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Lecture 8

BLG 700 Lecture Notes - Lecture 8: Anterior Inferior Iliac Spine, Anterior Superior Iliac Spine, Levator Labii Superioris


Department
Biology
Course Code
BLG 700
Professor
Nancy Woodley
Lecture
8

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Muscular System
Chap 9 (Section 9.6, 9.7), 10, 11
Skeletal muscles most extend from one bone to another and cross at least on joint
contraction causes movement pulling one bone toward another across a joint
o some attached to bone only on one end and to some other tissue on the other end e.g. to skin of
face allowing for facial expressions
strength related to the total number of myofibers (muscle cells) in the muscle
range of motion related to fascicle arrangement (bundles of muscle cells) (Fig 9.12)
o shape and size greatly influence the degree to which a muscle can contract and the amount of force it
can generate
o parallel muscles fascicules parallel to long axis of muscle and terminate on a flat tendon that spans
the width of the entire muscle
most skeletal muscles = parallel muscles
can be interrupted by transverse segments of connective tissue
may exhibit twisted or spinal arrangement
when activated can be shortened to a maximum of ~30%
o circular arranged in a circle around an opening and act as sphincters to close opening
when muscle contracts diameter of opening decreases
guard entrances and exits of internal passages
o convergent fasciculi arrive at one common attachment
tendon, tendinosus sheet, or raphe - slender band of collagen fibers
fibers spread out in fan-like manner
o pennate fasciculi emerge feather-like from a common tendon that runs the entire length of the
muscle
unipennate = fascicles arise from one side of the tendon only
bipennate = two sides of the tendon
multipennate = arranged in many places around central tendon
muscle terminology
o origin = fixed end of skeletal muscle, usually most stationary and proximal end of muscle
head = name given when muscle has multiple origins that converge to form one muscle
triceps brachii
o insertion = mobile end usually the distal end attached to the bone undergoing the greatest
movement
o belly = part of muscle between origin and insertion
o tendons long cable-like dense regular connective tissue that attach muscle to bone
aponeuroses = broad, sheet-like tendons
o innervation = nerve supply to a particular structure
one or more motor nerves control each muscle
actions = movement produced when muscle contracts
o agonist = muscle that produces a certain desired movement e.g. flexion
synergists = group of muscles working together to produce a movement e.g. hip flexors
prime mover = muscle within a synergistic group that plays the major role in the movement
o antagonist = muscle contraction whose action that counteracts the agonist movement e.g. extension
o fixators = prime movers and antagonists contract simultaneously to hold one bone in place relative to
the body while a usually more distal bone is moved
named according to:
o location (brachialis)
o size (gluteus maximus)
o length longus (long), brevis (short)
o shape (deltoid triangular)
o orientation of fascicles (rectus femoris straight with the axis of the bone)
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o origin and insertion (sternocleidomastoid origin sternum and clavicle, insertion mastoid process of
temporal bone)
o number of heads (biceps two heads)
o Function (abductor femoris)
Divisions of Skeletal Muscle System (Fig 10.1, 10.2)
Axial musculature origins on axial skeleton
o Positions head and vertebral column and assists in breathing by moving rib cage
Appendicular musculature stabilizes or moves components of appendicular skeleton
Axial Muscles
4 groups based on location and/or function
o Head and neck muscles, muscles of vertebral column, muscular walls of thoracic and abdominopelvic
cavities, muscles of the perineum and pelvic diaphragm
Head and Neck Muscles (Fig 10.3-10.9, Table 10.1-10.6)
A lot of these muscles are cutaneous they have origin that is on bone and have intersections on skin
Originate on skull or hyoid bone and not associated with vertebral column
Muscles of facial expression, extra-ocular muscles, muscles of mastication, muscles of the tongue, muscles
of the pharynx, and anterior muscles of the neck
o Responsible for verbal and non-verbal communication, feeding, and movement of eyes
Facial Expression (Fig 10.3, 10.4, Table 10.1)
o Cutaneous muscles origins on surface of skull and insertions via collagenous fibers of epimysium
(connective tissue wrapping skeletal muscles) woven into dermis of skin
Allow skin to twitch to remove irritants (e.g. insects)
Important in non-verbal communication
o Largest group associated with movement of mouth
Closing and puckering lips:
Orbicularis oris closes lips constricts opening while other muscles move lips or corners of
mouth
o Origin = nasal septum, maxilla, and mandible
Buccinator flattens cheek allows suckling and puckering
o Origin = mandible and maxilla
Smiling:
zygmaticus major and minor elevate and abduct upper lip; origin = zygomatic bone
levator anguli oris elevates angle of mouth; origin = maxilla
risoris abducts angle of mouth: origin = fascia of masseter
Sneering:
levator labii superioris elevates upper lip; origin = maxilla
Pouting or frowning:
Depressor annuli oris depresses angle of mouth; origin = mandible
Depressor labii inferioris depresses lower lip; origin = mandible
Mentalis- protrudes lower lip; origin = mandible
Name one or 2 anagonist that smile, antagonist are those that causes you to frown
A synergist is the same thing; ex name a synergist of zygmaticus major the synergist will be zygmaticus
minor
o Smaller group controls movement of eyebrows, eyelids, scalp, nose and external ear
occipitofrontalis raises eyebrows and furrows skin of forehead; origin = occipital bone; insertion =
skin of eyebrow and nose
Orbicularis oculi closes eyelids and auses o’s feet; origin = maxilla and frontal bones
levator palpebrae superior (Fig 10.5) raises upper lids; origin = lesser wing of sphenoid bone
Ptosis = droopy eyelid on one side usually indicates nerve damage leading to the muscle
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Corrugator supercilii draws eyebrows inferiorly and medially producing vertical corrugations
between eyes origin = nasal bridge
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