a

Chapter 10

Muscular

Tissue

Lecture slides prepared by Curtis DeFriez, Weber State University

• Like nervous tissue, muscles are excitable or "irritable”

they have the ability to respond to a stimulus• Unlike nerves, however, muscles are also:

Contractible (they can shorten

in length)

Extensible (they can extend or

stretch)

Elastic (they can return to their

original shape)

Functions of Muscular Tissue

• Muscle makes up a large percentage of the body’s

weight

• Their main functions are to:

Create motion – muscles work with nerves, bones, and

joints to produce body movements

Stabilize body positions and maintain posture

Store substances within the body using sphincters

Move substances by peristaltic contractions

Generate heat through thermogenesis

Functions of Muscular Tissue

Three Types of Muscular Tissue

(b) Cardiac muscle (c) Visceral smooth muscle

(a) Skeletal muscle

Three Types of Muscular Tissue

Skeletal Muscle

Skeletal Muscle

Skeletal muscle fibers are very long “cells” -

next to neurons (which can be over a meter

long),

perhaps the longest in the body

The Sartorious muscle contains

single fibers that are at least

30 cm long

A single skeletal muscle fiber

Skeletal Muscle

Sarcolemma

Motor neuron

Skeletal Muscle

The terminal processes of a

motor neuron in close proximity

to the sarcolemma of a skeletal

muscle fiber

The epimysium, perimysium, and

endomysium all are continuous with

the connective tissues that form

tendons and ligaments (attach

skeletal muscle to bone) and muscle

fascia (connect muscles to other

muscles to form groups of muscles)

Organization of Muscle Tissue

Organization of Muscle Tissue

Organization of a single muscle

belly

Epimysium

Perimysium

Organization of a fasciculus

Organization of Muscle Tissue

Organization of a muscle fiber

Organization of Muscle Tissue

A muscle, a fasciculus, and a fiber all visualized

Organization of Muscle Tissue

• In groups of muscles the

epimysium continues to

become thicker, forming

fascia which covers many

muscles• This graphic shows the

fascia lata enveloping the

entire group of quadriceps

and hamstring muscles in

the thing

Organization of Muscle Tissue

Organization of Muscle

Tissue• Many large muscle

groups are encased

in both a superficial

and a deep fascia

Real Anatomy, John Wiley and Sons

Organization of Muscle Tissue• An aponeurosis is

essentially a thick fascia that connects two muscle bellies. This epicranial aponeurosis connects the muscle bellies of the occipitalis and the frontalis to form “one” muscle: The occipitofrontalis

Epicranial aponeurosisFrontal belly of

the occipitofrontalis m.

Veins, arteries, and nerves are located in the

deep fascia between muscles of the thigh.

Organization of Muscle Tissue

Beneath the connective tissue endomysium

is found the plasma membrane (called the

sarcolemma) of an individual skeletal

muscle fiber

The cytoplasm (sarcoplasm) of skeletal

muscle fibers is chocked full of

contractile proteins

arranged in myofibrils

The Skeletal Muscle Fiber

You should learn the names of the internal

structures of the muscle fiber

Sarcolemma

Sarcoplasm

Myofibril

T-tubules

Triad (with

terminal cisterns

Sarcoplasmic reticulum

Sarcomere

The Skeletal Muscle Fiber

The Skeletal Muscle Fiber

Increasing the level of magnification, the

myofibrils are seen to be composed

of filaments

Thick filaments

Thing filaments

A scanning electron micrograph of a

sarcomere

• The basic functional unit of skeletal muscle fibers is the sarcomere: An arrangement of thick and thin filaments sandwiched between two Z discs

The Skeletal Muscle Fiber

The “Z line” is really a Z disc when considered in

3 dimensions. A sarcomere extends from Z disc

to Z disc.

• Muscle contraction occurs in the sarcomeres

The Skeletal Muscle Fiber

• Myofibrils are built from three groups of proteins

Contractile proteins generate force during contraction

Regulatory proteins help switch the contraction process

on and off

Structural proteins keep the thick and thin filaments in

proper alignment and link the myofibrils to the

sarcolemma and extracellular matrix

Muscle Proteins

• The thin filaments are comprised mostly of the structural

protein actin, and the thick filaments are comprised

mostly of the structural protein myosin

• However, in both types of filaments, there are also other

structural and regulatory proteins

Muscle Proteins