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