Skeletal System Flashcards
Functions of the skeletal system
Support Movement Protection Storage Production
Function of compact bone
Strong, good at transmitting force in one direction
Function of cancellous (trabecular) bone
Shock absorption (light and spongy), resists and channels forces from multiple directions, produces red blood cells.
Long bones
Longer than they are wide, act as levers, thick compact bone in diaphysis.
Made of epiphysis, medullary cavity and diaphysis
Short bones
Closer to equal width and length, can bear weight in multiple directions and are mostly composed of cancellous bone
Flat bones
Usually intended as muscle attachment surfaces or protective plates, composed of outer layers of compact bone over cancellous volumes
Irregular bones
Various shapes and functions. Not round, flat, square or predominantly cancellous. Often have foramen
Cranium vault
Encloses brain (internally), lots of space for muscle attachments (externally)
Facial bones
Makes housing of eyes nose and mouth
Vertebral collumn
Directs weight force down ward for support and erect positioning. Made of:
- Cervical bones 1-7
- Thoracic bones 1-12
- Lumbar bones 1-5
- Sacral bones 1-5 (2-5 are fused)
- Coccyx (fused)
Pectoral girdle
Made of clavicle, floating scapula for upper limb attachment with large mobility
Pelvic girdle
Made of hip bones and sacrum, bigger and more powerfully bound for weight bearing and directing force into lower limbs (and into ground, for movement)
Dimorphic
Differing by gender
Bone local adaptation
Bones are plastic and can remodel to an extent to assist in the dealing with of consistently applied forces on an individual by thickening, thinning or adjusting cancellous bone force direction
Organic ECM (bone matrix)
Makes up a third of the bone matrix, consists of collagen fibers in a ground substance, the fibers provide resistance against brittleness and tension
Inorganic ECM (bone matrix)
Makes up two thirds of the bone matrix. Composed of hydroxyapatite and other minerals. Minerals provide the strength and rigidity of bones aka resisting compression.
Cellular component of Bone Matrix
Only makes up 2% of bone weight by volume, responsible for directing homeostasis and local adaptations of bone
Osteogenic cell
Stem cells that produce osteoblasts
Osteoblast
Produce new bone matrix
Osteoclast
Deconstruct old bone matrix
Osteocyte
Maintain the bone matrix by recycling proteins and minerals of the ECM and communicating the needs of bone homeostasis
Osteon structure
Cylindrical structure with a central canal organized parallel to one another to form compact bone. Macroscopically dense with foramen for blood supply to canal.
Trabecular structure
Struts of lamella, osteocytes housed in lacunae on surface of lamella and marrow fills the space between lamella to form cancellous bone. No central canal, diffusion is enough.
Osteon
A single longitudinal cylinder in the osteon structure of compact bone. Each has a canal housing blood vessels and nerves running through its centre
Central (Haversian) canal
Osteon structure (compact bone) only. Houses blood vessels and nerves.
Lamellae
Series of rings form of ECM, in osteon structure this is around a central canal, in trabecular there is no canal so lamellae is solid
Lacunae
Pools of osteocytes housed perpendicular to and in lamella length.
Canaliculi
Channels for osteocytes through the ECM, allowing communication of homeostatic maintenance and delivery of nutrients. Connects to central canal in compact bone and to adjacent cavities in cancellous
Appositional Growth
Widens bone. Osteoblasts add bone matrix to periosteum, osteoclasts remove and recycle matrix from lamella at inner surface
Bone homeostasis
Osteoblast activity is equal to osteoclast activity allowing the body to mobilize minerals bound in the bone matrix and to facilitate the plastic responses of remodelling
Osteoporosis
The clinical stage of osteopenia where destruction of bone matrix has taken over it’s rate of creation. This results in weaker less compact bone and thinner structurally compromised cancellous bone. Compression fractures become more likely.
Periosteum
- Except within joint cavities, covers all bones
- Isolates bone from surrounding tissue
- Provides route for blood/nervous supply
- Actively participates in growth, repair, remodelling
Perforating fibres
Cement collagen fibers into lamella from tendons/ligaments and joint capsules. Often stronger than the bone it’s attached to
Endosteum
- Covers trabeculae structure of spongy bone, lines inner surfaces of central canal in compact bone
- Simple flattened layer of osteogenic cells covering bone matrix
- Few or no intervening connective fibers
- Where endosteum isn’t covering bone matrix with osteogenic cells, is where bone matrix can be build or removed
Osteoclastic crypt
Space of small depression in endosteum where osteoclasts have cleared bone
Primary ossification
First part of bone made in center of cartilage in endochondral ossification. This is the diaphysis of long bones
Secondary ossification
Secondary points of ossification during endochondral ossification. In long bones, this is the epiphysis
Epiphyseal plate
Of hyaline cartilage. Separates primary and secondary ossifications. As cartilage grows, chondrocytes die and leave canals that guide osteoblast production, this makes bones grow in length
Hyaline cartilage
Articular cartilage between two bones at a joint. Creates smooth friction reduced surface. Collagen fibers are barely visible and the high water content in it’s matrix make it compression resistant
Chondrocyte
Sit within lacunae of cartilage matrix, responsible for constructing matrix.
Nutrient delivery to Cartilge
Movement causes blood to move through joint, compression drives higher diffusion rate
Fibrocartilage
Thick bundles of collagen oriented with tension forces. Moderate water content. Generally found in joints under both compression and tension. Distributes forces over wider area
Dense fibrous connective tissue (DFCT)
Composed of collagen and elastin, makes up tendons and ligaments. Alignment of fibers enables resistance of tension. Some direct blood supply
Fibroblast
DFCT cell
Bony congruence
Sum of bone surfaces at articulation
Less congruence means more soft tissue support is needed to distribute force
Fibrous joint
DFCT forms ligaments which holds two bones two bones firmly in place such as in the sutures of skull
Cartilaginous joint
Connected entirely by cartilage, made of fibrocartilage and composes structures sure as intervertebral disks or pubis symphyses where high elasticity and compression resistance is required.
Subchondral
Bone underneath articular hyaline cartilage (bone ends)
Synovial membrane
Produces synovial fluid for lubrication of joint
Synovial fluid
Contains some level of nutrients. It’s fluidity is good at absorbing shock and reducing friction at the joint
Joint loading
Cartilage is compressed at joint, pressing out old synovial fluid. When cartilage is decompressed after loading, the cartilage expands taking up a new volume of fluid
Joint capsule (5)
- Sheet of DFCT
- Continuous with periosteum
- Holds bones together
- Thickens for support, thins to allow movement
- Container of potential space on joints
Capsular ligament
Continuous with joint capsule. Thickened region of joint capsule that prevents movement in directions detrimental to the joint
Intracapsular ligament
Separate from joint capsule, but contained within it. Composed of DFCT, prevents movement of bones in directions detrimental to joint
Fibrocartilaginous structure
Consists of a mixture of white fibrous tissue (for toughness) and cartilaginous tissue (for elasticity) in various proportions.
Miniscus
Sits between articular cartilage, made of fibrocartilage, absorbs shock and helps better direct force between joints
