1. Anatomy & Physiology H Chapter 15
Urinary System
Anatomy & Physiology H
Chapter 15

2. 15.1 Kidneys
The urinary system consists of the kidneys, ureters, urethra and the urinary bladder
The kidneys alone perform the functions of the urinary system;
Maintain the purity and concentration of internal fluids
Excrete nitrogenous waste
Regulate blood volume and chemical makeup
Secrete the enzyme renin to regulate blood pressure
Secrete the hormone erythropoietin to stimulate RBC production
Convert vitamin D to its active form

3. 15.1 Kidneys
The kidneys are located on the dorsal side of the body under the 12th rib
They are small dark red organs, shaped like kidney beans
The right is kidney is slightly lower than the left, due to crowding from the liver
Adult kidneys are about 5 inches long, 2.5 inches wide and about 1 inch thick

4. 15.1 Kidneys
Each kidney has an indentation called the renal hilus where the ureters and blood vessels enter
Atop each kidney is an adrenal gland
The renal capsule is a fibrous, transparent enclosure of each kidney
The adipose capsule of fat helps hold the kidneys in place

5. On page 503 in your book and expect it on the test

6. 15.1 Kidneys
When a kidney is cut lengthwise, three distinct regions are shown
The outer region, which is lightly colored is called the renal cortex
The middle region, called the renal medulla, is dark reddish-brown and contains triangle shapes called medullary pyramids
Near the hilus is the renal pelvis which is a basin like cavity

7. On page 504 in your book

8. 15.1 Kidneys Kidney blood supply;
About 1/4th of the total blood supply passes through the kidneys each minute
The arterial supply of each kidney is the renal artery which is a branch off of the aorta
As the renal artery approaches the hilus it branches into segmental arteries, which further branch (see next slide)

9. 15.1 Kidneys
Nephrons
Each kidney contains over a million functional units called a nephron
Each nephron consists of two main parts; a glomerulus (knot of capillaries) and a renal tube
The closed end of the renal tube is cup shaped and surrounds the glomerulus; its called the Bowman’s capsule or glomerular

10. 15.1 Kidneys The renal tube extends about 1.25 inches
PCT: proximal convoluted tubule is a twisted section of the renal tube just after the Bowman's capsule
Loop of Henle: after the PCT, a long loop of the tube surrounded by capillaries
DCT: distal convoluted tubule is a twisted section after the loop
Collecting duct: receives urine from the nephron

11. 15.1 Kidneys
On page 506 in your book and expect it on your test

12. 15.1 Kidneys Urine Formation
Filtration: nonselective, passive process that occurs at the glomerulus due to pressure in the blood
Tubular reabsorption: most occurs in the PCT, but some also occurs in the DCT and collecting duct
Most of the reabsorption is passive but some is active
Tubular secretion: reabsorption in reverse, primarily removing substances not already filtered

13. On page 508 in your book

14. 15.1 Kidneys Urine makeup and characteristics:
Urine contains urea (formed in the liver as an end product of protein breakdown) uric acid (released when nucleic acids are metabolized) and creatinine (metabolism in muscle tissue)
In 24 hours the kidneys filter from L of blood plasma and L of urine are produced
It is clear and pale to deep yellow (the more dilute the paler it is) The color is due to urochrome, a pigment that results from the breakdown of hemoglobin
Eating certain foods can temporarily color our urine

15. 15.2 Ureters, Bladder & Urethra
The ureters are slender tubes about inches long
A ureter runs from the hilus of each kidney along the back of the body and along the back of the bladder, entering the bladder on the posterior side at a slight angle
The ureters are passageways that carry urine from the kidney to the bladder

16. 15.2 Ureters, Bladder & Urethra
The bladder is smooth, collapsible, muscular sac that temporarily stores urine
The bladder is in the pelvic region
The trigone is the slightly triangular region just above the urethral opening in the bladder

17. On page 512 in your book

18. 15.2 Ureters, Bladder & Urethra
The urethra is a thin walled tube that carries urine, by peristalsis, from the bladder to the outside of the body
At the bladder-urethral junction is a thickening of smooth muscle call the internal urethral sphincter
Its control is involuntary and keeps the urethra closed when urine is not being passed (called micturition or voiding)
The need to void usually happens when the bladder contains about 200 ml, which causes it to stretch and impulses are sent to the spinal nerves to cause contractions that push urine past the internal urethral sphincter and tell you its time to go to the bathroom

19. 15.2 Ureters, Bladder & Urethra
The external urethral sphincter is made of skeletal muscle and is voluntary
The control of this is what is learned in potty training

20. 15.3 Fluid, electrolyte and Acid/Base Balance
Electrolyte changes cause water to move, severe changes can cause problems with blood volume and pressure
We need to make sure we take in more water than we lose and water isn't just lost through the formation of urine; we lose about 8% in sweat, 28% in through our skin and lungs ( we aren't aware of this) and about 4% in the production of feces

21. 15.3 Fluid, electrolyte and Acid/Base Balance
Reabsorption of water and electrolytes is regulated by the kidneys through hormones
ADH: antidiuretic hormone prevents the excess loss of water in urine
Aldosterone: regulates the sodium and other electrolyte levels
Renin: causes an increase in blood pressure and blood volume

22. 15.3 Fluid, electrolyte and Acid/Base Balance
Acid/Base balance is maintained by blood buffers
A buffer is a substance that can balance an acid or base
Most of fluids in in the body have a neutral pH (7)
For example if you have a stomach ache it is usually because it is over acidic so you take Pepto (which is basic) to counteract it