Skeletal System

I. Ossification (os - bone, fic- to make)Dependent on a proper supply of Ca and P to the bone tissue

II. Types of bonesa. Cortical bone (compact bone)- hard, dense, strong bone that forms the outer layer of a bone.

b. Cancellous bone (spongy bone) - lighter, less strong bone that is found in the ends and inner portions of long bones

III. Bone classificationa. long bones - bones with a shaft, two ends, and a marrow cavity (femor, radius)b. short bones - cube-shaped bones with no marrow cavity (carpal, tarsal)c. flat bones - thin flat bones ( pelvis)d. pneumatic bones - sinus-containing bones (frontal bone)e. irregular bones - umpaired bones (vertebrae)f. sesamoid bones - small bones embedded in a tendon (patella)

IV. Bone formationa. diaphysis - middle region of a long bone; composed of compact bone

b. epiphysis - end of the long bones; composed of cancellous bone

c. epiphyseal line (growth plate) - cartilage tissue that is constantly being replaced in long bones

d. Periosteum -tough, fibrous tissue that forms the outer covering of the bone

e. Articular Surface - smooth layer of cartilage covering the epiphysis where one bone forms a joint with another bone

f. Medullary cavity - space in the diaphysis that contains the marrow

g. Cortex - compact bone surrounding the medullary cavity.

h. Red marrow - forms blood; in older animals it is only found in the ends of the long bones.

i. Yellow marrow - consists of adipose tissue.

V. Joints (Articulations)A. Simple Joint - involving two bonesB. Compound Joint - involving more than 2 bones (Stifle)C. Structural Classification

1. Fibrous joint (synarthroses) - united by fibrous tissue; allowing little or no movement; these are often temporary joints

2. Cartilaginous joint (amphiarthroses) - united by fibrocartilage; slightly moveable

3. Synovial joint (diarthroses- ball and socket joints) - united by synovial capsule; freely moveable joint.

VI. Structural Supporta. Bone process - enlarged tissue where muscles and tendons attach

1. Bone head - rounded end of a bone2. Tubercle -small, rounded surface for attachment of tends or muscles3. Tuberosity - projecting part for attachment of tendons or muscles4. Condyle - rounded projection that articulates with another bone5. Crest - high projection or border projection6. Process - projection7. Protuberance - projecting part8. Trochanter - broad, flat projection (femur)

b. Bone depression - openings or regions where one bone connects to another bone1. Fossa - trench or hollow depressed area2. Foramen - opening for blood vessels or nerves3. Fissure - narrow, deep, slit-like opening4. Sinus - cavity within a bone

VII. Skulla. frontal - forms the roof of the cranial cavity; where the horn processes come fromb. parietal - paired bones that form the roof the caudal cavity.c. Occipital condyles- forms the caudal aspect of the cranial cavity; opening for the

spinal cordd. Temporal - paired bones that form the sides and base of the craniume. Zygomatic arch - cheekbonef. maxilla - upper jawg. mandible - lower jawh. lacrimal fossa - tear ducti. mental foramen - j. orbit - socket for the eyek. external acoustic meatus - l. paracondylar process - m. mastoid process - n. nuchal crest - o. tympanic bulla - p. coronoid process -

Skull Shapes:1. Brachycephalic - short, wide heads with the “smashed in” face2. Dolichocephalic - dogs have narrow, long heads3. Mesocephalic - dogs have average width to their head

VIII. Vertebrae (spondyl)a. Cervical - neck

1. Atlas (C1)2. Axis (C2)

b. Thoracicc. Lumbard. Sacrume. Coccygealf. intervertebral disc - cartilage disc that cushions each vertebrae

IX. Ribs (costal)a. sternum - breastboneb. xiphoid process - caudal portion of the sternumc. clavicle (collarbone) - pigs, ruminants and horses do not have clavicles

X. Front Limba. Scapula - shoulder bladeb. Spine of the scapulac. Humerusd. Radiuse. Ulna f. Olecranon - elbowg. Carpals - wristh. Metacarpalsi. Phalanges - fingers/toesj. Sesamoid - small nodular bones embedded in a tendon or joint capsulek. Cannon (III metacarpal)l. Splintm. Long Pastern (P1)n. Short Pastern (P2)o. Coffin bone (P3)p. Navicular

XI. Hind limba. femurb. tibiac. fibulad. patella - kneee. Tarsal - anklef. Metatarsal - footg. Phalange - toes

h. Sesamoid - small nodular bones embedded in a tendon or joint capsulei. Cannon (III metacarpal)j. Splintk. Long Pastern (P1)l. Short Pastern (P2)m. Coffin bone (P3)n. Navicular

XII. Pelvisa. Iliumb. Acetabulum (hip joint)c. Ischiumd. Pubise. Pelvic symphysisf. Obturator foramen

XIII. Vocabularya. oste(o) - bone

1. Oste/itis - inflammation of the bone2. Osteo/dystrophy - inadequate formation of bone tissue3. Osteo/genesis - formation of bone tissue4. Osteo/myel/itis - inflammation of the bone and bone marrow. May result in

bone destruction if it spreads to the joints.b. chondr(o) - cartilage

1. Chondro/malacia - softening of the cartilage2. Chondro/placia - formation of cartilage

c. Orth - straightd. Physis - to growe. Porosis - passage

1. Osteo/porosis - bone breaking down by forming holes. Bones become weak due to loss of Ca.

f. bursa - capsule around the joint containing fluid1. Burs/itis - inflammation of the bursa sac

g. reduction - restoration of a fractured bone to its normal place or positionh. arthritis - inflammation of the jointsi. Dislocation -displacement of a bone from its jointj. Sprain - injury to ligaments; twisting of the joint with partial rupture of its ligaments.

XIV. Pathological Conditionsa. Osteogenic Sarcoma - malignant tumor from the bone. Common in dogs and cats but rare in other species. Large breeds more frequently affected. Lameness and swelling of the bone with rapid metastasis to the lungs.

b. Fracturea. Closed (Simple) - bone broken but does not create an open wound

b. Compound (open) - broken bone with open wound created by the bone sticking out. Complicated with infections

c. Comminuted - bone splintered or crushed. Common with gunshot wounds

d. Greenstick - bone is partially fx

e. Compression - broken bone produced when the bones are pressed together

f. Spiral - broken bone in which the bone is twisted apart or spiraled apart

g. Avulsion - broken bone in which the site of muscle, tendon, ligament insertion is detached by a forceful pull

h. Chip - caused by overextension at speed in horse

i. Slab - surface pieces are broken off. Seen in carpal bones

c. Ankylosing Spondylitis - progressive arthritis with stiffening joints in the vertebrae.(Ankylo - bent; spondylitis - vertebrae)

d. Navicular Disease - lameness in horses caused by the navicular bone turning or the sesamoid bone going over the bone

e. Ring bone - periosteal bone deposition on the phalanges. Occurring near the pastern or coffin joint

f. Hip Dysplacia - Lameness ; Mostly in large dogs. Common causes in dogs are1. Genetic2. Nutrition3. Fat baby

g. Splint - inflammation of the horse’s interossesous ligaments and build-up of bone between the splint and cannon bones

h. OCD(osteochondrosis dissecans) - 2nd most common hock problem; Fast growing cartilage .

i. Wobbler Syndrome - stenosis (narrowing) of cervical vertebrae. Common in Bassets, Borzois, Dobies, Great Danes, Throughbreds. Clinical signs develop slowly with weakness, ataxia.

j. Intervertebral Disk Disease - one or more intervertebral disc dengenerates. This usually is disk material being squeezed out and puts pressure on the spinal chord. Signs include pain, numbness, weakness, paralysis. Common in Dachshunds at the cervical junction. Treatment includes surgery and cage rest.