Urinary System

Myth or Fact?• 1. Urinating on a jellyfish sting will help alleviate the

pain.   FALSE

2. It is safe to drink your own urine.Short term – YES, Long term – NO 

3. If someone is sleeping and you put their hand in warm water, they will pee their pants. FALSE

4. Holding your urine can cause a bladder infection.

5. There is a fish that will follow a urine stream and enter the urethra. FALSE

Functions of the Urinary System

Cells produce waste that can become toxic if they accumulate

The urinary system functions to:• removes salts and nitrogenous

wastes• maintains normal concentration

of water and electrolytes• maintains pH, controls red blood

cell production and blood pressure

Composition of the Urinary System

• consists of a pair of KIDNEYS which remove substances from the blood

• URETERS which transport urine from the kidneys to the bladder

• urinary BLADDER stores urine• URETHRA conveys urine to the outside of the

body

KIDNEYSKIDNEYS

URETERS

BLADDER

SPHINCTER URETHRA

Kidneys • Lie on either side of the

vertebral column deep in the abdominal cavity

• positioned behind the parietal peritoneum (retroperitoneally)

• lateral side is convex, medial is concave, kidneys sit in a depression called the renal sinus

• Entrance is called the HILUM

-Superior end of the kidney forms a funnel shaped sac - renal pelvis-renal medulla = center of the kidney-renal cortex = outer shell around the medulla; the cortex appears granulated due to the presence of nephrons-renal arteries and veins supply blood to the kidneys

Kidneys

The nephron is the functional unit of the kidney

Renal Arteries and Veins

• Arteries attach to the abdominal aorta

• Veins attach to the inferior vena cava

• Interlobar arteries pass between the renal pyramids

• Afferent arterioles lead to the nephrons

NEPHRONS - functional unit of the urinary system

• Quick Analogy: A nephron is to the urinary system as the _________________ is to the nervous system

• -each kidney contains about 1 million nephrons-renal corpuscle: composed of a tangled cluster called a glomerulus which filters fluid

• Pathway = glomerulus -> proximal tubulue --> nephron loop (also called loop of henle) --> distal tubule --> collecting duct --> ureter --> bladder

What blood vessel enters the glomerulus?

Urine Formation• (1) Glomerular filtration

- urine formation begins, plasma is filtered

• (2) Tubular reabsorption - returns most of the fluid to the body

• (3) Tubular secretion - removes what is not needed; produces urine

Glomerular Filtration

• Involves the filtration of blood plasma in the glomerulus

• Increased blood pressure in the glomerulus forces water and dissolved molecules to move from the lumen (walls) of capillaries, across the filtration membrane, and into Bowman’s capsule

• Larger sized proteins DO NOT pass through the filtration system; they exit through the arterioles

Glomerular Filtration• The walls of

the glomerulus contain pores

• The size of the pores determines what size substances can pass through the glomerulus

Tubular Reabsorption

• Glomerular filtration rate is so high, that the entire blood volume enters the tubules in less than 30 minutes

• Reabsorption of almost all the filtrate must occur quickly before dehydration occurs

• Tubular reabsorption is the process by which solutes and water are removed from the tubular fluid and transported into the blood. It is called reabsorption (and not absorption) because these substances have already been absorbed once (in the intestines).

• Majority of reabsorption occurs in the proximal convoluted tubule!

Tubular Reabsorption

• Substances can be reabsorbed through two ways:

• (1) Paracellular – substances diffuse between cells

• (2) Transcellular – substances pass through the cell

• Reabsorption can occur through passive transport (osmosis and diffusion) or active transport (Na+/K+ pump)

Aldosterone• Some hormones, like aldosterone, are responsible for

controlling reabsorption rates • Aldosterone is a steroid secreted by the adrenal

glands that is responsible for controlling the reabsorption of water and sodium

• Aldosterone regulates blood pressure by controlling the rate at which water and ions are reabsorbed. If it increases the rate of water and sodium reabsorption, more water and salt is retained, therefore increasing blood pressure.

• Diuretics act AGAINST aldosterone, decreasing reabsorption rates of water so more water is passed, lowering blood pressure

Tubular Secretion

• Tubular secretion has two main functions:• (1) regulate blood pH by secreting hydrogen

ions• (2) Secreting other substances removes them

from the body so that they will become urine• Secretion only occurs via ACTIVE TRANSPORT!

Tubular Secretion

• When the filtrate has arrived at the distal convoluted tubule, 80% of filtered water and more solutes (mostly sodium and chlorine) have been reabsorbed

• Tubular secretion occurs in the tubules, but mostly in the collecting duct

Urine Composition• 95 % Water• Contains urea and uric acid (characteristic

smell)• Can contain trace amino acids

• Urine may also contain other chemicals that can be detected.

• Hormones present in a pregnant woman are detectable in urine

Urine Elimination

• After urine forms in the nephrons, the ureters (starting with the renal pelvis) carry the urine away to the bladder

• Bladder is an expandable structure that stores urine before it is eliminated from the body.

• Transitional epithelial cells change shape to allow for expansion and contraction.

• Micturation = urination; as the bladder fills this reflex occurs though it is also under voluntary control

• Urethra = tube carries urine to the outside of the body

• Detrusor Muscle - attach to bladder and sphincter, control urination

Disorders of the Urinary System

• Many urinary problems can be solved by drinking enough water.

• So how much fluid does the average, healthy adult living in a temperate climate need? The Institute of Medicine determined that an adequate intake (AI) for men is roughly 3 liters (about 13 cups) of total beverages a day. The AI for women is 2.2 liters (about 9 cups) of total beverages a day.

Kidney Stones

• Extracorporeal shock wave lithotripsy (ESWL) is a procedure used to shatter simple stones in the kidney or upper urinary tract. Ultrasonic waves are passed through the body until they strike the dense stones, and make them smaller. Small pieces of the stone can then passed from the body.

• Cystitis = bacteria enters the bladder or kidneys (kidney infection); more common in women because the urethra is shorter

• Commonly known as a "bladder infection“

UTI = urinary tract infection

Frequent need to urinatePain in the abdomen Burning sensation during urinationCloudy, bad-smelling urineBlood in the urineLeaking urineLow back pain Fever and chillsNausea and poor appetite

Catheters• In medicine, a catheter is a tube that can be inserted into a

body cavity, duct, or vessel. • The process of inserting a catheter is catheterization.• Catheterization of the bladder is a common medical

procedure, often performed by nurses

• Overactive Bladder = sudden contractions of the bladder produce sensation of urgency, also more common in women

• Incontinence - inability to control urination (or defecation)

When Kidneys Fail....

• Dialysis may be used to clean the blood

(hemodialysis)• 4 hours, 3 times a

week• Patients will

eventually need a new kidney

• Domino Kidney Transplants or Kidney Exchanges - when you aren't a match for a family member, you can participate in a kidney exchange.