DIFFERENCES BETWEEN SINGLE-UNIT AND MULTI-UNIT SMOOTH MUSCLES
Single-unit Smooth Muscles
Multi-unit Smooth Muscles
They are composed of muscle fibres closely
They are composed of muscle fibres not so
closely joined together.
All the fibres of single smooth muscle
All the fibres of a multiunit muscle contract
contract together as a single unit.
as separate units.
Muscles of the wall of hollow visceral organs
Muscles of the wall of large blood vessels,
(e.g., Gastrointestinal tract and urinary
arrector pili muscles of skin dermis, ciliar and
bladder) are examples of this type of muscles.
iris muscles in the eyes are examples of this
type of muscles.