114
UNIT 2
Basic Tissues
Features
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
Striations
Yes
Yes
No
Fibers
Long, cylindrical, unbranched
Short, branched, anastomosing
Short, spindle shaped
Nuclei
Multiple, peripheral in cell
Single, central in cell
Single, central in cell
Cell junctions
No
Intercalated disks
Gap (nexus) junctions
T tubules
Well developed
Well developed
No
Sarcoplasmic
reticulum
Highly developed; has terminal
cisterns
Less well developed; small cisterns
Present, but poorly developed
Regeneration
Yes, satellite cells
No
Yes, mitosis
Contraction
Initiated by nerve action potential
Spontaneous; pacemaker system;
modulated by nervous system and
hormones
Spontaneous; modulated by
nervous system and hormones
Main function
Voluntary movement of limbs, digits,
face, tongue, and other muscles
Involuntary rhythmic
contractions;
pumps blood to muscles and
organs; modulated by physiological
and emotional factors
Involuntary control of blood
vessel diameter, gut peristalsis,
uterine contractions during
childbirth, airway diameter, and
others
TABLE 6-1
Muscle Characteristics
SYNOPSIS 6-1
Pathological and Histological Terms for Muscle
Anastomose
: To join end to end, as in suturing two blood vessels together (Fig. 6-8A).
Autoimmune disease
: A condition in which an individual’s immune system mistakes the individual’s own tissue for a for-
eign invader and attacks the tissue, as in myasthenia gravis or multiple sclerosis (Fig. 6-6C).
Caveolae
: Small, cup-shaped indentations in the sarcolemma of smooth muscle cells; may be involved in the uptake of
calcium during contraction (Figs. 6-12 and 6-13).
Dystrophin
: A large, rod-shaped protein that plays a critical role in connecting the molecular contractile mechanism of
skeletal muscle to the surrounding extracellular matrix so that the force of the actin-myosin contraction can be transferred
to other structures to do useful work. The lack of dystrophin is a key feature of some types of muscular dystrophies
(Fig. 6-3C).
Fibrosis
: Abnormal formation of connective tissue, including ±
broblasts and connective tissue ±
bers, to replace normal
tissues in response to tissue damage caused by disease or injury (Fig. 6-3C).
Hyperplasia
: Abnormal proliferation of cells, which may or may not lead to the increase in the size of the affected structure
or organ; may be a precancerous condition (Fig. 6-6C).
Hypertrophy
: An increase in the size of a structure produced by an increase in the size of the cells that make up the
structure.
Intrafusal
: Structures, particularly muscle ±
bers, that are found inside the muscle spindle. The word is derived from the
Latin “
fusus
” which means “spindle” (Fig. 6-7A).
Necrosis
: Pathologic death of cells or tissues as a result of irreversible damage because of disease or injury (Fig. 6-3C).
Synaptic cleft
: The small space between a presynaptic axon terminal and the postsynaptic membrane of a muscle cell or a
neuron upon which the axon forms a synapse (Figs. 6-6B,C).
Varicosity
: A local swelling in a tubelike structure such as an axon (Fig. 6-10A).
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