What does the urinary system do?
- Eliminates nitrogenous wastes, toxins, drugs
- Regulates homeostasis - water balance, Electrolytes, Blood pressure
Organs of the urinary system:
- Urinary bladder
Where are the kidneys located?
- Level T12 - L3Right kidney slightly lower than the left
What are the coverings of the kidneys?
- Renal Capsule - surrounds each kidney
- Adipose Capsule - surrounds kidney, provides protection, keeps in correct location
3 Regions of the kidney:
- Renal Cortex - outer region
- Renal Medulla - inside cortex
- Renal pelvis - inner collecting tube
- Medullary Pyramids - triangular regions
- Renal Columns - cortex material inward
- Calyces - funnel urine toward the pelvis
What are nephrons?
- Functional unit of the kidney
- Responsible for forming urine
What are the main structures of a nephron?
What is the Glomerulus?
Entertwined bed of capillaries that filters blood before urine formation
What are the parts of the renal tubule?
- Glomerular Capsule (Bowmans)
- Proximal Convoluted Tubule
- Loop of Henle
- Distal Convoluted Tube
What are the types of nephrons?
- Cortical nephrons - located in the cortex, includes most nephrons
- Juxtamedullary nephrons - found at the boundary of the cortex and medulla
What is the urine formation process?
What happens during filtration?
- Passive process
- Water and solutes smaller than protiens forced through capillary walls
- Filtrate is collected in the glomerular capsule
What happens during reabsorption?
- Peritubular capillaries reabsorb:
- Some water
- Amino Acids
- Most reabsorption occurs in the proximal convuluted tube
What materials are not reabsorbed in the urine process?
- Uric Acid
- Excess water
What happens during secretion?
- Reabsorbtion in reverse:
- Hydrogen, potassium and creatine, move from the pertibular capillaries into the renal tubes
- Materails left in the renal tube move to the ureter.
Characteristics of urine:
- Colored yellow due to urochrome
- Slightly aromatic
- Normal pH around 6
- Specific gravity of 1.001 - 1.035
What are the ureters?
Slender tubes attaching the kidney to the bladder
What does the urinary bladder do?
Temporarily stores urine
What is the trigone?
- 3 openings of the urinary bladder:
- Two from ureters
- One to the urethra
How is the urinary bladder wall constructed?
- 3 layers of smooth muscle (detrusor muscle)
- Mucosa made of transitional epithelium
What is the urethra?
Thin walled tube that carries urine from the bladder to the outside of the body
What is the release of urine controlled by?
- Internal sphincter - involuntary
- External sphincter - voluntary
Urethra Gender Differences
- Females - 1 inch, along wall of vagina, only carries urine
- Males - 8 inches, through the prostate and penis, carries urine and semen
What is micturition?
- "voiding" or peeing
- Both sphincters must be open
- Impulse sent from spinal cord via the pelvic splanchnic nerves
What is the normal amount of water in the human body?
- Young adult females - 50%
- Young adult males - 60%
- Babies - 75%
- Old Age - 45%
What is the distribution of body fluid?
- Intracellular - 40%
- Extracellular - 20%
What causes water to move from one compartment to another?
Changes in electrolyte balance
What regulates water and electrolyte reabsorption?
- Antidiuretic hormone - prevents excessive water loss in urine
- Aldosterone - regulates sodium ion content of extracellular fluid
- Cells in the kidney and hypothalmus are active monitors
What is blood pH?
- Normal - 7.35 - 7.45
- Alkalosis - above 7.45
- Acidosis - below 7.35
What controls acid balance in the body?
- blood buffers
What are the developmental aspects of the Urinary System?
- Functional kidneys develop my 3rd month
- Bladder is small
- Urine cannot be concentrated
- Urine can be controlled by 18 months