Muscles function, actions and identification of major superficial muscles, some conditions and treatments
types of muscles Three structurally and functionally distinct types of muscle are found in vertebrates: • smooth muscle, • skeletal muscle and • cardiac muscle.
functions of skeletal muscles • movement • posture • heat production • shape • facial expressions • chewing, swallowing • reflexes
naming skeletal muscles Skeletal muscles are named according to structural and/or functional characteristics. • Location - temporalis (temporal bone) and tibialis anterior (front of tibia) • Size - maximus (largest), minimus (smallest), longus (longest), brevis (shortest) • Shape – deltoid (triangular), trapezius (trapezoid), serratus (saw-like edge)
more on naming muscles • Direction of fibers – rectus (parrallel to midline), transverse (perpendicular to midline), oblique (diagonal to midline) • Number of origins – biceps (2), triceps (3), quadriceps (4) • Origin and insertion – sternocleidomastoid is named for the two places of origin as well as its insertion. • Action – what the muscle does when “at work.”
actions of skeletal muscles • flexion-movement that decreases the angle @ a joint • extension-movement that increases the angle @ a joint.
abd and add • abduction-movement of an appendage away from the midline. • adduction-movement of an appendage towards the midline.
rotation • rotation -turning around the longitudinal axis @ a joint.Can only occur at a pivot (radio-ulna / neck) or ball & socket (shoulder / hip) joint. • circumduction-Is a movement found @ ball & socket (hip & shoulder) and condyloid joints (wrist / ankle / knuckles).
supination- pronation • supination -medial rotation of the forearm at the Radio Ulna joint, so the palms face up. • pronation -Lateral rotation of forearm at the Radio Ulna joint, so the palms face down.
inversion -eversion • inversion- twisting of the foot so that the sole faces inward. • eversion- Twisting of the foot so that the sole faces outward.
dorsiflexion and plantar flexion dorsiflexion– toe towards the knee usingtibialis anterior plantar flexion–”point toes” usinggastrocnemius
shoulder girdle movements elevation - Upward movement of the shoulder girdle. depression - Downward movement of the shoulder girdle..Depression protraction and retraction are all movements associated with the shoulder girdle.
movements 1. Lateral rotation 2. medial rotation 3. Supination 4. Pronation 5. Eversion 6. Inversion 7. Adduction 8. Abduction
What do you know about these muscles? • Flexor carpi ulnaris • Extensor carpi radialis • Latissimis dorsi • Transversus abdominis • Rectus femoris • Deltoid • Trapezius • Orbicularis oris, Orbicularis oculi • Sternocleidomastoideus
skeletal muscle facts • Skeletal muscle consists of very long tubular cells. The average length of skeletal muscle cells in humans is about 3 cm (sartorius muscle up to 30 cm, stapedius muscle only about 1 mm). Their diameters vary from 10 to 100 µm. • Skeletal muscle fibres contain many peripherally placed nuclei.Up to several hundred rather small nuclei with 1 or 2 nucleoli are located just beneath the plasma membrane.
facts, continued • Skeletal muscle fibres show in many preparations characteristic cross-striations. It is therefore also called striated muscle. • Skeletal muscle is innervated by the somatic nervous system. • Skeletal muscle makes up the voluntary muscle.
what students of anatomy learn about the skeletal muscles • over 600 named muscles in human • makes up 40-50% of body weight • the physiology of muscle action • name, location, action, origin, insertion and often the nerve that serves the muscle
the players myofibrils contract instantly if ATP and Ca2+ is added to them, meaning that it is these single myofibrils which are the force generators in muscle cells.
sarcomere Striated sarcomeres are separated by Z-discs. Two Z-discs bound a sarcomere in the direction of stretching. Thin filaments made of Actin are attached to each of these discs and extend towards each other inside the sarcomere. They do not overlap in the sarcomere’s striated form. In this case there is a dark band visible between the Z-discs. This is made up of the thick Myosin filaments which overlap partially with the thin Actin filaments which extend into a light half of the I-Band region left and right of the dark A-band.
contraction = shorten When Myofibrils contract the thin and thick filaments move past each other. Each sarcomere unit of the myofibrils shortens proportionally to the muscle contraction. Upon contraction, it is the light bands which shorten whereas the dark bands do not change in length. This is explained by the Actin filaments sliding into the dark region of Myosin filaments.
thick and thin Actin - the thin filaments Myosin - the thick filaments
contraction During contraction, actin fibers are pulled inward a) pulling is by "hooks" on myosin (myosin heads) b) hooks bend, using energy of ATP c) each hook pulls, releases, pulls again until muscle is contracted d) calcium (Ca2+) ions signal this to start -Ca2+ into muscle starts contraction -during relaxation, Ca2+ is transported out
muscle ends • origin-stationary end, the anchor • insertion- moved end • belly- the area in between
CAUTION NOTE: These pictures are intended to provide a virtual tour of the lab models and specimens. They are not intended to substitute for classroom/lab learning. They are simply supplemental material for you to use as reminders of what you should study or have already studied.
superficial muscles Muscles which occupy the layer closest to the surface of the skin are called superficial muscles. These are easily displayed on a person who has developed their physique for show or physical performance.
major muscles of face • frontalis • orbicularis oculi • nasalis • temporalis • orbicularis oris • zygomaticus major • masseter • mentalis • levator labii superioris
Facial muscles around the mouth, directions of muscle contraction Alevator labii superioris B zygomaticus minor C zygomaticus major D risorius E depressor anguli oris F labii inferioris, G orbicularis oris
muscles of mastication • temporalis • medial and lateral pterygoids • masseter
masseter masseter and directions of the lower jawbone movement
sternocleidomastoid sternocleidomastoid muscle is the main muscle on the side of the neck.
neck pain The trapezius muscle is the one that tenses up most often. When you see people reaching back to massage their shoulders, it is the trapezius muscle that they are trying to loosen. The other two muscles that have a tendency to tighten up are the sternocleidomastoid (often called the sterno-mastoid) and the scalene muscles. Keep it Moving! The neck is by far the most mobile portion of the spine. Its ROM is generally 70 to 90 degrees.
bones of the neck, review The bones of the neck are called the cervical vertebrae. Every mammal on earth, even the giraffe, has 7 of them. In humans, the cervical vertebrae are obviously a lot smaller than those of giraffes. They are also a lot smaller than the vertebrae of the other areas of the human spine.
neck pain? Our necks need to use their mobility in order to maintain it. They work best when they can consistently move into and out of their full range of motion in a gentle - that is, not a jarring - way.
non-used necks = injuries We rotate our necks fully when we look over our shoulder and then back the car down the driveway. We extend our necks completely when we look up at the ceiling. The fact that we do not do these things often is one of the major reasons why our necks cause us problems. On occasion, when it’s essential for the neck to move to an extreme range of motion, it can’t cope with the job. That’s when injuries occur.
trapezius The trapezius covers a large section of the upper back. It conceals the upper part of the shoulder blade.
latissimus dorsi • The latissimus dorsi occupy the middle back on either side. • The gluteus maximus make up the back of the buttocks.
abdominal muscles 4 muscles of the abdominal area rectus abdominis external oblique internal oblique NS transversus abdominis NS
superficial muscles of the chest and front of the arm. • The shoulder muscles are called deltoids. These triangular muscles define the upper shoulders • biceps brachii are easily recognizable large bumps on the upper inside of the arm • The pectoralis muscles span the chest
superficial muscles of the posterior arm triceps brachii – extends the arm, straightening the elbow
anterior muscles of the thigh • Quads: extensor of knee rectus femoris vastus lateralis vastus medius vastus intermedialis • sartorius: cross leg • gracilis: adducts leg
posterior muscles of the thigh The hamstring muscle group comprises three muscles – • biceps femoris • semitendonosus • semimembranosus The action of these muscles is to bend the knee and extend the hip.
adductors of the thigh adductor magnus, longus, brevis and the pectineus, make up the adductor group. Groin pulls are a strain at the attachment of the adductors to the pubic bone.