Chapter 7 Muscular 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 muscle Portion 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 Controlled at will Nerves make them contract and extend Striated Microscopically have cross striated or stripped appearance SMOOTH Visceral Internal organs Involuntary Nonstriated CARDIAC Involuntary Striated

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 + smooth e.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 respiration Support 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 THORAX AID 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 ribs the internal intercostals lower the ribs the 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 oblique Transversus abdominis

Linea alba

Muscles of the hindlimb These 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