Bone: Introduction and Anatomy

What is the skeletal system composed of

Bones, Cartilages, and Ligaments

Cartilage

Is the forerunner/model of most bones and covers many joint surfaces of mature bones

What are the most durable remains of a once-living body

Bones and teeth

What do ligaments do

Hold bones together at joints

What do tendons do

Attach muscle to bone

What do all skeletal cartilages contain

Chondrocytes in lacunae and extracellular matrix

What are the three types of skeletal cartilage

Hyaline, Elastic, and Fibrocartilage

What is the function of hyaline cartilage

Provide support, flexibility, and resilience

What is hyaline cartilage made out of

Thin collagen fibers

What is the most abundant type of cartilage

Hyaline

Where is hyaline cartilage found

Articular (end of bone) cartilage, costal (rib) cartilage, respiratory (larynx, etc.) cartilage, and nasal cartilage

What is elastic cartilage made of

Thin collagen fibers and elastic fibers

Where is elastic cartilage found

External ear and Epiglottis

What is fibrocartilage made of

Thick bundles of collagen fibers

What cartilage has the greatest tensile strength

Fibrocartilage

Where fibrocartilage found

Menisci of knee and Vertebral discs

What are the 8 functions of the skeleton

Support, protection, movement, electrolyte balance (mineral storarge), acid-base balance, triglyceride storage, and hormone production

Functions of the skeleton: support

Limb bones and vertebrae support the body; jaw bones support teeth; some bones support viscera

Functions of the skeleton: Protection

Protects the brain, spinal cord, heart, lungs, and more

Functions of the skeleton: Movement

Limb movement, breathing, other movement depending on bone

Functions of the skeleton: Electrolyte balance (mineral storage)

Manages Calcium and phosphate levels

Functions of the skeleton: Acid-Base balance

Buffers blood against large pH changes by altering phosphate and carbonate salt levels

Functions of the skeleton: Blood cell formation (hematopoiesis)

Red bone marrow is the chief producer of blood cells

Functions of the skeleton: Triglyceride storage

Adipose tissues stores in the medullary cavity of long bones

Functions of the skeleton: Hormone Production

Osteocalcin regulates bone formation

What are bones

Organs

Why are bones considered organs

They contain many types of tissues

Bone (osseous tissue), nervous tissue, cartilage, fibrous connective tissue, muscle and epithelial cells in blood vessels

What are the three levels of bone strucutre

Gross anatomy, microscopic anatomy, and chemical

What are the two bone textures

Compact and spongy

What is the skeleton divided up by weight

3/4 is compact and 1/4 is spongy

Compact bone

Type of bone that has a dense outer layer; smooth and solid

Spongy Bone

Type of bone that is a honeycomb of flat pieces of bone deep to compact bone called trabeculae

Where is spongy bone found

In the center of the ends and the center of the shafts of long bones and in the middle of nearly all other bones

What is spongy bone covered with

Compact bone

What does spongy bone do

Absorbs shock

What are the marrow spaces of spongy bone lined with

Endosteum

What is the structure of short, irregular, and flat bones

They have thin plates of spongy bone covered by compact bone

The plates are sandwiched between connective tissue membranes known as

• Periosteum and endosteum

They don’t have shafts or epiphyses

There is no marrow cavity so bone marrow is found throughout spongy bone

Hyaline cartilage covers the articular surfaces

What are the features of long bones

Diaphysis, marrow cavity, and epiphyses

Diaphysis of long bone

Shaft that provides leverage

Marrow Cavity/ Medullary Cavity

Space in the diaphysis of long bone that contains bone marrow

Epiphyses of long bone

Enlarged ends of long bone

What is between the diaphysis and epiphyses

The epiphyseal line

What does the epiphyses do

Strengthens joints and anchors ligaments and tendons

What is the epiphyseal line

A remnant of childhood bone growth at the epiphyseal plate. In adults it is a bony scar that marks where the growth plate used to be

Articular Cartilage covers what

Articular Surfaces

Epiphyseal plate (growth plate)

An area of hyaline cartilage that separates the epiphyses and diaphysis of children’s bones. It enables growth in length

What are the general features of long bones

Epiphyses and Diaphysis, Compact and spongy bone, Marrow/Medullary Cavity, Articular Cartilage, Periosteum

Articular Cartilage

Layer of hyaline cartilage that covers joint surface; allows joints to move more freely

Nutrient Foramina

Minute holes in bone surface that allows blood vessels to penetrate

Periosteum

External Sheath covering most of bone

What are the layers of the periosteum

Outer Fibrous layer of collagen

• Some fivers continuous with tendons

• Perforating fibers-Penetrate into bone matrix

Inner osteogenic later of bone-forming cells

• Important to bone growth and healing fractures

Endosteum

Thin layer of reticular connective tissue lining marrow cavity

What cells does endosteum contain

Cells that dissolve osseous tissue and other cells that deposit osseous tissue

Bone is a connective tissue that consitis of

Cells, fibers, and ground substance

What are the four major cell types of bone

Osteogenic cells, Osteoblast, Osteocytes, Osteoclast

What is another name for osteogenic cells

Osteoprogenitor cells

Osteogenic cells

Mitotically active stem cells in periosteum and endosteum; multiply continuously and give rise to most other bone cell types

What do osteogenic cells arise from

Embryonic mesenchyme

When stimulated what happens to osteogenic cells

They differentiate into most other bone cell types, but some persist as osteogenic cells

Osteoblast

Bone forming cells

What do osteoblast secrete

An unmineralized bone matrix or osteoid

What makes up 90% of bone protein

Collagen

What is the function of osteoblast

They synthesize soft organic matter of matrix which then hardens by mineral deposition (osteogenesis)

Are osteoblast actively miotic

Yes they are actively miotic

What stimulates osteogenic cells to multiply rapidly and increate the number of osteoblast which reinforces bone

Stress

What hormone do osteoblast secrete

Osteocalcin

What does osteocalcin do

Stimulates insulin secretion of pancreas; increases insulin sensitivity in adipocytes which limits the growth of adipose tissue

Osteocytes

Mature bone cells in lacunae.

What are the former osteoblast that have become trapped in the matrix they deposited

Osteocytes

Lacunae

Tiny cavities where osteocytes reside

Canaliculi

Little hairlike channels that connect Lacunae to each other and the cental canal

Cytoplasmic processes of osteocytes reach into canaliculi and do what

Contact process of neighboring cells using gap junctions

What do gap junctions allow

Passage of nutrients, waste, and signals

What is the function of an osteocyte

Monitor and maintain bone matrix by acting as stress or strain sensors.

They respond to and communicate mechanical stimuli to osteoblast and osteoclast so bine remodeling can occur

Osteoclast

Bone destroying cells

What are osteoclast derived from

Hematopoietic stem cells that become macrophages

How are osteoclast cells formed

They are very large cells formed from the fusion of several stem cells. Results in giant multinucleate cells for bone resorption

What happens when osteoclast are active

They rest in the resorption bay and have a ruffled border

What does the ruffled border of the osteoclast do

Increases surface area for enzyme degradation of bone and seals off area from surrounding matrix

Resorption bays

Pits in bone surface

Osteolysis is which part of bone remodeiling

Dissolving bone

Where does organic matter come from

It is Synthesized by osteoblast

Examples of organic matter

Collagen, Glycosaminoglycans, proteoglycans, and glycoproteins (carbohydrate-protein complexes)

What cells are included in the organic components of bone

Osteogenic cells, Osteoblast, Osteocytes, bone- lining cells, osteoid, and osteoclast

Osteoid is made of

Ground substance (proteoglycans and glycoproteins), Collagen fibers

What makes up 1/3 of organic bone matrix secreted by osteoblast

Osteoid

Osteoid contributes to what

Structure by providing tensile strength and flexibility

What causes resilience of bone

Sacrificial bonds in or between collagen molecules

What do sacrificial bonds allow

They stretch and break easily on impact to dissipate energy and prevent fracture

If there is no additional trauma the bonds reform.

What makes up inorganic matter

85% is hydroxyapatite (crystalized calcium phosphate salt)

10% is calcium carbonate

and other minerals (fluoride, sodium, potassium, magnesium)

Hydroxyapatites

Mineral salts

What makes up 65% of bone by mass

Hydroxyapatites

What is hydroaxpiates mainy made from

Tiny calcium phosphate crystals in and around collagen fibers

What is hydroxyapatite responsible for

Hardness and resistance to compression

Bone is a composite material meaninf

It is a combination of a ceramic and a polymer

What is the ceramic part of bone

Hydroxyapatite and other minerals

What is the polymer part of bone

Collagen

What does the ceramic part of bone allow

It allows the bone to support body weight without sagging

What does the polymer part of bone allow

Some flexability

Rickets is a disease causes by

A mineral deficiency and results in soft, deformed bones