Transitional Epithelium

Transitional epithelium (uroepithelium) is specialized to change in response to increased tension. It forms the inner lining of the urinary bladder and lines the ureters and part of the urethra. When the wall of one of these organs contracts, the tissue consists of several layers of cuboidal cells; however, when the organ is distended, the tissue stretches, and the physical relationships among the cells change. While distended, the tissue appears to contain only a few layers of cells (fig. 5.9). In addition to providing an expandable lining, transitional

Transition Unstretched

Lumen

Stratified columnar epithelium

Nucleus

Basement membrane

Underlying connective tissue

Nucleus Wall Blood Vessle

Figure 5.8

Stratified columnar epithelium consists of a superficial layer of columnar cells overlying several layers of cuboidal cells (250x micrograph enlarged to 1,000x).

Basement membrane

Underlying connective tissue

Unstretched transitional epithelium

Basement membrane

Underlying connective tissue

Unstretched transitional epithelium

Unstretched Transitional Epithelium
(a)

Stretched transitional epithelium

Basement membrane

Underlying connective tissue

Figure 5.9

Transitional epithelium is (a) unstretched and consists of many layers when the organ wall contracts (250x micrograph enlarged to 600x). (b) The tissue stretches and appears thinner when the organ is distended (250x micrograph enlarged to 600x).

Epithelium Glandulaire

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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