Chapter 6 Flashcards
Bone is hard and rigid; cartilage is flexible yet strong. Cartilage in nose, external ear, thoracic cage and trachea.
Support
connect bone to bone.
Ligaments
Skull around brain; ribs, sternum, vertebrae protect organs of thoracic cavity.
Protection
Produced by muscles attached to bones via tendons.
Movement
Calcium and phosphate stored and released as needed. Adipose tissue stored in marrow cavities
Storage
Bone marrow that gives rise to blood cells and platelets
Blood cell production
form matrix.
Chondroblasts
surrounded by matrix; are within lacunae.
Chondrocytes
Collagen fibers for strength, proteoglycans for resiliency.
Matrix
Double-layered C.T. sheath. Covers cartilage except at articulations.
Perichondrium
More delicate, has fewer fibers, contains chondroblasts.
Inner Perichondrium
Blood vessels and nerves penetrate. No blood vessels in cartilage itself
Outer Perichondrium
Covers bones at joints; has no perichondrium Growth.
Articular cartilage
New chondrocytes and new matrix at the periphery.
Appositional
Chondrocytes within the tissue divide and add more matrix between the cells.
Interstitial
If mineral removed,
bone is too bendable
If collagen removed,
bone is too brittle.
Bone-building cells, produce collagen and proteoglycans
OSTEOBLASTS
produced by E.R. and golgi apparatus. Released by exocytosis.
Collagen
stored in vesicles, then released by exocytosis
Precursors of hydroxyapatite
Formation of bone by osteoblasts.
communicate through gap junctions.
Cells surround themselves by matrix.
OSSIFICATION
Mature bone cells.
Stellate.
Surrounded by matrix but can make small amounts of matrix to maintain it
OSTEOCYTES
spaces occupied by osteocyte cell body.
Lacunae
canals occupied by osteocyte cell extensions.
• Nutrients and gases can pass through:
• the small amount of fluid surrounding the cells in the canaliculi and lacunae
Canaliculi
Resorption of bone.
OSTEOCLASTS
the specialized reabsorption-specific area of the membrane
Ruffled border
are secreted into the extracellular space, enter the blood, and are used elsewhere in the body.
Degradation products
Stem cells called ____ can become osteoblasts or chondroblasts?
osteochondral progenitor cells
from osteochondral progenitor cells
Osteoblasts
from osteoblasts
Osteocytes
from stem cells in the red bone marrow
Osteoclasts
Brittle bone disorder
OSTEOGENESIS IMPERFECTA
caused by mutations that yield reduced or defective Type I collagen
CT disease
• Mildest, most common form
• Too little formation of normal type I collagen
• Bones are predisposed to fracture, tendency to develop spinal curvature
Type I Ol
Unlike those with more severe forms of Ol, these patients have normal or near-normal stature and minimal or no bone deformities
Type I Ol
• Most severe
• Usually lethal within the 1st week of life due to breathing failure caused by rib fractures and underdeveloped lungs
Type II Ol
Characterized by bones that fracture very easily, even before and during birth.
Fractures occurring before birth often heal in poor alignment, leaving the limbs short and bent.
Type Ill Ol
Collagen fibers randomly oriented.
• First type of bone formed by osteoblasts during ossification.
Woven bone
• Osteoclasts remove old bone and osteoblasts add new.
• Woven bone is remodeled into lamellar bone.
Remodeling
Mature bone in concentric sheets or layers called?
lamellae
appears porous
Spongy bone
interconnecting rods or plates of bone. Like scaffolding.
Trabeculae
Solid, outer layer surrounding each bone; has more matrix and is denser than spongy bone.
Blood vessels enter the bone and the lamellae are oriented around the blood vessels.
Compact Bone
Functional unit of compact bone is an?
osteon or haversian system.
Composed of concentric rings of matrix around a ____ , giving the appearance of a bulls-eye?
central canal
parallel to long axis.
Central or Haversian canals
concentric, circumferential, interstitial
Lamellae
perpendicular to long axis.
Perforating or Volkmann’s canal
Center portion of the bone
Diaphysis
primarily composed of compact bone surrounding the medullary cavity.
Shaft
In children ___ is red marrow for blood cell formation?
Medullary cavity
• In adult, red marrow is replaced by?
yellow in limb bones
End of the bone; primarily spongy bone covered with compact bone.
Epiphysis
growth plate
Epiphyseal plate
present until growth stops.
Hyaline cartilage
epiphyseal plate is ossified as bone stops growing in length.
Epiphyseal line
epiphyseal plate is ossified as bone stops growing in length.
Epiphyseal line
Connective tissue membrane covering the outer surface of a bone.
Periosteum
is dense irregular collagenous CT containing blood vessels and nerves.
Outer fibrous layer
is dense irregular collagenous CT containing blood vessels and nerves.
Outer fibrous layer
is a single layer of bone cells including osteoblasts, osteoclasts and osteochondral progenitor cells.
inner fibrous layer
some periosteal fibers penetrate through the periosteum and into the bone. Strengthen attachment of tendon to bone.
Perforating fibers (Sharpey’s fibers)
Single cellular layer of CT that lines all internal spaces of all cavities within the bones, such as the medullary cavity of the diaphysis and the smaller cavities in spongy and compact bone.
Endosteum
Includes osteoblasts, osteoclasts, and osteochondral progenitor cells.
Endosteum
No diaphyses, epiphyses.
Sandwich of spongy between compact bone.
Flat bones
Compact bone that surrounds spongy bone center; similar to structure of epiphyses of long bones.
Short and irregular bones.
air-filled spaces lined by mucous membranes.
sinuses
Takes place in embryonic connective tissue membrane.
Intramembranous ossification
Takes place in cartilage.
Endochondral ossification
Takes place in connective tissue membrane formed from embryonic mesenchyme.
Intramembranous Ossification
locations in membrane where ossification begins.
Centers of ossification
large membrane-covered spaces between developing skull bones; unossified.
Fontanels
Some embryonic mesenchymal cells in the connective tissue membrane differentiate into osteochondral progenitor cells which then form osteoblasts.
Osteoblast formation
Additional osteoblasts gather on the surfaces of the trabeculae and produce more bone, thereby causing the trabeculae to become larger and longer.
Spongy bone formation
forms as the trabeculae join together in an interconnected network of trabeculae separated by spaces.
Spongy bone
Cells within the spaces of the spongy bone specialize to form red bone marrow, and cells surrounding the developing bone specialize to form the periosteum.
Compact bone formation
converts woven bone to lamellar bone and contributes to the final shape of the bone.
Remodeling
Forms bones of the base of the skull, part of the mandible, epiphyses of the clavicles, and most of remaining bones of skeletal system.
Endochondral Ossification
formation begins at end of fourth week of development.
Cartilage
Embryonic mesenchyme cells aggregate in regions of future bone formation.
Cartilage Model Formation
As the chondroblasts are surrounded by cartilage matrix, they become?
chondrocytes
is continuous with tissue that will become the joint capsule later in development.
perichondrium
When blood vessels invade the perichondrium surrounding the cartilage model, osteochondral progenitor cells within the perichondrium become osteoblasts that produce compact bone on the surface of the cartilage model, forming a?
Bone Collar Formation
Blood vessels grow into the enlarged lacunae of the calcified cartilage.
Primary Ossification Center Formation
forms as osteoblasts produce bone on the surface of the calcified cartilage.
primary ossification center
These centers are created in the epiphyses by osteoblasts that migrate into the epiphyses.
Secondary Ossification Center Formation
appear during early fetal development, whereas secondary ossification appear later.
Primary ossification centers
In mature bone, spongy and compact bone are fully developed, and the epiphyseal plate has become the epiphyseal line.
Adult bone
epiphyseal plate is ossified becoming the epiphyseal line. Between 12 and 25 years of age.
Closure of epiphyseal plate
does not ossify and persists through life
Articular cartilage
contain slowly dividing chondrocytes.
Zone of resting cartilage
New cartilage is produced on the. epiphyseal side of the plate as the chondrocytes divide and form stacks of cells.
Zone of proliferation
Chondrocytes mature and enlarge.
Zone of hypertrophy
Matrix is calcified, and chondrocytes die.
Zone of calcification
The cartilage on the diaphyseal side of the plate is replaced by bone.
Ossified bone
is one of the most critical factors of bone strength.
Bone width
Lack of calcium, protein and other nutrients during growth and development can cause bones to be small.
Nutrition
Necessary for absorption of calcium from intestines.
Can be ingested or manufactured in the body.
Vitamin D
lack of vitamin D during childhood.
Rickets
During this process, cells move into the damaged area and form a callus, which is replaced by bone.
Bone Repair
lack of vitamin D during adulthood leading to softening of bones.
Osteomalacia
Necessary for collagen synthesis by osteoblasts.
Vitamin C
deficiency of vitamin C.
Scurvy
Lack of ___ also causes wounds not to heal, teeth to fall out?
vitamin C
Lack of ___ also causes wounds not to heal, teeth to fall out?
vitamin C
from anterior pituitary. Stimulates interstitial cartilage growth and appositional bone growth.
Growth hormone
required for growth of all tissues.
Thyroid hormone
such as estrogen and testosterone. Cause growth at puberty, but also cause closure of the epiphyseal plates and the cessation of growth.
Reproductive hormones
excessive growth hormone secretion during growing years.
Gigantism
insufficient growth hormone during growing years.
Dwarfism
bones become thick or develop abnormal spurs, or projections that can interfere with normal function.
Too much is deposited
weakens the bones & making them susceptible to fracture.
Too little bone formation / too much bone removal
Increased stress causes bone to increase in strength.
Mechanical Stress and Bone Strength
Traumatic, disease (pathological), at location of an implant on the bone (periprosthetic)
Mechanism of fracture
Closed versus open
Soft-tissue damage
Linear, spiral, avulsion, stress, compression.
Fracture pattern
Incomplete, complete, comminuted.
Number of fragments in the fractured bone.
Greenstick and epiphyseal fractures.
Age-specific
Broken bone causes bleeding and a blood clot forms
Hematoma formation
A fibrous network forms between two fragments
Callus formation
Cartilage model forms first then osteoblasts enter the callus and form spongy bone (This continues for 4-6 weeks after injury)
Callus ossification
Spongy bone is slowly remodeled to form compact and spongy bone.
Bone remodeling
Three hormones control blood calcium levels:
• Parathyroid hormone (PTH).
• Calcitriol (biologically active form of vitamin D3).
• Calcitonin.
• Increases blood calcium by stimulating intestinal absorption of calcium.
• Derived from vitamin D3.
Calcitriol
Lowers blood calcium by inhibiting osteoclast activity.
Calcitonin
is porous bones, a loss of bone matrix.
Osteoporosis
