Chapter 5 Flashcards
Bones as Organs
List the functions of the skeletal system
Encasement and protection
Support and movement
Hemopoiesis (blood cell production)
Mineral and energy storage
List the five categories of bones and give an example of each.
Flat bones - thin, broad, and commonly curved; characterized by a layer of spongy bone in between two thin layers of compact bone Examples: scapula, sternum, ribs
Irregular bones - all bones that do not easily fit into the other shape classifications
Examples: vertebrae, ethmoid bone, sphenoid bone, hip bones (os coxae)
Sesamoid bones - small, flat, and oval shaped bones that are specialized and found within tendons; their role is to increase muscle leverage and increase the longevity of tendons
Example: patella (kneecap)
Short - bones that are equally long and wide, forming a cube in shape
Examples: carpals (hands), tarsals (feet)
Long - bones that are longer than they are wide (shape, not size matters)
Examples: phalanges (fingers and toes), humerus (arm), femur (leg)
Define and identify the diaphysis
the long, tubular portion located in the central part of the long bone
Define and identify the epiphysis
a wider region at either end of a long bone that varies in shape
Define and identify the periosteum
a tough, two-layer connective tissue covering located on the external surface of bones; consists of an outer fibrous connective tissue layer and an inner cellular layer; covers the outer surfaces of all bones except for articular surfaces where cartilage will cover the bone instead; richly supplied with blood vessels and neuronal axons
Define and identify the medullary cavity
the cylindrical, hollow center of the diaphysis that is filled with yellow bone marrow in adults
Define and identify the endosteum
a layer of cells that line the walls of the medullary cavity
Define and identify compact bone
hard, dense non-cancellous portion of bone consisting largely of concentric lamellar osteons and interstitial lamellae; located underneath the periosteum; also known as cortical bone
Define and identify spongy bone
a sponge or honeycomb-like layer of bone found deep to compact bone that is characterized by narrow plates of bone (called trabeculae) forming a complex interlocking lattice arrangement; primarily located within the proximal and distal epiphyses in long bone and the central part of flat bones; also known as trabecular bone
Compare and contrast compact and spongy bone.
Compact bone - very solid and dense, makes up ~80% of our mass, forms outer shell of all bones but varies in thickness depending on bone type
Spongy bone - found within the epiphysis of long bones, makes up interior bulk of short and bones, called diploë in the flat bones of the skull
Specify the bone cells responsible for absorbing bone, depositing bone, and monitoring bone and explain how they remodel bone over the course of a lifetime
osteoprogenitor (osteogenic) cells - stem cells derived from mesenchyme found in periosteum and endosteum that mature into osteoblasts
osteoblasts - build bone by secreting osteoid (an organic bone matrix) that will later calcify when calcium salts are deposited; eventually become trapped in the bone they secreted (in small cavities called lacunas) and change into osteocytes
osteocytes - mature osteoblasts that maintain bone health; secretions maintain the extracellular matrix (ECM); can recruit osteoblasts to strengthen areas of bone that are experiencing increased tension or compression
osteoclasts - large, multinucleated cells responsible for bone breakdown (in a process called bone resorption); produce secretions that break down the organic (collagen fibers; broken down using enzymes) and inorganic components of bone (calcium and phosphate; broken down using hydrochloric acid)
Compare which parts of the skeleton develop from endochondral ossification and which parts of the skeleton develop from intramembranous ossification
Endochondral ossification: produces most bones of the skeleton (including long bones, vertebrae, and ribs)
Intramembranous ossification: bones developing within a membrane (e.g. flat bones of skull, many facial bones, mandible, portion of the clavicle)
List the six major steps of endochondral ossification
1: Fetal hyaline cartilage model develops (chondroblasts secrete a cartilage matrix to form a hyaline cartilage model (8-12th week of fetal development); this model is covered by perichondrium that serves as a template that will later be converted to bone)
2: Cartilage calcifies, and a periosteal collar forms around diaphysis (osteoblasts begin to deposit osteoid in the hyaline cartilage surrounding the diaphysis, forming the periosteal collar; chondrocytes are deprived of nutrients as the composition of the matrix changes and increases in density, leading them to begin to atrophy and die; this causes cavities to form within the cartilage model)
3: Primary ossification center forms in the diaphysis (blood vessels and osteoblasts form a periosteal bud that pierces the cartilage model and moves into the cavity within the diaphysis; the osteoblasts begin to secrete osteoid within this cavity, creating new bone; this area of new bone is called the primary ossification center (first site of bone formation)) (6-12 weeks of fetal development)
4: Secondary ossification centers form in epiphyses (cartilage in epiphyses begin to degenerate; blood vessels and osteoprogenitor cells enter the epiphyses; osteoprogenitor cells mature into osteoblasts and begin to secrete osteoid inside the epiphyses, creating secondary ossification centers, which become the proximal and distal epiphyses of long bones and projections) (around time of birth)
5: Bone replaces cartilage, except at articular cartilage and epiphyseal plates (as diaphysis grows in length) (childhood and adolescence)
6: Epiphyseal plates solidify and form epiphyseal lines (begin around 10 years of age, finish in mid to late 20’s)
Explain where the primary ossification center and secondary ossification centers are located in a long bone during endochondral ossification
Primary: diaphysis
Secondary: epiphyses
List the four main steps of bone fracture repair
1: Formation of a hematoma around the fracture
2: Soft (fibrocartilaginous) callus development
3: Hard (bony) callus development
4: Bone remodeling
