Excretory System

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EXCRETORY SYSTEM
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What is Excretion?

• The process of ridding the body of waste in order
  to maintain homeostasis.

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Excretory System

• How does the excretory system maintain
  homeostasis?
• It regulates heat, water, salt, acid-base
  concentrations and metabolite concentrations

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ORGANS OF EXCRETION

• Skin and associated glands
• sweat is removed by skin as a waste product
  trying to Remove heat and salts
• Lungs Removes carbon dioxide
• Liver
• get rid of unneeded wastes in the body. It
  changes toxic ammonia, which is a poisonous gas ,
  to urea, a harmless fluid.
• Kidneys removes nitrogenous waste (urea)

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What is the Function of the Human Excretory
System?

• Maintain proper water balance in the body and to
  also remove liquid waste (urine)
• Kidneys filter approximately200L of blood or
  filtrate everyday
• Remove approximately 1-2 L of fluid everyday

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Parts of the human excretory System

• Kidneys
• Ureters
• Urinary bladder
• urethra

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Urinary System
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Kidneys

• Kidneys
• filter blood to produce urine.. Maintain water
  balance and rid body of nitrogenous waste (urine)
  created by the liver
• The kidney is a lima bean shaped structure found
  on both sides of the spinal column in the lower
  back

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The Kidney
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KIDNEY PARTS

• Kidney has three distinct regions
• Cortex
• the outer part
• Function filter blood
• Medulla
• the middle part made up of collecting ducts
• Function collect filtrate (filtered materials
  from the blood) and carries it to the renal
  pelvis
• Pelvis
• the inner cavity where urine collects. It is
  connected to the ureters
• Function Filtrate (now called urine) drains from
  the pelvis into the ureters for removal

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MAJOR FUNCTIONSOF KIDNEYS

• 1. Filters blood of
• Ø Urea formed in the liver from the breakdown
  of ammonia
• Ø Creatinine formed in the muscles
• Ø Uric Acid formed as a result of the breakdown
  of nucleic acids (DNA and RNA)

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• 2. Controls the balance of water in our bodies
• 3. Regulates pH of the blood
• 4. Regulates the concentration of dissolved ions
  in the blood

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• 5. Secretes a hormone that causes a production of
  red blood cells
• 6. Activates Vitamin D production in the skin

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Parts of Excretory system contd

• Urinary Bladder
• hollow muscular pouch located in the pelvis
• Function hold urine until it is released from
  the body. A typical bladder is able to hold up to
  about 500ml of urine.
• Urethra
• hollow tube leading from the bladder to the
  outside of the human body
• function carries urine from the bladder to the
  outside of the body.
• Ureters
• hollow tubes connecting the renal pelvis to the
  urinary bladder
• Function carry urine from the kidney to the
  urinary bladder

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IMPORTANT BLOOD VESSELS

• Renal Artery carries contaminated blood into the
  kidney.
• Renal Vein carries purified blood from the
  kidney and returns it back into circulation by
  way of the inferior vena cava.

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NEPHRONS

• Tiny filtering units called nephrons fill the
  cortex and medulla of the kidney.
• Basic functional unit of kidney responsible for
  filtering the blood and maintaining proper water
  balance
• Extends from renal cortex (glomerulus/ Bowman's
  capsule) into the renal medulla (loop of
  Henle)
• Each kidney contains 1 to 1.25 million nephrons.

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Parts of the Nephron

• Renal artery
• this is the artery that carries blood TO the
  kidney to be filtered
• Renal vein
• this is the vein that carries blood FROM the
  kidney AFTER it has been filtered
• Glomerulus
• A tight ball of blood capillaries located in the
  Bowman's capsule of Nephron.
• Blood pressure created here causes material to be
  filtered from the blood
• Bowman's capsule
• A cup shaped structure that receives filtrate
  from the Glomerulus
• Proximal tubule
• tube connected to the Bowman's capsule.
• Filtrate enters the proximal tube from the
  Bowman's capsule.
• Reabsorption of Amino Acids and Glucose occurs
  here

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• Loop of henle
• long u shaped tube that extends into the renal
  medulla. Responsible for maintain salt balance by
  reabsorption or releasing salt in the filtrarte
• Distal tubule
• tube extending from the loop of henle.
• It also reabsorbs materials from the filtrarte .
  Tubular secretions occurs here. Materials such as
  creatinine and drugs are added to the filtrate
• Collecting tubule
• tube that extends from the distal tubule to the
  renal pelvis. This portion of the nephron is
  mainly responsible for reabsorption of water

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Nephron Function (4 stages)

• 1. Filtration
• Blood travels from the renal artery, to an
  arteriole and then into the glomerulus, a mass of
  capillaries surrounded by the Bowmans capsule.

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• Blood pressure forces some plasma of the blood,
  containing both waste and useful material, into
  the Bowmans capsule. This material is called
  the nephric filtrate.

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• The filtrate contains such things as water,
  urea, uric acid, salt, glucose, amino acids, ions
  and vitamins.

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• 1. Filtration
• Filtration Hydrostatic pressure (blood
  pressure) forces
• water and dissolved substances out of the
  glomerular blood into Bowmans capsule.
• H2O, glucose, amino acids, electrolytes, wastes
• Averages 125 ml/min for both kidneys
• Æ180 liters/day
• The vast majority of the filtrate must be taken
  back

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2. Re-absorption

• From the Bowmans capsule the filtrate is pushed
  into the proximal tubule. The process of
  re-absorption, of useful materials within the
  filtrate, into the capillary network that
  surrounds the nephron than begins.

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• Reabsorption occurs by osmosis, diffusion, and
  active transport
• Reabsorbed materials include water, glucose,
  amino acids, ions and vitamins

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• When the filtrate reaches the end of the distal
  tubule the solution is isotonic (the filtrate and
  the surrounding cells have the same concentration
  of water and solutes).

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• The filtrate then moves down the descending loop
  of Henle as the loop descends further into the
  inner medulla, sodium concentrations in the
  surrounding tissue increase which draws water out
  of the filtrate (by osmosis).

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• At the bottom of the loop sodium ions in the
  filtrate are at high concentration and therefore
  diffuse out of the tubule.

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• Positive sodium ions are followed by negative
  chloride ions
• Water cannot reenter the ascending loop because
  this loop is impermeable to water

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• H2O - osmosis
• NaCl - active transport
• Glucose, amino acids - active co-transport

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3. Secretion

• Occurs in the distal tubule
• Involves active transport of substances from the
  capillaries into the tubule
• Substances include hydrogen ions, creatinine and
  drugs

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4. Elimination

• The fluid than enters the collecting duct as
  urine. It passes through the pelvis into the
  ureter.
• Most of the water, ions and useful nutrients
  (glucose, amino acids) have been reabsorbed.

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Path of filtrate through nephron

• Bowmans capsule - proximal tubule - loop of
  Henle - distal tubule - collecting duct

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Control of Water Balance

• When water levels are too low
• The hypothalamus stimulates the pituitary gland
  to secrete a hormone called anti-diuretic hormone
  (ADH) or Vasopressin. ADH travels through blood
  to kidneys.

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• 2) ADH increases the permeability of the tubules
  and collecting ducts
• 3) More water is reabsorbed into the blood so the
  urine is more concentrated

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• When water levels are too high
• Hypothalamus doesnt stimulate ADH secretion
• Little water is reabsorbed into the blood so the
  urine is more dilute.

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Other

• Aldosterone affects distal tubule and collecting
  tubule to reabsorb sodium ions
• ANP( atrial natruuretic peptide increase
  glomerulus filtration rate by dilating the
  arterioles and inhibits the collecting ducts from
  reabsorbing sodum.

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Excretory System Disoders

• These are problems associated with the kidneys,
  bladder , or ureters
• We will examine the following disorders
• 1. Urinary tract Infections
• Cystitus
• Ureyhritis
• Pyelonephritis
• 2. Kidney stones
• 3. Kidney Failure

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Urinary Tract Infections UTIs

• These are Bacterial Infections of the kidneys,
  bladder or Urethra
• There are 3 types of UTIs
• 1. Cystitis- infection of the bladder
• 2. Urethritis- infection of the urethra (tube
  leading from the bladder to the outside of the
  body)
• 3. Pyelonephritis- infection of the kidney

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Causes of UTIs

• Bacteria from the anus (females
• Blocked prostate (men)
• Bacterial infection from other areas of the body
• Note UTIs are more common in females than males

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Symptoms of UTIs

• Painful urination
• Burning sensation
• Bloody or brown urine
• Chills, fever, nausea

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Danger and Treatments

• Danger of UTIs
• Permanent damage to the kidneys and possible
  kidney failure.
• Treatments of UTIs
• antibiotics

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2. Kidney Stones

• What are Kidney Stones?
• These are hard crystals of calcium oxalate or
  uric acid that foem in the kidney bladder or
  ureter/urethra
• Kidney stones form when materials in the urine
  solidify
• Kidney stones are more common in men than women

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Causes of Kidney Stones?

• Urinary tract infections
• Not drinking enough water
• Too much vitamin C and D

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Symptoms of Kidney Stones

• Severe pain in abdomen and back
• Blood in urine
• Nausea
• vomiting

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Treatments of Kidney Stones

• Change diet
• Drink lots of water
• Ultrasound( breaks them up so they can pass)
  called lithotripsy
• Surgery (open)
• Incision through the back (nephrolithotomy
• Insertion of thin telescopic instrument into
  urinary tract( ureteroscopsy)

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Kidney Failure

• When the kidneys are not working correctly, waste
  products and excess fluid can build up and the
  levels of sodium, potassium, phosphate and
  calcium are not regulated correctly. 

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• symptoms of kidney disease, which can include
• high blood pressure,
• excessive tiredness,
• fluid retention and
• possibly lower back pain.

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Causes

• Kidney damage can occur for a number of reasons
• diabetes,
• high blood pressure,
• infections and a group of diseases that affect
  the glomerulus. 
• The kidneys also need an adequate supply of
  blood, so if there is something wrong with the
  blood vessels to the kidney, such as a narrowing,
  this will prevent the kidneys from working
  efficiently.

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Treatments

• dialysis
• cleans and filters your blood using a machine to
  temporarily rid your body of harmful wastes,
  extra salt, and extra water. Hemodialysis helps
  control blood pressure and helps your body keep
  the proper balance of important chemicals such as
  potassium, sodium, calcium, and bicarbonate.
• Dialysis can replace part of the function of your
  kidneys. Diet, medications, and fluid limits are
  often needed as well. Your diet, fluids, and the
  number of medications you need will depend on
  which treatment you choose.

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• Kidney transplantation
• surgically places a healthy kidney from another
  person into your body. The donated kidney does
  enough of the work that your two failed kidneys
  used to do to keep you healthy and symptom free.