Topic 23: The Excretory System

Excretion (kiválasztás) refers to the removal of metabolic wastes from the cells together with the body.  It involves many organs:
- liver:  involved inwards detoxification, hemoglobin breakdown together with amino acid breakdown
- skin: via sweating
- lungs: removal of carbon dioxide
- urinary/excretory system: produces urine (vizelet)


The construction of the excretory system

http://www.tutorvista.com/content/biology/biology-ii/excretion-and-osmoregulation/excretion-osmoregulation-man.php

The excretory organization functions past times filtering the blood, reabsorbing of import compounds together with secreting wastes inwards the shape of urine, inwards gild to hold the body's fluid volume, pH together with electrolyte concentrations.

http://www.medindia.net/patients/patientinfo/acuterenalfailure.htm

The kidney (vese) is most 10cm long together with works life at the dorsum of the abdominal cavity.  It is surrounded past times the capsule, with the cortex forming the periphery of the kidney (lighter colour) together with the medulla forming the inner component (darker colour).  The nephron (nefron) is the functional unit of measurement of filtration.  There are most a 1000000 nephrons inwards each kidney, which run through the cortex together with the medulla.  The Bowman's  capsule and the glomerulus, along alongside the proximal together with distal convoluted tubules are works life inwards the cortex, volition the Loop of Henle runs into the medulla.

http://www.buzzle.com/articles/labeled-diagram-of-the-human-kidney.html

This ikon shows the component of the nephron works life inwards the cortex (ligter pink) together with the component inwards the medullar (darker reddish) of the kidney.  http://lyceum.algonquincollege.com/lts/onlineCourses/anatomy/content/module14-6.htm

Filtering process:

1.  Blood enters the glomerulus.  It is nether high pressure.  Many of its contents move past times across the capillary walls into the Bowman's capsule.  Water, glucose, vitamins, amino acids, carbamide (product of poly peptide breakdown), uric acid (product of nucleotide breakdown), ammonia, salts together with ions all brand upward the primary filtrate (szűrlet).  About 180L of primary filtrate is produced each day.  

http://faculty.pasadena.edu/dkwon/chapter%2019%20web%20page/chapter%2019%20urinary_files/frame.htm

2.  Reabsorption  occurs throughout the nephron, but varies inwards the unlike parts, depending on which transporter molecules are works life there.  Most of the carry out of the nephron is active (requires ATP), but around is passive together with motion of H2O occurs past times osmosis.

In the promixmal convoluted tubule essentially 100% of the glucose together with amino acids are reabsorbed.  Reabsorption of glucose requires carry proteins.  If a somebody has diabetes, together with therefore really high levels of blood glucose, these carry proteins can't carry all of the glucose out of the filtrate earlier it has flowed to the side past times side part, therefore glucose remains inwards the filtrate (and together with therefore the urine).  Thus glucose inwards the urine is a sign of diabetes.  About 2/3's of the ions such every bit sodium, potassium, calcium together with chloride are reabsorbed, together with therefore is most one-half the urea.  Meanwhile hydrogen ions, many medications together with toxins are secreted into the nephron.  While all this is happening most 2/3's of the H2O is likewise reabsorbed past times osmosis.

In the Loop of Henle, the decending loop allows for the reabsorption of water, spell the ascending loop allows for passive together with active carry of salts.  

In the distal convoluted tubule the reabsorption of the remaining H2O is subject on the presence of the hormone vasopressin (also called anti-diuretic hormone, or ADH for short).  It affects the H2O permeability of the tubule wall together with if it is present, together with therefore to a greater extent than H2O volition endure reabsorbed.  This is an active process.  Another hormone that plays a role inwards the distal convoluted tubule is aldosterone.  When it is acquaint to a greater extent than sodium is reabsorbed together with to a greater extent than potassium is secreted.  In addition, hydrogen ions together with ammonium are likewise secreted.

The collecting tubule/duct is commonly impermeable to water, but inwards the presence of vasopressin, becomes permeable.  Urea tin likewise cross the collecting duct.

http://en.wikipedia.org/wiki/Nephron

The liquid that flows out of the collecting duct into the renal pelvis is the in conclusion filtrate, or urine.  It is usually most 2L per day, but its quantity together with composition are subject upon hydration, what the private has consumed together with hormone production.  Standardly urine contains a mixture of water, salts, peculiarly NaCl, together with metabolic wastes together with toxins.  It should not incorporate whatever glucose or proteins.

The urine flows through the ureters, which are formed of polish musculus together with deport out peristaltic motion, to the bladder.  The bladder tin concord upward to 300-350ml of urine.  Pressure receptors inwards the bladder wall post signals to the encephalon most how total it is.   From the bladder, urine exits the torso via the urethra.  Emptying of the bladder is controlled past times sphincter muscles that are nether concious control.

Disorders:

Kidney stones:  crystalized minerals works life inwards the kidneys or the tracts of the urinary system.  If the stones are small, they only move past times through the system, but every bit their size increases they tin effort obstruction.  Kidney stones are known to effort excruciating pain.  Calcium-based stones are the most common, but other minerals tin likewise shape stones.  Risk factors for rock formation include dehydration, high dietary intake of poly peptide together with sugar, together with for sure metabolic conditions.

Infections:  Urinary tract infections are typically bacterial.  They are associated alongside fever, lower dorsum pain, pus inwards urine.  Chronic and/or serious infections tin atomic number 82 to problems alongside kidney function.

Bladder cancer: characterized past times blood inwards the urine.  Usually works life early on together with successfully treated.  Smokers receive got higher rates of bladder cancer.

Kidney failure:  characterized past times a reduction inwards the charge per unit of measurement of glomerular filtration

1.  Acute kidney failure -  it usually progresses rapidly, but alongside appropriate handling is likewise usually reversible.  Possible causes include loss of torso fluids, infections, hypertension, toxins, chemicals, etc

2.  Chronic kidney affliction - it usually progresses less rapidly, but is non reversible.  Possible causes include metabolic disorders, toxin accumulation, hypertension together with it oft shows an inherited predisposition.  Treatment includes dialysis (filtration of blood through a machine - non painful, but time-consuming) or kidney transplant.