The schematic drawing below shows the cross section of a crypt in the gut epithelium of a mammal. Indicate whether each of the following descriptions better applies to the areas labeled A, B, or C. Your answer would be a four-letter string composed of letters A to C only, e.g. CCBB.

( ) The stem cells reside in this area.
( ) This area contains the most rapidly dividing cells.
( ) Cells in this area would show the least radioactivity following a pulse of tritiated thymidine.
( ) This area contains cells of the innate immune system.

Question

The schematic drawing below shows the cross section of a crypt in the gut epithelium of a mammal. Indicate whether each of the following descriptions better applies to the areas labeled A, B, or C. Your answer would be a four-letter string composed of letters A to C only, e.g. CCBB.
  
( ) The stem cells reside in this area.
( ) This area contains the most rapidly dividing cells.
( ) Cells in this area would show the least radioactivity following a pulse of tritiated thymidine.
( ) This area contains cells of the innate immune system.

Quizplus · Accepted Answer

The stem cells are located near the base of the crypt, interspersed between Paneth cells (in area C), and divide at a relatively slow pace compared to the committed precursors (in area B) that divide rapidly. The cells in area A are differentiated and no longer divide.

The Schematic Drawing Below Shows the Cross Section of a Crypt