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Human physiology (The urinary system Complete)
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covers all the structures and steps of the human urinary system.
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Lesson 18-20- Urinary system:The 6 Kidney functions:
● regulation of extracellular fluid volume and blood pressure
- ECF volume decreases, blood pressure decreases
- fall too low, not adequate blood supply to the brain
- kidneys work integrated with CVS to ensure BP and tissue perfusion
● regulation of osmolarity
- integration kidney function with behavioral drives (thirst)
- osmolarity w 290mOsM
- reflex pathways for regulation
● maintenance of ion balance
- keep concentrations of key ions
- normal range by balancing dietary intake with urinary loss
- sodium (Na+), major ion for regulation of ECF volume and osmolarity
- potassium (K +) and calcium (Ca2+)
● homeostatic regulation of pH
- narrow range of pH
- too acidic, kidneys remove H + and conserve bicarbonate (HCO− 3 )
- too alkaline, kidneys remove HCO− 3 and conserve H +
- do not correct pH as rapidly as the lungs
● excretion of wastes
- removal of metabolic waste products creatinine (muscle metabolism) and
nitrogenous wastes (urea and uric acid) urobilinogen, metabolite of
hemoglobin (yellow color) hormones
- removal of foreign substances drugs environmental toxins
● production of hormones
- kidneys aren't endocrine glands
1. erythropoietin synthesis (cytokine/hormone that regulates red blood
cell synthesis)
2. renin release
3. renal enzymes regulate Ca2+ balance
Anatomical overview:
- Consists of kidney, bladder,and ureters(connects kidney to bladder), urethra(expels
from bladder outside the body)
Macroscopy:
Route of water from plasma to excretion(urine production):
1. Water and solutes move from plasma to hollow tubes
2. These tubules modifies the composition of the fluid as it passes
3. Modified fluid leaves kidney and passes via ureters(one from each kidney) to the
urinary bladder
4. Bladder expands and fills with urine
5. Contracts and expels urine from the urethra
, ➔ The kidneys are the site of urine formation and they are located at the 11th &12th
ribs/ and below the diaphragm and outside of the peritoneal cavity
➔ Kidneys are a retroperitoneal organ
➔ Renal arteries supply blood to kidneys, renal vein carries blood from kin=denys to
inferior vena cava
➔ Kidneys receive up to 20-25% of cardiac output
➔ Interior is arranged in 2 layers
- Outer cortex
- Renal medulla
Nephron:
- The functional unit of the kidney
- 80% of nephrons in kidney are contained in the cortex cortical nephrons
- 20% of nephrons located in= juxtamedullary nephrons
● Nephrons are divided into sections:
- Nephron begins with a hollow ball like structure called Bowman's Capsule
contains which surrounds the glomerulus
● This fusion of the bowmans and the glomerulus is called Renal Corpuscle
- From the bowman's capsule, the filtered fluid flows into the proximal tubules
then falls into the loop of henle
- Loop of henle is divided into a thin ascending limb and an ascending limb
which is thin then becomes thick.
- The fluid passed into the distal tubules then all the fluid is collected by
common collecting ducts
- Collecting ducts pass from cortex through medulla then drain into renal pelvis
- Renal pelvis= will collect urine from each of the medullary parts of the kidneys
into the calyx
- Ureters take it into bladder> then urethra
Vascularization:
- Makes filtration of nephron possible
1. Blood enters kidney from Renal artery then flows into smaller arteries then
arterioles that flow into the cortex
2. Portal system=leaves the irrigation of an organ(hepatic portal system &
respiratory portal system
3. Blood flows from afferent arteriole into the glomerulus(capillaries inside
bowman's capsule)
4. Flows into efferent arterioles then into a second set of capillaries=peritubular
capillaries that surround each of the tubules of the nephron
5. Or goes to in the juxtamedullary nephrons, the long peritubular capillaries are
called the =Vasa recta(associated with loop of henle)
6. Renal capillary join to form the veins to remove blood via intertubular vein
then renal vein
Functions depending on location of nephron:
● Bowman's capsule= filtration
● Proximal tubule=reabsorption + secretion
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