Chapter 11: The Muscular System

Spinal flexors of the vertebral column

- A few spinal flexors are associated with the anterior surface of the vertebral column - In the neck, the longus capitis & longus colli rotate or flex the neck depending on whether the muscles of one or both sides are contracting - In the lumbar region, the large quadratus lumborum flexes the vertebral column & depresses the ribs

Muscles of the iliopsoas group that move the thigh

- A pair of muscles controls the internal surface of the pelvis - The large psoas major originates alongside the inferior thoracic & lumbar vertebrae - Its insertion lies on the lesser trochanter of the femur - Before reaching this insertion its tendon merges with that of the iliacus which nestles in the iliac fossa - These two powerful hip flexors are often grouped together & collectively referred to as the iliopsoas

Description of fixator

- A synergist that assists an agonist by preventing movement at another joint, thereby stabilising the origin of the agonist - During flexion of elbow, the trapezium & rhomboid act as fyxators by stabilising & preventing the movement of the scapula

Calcaneal tendon (achilles tendon)

- A tendon shared by the gastrocnemius & soleus muscles, & this tendon inserts into the calcaneus - Although its among the largest & strongest tendons in the body, its rupture is common - The applied forces increase markedly during rapid acceleration or deceleration - Common in sprinters & elderly - Surgery maybe needed to reposition & reconnect the torn ends of the tendon to promote healing

Description of Agonist

- AKA Prime mover, is a muscle whose contraction is mostly responsible for producing a particular movement - Biceps brachii is an agonist that produces flexion at the elbow

Appendicular muscles

- Appendicular musculature positions & stabilises the pectoral & pelvic girdles, & moves the upper & lower limbs - There are two major groups of these muscles: 1) muscles of shoulder (pectoral girdles) & upper limbs 2) muscles of pelvis (pelvic girdle) & lower limbs - The functions & required ranges of motion are very different between these groups

Agonist & Antagonist

- Are functional opposites - If one produces flexion, the other produces extension

Subclavius and pectoralis minor as muscles that position the pectoral girdle

- Are two deep chest muscles that arise along the anterior surfaces of the ribs on either side - Subclavius originates on the first rib & inserts on the inferior border of the clavicle - When it contracts, it depresses & protracts the scapular end of the clavicle, causing the shoulder joint to move - Pectoralis minor originates on anterior surfaces of ribs 2-4 (or 2-5 etc) & attaches to the coracoid process of the scapula - The contraction of this muscle generally acts as a synergist to the subclavius

Bones as levers introduction

- Attaching muscle to lever can modify the force, speed, or direction of movement produced by a muscle contraction - A lever is a rigid structure (bone) that moves on a fixed point called a fulcrum (joint) - It moves when an applied force (pressure from muscles) is sufficient to overcome a load that would otherwise oppose or prevent such movement

Principle axial muscles of the body

- Axial muscles fall into logical groups on the basis of location, function, or both - Groups don't always have distinct anatomical boundaries - Four main groups: 1) Muscles of head & neck 2) Muscles of vertebral column 3) Oblique & rectus muscles 4) Muscles of the pelvic floor

Muscles of shoulder (pectoral girdles) & upper limbs

- Can divide these into four groups: 1) muscles that position the pectoral girdle 2) muscles that move the arm 3) muscles that move the forearm & hand 4) muscles that move the fingers

Extensors of the knee

- Collectively, four knee extensors which are the three vastus muscles (originate along the shaft of the femur), & the rectus femoris, make up the quadriceps femoris (AKA the quads) - Together the vastus muscles cradle the rectus femoris the way a bun surrounds a hot-dog - All four muscles insert in the patellar by way of the quadriceps tendon - The force of their contraction is relayed to the tibial tuberosity by way off the patellar ligament - Rectus femoris originates on the anterior inferior iliac spine & the superior acetabular rim, thus in addition to extending the knee it assists in flexion of the hip

Large superficial trapezius as a muscle that positions the pectoral girdle

- Commonly called traps, it covers the back & portions of the neck reaching to the base of the skull - This muscle originates along the midline of neck & back (axial skeleton), & inserts on the clavicles & scapular spines - The trapezius is innervated by more than one nerve, for this reason specific regions can be made to contract independently & their actions are quite varied

Biceps brachii muscle for action at the elbow

- Contraction of the biceps brachii flexes the elbow & supinates the forearm - With the forearm pronated (palm facing posteriorly) the biceps brachii cannot function effectively - Is important for stabilising the shoulder joint - The short heads originates on the coracoid process & supports the posterior surface of the joint capsule - The long head originates at the supraglenoid tubercle inside the shoulder joint - After crossing the head of the humerus it passes along the intertubercular sulcus - In this position the tendon helps to hold the head of the humerus within the glenoid cavity while arm movements are underway

Triceps brachii muscle for action at the elbow

- Contractions of the triceps brachii extends the elbow e.g. when you do push ups

Description of Synergist

- Contracts to help a larger agonist work efficiently - May provide an additional pull or stabilise the point of origin - Important in assisting a particular movement that may change as the movement progresses - Often most useful at the start, when agonist is stretched & unable to develop maximum tension

Muscles of the vertebral column

- Covered by more superficial back muscles, e.g. trapezius & latissimus dorsi - Main muscles of this group are the erector spinae muscles which include superficial & deep layers - The superficial layer can be separated into spinalis, longissimus, & iliocostalis groups - In the inferior lumbar & sacrial regions the boundary between the longissimus & iliocostalis is indistinct

Fibularis muscles that move the foot and toes

- Deep to the gastrocnemius & soleus are a pair of fibulas muscles, longus & brevis (or peroneus) - The fibularis produces eversion & extension (plantar flexion) at the ankle - Inversion is caused by the contraction of the tibias muscles - The large tibias anterior flexes the ankle & opposes the gastrocnemius

Muscles of the vertebral column in the deep layer

- Deep to the spinalis muscles, smaller muscle interconnect & stabilise the vertebrae - These include the semispinalis group, the multifidus group & the interspinalis, intertransersarii, & rotatores - In various combinations they produce slight extension or rotation of the vertebral column - They are also important in making delicate adjustments in the positions of individual vertebrae & they stabilise adjacent vertebrae

Structural Characteristics in naming muscles: Origin & Insertion

- E.g. Biceps brachii is named after its origin as it has 2 tendons of origin (bi = 2; + camput = head), while similarly triceps brachii has 3, & the quadriceps femurs has 4 - First part of name indicates origin, & second part indicates insertion - E.g. genioglossus originates at chin (geneion) & inserts in the tongue (glossus)

Muscles of the pelvic floor

- Extend from the sacrum & coccyx to the ischium & pubis - These muscles (1) support the organs of the pelvic cavity, (2) flex the sacrum & coccyx & (3) control the movement of materials through the urethra & anus

Muscles of the gluteal group that move the thigh

- Gluteal muscles cover the lateral surfaces of the ilia - The gluteus maximus is the largest & most posterior of the gluteal muscles - Its origin includes parts of the ilium, the sacrum, coccyx , & the thoracolumbar fascia - Acting alone this massive muscle produces extension & lateral rotation at the hip joint - Gluteus maximums shares an insertion with the tensor fasciae latae which originates on the iliac crest & the anterior superior iliac spine - Together these muscles pull on the iliotibial tract which is a band of collagen fibres that extend along the lateral surface of the thigh & inserts on the tibia - This tract provides a lateral brace for the knee which becomes important when balancing on one foot - The gluteus medius & gluteus minimus originate anterior to the origin of the gluteus maximus & insert on the greater trochanter of the femur - The anterior gluteal line of the lateral surface of the ilium marks the boundary between these two muscles

Muscle patterns in the arm

- In general, the extensor muscles lie along the posterior & lateral surfaces of the arm, where as the flexors are on the anterior & medial surfaces - Connective tissue partions separate major muscle groups, dividing the muscles into compartments formed by dense collagenous sheets - The brachialis & brachioradialis flex the elbow & are opposed by the anconeus & the triceps brachii respectively

Functional groups of the muscles of the head & neck

- Include muscles of the facial expression, the muscles of mastication (chewing), the muscles of the tongue, & the muscles of the pharynx - Originate on the skull or hyoid bone - Muscles involved with sight & hearing also are based on the skull

Muscles of the anterior neck

- Include muscles that control the position of the larynx, muscles that depress the mandible & tense the floor of the mouth, & muscles that provide a stable foundation for muscles of the tongue & pharynx

Flexors of the knee

- Include the biceps femoris, semitendinosus, semimembranosus, sartorius, & popliteus - Thes muscles originate along the edges of the pelvis & insert on the tibia & fibular

The oblique group of muscles

- Includes the scalene muscles of the neck & the intercostal & transversus muscles of the thorax - The scalene muscles (anterior, middle, & posterior) elevate the first two ribs & assist in flexion of the neck - In the thorax the oblique muscles extend between the ribs, with the external intercostal muscles covering the internal intercostal muscles - Both groups of intercostal muscles aid in breathing movements of the ribs

Pitcher's arm

- Inflammation at the origins of the flexor carpi muscles at the medial epicondyle of the humerus - Condition results from forcibly flexing the wrist just before releasing a baseball

Carpal tunnel syndrome

- Inflammation of the retinacula and synovial tendon sheaths can restrict movement & out pressure on the distal portions of the median nerve, a mixed (sensory & motor) nerve that innervates the hand - This condition causes tingling, numbness, weakness, & chronic pain - A common cause is repetitive hand or wrist movements

Rectus abdomenis (AKA the "abs')

- Inserts at the xiphoid process & originates at the pubic symphysis - This muscle is longitudinally divided linea alba (white line), a median collagenous partion - Is separated into segments by transverse bands of collagen fibres called tendinous inscriptions

Supination & pronation

- Involve changes in the relationship between the bones of the forearm, the radius & the ulna - These changes also result in movement of the palm of the hand - For this reason the muscles involved in these processes are the supinator & pronator teres which originate on both the humerus & the ulna - These muscle rotate the radius without either flexing or extending the elbow - The square shaped pronator quadratus originates on the ulna & assists the pronator teres in opposing the actions of the supinator or biceps brachii - During pronation the tendon of the biceps brachii rotates with the radius

Description of Antagonist

- Is a muscle whose action opposes that of a particular agonist E.g. the triceps brachii is an agonist of that extends the elbow so for this reason its an antagonist of the biceps brachia - Likewise the biceps brachii is an antagonist of the triceps brachii

Digastric muscle of the anterior neck

- Is one of the main muscles that controls the position of the larynx - This muscles has two bellies, the anterior belly extends from the chin to the hyoid bone, while the posterior belly continues from the hyoid bone to the mastoid portion of the temporal bone - Depending on which belly contracts & whether fixator muscle are stabilising the position of the hyoid bone, the digastric can open the mouth by depressing the mandible, or can elevate the larynx by raising hyoid bone - Covers the mylohyoid

The sartorius as a flexor of the knee

- Is the only knee flexor that originates superior to the acetabulum - Its insertion lies along the medial surface of the tibia - Sartorius crosses over two joints & its contraction produces flexion at the knee & lateral rotation at the hip e.g. when you cross your legs

Forearm

- Is the region of the upper limbs between the elbow & the hand, & the hand is the region distal to the radiocarpel joint comprising the wrist, palm, & fingers - The muscles of this region can be grouped according to their actions at the elbow & hand, & include flexors, extensors, pronators, & supinators

Perineum

- Its boundaries are formed by the inferior margins of the pelvis - A line drawn between isichial tuberosities divides the perineum into two triangles: an anterior urogenital triangle and a posterior anal triangle - The superficial muscles of the urogenital triangle are the muscles of the external genitalia - They cover deeper muscles that strengthen the pelvic floor & encircle the urethra - An even more extensive muscular sheet, the pelvic diaphragm forms the muscular formation of the anal triangle, with this layer traveling as far as the pubic symphysis

Naming muscles based on action

- Many muscles are named flexor, extensor, pronator, abductor, adductor, & rotator - Are such common actions that names almost always include other clues as to appearance or location of muscle - E.g. extensor carpi radialis longus is a long muscle along the radial border of the forearm, & when it contracts it causes extension of carpus (wrist) - A few muscles are named after specific movements associated with special occupations or habits - E.g. the buccinator (translates as trumpeter) on the face compresses the cheeks (like when you blow a trumpet)

Muscles that move the foot and toes

- Most of the muscles that move the ankle produce the plantar flexion involved in walking & running movements - The gastrocnemius of the calf is an important plantar flexor, but the slow muscle fibres of the underlying soleus are better suited for making continuous postural adjustments against the pull of gravity - These muscles are best seen in posterior & lateral views - The gastrocnemius arises from two heads located on the medial & lateral epicondyles of the femur, just proximal to the knee - The fabella, a sesamoid bone is occasionally present in the tendon of the lateral head of the gastrocnemius

Origins of muscles that allow action at the elbow

- Most of the muscles that move the forearm & hand originate on the humerus & insert on the forearm & wrist - Two exceptions to this are the biceps brachii & triceps brachii - Biceps brachii & the long head of the triceps brachii originate on the scapula & insert on the bones of the forearm

Muscles of mastication (chewing)

- Move the mandible at temporomandibular joint - Includes temporalis, masseter, medial pterygoid, & lateral pterygoid - The large masseter is the strongest jaw muscle - The temporalis assists in elevating the mandible - The pterygoid muscles used in combination can elevate, depress, & protract the mandible or slide it from side to side (this is called lateral excursion)

Action of medial & lateral rotation at joints that permit rotation

- Movement or turning of the body part occurs around the joints axis - Shoulder joint is a ball-&-socket joint that permits rotation - Subscapularis has lines of action that cross the anterior aspect of the shoulder joint, when this contracts it produces medial rotation at joint - Teres minor has lines of action that cross the posterior aspect of the shoulder joint, when it contracts it produce lateral rotation at the shoulder

Muscles that move the leg

- Muscle distribution in the lower limb has a pattern: extensor muscles are located along the anterior & lateral surfaces of the leg & flexors lie along posterior & medial surfaces of the leg - Sturdy connective tissue partions divide the lower limb into separate muscular compartments - The flexors & adductors originate on the pelvic girdle, but most extensors originate on the femoral surface

Oblique & rectus muscles

- Muscle groups lie within the body wall, between the spinous processes (vertebral column) & the ventral midline - Oblique muscles compress underlying structures or rotate the vertebral column, depending on whether one or both sides contracts - Rectus muscles are important flexors of the vertebral column, acting in opposition to the rector spinae - Can subdivide each of these groups into cervical, thoracic, & abdominal regions

Postion, Direction, or Fascicle Arrangement

- Muscle visible at body surface often called externus or superficialis - Deeper muscle called internus or profundus - Superficial muscles that stabilise or position an organ called extrinsic, while muscles located entirely inside an organ are called intrinsic - Transverse muscle run across the body & oblique muscle run at a slanting angle to the longitudinal axis - Rectus (means straight) & most have fascicles that run along the longitudinal axis of the muscle

Origins & insertions

- Muscles have one fixed point of attachment (origin) - & one moving point of attachment (insertion) - Most muscles originate or insert on the skeleton - Origin is usually proximal to insertion

Muscles that move fingers

- Muscles of the forearm provide strength & gross motor movement of the hand & fingers - These muscle sae known as the extrinsic muscles of the hand - Fine motor movement of the hand involves small intrinsic muscles which originate on the carpel & metacarpal bones - No muscles originate on the phalanges & only tendons extends across the distal joints of the fingers

Muscles that move the thigh within the four muscle groups

- Muscles of the gluteal group are the gluteus maximus, gluteus medius, gluteus minimus, & tensor fasciae latae - Muscles of the lateral rotator group are the obturators (externus & internus), piriformis, gemellus (superior & inferior), & quadratus femoris - Muscles of the adductor group include adductor brevis, adductor longus, adductor magnus, pectineus, & gracilis - Muscles of the iliopsoas group are the iliacus & psoas major

Muscles that move the arm that originate on the scapula

- Muscles that move the arm have their actions at the shoulder joint - The deltoid is the major abductor, but the supraspinatus acts as a synergist at the start of this movement - The sub-scapularis & teres major produce medial rotation at the shoulder, whereas the infraspinatus & the teres minor produce lateral rotation - The small coracobrachialis is the only muscle attached to the scapula that produces flexion & abduction at the shoulder

Action of flexion & extension at joints that permit it

- Muscles whose lines of action cross the anterior side of a joint are flexors of that joint - While muscles whose lines of action cross the posterior side of the joint are extensors of that joint - E.g. biceps brachii is a flexor of the elbow joint, while triceps brachia is an extensor of the elbow joint

Action of abduction & adduction at joints that permit it

- Muscles whose lines of action cross the medial side of a joint are adductors of that joint - While muscles whose lines of action cross the lateral side of the joint are abductors of that joint - E.g. gluteus medius & minimus are abductors of the hip joint, while adductor magnus is a an adductor pf the hip joint

Three other muscles of the anterior neck

- Mylohyoid elevates the floor of the mouth or depresses the jaw when the hyoid bone is fixed - Aided by the deeper geniohyloid that extend between the hyoid bone & the chin - Stylohyoid forms a mucular connection between the hyoid bone & the styloid process of the skull

Muscles of the tongue

- Needed for speech, manoeuvring food & preparation for swallowing - Include genioglossus, styloglossus, hyoglossus, & palatoglossus - Palatoglossus originates at the palate, styloglossus at the styloid process of the temporal bone, the genioglossus at the chin, & the hyloglossus at the hyoid bone

Muscles of facial expression

- Originate on the surface of the skull - Largest group of facial muscles is associated with the mouth - Orbicularis orgs constricts the mouth opening - Buccinator has two functions including chewing & providing suction (e.g. in infants) - Smaller groups of muscles control eyebrows, eyelids, scalp, nose, & external ear - Scalp (epicranium) contains temporoparietalis & the occipitofrontalis, which has a frontal belly & a occipital belly - The two bellies are separated by the epicranial aponeurosis (a thick collagenous sheet) - Platysma covers the anterior surface of the neck

Serratus anterior as a muscle that positions the pectoral girdle

- Originates along the anterior surface of several ribs - This fan shaped muscle inserts along the anterior margin of the vertebral border of the scapula - When the serratus anterior contracts it abducts (protracts) the scapula & swings the shoulder anteriorly

Oblique & rectus muscles of the abdominal region

- Pattern of musculature extends unbroken across the abdominopelvic surface - Here the muscles are the external oblique, internal oblique, transversus abdomenis, & the rectus abdomenis (AKA the "abs')

Muscles of the pelvis and lower limbs

- Pelvic girdle is tightly bound to axial skeleton, permits little movement - Few muscles of the axial musculature can influence the position of the pelvis - However the muscles that position the lower limbs provide a range of movements within these limbs - These muscle can be divided into three functional groups: 1) Muscles that move the thigh 2) Muscles that move the leg 3) Muscles that move the foot & toes

The diaphragm

- Refers to any muscular sheet that forms a wall - Is a major muscle that separates the abdomen-pelvic & thoracic cavities - It is used in breathing

Rhomboid major, rhomboid minor, & elevator scapulea as three muscles that position the pectoral girdle

- Revealed by removing the trapezius - These muscles are attached to the posterior surfaces of the cervical & thoracic vertebrae - They insert along the vertebral border of each scapula, between the superior & inferior angles - Contraction of a rhomboid abducts (retracts) the scapula on that side - The elevator scapulae elevates the scapula

Muscles associated with the fingers

- Several superficial & deep muscles of the forearm flex & extend the finger joints - These large muscles end before reaching the wrist & only their tendons cross the articulation - This arrangement ensures maximum mobility at both wrist & hand - The tendons that cross both posterior & anterior surfaces of the wrist pass through synovial tendon sheaths, elongated bursae that reduce friction

Structural Characteristics in naming muscles: Shape & Size

- Shape sometimes an important clue to name of a muscle - E.g. the trapezius, deltoid, rhomboid, & orbicularis look like a trapezoid, a triangle, a rhomboid, & a circle, respectively - Many terms refer to muscle size - Long muscles are called longus (long) or longissimus (longest) - Teres muscle are both long & round - Short muscles are called brevis - Large ones are called magnus (big), major (bigger), or maximus (biggest) - Small ones are called minor (smaller) or minimus (smallest)

Extrinsic eye muscles

- Six muscles attach to the outer surface of the eye and produce eye movements - Superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, & inferior oblique

Muscles that don't originate at bone

- Some originate at connective tissue sheath or band - E.g. intermuscular septa & tendinous inscriptions

Muscles of the spinalis group in the superficial layer

- Spinalis cervicis has origin of inferior portion of ligamentum nuchae & spinous process (of C7) - Spinalis thoracis has origin of spinous process of inferior thoracic & superior lumbar vertebrae

Sternocleidomastoid muscle and omohyoid muscle of the anterior neck

- Sternocleidomastoid extends from the clavicle & the sternum to the mastoid region of the skull & turns the head obliquely to the opposite side - Omohyoid attaches to the scapula, the clavicle, & the first rib, & the hyoid bone - The other members of this group are strap-like muscles

Strap-like muscles of the anterior neck

- Sternothyroid muscles extend between the sternum & larynx - Sternohyoid muscles extend between the sternum & the hyoid - Thyrohyoid muscles extend between the larynx & the hyoid bone

Rotator cuff muscles (hint: SITS)

- Supraspinatus - Infraspinatus - Teres Minor - Subscapularis

Muscle sphincters

- Surround the passageways (of urethra, anus, (& vagina)) & the external sphincters permit voluntary control of urination & defecation - Muscles, nerves, & blood vessels also pass through the pelvic outlet as they travel to or from the lower limbs

Muscles of the adductor group that move the thigh

- The adductors originate inferior to the horizontal axis of the acetabulum - This muscle group includes adductor brevis, adductor longus, adductor magnus, pectineus, & gracilis - All but adductor magnus originates both anterior & inferior to the joint so they perform hip flexion as well as adduction - The adductor magnus can produce either adduction & flexion or adduction & extension depending on the region stimulated - Adductor magnus can also produce medial or lateral rotation of the hip - The other muscles which insert in low ridges along the posterior surface of the femur produce medial rotation

Description of third-class lever

- The applied force is between load & the fulcrum i.e. F-AF-L - Most common levers in the body

The "hamstrings" as a flexors of the knee

- The biceps femoris, semitendinosus, & semimembranosus are often called the hamstrings - Because they originate on the pelvic surface inferior & posterior to the acetabulum their contractions produce not only flexion at the knee, but also extension at the hip - A pulled hamstring is a common sports injury caused by strain effecting one of the mastering muscles

Fascia thickenings of the wrist & their functions

- The fascia of the forearm thickens on the posterior surface of the wrist forming the extensor retinaculum - This is a wide band of connective tissue which holds the tendons of the extensor muscle in place - On anterior surface, the fascia also thickens to form another wide band of connective tissue called the flexor retinaculum which stabilises the tendons of the flexor muscles

Actions of the hand in terms of the wrist

- The flexor carpi ulnaris, flexor carpi radialis, & the palmaris longus are superficial muscles that work together to produce flexion of the wrist - Flexor carpi radialis flexes & abducts, & the flexor carpi ulnaris flexes & adducts

Description of first-class lever

- The fulcrum (F) lies between the applied force (AF) & the load (L) e.g. L-F-AF - The body has a few first-class levers e.g. there is one involved in extension of neck & lifting the head

The popliteus as a flexor of the knee

- The knee joint can be locked at full extension by a small lateral rotation of the tibia - The small popliteus originates on the femur near the lateral condyle & inserts on the posterior tibial shaft - When flexion is started this muscle contracts to produce a slight medial rotation of the tibia that unlocks the knee joint

Muscles of the lateral rotator group that move the thigh

- The lateral rotators originate at or inferior to the horizontal axis of the acetabulum - There are 6 lateral rotator muscles in all - The piriformis & obturator are dominant

Description of second-class lever

- The load lies between the applied force & the fulcrum i.e. F-L-AF - The body has a few second-class levers e.g. is involved in ankle extension by the calf muscles

Other muscles that move the arm

- The pectoralis major extends between the anterior portion of the chest & the crest of the greater tubercle of the humerus - The latismus dorsi extends between the thoracic vertebrae at the posterior midline & the intertubercular sulcus of the humerus - The pectoralis major produces flexion at the shoulder joint, & the latismus dorsi produces extension

Digital muscles

- These important muscles originate on the surface of the tibia, the fibula, or both - Large synovial tendon sheaths surround the tendons of the tibias anterior, extensor digitorum longus, & extensor hallucis longus, where they cross the ankle joint - The positions of these sheaths are stabilised by superior & inferior extensors retinacula - Intrinsic muscles of the foot originate on the tars & metatarsal bones, their contractions move the toes & maintain the longitudinal arch of the foot

Axial muscles: Muscles of the pelvic floor

- These muscles extend between sacrum & pelvic girdle - This group forms the perineum which is a region anterior to the sacrum & coccyx between the inner thighs

Axial muscles: Oblique & rectus muscles

- This group forms the muscular walls of the trunk between the first thoracic vertebra & the pelvis - In the thoracic area the ribs separate these muscles but over the abdominal surface the muscles form broad muscular sheets - The neck also has oblique & rectus muscles, they don't form a complete muscular wall but they share a common developmental origin with the oblique & rectus muscles of the trunk

Axial muscles: Muscles of the head & neck

- This group includes muscles that move the face, tongue, & larynx - They are responsible for verbal & non-verbal communication - E.g. used for talking, eating, & eye movement - This group doesn't include muscles of the neck that involved in movements of the vertebral column

Axial muscles: Muscles of vertebral column

- This group includes numerous flexors, extensors, & rotators of the vertebral column

Muscles of the pharynx

- Three pharyngeal constrictor muscles move food (in a bolus) into to the oesophagus by constricting the pharyngeal walls - Superior pharyngeal constrictor, middle pharyngeal constrictor, & inferior pharyngeal constrictor - Two paletal muscles elevate the soft palate & pull open the entrance to the auditory tube - Laryngeal elevators raise the larynx

Insertions of muscles that allow action at the elbow

- Triceps brachii inserts on the olecranon of the ulna - Biceps brachii inserts on the radial tuberosity, roughened bump on the anterior surface of the radius

Four functional types for how muscles work together

1) Agonist 2) Antagonist 3) Synergist 4) Fixator

Two reasons the vertebral column doesn't have massive flexor muscles

1) Many of the large trunk muscles flex the vertebral column when they contract 2) Most of the body weight lies anterior to the vertebral column so gravity tends to flex the spine

Four types of muscle types according to arrangement of fascicles

1) Parallel 2) Convergent 3) Pennate (more powerful than parallel) 4) Circular (AKA sphincter)

Important things levers can change

1) The direction of an applied force 2) The distance & speed of movement created by an applied force 3) The affective strength of an applied force

Three classes of levers

1. first-class lever 2. second-class lever 3. third-class lever