Bones & Bone tissue

Skeletal system

cartilage, bones, ligament, and tendons

Functions of skeletal

Support - bones are framework, cartilage provides support with certain structures (nose), ligaments hold bones together

Protection - skull, ribcage, vertebrae

Movement - tendons, shape of bones at joints determines type of movement

Functions of skeletal

Storage - minerals (Ca) and adipose tissue (fat)

Blood cell production - occurs in red bone marrow cavities of certain bones

Cartilage

type of connective tissue - therefore composed of cells and extracellular matrix

avascular - NO BLOOD VESSELS IN THIS TISSUE

Three types: hyaline, fibro…, elastic

Hyaline cartilage

Location: ends of long bones, ribs, growth plates, trachea, bronchi, nose, and embryonic skeleton

Function: smooth surface for joints, support (for airways like trachea)

Light pink, scattered nuclei surrounded by extracellular matrix (gel & collagen fibers)

Fibrocartilage

Locations: pubic symphysis, intervertebral discs, labrum, menisci

Functions: support, shock absorption

Purple, organized nuclei in lines surrounded by collagen fibers (organization=strength)

Elastic cartilage

Locations: epiglottis, ear

Functions: support with flexibility

Purple, chondrocytes packed together, extracellular matrix of collagen and elastic fibers

Bone

Classified according to shape (long, short, flat, or irregular). Type of connective tissue that contains osteoblasts, osteocytes, and osteoclasts

Long bones

longer than wide (name reflects shape rather than overall size)

Examples: femur, humerus, tibia

Short bones

cube like bones of wrist and ankle

Flat bones

sternum, ribs, certain bones of skull

Irregular bones

all other bones (vertebrae, hip bones)

Structure of long bones

diaphysis, epiphyses, epiphyseal lines, periosteum, and endosteum

Diaphysis

shaft (long axis) of a long bone. Composed primarily of compact bone

Contains the marrow cavity (filled with yellow bone marrow)

Epiphyses

ends of the long bone (joint surface). Composed primarily of spongy bone.

Covered with articular cartilage (aka hyaline cartilage) to provide a smooth surface, reduce friction, and absorb shock

Epiphyseal lines (metaphysis)

located between the diaphysis and epiphyses - former growth plates

Periosteum

Connective tissue membrane which surrounds the external surface of the diaphysis

Endosteum

Connective tissue membrane which surrounds the internal surfaces of the bone, in marrow cavity

Osteoblasts

make bone (secrete osteoid) → turn into osteocytes “Builder”

Osteocytes

mature bone cells, maintain bone

Cell body of osteocytes sit in lacunae

Cell processes of osteocytes sit in canaliculi

Osteoclasts

Breakdown bone, multinucleate

Extracellular matrix of bone

primarily composed of osteoid and hydroxyapatites

Osteoid

Secreted by osteoblasts, accounts for bone strength due to collagen fibers

Hydroxyapatites

account for hardness of bone

Compact bone

external layer of bone, composed of osteons

Osteons

Vascular and innervated

tube of bone matrix formed by rings called concentric lamellae

Contains a central canal (housing blood vessels and nerves)

Concentric lamellae

cell bodies of osteocytes are in lacunae between ___

Osteocytes pass oxygen and nutrients to each other through the cell processes (in canaliculi) → gap junctions

Central canal

Also called Haversian - houses blood vessels and nerves

Connected to each other by perforating canals (aka volkmohn’s)

Spongy (cancellous) bone

surrounded by compact bone

NO OSTEONS!!!

composed of plates of bone called trabeculae (align along lines of stress)

Mechanical stress

Remodels spongy bone as a result of muscle pull and gravity

keeps bones strong (ex: exercise), the anatomy of bone reflects the stresses it encounters

trabeculae

plates of bone that compose spongy bone

Align along lines of stress