Graduate Microanatomy, 1998
Graduate Microanatomy, 1998
|
Lab Exercises: Collecting ducts, calyces, Ureter and Bladder
Date page was last edited 06/09/04 |
Lab Exercises: Calyces, Ureter & Bladder Calyces: The collecting ducts become taller as they descend in the medulla. Eventually they become the columnar DUCTS OF BELLINI. The epithelium then joins with that of cup like extensions of the ureter called the MINOR CALYCES (singular=calyx). The minor calyces are branches of the MAJOR CALYCES. The epithelium of the minor and major calyces is transitional, beginning with 2-3 layers and ending with 8 or more layers. You may find parts of the calyces on your kidney slides, especially the Masson stained slide.
The above photograph shows the transition between the Duct of Bellini and the minor calyx. Note the increase in number of layers in the epithelium. Urine is emptied into the calyces which are like funnels that send it to each of the ureters. Note the extensive connective tissue that underlies the epithelium in this region (stained blue). The following photo shows a higher magnification of the transitional region. Some areas still have only a simple columnar epithelium, others have the mixture of types of epithelia typical of transitional epithelium.
The major calyx may be distinguished by its number of layers of cells. The following photograph shows the wall of a major calyx. Again, the epithelium is transitional, like that of the ureter.
URETER: After they begin in the calyces, the two muscular tubes, the URETERS, conduct the urine to the bladder. The following photograph shows the transitional epithelium in the ureter. Find it in your ureter slide. Recall that it is distinguished by rounded cells at the surface. It is a mixture of columnar and cuboidal epithelia which is how it got its name.
Underneath the epithelium is a layer of connective tissue. Then, there are three layers of smooth muscle. The innermost is longitudinal (cut in cross section in your sections), the middle is circularly arranged around the tube (cut in longitudinal section) and the outer is longitudinal again. Look at the muscle in your ureter slide and find a region that shows the three layers distinctly. The following photo illustrates such a region.
The above photograph shows the inner, middle, and outer smooth muscle layers of the ureter. Outside the muscle wall is the ADVENTITIA which is loose connective tissue.
1. Draw the ureter and show how it ends in the major and minor calyces in the kidney.
BLADDER The urinary bladder is relatively simple in that it has a transitional epithelium, an underlying connective tissue (LAMINA PROPRIA) and an interwoven smooth muscle wall which shows no distinct layers (MUSCULARIS). Outside the muscular wall is the connective tissue ADVENTITIA. Find these regions in your bladder slide. These photos show the bladder epithelium. Note the rounded bulging cells facing the lumen. Also, note the underlying lamina propria in the above photo.
2. What structures enable the transitional epithelium to distend? Draw an electron microscopic view of the epithelial cells.
Note the interlacing muscle bundles in the wall of the bladder, separated by connective tissue as shown in the above photo. There are no organized layers of smooth muscle in the wall.
Return to top of page | Course Design | Learning Aids | Learning modalities | |
