Lab 2 Epithelial Tissue: Index - 1)Introduction - 2)Simple Squamous - 3)Simple Cuboidal - 4)Simple Columnar - 5)PsuedoStratified - 6)Transitional - 7)Stratified Squamous - 8)Stratified Columnar - 9)Stratified Cuboidal - 10) Trachea and Esophogus Comparison - 12) Practical

 

TRANSITIONAL EPITHELIUM

Distribution is limited to the urinary tract.

 

1. Urinary bladder

# 14 - Urinary bladder, transitional epithelium, h&e

 

Examine this slide first by eye and then by 4x. Find the epithelium-lined lumen of the bladder. Transitional epithelium is usually not more than 3-8 layers deep. It is characterized by "dome-shaped cells" and "pear-shaped cells" when under little or no tension. When stretched, these dome-shaped cells become much flatter and appear quite similar to the uppermost cells of stratified squamous epithelium. You may be able to observe regions that contain both the domed and stretched forms of this tissue. Contrast the cytomorphosis (change in shape and appearance of cells from the base of the epithelium to its surface) in this type of epithelium with that occurring in typical stratified squamous epithelium (in the following section).

References: Gartner, p. 35, Fig. 4 Ross, p. 595, Fig. 3 p. 333, Fig. 4 p. 89, Fig. 4 Wheater, p.81, Fig. 5.9 DiFiore, p. 15, Fig. 1-7

 

The white line is defining the length of the epithelium. Notice how the cells look different at the top than the bottom. The arrangement makes sense functionally because by the top most layer being plump (orange arrow), allows them to be compressed when the bladder is full.

HINT: If the top cells are plump, the bladder or lumen is empty. If they are flat, it is full.

White line- defines height of epithelium

Orange Arrow - "plump" cell

Bladder (empty)

 

2. Kidney pelvis and ureter

# 142- Kidney, adrenal, human fetus

 

In the hilum of the kidney, locate the beginning of the ureter and observe the epithelium. Refer to p. 593 of Ross. The ureter is the round hollow structure with the star-shaped lumen located in the adipose tissue in the hilum of the kidney.

References: Gartner, p. 333, Fig. 2 Ross, p. 593, Fig. 3 Wheater, p. 302, Fig. 16.22 (overview) DiFiore, p. 255, Fig. 16.6 - 16.7 p. 303, Fig. 16.25 (epithelium)

 

Now this is the same type of epithelium, but look how different it looks now. You almost want to call this stratified squamous. But because of the fact that this bladder or lumen is full the plump cells are now flattened (orange arrow). This flattening allows for distention of the bladder to hold your urine so you don't have to go to the bathroom every five minutes.

White line - Height of epithelium

Orange arrow - Flattened "plump" cells

Bladder (full)