Pl. VII · Transitorius distensibilis — transitional

The plate

The specimen, drawn

Pl. VII

The tissue as you will meet it on the slide.

Habitat & range

Where it lives

Body map

Where this tissue is found.

Range

• Renal calyces and pelvis
• Ureters
• Bladder
• Upper urethraThe tube that carries urine from the bladder to the outside of the body. — and nowhere else

Collection record

• Add your slide numbers here.

Niche

What it does for a living

Changing shape without changing number. It accommodates volume and keeps urineThe liquid waste excreted by the kidneys. out of the tissue underneath while doing it — the tightest barrier in the body.

field collected specimen

How to know it on sight

• Several layers with a domed, bulging top row when relaxed.
• Umbrella cellsThe basic structural and functional units of life., often binucleate.
• Stretched, the whole thing flattens and looks like fewer layers.
• Judge it by location as much as by shape.

Specimen 1

Specimen 2

Specimen 3

People keep calling her by the wrong name

Look-alikes

Three plates. Read the line underneath each one before you decide.

Stratified squamous

Tell them apart by the top cells — flat, never domed — and by the organ.

Stratified cuboidal

Tell them apart by depth: only two layers.

An over-stretched specimen of itself

Tell them apart by remembering it is the same tissue. Flattened urothelium is not squamous.

Examine it yourself

The virtual slide

Zoom in until you can see the surface of the cells, then find the basement membrane underneath.

Virtual slide courtesy of Histology Guide.

Field notes

Why this animal

A pufferfish is the same fish empty or full; it does not grow, it fills, and the skinThe body’s largest organ, providing protection and regulation. takes up the slack.