A&P 6: Bones & Skeletal Tissue Flashcards
Skeletal cartilage
made of some variety of cartilage tissue molded to fit its body location and function
Hyaline cartilages
provide support with flexibility and resistance; most abundant skeletal cartilages; chondrocytes are spherical; only fiber type in matrix is fine collagen (undetectable microscopically); includes articular, costal, respiratory, and nasal cartilages
Elastic cartilages
more stretch elastic than hyaline cartilages and so are better able to stand up to repeated bending; found in only 2 skeletal locations - the external ear and the epiglottis
Fibrocartilages
highly compressible with great tensile strength; consist of roughly parallel rows of chondrocytes alternating with thick collagen fibers; occur in sites subjected to both pressure and stretch (padlike cartilages (menisci) of knee and the discs between vertebrae)
Appositional growth
“growth from outside”; cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue
Interstitial growth
“growth from inside”; the lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within
Axial skeleton
forms the long axis of the body; includes the bones of the skull, vertebral column, and rib cage; protect, support, or carry other body parts
Appendicular skeleton
consists of the bones of the upper and lower limbs and the girdles (shoulder bones and hip bones) that attache the limbs to the axial skeleton
Long bones
bones that are considerably longer than they are wide; has a shaft plus 2 ends which are often expanded; all limb bones except the patella, wrist, and ankle bones are this type
Short bones
bones that are roughly cube shaped; example: bones of the wrist/ankles
Sesamoid bones
“shaped like a sesame seed”; special type of bone that form in a tendon (ex. patella); vary in size and number in different individuals; some act to alter the direction of pull of a tendon
Flat bones
bones that are thin, flattened, usually a bit curved; ex: sternum, scapulae, ribs, and most skull bones
Irregular bones
bones with complicated shapes that fit no class; ex. vertebrae, hip bones
Hematopoiesis
blood cell formation; mostly occurs in the red marrow cavities of certain bones
Compact bone
external layer of bone; dense, looks smooth, solid
Spongy bone
AKA trabecular bone; internal to compact bone, a honeycomb of small needle-like or flat pieces (trabeculae)
Trabeculae
“little beams”; small needle-like or flat pieces in spongy bone
Diploe
in flat bones, the spongy bone is called this, which means “folded”
Diaphysis
tubular shaft that forms the long axis of a typical long bone
Medullary cavity
diaphysis is constructed of a relatively thick collar of compact bone that surrounds a central _________ ______; in adults, it contains fat (yellow marrow)
Yellow marrow cavity
in adults, the medullary cavity contains fat and is called this
Epiphyses
ends of long bones; in many cases, are broader than the diaphysis
Epiphyseal line
between the diaphysis and each epiphysis of an adult long bone is this, a remant of the epiphyseal plate
Epiphyseal plate
disc of hyaline cartilage that grows during childhood to lengthen the bone
Periosteum
glistening, white double-layered membrane that covers the external surface of the entire bone except the joint surfaces; outer fibrous layer, osteogenic layer
Nutrient foramina
periosteum is richly supplied with nerve fibers and blood vessels which pass through the shaft to enter the marrow cavity via these “openings”; perforating (Sharpey’s) fibers secure the periosteum to the underlying bone
Endosteum
“within the bone”; delicate, connective tissue membrane which covers internal bone surfaces
Red marrow
hematopoietic tissue, typically found within the trabecular cavities of spongy bone of long bones and in the diploe of flat bones
Red marrow cavities
trabecular & diploe cavities often called this
Bone markings
serve as sites of muscle, ligament, and tendon attachment, as joint surfaces, or as conduits for blood vessels and nerves; those that are depressions and openings include fossae, sinuses, foramina (sing = foramen), and grooves - allow nerves/blood vessels to pass; projections (project outward) = heads, trochanters, spines, etc)
Osteogenic (osteoprogenitor) cells
mitotically active stem cells found in the membranous periosteum and endosteum; in growing bones = flattened/squamous cells; when stimulated, differentiate into osteoblasts or bone lining cells, while others persist as is
Osteoblasts
bone-forming cells that secrete the bone matrix; actively mitotic; unmineralized bone matrix they secrete includes collagen (90% of bone protein) and calcium-binding proteins that make up the initial unmineralized bone (osteoid); also play a role in matrix calcification
Osteocytes
spidery, mature bone cells that occupy spaces (lacunae) that conform to their shape; monitor and maintain the bone matrix; act as stress/strain sensors and respond to mechanical stimuli (bone loading, bone deformation, weightlessness)
Bone lining cells
flat cells found on bone surfaces where bone remodeling is not going on; thought to help maintain the matrix; on the external bone surface, AKA periosteal cells; those lining internal surfaces AKA endosteal cells
Osteoclasts
derived from the same hematopoietic stem cells that differentiate into macrophages; giant multi-nucleate cells located at sites of bone resorption; rest in a shallow depressions called a resorption bay when actively breaking down (resorbing) bone; exhibit a distinctly ruffled border which directly contacts the bone (increase surface area for enzymatically degrading the bones and seal off that area from the surrounding matrix)
Osteon (Haversian system)
structural unit of compact bone; each = elongated cylinder oriented parallel to the long axis of the bone; tiny, weight-bearing pillars
Lamella
“little plate”; a layer, such as of bone matrix in an osteon of compact bone
Lamellar bone
AKA compact bone
Central (Haversian) Canal
running through the core of each osteon is this canal, containing small blood vessels and nerve fibers that serve the osteon’s cells
Perforatin (Volkmann’s) Canals
canals that lie at right angles to the long axis of the bone and connect the blood and nerve supply of the periosteum to those in the central canals and the medullary cavity
Lacunae
spider-shaped osteocytes occupy these at the junctions of the lamellae
Interstitial lamellae
lying between intact osteons are incomplete lamellae; either fill the gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling
Circumferential lamellae
located just deep to the periosteum, just superficial to the endosteum; extend around the entire circumference of the diaphysis, effectively resist twisting of the long bone
Osteoid
organic part of bone matrix; makes up 1/3 of the matrix, includes ground substance (composed of proteoglycans and glycoproteins) and collagen fibers, both of which are made and secreted by osteoblasts; contribute to a bone’s structure and to the flexibility and tensile strength that allow it to resist stretch and twisting
Ossification
AKA osteogenesis; process of bone formation
Cartilage (endochondral) bone
bone developed by replacing hyaline cartilage (via endochondral ossification)
Membrane bone
in intramembranous ossification, a bone develops from a fibrous membrane
Endochondral ossification
essentially all bones below the base of the skull (except the clavicle) form by this process
Primary Ossification Center
formation of a long bone typically begins in the center of the hyaline cartilage shaft at a region called this
Periosteal bud
collection of elements which contain a nutrient artery and vein, nerve fibers, red marrow elements, osteogenic cells, and osteoclasts; invades the forming cavities to form spongy bone
Secondary ossification centers
shortly before or after birth, these appear in one or both epiphyses, and the epiphyses gain bony tissue
Intramembranous ossification
forms the cranial bones of the skull (frontal, parietal, occipital, and temporal bones) and the clavicles; most bones formed by this process are flat bones
Bone remodeling
bone deposit & bone resorption
Parathyroid hormone (PTH)
hormonal control of remodeling; produced by the parathyroid glands
Calcitonin
produced by parafollicular cells (C cells) of the thyroid gland, may be involved in hormonal control of remodeling, though to a lesser extend than PTH
Fractures
breaks in bones
Hematoma
mass of clotted blood; forms at the fracture site in bones
Fibrocartilaginous callus
entire mass of repair tissue that splints the broken bone
Bony (hard) callus
new bone trabeculae appear in the fibrocartilaginous callus and gradually convert it to this; formation continues until a firm union forms about 2 months later
Osteomalacia
“soft bones”; includes a number of disorders in which the bones are poorly mineralized; osteoid is produced, but calcium salts are not adequately deposited, so bones are soft and weak; main symptom is pain
Rickets
like osteomalacia, but in children and much more severe; bowed legs, deformities of the pelvis, skull, and rib cage are common; epiphyseal plates cannot calcify (so continue to widen) and the ends of long bones become visibly enlarged and abnormally long
Osteoporosis
refers to a group of diseases in which bone resorption outpaces bone deposit; bones become fragile, have tendency to break much more easily than normal; composition of the matrix remains normal, but bone mass declines, and the bones become porous and light
Paget’s disease
characterized by excessive and haphazard bone deposit and resorption; has an abnormally high ratio of spongy bone to compact bone
