Chapter 6 Flashcards
What are ligaments?
connect bone to bone
What are tendons?
connect muscle to bone
What does connective tissue do?
capture joint capsules
What are the skeletal system functions?
-protection
-mineral storage (calcium, more, phosphate, less)
-blood cell formation (red bone marrow makes blood, yellow bone marrow stores fat)
-movement (muscles produce movement via their attachment to bones)
-support
What are examples of long bones?
-most bones of the arms and legs (including humerus)
-bones of the hands, feet, fingers, and toes
-known for shape and not size
What are examples of short bones?
-carpals (bones of the wrist)
-tarsals (bones of the ankle)
-known for shape and not size
What are examples of flat bones?
-most bones of the skull
-the ribs
-sternum
-bones of the pelvis
What are examples of irregular bones?
-vertebrae
-certain skull bones
What are examples of sesamoid bones?
-patella
-suspended in tendons
What is the diaphysis?
-the shaft of the long bone
-mostly compact bone
-nutrient foramen allows blood and nerve supply to enter
-dense and solid with hollow tube in middle
What is an important concept about bone tissue and bone organs?
Bone tissue never touches bone tissue, only bone organs do
What is the epiphysis?
-wide part at each end
-articulation with other bones (joint)
-mostly spongy bone
-covered with compact bone
What does spongy bone do?
Framework that helps to transmit forces down (body weight)
lightens bone
spongy bone weakens with age
What is osteoporosis?
causes holes to appear in spongy bone particularly
What is the metaphysis?
-where the diaphysis and epiphysis meet
-growth plate exists largely here while we are young
How does bone growth appear?
Diaphysis increases in length and pushes epiphysis away
What is the medullary cavity?
-empty of bone
-has strong, compact bone walls
-center of shaft of long bone
-red bone marrow (makes blood cells, both red and white platelets)
-yellow bone marrow
What supplies red and yellow bone marrow?
Nutrient artery
What covers the outside of bones?
Periosteum
What do perforating fibers do?
-collagen of periosteum penetrates bone (perforating fibers)
-anchor tendons and ligaments to bone
-anchor collagen fibers in bone
What does the inner layer of the periosteum do?
contains cells that help make and maintain bone
What does the outer layer of the periosteum do?
fibrous layer & strong and resists stretch
What is the route for vessels and nerves to enter bone?
periosteum
What is the endosteum?
inner lining of bone
-only cellular, no fibrous component (bone cells)
-covers trabeculae of spongy bone
-lines central canals
What is the structure of flat bones?
resembles a sandwich of spongy bone
-no medullary cavity
-between 2 layers of compact bone
-spongy bone AKA diploe (with red bone marrow)
What drives the function of connective tissue?
matrix of bone tissue
What is in the dense matrix?
-deposits of calcium salts and collagen fibers
-osteocytes within lacunae
-canaliculi
How are osteocytes organized?
-around blood cells
-live in lacunae (fluid-filled)
-blood cells live in center
What is the canaliculi?
tunnel/passageway for diffusion process
form pathway for blood vessels
exchanges nutrients and wastes
What makes up 2/3’s of the bone’s matrix?
minerals (inorganic matrix)
calcium salts which form hydroxyapatite crystals
Helps bone to resist compression and gives bone its strength
What makes up 1/3 of the bone’s matrix?
protein fibers AKA collagen (organic matrix)
helps to resist twisting/breaking (reinforcement)
How much of the bone mass do the cells make up?
2%
What are the 4 cell types of bone?
osteogenic cells
osteocytes
osteoblasts
osteoclasts
What are the cycles of bone cells?
osteogenic to osteoblast to osteocyte
What is an osteogenic cell?
-stem cells
-inner lining of periosteum and endosteum
-waiting for new bone/matrix
-capable of mitosis
-differentiate
What are osteoblast cells?
make bone matrix (calcium phosphate) and collagen fibers
bury themselves in bone
once buried, leaves itself lacunae and becomes dormant and becomes osteocyte
What are osteocyte cells?
Maintains matrix
does not produce new matrix
What are osteoclast cells?
not related to other 3 cell types
multinucleated
makes enzymes and secretes to dissolve bone
What is the basic unit of compact bone?
osteon
What are the layers surrounding osteons?
concentric lamellae
What is an osteon around (what is in the middle of an osteon)?
central canal
Where is compact bone found?
walls of diaphysis
surface of epiphysis
What is in the central canal in an osteon?
blood vessels and nerves
What are perforating canals?
tunnels that connect canal to canal to outside
What are interstitial lamellae and what do they do?
remnants of old osteons
fill spaces between new osteons
Where are circumferential lamellae located and what do they do?
wrapped around whole of long bone
makes bone smooth
What does spongy bone not have?
no osteons
no central canal
What is spongy bone surrounded by?
both bone marrows
both very vascular
Where is spongy bone located?
center of epiphysis
How is spongy bone organized?
organized in branches called trabeculae
What fills the spaces between spongy bone?
bone marrow (obtains nutrients from it)
What is a spongy bone’s function?
lightens the bone and serves as transmitter of forces
What is primary bone?
-immature, woven bone
-solid mass of bone matrix
-over time, osteoclasts and osteoblasts organize matrix into layers
What are the two types of ossification?
-Intramembranous (no cartilage used)
-Endochondral (cartilage is used)
What is secondary bone?
-mature once matrix is organized into layers
-has lamellae
What is intramembranous ossification?
-starts in connective tissue proper
-skull, mandible, and clavicle form this way, AKA dermal bones
-osteoblasts migrate to periosteum
What is endochondral ossification?
-starts with hyaline cartilage model
-cartilage does NOT become bone
-cartilage dies off and is replaced with bone tissue
Where does cartilage remain?
surface (articular cartilage)
epiphyseal plate (growth plate)
What type of ossification increases bone length?
Endochondral ossification
Where does longitudinal growth occur?
at growth plate in metaphysis
What type of ossification does appositional growth occur by?
Intramembranous ossification
How does compact bone thicken and lengthen long bone?
with layers of circumferential lamellae
What happens in the zone of proliferation?
-chondrocytes produce new cartilage
-chondrocytes divide and push epiphysis away
-cells move down into zone of hypertrophy
What happens in the zone of hypertrophy and maturation?
-chondrocytes enlarge and mature
What happens in the zone of calcification?
-chondrocytes die and matrix calcifies
What happens in the zone of ossification?
-osteoblasts replace cartilage with bone tissue
-diaphysis increases in length
Where is calcium secreted in the bone growth plate zones?
between the zone of hypertrophy and calcification
What does mineral recycling allow bones to do?
adapt to stress
What happens to heavily stressed bones?
they become thicker and stronger
How much bone mass can be lost in a few weeks of inactivity?
1/3
What does normal bone growth and maintenance require?
-calcium and phosphate salts from diet
-small amounts of magnesium, fluoride, iron, and manganese
-Calcitriol
What is calcitriol?
Hormone that helps absorb calcium and phosphorus from digestive tract
What does calcitriol synthesis require?
Vitamin D3
Where is calcitriol made?
kidneys
What is Vitamin C required for?
collagen synthesis
stimulation of osteoblast differentiation
What does Vitamin A do?
stimulates osteoblast activity
What does Vitamin K & B12 do?
help synthesize bone proteins
What do growth hormone and thyroxine do?
stimulate bone growth
What do estrogens and androgens do?
stimulate osteoblasts
What do calcitonin and parathyroid hormone (PTH) do?
regulate calcium and phosphate levels
What are calcium ions vital to?
membranes
neurons
muscle cells, especially heart cells
What are calcium ions regulated by?
PTH and calcitonin
How does the PTH increase calcium ion levels in the blood?
stimulating osteoclasts
increasing intestinal absorption of calcium
decreasing calcium excretion @ kidneys
What is calcitonin secreted by and where?
secreted by C cells (parafollicular cells) in thyroid
What does calcitonin do?
decreases calcium ion levels by
-inhibiting osteoclast activity
-increasing calcium excretion @ kidneys (into urine)
-out of blood and into bones
What factors increase osteoblast activity?
compressional load or exercise
tension placed on bone
testosterone
Adequate dietary intake of calcium and vitamins C, D, and K
What factors decrease osteoclast activity?
estrogen
calcitonin
increase in blood calcium ion concentration
What factors decrease osteoblast activity?
inadequate exercise
inadequate dietary intake of calcium or vitamins C, D, or K
What factors increase osteoclast activity?
continuous pressure placed on bone
parathyroid hormone
decrease in blood calcium ion concentration
What happens in the very beginning of fracture repair?
formation of blood clot (hematoma)
What happens within a week of fracture repair?
-fibroblasts make collagen fibers and chondrocytes make cartilage
-soft callus forms
What happens around 6 weeks of fracture repair?
osteoblasts build a bone callus
bone callus is raised, hard surface. not yet stable
What happens a couple of months into fracture repair?
bone callus is remodeled and primary bone is replaced with secondary bone
What is a spiral fracture?
fracture caused by a twisting force
What is a comminuted fracture?
shattered fracture
multiple pieces
What is a greenstick fracture?
fractured on one side and folded on other
not all the way through
common in the young
What is a compression fracture?
bone is crushed under weight above
common in the elderly and those with reduced bone mass
What is an avulsion?
fracture that involves a tendon or ligament
often seen in ankle fractures
tendon or ligament pulls chunk of bone out
What is an epiphyseal plate fracture?
fractured through cartilage
can interfere with growth process
can end up with limbs of different lengths
occurs in children and young adults
When does osteopenia begin?
between ages 30 and 40
How fast do men and women lose bone mass?
women lose 8% of bone mass per decade
men lose 3% of bone mass per decade
What body parts are most affected by osteopenia?
the epiphyses
vertebrae
jaw
What does osteopenia result in?
fragile limbs
reduction in height
tooth loss
How many men and women have osteoporosis?
over age 45, occurs in 29% of women
18% of men
Put the steps of endochondral ossification in order
as the medullary cavity enlarges, the remaining cartilage is replaced by bone; the epiphyses finish ossifying
the chondroblasts in the perichondrium differentiate into osteoblasts
in the primary ossification center, osteoblasts replace the calcified cartilage with early spongy bone; the secondary ossification centers and medullary cavity develop
simultaneously, the internal cartilage begins to calcify and the chondrocytes die
osteoblasts build the bone collar on the bone’s external surface as the bone begins to ossify from the outside
- the chondroblasts in the perichondrium differentiate into osteoblasts
2a. osteoblasts build the bone collar on the bone’s external surface as the bone begins to ossify from the outside
2b. simultaneously, the internal cartilage begins to calcify and the chondrocytes die - in the primary ossification center, osteoblasts replace the calcified cartilage with early spongy bone; the secondary ossification centers and medullary cavity develop
- as the medullary cavity enlarges, the remaining cartilage is replaced by bone; the epiphyses finish ossifying
