The Nephron and Urine Formation!

Hey guys, sorry this wasn't up earlier! It was one of those situations where I don't look at my agenda until late Sunday night and then realize I forgot to write on the blog. SO, here it goes.

We learned a lot about the nephron this class. The nephron is the funcional unit of the kidney. As was said by Camille (I think it was Camille), nephrons are to the kidney as lobules are to the liver. There are approximately 1 million nephrons in the kidney and each are composed of a system of tubules. Each has its own blood supply. From the renal artery, the afferent arteriole leads into the glomerulus and then blood leaves the glomerulus by way of the efferent arteriole. The efferent arteriole then takes the blood to the peritubular capillaries which surround the rest of the nephron. The blood then goes to the renal vein.

Here is a diagram showing the path of the blood.

Next are the different parts of the nephron. First up is the GLOMERULAR CAPSULE, also known as Bowman's Capsule. Then we have the PROXIMAL CONVOLUTED TUBULE, which is difficult to remember so it can be shortened to PCT. Thirdly is the LOOP OF HENLE, which is a U-shaped tube composed of simple squamous epithelium. Next up is the DISTAL CONVOLUTED TUBULE, which again, may be difficult to remember. So we can shorten it to DCT. Last but not least are the COLLECTING DUCTS. They empty out into the renal pelvis.

Here is another lovely diagram, but this one shows all the different parts of the nephron that I just mentioned.

Now here is the big question that I know you are all secretly asking yourselves...

HOW IS PEE MADE? or in more formal terminoligy: URINE FORMATION.

You see, there are 3 steps to urine formation: GLOMERULAR FILTRATION, TUBULAR REABSORPTION, and TUBULAR SECRETION. Now I'm not going to go into great detail about these 3 steps because you can easily go read your powerpoint notes or textbook. Instead I'll show you a video:

*make note: she says capillary really weird (in my opinion)

AND, sorry guys! I couldn't figure out how to embed the video onto the blog.

http://www.youtube.com/watch?v=glu0dzK4dbU

Lastly, why is our pee yellow? Well, I actually coincidentally found out the answer to this question ON this blogger website. It said,

"The yellow color in urine is due to chemicals called urobilins. These are the breakdown products of the bile pigment bilirubin. Bilirubin is itself a breakdown product of the heme part of hemoglobin from worn-out red blood cells. Most bilirubin is partly broken down in the liver, stored in the gall bladder, broken down some more in the intestines, and excreted in the feces (its metabolites are what make feces brown), but some remains in the bloodstream to be extracted by the kidneys where, converted to urobilins, it gives urine that familiar yellow tint."

(http://sxxz.blogspot.com/2006/07/why-is-urine-yellow.html)