Urinary System

Edison D. Ramos, RMT, MPHAssistant Professor II

College of Medical Technology

Manila Central University

INTRODUCTION

- It helps keep the body in homeostasis by removing and restoring selected amounts of solutes and water from blood

Consists of:KIDNEY – main filtering organs of the system, paired organ that regulate the composition and volume of blood and remove wastes from the blood in the form of urine.

URETER – transport urine from the renal pelvis into the urinary bladder

BLADDER – hollow muscular organ located in the pelvic cavity posterior to the pubic Symphysis.

URETHRA – the tube that leads from the bladder to the outside

Urine Formation by Nephron

Blood pressure forces water, glucose, amino acids and urea from capillaries into nephron

Glucose and amino acids are reabsorbed into blood from nephron

Some water is reabsorbed into blood

Urine is urea and salt concentrated in water

Regulation of Water Balance

Brain monitors water content of blood

If low water content, pituitary releases ADH

ADH travels in blood to nephron

ADH causes more water to move from urine back into blood

Urinary SystemHas specific Performs specific

Structure Functionenables

Kidney

includes

Nephron

Collecting Ducts

Minor Calyces

Major Calyces

Renal Pelvis

Ureters

Urinary Bladder

Urethra

Lead to

Urine flows to

Urine flows to

Urine flows to

Urine flows to

Urine flows to

Urine flows to

Urine elimination

includes

Waste and foreign

substanceUrine storage

Urine formation

Tubular secretion

Tubular reabsorption

Glomerular filtration

by

FUNCTIONS OF THE URINARY SYSTEM

1. Excretion

- Kidney filter large amounts of fluid from the bloodstream. They are the major excretory organ because they eliminate nitrogenous wastes, drugs and toxin from the body. It also reabsorb needed substances and return them to blood.

2. Maintain blood volume and concentration

- Regulating the proper balance in the blood between salt and water, regulate concentration of ions in body fluids and blood so the proper balance of Na, K, Ca, and phosphate ions is maintained.

3. pH regulation

- Control the proper balance of hydrogen ions in the blood

4. Blood pressure

- Produce enzyme RENIN which helps maintain blood pressure

5. Erythrocyte concentration

- Produce the protein hormone ERYTHROPOIETIN which stimulates red blood cell production

6. Vitamin D production

- It converts vitamin D to calciferol which is its active form. Kidney participate along with liver and skin in vitamin D synthesis.

EXTERNAL ANATOMY OF THE KIDNEY

- Kidneys are paired organs that are reddish in color and resemble kidney beans in shape

- They are about the size of a closed fist

- The right kidney is slightly lower than the left because of the large area occupied by the liver.

HILUM – notch in the concave center of the kidney through which a ureters leaves the kidney and blood vessels, nerve, lymph vessels enter and exit the kidney

Three layers surrounding each kidney

1. Renal capsule – innermost layer, act as a barrier against infection and trauma.

2. Adipose capsule – second layer, mass of fatty tissue that protect the kidney from blows

3. Renal fascia – outermost layer, anchors the kidney to the abdominal wall.

CORTEX – outer area of kidney

MEDULLA – inner area of kidney

RENAL PYRAMID – striated, triangular structure within the medulla whose bases face the cortex and tips point to the center of kidney (renal papillae)

RENAL COLUMN – cortical material that extends between the pyramids

MINOR CALYX – funnel-shaped structures that surround the tip of renal pyramid

MAJOR CALYX – union of minor calyces

RENAL PELVIS – union of major calyces, large collecting funnel which narrows to form ureter

ANATOMY OF THE NEPHRONNEPHRON – functional unit of kidney

BOWMAN’S CAPSULE – double-walled globe where nephron begins.

GLOMERULUS – capillary network surrounded by bowman’s capsule

PROXIMAL CONVOLUTED TUBULE – first part of the renal tubule

DESCENDING LIMB OF HENLE – name given to PCT as it dips into the medulla

LOOP OF HENLE – U-shaped structure of the limb of Henle

ASCENDING LIMB OF HENLE – name given to loop of Henle as it ascends toward the cortex

DISTAL CONVOLUTED TUBULE – name given to the ascending limb of Henle as it enters the cortex and becomes convoluted

COLLECTING DUCT – connects with the distal tubules of the other nephron

Proximal Convoluted Tubule

Reabsorbs: water, glucose, Reabsorbs: water, glucose, amino acids, and sodium.amino acids, and sodium.

•65% of Na+ is reabsorbed•65% of H2O is reabsorbed

•90% of filtered bicarbonate (HCO3-)

•50% of Cl- and K+

Loop of Henle

Creates a gradient of increasing Creates a gradient of increasing sodium ion concentration towards sodium ion concentration towards the end of the loop within the the end of the loop within the interstitial fluid of the renal pyramid.interstitial fluid of the renal pyramid.

•25% Na+ is reabsorbed in the loop•15% water is reabsorbed in the loop•40% K is reabsorbed in the loop

Distal Convoluted Tubule

Under the influence of the hormone Under the influence of the hormone aldosterone, reabsorbs sodium and aldosterone, reabsorbs sodium and secretes potassium. Also regulates secretes potassium. Also regulates pH by secreting hydrogen ion when pH by secreting hydrogen ion when pH of the plasma is low.pH of the plasma is low.

• only 10% of the filtered NaCl and 20% of water remains

Collecting Duct

Allows for the osmotic Allows for the osmotic reabsorption of water.reabsorption of water.

ADH (antidiuretic hormone)- makes collecting ducts more permeable to water-- produce concentrated urine

BLOOD AND NERVE SUPPLY TO THE NEURON

- Nephrons are mainly responsible for removing wastes from the blood and regulating its electrolytes and fluid content, they are richly supplied with blood vessels.

RIGHT and LEFT ARTERIES – transport 1200ml of blood to the kidneys every minute

- The arteries that branch and pass between the renal pyramids in the renal column as the INTERLOBAR ARTERIES

AFFERENT ARTERIOLE – takes blood from the renal artery to bowman’s capsule, where the arteriole divides into tangled capillary network known as GLOMERULUS

EFFERENT ARTERIOLE – formed from union of glomerulus, carries blood away from the bowman’s capsule. Each efferent arteriole further divides to form a network of capillaries called PERITUBULAR CAPILLARIES

PERITUBULAR CAPILLARIES reunite to form INTERLOBULAR VEIN

PHYSIOLOGY OF THE NEPHRONS

Three major functions of Nephron

1. Control blood concentration and volume by removing selected amount of water and solutes

2. Help regulate blood pH

3. Remove toxic waste from the blood

Formation of Urine

1. GLOMERULAR FILTRATION

- removes water and dissolved substances from the plasma of blood (Na, K, Ca, Mg, Cl, Sulfate, Phosphate, glucose, urea, uric acid) 90% of the fluid gets reabsorb in the renal tubules and reenters the plasma. The remaining small portion leaves the kidney as urine

2. TUBULAR REABSORPTION

- transport substances out of the tubular fluid and back into the blood of the peritubular capillary. Majority of the reabsorption occurs in the PCT. Active transport reabsorbs glucose and osmosis reabsorbs water. Positively charged ions are reabsorbed by active transport and negatively charged ions are reabsorbed by electrochemical attraction

3. TUBULAR SECRETION

- moves the substances from plasma in the peritubular capillary into the fluid of the renal tubule

PCT: secretes penicillin, creatinine and histamine

RENAL TUBULE: secretes hydrogen ions

DCT, COLLECTING DUCT – secrete potassium ions

ANATOMY AND FUNCTIONS OF URETER

- Body has 2 ureters each one descending from a kidney

- Each ureter is an extension of the pelvis of the kidney and extends down to the urinary bladder

FUNCTION: transport urine from the renal pelvis into the urinary bladder

- The urine is carried through the ureters by peristaltic contraction of smooth muscle walls but gravity and hydrostatic pressure also contribute

URINARY BLADDER- Hollow muscular organ located in the pelvic cavity.

- It is a movable organ held in position by folds of peritoneum

- When empty, it resembles a deflated balloon. When full of urine, it is spherical shape. As urine volume increases, it becomes pear-shaped and ascends into abdominal cavity

- Urine is expelled from the bladder by an act known as MICTURITION commonly referred to as urination or voiding.

- The average capacity of bladder is 700 to 800ml

Ureter

Bladder

PROBLEMS OF THE URINARY TRACT

Incontinence (urine leakage)

Causes of Incontinence

Stress incontinence: leaking small amounts of urine when coughing, lifting, or exercising

Urge incontinence: the bladder suddenly and unexpectedly contracts and expels urine

Overflow incontinence: bladder cannot completely empty so urine dribbles

Treatments for Incontinence

Kegel exercises to strengthen the urinary sphincter Medicines that increase the sphincter’s ability to contract Surgery to strengthen the pelvic muscles or to lift the bladder Retrain the bladder to increase its storage capacity (allowing

3-4 hours between urinating) Drugs to prevent urge incontinence Surgery to remove part of prostate gland if responsible for

overflow incontinence

Kidney stones form in the kidney pelvis. There are 4 types of stones.

•Calcium stones (most common)•Uric acid stones•Bacteria caused stones•Cystein stones

Treatments for Kidney Stones Small stones may pass with no pain Larger stones may pass but cause extreme of pain,

requiring a lot pain medication Stones that are too large to pass may require

surgical treatment including: using a ureteroscope to go up and snare the

stone using a nephroscope to crush the stone and

retrieve it using shock wave lithotripsy where a person is

submerged in water containing shock waves to pulverize the stones

Urinary Tract Infection (UTI)

Second most common infection following respiratory infections

UTI occur when bacteria (E. coli) from the digestive tract get into the opening of the urinary tract and multiply

Bacteria first infect the urethra, then move to the bladder and finally to the kidneys

UTI tend to occur more in women than men

Women may have more UTIs than men because: 1) they have a shorter urethra, allowing quicker

access to the bladder2) the urethral opening is nearer the anus3) intercourse may result in UTIs in women

Symptoms of UTIs

Urge to urinate but only small amount of urine produced

Pain and burning sensation in bladder

Fever Blood in urine

Diagnosis and Treatment

Doctors check urine for white and red blood cells and bacteria

Bacteria grown in culture to determine which antibiotic will work the best

UTIs are treated with antibiotics and are often cured within 1 or 2 days

The End