Anatomy and Physiology II

Kidney Dissection Lab Instructions

You are required to compile your pictures into a presentation. You will attach this presentation in the designated ‘Assignments’ folder (located under the ‘Assessments’ tab in the nav bar on the course home page). Most students use ‘Power Point’ or insert the pictures into a Word document. I appreciate added comments in your presentation that explain/describe things you found or didn’t find.

Please make sure your labels are clear and small enough I can see the structure you are identifying. The pictures seem to be clearer when you place light colored paper behind the specimen. You must use a digital camera. (The camera on your phone is ‘digital’. That will enable you make sure they are clear. You will create a presentation, using the ‘best shot’ of each set of pinned structures. If you can’t clearly see the label for a structure in a photo you’ve already taken, you can label it again by using the ‘editing’ tools in a graphics program on your computer. I have suggested picture groupings below, but please feel free to divide the structures up as necessary to get me the best view of your dissection.

Make a label with your name to put in each picture. The structures you need to identify are in the list below. The detailed instructions for completing the dissection follow this list.

Structures:

renal fat
capsule
hilus

-take a photo

renal artery
renal vein
ureter

-take a photo

cortex
medulla
columns
pyramids

-take a photo

papilla
renal sinus

-take a photo

minor calyx
major calyx
renal pelvis

-take a photo

The kidneys are composed of nephrons, connective tissue, & vessels. The nephrons, numbering about 400,000 in each sheep kidney, are too small to see on your dissection specimen. However, you will be able to see and label the larger connective tissue structures. Because the kidney’s job is to filter the blood, producing tubular filtrate and urine, some of the “structures” will be open spaces (such as renal sinuses). The renal artery, renal vein and ureter are located at the hilus.

1. Locate the renal capsule and identify the renal fat. The renal capsule is ‘shrink wrapped’ to the kidney, not really ‘loose’ like in this picture. You might need to ‘tease’ it off or cut into the kidney specimen and then look for it (you can easily pull it away from the underlying tissue if it’s cut into). It is possible you received a kidney with the capsule already removed. If you make a shallow incision into the outside layer of the kidney, you will see one of two things: all the tissue is the same, or a separate thin, tough outer layer that you can pull away from the underlying tissue. Try it and see. If you have a capsule (the part that pulls away), label it. If you don’t, label where it should have been and make a note in your submission that yours was missing, but that’s where it would have been.

The kidney is covered in fat. Your specimen might not have lots of fat, but you should be able to find some near the hilus (white or yellow stuff). The kidneys are retroperitoneal, lying behind the peritoneum. This fatty layer acts like a shock absorbing layer for the kidneys.

Each kidney is covered with fibrous capsule. You found it first in this dissection. A protective outer capsule is seen around all the organs of the body. You should also be able to locate the remnants of a denser connective tissue, the renal fascia, around the area where the structures enter the kidney at the hilus. The renal fascia fuses with the deep fascia of the transversus abdominis and the peritoneum overlying the kidney. This anchors the kidney in place.

The vessels, as well as the ureter, enter and exit each kidney at the hilus. Three structures are found at the hilus of the kidney. These structures are the renal artery, renal vein and ureter. Each kidney is supplied with blood by a renal artery, a direct branch off of the abdominal aorta. The renal vein empties into the inferior vena cava. The ureter is the tube through which urine exits the kidney and enters the bladder.

The renal artery will be the smaller, rounder, firmer vessel. The vein, because it doesn’t have so much smooth muscle in its walls, will be collapsed/floppier when there is no blood inside of it. Normally the ureter is lighter in color and longer.

If the vessels are encased together by a connective tissue wrapping, separate them (it may be all three, or it may just be the artery and vein). If you cannot find three structures, you may need to dissect into the hilus for a short distance. If one or more of these structures is missing from your kidney, “make” a pretend one from paper and label it.

The structure covered in the most fat is the ureter (2). It is also most likely the longest structure.
The renal vein is wider and thinner than the renal artery (3). That observation should not surprise you. The renal artery is thicker, but more narrow than the vein or ureter (1).

Now make a frontal (coronal) section through the kidney. Don’t cut towards your hand as it seems to indicate in this photo. Place your non-cutting hand over the top of the knife and grip the kidney on either side as you cut down towards the table/tray until you have cut all the way through.

The outer portion of the kidney is the renal cortex, which has extensions inward called renal columns. These will be the very thin strips of tissue in between the pyramids. The middle portion (between the cortex and the hilus) is the renal medulla, which is made up of many renal pyramids.

The region of the kidney just below the capsule is the renal cortex. It is usually a lighter color than the deeper region. Extensions of this tissue, the renal columns, dip toward the hilus. This tissue is less dense that the deeper medullary tissue, allowing the vessels of the renal blood system to reach all of the nephrons.

The renal medulla of each kidney contains 6-18 triangle shaped structures called renal pyramids. This tissue is darker and appears striated. This is because all the tubular systems of the nephrons within that pyramid are oriented in the same direction. This forms parallel tubes, giving the tissue the striated appearance. All of the tubular systems, with their collecting ducts, converge at the apex of the pyramid. This structure is called the renal papilla. The filtrate has now left the nephron. It can have no more changes in volume or composition. The fluid is now urine.

The open spaces surrounding the renal structures are called renal sinuses. In addition to the renal structures, sinuses also contain blood and other vessels, nerves, and fat. Where you can find small spaces/gaps between the other tissues in the medulla, those are the sinuses.

The urine continues its journey through a series of tubes that become larger as more structures converge. Each renal papillae is surrounded by a minor calyx. The papillae are at the narrow, pointed tips of the pyramids where they meet up with the minor calyx leading into the renal pelvis. Seven to fourteen minor calyces (the plural form of calyx) converge to become a major calyx. Each kidney usually has two major calyces that converge into a larger opening, the renal pelvis. The renal pelvis is where all these tubes converge. It’s a single chamber formed just inside the hilus that is continuous with the ureter as it leaves the hilus. The ureter is draining this fluid (the urine) from the renal pelvis to the urinary bladder.

Using your fingers, complete a “rough” dissection of the tubular system. THAT MEANS DIG OUT THE TISSUE. THE SOFT STUFF WILL COME OUT AND YOU WILL BE LEFT WITH BEAUTIFUL ARCHITECTURE! Basically, you are pulling out the pyramids and looking at what is underneath. You should find lots of vessels, nerves, and structures of the large tubules that convey filtrate, which becomes urine to the ureter. Label a major calyx, a minor calyx and the renal pelvis on this rough dissection where you can actually see these structures clearly (they were previously hidden by all that other tissue).