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Excretory System . Yummmmmm … Nephrons. Mind Maps. Get into groups of 3-4 – use iPads to create a mindmap On iThoughtsHD create a mind map on thoughts , ideas, knowledge. Functions on the Urinary System. Excretion of Metabolic Wastes Maintenance of water – salt balance

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excretory system

Excretory System

Yummmmmm… Nephrons

mind maps
Mind Maps
  • Get into groups of 3-4 – use iPads to create a mindmap
  • On iThoughtsHD create a mind map on thoughts, ideas, knowledge
functions on the urinary system
Functions on the Urinary System
  • Excretion of Metabolic Wastes
  • Maintenance of water – salt balance
  • Maintenance of acid – base balance
  • Secretion of hormones
excretion of metabolic wastes
Excretion of Metabolic Wastes
  • Excrete nitrogenous wastes
  • Urea is the primary nitrogenous waste
    • By product of nucleic acid breakdown
    • Liver releases ammonia (extremely toxic to cells)
    • Forms with carbon dioxide to form urea
    • If too much uric acid is present in the blood, can precipitate causing crystal = gout
  • Others wastes include methane
maintenance of water salt balance
Maintenance of Water-Salt Balance
  • Blood volume is closely associated with the salt balance of the body
  • The greater amount of salt in the blood, the greater the blood volume, the greater the blood pressure
  • Kidneys are responsible for filtering the blood of appropriate ions (Sodium, Potassium, Chloride etc…)
maintenance of acid base balance
Maintenance of Acid-Base Balance
  • Kidneys monitor and maintain a pH of 7.4
  • Excretes hydrogen ions
  • Reabsorbs bicarbonate ions
secretion of hormones
Secretion of Hormones
  • Assist in the endocrine function of the human body
  • Releases rennin which stimulates the release of aldosterone from the adrenal glands
    • Promotes the reabsorption of Na+ ions from the kidney
organs of the urinary system
Organs of the Urinary System
  • Consists of the kidneys, ureters, urinary bladder and urethra
  • Numbered off into groups 1-4, learn the specific function of the specific organ
  • Group 1: KidneyGroup 2: UreterGroup 3: Urinary BladderGroup 4: Urethra
  • 1 person is nominated to write brief description onto the board
the urinary system
  • Wastes filtered from blood by kidneys.
  • Wastes travel to bladder through ureters.
  • Kidney cross section:

Cortex: outer layer.

Medulla: inner layer.

Renal pelvis: hollow, central chamber.

gross anatomy of the kidney
Gross Anatomy of the Kidney

Renal Cortex: outer granulated layer that dips down

Renal Medulla: Consists of cone shaped tissues

Renal Pelvis: Is a central space or cavity that is continuous with the ureters

  • Multiple small tubes.
  • Functional unit of kidneys.
  • Afferent arterioles supply blood.
  • Branch into capillary bed or glomerulus.
  • Blood leaves glomerulus through efferent arterioles.
nephrons continued
  • Glomerulus surrounded by Bowman’s capsule.
  • Urine carried through proximal tubule (lined with microvili) to the loop of Henle (lined with simple squamous epithelium)
  • Urine continues to distal tubule (cuboidal epithelial cells) and into collecting ducts.
  • Collecting ducts merge in renal pelvis and expel urine into ureters.
glomerular filtration rate
Glomerular Filtration Rate
  • Occurs when the blood enters the afferent arteriole and the glomerulus
  • Due to glomerular blood pressure, water and other small molecules move from blood into the filtrated urine
glomerular filtration
Glomerular Filtration
  • Nephrons in kidney filter 180 liters of water per day ,including a small amount of molecules such as glucose and ions
  • Individual nephrons have own blood supply.
  • Blood moves through afferent arteriole into glomerulus.
  • Glomerulus under high pressure.
  • Solutes diffuse across glomerulus walls into Bowman’s capsule.
  • Materials move from high pressure to low pressure.
the filtrate
  • Not all blood components pass through capillary wall.
  • Small molecules and ions pass through easily.
  • E.g. Water, glucose, salts, amino acids.
  • Large molecules and structures remain in blood.
  • E.g. RBCs, platelets, proteins.
  • Urine formation water intensive.
  • Water and other important salts and molecules must be reabsorbed.
  • Active and passive transport used.
  • Na+ transported across nephron cell membrane.
  • Excess salts excreted in urine when threshold level reached.
  • Glucose and amino acids actively transported back into blood.
  • Some urea and uric acid is reabsorbed by this process.
  • Movement of wastes into nephron.
  • E.g. Nitrogenous wastes, surplus ions.
  • Active transport.
  • Mitochondria line distal tubule.
water balance
  • Increased water intake → increased urine production.
  • Increased exercise, decreased water intake → reduced urine production and concentrated urine.
antidiuretic hormone adh
  • Increases water reabsorption.
  • More concentrated urine results.
  • Produced by nerve cells of hypothalamus and stored in pituitary gland.
  • Pituitary gland releases ADH into blood.
  • Osmoreceptors in hypothalamus detect changes in body osmotic pressure.
  • Hypothalamus shrinks and sends nervous signals to pituitary gland.
  • ADH released into blood.
  • Thirst.
adh action on nephron
  • All parts of nephron not always permeable to water.
  • ADH makes upper section of distal tubule and collecting duct permeable to water.
  • High concentration of NaCl in interstitial fluid draws water back into interstitial space.
regulation of blood pressure
  • Kidneys regulate blood pressure by controlling blood volume.
  • Aldosterone produced in adrenal glands increases causing water reabsorption and increased blood volume.
renin angiotensin aldosterone system
  • Blood pressure receptors near glomerulus detect drop in blood pressure.
  • Renin released.
  • Converts angiotensinogen to angiotensin.
  • Blood vessels constrict.
  • Also stimulates release of more aldosterone.