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Renal Artery Renal Vein
Adrenal GlandRenal Cortex
Renal Pelvis
KidneyRenal Medulla
Ureter
Urinary Bladder
Urethra
• Skin excretes water and salts in perspiration
• Lungs excrete CO2 as a gas
• Liver excretes bile pigments
• Kidneys excrete nitrogeneous wastes in urine
Role of Kidneys
• Important in protein breakdown (proteins are amino acid based which is nitrogen based)
• Nucleotides (metabolic products) are metabolized to form uric acid
• Uric acid is not very soluble - if it precipitates out of solution, you have gout
What do kidneys do?
• 2 kidneys located high up in the abdomal cavity
• Purposes - • filter blood• maintain blood volume• remove waste products• recover vital substances• Maintains homeostasis in the body
• Little bit of protection by rib cage
• Covered by tough fibrous cap of connective tissue - surrounded by adipose tissue (inside fibrous tissue)
Ureters
• Ureters connect bladder to kidney - smooth muscle
• Ureters and bladder made of transitional epithelium
• Urinary bladder can stretch to accommodate up to 600 ml or more (sometimes in excess of 1000ml) (600 ml is conservative)
• has folds - rugae (like folds of stomach) - running throughout is smooth muscle fibers
• Urethra extends from bladder to outside the body
• Females urethra is about 1-2” - this leads to more frequent urinary tract infections
• Male urethra is about 6” - prostate in later years can enlarge (very often does) which causes an obstruction in urine flow
• Histology of Kidney
• Bean shaped
3 regions
• Cortex
• Medulla which contains renal pyramids (appear striated)
• Renal Pelvis (or inner space) - continuous with ureter
Nephron
• Plasma minus the proteins pass through filtration cells, then you need to recover vital molecules - glucose, water, etc.
• over 1 million nephrons
• Nephron is the filtration unit of the kidney - made of cells that are specialized for active transport, diffusion, moving substances across membranes
Nephron
• Structure of nephron
• cup shaped structure - Bowman’s capsule
• Parts of nephron beyond Bowman’s capsule
• specialized tube
Nephron
• part closest to glomerulus is the proximal convoluted tubule (closest to renal corpuscle
• Loop of Henley or Henley’s Loop - descending and ascending limb with a hairpin turn
• Distal convoluted tubule - farthest away from renal corpuscle
• each has a role in recovery of nutrients and leads away from nephron to collecting duct and away
Formation of Urine
• Pressure Filtration• Blood from arteriole is flowing into
glomerulus, due to bp, filtration• Everything from plasma that is filterable
leaves through glomerulus - water, glucose, amino acids, salts, urea, uric acid and creatinine (nitrogen wastes)
• blood cells, platelets and proteins are not filtered
• Concentration of water is same as plasma
• Body needs to recover water and nutrients
• Selective Reabsorption
• Almost 180 L of filtrate pass into collecting tubules per day. 90 - 2L bottles!
• Diffusion and active transport (passive and active processes)
• water glucose amino acids and salts are reabsorbed. About 99% of the water is reabsorbed.
• Region most highly specialized for selective reabsorption is the proximal convoluted tubule
• Many mitochondria needed - produce atp for active transport
• Reabsorption of water
• happens in loop of Henle
• Lower part of ascending limb - dealing with passive diffusion of NaCl
• Regulate pH of blood by regulating particular ions
• Beside filtration, keeping good stuff and getting rid of waste
• Maintaining blood volume
• ADH - Produced in Hypothalamus by neurosecratory cells, stored and secreted from posterior pituitary gland
• ADH increases the permeability of the collecting duct to water so more water can be reabsorbed.
• Increase Blood Pressure and Blood Volume• Diuresis - increases amount of water in urine• Alcohol is a diuretic - decreases production of
ADH• Believed after effects of alcohol (hangover) is
due to dehydration• Kidney stones - calcium salts or uric acid
precipitate and form kidney stone