Biology · Structural Organisation in Animals · NEET
Smooth (visceral) muscle is made of spindle-shaped (fusiform) cells, each with a single central nucleus, no striations, and it works involuntarily. It is found in the walls of hollow internal organs like the stomach, intestine, blood vessels and urinary bladder. Memory hook: "Smooth = Spindle, Single nucleus, Smooth (no bands), Silent (involuntary)."
At a glance
Cell shape
Spindle-shaped (fusiform)
Long and cylindrical
Nuclei
Single, central (uninucleate)
Many (multinucleate)
Striations
Absent (non-striated)
Present (striated)
Control
Involuntary
Voluntary
Intercalated discs
Absent
Absent
Location
Gut, blood vessels, bladder
Attached to bones
Smooth (visceral) muscle: spindle-shaped, unbranched cells each with one central nucleus, no striations, working involuntarily in the walls of the gut, blood vessels and bladder.
Your doubts, answered
Why is smooth muscle also called visceral muscle?
Because it lines the walls of the internal hollow organs, called viscera. Examples are the stomach, intestine, blood vessels and urinary bladder. Since it sits in these visceral organs, NCERT names it visceral (smooth) muscle.
Does smooth muscle have striations?
No. Smooth muscle has no striations, so it looks plain or uniform under the microscope. That is exactly why it is called smooth (or non-striated / unstriped) muscle. Only skeletal and cardiac muscle show light and dark bands.
Is smooth muscle voluntary or involuntary?
It is involuntary. You cannot control it by your will. It works on its own, controlled by the autonomic nervous system, for example when the intestine pushes food forward (peristalsis).
How many nuclei does one smooth muscle cell have?
One. Each smooth muscle cell (a spindle-shaped fibre) has a single, central nucleus. This is a common NEET point: smooth = uninucleate, skeletal = multinucleate.
What is the shape of a smooth muscle cell?
It is spindle-shaped, also called fusiform. This means it is wide in the middle and tapers (becomes pointed) at both ends. Skeletal muscle fibres are long and cylindrical instead.
Do smooth muscles have intercalated discs?
No. Intercalated discs are found only in cardiac (heart) muscle. This exact swap was tested in NEET 2021, where saying smooth muscle has intercalated discs was the wrong statement.
⚠️ The NEET trap ✗ Smooth muscle cells are joined by intercalated discs and are multinucleate. ✓ Smooth muscle cells are spindle-shaped, uninucleate and have NO intercalated discs. Intercalated discs belong only to cardiac muscle. 🧠 NTA loves swapping features between the three muscle types. Fix each label: intercalated discs = cardiac only; multinucleate = skeletal only; smooth = single central nucleus, spindle-shaped, no discs, no striations.
Real NEET questions
2016
Smooth muscles are
A · Involuntary, fusiform, non-striated ✓
B · Voluntary, multinucleate, cylindrical
C · Involuntary, cylindrical, striated
D · Voluntary, spindle-shaped, uninucleate
Solution: Smooth (visceral) muscle cells are spindle-shaped (fusiform), have a single central nucleus, lack striations and are involuntary. Options B and C describe skeletal muscle features, and option D wrongly calls them voluntary.
2016
Which type of tissue correctly matches with its location?
A · Tissue: Smooth muscle, Location: Wall of intestine ✓
B · Tissue: Areolar tissue, Location: Tendons
C · Tissue: Transitional epithelium, Location: Tip of nose
D · Tissue: Cuboidal epithelium, Location: Lining of stomach
Solution: The wall of the intestine (a visceral organ) is lined by smooth muscle, so option A is correct. Tendons are dense regular connective tissue, the nose tip has cartilage, and the stomach lining is columnar epithelium.
2021
Which of the following statements wrongly represents the nature of smooth muscle? (a) Communication among the cells is performed by intercalated discs (b) These muscles are present in the wall of blood vessels (c) These muscle have no striations (d) They are involuntary muscles
A · Communication among the cells is performed by intercalated discs ✓
B · These muscles are present in the wall of blood vessels
C · These muscle have no striations
D · They are involuntary muscles
Solution: Statement (a) is the wrong one, so it is the answer. Intercalated discs are found in cardiac muscle, not smooth muscle. The other three statements are all true features of smooth muscle.
Solved Structural Organisation in Animals NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Spindle-shaped (fusiform) cells, a single central nucleus (uninucleate), no striations (non-striated), and involuntary control. This is the standard NCERT set NEET tests most often.
Where is smooth muscle located?
In the walls of hollow internal (visceral) organs: the alimentary canal (stomach, intestine), blood vessels, urinary bladder, ureters, bronchi and reproductive tracts.
Why is smooth muscle important for the body?
It moves substances through internal organs without conscious effort, for example peristalsis in the gut and changing the diameter of blood vessels. This keeps digestion and blood flow running automatically.
How is smooth muscle different from skeletal muscle?
Smooth muscle is spindle-shaped, uninucleate, non-striated and involuntary. Skeletal muscle is long, cylindrical, multinucleate, striated and voluntary.
Is smooth muscle branched?
No. Smooth muscle cells are unbranched, spindle-shaped fibres. Only cardiac muscle fibres are branched and joined by intercalated discs.
