Flashcards in Exam 4 - chapter 6 Deck (47)
Functional properties of hyaline cartilage
Provides support, flexibility, and resilience for articular, costal, respiratory, and nasal region.
Functional properties of elastic cartilage
Provides elasticity in external ear and epiglottis
Functional properties of fibrocartilage
thick collagen fibers provide tensile strength for the menisci of the knee and the vertebral discs. (also in pubic symphosis)
Cartilage growth: appositional
cells secrete matrix against external face of existing cartilage
Cartilage growth: interstitial
chondrocytes divide and secrete new matrix, expanding cartilage from within.
2 major groups of the skeleton
axial: skull, vertebrae, rib cage
appendicular: limbs, girdles (shoulder, pelvic)
4 bone classes
long bones: longer than they are wide. ex, limbs.
short bones: cube-shaped bones. ex, wrist & ankle
flat bones: thin, flat, and slightly curved. ex, sternum, scapula, ribs, most skull bones.
irregular bones: anything else. ex, vertebrae, coxal bones.
7 important functions of bones
1. support - for body & soft organs
2. protection - brain, spine, vital organs
3. movement - levers for muscle action
4. mineral & growth factor storage - Ca + phosphorus, growth factors reservoir
5. blood cell formation - blood cell formation in red marrow cavities in certain bones (hematopoiesis)
6. triglyceride (fat) storage - fuel / energy
7. hormone production - osteocalcin - regulates bone formation, protects from obesity, glucose intolerance, diabetes.
gross anatomy of long bones
composed of spongy (trabeculae, honeycomb) and compact bone (dense outer layer, smooth & solid)
has 2 epiphyses (ends) and the middle piece is the diaphysis. between the epiphyses and the diaphysis is the epiphyseal line (plate in younger people).
bone is lined with periosteum, and inner medullary cavity is lined with endosteum. inside is yellow bone marrow.
Joints are covered by articular cartilage
gross anatomy of flat bone
thin plates of spongy bone covered by compact bone. plates are sandwiched between connective tissue membranes (periosteum, endostum).
no shaft or epiphyses, bone marrow throughout spongy bone, but no marrow cavity.
hyaline cartilage covers articular surfaces.
microscopic anatomy of compact bone
5 types of cells:
osteogenic, osteoblasts, osteocytes, bone lineing cells (periosteal / endosteal), and osteoclasts
mitotically active stem cells in periosteum and endosteum. when they are stimulated, they differentiate into osteoblasts (bone forming) or revert back to more osteogenic cells
bone forming cells, secrete unmineralized bone matrix (osteoid) - includes collagen and Ca-binding proteins. actively mitotic.
mature bone cells in lacunae. they monitor and maintain bone matrix. respond to strain and stress and communicate with osteoblasts and osteoclasts for bone remodeling.
periosteal/endosteal: flat cells on bone surfaces which maintain matrix.
break down bone - hematopoietic stem cells that become macrophages. rest in resorption bay and have a ruffled border to increase surface area for enzyme degradation of bone and seals off area from surrounding matrix.
microscopic anatomy of compact bone
osteon: structural unit of compact bone - cylinder parallel to the long axis of the bone.
elongated cylinder parallel to the long axis of bone
lamellae - hollow tubes of bone matrix; collagen fibers in the same ring run in the same direction, but adjacent rings run in different directions to withstand stress and resist twisting
central canal runs through core of osteon which contains blood vessels and nerve fibers.
volkmann's canals run perpendicular to canal, and connect blood vessels and nervs of periosteum, medullary cavity, and central canal.
lacunae - small cavities that contain osteocytes.
canalculi = hairline canals that connect lacunae to each other and central canal.
microscopic anatomy of spongy bone
appears poorly organized, with trabeculae
contain irregularly arranged lamellae and ostoecytes interconnected by canalculi. capillaries in endosteum supply nutrients.
organic components of the chemical composition of bone
osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts, osteoids.
1/3 of organic bone matrix is secreted by osteoblasts (made up of ground substance, collagen fibers, and contributes to structure; provides tensile strength, flexibility)
inorganic components of chemical composition of bone
hydroxyapatites (mineral salts) - 65% of bone by mass, mainly of tiny calcium phosphate crystals in and around collagen fibers
responsible for hardness and resistance to compression
bone develops from fibrous membrane, resulting in a membrane bone (flat bones, like clavicles and cranial bones)
bone forms by replacing hyaline carilage. bones are called cartilage bones, forms most of skeleton.
interstitial growth: growth in length of long bones
requires presence of epiphyseal cartilage
epiphyseal plate maintains constant thickness - rate of cartilage growth on one side balanced by bone replacement on the other.
concurrent remodeling of epiphyseal ends to maintain proportion
interstitial growth zones
1. resting zone - cartilage on epiphyseal side of epiphyseal plate (inactive)
2. proliferation zone: cartilage on diaphysis side of epiphyseal plate, rapidly divide pushing epiphysis away from diaphysis
3. hypertrophic zone: older chondrocytes which erode and enlarge, leaving interconnected spaces
4. calcification zone: surrounding cartilage matrix calcifies, chondrocytes die and deteriorate
5. ossification zone: stalagtite-looking, osteoclasts erode spicules and osteoblasts cover them with new bone, ultimately spongy bone replaces them
bone remodeling components
osteoblasts: secrete new bone matrix (bone deposit)
dig depressions and grooves as they break down matrix, secret lysosomal enzymes that digest matrix and protons, acidity converts salts to soluble forms.
-they also fagotize demineralized matrix and dead osteocytes
primary ossification center
begins in center of shaft, blood vessel infiltration of perichondrium converts it to periosteum
secondary ossification center
appear in epiphyses
vitamin d's affect on bone growth and development
increases the flow of calcium into the blood stream by promoting absorption of calcium from food.
somatotropin (growth hormone)'s affect on bone growth and development
stimulates epiphyseal plate activity in infancy and childhood
thyroid hormone's affect on bone growth and development
modulates activity of growth hormone, ensures proper proportions
calcitonin's affect on bone growth and development
reduces blood calcium, opposing the effects of PTH. works with PTH so maintain homeostasis.
parathyroid hormone's affect on bone growth and development
removes calcium from bone regardless of bone integrity. works with calcitonin to maintain homeostasis.
androgen's affect on bone growth and development
sex hormones help maintain health & normal density of the skeleton by restraining osteoclasts and promoting deposit of new bone. after menopause, estrogen levels drop and deficiency is strongly implicated in osteoporosis in older women.
physical stress associated with exercise's affect on bone growth and development
weight bearing exercise increases bone mass above normal values and provide a greater buffer against age-related bone loss
bone fragments into three or more pieces
bone is crushed. comon in porous bones subjected to extreme trauma, like a fall.
ragged break occurs when excessive twisting forces are applied to bone - common sports fracture
epiphyseal separates from the diaphysis along the epiphyseal plate - occurs when cartilage cells are dying and calcification of the matrix is occurring
broken bone portion is pressed inward - skull fracture
bone breaks incompletely, like a green twig. only one side breaks, other side bends. common in children whose bones have relatively more organic matrix are more flexible than adults.
hematoma forms (collection of blood) - clot forms, site is swollen, painful, and inflamed
1st step in fracture repair
fibrocartilaginous callus forms -
capillaries grow into hematoma,
phagocytic cells clear debris,
fibroblasts secrete collagen fibers to span break and connect broken ends,
fibroblasts, cartilage, and osteogenic cells begin reconstruction of bone
mass of repair tissue called fibroartilaginous callus
2nd step in fracture repair
bony callus forms
in 1 week, new trabeculae appear in fibrocartilaginous callus,
callus converted to bony (hard) callus of spongy bone
~2 months later firm union forms
3rd step in fracture repair
bone remodeling occurs
begins during body callus formation
continues for several months
excess material on diaphysis exterior and within medullary cavity removed
compact bone laid down to reconstruct shaft walls
final structure resembles original because responds to same mechanical stressors
4th step of fracture repair
bones poorly mineralized
calcium salts not adequate
soft, weak bones
pain upon bearing weight
rickets (osteomalacia of children)
bone resorption outpaces deposit
spongy bone of spine and neck of femur most susceptible (vertebrae/hip fractures most common)