Chapter 3 Part 3 - The Skeletal System

The Appendicular Skeleton is Composed of
pectoral (fore) limbs
pelvic (hind) limb
shoulder and pelvic girdles
Pectoral Limb
no bony connection to the trunk, only attached by muscles
The Bones of the Forelimb are:
radius and ulna
absent in dogs, sheep, horses, cows, pigs
present in cats
shoulder blade
long bone forming the upper formlimb
composed of 7 short bones
carpal bones - two rows
8 bones - cow, sheep, horses, pigs
composed of five small long bones (metacarpal bones) - dogs/cats
2nd and 5th gone on cow
5th gone on horse
3rd and 4th fused on cow
one large metacarpal - cannon bone
two small metacarpal bones - splint bones
composed of the phalanges - long bones
each digit has three phalanges, except digit 1, the dew claw, which has only two
Sesamoid Bones
pairs of small sesamoid bones
proximal sesamoid bones - junction of the metacarpal and proximal phalanx
distal sesamoid bone - junction of the middle and distal phalanges
Horse - navicular bone
Bone of Hindlimb: Pelvis
how the hindlimb connects to the body
it consists of two hip bones or ossa coxarum which are joined together at the pubic symphysis
Pelvis Articulates With
the sacrum at the sacroiliac joint
Each Hip Bone Consists of:
3 bones
frouped around the acetabulum (socket of the hip joint)
long bone - forms the thigh
proximal femur head - articulates with the acetabulum
Tibia and Fibula
long bones - forms the lower leg
lie parallel to eachother
Tibia (more medial) - much larger of the two
Tibia articulates with the femur
seven short bones (tarsal bones)
three rows
two bones - proximal row (talus and calcaneus [ankle])
calcaneus (fibular tarsal bone) - has a large caudal projection - tuber calcis which forms the 'point' of the hock
four metatarsal bones
some dog breeds - may lack the first digit (dew claw)
digits - called phalanges
Joints or Arthrosis
when one bone connects to another they form an articulation
the study of articulations between bones (joints)
Joints Allow:
variable degrees of movement and are categorized into three groups:
fibrous joints
cartilaginous joints
synovial joints (knee)
Fibrous Joints
immovable joints
bones that form them are united by dense fibrous connective tissue (skull - sutures)
fibrous joints are also classed as synarthroses (joint that permits little or no movement)
Sutures also Associated with
the teeth - where join to bony socket of jaw
Cartilaginous Joints
allow limited movement or no movement
United by cartilage
Synarthroses joints
ex. pubis symphsysis - connects the two hip bones
mandibular symphysis - joining the two halves of the mandible
Amphiarthroses Joints
allow some degree of movement between the bones
ex. between the vertebrae (limited flexibility)
between fibs and sternum
Synovial Joints or Diarthroses
allow a wide range of movement
Joint Cavity
the bones are seperated by a space filled with synovial fluid
a joint capsule surrounds the whole joint
Synovial Joints outer layer
consists of fibrous tissue that serves as protection
Synovial Joints cavity
is lined by the synovial membrane - secretes synovial fluid
lubriates the joints
provide nutrition for the hyaline articular cartilage
Some Synovial Joints Can Have Additional Stabilization
from ligaments within the fibers of the joint capsule (either side of joint - collateral ligaments)
Some Synovial Joints Can Have Stabilizing Ligaments
attached to the articulating bones within the joint (intracapsular ligaments)
cruciate ligaments within the stifle joint
Some Synovial Joints Can Possess One or More
intra-articular fibrocartilaginous discs or menisci within the joint cavity
1. increase the range of movement
2. act as 'shock absorbers' - reducing wear and tear
3. ex. stifle joints - two crescent shaped menisci