Unit G: Urinary System

Fun Facts

AKA the Excretory System

Performs the main part of the excretory function in the body- to urinate!

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 Kidneys

• 2 Ureters

• 1 Bladder

• 1 Urethra

• 1 Urinary Meatus

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 floating ribs

External Structures

• Renal Capsule

• Renal Fascia

• Renal Hilum

Internal Structures

• Renal Cortex

• Renal Medulla

• Renal Pelvis

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)

Internal Kidney

• Renal Cortex: Outer layer

  • Composed of millions of microscopic functional units called nephrons

• Renal Medulla: Middle layer

  • 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

• Renal Pelvis: Innermost layer

Ureters

• Muscular tube extending from each kidney to the urinary bladder

• Lined by a mucous membrane

• 10-12” long

Urinary Bladder

• Hollow muscular organ

• Located in pelvic cavity

• Made of elastic fibers and involuntary muscles

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

• The external opening of the Urethra

Day 2: Functions of the Urinary System

Important

1. Proximal Convoluted Tubule

2. Distal Convoluted Tubule

3. Loop of Henle (nephron)

4. Bowman’s Capsule

5. Collecting Tubule

6. Glomerulus

(1,2,3 do the same function. 4,5,6 do different functions)

Functions

• Excretion

  • Process of removing nitrogenous waste materials, certain salts and excessive water from the blood

Formation of Urine: Filtration → Reabsorption → Secretion

Filtration

• Blood from the renal artery enters the glomerulus

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

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 (1-1.5 L)of urine are excreted daily

Reabsorption

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

• Reabsorbed by the capillaries in bloodstream 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.

Elimination (Excretion) of urine

• Bladder acts as a reservoir (storage tank) for urine.

• Contains approximately 500 ml of urine.

• Becomes distended and uncomfortable, letting us know it needs emptying.

• Emptying the bladder (voiding) occurs through involuntary muscular contractions, which the nervous system can control to some extent.

Fluid and electrolyte balance

• Electrolytes are selectively secreted to maintain body’s acid-base balance.

• Chemical control: aid in the REABSORPTION process!

  • ADH – Antidiuretic hormone

  • Aldosterone

• The amount of ADH produced is related to the level of body hydration

• Under control of the hypothalamus

• Aldosterone Secreted by the adrenal cortex of the KIDNEY.

  • Promotes the excretion of potassium and hydrogen ions.

  • Aldosterone release is the result of the renin-an enzyme in the kidneys that is released into the bloodstream.

Nervous control

• Accomplished directly through action of nerve impulses on blood vessels within the kidney (and glomerulus)

• Endocrine glands (Posterior Pituitary) hormonal secretions (Vasopressin and/or ADH) will also control urinary secretion.

Disorders and Dysfunctions

Cystitis

• What is cystitis?

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

An inflammation of the mucous membrane lining of the urinary bladder.

• The most common cause: is E. Coli (an organism found in the rectum)

• Symptoms: Painful (dysuria) or frequent (polyuria) urination

More common in females—Why ??

• The length of the female urethra is 1.5-2 inches long.

Organisms can easily enter the urethra and then into the bladder from the outside of the body.

Glomerulonephritis

• Disease which injures the glomerulus of the nephron.

• What will happen as a result of damaged glomeruli?

  • Filtration process is affected

  ACUTE (one instance)

• Sudden onset

• Occurs after bacterial infection (usually strep throat in children)

• Treated with antibiotics

Chronic (Long Term)

• Filtration membrane is permanently affected

• Causes diminished function of the kidney

• May result in kidney failure.

Renal Calculi (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 (colon)

• 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 429 medical highlight)

• Meds for pain

Acute Renal Failure

• 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

Incontinence-Lack of voluntary control of urination

Enuresis-involuntary urination (bedwetting)

Treatment Options

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

Peritoneal Dialysis

• Uses the person’s own peritoneal lining instead of a dialyzer to filter the blood.

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

Urinalysis

• An examination of urine

• What does normal urine look like?

  • Clear, straw colored

• What constitutes an abnormal urinalysis?

  • Presence of blood, bacteria, protein, pus, etc.