The urinary system functions to regulate homeostasis by controlling water, electrolyte, and acid-base balance and eliminating waste from the body. The major organs of the urinary system include the kidneys, ureters, urinary bladder, and urethra. The kidneys filter waste from the blood to form urine and are made up of nephrons, the functional units that filter blood and remove waste. Urine is formed through the processes of filtration, reabsorption, and secretion in the nephrons and is temporarily stored in the bladder before being excreted through the urethra.

1. Essentials of Human Anatomy & Physiology
The Urinary System
Anatomy & Physiology II
Mr. Hildebrandt

2. Urinary System Functions
Regulates homeostasis:
Water & Electrolytes
Blood pressure & pH
Red blood cell production
Elimination of waste products:
Nitrogenous wastes
Toxins
Drugs

3. Urinary system Organs
Kidneys
Ureters
Urinary bladder
Urethra

4. The Kidneys
Against dorsal body
wall
Right kidney is slightly
lower than the left
3 Regions:
Renal cortex – outer
region
Renal medulla – inside
the cortex
Renal pelvis – inner
collecting tube

5. Kidney Characteristics
Attached to ureters, renal
blood vessels, and
nerves at renal hilus
Atop each kidney is an
adrenal gland
Renal capsule - Surrounds
each kidney
Kidney stones – filtrate
concentrates, crystallizes
and forms stony masses

6. Ureters
Slender tubes attaching the
kidney to the bladder
Continuous with the renal
pelvis
Enters posterior portion of the
bladder
Runs behind the peritoneum
Peristalsis aids gravity in
urine transport

7. Urinary Bladder
Smooth, collapsible, muscular sac
Temporarily stores urine

8. Urethra
Thin-walled tube that carries
urine from the bladder to
the outside of the body by
peristalsis
Release of urine is controlled
by two sphincters
Both sphincter muscles must
open to allow micturition
(voiding)

9. Urethra Gender Differences
Function:
Females – only carries
urine
Males – carries urine &
sperm cells
Length:
Females – 3–4 cm (1 inch)
Males – 20 cm (8 inches)

10. Nephrons: filter “junk” out of blood
Structural & functional units of kidneys
Responsible for forming urine
Nephron structures:
Glomerulus
Bowman’s capsule
Proximal convoluted
tubule
Loop of Henle
Distal convoluted tubule
Collecting duct

11. Urine Formation Processes
Filtration - Water and
small solutes (filtrate) are
forced out of glomerulus &
into Bowman’s capsule
Reabsorption - Blood
capillaries reabsorb 99% of
water, glucose, amino acids,
& ions from renal tubule
Secretion - Hydrogen &
potassium move back into
renal tubules resulting in
urine

12. Formation of Urine

13. Characteristics of Urine
Colored somewhat
yellow due to the
pigment urochrome
and other solutes
1.8 liters produced
per day
Slightly aromatic
pH normally 6ish
Sterile

14. Maintaining the Balance
Water intake must equal water output
Blood pH must remain between 7.35
and 7.45 to maintain homeostasis
Kidneys increase water volume &
sodium in blood to control blood
pressure
Kidneys recognize hypoxia (low oxygen
levels) & responds:
Erythropoietin is released in blood
Bone marrow produces more RBCs