cells and plasma proteins are not filteredthrough the glomerular capillaries.

. Presence of cells and protein indicate a kidney

dysfunction The water and salts that have been forced out of

the glomerular capillaries pass into the Bowman'sCapsule and are called the glomerular filtrate.

Renal blood flow= 1200- 1300 ml/ min, (cardiacoutput=5600 ml/min)

This glomerular filtrate is formed at a rate ofabove 125 cm3 (mL) per minute (glomerularfiltration rate) =7.5L/h =180L/day

This volume is approx. 20% of the plasmadelivered during that time

Urine volume=1L/day (depends on )


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(2)Tubular Reabsorption

Only about 1% of the glomerularfitrate

actually leaves the body because the

rest (the other 99%) is reabsorbed intothe blood while it passes throughthe

renal tubules

Most of the volume of the fitratesolution is reabsobed in the proximal

convoluted tubule (PCT)


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(3)Tubular Secretion

Substances being added to the tubular

fluid from the efferent arterioles


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CLEARANCECLEARANCE

The GFR can be measured by measuring the

excretion and plasma level of a substance that

is freely filtered through the glomeruli and

neither secreted, nor reabsorbed by thetubules

Amount per unit of time

GFR = (UX) V/ P

X

(UX) = concentration ofX in the urine

V= urine flow per unit of time

PX = concentration ofX in the plasma

Eg . Inulin


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CLEARANCECLEARANCE

Example:

UIN=35 mg/Ml

V= 0.9 mL/min PIN= 0.25 mg/Ml

CIN=350.9/0.25 = 126ml/min


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(Micturition)(Micturition)

The process of disposing urine from theurinary bladder through the urethra to theoutside of the body.

The process of urination is usually undervoluntary control.

Urinary incontinence is the inability to controlurination, and is more common in women

than men. Urinary retention refers to the inability to

urinate.

Enuresis nocturnia = incontinence during the

night


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Urine Characteristics

Amount 1500 ml in 24 hours

pH average 6.0

Specific Gravity heavier than water(1.001-1.035)

Color yellow (amber, straw colored,

concentrated, orange, brow

n, red,sediment, clear or cloudy)

Dehydrated = deep yellow, dark

Overhydrated = pale yellow, colorless


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Light yellow color of urine is due to a

pigment called uroch

rome Urochrome is formed from the breakdown

ofhemoglobin in the liver


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Urine Testing

Urinalysis

Microscopic exam

Culture and sensitivity Urine dipstick

Urine Drug and alcohol screening

24 hour urine testing


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Abnormal Constituents ofUrine

Albumin (protein)

Glucose

Red blood cells Hemoglobin

White blood cells

Ketone bodies Bilirubin


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pgu1 intruduction to urinary system

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