The Skeletal System

Functions of the Skeletal System (6)

Support body & provide shape

Provide attachment and leverage for muscles

Protect internal organs - brain skull, heart lungs ribs

Site and protection for sensory organs

Store minerals - e.g. calcium and phosphorus

Produce new blood cells (haematopoiesis)

Condyle

Round protuberance (bulge/knob) at end of bone

Crest

Raised area of bone

Foramen

Hole/opening within bone

Fossa

Depression within bone where another structure is found

Groove

Depression in bone

Medullary Cavity

Centre of long bones, often containing bone marrow

Periosteum

Outer covering of bone

Process

Thin, elongated projection

Sinus

Narrow hollow cavity

Spine

Central part bone

Trochanter

Prominent area of femur that lies behind head of femur

Tubercle

Small elevation on surface of bone

Tuberosity

Area of tubercle where tendons attach

Bones are … , made of …

Connective tissue, matrix of collagen fibres, filled with cells to build and modify bone. Minerals e.g. Ca, P (hyrdroxyapatite), stored within matrix, presence gives bone hardness and rigidity

Osteoblast

Immature bone cell responsible for developments and repair of bone

Osteocyte

Mature bone cells, main function is bone maintenance

Able to divide and convert into osteoblasts when necessary

Osteoclast

Bone cell responsible for breakdown of bone matrix

Sections of bone

Epiphysis, Metaphysis and Diaphysis

Epiphysis

Ends of long bone. Develop separately, initially separated by cartilage from shaft

Metaphysis

Site allows growth of bone (growth plate), between epiphysis and diaphysis. Visible on xrays as cartilage (epiphyseal line), area becomes calcified once bone growth complete

Diaphysis

Central shaft of bone, contains medullary cavity

Periosteum

Tough, fibrous membrane covers bone and provide ligament and tendon attachment. Covers all bone except articulate surfaces

Articular cartilage

Hyaline cartilage covers bone area within joints, provide cushioning and shock-absorption

Nutrient foramen

Hole provides entry for blood supply, ensure oxygen and nutrients reach bone

Bone marrow

Spongy tissue, within medullary cavity (yellow marrow) and epiphyses (red marrow). Primary site of haematopoiesis (RBCs, WBCs, platelets)

Cortical (compact) bone

Dense, regular structure, high mineral content for strength

Outer surfaces, covered in periosteum membrane

Close arrangement of canals (haversian system).

Cells form in circular patterns (lamellae) around central canal (Haversian canal)

Contained within - blood, lymph and nerves supplying bone

Cancellous (spongy) bone

Less dense than compact,

Honeycomb pattern

Less strength, commonly ends of long bones/smaller bones e.g. vertebrae

Less structured network - Loose network of fibres - trabeculae

Production of blood cells (haemopoiesis) occur predominantly

Long bones

Cylindrical, longer than wide, describes shape not size

Small long bone - toe bone (phalanges)

Long bones contain outer cortex (cortical bone), medullary cavity in main shaft (diaphysis), and cancellous bone at ends (epiphyses)

Majority of appendicular skeleton (limbs) are long bones, function as levers against which muscles contract and create movement

Short Bones

Cube-shaped approximately equal length, width, thickness

One section, no medullary cavity, develop from one area of ossification

Provide stability and support, limited motion.

Typically found within carpus and tarsus

Sesamoid Bones

Small, round, seed

Form in tendons, great pressure generated.

Provide extra support to resist strong forces created when extending/flexing joint

Sesamoid bones vary in number/placement between species, typically involve patellae (sitting over stifle), and fabellae (sitting behind stifle)

Flat bones

Thin, curved, consist layer of cancellous bone within layer of compact, without medullary cavity

Flat bones serve as points of attachment for muscles, e.g. scapula or pelvis, specific protection of internal organs e.g. ribs or skull

Irregular bones

Complex shaped, e.g. vertebrae or provide specific structural features e.g. jaw or sinuses

Pneumatic bones

Medullary cavity in these bones largely replaced by air to reduce weight

Bones confined to skull and paranasal sinuses, which communicated with nasal cavities. e.g. sphenoid bone in skull

More significant in birds, most of skeleton pneumatic and connected to air sacs (avian respiratory system). Skeleton lighter, adapted for flight

Appendicular Skeleton Consists of

Forelimb, scapula, hindling, pelvis

(Scapula, clavicle (collar bone), humerus, radius ulna, carpus, metacarpals, phalanges, pelvis, femur, stifle, tibia and fibula, tarsus, metatarsus)

Forelimb

No bony connection to body

Attached by muscles

Shock absorber that use all 4 limbs, most weight bearing occur

Hindlimb

Bony attachment at pelvis

Limb provides attachment for powerful muscles used during running, jumping

Axial Skeleton

Bones of skull, vertebral column, ribs and sternum, hyoid apparatus and middle ear

Skull: mandible, skull cranium, hyoid apparatus, atlas axis, vertebral column, ribs, sternum, sacrum,

Vertebral Column and Intervertebral Discs:

Intervertebral disc: Central portion (nucleus pulposus) jelly-like material providing shock absorption, outer layer (anulus fibrosus) more fibrous to provide support and stability

Splanchnic skeleton

Develop in soft tissue remote from rest of skeleton

os penis/baculum

Dog skulls

Dolichocephalic, Mesocephalic, Brachycephalic

Greyhound, Labrador and pug

Bones within skull Lateral

Ventral skull

Rabbit skeletal system

Rabbit skeleton 6-7% BW, prone to fractures esp. spine and hindlimbs due to powerful musculature hindlimbs, kicking out

Rabbit skull

Mandible narrower than maxilla. Temperomandibular joint has wide SA allow lateral movement of mandible in relation to maxilla

Rabbit Axial skeleton

Cervical vertebrae box-like, small, great mobility.

Thoracic vertebrae possess attachment to 12 paired ribs

Pelvis narrow, positioned vertically, ilial wings meet ischium and pubic at acetabulum, accessory bone unique to rabits - os acetabuli

Pubis forms floor of pelvis and borders obturator foramen, oval in rabbits

Rabbit Appendicular skeleton

Ulna fuses to radius in older animals, two bones deeply bowed

Hindlimbs similar to cats, femur flatter and tibia, fibula fused

Calcaneous of tarsal bone prominent