Skeletal system Flashcards
Two types of skeletal systems
Axial, composed of the spine, head, and tail
Appendicular, all appendages
Dolichocephalic
long headed, ex. german shepard, collie,
Brachycephalic
Short wide skull, ex. pugs, boston terrier, boxer
Mesaticephalic
Moderate head, ex. beagles, terrier breads
Problems with brachycephalic breeds
defective teeth, difficulty breathing, shallow eye sockets, dystocia(difficult to give birth because of there large heads)
Spina bifida
Rare, a cleft or space in the dorsal part of the vertebral column
Hemi vertebrae
failure of the vertebrae body to ossify resulting in an improperly formed or shaped vertebrae
Different types of curvature of the spine and which way they curve?
Kyophis (Dorsal) Lordosis(ventral) Scoliosis( lateral)
os and oseo =bone
- Second hardest substance in the body (enamel is the hardest)
- Living, changing tissue
- Has the capacity for remodelling and repair in response to new stresses and _injury__
What is bone made of
Bone is made up of a few cells in a solid matrix
o Cells start out as osteoblast
o Produce a soft matrix made up of collagen fibers in ground substance
o Osteoblasts harden the matrix by adding crystalline calcium and phosphate salts in a process called ossification
Function of bone
Support, protection, leverage, storage, blood cell formation
Three main types of bone cells
Osteoclasts: cells that eat away or remove bone.
Osteoblasts: cells that form bone
Osteocytes: osteoblasts that have been trapped is ossified matrix
two types of bone
compact or cancellous
Compact bone
Dense, strong bone
Makes up the shaft of the long bones and the outer layer of the bones
Permeated by a microscopic framework of tunnels, channels, ad interconnecting networks, surrounded by a hard matrix
Bone is nourished and maintained through these tunnels
Function of bone: support
framework or scaffolding to support the animals and its organs
Function of bone:protection
surrounds ,supports, and protects delicate organs
Function of bone: Leverage
Levers to which the muscle attach allow animal to move its body
Function of bone: Storage
Particularly Calcium
Controlled by 2 hormones; Calcitonin(from the thyroid) that prevents the blood calcium level from going too high by placing calcium in bone and Parathyroid hormone(from the parathyroid glands) stops the blood calcium level from going too low bytaking calcium from bone
Function of bone: Blood cell formation
Site for hematopoiesis(production of blood cells)
Osteon or Haversian System
The functional and structural unit of compact bone
Contains one or two blood capillaries
Around each central haversian canal are concentric rings of matrix called lamellae (secreted by osteocytes)
There are small hollow cavities, called lacunae, between lamellae which contain the osteocytes
Osteocytes in the lacunae have many protoplasmic processes that extend outwards in a spider-like manner through a series of minute hollow tunnels called canaliculi
There is basically a continuous network of communicating canals (canaliculi) that join the central canal to the lacunae and adjacent lacunae to each other
Groups of osteons lie in a parallel arrangement.
Adjacent lamellae are separated with demarcation lines called cement lines
Perforating (Volkmann’s) canals penetrate the bone and connect the central (Haversian) canals of adjacent osteons
Cancellous bone
Lies adjacent to compact bone and is continuous with it.
No distinct line of demarcation between the two regions
Less organized histologically than compact bone
Primary feature is the trabeculae or spicules, which are a series of branching, overlapping plates of matrix
These plates are organized to produce large, interconnecting, cave like spaces which function in storage and as pockets to hold the
hematopoietic of the bone marrow
Spicules function to reduce the weight of the bone without compromising strength.
Arranged to provide support against the forces pulling on the bone
Spicules are randomly punctuated by lacunae (osteocyte-holding spaces) and blood vessels which provide lots of nourishment to nearby osteocytes
Bone shapes
Long, short, flat irregular
Long bones
Greater in one dimension than the other (i.e. Longer than wide)
Function as levers, support and sites for muscle attachment
Important for locomotion
Include most bones of the limbs
Parts of long bone
Epiphyses, diaphysis, epiphyseal, periosteum, endosteum, articular cartilage
Epiphyses
enlarged end of the long bone
Primarily made of cancellous/spongy bone
Diaphysis
Shaft of long bones
Primarily compact bone
Epiphyseal(growth) plate
Area between epiphyses and diaphysis
Layer of dividing cartillage still exists here in young growing bones allowing the bone to increase in length
Allows the bone to increase in length
When the animal has reached its full size the epiphyseal plate completely ossifies (turns to bone)
Until ossification these regions are the weakest
Periosteum
A tough, fibrous membrane which lines the outer surface of bone (except at the articular surfaces)
Adhreres tightly to the outer layer of compact bone
Anchored by bundles of collagen fibers that perforate and become embedded in the outer lamellae
Composed of outer layer of fibrous connective tissue and an inner osteogenic layer, which is a source of new born forming cells and provides access to blood vessels
Very important for: healing, growth in diameter of bone
Endosteum
Similar to the periosteum, but lines the inner surface of the bone
Also contains osteoblasts, is a source of new bone and assists in healing
Articular Cartilage
Smooth layer of hyaline cartilage covering the articular surface of the epiphysis
Reduces friction and wear in joints
Short bones
Cuboid shaped and contain no marrow cavity, just spongy bone in centre
Function – absorbs concussion or shock
Examples – tarsus, carpus
Flat bones
Thin and flat
Function- to protect vital organs and act as attachments for large muscle groups
Examples – ribs, scapula, pelvis, cranial bones
Irregular bones
Any bones that don’t fit into any of the above three categories
Sesamoid bones
Shaped like sesame seeds (hence the name)
Embedded in tendons and function to to reduce friction and/or change the course of a tendon
Example: patella (or knee cap) and fabellae (behind the stifle in dogs and cats)
Common bone features
Articular surface; condyles, head, facet, processes, foreman, and fossa
Condyles
Large and round
Seen mainly in the femeur, humorous and occipital bone of the skull
Head
Single spherical portion located at the __proximal epiphysis, femur and ribs_
Example: the ‘ball’ of the ‘ball and socket joints’
United with the shaft of the bone by a narrow region called the neck
Facet
Flat, allowing for rocking or twisting motion
Seen in carpal/tarsal bones, vertebrae and long bones such as the radius/ulna
Processes
- A general term that includes all bumps and projections on the bone
Processes that have a non-articulating function tend to have rough, irregular surfaces
Are usually the site of muscle or tendon attachmnet
Example: the spine of the scapula
As a rule of thumb, the larger the process the more powerful the muscular pull on that area of the bone
Processes go by many names such as:
Trochanter, at the femur
Tubercle, at the humerus
Spine, at the scapula
Even just “process”, such as in the spinous process of the vertebrae
Foramen
A hole in the bone through which nerve or blood vessels passes
Exception is the obturator foramen at the pelvis
Largest foramen of the body and exists to decresses the weight of the pelvic bone
Fossa
a depression or sunken area on the surface of a bone
muscles or tendons usually occupy this area
Blood supply
- Blood supply comes from blood vessels in __periosteum__
- Penetrate into bone through _volkmanns canals
__ * Connections between Volkmanns canals (right angles to long bones) and Haversian canals(parallel to long bones) allow nutrition of osteocytes - Nutrient foramina is a large channel through which __blood vessels_ and __nerves_ penetrate to feed the bone marrow (can appear as cracks or defects in the bone on radiograph!)
Bone marrow
Fills the space in the diaphysis of long bones and between spicules in cancellous bones, two types; Red and Yellow
Red Bone Marrow(RBM)
Hematopoietic tissue
Majority of bone marrow in young animals
Small part of older animals – primarily in ends of long bones and in the pelvic bones and sternum
Yellow Bone Marrow(YBM)
Primary adipose tissue_
Most common marrow in adults
Doesn’t produce blood cells, but can revert to red bone marrow if body needs more blood cells
Two types of bone formation
Endochondral and intramembranous
Endochondral bone formation
- bone grows into and replaces a cartilage framework
- Most bones in the body
Bones start as cartilage in the developing fetus - Start to ossify in the center of long bone shaft – the priamry growth center
- Epiphyses (ends) of the bone also ossify – the
Secondary growth center - During ossification, cartillage is removed and bone is deposited
- At birth and during first months of life, 2 parts of long bones remain cartilage – these are the plates where the epiphysis attach to the diaphysis on either end of the bone
- Called growth (or epiphyseal) plates
- As the animal grows, the body lays down cartilage on the epiphyseal side of the growth plates and osteoblasts ossify the diaphysial side
- When the animal reaches mature size, these cartilage plates ossify
Intramembranous bone formation
Bone develops from fibrous tissue membranes
Occurs in some of the skull bones
Fibrous tissue membranes cover the brain of the fetus
As it matures, these membranes are ossified
Form the cranium
Bone Homeostasis
Bones are constantly remodeling
Osteoclasts destroy bone (injured/damaged/allowing for remodeling)
Osteoblasts build bone
Control of mineral levels in the blood is regulated by hormones
Minerals important in Bone homeostasis
Calcium
Phosphate
Magnesium
Manganese
Copper
Vitamins important in Bone Homeostasis
Vitamin A+D
Important hormones in bone building
Parathyroid hormone
Calcitriol(vitamin D)
Calcitonin
Growth hormone
Insulin
Sex hormones
Gluccorticoids
Parathyroid hormone
▪ Increases blood calcium levels
▪ Stimulates the release of calcium from bone
▪ Inhibits calcium excretion by the kidneys
▪ Stimulates the absorption of calcium by the intestine.
Calcitirol (vitamin D)
▪ Increases blood calcium levels
▪ Inhibits calcium excretion by the kidneys
▪ Stimulates the absorption of calcium by the intestine
Calcitonin
▪ Decreases blood calcium levels
▪ Inhibits the release of calcium from bone
▪ Stimulates calcium excretion by the kidneys
Growth hormone
▪ Responsible for the general growth of all tissues of the body
▪ Stimulates the growth of epiphyseal cartilage
▪ Stimulates calcium excretion by kidneys
▪ Stimulates calcium absorption by the intestine
Sex hormone
(estrogens and testosterone)
▪ Cause the degeneration of cartilage in epiphyseal plates (stops longitudinal bone growth)
▪ Stimulate bone formation
▪ Estrogens prevent osteoporosis, possibly by direct effect on
osteoblasts
Insulin
Increases bone formation
Glucocorticoids
Decrease calcium absorption, blood calcium levels and weaken bones
Decrease blood calcium concentrations
Weakens bones
Cervical Vertebral Instability
o Affects mainly Dobermans, Great Danes and horses
o Results from a narrowing of the spinal canal in the cervical region
o Compresses the spinal cord
o Can be a result of malformation or misarticulating of the vertebra
oCause is a mixture of genetics, rapid growth and nutrition
o C/s – develop slowly and start with weakness and ataxia (in-coordination) * The term “wobbler’s syndrome” comes from the c/s of wobbly, uncoordinated gait
* Can appear drunk
* Can progress to complete paralysis
o Surgery often necessary with a guarded prognosis
Angular limb deformations in foal
o May be congenital or acquired in early neonatal life
o The carpus is most frequently affected
o Can be the distal radial physis (epiphyseal plate) or the tarsus
o Cause the distal portion of the limb to deviate either laterally or medially
Premature closure of the physis
o Most common in the radius and ulna
o Causes bowing of the limb which causes changes in the associated joints.
Joints
A joint is a union or junction of two or more bones
Arthro refers to joints
3 Basic joint types
Fibrous, Cartilaginous, and Synovial
Fibrous joints
- Bones are held together by fibrous tissue
- Virtually no movement
- Often ossify with age (fibrous only in the very young)
- E.g. Suture between skull bones
Cartilaginous Joints
- Bones are held together by cartilage
- Slight rocking or gliding movement
- E.g. Intervertebral disks, pelvic symphysis, mandibular symphysis
Synovial joints
- What we usually think of when we say joint
- Freely movable
- Made up of articular cartilage, the joint cavity, the joint capsule, and associated ligaments
Flexion
Decreases the angle b/w bones(bends)
Extension
Increases the angle b/w bones(straightens)
Adduction
Towards body
Abduction
Away from body
Circumduction
only the distal end of limb move in circle
Hinge joint
Moves only in the sagittal plane so only possible to flex and extend
Gliding joint
Also called arthrodial joint
Slight rocking movement
Main movement is flex and extend but some abduction and adduction is possible
Pivot joint
Trochoid joint
Only rotational movement is possible
Only place in animals this joint occurs is at the atlantoaxial joint
Ball and Socket
Permits movement in nearly all directions
Humeral or scapulohumeral
shoulder
Elbow
Cubital or humeroradioulnar
Hip
Coxal or coxofemoral
Patellar luxation may be due to
Hereditary in toy breeds
Shallow femoral trochlea
Medial luxation - may be intermediate: cranial cruciate may rupture in some cases, some develop secondary arthritis
Rupture of the cruciate ligaments of the stifle joint
o In dogs, usually the cranial cruciate
o Often accompanied by rupture of the medial collateral ligament
o Joint instability can be demonstrated by the “drawer sign” … The ability to slide the tibia cranial to the femur
Hip dysplasia
o Multifactorial disease
o Caused by combination of hereditary predisposition, injury as a puppy (splay-leg falls), obesity or too-rapid growth as a pup
o Acetabulum is shallow and femoral head moves excessively in the joint
o Causes osteophytes, flattening of the femoral head, and osteoarthritis
o Prevention: selective breeding, don’t over-feed large breed puppies, avoid slippery floors and excessive stairs for developing puppies
o Treatment: NSAIDs, femoral head osteotomy, hip replacement,
Aseptic necrosis (or Legg-Calve- Perthes disease)
o Spontaneous necrosis of the femoral head
o Unknown cause
o Affects young, small breeds of dogs
o Very painful
Humeroradioulnar joint (cubital or elbow joint) dysplasia
o Several types:
o OCD
o Ununited anconeal process
* Failure of ossification centre of anconeal process to fuse with
proximal ulna at 6 months of age
* Hereditary in large and giant breed dogs
* Joint is unstable and osteoarthritis can develop
* Treatment - surgical removal of fragments
Osteochondrosis(itis) dessecans (OCD)
o Problem in bone underlying articular cartilage
o Articular cartilage becomes abnormally thickened and can separate o Results in a partially attached ‘saucer-shaped’ flap which is prevented from reattaching and healing by joint movement
o This flap is often torn loose to float freely in the joint (joint mouse) o Flap can grow due to nourishment supplied by the synovial fluid
o Cause is unknown but hereditary is a probable factor, so affected animals should not be bred
o Most commonly affected joint is the shoulder but may also affect the elbow, stifle and hock
o Affects giant and large breed dogs at 4 to 8 months of age as well as horses
o Treatment - surgical and/or rest
Intervertebral disc disease
- Degeneration of one or more intervertebral discs
- Causes either bulging of the fibrous disc covering or complete rupture of the contents
- Presses against the spinal cord dorsal to the disc
- Primarily occurs in the neck or thoracolumbar areas
- Common in chondrodysplastic (short legged) dogs (e.g. Dachshunds) * Causes pain, paresis, paralysis, numbness
- May require surgery, but minor problems often improve with cage rest
Subluxation
o Partial dislocation
o Usually traumatic
Luxation
o One or more segments of the joint are out of place
o Nearly always traumatic with stretching or tearing of ligaments
o Severe - joint capsule may also be torn
o Can also have a conformational or developmental component
Classification of arthritis
o Acute - usually due to trauma or infection and involving only 1 joint, which becomes hot, swollen and painful
* E.g. “popped knees” or traumatic carpitis - an inflammation of
the carpus in horses
o Chronic – most commonly a degenerative osteoarthritis
* The most common type of arthritis
* Usually in older animals as a result of poor conformation,
previous trauma or chronic repeated stress. Called degenerative
joint disease.
Causes of arthritis
Trauma
* Immune mediated
* Infectious
Simple fracture
Skin is intact over the fracture site
Compound fracture
o When the external wound contacts the bone at the point of fracture
o Either the bone protrudes or the external wound intrudes
o Examples - bullet wounds, fan injuries, bite wound fractures
Comminuted fracture
several pieces (3+)
Epiphyseal
- also called ‘growth plate’ fractures
o At the epiphyseal plate
o Young animals
Incomplete fracture
- “greenstick”
o Bone bends and tears partially. Seen in young animals with more fibres and trabeculae in their bone.
Fracture healing
- Must reduce a fracture to reasonably close alignment
- Need to ‘fix’ or immobilize against movement
- Fracture hematoma forms ➔ osteoblasts invade area and start form in a callus ➔ calcium salts are deposited to mineralize the callus ➔ initial healing complete ➔ months to years of remodeling to restore strength and strength.
Articulate cartilage
o Covers the ends of the bones and is extremely smooth and cushioning
o Purpose is to reduce friction
Joint cavity or joint space
o A space within the joint which contains a small amount of synovial fluid
Joint capsule
o Consists of 2 layers:
▪ The outer layer is a
fibrous tissue membrane
▪ The inner layer, called the synovial membrane, produces synovial fluid
▪ Synovial fluid is normally transparent and serves to nourish and lubricate the joint
Ligaments
o Ligaments join bone to bone
o Can be within the joint capsule (intracapsular), or outside the capsule or forming part of the joint capsule (extracapsular)
Meniscus
o A cartilaginous pad or cushion found in the stifle or knee joint and in the
mandibular joint
