SMOOTH MUSCLE
Smooth muscle is found in the walls of blood vessels and in viscera such as the gut, bladder, glands and uterus. Smooth muscle is not striped or ❌ when examined under a microscope. It has a spontaneous rhythm and contraction, although it can be controlled by ❌ which slow down or speed up the rate of contraction. Smooth muscle contracts and fatigues slowly.
The muscle cells or fibres are ❌ and ❌ with a central nucleus and are much ❌ than the skeletal muscle fibres. The muscle fibres are usually arranged in sheets or layers. In many tubular visceral structures, e.g. ❌, the smooth muscle is arranged in layers. The cells are on layer lie at ❌ to the cells of the adjacent layer. This allows a wave of contraction (❌) to pass down the tube propelling the contents forwards.
In some place, e.g. ❌, smooth muscle fibres occur singly or in small groups. In the ❌, at the exit of the stomach into the small intestine, the muscle fibres are arranged in a ❌.
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spindle-shaped
spindle-shaped
right angles
right angles
pyloric sphincter
pyloric sphincter