Myology 1 & 2

latin term for musculus?

little mouse

The piriformis muscle is associated with which gluteal muscle?

middle gluteal

explain the musculus origin:

Shape and movement of some muscles (biceps) thought to resemble mice

Generation of body heat

shivering

Storage is paired with:

glycogen

list the muscle functions:

Movement of the body

• Maintenance of posture and body position

• Movement of substances inside the body

• Generation of body heat

• Storage

• Provide support

list the muscle types:

smooth, cardiac, skeletal

smooth muscle characteristics

aka - visceral, unstriated, or involuntary muscle

• no striations

• Specialized for slow and steady contractions

• Muscle cells are spindle shaped, mono-nucleated

• innervated GVE neurons of ANS

smooth muscle locations

Hair follicles of skin, walls of hollow organs, walls of blood vessels, capsule of spleen, eyeball

cardiac muscle characteristics

make up the bulk of the heart

• branched cells

• central nuclei

• joined by intercalated discs

• striations

• innervated by GVE neurons of ANS

characteristics of skm

40% of body weight, most attached to bones

• striated, voluntary, or somatic

• long, cylindrical, multinucleated (peripherally) arranged into bundles with c.t envelopes

• innervated by GSE nerves

skm organization

enclosed in epimysium

• epimysium- is continuous with fascia and the tendon binds muscle to bone

• perimysium- wraps several fascicles in thin CT layer

• endomysium- individual muscle fiber (cells) in fascicles that are surrounded by delicate c.t layer

skm unit organization

each muscle fiber is made of myofibrils

• within myofibrils there are myosin + actin filaments organized in sarcomeres

• sarcomeres separated by z discs

tendon

attach muscles to bone with CT

APONEUROSES

Flat sheets of densely arranged collagen fibers

• used to denote any connective tissue sheet

• apo- edge ; neuron= tendon?

where do muscles attach directly to?

the fleshy periosteum

• ex. the attachment of the serratus ventralis m. to the serrated face of the scapula

other CT attachments

fascia

• thin sheath of CT layer enclosing muscle or other organs

Superficial fascia

site for fat storage, closely associated with skin, often contains cutaneous muscles

deep fascia

• fascial compartments: Covers and separates muscles enclosing them in a ‘fascial envelope or sleeve’

• consisting of mostly collagen fibers

• Fibers oriented in the same direction as tension and stress forces acting on the muscle

• serve as origin or attachment sites

clinical use of deep fascia:

holds sutures well, allows for bloodless separation of muscle

• cons- direct drainage of fluids or spread of infections + inflammation/swelling of muscle or tendon affects other structures

what are the regional thickenings in deep fascia?

retinacula (retinaculum) and annular ligaments (ring shaped)

Retinacula

aka retinaculum- that which holds or binds; band

• ex. flexor retinaculum + extensor retinaculum

tendon structure

similar to skm

• largely composed of collagen fibers

• subfascicle- primary bundle; collagen fibers form

secondary bundles of fascicles

group of primary bundles in tendon

• tertiary bundle- group of secondary bundles

• tendon- group of tertiary bundles

CT layers of tendons

endotenon- surrounding individual tendon fibers

epitenon- surrounds the entire tendon with CT sheath

paratenon- epitenon surrounded by a loose areolar CT layer

tendon protection

tensile strength

• can be damaged by excessive pressure or friction; when they change direction over bony prominences or hard tissues

places that provide tendon protection

synovial bursae, tendon sheath, sesamoid bones

Synovial bursae

bursa is a flattened sac containing synovial fluid to facilitate the gliding of a tendon over bone

types of synovial bursae

congenital bursa- present at birth (ex. Calcanean bursa)

induced bursa- develop SQ due to chronic outside pressure

burtitis

inflammation of bursa

tendon sheath

develop as an elongated bursa applied to one surface of a tendon

visceral layer (synovial sheath)

where the tendon sinks into the synovial bursa and is surrounded by it

different forms of tendon sheaths

parietal layer, mesotendons, visceral layer (synovial sheath)

parietal layer

External layer connected to the neighboring CT or periosteum

mesotendons

elongated mesentery that connects visceral and parietal layers

• provide vascular and sensory nerve supply to tendon

Synovial Structures on the Thoracic Limb

Intertubercular (bicipital) bursa- not a true bursa/tendon sheath but extension of the shoulder joint capsule

define a muscle origin:

denotes the more fixed point of muscle attachment

define a muscle insertion:

denotes the more movable point of muscle attachment

• insertion moves with the contraction

• insertion of a muscle is always considered to be distal to the origin

hypertrophy

enlargement of the muscle fibers (increase in contractile proteins) resulting in increase in total mass of a muscle

Atrophy

decrease in size or shrinking of muscle fibers (loss of contractile proteins) and thus the muscle

• disuse atrophy

• neurogenic atrophy (denervation)

Extrinsic muscles

Muscles that attach the limb to the body/trunk

• ex. trapezius

Intrinsic muscles

Muscles that are on the limb

• deltoideus

muscle actions

when a muscle or its tendon crosses a joint and the muscle contracts, it causes movement

• flexion and extension

agonist

prime mover

• any muscle capable of producing a designated action on a joint

Antagonist

any muscle that has the opposite action on that joint

agonist for extension of elbow joint

ex. triceps brachii m.

agonist for flexion of the elbow joint

ex. biceps brachii + brachialis m.

Triceps brachii m. agonist vs antagonist:

agonist for elbow joint extension BUT an antagonist to elbow joint flexion

Biceps brachii & brachialis m. agonist vs antagonist:

Both agonists for elbow joint flexion BUT antagonists to elbow joint extension

Fixators

any muscle that stabilizes the origin of the agonist and the joint that the origin spans

Synergists

muscles that work together to create a movement

Strap-like

fibers run parallel to the long axis and throughout the length of the muscle

• ex. gracilis and biceps femoris m.

Spindle-shaped

2 headed muscles- biceps (one in dogs)

3 headed muscles- triceps (4 in dogs)

2 bellied muscles- digastricus

Pennate muscles

Possess tendons throughout their length

• unipennate- muscle with tendon

• bipennate- muscle with a tendon on each side

• multipennate- muscle with tendons distributed throughout its volume

ex of bipennate:

Infraspinatus m.

ex of multipennate:

Humeral head of DDF

ex of Unipennate:

Ulnar and radial head of DDF (deep digital flexor)

sphincter

ex of external + sphincter muscle shape (circular); anus

6 pack muscle is ex of what muscle shape/form?

wide muscle with tendinous tissue

• rectus abdominus

rectus refers to what?

anything straight

ex of circular m.:

orbicularis orbis + orbicularis oculi

what muscle is in the category of wide muscle with aponeuroses?

serratus dorsalis

• EAO- external abdominal oblique

• IAO- internal abdominal oblique

define motor unit

One motor neuron and all the muscle fibers it innervates

• stimulated to contract by action potentials produced in alpha lower motor neurons

motor unit innervation:

Every muscle fiber (cell) is innervated by a LMN nerve cell, originating in the CNS

• single neuron branches to innervate more than one muscle fiber

explain contraction

Contraction of a muscle fiber is an all or none event

• Force of contraction determined by the number and size

  of motor units activated

sizes of motor units:

• Small motor unit : a single neuron innervating a few muscle fibers

• Large motor units : a single neuron innervating several hundred muscle fibers

Order of activation or recruitment of motor units is from small to large

muscle spindles

provide feedback on muscle length

• protective function

golgi tendon organs

provide feedback on muscle tension

• protective function

patellar reflex

Tapping on the patellar ligament results in stretching at musculotendinous junction

• stimulates muscle spindle

• reflexive contraction

muscle groups on the limb

• Grouped based on their location and action

• Often the origins or insertions within a group are

  very similar

• Muscles in a group are often innervated by the

  same nerve

ex of location and action grouped muscles:

cranial and lateral muscles of the forearm

• extensors of carpal joints or carpal and digital joints

ex of muscles grouped by origins or insertion

extensors all originate from lateral epicondylar region of the humerus

ex of muscles grouped due to innervation by the same nerve

all innervated by the radial nerve

Caudal muscles of the brachium

extensors of the elbow joint ; all insert on the olecranon

• tensor fasciae antebrachii(11), triceps

  brachii(6,6”,6”), anconeus mm

Cranial muscles of the brachium

flexors of the elbow joint ; both insert on the radial and ulnar tuberosities

• biceps brachii(12), brachialis(8) mm.

Craniolateral forearm muscles

extensors ; carpal and digit joints ; all originate from the lateral epicondylar region of the humerus

• extensor carpi radialis, common & lateral digital extensors, abductor digiti I longus

Caudomedial forearm muscles

flexors ; carpal and digital jts ; originate from the medial epicondyle of the humerus

• flexor carpi radialis/ulnaris,

  superficial & deep digital flexors

Lateral muscles of the rump

hip ; includes all gluteal muscles & tensor fascia latae m.

Caudal muscles of the hip

stabilizers

• counter the rotation caused by the gluteals during hip joint extension

caudal muscles of the thigh

all originate from the ischiatic tuberosity ; hamstring

• extend the hip variable action on the genual joint

cranial muscles of the thigh

flex the hip and extend the genual joint

• Quadriceps femoris m. and iliopsoas

medial muscles of the thigh

Most are adductors of the limb

craniolateral muscles of the crus

flex tarsal joints and extend digital joints

Caudal muscles of the crus

extend tarsal joints and flex digital joints

what are muscles named based on?

direction of fibers

size & shape

muscle action

#of origins

location

origin and insertion

define direction

orientation of muscle fascicles relative to the body’s midline

• rectus - parallel to rectus - rectus abdominis

• transverse - perpendicular to midline - Transversus abdominis

• oblique - diagonal to midline - external abdominal oblique

size greek abbreviations (brevis-, latissimus, longissimus, magnus, vastus, longus)

longus = long

brevis = short

latissimus = widest

longissimus = longest

magnus = large

vastus = huge

match the shape greek root meanings

Sphincter ; Tensor

Decreases size of an opening ; Makes body part rigid

define location

structure near which a muscle is found

• temporalis, muscle near temporal bone

orgin and insertion for Sternocleidomastoid

originating on sternum and clavicle and inserting on mastoid process of temporal bone