THE KIDNEYS 



173 



/ Much water. 



2. The skin j Little carbonic acid gas. 



( Little urea. 

 . Much water. 



3. The kidneys] Much urea. 



1 Little uric acid. 



The blood which leaves the kidneys by the renal veins is 

 often said to be the purest blood in the body. It has lost much 

 nitrogenous waste matter. Of course a certain proportion of the 

 blood which enters the kidneys goes to nourish the walls of the 

 vessels of which the organs are almost entirely composed. Hence 

 this blood would tend to become venous by its loss of oxygen 

 and its gain of carbonic acid gas. But this is counterbalanced by 

 the excretion of the urine, which contains relatively more carbonic 

 acid gas and less oxygen than the blood from which it was formed. 

 As a result of this, the blood of the renal vein, which has lost so 

 much nitrogenous matter, is still arterial in character. 



SUMMARY. 



About 4 ounces. 



At the back of the abdomen. 



One on each side of the upper lumbar vertebrae. 



The capsule a thin fibrous membrane. 



Renal artery -I A branch of the aorta " 

 3 I Contains arterial blood. 



j Leads to \hevena cava inferior. 

 \ Contains the purified blood. 

 I Leads to the bladder. 

 \ Contains the urine. 

 i Enlargement of the ureter. 

 \ Gives off prolongations called 

 ^ calices. 



( Composed of minute tubes. 

 I Arranged in cones or pyra- 

 mids. 



V Tubes open into \\\z pelvis. 

 Cortical por- j Outer portion of the kidney. 

 tion I Darker in colour. 



Excretion continuous. 



/ 3 Ibs. water. 

 I I oz. urea. 

 Daily . . -| 10 grs. uric acid. 



Various salts. 

 V Dissolved gases. 

 ( Strong oval bag. 

 J Involuntary muscular fibres. 

 i Lined with mucous membrane. 

 I Surrounded by peritoneum. 

 < Ureters convey urine from the kidneys. 

 I Urethra for the discharge of the urine. 

 I To retain the urine, and 

 ' t To discharge it at intervals. 



KIDNEY . 



Weight 

 Position 

 Covering 



Vessels 



BLADDER 



Structure 



Excretion 



Structure 



Vessels 

 Use 



Renal vein. 

 Ureter . 



Pelvis 



Medullary 

 portion 



