Vertebrate Muscular System

pectoralis

(downstroke muscle)

supracoracoideus

(upstroke muscle)

Muscle

- Can cause either locomotion of the organism itself or movement of internal organs. - Contractile tissue of the body & derived from mesodermal layer of embryonic germ cells

Muscles of 3rd and Successive Arches:

- In shark, constrictors above and below gill chambers plus levators (including cucullaries) that compress and expand gill pouches - In bony fish, muscles reduced; operculum plays important part in respiration

Muscles of Hyoid arch

- Moves hyoid arch - Aid in hearing (stapedial muscle) - Assist in moving lower jaw

Smooth muscle tissue

- Not striated - Involuntary - Has rhythm in some part (GIT) - Fusiform or spindle-shaped; contain centrally located nucleus - Provides movement of substances in hallow organs -Very slow

Cardiac muscle tissue

- Striated - Involuntary - Has rhythm - Branching; contain centrally located nucleus - Provides route for quick muscle action potentials throughout the heart

• Masseter & temporalis • Pterygoid • Digastric

- adductors of mandible are:

branchiomeric muscles

- associated with pharyngeal arches - series of skeletal & smooth muscles - adductors, constrictors, and levators operate jaws plus successive gill arches'

Muscle/ tissue or organ

- characterized by the ability to contract in response to a stimulus from nervous system.

Electric organs

- consists of number of electric discs (up to 20,000) piled in vertical or horizontal columns

Muscle cells

- contain contractile filaments moving past each other, changing the size of cell

Epimysium

- dense layer of collagen fibers that surrounds entire muscle; separates muscle from surrounding tissues & organs

Hypobranchial of Fish

- extend forward from pectoral girdle & insert on mandible, hyoid, and gill cartilages -strengthen floor of pharynx and assist branchiomeric muscles in elevating floor of mouth, lowering jaw, and extending gill pouches

Intrinsic

- integumentary muscles (arrector pili muscles) - entirely within the dermis - found in birds and mammals - mostly smooth muscles

Shortest bundles of epaxial

- invertebral, remain segmented; connects processes (spinous, transverse, zygapophyses) of adjacent vertebrae

Spinalis group

- lies close to neural arches - connects spinous processes or transverse processes with several vertebrae anteriorly

· Subvertebral muscles

- muscles forming longitudinal bands in roof of body cavity

extrinsic

- originated on axial skeleton & inserts on the girdles or skeleton of limbs - most develop from hypaxial blastemas - referred to as secondary appendicular muscles

intrinsic

- originated on the girdle as proximal muscles & inserts on distal parts - from from blastemas within the limb bud - called primary appendicular muscles

Perimysium

- surrounds group of 10-100 or more individual bundles of muscle fiber called fascicle

Endomysium

- surrounds individual skeletal muscle fiber (fascicle) & interconnects adjacent muscle fibers; scatted between endomysium & muscle fibers a

Stylopharyngeus

- used for swallowing

Skeletal muscle tissue

-Striated -Voluntary - No rhythm - Cylindrical; contain periphery located numerous nucleus -move bones thus creating movement -Fast to slow

Cardiac muscle tissue

-forms wall of heart -possess intercalated discs

extrinsic

-integumentary muscles (platysma) - originate (usually) on the skeleton and insert on underside of dermis - striated - move skin of amniotes

- aquatic urodeles: swimming - terrestrial: locomotion - other tetrapods: support abdomen, respiration, assist epaxial

Function of Hypaxials of Tetrapods

Defense Communication Locating prey (electrlocation)

Functions of electric organs

external oblique, internal oblique, and transverse

Hypaxial three layers

birds

Intrinsic musculature is reduced; pectoralis (downstroke muscle) and supracoracoideus (upstroke muscle) are enlarged

Longissimus group Iliocostalis group Spinous group

Longest bundles of epaxial muscles

Linea alba

Middorsal & midventral septa separate the myomeres od the 2 sides of bod

Appendicular Muscles

Move fins or limbs

40-50%

Muscle tissue constitute about how much body weight?

· Oblique (external & internal) · Transverse · Rectus muscles Subvertebral muscles

Muscles of lateral body wall of Hypaxial of tetrapods

Adductor mandibulae and intermandibularis

Operates jaws of shark and other dishes

Contractility

ability of muscle tissue to contract forcefully when stimulated by an action potential

tetrapods

appendicular muscles are much more complicated than in fish; greater leverage required for land locomotion; jointed appendages require complex muscles

reptiles

appendicular muscles more numerous and diverse than in amphibians; better support & increased mobility

amphibians

appendicular muscles much complex than in fish

fish

appendicular serve as stabilizers; intrinsic are limited in number & undifferentiated

mammals

appendicular similar to reptiles but more diverse

aponeuroses

attach flat muscle to another muscle or to several bones

Skeletal muscle tissue

attached to bones

origin

attachment of muscle tendons or aponeuroses to a stationary bone; usually proximal

insertion

attachment of the muscle tendons or aponeuroses to the movable bone; usually distal

Hypaxial

below septum

o Scapular deltoid o Latissimus dorsi o Rhomboideus o Serratus ventralis o Pectorals

chief extrinsic muscles of forelimbs of tetrapods include:

Metamerism

condition in which organism forms or possesses a linear series of body segments; segmented appearance created by the epaxial and hypaxial muscles

Muscle slings -

connection between muscles & when muscles activate together they can enhance stability

Intercalated discs

connects muscle fiber to another (unique to cardiac muscles)

tendons

connects muscles to bone

electroplax

disc with a large-coined shape cell

trapezius and latissimus dorsi

dorsal group of the forelimbs of extrinsic

Epaxial muscles

dorsal side muscle & support body; move head & tail (extend from the skull to the tip of the tail); aid in stride length

urodeles & some lizards

epaxials are metameric & referred to as dorsalis trunci

- Side to side movements of vertebral column - arch and support vertebral column - attach to and move skull

function of epaxial of terapods

Axial muscles

include skeletal muscles of the trunk & tail - extend forward beneath pharynx as hypobranchial muscles & muscles of tongue - present in orbits as extrinsic eyeball muscles - are metameric - segmental because of their embryonic origin; arise from segmental mesodermal somite

ligaments

joins bone to bone

iliocostalis group

lateral to longissimus & spinalis - arises on ilium & inserts on dorsal ends of ribs or uncinate process

Epaxial of Tetrapods

lie along vertebral column dorsal to transverse processes & lateral to neural arches - extend from base of skull to tip of tail

longissimus group

lies on transverse processes of vertebrae; includes the longest epaxial bundles

Smooth muscle tissue

located in walls of hallow internal structures

- Stylopharyngeus (arch III) - Intrinsic muscles of pharynx -Cucullaris

primary muscles of 3rd and successive arches include:

agonist

prime mover; contracting muscle causes desired action

Pelvic girdle

requires no muscular anchoring since it is attached directly to vertebral column, so extrinsic muscle is small in posterior limbs

Motion

result of alternating contraction & relaxation of muscles

· Myocommata

separates myomeres vertically

Myosepta

serve origins & insertions for segmented muscles

Hypobranchial of tetrapods

stabilize and move hyoid apparatus & larynx

synergist

steady or supports movement preventing unwanted movements and helping prime mover function efficiently; involved in addition to agonist & antagonist

Myology

study of muscle

longissimus dorsi, longissimus cervicis, longissimus capitis

subdivisions of longissimus group

higher tetrapods,

superficial epaxial bundles form long muscles that extend over many body segments; deep bundles are still segmented

pectoralis

ventral group of forelimbs of extrinsic

Hypaxial muscles

ventral side muscle & dominant in tetrapods; aid in respiration

Elasticity

· ability of muscle tissue to return to its original length & shape after contraction or extension

Extensibility

· ability of muscle to stretch without being damaged

Electrical excitability

· ability to respond to certain stimuli by producing electrical signals such as action potential

Epaxial

· above septum

Myomeres

· bundles of muscle fiber; series of segments

Deep fascia

· lines body walls & limbs - holds muscle with similar function together - allows free movement of muscles; carries nerves, blood vessels, & lymphatic vessels - fills space between muscles

antagonist

· relaxes as the agonist contracts

myosepta

· separate myomeres horizontally

Superficial fascia

· separates muscle from skin; contains adipose tissue that insulates body

Fascia

· sheet or broad band of fibrous connective tissue that supports & surrounds muscle and other organs

tongue of amniotes

• a "sac" anchored to hyoid skeleton & filled with hypobranchial muscle

cucullaris

• gives rise to trapezius, cleidomastoid, and sternocleidomastoid

Oblique and Transverse muscles of modern amniotes

• myosepta and ribs are restricted to the thorax (so abdominal muscles are not segmented)

Oblique and Transverse muscles of Early Amphibians & Reptiles

• ribs developed in myosepta along entire length of the trunk • urodeles still have myosepta the length of the trunk (but ribs no longer form in all of them).

Subvertebral muscles

• underneath & against transverse processes of vertebrae • includes psoas & iliacus in the lumbar region and the longus colli in the neck • less developed in thorax & none in tail

Rectus muscles

• weakly developed in most fish: stronger in tetrapods • support ventral body wall & aid in back arching • in mammals, rectus abdominis extends from anterior end of sternum to pelvic girdle