What are the three types of skeletal cartilage?

• Hyaline cartilage: provides support, flexibility and resilience. Also is the most abundant type
• Elastic cartilage: similar to hyaline cartilage, but contains elastic fibers
• Fibrocartilage: collage fibers-have great tensile strength

Skeletal cartilage

• contain no blood vessels or nerves
• dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage

What ways cartilage can grow?

1. appositional growth: cells secrete matrix against the external face of existing cartilage
2. interstital growth: chondrocytes divide and secrete new matrix, expanding cartilage from within
3. under certain conditions calcification of cartilage can occur during normal bone growth and old age

Human skeleton are divided in what two groups?

1. axial skeleton: forms the long axis of the body and includes the bones of the skull, vertebral column and rib cage
2. appendicular skeleton: consists of the bones of the upper and lower limbs and the girdles (shoulder and hip bones) that attch the limbs to the axial skeleton

Classification of bones by shape:

• Long bones: longer than they are wide
• Short bones: cube-shaped bones (in wrist and ankle), sesamoid bones (within tendons; example: patella)
• Flat bones: thin, flat, slightly curved
• Irregular bones: complicated shaped

What are the functions of bone?

• support: for the body and soft organs
• protection: for brain, spinal cord and vital organs
• movement: levers for muscle action
• storage: minerals (calcium and phosphorus) and growth factors
• blood cell formation (hematopoiesis) in marrow cavities
• triglyceride (energy) storage in bone cavities

In bone markings, what do projections (bulges), depressions and holes serve as?

• site of attachment for muscle, ligaments and tendons
• joint surfaces
• conduits for blood vessels and nerves

Name the types of projection (bulges) bone marking

1. tuberosity: rounded projection
2. crest: narrow, prominent ridge
3. trochanter: large, blunt, irregular surface
4. line: narrow ridge of bone
5. tubercle: small rounded projection
6. epicondyle: raised area above a condyle
7. spine: sharp, slender projection
8. process: any bony prominence

What are the projections (bulges) bone marking that help to form joints?

• head: bony expansion carried on a narrow neck
• facet: smooth, nearly flat articular surface
• condyle: rounded articular projection
• ramus: arm-like bar

Name the depression and opening bone markings

1. meatus: canal-like passageway
2. sinus: cavity within a bone
3. fossa: shallow, basin-like depression
4. groove: furrow
5. fissue: narrow, slit-like opening
6. foramen: round or oval opening through a bone

Two types of bone structures:

1. compact bone: dense outer layer
2. spongy (cancellous) bone: honeycomb of trabeculae

Structure of long bone: (diaphysis)

• compact collar bone surrounds medullary (marrow) cavity
• medullary cavity in adults contains fat (yellow marrow)

Structure of long bone: (epiphyses)

• expanded ends
• spongy bone interior
• epiphyseal line (remnant of growth plate)
• articular (hyaline) cartilage on joint surfaces

Membrane of bone: periosteum

• outer fibrous layer 
• inner osteogenic layer: (osteoblast - bone forming cell) (osteocyte - bone destroying cell) (osteogenic cell - stem cells)
• nerve fiber, nutrient blood vessels and lymphatic vessels enter the bone via nutrient foramina
• secured to underlying bone by Sharpey's fibers

Membrane of bone: endosteum

• delicate membrane on internal surfaces of bone
• contains osteoblasts and osteocytes

Structure of short, irregular and flat bones

• periosteum - covered compact bone on the outside
• endosteum - covered spongy bone within
• spongy bone called dipole in flat bone
• bone marrow between the trabeculae

Location of hematopoietic tissue (red marrow)

1. red marrow cavities of adults

• trabecular cavities of the heads of the femur and humerus
• trabecular cavities of the dipole of flat bones

2. red marrow of newborn infants

• medullary cavities and all spaces in spongy bone

Osteocytes

• mature bone cells

Osteoclasts

• cells that break down (resorb) bone matrix

Osteogenic (osteoprogenitor) cells

• stem cells in periosteum and endosteum that give rise to osteoblasts

Osteoblasts

• bone forming cell

Compact bone: perforating (Volkmann's) canals

• at right angle to the central canal
• connects blood vessels and nerves of the periosteum and central canal

Compact bone: lacunae

• small cavities that contain osteocytes

Compact bone: canaliculi

• hair-like canals that connect lacunae to each other and the central canal

Compact bone: lamellae

• weight-bearing
• column-like matirx tubes

Compact bone: central (Haversian) canal

• contains blood vessels and nerves

Spongy bone: trabeculae

• align along lines of stress
• no osteons
• contain irregularly arranged lamellae, osteocytes, canaliculi
• capillaries in endosteum supply nutrients

Chemical composition of bone: organic

1. osteogenic cells, osteoblasts, osteocytes, osteoclasts

2. osteoid: organic bone matrix secreted by osteoblasts

• ground substance (proteoglycans, glycoproteins)
• collagen fibers: provide tensile strength and flexibility

Chemical composition of bone: inorganic

   1. hydroxyapatites (mineral salts)

• 65% of bone by mass
• mainly calcium phosphate crystals
• responsible for hardness and resistance to compression