My revision notes: A2 Biology: EXCRETION + Kidney functions

Excretion - Removal of toxic waste products formed by metabolic reactions.

CO2 - from respirations

• Dissolves in H2O to form Carbonic acid >  lowers pH of blood and denatures enzymes
• Detected - by chemoreceptors/aorta > sends and impulse to the medulla bongata > increase rate and depth of breathing. If thi falls below the pH of 7.35 > find it difficult to breathe = respiratory acidosis. 
• Carbonic acid: CO2 + H2O > H2CO3
• H2CO3  >(dissolves in)> H+  +  HCO3- (hydrogen carbomate)
• H+  +  Hb (haemoglobin) > HHb (Haemoglobinic acid) 
• Which leads to Hb not being able to load enough O2 ad therefore reduce amount of O2 that Hb can load

Removal of urea by the kidney

KIDNEY FUNCTIONS

• Removes urea from blood to urine
• maintin water  potential of blood
• remove exceess ions etc

Different sections of the nephtons have different functions.

Ultrafiltration - takes place in the Bowman;s capsule

Blood contains - Red blood cells (RBC), white blood cells (WBC)

                        -Plasma, which contains - amino acids, glucose, H2O, CO2, O2, hormones, urea

Ultrafiltration filters the blood (plasma) but the RBC and WBC are too big to be filtered out. 

The capillary is made of endothermic cells which is very thing and flat an have tessellated margins. 

In the nephron, the afferent arteriole has a wider diameter than the efferent arteriole which means the blood pressure in the glomerulus (knot of capilleries in the nephron) increaser - so all the small molecule sin the blood (amino acids, urea, co2, h2o, o2 etc) gets forced out of the blood capillaries BUT blood cells and large plasma proteins are too large to be forced out.

The filtrate (plasma without plasma proteins) is forced out into the bowman's capsule. 

There is only a basement membrane is the only true separation between endothelial cells of the glomerulus ad the bowman's capsule

The kidney 

•Blood enters a kidney through the renal artery and leaves through the renal vein.

•Excretory products are removed from the blood and are collected in the form of urine.

•Urine collects in the central part of the kidney called the pelvis.

•Urine passes from each kidney to the bladder along a tube called the ureter.

•The outer darker region of the kidney is the cortex and the inner, lighter region is called the medulla.