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Chapter 3
Objective: Describe the functions of the musculoskeletal system.
Introduction - The skeleton has 3 divisions
1. axial skeleton - bones that lie around the body’s center of gravity (skull, vertebrae,
hyoid apparatus, ribs, sternum
2. appendicular skeleton - bones of the limbs
3. visceral skeleton - bones that form in soft organs (os penis, os cordis, os rostra)
Bones have the following five functions:
1. form/structure - bones help define the shape and appearance of animals
2. protection - certain bones have critical roles in protection such as the skull and ribs
3. mineral storage - primary storage site for calcium and phosphorus
4. blood formation - marrow cavities of bones produce both red and white blood cells
5. leverage (mobility) - muscles work with bones to enable movement
Objective: Detail the structure of bone.
There are three types of bone cells:
1. Osteoblasts - cells that actively produce bone. They are destined to become...
2. Osteocytes - maintains bone matrix
3. Osteoclasts - cells that tear down bone so it can be rebuilt; active in formation of bone
marrow cavities and spaces
Types of bones: classified according to shape and structure
1. Long bones - longer than wide. Has central marrow cavity and distal and proximal
epiphysis. (Femur)
2. Short bones - long as they are wide. (carpals and tarsals)
3. Flat bones - two plates of compact bone with spongy bone between. No marrow
cavity. (pelvic bones, skull bones, ribs)
4. Irregular bones - odd shaped bones. (vertebrae)
5. Pneumatic bones - contain air spaces. (avian species)
Anatomy of bones: Define the following terms.
Articular Projections
headcondyletrochleaNon-Articular Projections
cavitiesnotchfacetfoveafossaforamencanalParts of the Long Bone
Diaphysis - the shaft of the bone (compact bone, central medullary canal, and spongy
bone at the proximal and distal ends)
epiphyses - proximal and distal ends of the bone (thin outer layer of compact bone with
centers of spongy bone)
metaphyses - regions in mature bone where diaphysis joins the epiphyses
Objective - List two major sections of skeleton, name the corresponding bones,
and outline species differentiation.
Axial Skeletal System
Cranium - combines numerous flat bones
Zygomatic Arch
Nuchal crest
Vertebral Column (feline)
Cervical - 7 vertebrae (c1 = atlas, c2 = axis)
Thoracic - 13 vertebrae
Lumbar - 7 vertebrae
Sacrum - 3 vertebrae; fused
Coccygeal (Caudal) - variable depending on breed
Ribs - head, neck, tubercle, shaft, costal cartilage
Sternum - xiphiod cartilage, xiphoid process
Appendicular Skeletal System
Collarbone; attaches to scapula in felines
Not articulated with other bones in canines/may be missing.
Large animals have only cartilage.
Shoulder blade; large triangular bone
Acromion process
long bone extending from shoulder to elbow
Head, greater and lesser tubercles, medial and lateral epicondyles, trochlea
Caudal long bone of forelimb.
Forms elbow joint by articulating with humerus.
Fused with radius in equines.
Trochlear notch, olecranon, lateral styloid process
Cranial long bone of forelimb.
Head, radial tuberosity, medial styloid process
Numerous irregularly shaped bones.
Human wrist = animal knee.
Articulate carpus with phalanges.
Numbered from medial to lateral.
Splint bones and cannon bone in equines.
Phalanges (digits)
Normally 3 phalanges in each digit.
Digits numbered from medial to lateral. (roman numerals)
Phalanges numbered from proximal to distal. (numbers)
Canine = 5 digits
Cloven hoof = two digits
Equine = 1 digit with 3 phalanges
Joint between cannon bone and first digit = fetlock
Phalanx 1 = pastern bone
Phalanx 2 = short pastern bone
Phalanx 3 = coffin bone
Three pairs of fused bones
Connects to the sacrum and coccygeal vertebrae
Supports caudal half of body
Attachment for hind limbs at hip joint
Ilium - largest pair; flares to side
Ischium - strongest and most caudal pair
Pubis - most ventral pair
Hip socket; articulates with end of femur
Proximal long bone of hind leg
Longest bone in the body
Head, neck, greater and lesser trochanter, medial and lateral condyle
Flat bone that glides over stifle joint
Kneecap in humans
Larger, more weight bearing bone of distal hind limb
medial and lateral condyles, medial malleolus
Long slender bone of lower hind limb
Does not articulate at distal end in some species (horses)
Head, shaft, lateral malleolus
Numerous irregularly shaped bones arranged in rows
Human ankle
Hock in animals
Articulate tarsals with phalanges
Phalanges (digits)
Same as forelimb
Objective - Name the joint types and the role in movement
arthrology - study of joints
Types of joints
1. fibrous - fixed joints that are brought together with dense connective tissue; skull
2. cartilage - bones that are connected directly with cartilage; growth plates
3. synovial - true joints; layer of bone covered with cartilage and enclosed in a capsule;
elbow joint
a. costochondral junction b. temporomandibular joint c. scapulohumeral joint d. humeroradioulnar joint e. carpal joint
f. fetlock joint (equines)g. pastern joint (equines)h. coffin joint (equines)i. sacroiliac joint j. coxofemoral jointk. femorotibial jointl. tarsal jointm. tibiotarsal jointdesmology - study of ligaments
a. nuchal ligamentb. cruciate ligamentsc. suspensory ligament-
Myology - study of muscles
allows movement in conjunction with bones
over 600 muscles in the body
help produce body heat
form some internal organs (heart)
Allied Muscular Structures
tendons - strong, fibrous white bands that attach muscles to bones
fascia - sheets of fibrous membrane that encloses muscles/separates groups
ligaments - strong bands of fibrous tissue connecting bone to bone
origin - fixed/less movable point of attachment to bone
insertion - movable point of attachment to bone
Muscle Composition
myofibers - cells of muscle tissue
sarcolemma - plasma membrane of a muscle cell
sarcoplasm - cytoplasm of muscle cell
skeletal - voluntary muscles that are striated (striped); tongue, biceps
smooth - involuntary muscles that are not striated; stomach, uterus
cardiac - heart muscle; involuntary and striated
abduction - movement away
adduction - movement towards
flexion - makes angle smaller
extension - makes angle larger
orbicularis oculi - move the eyelids
masseters - mastication; raise the mandible
Neck, Back, and Thorax
serratus - supports trunk
pectoral - forms chest; adducts forelimb
lattisimus dorsi - broadest back muscle; shoulder flexion
intercostals - rib muscles
diaphragm - separates chest/stomach cavity; allows lung expansion
triceps brachii - extends forelimb; caudal humerus
biceps brachii - forelimb flexion; cranial humerus
obliques - slanted muscles on abdominal side
abdominis - floor of abdomen
gluteal - limb extension and adduction; pelvis
quadriceps femoris - limb flexion and extension; cranial femur
semimembranosus/semitendinosus - posterior hind limb; injections
biceps femoris - posterior hind limb
arrector pili - muscles causing hair to stand on end
cutaneous trunci - dermal muscle causing insect repelling skin twitches
cremaster - part of spermatic cord; raises/lowers testicles in response to temp