Chapter 6
Periosteum
a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.
greenstick fracture
a partial break in which only one side breaks and the other side bends a. Occurs only in children who have bones with more organic material
bones flexibility depends on
collagen fibers
what part of bone is spongey
epiphysis and metaphysis
components of extracellular matrix
15% water 30% collagen fibers 55% crystallized mineral salts
Epiphysis
End of a long bone
Fracture and Bone Repair
- The reactive phase is an early inflammatory phase. (MOST PAINFUL) - The reparative phase includes formation of a fibrocartilaginous callus first and a bony callus second. (endocondral ossification) - The bone remodeling phase is the last step as the bony callus is remodeled. - The healed fracture, stronger than before because there is so much collagen
Where is spongy bone found in short flat sesmoid and irregularly shaped bones? Long bones?
- interior bones - long bones: epiphysis
what type of bones are made through intramembraneous ossification?
-flat bones - facial bones -mandible - medial part of clavicle -soft part of skull
steps of endochondral ossification
1. Most bones develop from a carilage model, mesenchyme develops into chondroblasts - growth of cartilage model by division on chondrocytes - development of primary ossification center - development of medullary cavity - development of secondary centers - formation of articular cartilage and epiphyseal plate
4 parts of ossification?
1. initial formation of bones in an embryo and fetus 2. growth of bones during infancy, childhood, and adolescence 3. remodeling of bone 4. repair of fractures
facts that affect bone growth and bone remodeling
1. minerals 2. vitamins 3. hormones
4 zones of epiphyseal plate
1. zone of resting cartilage 2. zone of proliferating cartilage 3. zone of hypertrophic cartilage 4. zone of calcified cartilage
i. Hemopoiesis: WBC, RBC, and platelet production ii. Red Bone marrow (Connective Tissue): consists of developing blood cells; adipocytes, fibroblasts, macrophages
Blood cell production
articular cartilage
Hyaline cartilage attached to articular bone surfaces
where are osteoprogenitor cells found
Located in periosteum and endosteum and canals within the bone that contain blood vessels
Calcitonin
Lowers blood calcium levels, deposition of calcium into bone
Metaphyses (long bone)
Narrow areas between diaphysis & Epiphysis
trabecular or cancellous bone
SPONGEY BONE less compact bone with high porosity; found in the ends of long bones and the vertebrae
osteoprogenitor cells
Stem cells derived from mesenchyme Produce cells that mature to become osteoblasts
what happens when u put bone in vinegar
becomes rubbery because it dissolves the mineral salts
When does the epiphyseal plate close?
between 18-25
the additions of minerals and collagen fibers to bone by osteoblasts
bone desposition
The ongoing replacement of old osseous tissue by new osseous tissue is
bone remodeling
The removal of minerals and collagen fibers from bone by osteoclasts
bone resorption
the removal of minerals and collagen fibers from bone by osteoclasts
bone resorption by osteoclasts
Osteoblasts
bone-forming cells that secrete the bone matrix
what causes the medullary cavity to form?
break down by osteoclasts
what do osteoblasts start (the process)
calcification
what happens when the mineral salts in the collagen fiber of the extracellular matrix crystallize
calcification
Calcium phosphate + calcium hydroxide
calcium hydroxyapatite
most abundant mineral salt in the in extracellular bone matrix
calcium phosphate
radiating from lacuna, fingerlike projections from the osteocytes
canaliculi
growth in length? results from what part of the bone?
cartilage continually grows and is replaced by bone. epiphyseal plate
medullary cavity
cavity within the shaft of the long bones filled with bone marrow
why does cartilage model grow?
cell division of chondrocytes
Osteoclasts are
cells that break down bone matrix
what type of cell is used in endochondrol ossification? what does it secrete?
chondroblasts, cartilage extracellular matrix
what do chondrobalasts become during the growth of the cartilage model?
chondrocytes that divide for interstitial growth
arranged around the entire outer and inner circumference of the shaft of a long bone
circumfental lamallae
What do osteoblasts secrete?
collagen and other organic compounds upon which bone is formed
what provides tensile strength in bones
collagen fibers
circular plates of mineralized extracellular matrix
concentric lamellae
bones hardness is due to
crystallized inorganic
what part of the bone is compact
diaphysis
where is the primary ossification center?
diaphysis
2. Closed (simple):
does not break through the skin
bone forms within hyaline cartilage that develops from mesenchyme
endochondrol ossification
Enter epiphyses between articular cartilage and epiphyseal plate and supple red bone marrow and bone tissue of the epiphyses
epiphyseal arteries
why do we need calcium?
exocytosis, neurotransmitter release, muscle contraction, blood clotting
colles
fracture of the distal end of the lateral leg bone (fibula), serious damage to the distal tibial articulation
pott fracture
fracture of the distal end of the lateral leg bone (fibula), serious damage to the distal tibial articulation
1. Periosteal cells differentiate into osteoblasts (that secrete the collagen fibers and other organic molecules that form bone extracellular matrix) 2. Osteoblasts become surrounded by extracellular matrix and develop into osteocytes àcreates bone ridges on either side of a periosteal blood vessel 3. The ridges slowly enlarge and create a groove for the periosteal blood vessel 4. Ridges fold together and fuse, the groove become a tunnel that encloses the blood vessel 5. Former periosteum becomes the endosteum that lines the tunnel 6. Osteoblasts in the endosteum deposit bone extracellular matrix, form new concentric lamellae 7. Concentric lamellae form inward toward the periosteal blood vessel 8. New osteon created 9. Osteoblasts under the periosteum deposit new circumfential lamellae, further inc. the thickness of bone as additional periosteal blood vessels become enclosed.
growth in thickness
What type of cartilage is articular cartilage?
hyaline cartilage
what type of cartilage is the epiphyseal plate?
hyaline cartilage
what is the cartilage model made of?what surrounds it?
hyaline cartilage, perichondrium
what type of growth is it when there is a growth of the cartilage model?
interstitial
The areas between neighboring osteons contain
interstitial lamellae
fragments of older osteons found between osteons
interstitial lamellae
simpler ossification
intramembraneous
bone forms directly within mesenchyme, which is arranged in sheet-like layers that resemble membranes
intramembranous ossification
small spaces in between concentric lamallae
lacuna
what happens when the chondrocytes die?
leave spaces called lacunae
enter the metaphyseses of the Long bone and, together with the nutrient artery, supply the red bone marrow and bone tissue of the metaphyseal
metaphyseal arteries
stores Ca and Ph that contribute to strength of bone. On demand bone release minerals into blood
mineral homeostasis
skeletal muscles that are attached to bones pull on bones when they contract and produce movement
movement
Near the center of the diaphysis, the ------- and vein pass through a hole in the compact bone called the nutrient ________.
nutrient artery, nutrient foramen
steps of intramembranous ossification
o Development of Ossification Center o Calcification o Formation of Trabeculae o Development of the periosteum
5. Impacted:
one end of the fractured bone is forcefully driven into the interior of the other
the process by which bone forms
ossification
what are aligned along the trabecule of new bone
osteoblasts
does PTH stimulate osteoblasts or osteoclasts?
osteoclasts
Mature bones cells are known as _______,
osteocytes
what do osteoblasts become
osteocytes
What do lacunae contain?
osteocytes (mature bone cells)
repeating structural unit of bone
osteon
what is the only bone cell that undergoes cell division
osteoprogenitor cell
four types of cells in bone tissue
osteoprogenitor cells osteoblasts osteocytes osteoclasts
horomone that regulates exchange of calcium?
parathyroid hormone
how is the periosteum attached to underlying bone?
perforating fibers
thick bundles of collagen that extend from the periosteum into the bone extracellular matrix
perforating fibers
small arteries accompanied by nerves, enter the diaphysis through many perforating canals and supply the periosteum and outer part of the compact bone
periosteal arteries
what cleans up the dead or damaged tissue in reactive phase?
phagocytes and osteoclasts
What does PTH increase?
production of cyclic AMP
protects most important internal organs from injury
protection
when is there a fracture hemotoma?
reactive phase
Why is there swelling during reactive phase?
response to dead bone cells that produce additional cellular debris
Diaphysis
shaft of a long bone
which type of bone is located on lines of stress
spongey
bones tissue that doesn't contain ostoens
spongey bone
a series of microscopic fissures in bone that forms without any evidence of injury to other tissues
stress fracture
structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles
structure
Functions of the skeletal system
support, protection, movement, mineral homeostsis, blood cell production, trigylercide storage,
what is the resistance to being torn apart
tensile strength
3. Comminuted:
the bone is splintered, crushed, or broken into pieces at the site of impact, smaller bone fragments lie between the two main fragments
1. Open (Compound):
the broken ends of bone protrude through the skin
arrangement of lamallae In spongey bone
trabeculae
storage of yellow bone marrow
triglyceride storage
how are osteoblasts formed
when osteoblasts get trapped in the extracellular matrix
does trabeculae have concentric lamellae
yes
a. Only a few cells thick b. Mostly dead chondrocytes due to the calcified matrix around them c. Osteoclasts dissolve the calcified cartilage d. Osteoblasts and capillaries from diaphysis invade the area i. Lay down extracellular matrix ii. Replace the calcified cartilage through endochondral ossification (replacement of cartilage by bone) iii. This become the new part of the diaphysis
zone of calcified cartilage
a. Layer consists of large, maturing chondrocytes arranged in columns
zone of hypertrophic cartilage
a. Slightly larger chondrocytes, arranged like stacks of coins b. Chondrocytes undergo interstitial growth as they divide and secrete extracellular matrix c. These chondrocytes divide in order to replace those that die at the diaphyseal side of the epiphyseal plate
zone of proliferating cartilage
- Layer closest to end of epiphysis - Resting cells; anchor epiphyseal plate to epiphysis - scattered chondrocytes
zone of resting cartilage