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HUMAN PHYSIOLOGY 



Suprarenal 



body 



Cortex 



Medulla 



z--^=i^Pvra m ids 



closely wrapped in a thin coat of connective tissue ; this is called the capsule. 



Remove the kidney from this capsule. Notice its color and shape. The 



depression called the hilum is deeper than 

 the corresponding region in the kidney 

 bean. The hollow tube passing out from 

 this region is called the ureter. Blood 

 vessels also enter and leave the kidney 

 at the hilum. Cut the kidney lengthwise 

 into halves. Try to find the following 

 regions : (1) The outer or cortical region; 

 note its color; (2) The inner or medul- 

 lary layer; this layer is provided with 

 little projections ; these are the pyramids 

 of Malpighi, so called after their dis- 

 coverer, Marcello Malpighi, a celebrated 

 Italian physiologist; (3) the cavity or 

 pelvis of the kidney. At the summit of 

 each pyramid is a small opening through 

 which escapes into the pelvis the secretion 

 formed in the little tubules which make 

 up the substance of the kidney. Draw a 

 sheep's kidney, cut lengthwise, showing 

 all the above points. 



-Ureter 



Longitudinal section of kidney. 



a 



The Human Kidney. — The description given above will apply 

 almost exactly to the kidney of man except for the size. The 

 human kidney is about four inches long, two and one half inches 

 wide, and one inch in thickness. Its 

 color is dark red. If you examine the 

 structure of the medulla and cortex (see 

 above) under the compound microscope, 

 you will find these regions to be com- 

 posed of a vast number of tiny branched 

 and twisted tubules. The outer end of 

 these tubules open into the pelvis; the 

 inner end, in the cortex, forms a tiny 

 closed sac. In each sac, the outer wall 

 of the tube has grown inward and car- 

 ried with it a very tiny artery. This 

 artery breaks up into a mass of capil- 

 laries. These capillaries, in turn, unite 

 to 'form a small vein as they leave 

 the little sac. Each of these sacs with 

 its contained blood vessels is called a 

 glomerulus. 



Diagram of kidney circulation, 

 showing a glomerulus and 

 tubule ; a, artery bringing 

 blood to part ; b, capillary 

 bringing blood to glomerulus; 

 b', vessel continuing with 

 blood to tubule; c, vein; t, 

 tubule ; G, glomerulus. 



