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Unit 12 – Assignment 1 – P1
The kidney

There are three regions of the kidney: an outer cortex, a middle medulla and an inner pelvis
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These are microscopic, multicellular structures
which have the form of a long tube (around 3cm long)
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http://blindnessinlight
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com/2010/08/kidney
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umich
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htm

Inside the cortex are the renal capsule and the first and second convoluted tubule
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The collecting ducts deliver the urine into
the pelvis
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The ureter connects the kidney to the bladder
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The arterioles divide
into a knot of capillaries; these are called the glomerulus which is found in the cup of each renal
capsule
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The network surrounds the first and second convoluted tubules and the loop of
Henle
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http://www
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pe
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htm

The function of the kidney has three main processes:
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•

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Ultrafiltration: This occurs in the renal capsule
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The filtrate contains the waste products and
useful substances for the body
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Selective reabsorption: This process occurs in the second convoluted tubule and the
collecting duct
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Concentration: This occurs in the second convoluted tubule and the collecting duct
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This allows the concentration to
occur
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Extracellular fluid
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How fluids can get into the body:
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•
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Through liquids consumed
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Inhaling
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How fluids can get out of the body:
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•
•
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The urinary system (kidney)
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e
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Through skin (i
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sweat)
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e
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Fluids and electrolytes
Homeostasis: Homeostasis means to maintain a constant internal environment, or the state of
equilibrium in the body with respect to various functions and to the chemical compositions of the
fluids and tissues
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Efficient
functioning of organs and systems maintain homeostasis
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The function of water in the body is to maintain the body
temperature; to maintain the cell shape; to transport nutrients, gases and waste
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Water is a solvent, a lubricant and changes temperature at a slow rate
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Outside the cell – Extracellular (ECF) (1/3)
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Lymph - Water in lymphatic vessels
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Specialised fluid – Synovial fluid, cerebrospinal fluid aqueous humor in the eye
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This makes up around 2/3 of the total body water
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Minor components include all other extracellular fluids
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Hypervolemia – excess of isotonic fluid in the extracellular space
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Organs that regulate water balance:
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•
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•
•
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•
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Lungs – CO2, O2 and H2O
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Blood – pH level
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Digestive system – elimination of water
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In the hypothalamus, osmoreceptors sense
changes in the osmolality of body fluids
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ADH – anti diuretic hormone
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Aldosterone – stimulated to reabsorb sodium ions in the kidney's renal cortex
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They are substances that separate into ions
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Most of them are inorganic salts, acids and bases
found in all body fluids
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They
are lost with output, I
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sweat, vomit or urine
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It
may later cause dizziness, confusion, weakness and a low BP shock
Hypernatremia (high sodium ions) - This causes excessive water loss or sodium ingestion
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Electrolyte imbalances outside the cell:
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•
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Hypokalaemia (low potassium ions) - This causes vomiting, diarrhoea and renal disease
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Hyperkalaemia (high potassium ions) - This causes acute renal failure and Addison's disease
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Hypocalcaemia (low calcium ions) - This causes hypoparathyroidism or decreased calcium
ion intake
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Hypercalcaemia (high calcium ions) - This causes hyperparathyroidism
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Water balance
Kidneys maintain the water balance in the body
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The kidneys can also control the salt levels and the excretion of urea
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Kidneys can conserve water; this is done by producing
concentrated urine relative to plasma
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The direct control the kidney has of
water excretion is carried out by the hypothalamus secreting hormones; i
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ADH (anti-diuretic
hormone), which is a peptide hormone
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This is
done by placing water channels in the membranes of cells that line the collecting ducts
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The secretion of ADH occurs due to a number of factors:

•

•

•

When the plasma becomes too concentrated, receptors in the hypothalamus causes the
secretion of the hormone
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If the blood levels returning to the heart from the veins are high, stretch receptors in the
atria are activated
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On the other hand, If the blood levels are low, stretch receptors in aorta and carotid arteries
are activated
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Diffusion of molecules across a selectively permeable artificial membrane

9
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Record the colour changes, if any, in the results tables below
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If the strips are light blue there is no glucose
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If the
solution stays yellow, there is no starch content
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This means that some of the glucose had
diffused through the selectively permeable artificial membrane
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This means that starch was not present in the solution
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This means that some of the glucose
had diffused through the selectively permeable artificial membrane
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This
means that starch was not present in the solution
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In solution C, the colour of the solution had stayed light blue throughout (0 on the colour scale)
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For the iodine test, after put into the water bath
for 15 minutes at 30 degrees Celsius, the colour of the solution was yellow
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As the colour of the solution inside the visking tube and at the
beginning was purple, I can conclude that the starch had not diffused through the selectively
permeable artificial membrane
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blogspot
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html

Results:

This graph shows that overall, as you increase the concentration of sucrose in which the potatoes
are submerged, the percentage weight decreases
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The average percentage difference in
weight was 10%
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3 molarity
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If my results had been more accurate, the higher the concentration of sugar in the solution,
will mean a higher loss of weight for every one
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The more dilute
the solution is, the lesser the loss of weight
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If this was not applied to every tubule, then this could significantly make the results differ
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This will make the solution contaminated and cause inaccuracy
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This means that the outcome may be completely different than
what is supposed to happen; making the potato differ in weight
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If I were to do this experiment again, I would ensure that I used the right pipette to put each solution
in the measuring cylinder; this is so that the solution will not be contaminated with another, which
could cause the outcome may be completely different than what is supposed to happen; making the
potato differ in weight
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In addition, I would have ensured that the mass of
each potato tubule were the same, if not very close
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3g, this
could have affected my results causing them to be inaccurate
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This is to ensure that parallax error will not
involved in the errors of this experiment
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Finally, I
would take more time drying the potato tubules so that there would be little moisture left, this
would be to ensure that my results are accurate and to reduce the error
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Specialised proteins called transporters are located on the membranes
of the various cells of the nephron
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Each transporter grabs only one or two types of molecules
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Transporters are connected in different parts of
the nephron
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Since transporters require energy, usually in the
form of adenosine triphosphate (active transport) whilst others do not (passive transport)
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Other molecules get reabsorbed passively
when they are caught up in the flow of water; this is called solvent drag
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This is set up by the reabsorption of Na
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In facilitated diffusion, glucose is removed from the filtrate and goes down a concentration
gradient to the cells of the first convoluted tubule
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This process
has two effects:
•
•

It will maintain a concentration gradient between the filtrate and the cells of the first
convoluted tubule
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Glucose is able to diffuse through the capillaries and is carried away in the blood
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google
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uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0
CAcQjRxqFQoTCNHElNPn08gCFUHHGgodioUPcA&url=https%3A%2F%2Fwww
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com%2Fnot
es%2Fnote%2Fn%2Flec-32%2Fdeck%2F4432112&psig=AFQjCNFb0pjQwQHUtkxmMhRj8NODnuMpA&ust=1445525296611462

http://1
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blogspot
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gif
Amino acids: The process of sodium-amino acid cotransport is vital so that amino acids can be
reabsorbed into the proximal tubule
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They diffuse from the filtrate
into the cells lining the proximal convoluted tubule
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Urea and water: The reabsorption and active secretion of urea will lead to a urea circulation
between the lumen of the nephron and renal medulla
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The urea will then be secreted
into the thin ascending limb of Henle loop; therefore large quantities of urea will be transported to
the distal nephron
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This
process allows a high-osmolar urea gradient to form in the renal medulla
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files
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com/2013/03/42_17_water_reabsorption-l1
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A
base is a substance that decreases the concentration of hydrogen (H+) ions in water and/or increases
the concentration of hydroxyl (OH-) ions, otherwise known as alkaline substances
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The value of 7 is
considered to be neutral as it contains an equal number of H+ and OH- ions
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357
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Urine is acidic, stomach contents are very acidic and intestines
are alkaline
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Normal
metabolism tends to make body fluids more acidic, therefore it must be continuously corrected by
the body
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There are many processes, both chemical and physiological, that acid-base homeostasis involves
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These chemical processes are a defence mechanism towards an acid or base load and include the
extracellular and intracellular buffers
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It also adjusts the structure by modifying responses in the
excretion of volatile acids by the lungs and fixed acids by the kidneys
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The acid-base balance
systems are:
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•
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Buffer
Respiratory
Renal
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If a potential pH change is
created by a strong acid, the strong acid will react with the sodium bicarbonate, to produce salt and
a weak acid which has little effect on pH
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During normal metabolism, fluids tend to become more acidic, so more sodium is needed
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There are two components of the phosphate buffer system: a weak acid and a weak base
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The phosphate buffer system is
important in the regulation of the pH in the blood by the kidneys
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They cannot prevent great changes in
pH because only limited number of buffer molecules are present,
The respiratory system can cause changes in pH and can compensate for metabolic changes in pH
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to cause
increased exhalation of CO2 which will decrease the H+ ion formation and increase pH back to
normal
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This causes a
retention of CO2 which allows an increase in H+ ion formation which will lower the pH back to
normal
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In the renal system, the kidneys help regulate the pH in the ECF by excreting or conserving H+ ions,
Na ions and HCO3 ions as the pH fluctuates
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However, it does have the greatest ability to buffer an ongoing pH
change

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