Chapter 9, 10 , 11 ( muscular system) Flashcards
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 of skeletal muscles
• strength related to the total number of myofibers (muscle cells) in the muscle
range of motion
• 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
parallel muscle
o 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%
circular
o – 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
convergent
o fasciculi arrive at one common attachment
♣ tendon, tendinosus sheet, or raphe - slender band of collagen fibers
♣ fibers spread out in fan-like manner
pennate –
o 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
♣ does not move tendon as far as a parallel muscle of the same size – but produces more tension
• 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
• actions = movement produced when muscle contracts
agonist
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
antagonist
o antagonist = muscle contraction whose action that counteracts the agonist movement – e.g. extension
fixators
o 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 – specific region of the body (brachialis, capitus)
o size (gluteus maximus)
o length – longus (long), brevis (short)
o shape (deltoid – triangular)
o orientation of fascicles – transverse, oblique, rectus - straight with the axis of the bone (rectus femoris)
o origin and insertion (sternocleidomastoid – origin sternum and clavicle, insertion mastoid process of temporal bone)
o relative position – posterior, anterior, profundus (deep), superficialis
o number of heads (biceps – two heads)
o function (adductor pollicus)
Divisions of Skeletal Muscle System
• Axial musculature – origins and insertions 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
Axial muscles - Head and neck muscles
• 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
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
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 causes “crow’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
♣ corrugator supercilii – draws eyebrows inferiorly and medially producing vertical corrugations between eyes – origin = nasal bridge
Extra-Ocular Muscles
o 6 extra-ocular (extrinsic eye) muscles rotate eyeball within orbit to allow vision in a wider range of directions
origins = surface of orbit, insertions = sclera (thick fibrous outer layer of wall of eye
- rectus muscles
- oblique muscles
- diplopia
- strabismus
rectus muscles
o rectus muscles = nearly straight with axis of eye and rotate eye in direction of their attachment
♣ superior rectus – “look up”
♣ inferior rectus – “look down”
• superior and inferior are slightly offset so also bring eye medially
♣ lateral rectus – abducts eye “look to the side”
♣ medial rectus – adducts eye “look to the nose”
oblique muscles
o = oriented at an oblique axis of the eye inserting into posterior lateral margin
♣ superior oblique – moves eye “down and out”
♣ inferior oblique – moves eye “up and out”
diplopia
o double-vision - each eye not focused on same image and get two separate images
♣ can result from paralysis or weakness of certain extrinsic muscles or neurological diseases
strabismus
o congenital weakness of external eye muscles in which eye rotates medially “cross-eyed” or laterally “wall-eyed”
♣ to compensate eyes may alternate focusing on objects, or only the controllable eye may be used and the brain ignores the input from the other eye making it functionally blind (amblyopia)
Mastication
chewing
o move mandible at temporomandibular joint
elevator of mandible
o – brings mandibular teeth forcefully against maxillary teeth to crush food
♣ masseter – elevates and protracts mandible; origin = zygomatic arch, insertion = mandibular ramus
• most powerful and important muscle
♣ temporalis – elevates and retracts mandible; origin = temporal fossa of parietal bone, insertion = mandibular ramus and coronoid process of mandible
♣ medial pterygoid – elevates and protracts mandible; origin = pterygoid plate of sphenoid bone
♣ lateral pterygoid – protracts and depresses mandible; origin = pterygoid plate of sphenoid bone
o slight mandibular depression due to relaxation of the elevators and pull of gravity – “slack jaw”
o grinding food between teeth = medial and lateral excursion of mandible – and all muscles of mastication
Muscle of the tongue
o important in mastication and speech
♣ moves food around mouth
♣ holds food in place
♣ pushes food up to palate and back toward pharynx to initiate swallowing
♣ changes shape to modify sound during speech
intrinsic muscle of tongue
within the tongue itself – change shape of tongue
extrinsic muscle of tongue
o = outside of tongue but attach to it
♣ names end in glossus – meaning tongue
♣ most origins = bone (mandible, styloid process of temporal bone, hyoid)
♣ change shape of tongue, and move it – up, down, out, back
Muscles of the Pharynx
o important for swallowing - involves muscles of the hyoid, soft palate, pharynx and larynx
pharyngeal constrictors
o pharyngeal constrictors (superior, middle and inferior) – initiation of swallowing
♣ move food bolus (mass of food) into esophagus
laryngeal elevators
o laryngeal elevators – “-pharyngeous” muscle insert onto thyroid cartilage and elevate the larynx
♣ salpingopharyngeus – together with palatal muscles opens auditory tube – equalizes pressure between middle ear and atmosphere
palatal muscles
o palatini” – elevate the soft palate
♣ close the posterior opening to the nasal cavity during swallowing
Anterior muscles of the neck
o control position of larynx, depress mandible, tense the floor of the mouth
extrinsic muscles of the larynx
o extrinsic muscles of the larynx – position the larynx
♣ narrow or close laryngeal opening so food does not enter larynx
intrinsic muscles of the larynx
o contraction affects the vocal cords
♣ shortening vocal cords lowers the pitch of the voice
♣ lengthening raises the pitch of the voice
suprahyoid muscles
o depress mandible, opening mouth and/or elevates mandible;
♣ digastric, geniohyoid, mylohyoid, stylohyoid - insertion = hyoid bone
infrahyoid group
o depress the larynx
♣ omohyoid, sternohyoid, sternothyroid - insertion = hyoid bone
o sternocleidomastoid
♣ one contracting laterally flexes head to shoulder on same side or rotates head and neck to opposite side
♣ both contracting together flex neck
♣ origin = manubrium and medial clavicle; insertion = mastoid process and superior nuchal line
laryngospasm
o tetanic contraction of the muscles that narrow the opening of the larynx
♣ occurs when food or liquid “goes down the wrong way”
♣ can result from severe allergic reactions, tetanus infections or hypocalcemia
♣ typical episode lasts 30-60 seconds
• severe cases opening is closed completely and air cannot pass through the larynx to the lungs
• botulinum toxin – injection can relax muscles
tracheotomy
Muscles of Vertebral Column
• has many extensors but few flexors
o many of the large trunk muscles flex the vertebral column when they contract
o most of the body weight lies anterior to the vertebral column and gravity tends to flex spine
longus capitis
o – transverse processes of C4-C6 to base of occipital bone
♣ together - flex neck; one side – rotates neck to that side
longus colli
o anterior margins of the cervical vertebrae to transverse processes of superior cervical vertebrae insertion = occipital bone
♣ flexes neck
• extensor muscles of back arranged into 3 layers:
superficial, intermediate, deep
superficial layer
♣ splenius muscles (splenius capitus and splenius cervicis) – origin: ligamentum nuchae and spines of vertebrae (C7-T6), insertion: mastoid process, occipital bone, superior cervical vertebrae
• together - extend neck; one side – rotates and laterally flexes neck to that side
♣ trapezius, latissimus dorsi, levator scapulae, and rhomboids
• position pectoral girdle and upper limb (see appendicular muscle section below)
intermediate layer
♣ erector spinae – group of muscles on either side of spine that extend the head, neck and vertebral column
what are the 3 subgroups of intermediate layer
• 3 subgroups (superior to inferior)
o spinalis –origin: C6-C7, T11-T12 (most medial)
o longissimus – accounts for most of the muscle mass in the lower back; origins: cervical and thoracic vertebrae
o iloiocostalis – origin: sacrum, illium and lumbar spines (most lateral)
• each subgroup has muscles that insert on the skull – capitus; upper cervical vertebrae – cervicis; and lower cervical and upper thoracic vertebrae – thoracis
o capitus and cervicis groups: together - extend neck; one side – rotates and laterally flexes neck to that side
o thoracis groups: extend vertebral column; one side – lateral flexion to that side
♣ serratus posterior muscles
♣ serratus posterior muscles - assist in rib movement during inspiration
o deep layer = intrinsic back muscles
♣ transversopinalis muscles - interconnect and stabilize vertebrae
• semispinalis group, mulitidus, rotatores, interspinales, intertrranversarii muscles
• short muscles that work in combinations to produce slight extension or rotation of vertebral column
Oblique and Rectus Muscles
- lie between vertebral column and ventral midline
* have cervical, thoracic and abdominal groups
oblique muscles
cervical region
• compress underlying structures or rotate vertebral column
o cervical region
♣ scalenes – origin = cervical vertebrae; insertion = first and second ribs
• elevates ribs and/or flex neck; one side bends neck and rotates to same side
oblique muscles - thoracic region
o thoracic region
♣ external intercostals – elevates ribs during quiet inspiration
• origin: inferior margin of each rib, insertion: superior border of next rib below
• superficial to internal intercostals
♣ internal intercostals – depresses ribs during forced expiration; origin: superior margin of each rib, insertion: inferior border of next rib above
oblique muscles - abdominal regions
o – muscles compress abdomen; depress ribs; flexes, laterally flexes and rotates vertebral column
♣ crossing pattern of abdominal muscles creates strong anterior wall
♣ external obliques – superficial lateral abdominal muscle; origin: 5th to 12th ribs, insertion: iliac crest, rectus sheath
♣ internal obliques – middle lateral abdominal muscle; origin: iliac crest, lumbar fascia, insertion: 10th to 12th ribs and rectus sheath
♣ transversus abdominis – deepest abdominal muscle; origin: 7th to 12th costal cartilages, lumbar fascia, insertion: xiphoid process, linea alba, pubis
rectus muscles
• – oppose erector spinae – flex vertebral column
o rectus abdominus – on either side of linea alba and covered by rectus sheath
♣ linea alba = located in the midline from the xiphoid process to the pubis = dense connective tissue
♣ origin: pubic crest and symphysis pubis, insertion: xiphoid process and inferior ribs
♣ depress ribs, flexes vertebral column, compresses abdomen
♣ tendinous inscriptions = bands of fibrous tissue that divide muscle into repeated segments “six-pack”
diaphragm
main muscle of inspiration – flattens to depress floor of thorax; origin: interior of lower ribs, sternum and lumbar vertebrae, insertion: central tendon of diaphragm
hernia
when visceral organ or part of an organ protrudes abnormally through an opening in a surrounding muscular wall or partition
inguinal hernia
o protrusion of portion of greater omentum or small intestine through inguinal canal
♣ more common in males
diaphragmatic hernia
o – abdominal organs slide into thoracic cavity
♣ hiatal hernia – if entry is through the esophageal hiatus (opening)
• very common and most go unnoticed
• increase severity of gastric acid entry in esophagus (gastroesophageal reflux, GERD)
Muscles of the Perineum and Pelvic Diaphragm
purpose ?
- extend from sacrum and coccyx to ischium and pubis
- support organs of pelvis cavity
- flex joints of sacrum and coccyx
- control movement of material through urethra and anus
perineum (pelvic floor
– boundaries = inferior margins of pelvis
o urogenital triangle (anterior portion) (Table 10.9)
♣ superficial muscles = muscles of external genitalia
♣ urogenital diaphragm = deeper muscles - strengthen pelvic floor and encircle urethra
• deep transverse perineal muscle and external urethral sphincter
o anal triangle (posterior portion) (Table 10.10)
♣ pelvic diaphragm = muscular foundation of anal triangle
• coccygeus, levator ani and external anal sphincter muscles