Slide 26. Smooth muscle tissue of the small intestine, H&E
Explains how to identify smooth muscle of the small intestine in an H&E section, covering the two muscularis externa layers cut at right angles. It describes the pink cytoplasm and blue-purple nuclei, the lengthwise spindle cells with central cigar-shaped nuclei, and the round cross-sections of the other layer, some showing a nucleus. It also notes the absence of striations, the myenteric plexus ganglion cells between the layers, and how to tell it from dense regular connective tissue.
Inside: 1 section · 1 min
Topic 115 of 127 in the MU Sofia syllabus for Cytology (Dental Medicine, Year 1). The free AceMed note covers it in 1 section, about 118 words (1 min of reading).
In this note
Introduction
Introduction
The muscularis externa of the small intestine has two layers of smooth muscle: an inner circular layer and an outer longitudinal one. A section therefore cuts the two layers at right angles.
Stain
H&E: cytoplasm pink and even, nuclei blue-purple.
How to recognise it
In one layer, spindle-shaped cells cut lengthwise, each with one central, cigar-shaped nucleus.
In the other layer, round profiles of different sizes, only some of them showing a nucleus (those cut through the middle).
No striations.
Between the two layers, groups of ganglion cells of the myenteric (Auerbach's) plexus.
Don't confuse it with: dense regular connective tissue, whose nuclei are squeezed between collagen bundles rather than lying inside cells.
Theory: topic 59 (smooth muscle).
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