The Urinary System

Health Sciences 1

• Performs the main part of the excretory function in the body

• Most important organ of excretory system is the kidney

• If kidneys fail, toxic wastes start to accumulate in the body which causes cells to “poison” the body.

Gross Anatomy

2 Kidneys2 Ureters1 Bladder1 Urethra1 Urinary meatus

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Structures of the urinary system

Kidneys• Most important excretory organ

– Bean-shaped – Located between peritoneum

and the back muscles (retroperitoneal)

– Held in position by connective tissue

– Enclosed in an adipose capsule– Protected by the ribs

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Structures of the urinary system

Kidneys• External structures

– Renal capsule– Renal fascia– Renal hilum

• Internal structures– Renal cortex– Renal medulla– Renal pelvis

Structures of the urinary system

External kidney -- Renal Capsule

• Kidney is enclosed within

– Renal fascia• Fibrous layer of connective

tissue that covers the kidney

– Renal hilum• Indentation that gives the

kidney its bean-shaped appearance (passageway for lymph vessels, nerves, renal artery and vein and ureter)

Structures of the urinary system

Internal kidney– Renal cortex

• Outer layer

– Renal medulla• Middle layer

– Renal pelvis• Innermost layer

Structures of the urinary system

Renal cortex– Composed of millions of

microscopic functional units called nephrons

Structures of the urinary system

Nephron• Functional unit of kidney– Renal corpuscle

• Bowman’s capsule• Glomerulus

– Renal tubule• Proximal convoluted

tubule• Loop of Henle• Distal convoluted tubule• Collecting tubules

Each kidney contains about 1.3 MILLION nephrons!

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Structures of the Urinary system

Renal medulla• Inner, striated layer• RENAL PYRAMIDS are

the striated cones.• Base of each pyramid

faces cortex, while apex empties into cuplike cavities called CALYCES

• Renal columns• Located between

the pyramids• Cortical tissue

4.01 Remember the structures of the urinary system

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Structures of the urinary system

Renal pelvis– Funnel shaped structure

at the beginning of the ureter

4.01 Remember the structures of the urinary system

Structures of the urinary system

Ureters– Muscular tube

extending from each kidney to the urinary bladder

– Lined by a mucous membrane

– 10-12” long

Ureters

Structures of the urinary system

Urinary bladder– Hollow muscular organ– Located in pelvic cavity– Made of elastic fibers and

involuntary muscles

Structures of the urinary system

Urethra– Connects the bladder to

the outside of the body• Female 1-2” long• Male 4-6” long

Urinary meatus– Opening to the outside

of the body

Female

Male

What are the structures of the urinary system?

Understand the Functions and Disorders of the Urinary System

Understand the functions of the urinary system

Functions:

• Excretion

– Process of removing nitrogenous waste materials,

certain salts and excessive water from the blood

Understand the functions of the urinary system

Filtration

Reabsorption

Secretion

• Blood from renal artery enters glomerulus

• High pressure in glomerulus forces fluid into Bowman’s capsule, where it is filtered

Filtration

BOWMAN’S CAPSULE

• Bowman’s capsule filters out 125cc of fluid/min. …how many cc’s per hour is this?• As the filtrate continues through nephron, 99% of

water is reabsorbed— so only 1000-1500 cc of urine are excreted daily.

Filtration

Reabsorption

• Substances include water, glucose, amino acids, vitamins, magnesium, sodium and potassium

• Reabsorbed by the capillaries around the tubules.• If blood levels of certain substances are high, the substances

will not be reabsorbed. – They remain in the tubules and are excreted in the urine.– Ex- glucose in diabetics “spilling” glucose in urine– Ex – medications – hence why medications need to be taken

frequently

Secretion

This process is the opposite of reabsorption.

• Substances are secreted into the collecting tubules include ammonia creatinine, hydrogen ions, potassium and some drugs.

Secretion

Understand the functions of the urinary system

Fluid and electrolyte balance• Electrolytes are selectively secreted to maintain

body’s acid-base balance.

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Control of urinary secretion

Fluid and electrolyte balance

Chemical control– ADH – Antidiuretic hormone

– Aldosterone

4.02 Understand the functions and disorders of the urinary system

Understand the functions of the urinary system

Fluid and electrolyte balance

Chemical control• ADH is released by the posterior pituitary gland* ADH increases size of cell membranes pores, allowing increased permeability to water.

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Understand the functions of the urinary system

Fluid and electrolyte balanceChemical control• The amount of ADH produced is related to the

level of body hydration• Under control of the hypothalamus

4.02 Understand the functions and disorders of the urinary system

Understand the functions of the urinary system

Fluid and electrolyte balanceChemical control

Aldosterone• Secreted by the adrenal cortex.• Promotes the excretion of potassium and

hydrogen ions. • Aldosterone release is the result of the renin-

angiotensin system.

Understand the functions of the urinary system

Fluid and electrolyte balance

Nervous control

• Accomplished directly through action of nerve impulses within the kidney

• Endrocine gland hormonal secretions will also control urinary secretion.

Understand the functions of the urinary systemThe flow of electrolytes

Review urine formation, electrolyte exchange, and some factors that effect urine volume.

Understand the functions of the urinary system

Elimination of urineBladder acts as a reservoir for urine. Contains approximately 500 ml of urine.Becomes distended and uncomfortable, letting us know it needs emptying. Emptying bladder (voiding) takes place by muscular contractions of the bladder, which are involuntary, although they can be controlled in some extent through the nervous system.

Understand the functions of the urinary system

Elimination of urineUrinary output

Average urinary output = 1500 ml per day *How many ounces is this?

What effects the color of your urine?

UrinalysisAn examination of urine

• What does normal urine look like?– Clear, straw clolored?

• What constitutes an abnormal urinalysis?– Presence of blood, bacteria, etc.

Urinalysis

Where would excess glucose show up?What does this mean?

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Urinalysis

4.02 Understand the functions and disorders of the urinary system

Disorders of the urinary system

Disorders of the urinary system

Cystitis

• What is cystitis (cyst= medical term for ____ +itis =___ )

• Most common cause: E. Coli• Symptoms– Painful (dysuria) or frequent (polyuria) urination

Cystitis• More common in females—Why ??

Rx=

antibiotics

Disorders of the urinary system

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Glomerulonephritis

4.02 Understand the functions and disorders of the urinary system

Disorders of the urinary system

Disease which injures the glomerulus.

What will happen as a result of damaged glomeruli?• Filtration process isaffected

• Acute Glomerulonephritis– Sudden onset– Occurs after bacterial infection (usually strep

throat in children)– Treated with antibiotics

• Chronic glomerulonephritis– Filtration membrane is permanently affected– Caused diminished function of the kidney– May result in kidney failure.

Renal Calculi

• Also known as kidney stones• Can be calcium, uric acid or other substances• They grow larger and eventually fill the renal

pelvis and possibly obstruct flow of urine.

• First symptom – extreme pain in kidney area or lower abdomen (colic)

• Nausea and vomiting are common

• May have painful urination, frequency, chills or fever

• Possibility of blood in urine (hematuria)• Diagnosed with ultrasound or CT scan• Treat with increased fluids to flush stone out.• Possibility of lithotripsy (see page 437 medical

highlight)• Meds for pain

Renal Failure

• Acute– Sudden onset– Caused by inflammation of the nephron

(nephritis), shock, injury, bleeding, heart failure or poisoning

– Symptoms• Oliguria (scanty or diminished production of urine)• Anuria (absence of urine) – could be dangerous

because of build up of toxins

Chronic renal failure

• Gradual loss of kidney functions.• Treat with Dialysis– Passage of blood through a device which rids the

blood of harmful waste, extra salt, and water– These devices serve as a substitute kidney.• Two forms

– Hemodialysis and peritoneal dialysis

Hemodialysis

Process for purifying blood by passing it through a thin membrane and exposing it to a solution which continually circulates around the membrane. Uses a machine called a dialyzer

Kidney Transplants

• Done in cases of prolonged chronic debilitating diseases and renal failure involving both kidneys.

• Usually clients have been on dialysis for a long time waiting for a compatible organ.

• Daily meds to prevent rejection• Improve quality of life

Peritoneal dialysis

• Uses the persons own peritoneal lining instead of a dialyzer to filter the blood.