The Skeletal system Flashcards
Bone
- 2nd hardest substance in the body
- Composed of cells embedded in the matrix
- Matrix is made up of collagen fibres embedded in protein and polysaccharides
- Bone is primarily made up of calcium and phosphate
Function of bone
- Support
- Protection
- Leverage
- Storage
- Blood cell formation
Types of bone
1) Cancellous bone
- Light and spongy
- Tiny ‘spicules’ of bone that appear randomly arranged
- Spaces between the spicules contain bone marrow
2) Compact bone
- Dense and heavy
- Shafts of long bones and the outside layer of all bones
- Composed of Haversian systems that run lengthwise with the bone
Haversian canals
- Concentric layers of ossified bone matrix arranged around a central canal
- Blood and lymph vessels and nerves
Blood supply to bone
- Volkmann canals - channels through bone matrix that contain blood vessels - connect Haversian canals to periosteum
- Blood vessels in the Volkmann canals join with blood vessels in the Haversian systems
- Nutrient foramina - channels in many large bones - contain large blood vessels, 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
- Endosteum - membrane that lines the hollow interior surfaces of bones (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
Types of bone marrow
1) Red bone marrow
- Forms red blood cells
- Majority of the bone marrow of young animals
- Only a small amount of the marrow in older animals
- Confined to a few specific locations in older animals
2) Yellow bone marrow
- Consists primarily of adipose connective tissue (fat)
- Most common type of marrow in adult animals
- Can revert to red bone marrow if needed
Bone shapes
- Long
- Short
- Flat
- Irregular
Bone features
- Articular (joint surfaces
- Condyle - large, round articular surface
- Head - spherical articular surface on the proximal end of a long bone - joins with the shaft of the bone at the neck region
- Facet - flat articular surface
- Humeral condyles are a common site of fracture in dogs - specifically in spaniels
- Foramen - hole in a bone; may contain blood vessels, nerves
- Fossa - depressed area on the surface of a bone
Axial skeleton - Skull
- Maxilla refers to the upper jaw
- Most of the skull bones are joints called sutures
- The mandible (lower jaw) is connected to the rest of the skull by a synovial joint
Axial skeleton - Hyoid bone
- Sometimes included with the cranial bones
- Also called the hyoid apparatus
- Composed of several portions of bone untied by cartilage
- Supports the larynx and ‘voice box’
Axial skeleton - Vertebrae
- Consists of a body, an arch and processes
- Intervertebral discs - cartilage separating bodies of adjacent vertebrae
Vertebral regions: - Cervical vertebrae (atlas, axis)
- Thoracic vertebrae
- Lumbar vertebrae
- Sacral vertebrae
- Coccygeal vertebrae
Axial skeleton - Ribs
- Flat bones that form lateral walls of the thorax
- Dorsa; heads of the ribs articulate with thoracic vertebrae
- Costochrondral junction: area where costal cartilage meets bony rib
- Costal cartilage joins the sternum or the costal cartilage ahead of them
- The last rib is classed as a floating rib - these do not join at the sternum
Axial skeleton - Sternum
- The breastbone
- Forms the floor of the thorax
- Composed of sternabrae
- Manibrium sterni - most cranial sternebra
- Xiphoid process (xiphisternum) - most caudal sternebra
Appendicular skeleton - Scapula
- Flat, triangular bone
- Forms portion of the shoulder joint
- Spine of the scapula - longitudinal ridge on lateral surface
- Glenoid cavity - shallow, concave articular surface
Appendicular skeleton - Clavicle
- The collarbone
- This is free floating in cats and rudimentary in dogs . it resides in the brachiosephallicus muscle
- While dogs do have a clavicle, it is rudimentary within the brachiosephallicus muscle and it is rarely seen on x-ray, it has no functional role in the canine shoulder
Appendicular skeleton - Brachium/Antebrachium
- This divides the thoracic limb (foreleg)
Appendicular skeleton - Humerus
- Long bone of the brachium (upper half forelimb)
- Forms portions of the shoulder and elbow joints
- Tubercles - processes where shoulder muscles attach
- Condyles - articular surfaces
Appendicular skeleton - Ulna
- Part of the antebrachium
- Olecranon process - point of elbow, site for tendon attachment or triceps brachia muscle
- Anconceal and coronoid processes articulate with the humerus
- The ulna is prone to ‘greenstick’ fractures
- We don’t repair a fractured ulna without displacement if the radius is intact, as it is not a weight baring axis
Appendicular skeleton - Radius
- Main weight bearing bone of the antebrachium
- Articulates with humerus and ulna
- Styloid process articulates with carpus
Appendicular skeleton - Carpus
- Wrist
- Two rows of bones are names (“radical carpal bone” “ ulnar carpal bone” etc)
- Distal row bones are numbered medial to lateral
Appendicular skeleton - Metacarpals
- Bones in front of paws
- extend distally from distal carpal bones to proximal phalanges
- Dogs and cats - 5 bones
Appendicular skeleton - Thoracic limb phalanges
- Phalanges (pl), Phalanx singular (bones in digits)
- Proximal, middle, distal
- Numbered 1-5
- Ungual process - within the claw on distal phalanx
- Digit 1 (dewclaw): One proximal and one distal phalanx
- Digits 2-5: A proximal, a middle and a distal phalanx
Appendicular skeleton - Pelvis
3 fused bones
- Ilium - projects in dorsocranial direction and forms the sacroiliac joint with the sacrum
- Ischium - most caudal pelvic bone
- Pubis - forms cranial portion of the pelvic floor
- Pubic symphysis - cartilaginous joint between the 2 halves of the pelvis
Appendicular skeleton - Femur
- Proximal end forms part of the hip joint
- Femoral head fits deeply into acetabulum of pelvis
- Trochlea articular groove containing the patella (knee cap)
Appendicular skeleton - Tibia
- Main weight-bearing bone of lower limb
- Forms the stifle joint with femur, the hock with the tarsus
Appendicular skeleton - Fibula
- Parallel to tibia
- Not weight-bearing
- Serves as a muscle attachment site
Appendicular skeleton - Tarsus
- Hock (ankle)
- 2 rows of tarsal bones
- Proximal row is named
- Distal row is numbered medial to lateral
- Calcaneal tuberosity (ankle): point of attachment for the tendon of the gastrocnemius muscle
Appendicular skeleton - Metatarsal bones
- Dogs and Cats - 4 metatarsal bones (1-5)
- It is uncommon for canine and feline patients to have a hind dewclaw
Appendicular skeleton - Pelvic limb phalanges
- Similar to limb phalanges
- Exceptions: Dogs and cats usually only 4 digits (2-5)
Sesamoid bones - bones within tendons
Patella - Knee cap:
- Large sesamoid bone
- Formed in the distal tendon of the quadriceps femoris muscle
- Protects the tendon
Fabellae:
- 2 small sesamoid bones in proximal gastrocnemius muscle tendons of dogs and cats
- Not present in cattle or horses
Splanchnic/Visceral skeleton:
- Bones that form in organs
Examples: - Os cordis: in heart of cattle and sheep
- Os penis: in penis of dogs, beaver, racoons, and walruses
- Os rostri: in nose of swine
Types of joints
1) Fibrous joints: immovable
2) Cartilaginous joints: slightly moveable
3) Synovial joints: freely moveable
Synovial joints
- Large range of movement
Components: - Articular surfaces on bones
- Articular cartilage (hyaline) covering articular surfaces
- Fluid-filled joint cavity enclosed by a joint capsule
- Synovial membrane
- Synovial fluid
- Ligaments - fibrous connective tissue
