W.13 - Urinary System & Urinalysis

What structures comprise the urinary system?

Kidney and Urinary tract (ureters, urinary bladder & urethra)

Enumerate the functions of the urinary system.

1. Storage of urine

2. Excretion of urine 

3. Regulation of:

   1. Blood volume

   2. RBC production

   3. Ion levels

   4. Acid-base balance

What structures comprise the urinary tract?

Ureters, urinary bladder & urethra

Are the kidneys at the same level w/ each other?

No – the right is pushed down by the liver

What is a nephron?

a. How many do we have in each kidney?

Nephron is the functional filtration unit of the kidney

• Each consists of a renal corpuscle + renal tubule.

• 2 types of Nephron

  • Cortical nephrons (85%)

  • Juxtamedullary nephrons (15%)

a. 1 million

What are the processes involved in urine formation? (FRS)

1. Filtration

   1. Water and some dissolved solutes move out of glomerulus and into capsular space of renal corpuscle due to pressure

   2. Once fluid leaves plasma and enters capsular space, it is called filtrate

2. Tubular reabsorption

   1. Substances (most water and all needed solutes) in filtrate are reabsorbed to the blood

3. Tubular secretion

   1. Solutes are actively transported out of blood and into tubular fluid

What is the urethra?

a. What are the two sphincters found in the urethra?

Urethra is a fibromuscular tube from the urinary bladder, conducting urine to the exterior of the body

• Lined with mucin producing cells in mucosa

• Has smooth muscle to help propel urine

a. Internal urethral sphincter – at the beck of bladder – INvoluntary

External urethral sphincter – in urogenital diaphragm – voluntary

Compare and contrast male and female urethra

Female urethra ONLY transports urine

• Stratified squamous epithelium

Male urethra transports urine AND semen, but not simultaneously

What are the advantages of urinalysis (assessing the composition of plasma and detecting diseases)?

convenient and nonintrusive

When is urinalysis done?

• To check overall health 

• To diagnose 

• To monitor a condition 

• Pregnancy test & drug screening

What are the ways to evaluate urine in urinalysis?

1. Visually – clear, cloudy, color & odor 

2. Dipstick

3. Microscopic

What is the appearance of normal urine?

a. Green urine most probably is caused by?

clear, light yellow to amber

a. Bacterial infection (pseudomonas aeruginosa)

• Food coloring 

• Increased carotene diet

• Oxalate poisoning 

• Oxaluria

• Phenol poisoning

What is the normal pH of urine?

4.5 – 8

Describe a normal (N) urinalysis result in terms of…

• pH

• Specific gravity

• Protein

• Sugar

• Ketones

• Bilirubin

• RBC

• Hemoglobin

• Volume

• pH: 4.5 – 8

• Specific gravity: 1.010 – 1.025

• Protein: -

• Sugar: - 

• Ketones: -

• Bilirubin: -

• RBC: -

• Hemoglobin: - 

• Volume: 800 – 2,000 mL/day

Define the following terms…

a. Glucosuria

b. Proteinuria

c. Hemoglobinuria

d. Bilirubinuria

Glucosuria – glucose in urine

• filtered glucose is normally reabsorbed from the renal tubules into the blood w/ help of a protein carrier

• The concentration of glucose in the glomerular ultrafiltrate is more than the capacity of the carrier proteins

• Glucose not transported will “spill over” into the urine

Proteinuria – protein in urine

• May indicate an abnormal increase in permeability of the filtration barriers into the glomerular capsules

• Possible causes: renal infections (glomerulonephritis) or secondary to diabetes mellitus, jaundice or hyperthyroidism

Hemoglobinuria – hemoglobin in urine. Causes:

• Hemolysis is the systemic blood vessels (ex. Transfusion reaction)

• Rupture in the capillaries in the glomerulus

• Hemorrhage in the urinary system

• Menstrual period

Bilirubinuria – Bilirubin in urine. Causes:

• Increase rate of RBC destruction (ex. Hemolytic anemia)

• Liver damage (ex. Hepatitis or cirrhosis)

• Obstruction of the common bile duct (ex. gallstone)