Chapter 6 - bones and skeletal tissue

Types of Cartilages

1. Hyaline

2. Elastic

3. Fibrocartilage

Contains:

• Chondrocytes

• Abundant extracellular matrix

• Lacuna

Hyaline Cartilage

• most abundant

• resists compression due to: large amount of H₂O

• inside matrix will only be collagen fibers

• found in:

  • articular cartilage

  • sternal cartilage

  • holds airways open in respiratory system

Elastic Cartilage

• matrix contains elastic and collagen fibers

• function: tolerate repeated bending

• found in:

  • epiglottis

  • ear

  • auditory tube

Fibrocartilage

• contains thick collagen fibers that surround the chondrocyte

  • dense irregular CT

• function to resist compression and pulling forces

• found in the:

  • intervertebral disc

  • articular discs between joints

Functions of Bones

• support

• movement

• protection

• mineral storage

• blood cell and fat storage

• energy metabolism

Bone Classification

• long

• short

  • sesamoid

• flat

• irregular

• sutural

Long Bone

humerus

Short Bone

carpals and tarsals

Flat

scapula

Irregular

irregular bone (vertebrae)

Tuberosity

large rounded projection; may be roughened

Crest

narrow ridge of bone; usually prominent

Trochanter

very large, blunt, irregularly shaped process

Line

narrow ridge of bone; less prominent than a crest

Tubercle

small rounded projection or process

Epicondyle

raised area on or above a condyle

Spine

sharp, slender, often pointed projection

Process

any bony prominence

Head

bony expansion carried on a narrow neck

Facet

smooth, nearly flat articular surface

Condyle

rounded articular projection, often articulates with a corresponding fossa

Foramen

round or oval opening through a bone

Groove

furrow

Fissure

narrow, slitlike opening

Notch

indentation at the edge of a structure

Fossa

shallow basin like depression in a bone, often serving as an articular surface

Meatus

canal-like passageway

Sinus

cavity within a bone, filled with air and lined with mucous membrane

Compact Bone

external layer

Spongy Bone

internal layer

Gross Anatomy of the Long Bone

• diaphysis

• epiphysis

• epiphyseal line

• periosteum

  • dense irregular connective tissue

  • osteogenic layer

    • osteoblasts/osteoclasts

• articular cartilage

• endosteum

Flat Bones

• compact bone

• spongy bone = diploe

Organic Bone Composition

• contains mostly collagen

• produced by osteoblasts

• contributes to: the flexibility and tensile strength that allow bone to resist bending and twisting

  • approx 35% of the bone weight is due to the organic composition

Inorganic (hydroxyapatites)

• calcium phosphate

• contributes to bone being hard and resisting compression forces

Bone Cell Types

• osteogenic cell

• osteoblasts

  • osteoid

• osteocyte

• osteoclast

  • pth role

Histology of Compact Bone

• osteon (haversian system)

• lamellae

• central canal (haversian canal)

• perforating canals (volkmann’s canal)

• lucunae

• canaliculi

• circumferential lamellae

Bone Ossification

• beings at 8th week of embryo development

• intramembranous ossification

  • bone formed from fibrous membrane

  • skull and clavicle

• endochondral ossification

  • bone from hyaline cartilage replaced

Endochondral Ossification (1st Step)

• starts as cartilage model

• perichondrium is invaded by blood vessels to form periosteum

• osteoblasts in periosteum form bone collar

Endochondral Ossification (2nd Step)

• cartilage in the middle of the diaphysis hardens leaving a cavity

Endochondral Ossification (3rd Step)

• periosteal bud invades cavity

• trabeculae/spongy bone formed due to osteoblast activity

• primary ossification center

Endochondral Ossification (4th Step)

• diaphysis continues to grow

• medullary cavity formed

• after birth

  • epiphysis becomes spongy bones when bud enters the epiphysis

  • secondary ossification centers

Endochondral Ossification (5th Step)

• epiphysis completes ossification

• hyaline cartilage only at surfaces of epiphysis and the epiphyseal plate

Interstitial Bone Growth

• bone will continue to grow in length as long as cartilage will equal bone conversion

• puberty

Appositional Bone Growth

• at periosteum

  • osteoblasts

• at endosteum

  • osteoclasts

Comminuted Fracture

• bone fragments into three or more pieces

• particularly common in the aged, whose bones are more brittle

Compression Fracture

• bone is crushed

• common in porous bones (i.e., osteoporotic bones) subjected to extreme trauma, as in a fall

Spiral Fracture

• ragged break occurs when excessive twisting forces are applied to a bone

• common sports fracture

Epiphyseal Fracture

• epiphysis separates from the diaphysis along the epiphyseal plate

• tends to occur where cartilage cells are dying and calcification of the matrix is occurring

Depressed Fracture

• broken bone portion is pressed inward

• typical of skull fracture

Greenstick Fracture

• bone breaks incompletely, much in the way a green twig breaks

• only one side of the shaft breaks; the other side bends

• common in children, whose bones have relatively more organic matrix and are flexible than those of adults

Osteoporosis

• due to low bone mass

• bones become porous and thinner

• most vulnerable at vertebral column and neck of femur

• who gets it? → women (65+), men (poor diet), asian, caucasian

• why do you get it? → women (low exertion), men (poor diet)

• how to detect it? → dexa scan

• how to treat? → medication, injection, resisted exercise

paget’s disease

• chronic bone disease

• excessive rates of bone deposition and bone resabsorption

  • immature bone

• later stages bones become thick

  • not life threatening

Rickets

• form of osteomalacia but in children

• bones not fully calcified so becomes soft

• due to:

  • low calcium phosphate

  • low amounts of Vitamin D