Chapter 7Muscular system

VTHT 1205

ROOTS

• ARTHR/O- JOINT (arthroscopy)

• CERVIC/O- NECK (cervicoplasty)

• CHONDR/I, CHONDR/O, CHONDR/IO- CARTILAGE (chondromalacia)

• COST/O- RIB (intercostals muscles)

• GNATH/O- JAW (brachygnathous)

• MYEL/O- BONE MARROW OR SPINAL CORD (myelocyte, myelogram)

• THORAC/O- CHEST(thoracocentesis)

ROOTS

• MY/O- MUSCLE (myositis)

• OCCIPIT/O- BACK OF HEAD (occipitoatlanto)

• OSS/EO, OSS/I, OST/E, OST/EO- BONE (osteotome)

• SACR/O- SACRUM (sacroiliac joint)

• SPONDYL/O- VERTEBRA (spondylosis)

• STERN/O- STERUM (sternotomy)

• STETH/O- CHEST (stethoscope)

• TEND/O, TEN/O- TENDON (tendonectomy)

Introduction

• My/o/logy: Study of muscles

• Functions– Movement: contract and extend muscles– Posture: Support and maintenance– Producing body heat– Form: heart, uterus, lungs and intestines

• Always working

Tendon : attaches muscle to bone

• Tendons– Strong FIBROUS white

bands

– Attaches muscle to bone

• Ligaments– Bone to bone

Tendon

• Aponeurosis– Broad flat connective

tissue

– Attaches muscle > bone OR muscle > muscle

– “Flat and ribbon like”

Tendon Sheath

• CT around tendon when there is a long distance to attachment or when tendon pulls over a joint

Fascia : Sheet of fibrous tissue that encloses muscles and separates them into groups

Ligament : attaches bone to bone or bone to cartilage

• Strong bands of fibrous tissue

• Help/hinder movement and support organs

Origin - Insertion

• Origin : the less movable of the two points of attachment

• Insertion : the point of attachment by a musclePortion that moves during contraction

Muscles

• Muscles may attach directly to cartilage, joints, skin, mucous membrane, or fascia of other muscles

Muscle cells

• Motor or neuromotor unit: nerve cell + group of muscle cells

• Causes muscle to move by stimulating a group of muscle fibers

circumduction

• FLEXION – bending at a joint• EXTENSION – straightening at a

joint• ABDUCTION – moving a body

part away from the body• ADDUCTION – moving a body

part toward the body• ROTATION – turning a body part

on its axis• CIRCUMDUCTION – circular

movement

Composition of muscle

• Long slender cells called MYOFIBERS– Larger than other body cells

• Plasma membrane: sarcolemma

• Cytoplasma: sacroplasma

• Fascia: Encloses fibers which are held together by CT

• Within myofibers there are multiple myofibrils

Composition of muscle

• Very vascular

• Move when fibers contract

• Speed: varies with type muscle and size of body part to be moved– Smaller structures move faster e.g. eye

• Movement carried out by group of muscles

• Exercise increase fiber thickness, does not produce NEW fibers

Muscle Classification

SKELETAL

• Voluntary

• Striated

• Usually attached to skeleton

– Striated muscle not attached to skeleton: eyes, tongue, pharynx, skin muscles, heart

• Contract: muscle becomes short and thick

• CNS and PNS

SMOOTH• Visceral• Not striated

– Spindle shaped fibers

• Involuntary– Not controllable at will

• Stomach, intestine, uterus, blood vessel, eye-iris– Some influenced by

hormones

Some organs = skeletal + smoothe.g. esophagus ruminants: regurgitate and chew cud

bladder

uterus

Smooth muscle vs skeletal muscle

CARDIAC

• Striated• Involuntary

– Unlike other involuntary muscle

– Fine transverse striations

• ANS

cardiac

striated

smooth

Muscle attachments

• Muscle > tendon > phalanges: movement and reduction of bulk

• Voluntary m. – bone – Except larynx and thorax: muscle is attached to

thorax

• Attached to skin (cheek), mucous membrane (tongue)

• Attached to fascia of other muscles

A muscle must depend on other muscles to assist in a desired movement. For this reason

muscles are called prime movers, antagonists and synergysts.

Primer Movers

Muscles that actively produce a movement

Antagonist

Muscles that are in opposition to the prime movers

Synergist

Muscles that contract simultaneously with the prime

mover to help execute a movement or steady a part

The names of muscles are based on six points of identification* named for their action* named for their origin and insertion* named for their location* named for their shape or use* named for the direction of their fibers* named according to the number of their sections

• ORBICULARIS OCULI (C)– moves the eyelids

• MASSETERS (M) – muscles of mastication that raise the mandible to close the jaw

FACIAL MUSCLES

Serratus muscle group

Assist in respirationSupport trunk of the body

MUSCLES OF NECK, BACK, AND THORAX

• PECTORALS (7) – forms chest, adducts forelimb

• LATISSIMUS DORSI (2) – broadest muscle in the back. Provides support for the forelimb and aids in flexion of the shoulder

EPAXIAL MUSCLES IN BACK

EXTEND THE THORAX AND PRODUCE LATERAL MOVEMENT OF THE TRUNK

-ILIOCOSTALIS

-LONGISSIMUS

-TRANSVERSOSPINALIS

MUSCLES OF THORAXAID IN RESPIRATION, ALLOW THE THORAX TO

ENLARGE AND THE LUNGS TO EXPAND

- INTERCOSTALS (external

and internal):respiratory

muscles that are located

between the ribs

– DIAPHRAGM – wall that

separates the abdominal

and thoracic cavities

During respiration: the external intercostals lift the

ribsthe internal intercostals lower the

ribsthe diaphragm contracts and

flattens out causing the thorax to enlarge and the lungs to expand

MUSCLES OF FORELIMBS

• BICEPS BRACHII – flex the distal forelimb

• TRICEPS BRACHII – extend the distal forelimb

ABDOMINAL MUSCLES

KEEP VISCERA IN PLACE, SUPPORT AND COMPRESS THE ABDOMEN,

CONTRACT (DURING PARTURITION, DEFECATION, URINATION, COUGHING), ROTATE THE

VERTEBRAL COLUMN

                                                 

                                                                       

tricep

                                                 

                                                                       

bicep

ABDOMINAL MUSCLES• EXTERNAL OBLIQUE • INTERNAL OBLIQUE• RECTUS ABDOMINUS• TRANSVERSUS ABDOMINUS

• LINEA ALBA – fibrous band of connective tissue that is the center of attachment of the abdominal muscles on the ventral abdominal wall. Landmark for Sx.

                                                 

                                                                       

Rectus abdominis

External oblique

Internal obliqueTransversus abdominis

Linea alba

Muscles of the hindlimbThese muscles have several

functions in movement. The most important muscle groups include

*gluteal group*quadricep group

*semi group

MUSCLES OF THE HINDLIMB• GLUTEALS – located over the pelvis, extend and abduct

the limb

• QUADRICEPS FEMORIS – extend the hind leg

– Rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

MUSCLES OF THE HINDLIMB

• GROUP THAT IS LOCATED ON THE POSTERIOR ASPECT OF THE LIMB. FORMS THE HAMSTRINGS AND FLEXES THE HIND LEG

- SEMIMEMBRANOSUS– SEMITENDINOSUS– BICEPS FEMORIS

MUSCLES OF THE HINDLIMB

• GASTROCNEMIUS– Flexes the leg and foot

- Forms the Achilles Tendon

Miscellaneous muscles:arrector pili

These are smooth muscles attached to hair on the dorsum. When stimulated these muscles

raise the hair on the back.

Cutaneous trunci: a muscle that attaches to the dermis and controls the insect twich in large animals

Another large animal muscle is the cremaster, this muscle is part of the spermatic cord and attaches to the

scrotum. This muscle contracts and relaxes, raising and lowering the testicles. This movement helps to regulate testicular

temperature