Chapter 8 - Lecture
Skeletal Myology/Muscular Systems
Terms in this set (56)
How much of the body mass is composed of skeletal muscles?
When they contract, what are skeletal muscles involved in?
locomotion, posturing, respiration, prehension, mastication, deglutition, orifice closure (and opening), the abdominal press, vocalization, eye movement, and venous return.
A by-product of muscle contraction rather than a primary function
Two major parts of a skeletal muscle
belly and tendinous attachments
Two forms of tendons
bands of c.t. proper ("regular" tendons) and flat sheets of c.t. proper (apeneuroses)
refers to the attachment at the less moveable end of the muscle belly
the attachment at the more moveable end of the muscle belly
C.t. proper encasements of muscles
epimysium, perimysium, and endomysium
the outer connective tissue proper encasement of a skeletal muscle.
At the ends of a muscle belly, epimysium condenses with the ensheathments formed by perimysium (around muscle fascicles) and endomysium (around individual muscle cells) to form the tendons of the muscle
surrounds fascicles (groups of muscle cells)
surrounds individual muscle cells
binds groups of muscle bellies together
hold tendons into certain loci
partially surround tendons and protect them from frictional degradation
totally surround tendons and protect them from frictional degradation
Sesamoid bones acts as
bearing surfaces for the tendon of a few muscles
What happens to myocytes when contractile proteins interdigitate?
myocytes (myofibers) shorten
cytoplasmic organelles of contraction. Contain the contractile proteins (thin and thick myofilaments)
(stacked) in the myofibrils in a very organized fashion in skeletal and cardiac muscle cells which produce histological cross striping termed striation (bands)
A bands production
produced by the stacks of thick myofilaments (myosin)
the lighter of the microscopically observable, alternating dark and light striations across a myofibrils.
I bands occur between the A bands in those loci where the contral parts of thin myofilaments are not overlapped by thick myofilaments
Histological landmarks of Myomere
Z line, H band, M line, A band, I band
functional subunit of a myofibril extending from one Z line to the next one
Action of a muscle
potential movement that may occur when the muscle contacts
Are all muscles multi-actioned?
Some muscles have only one stated action, others have two or more
What happens when a muscle contracts?
there may be no movement, the stated action, or the opposite (antagonistic) action
muscles with the same stated action
muscles with opposite action to another muscle. When a given body motion occurs, the opposite can be effected by antagonists, gravity, or elastic recoil
is antagonistic to one or more actions of a multi-actioned muscle
Skeletal muscle are under direct ____ control of the ____
voluntary - CNS
terms used to name muscles are descriptive and are reflective of the muscle's shape, size, fiber orientation, action, location in the body, number of subdivisions, attachments and/or the part of the body acted upon
How many skeletal muscles are in the human body?
about 600 - most are paired
7 major groups of muscles
muscles of the head, neck, back, thorax, abdomen, superior limbs, and inferior limbs
Subdivisions of muscles of the head
muscles of the face, eye, auditory ossicles, mastication, tongue, and palate/fauces
Subdivisions of muscles of the neck
suboccipital, suprahyoid, infrahyoid, pharyngeal, and laryngeal muscles plus an unnamed group
Subdivisions of muscles of the thorax
11 muscles belong to the thorax and are not subdivided into groups
Muscles of the abdomen include...
those that form the anterior, lateral, and posterior abdominal walls as well as those forming the pelvis and urogenital diaphragms
Muscles of the back primary action
to bend the vertebral column
Subdivisions of muscles of the back
epaxial (behind the transverse processes of the vertebrae), and a hypaxial group (in front of the latter)
Subdivisions of muscles of the superior limb
shouder/scapula, anterior brachium, posterior brachium, anterior antebrachium, posterior antebrachium, and manus (three subgroups)
Subdivisions of muscles of the inferior limb
anterior/posterior/medial hip muscles, anterior/posterior/medial thigh muscles, anterolateral muscles of the crus, posterior muscles of the crus, and muscles of the foot (three subgroups)
Development of skeletal muscles
develop from various portions of the mesoderm
central part of mesoderm divides to form over 40 block-like segments called somites
muscle cell precursors called myoblasts develop in parts of the somites called myotomes
Paralysis of muscles
results from loss of innervation
the darker of the microscopically observable, alternating dark and light striations across myofibrils. The A bands represent those areas where thick myofilaments are located
the potential motion(s) associated with the muscle contraction. When a muscle contracts, this motion may or may not occur (depending on opposing forces
Belly of a muscle
the contractile part of a skeletal muscle. It is attached to other structures by tendons at each end and is sometimes divided into named subparts
a small bundle of muscle, nerve, or tendon fibers.
the nerve supply of a muscle or another body structure
body movement. Most locomotion is effected by contraction of skeletal muscles, but gravity and elastic recoil also play a role
a motor neuron plus the group of skeletal muscle cells that are innervated by it. Skeletal muscles contain many motor units which vary in size from small ones (involving a few muscle cells) to large ones (involving a few hundred muscle cells)
a muscle cell. The contraction of an individual muscle fiber is "all or none"
a contractile organelle found in the cytoplasm of a muscle cell. The strength of contraction of a given muscle cell is related to the number of myofibrils that it contains
a poteinaceous contractile element found within a myofibril. Two major myofilaments are recognized: thick (myosin) and thin (actin)
a fluid-filled structure, similar to a synovial joint capsule, located between a bony prominence and the tendon or belly of a muscle
Functionally, a synovial bursa reduces freictional degradation as the muscle moves reciprocally over the prominence
Synovial tendon sheath
a synovial 'bursa' that completely envelops a tendon. It has the same function as a bursa
the fibrous c.t. structure found at each end of a skeletal muscle belly. It is the non-contractile part of a muscle which attaches the belly to other structures