WEEK 3: Bone Anatomy Flashcards
Lost and describe the functions of bones
- Support
- Protection
- Movement
- Mineral homeostasis (storage and release): calcium and phosphorous (gives bone hardness). The body will break down the bone to release minerals into the blood.
- Blood cell production (red bone marrow).
- Triglyceride storage (yellow bone marrow)
What are the five classifications of bone?
- long
- flat
- short
- irregular
- sesamoid
What are long bones?
- longer than they are wide
FUNCTION: support weight and facilitate movement
e.g., the lower limbs (the tibia, fibula, femur, metatarsals, and phalanges) and bones in the upper limbs (the humerus, radius, ulna, metacarpals, and phalanges).
What are flat bones?
- flattened bones, thin
FUNCTION: protection and a large area of attachment for muscles
e.g., scapula, sternum, ribs
What are short bones?
- about as long as they are wide
FUNCTION: provide stability and some movement
i.e., carpals in the wrist (scaphoid, lunate, triquetral, hamate, pisiform, capitate, trapezoid, and trapezium) and the tarsals in the ankles (calcaneus, talus, navicular, cuboid, lateral cuneiform, intermediate cuneiform, and medial cuneiform).
What are irregular bones?
- complex shapes
FUNCTION: often serve as protection for internal organs
i.e., vertebrae, coccyx, temporal, sphenoid.
What are sesamoid bones?
- bone embedded in tendons
FUNCTION: protection from stress and wear
i.e., patella, found in knee/thumb/toe
Structures of bone: diaphysis
- middle section of the bone that houses the medullary cavity
Structures of bone: proximal and distal epiphysis
- ends of bone that is filled with spongy bone
- contains red bone marrow
- each end meets at the metaphysis
- prox is up high, dist is down low
Structures of the bone: medullary cavity
- filled with yellow bone marrow that is made of adipose tissue
- adipose tissue holds tyglericides
Structures of the bone: endosteum
- the inner lining of the medullary cavity
Structures of the bone: periosteum
- the fibrous membrane of the bone
- covers the entire external surface of the bone
Structures of the bone: epiphyseal plate
- indicative of the boundary between the epiphysis and the diaphysis
- is a layer of hyaline cartilage
- the location where growth prior to puberty occurs
Structures of the bone: articular cartilage
- a thin layer of cartilage that reduces friction and acts as a shock absorber
Types of bone cells:
- Osteoprogenitor cell
- Osteoblast
- Osteocyte
- Osteoclast
What are osteoprogenitor cells?
- Stem cell (where bone originates from)
- Derived from mesenchyme.
- Located in endosteum and periosteum.
- Differentiate into osteoblasts (only cells that undergo division)
What are osteoblast cells?
- they are matrix-synthesising cells that are responsible for bone growth
- they synthesise and secrete osteoid
- located in endosteum and periosteum
OSTEOID =made of collagen fibres and other substances necessary to the formulation of ground substance (unmineralised bone matrix)
- osteoid can bind calcium and phosphorus
- osteoid is secreteted around the cell and the cells become trapped > forms an osteocyte
What are osteocytes?
- mature bone cells that become trapped in lacunae (are trapped in osteoid cellular matrix)
- monitor and maintain the mineralised bone matrix (transport waste and nutrients to and from the cell)
- sense mechanical loading
What are lacunae?
- the spaces that osteocyte cells are trapped in after osteiod fluid is secreteted
What are canaliculi?
- the long processes that extend from osteocytes, that allow them to communicate with one another
- they function as tunnels that extend out from each of the cells
- they are critical to mineral homeostasis: they move waste and nutrients in and out of the cells
What are osteoclasts?
- derived from WBCs
- they migrate from bone marrow and into the bone tissue
- they are bone-resorbing cells; the cells that degrade bone to initiate normal bone remodeling and mediate bone loss in pathologic conditions by increasing their resorptive activity
- they have a ruffled border that adheres to the bone’s extracellular matrix
- when it attaches to the matrix, it secretes acids and enzymes that break down the bone
Features of compact bone (cortical bone)
- is an extracellular matrix filled with tightly bunched together collagen fibres and calcified osteoid.
- composed of closely packed osteons
- tiny spaces between lacunae
- is the hard external layer of bones
FUNCTION: strength, protection, support
What are osteons?
- ompact rings of concentric lamellae
Features of spongy bone (cancellous bone)
- bone tissue is an open network
- lamellae are arranged to form trabeculae (rather then osteon rings)
- red bone marrow is situated between the trabeculae
FUNCTIONS: flexability (can compress), shock absorber, produce blood cells
