Chapter 10 Muscular Tissue Lecture slides prepared by Curtis DeFriez, Weber State University

Functions of Muscular Tissue 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

Three Types of Muscular Tissue Location Function Appearance Control Skeletal skeleton movement, heat, posture striated, multi-nucleated (eccentric), fibers parallel voluntary Cardiac heart pump blood continuously striated, one central nucleus involuntary Visceral (smooth muscle) G.I. tract, uterus, eye, blood vessels Peristalsis, blood pressure, pupil size, erects hairs no striations, one central nucleus

Three Types of Muscular Tissue (a) Skeletal muscle (b) Cardiac muscle (c) Visceral smooth muscle

Skeletal Muscle Location Function Appearance Control Skeletal skeleton movement, heat, posture striated, multi-nucleated (eccentric), fibers parallel voluntary Cardiac heart pump blood continuously striated, one central nucleus involuntary Visceral (smooth muscle) G.I. tract, uterus, eye, blood vessels Peristalsis, blood pressure, pupil size, erects hairs no striations, one central nucleus

Skeletal Muscle All muscle start as these spindly shaped cells from myoblasts – skeletal muscle cells fuse to form large fibers… Satellite cells are small mononuclear progenitor cells with virtually no cytoplasm found in mature muscle. They are found sandwiched between the basement membrane and sarcolemma (cell membrane) of individual muscle fibres, and can be difficult to distinguish from the sub-sarcolemmal nuclei of the fibres. Satellite cells are able to differentiate and fuse to augment existing muscle fibres and to form new fibres. These cells represent the oldest known adult stem cell niche, and are involved in the normal growth of muscle, as well as regeneration following injury or disease.

A single skeletal muscle fiber 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 It’s difficult to find the sartorius muscle in some people (cadavers) A single skeletal muscle fiber

Skeletal Muscle The terminal processes of a motor neuron in close proximity to the sarcolemma of a skeletal muscle fiber Motor neuron Sarcolemma

Organization of Muscle Tissue 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 Epimysium Perimysium These next few graphics show connective tissue elements associated with skeletal muscle: Starting with whole muscles and working our way down to fascicles and individual muscle cells (fibers). Organization of a single muscle belly

Organization of Muscle Tissue 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 Many large muscle groups are encased in both a superficial and a deep fascia Real Anatomy, John Wiley and Sons