The Skeletal System Learning Objectives List the cell
The Skeletal System Learning Objectives
List the cell types that make up bone; describe the function of
each cell type. List the functions of bone and differentiate between cancellous and compact bone. Describe the process of endochondral bone formation and growth. Describe the process of intramembranous bone formation. List and describe the four shapes of bone. Differentiate between yellow and red bone marrow. List and define terms used to describe shape and surface features of bone. List the components of the axial and appendicular skeletons.
Name the bones of the thoracic and pelvic limbs; the internal and external bones of the face and cranium. List the divisions of the spinal column and describe the structure of the ribs and sternum. List and describe the three classification of joints. Bone Second hardest substance in the body
Composed of cells embedded in a matrix Matrix is made up of collagen fibers embedded in ground substance of protein and polysaccharides (gel-like) Cells are initially osteoblasts
Osteoblasts Make matrix Harden matrix ossification Osteocytes
Live in lacunae Nourishment for the cells and communication with each other is by canaliculi Osteoclasts Functions of Bone
Support Protection Leverage Storage Blood cell formation
Bone Structure Two types of bone Cancellous bone: light and spongy Compact bone: dense and heavy Cancellous Bone
Tiny "spicules" of bone that appear randomly arranged Spaces between the spicules
contain bone marrow Compact Bone Shafts of long bones and the outside layer of
all bones Composed of haversian systems that run lengthwise with the bone Haversian Systems Concentric
layers of ossified bone matrix arranged around a central canal Blood and lymph vessels and nerves Bone Structure
Periosteum: membrane that covers outer surfaces of bones Outer layer is composed of fibrous tissue Inner layer contains osteoblasts Not present on articular surfaces Bone Structure
Endosteum: membrane that lines the hollow interior surfaces of bones Also contains osteoblasts Bone Cells Osteoblasts: cells that produce bone
Harden matrix through ossification Once surrounded by bone, osteoblasts are called osteocytes Osteoclasts: remodel/remove bone
Blood Supply to Bone Volkmann canals: channels through bone matrix that contain blood vessels Blood vessels in the Volkmann canals join with blood vessels in the
haversian systems. Blood Supply to Bone Nutrient foramina: channels in many large bones Contain large blood vessels, lymph vessels, and nerves
Often mistaken for a possible fracture on radiographs Bone Formation Two possible mechanisms: 1. Endochondral bone formation Grows into and replaces cartilage
2. Intramembranous bone formation Develops from fibrous tissue membranes Endochondral Bone Formation Primary growth center: bones develop in the diaphyses
Cartilage rod Cartilage is removed as bone is created Secondary growth centers: develop
in the epiphyses of the bone Endochondral Bone Formation Epiphyseal plates: cartilage located between diaphysis and epiphyses of bone
Sites where new bone develops to allow long bones to lengthen Endochondral Bone Formation Osteoblasts replace cartilage with bone
on the diaphyseal surface of the plate. When the bone has reached its full size, the epiphyseal plates completely ossify. Intramembranous Bone Formation
Occurs in certain skull bones Bone forms in the fibrous tissue membranes that cover the brain in the developing fetus. Bone Shapes Four basic shapes: 1. Long
2. Short 3. Flat 4. Irregular Long Bone Longer than it is wide Femur
Humerus Short Bone Short, kind of block like Capal Tarsal
Flat Bone Flat and thin Pelvis Scapula Irregular
Vertebrae Sesamoid bone Imbedded in tendon (patella, fabella, navicular) Bone Marrow
Fills the spaces within bones Two types: 1. Red bone marrow 2. Yellow bone marrow. Red Bone Marrow
Forms blood cells Majority of the bone marrow of young animals Only a small portion of the marrow of older animals
Confined to a few specific locations in older animals Yellow Bone Marrow Consists primarily of adipose
connective tissue Most common type of marrow in adult animals Can revert to red bone marrow if needed Fractures Types of fractures
Healing 3 things needed for bone healing: Alignment Immobilization Time Alignment
Align the bones as close as possible reducing the fracture or reduction Immobilization Fixation of the fracture
Internal fixation Surgery under anesthesia Pins, screws, plates, wires External fixation Usually placed while under anesthesia Casts, splints, slings
External Fixation Thomas Splint Traction = maintains alignment, length of bone Traction need only be slight Distal foot should be secured to frame
Fractures of the Radius, Tibia Thomas Splint Construction of Thomas splint Ring should fit contour of the upper limb Footplate (frame) length of limb in traction Limb will have been bandaged (pressure bandage) Step 1: Form ring and footplate out of aluminum rod Step 2: Pad the ring
Thomas splint External Fixation Robert Jones Bandage Padded pressure bandage Provides immobilization because of compression of the thick cotton secondary layer Reduces post-operative swelling
Can use a metasplint or quicksplint for added immobilization Robert Jones Bandage Application of Robert Jones Bandage Apply anchor tapes (stirrups) Apply primary layer (contact w/ wound)
Place cotton between toes Apply secondary layer - cotton padding Apply tertiary gauze layer Reflect back, twist, and tape stirrups to gauze Apply protective tape layer, Vet Wrap Check padding (percuss) Check toes
Robert Jones Bandage https://www.youtube.com/watch?v=okfoKPc VN78 Time Small or young animals
Might take a couple weeks Large or older animals Might take a couple months or even several months Healing
Blood supply to bones = considerable bleeding at fracture site As blood clots = fracture hematoma Healing cells (osteoblasts) form healing tissue called a callus
Callus bridges the fracture gap Large callus-movement between fracture gaps Smaller callus is better. Bone remodeling returns bone to original shape and strength (osteoclasts) Open vs Closed, reduced
fracture Callus formation Femur: fracture w/ callus at 2 weeks Ouch! Bone Features Articular Surfaces:
1. Condyle: large, round articular surface 2. Head: spherical articular surface on the proximal end of a long bone Joins with the shaft of the bone at the neck region 3. Facet: flat articular surface Articular Surfaces
Smooth areas of compact bone that come in contact with smooth surfaces of another bone Forms a joint such as the stifle Articular surfaces are covered with hyaline cartilage
Condyle large, round articular surface Examples of where to find some condyles Occipital Bone-connects the head to the neck
Distal end of the Femur Distal end of the Humerus Condyle of the Canine Femur. These condyles meet the proximal end of the tibia to form the stifle joint
The Condyle of the Canine Humerus. These surfaces along with the proximal articular surfaces of the radius and ulna form the elbow joint Head Humerus mostly spherical in shape Femur
Proximal end of a long bone such as Femur and Humerus The head of the femur fits into a socket in the pelvis (the acetabulum) to form the hip joint. The head of the humerus joins the glenoid cavity of the scapula to form the shoulder
joint. The neck, which is just lateral to the head, is not as pronounced as in the femur. Proximal end of ribs Narrowed region that joins head to rest of bone is the neck Head of a Rib. The heads of the ribs articulate with the
thoracic vertebrae of the spinal column. Facet flat articular surface The heads of ribs articulate with these articular facets (lateral view).
Facet Articular Surfaces. Equine Carpus More Bone Features: Processes, Holes and Depressed areas Bone Features Processes
Projections off a bone surface Lumps and bumps Name depends on location Examples:
Spinous process of a vertebra Trochanter on the femur Tuberosity on the ischium Spine on the scapula Wing on the atlas Xiphoid process on caudal end of sternum
Lumps and Bumps - Process Tendons of muscles attach to bone The larger the process the larger, more powerful the muscle
Types of synovial joints Hinge joints Gliding joints Pivot joint
Ball and socket joint Hinge joint Elbow, stifle, digits Gliding joint Carpus, tarsus
Pivot Joint Atlantoaxial joint C1 and C2 Ball and Socket joint
Shoulder, hip Stifle joint anatomy Stifle joint: distal end of femur articulates with proximal end of tibia Hinge joint
Ligaments of the stifle joint Cruciate cross Anterior and posterior cruciate ligament Collateral ligaments lateral and medial
(sides) of the joint Miniscus-cushion between femur and tibia Patella tendon
Patella is suspended in large tendon Quadriceps muscle tendon (often mistakenly referred to as a ligament) Patella tendon connects from quadricep muscle of
femur to the tibia Patella covers the anterior cruciate ligament and posterior cruciate ligament Result of ACL injury
Very common injury in dogs Anterior cruciate ligament in the cranial ligament of the X formed by the two lagaments Miniscus can be affected Cartilage also will wear done (ultimately until bone on bone) How the ACL tear or rupture affects motion
Instablity of joint Normal movement between femur and tibia is hinges Without stability of ligament the two bones slide backward and forward
Chicken stifle: Leg quarters from Grocery store Movement of joints Flexion
Decrease angle between bones Extension Increase angle between bones Adduction
Movement of an extremity toward the median plane Abduction Movement of an extremity away from the median plane
Rotation Twisting/ rotating movement Circumduction
Movement of an extremity so that the distal end moves in a circle
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