kidney anatomy & function. organs of the urinary system figure 15.1a
TRANSCRIPT
Coverings of the Kidneys• Fibrous capsule– Surrounds each kidney, transparent
• Perirenal fat capsule– Surrounds the kidney and cushions against blows
Regions of the Kidney
Figure 15.2b
•Renal cortex—outer region•Renal medulla—inside the cortex•Renal pelvis—inner collecting tube
Kidney Structures• Renal pyramids—triangular
regions of tissue in the medulla
• Renal columns—extensions of cortex-like material inward; separate the pyramids
• Major/minor calyx —tubes that funnel urine towards the renal pelvis
Blood Supply• One-quarter of the total blood supply of the
body passes through the kidneys each minute• Renal artery provides each kidney with arterial
blood supply• Blood leaves the kidneys through the renal
veins
Nephron Anatomy and Physiology• The nephron is the structural and functional
unit of the kidneys• More than 1 million per kidney• Responsible for forming urine• Main structures of each nephron– Glomerulus (knot of capillaries)– Renal tubule
http://www.youtube.com/watch?v=C-Ub0Df44Wk
Nephron Anatomy• Renal tubule extends from
glomerular capsule and ends at the collecting duct– Glomerular (Bowman’s) capsule– Proximal convoluted tubule
(PCT)– Loop of Henle– Distal convoluted tubule (DCT)
http://www.youtube.com/watch?v=C-Ub0Df44Wk
1. Glomerular Filtration • Moves: water &
solutes smaller than proteins
• Non-selective& passive
• Fluid = filtrate• Works b/c there’s high
pressure in the capillaries
2. Tubular Reabsorption
• Moves: water, glucose, amino acids, & ions into peritubular capillaries (reabsorbed)
• Depends on body’s needs• Occurs in entire renal tubule – most in proximal convoluted
tubule• Some substances move passively
(water osmosis)• Most move via active transport
(glucose, amino acids)
3. Tubular Secretion • Moves: hydrogen ions,
potassium ion, & creatinine into filtrate from blood into filtrate to be excreted
• Helps get rid of substances not already in filtrate such as drugs or excess potassium
• Helps regulate blood pH
Take out a sheet of scrap paper and…
• Define filtration and list 3 things filtered out of the blood
• Define tubular reabsorption and list 3 things that are reabsorbed
• Define tubular secretion and list 2 things that are secreted
Put your name on top and pass it up.
• Kidneys keep these in normal ranges:– Water– pH– Electrolytes
• Kidney allow for the removal of – Nitrogen-containing wastes (urea & uric acid)– Creatinine (from muscle metabolism)
Renal Homeostatic Control
Major Fluid Compartments of the Body
Figure 15.8
Intracellular fluid- in cells
Extracellular fluid- NOT in cells
So then anti-diruetic hormone…• Action: causes water to be reabsorbed
from filtrate• Where: in the DCT & Collecting Duct• How: adds more aquaporins, therefore
more water is reabsorbed• So then why does…
– (alcohol prevents ADH from doing its job, you excrete needed water
pH Balance in Blood & its Regulators
• Buffers are the first line of defense work almost instantaneously
• Secondary defenses take longer to work:– Respiratory mechanisms take several minutes to hours– Renal mechanisms may take several days
Bicarbonate
Aldosterone• What: Hormone that affects Na+
reabsorption
• When released: If blood is diluted & low in volume (from adrenal gland)
• Effect: causes more sodium to be reabsorbed fixes concentration… BUT what about the low volume?
• Where: Works on DCT and collecting duct
Addison’s Disease• Description: Inability to
produce enough aldosterone
• Cause: adrenal glands get attacked by the immune system
• Incidence: 3/100,000 of all ages and sexes
• s/s: chronic fatigue, muscle weakness, loss of appetite, weight loss, low BP, cravings for salty foods
Kidneys help keep Blood Homeostasis by:
1. Maintaining water • Regulates blood volume & BP; uses ADH
2. Regulate pH (~7.4)• HCO3- and H+
3. Keeping electrolytes in balance• Regulates ion/electrolyte levels; uses aldosterone
4. Excretion of nitrogen-containing wastes • Urea- protein amino acids ammonia urea
• Uric acid when nucleic acids are broken down• Creatinine doesn’t have nitrogen but still waste from muscle
metabolism
Contents of Urine• Filtrate vs. urine• Should have: sodium & potassium ions, nitrogen-
containing wastes, ammonia, bicarbonate ions• Should not have: glucose, blood proteins, RBCs,
Hemoglobin, WBCs, bile• Sterile• Colored• pH• Aroma• Density/specific gravity