This document discusses smooth muscle tissue. It defines smooth muscle as non-striated muscle that lacks sarcomeres and is usually involuntary. There are two types of smooth muscle: single unit (visceral) muscle found in organs, and multiunit muscle like the ciliary muscle. Smooth muscle is composed of spindle-shaped cells with a central nucleus. Contraction is triggered by calcium ions causing actin and myosin filaments to slide past each other. Smooth muscle contraction is controlled by the autonomic nervous system, local tissue factors, hormones, and stretch.

1. Regents Biology 2015/2016
Mohamed M.Elsaied
2016/2017
[Smooth Muscle
tissue]

2.  Muscle Tissue
Mohamed M.Elsaied
2016/2017
Types of Muscular Tissue :-
• Skeletal
• Smooth
• Cardiac

3. Mohamed M.Elsaied
2016/2017

4.  Smooth Muscle
Mohamed M.Elsaied
2016/2017
• Cells are not striated
• Fibers smaller than those in skeletal muscle
• Spindle-shaped; single, central nucleus
• More actin than myosin
• No sarcomeres
- Not arranged as symmetrically
as in skeletal muscle,
thus NO striations.
• Caveolae: indentations in sarcolemma;
- May act like T tubules
• Dense bodies instead of Z disks
- Have noncontractile intermediate
filaments

5.  Smooth Muscle Tissue
Mohamed M.Elsaied
2016/2017
 Lacks the striations of skeletal and cardiac muscle tissue
 Usually involuntary
 divided into 2 types (Multiunit type – Visceral )

6.  Types of smooth muscle
Mohamed M.Elsaied
2016/2017
i. Visceral (Single unit type )
 This fibers usually are arranged in sheets or bundle and the cell
membrane are adherent to one another at multiple points so
force generated in one muscle fiber can be transmitted to the
next.
 Acts as syncytium
 Controlled mainly hormonally and locally
 The cell membrane are joined by many gap junction to allow
ions to flow .
 it is called visceral because it is found in the wall of most
viscera .
 Examples :-
• Wall of blood vessels

7. Mohamed M.Elsaied
2016/2017
ii. Multi unit type
 This type of smooth muscle is composed of separate
fibers .
 Each fiber operates independently of tha other and
often is innervated by a singe nerve ending as skeletal
muscle .
 Don’t obey all or none law .
 fibers are too small to generate AP .
 No spontaneous contraction
 Examples :-
• Ciliary muscle
• Pilo –erector muscle

8. Mohamed M.Elsaied
2016/2017

9.  Ultrastructure of Smooth Muscle:
Mohamed M.Elsaied
2016/2017
•Actin and myosin filaments
•intermediate filaments of desmin (also vimentin in vascular smooth
muscle)
•Membrane associated and cytoplasmic dense bodies containing 
actinin (similar to Z lines)
•Relatively active nucleus (smooth muscle cells make collagen, elastin,
and proteoglycans)

10. Mohamed M.Elsaied
2016/2017
Color Nuclei Homogeneity
Smooth
muscle
Smooth muscle
is more purple
because of
combination of
actin/myosin
and RNA (red +
blue = purple)
Smooth
muscle nuclei
are inside cell
Smooth muscle
is composed
only of muscle

11.  Mechanism of Smooth Muscle Contraction
Mohamed M.Elsaied
2016/2017

12.  Control of smooth muscle contraction
Mohamed M.Elsaied
2016/2017
i. nervous control :- Autonomic supply
ii. local tissue factor :- oxygen lack . CO2 excess
iii. Hormonal control :- nor-epinephrine . ADH
iv. stretch :- lead to spontaneous AP

13. Mechanism of Smooth Muscle Relaxation:
Mohamed M.Elsaied
2016/2017

14.  Muscle Regeneration and Growth
Mohamed M.Elsaied
2016/2017
Smooth Muscle
•Increase in size (hypertrophy)
•Increase in number (regeneration/proliferation)
•Smooth muscle cells are proliferative
(e.g. uterine myometrium and vascular smooth muscle)
•Vascular pericytes can also provide source of smooth muscle

15. Mohamed M.Elsaied
2016/2017
Smooth Muscle found in
 Walls of arteries and veins
 Walls of hollow organs
 Walls of airways to the lungs
 Muscles that attach to hair follicles
 Muscles that adjust pupil diameter
 Muscles that adjust focus of the lens in the eye

16. Mohamed M.Elsaied
2016/2017
Walls of arteries and veins

17. Mohamed M.Elsaied
2016/2017
Small intestine

18. Mohamed M.Elsaied
2016/2017
Stomach

19.  References ….
Mohamed M.Elsaied
2016/2017
 Copyright 2009 John Wiley & Sons, Inc.
 The vascular smooth muscle cell: molecular and biological responses
to the extracellular matrix
 The Oxford Companion to the Body (Smooth muscle tissue )
 Uchide T, Uchide T, Adur J, Yoshioka K, Sasaki T, Temma K, Saida K
(2001) Endothelin- 1 in smooth muscle cells and mast cells of mouse
uterus after parturition. Journal of Molecular Endocrinology 27: 165-
173.
 Bloom W, Fawsett D (1975) A Textbook of Histology., Philadelphia: W.
B. Saunders Company. pp. 185-187