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What does the urinary system do?
- Eliminates nitrogenous wastes, toxins, drugs
- Regulates homeostasis - water balance, Electrolytes, Blood pressure
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Organs of the urinary system:
- Kidneys
- Ureters
- Urinary bladder
- Urethra
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Where are the kidneys located?
- Level T12 - L3Right kidney slightly lower than the left
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What are the coverings of the kidneys?
- Renal Capsule - surrounds each kidney
- Adipose Capsule - surrounds kidney, provides protection, keeps in correct location
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3 Regions of the kidney:
- Renal Cortex - outer region
- Renal Medulla - inside cortex
- Renal pelvis - inner collecting tube
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Kidney Structures:
- Medullary Pyramids - triangular regions
- Renal Columns - cortex material inward
- Calyces - funnel urine toward the pelvis
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What are nephrons?
- Functional unit of the kidney
- Responsible for forming urine
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What are the main structures of a nephron?
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What is the Glomerulus?
Entertwined bed of capillaries that filters blood before urine formation
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What are the parts of the renal tubule?
- Glomerular Capsule (Bowmans)
- Proximal Convoluted Tubule
- Loop of Henle
- Distal Convoluted Tube
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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
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What is the urine formation process?
- Filtration
- Reabsorption
- Secretion
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What happens during filtration?
- Passive process
- Water and solutes smaller than protiens forced through capillary walls
- Filtrate is collected in the glomerular capsule
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What happens during reabsorption?
- Peritubular capillaries reabsorb:
- Some water
- Glucose
- Amino Acids
- Ions
- Most reabsorption occurs in the proximal convuluted tube
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What materials are not reabsorbed in the urine process?
- Urea
- Uric Acid
- Creatinine
- Excess water
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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.
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Characteristics of urine:
- Colored yellow due to urochrome
- Sterile
- Slightly aromatic
- Normal pH around 6
- Specific gravity of 1.001 - 1.035
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What are the ureters?
Slender tubes attaching the kidney to the bladder
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What does the urinary bladder do?
Temporarily stores urine
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What is the trigone?
- 3 openings of the urinary bladder:
- Two from ureters
- One to the urethra
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How is the urinary bladder wall constructed?
- 3 layers of smooth muscle (detrusor muscle)
- Mucosa made of transitional epithelium
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What is the urethra?
Thin walled tube that carries urine from the bladder to the outside of the body
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What is the release of urine controlled by?
- Internal sphincter - involuntary
- External sphincter - voluntary
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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
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What is micturition?
- "voiding" or peeing
- Both sphincters must be open
- Impulse sent from spinal cord via the pelvic splanchnic nerves
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What is the normal amount of water in the human body?
- Young adult females - 50%
- Young adult males - 60%
- Babies - 75%
- Old Age - 45%
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What is the distribution of body fluid?
- Intracellular - 40%
- Extracellular - 20%
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What causes water to move from one compartment to another?
Changes in electrolyte balance
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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
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What is blood pH?
- Normal - 7.35 - 7.45
- Alkalosis - above 7.45
- Acidosis - below 7.35
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What controls acid balance in the body?
- kidneys
- blood buffers
- respiration
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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
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