Functions

1) Support/Movement

2) Protection

3) Storage of inorganic (mineral) salts

4) Hemopoiesis of all types of blood cells

^-------Through red bone marrow.

Histology of Compact Bone Tissue

Matrix of tightly-packed osteons.

Osteons composed of concentric rings of bone matrix.  Concentric rings are called lamellae.

Osteocytes are in lacunae between lamellae.

Canaliculi are tiny canals which communicate between osteocytes and Osteonic Canals, which run through each osteon and contain blood and lymph vessels.

Histology of Cancellous (Spongy) Bone Tissue

Matrix consists of Trabeculae (bone bridges).

Spaces between the trabeculae are filled with myeloid tissue (red bone marrow.)

Dense Bone Tissue

Matrix consists of thin, flat sheets of bone tissue.

Located on the very outer surfaces of bone.

General Types of Bones

Long Bones

Short Bones

Irregular Bones

Flat Bones

Sesamoid Bones

Long Bones

Most complex anatomy.

Diaphysis(shaft) composed of compact bone tissue.  Contains Medullary Cavity filled with yellow bone marrow.  Covered by fibrous tissue called the Periosteum.

Epiphyses - ends composed of spongy bone tissue containing red bone marrow.

Epiphyses are covered with articular cartilage.

Short Bones 

(Examples)

Carpals, Tarsals

Irregular Bones

(Examples)

Vertebrae (Atlas, Axis)

Flat Bones

(Examples)

Cranial bones, sternum, scapulae, ribs, pelvis

Sesamoid Bones

Found in tendons for support.

EX: Patellae (kneecaps) in patellar tendons.

Bone Development/Growth Overview

Bone Development takes 25-26 years.

Pre-bone tissues develop in the embryo by the 6-8th week.

Hyaline Cartilages ossify by endochondral ossification.

Fibrous membranes ossify by intramembranous ossification.

Bone Development Cells

Osteoblasts produce bone tissue matrix.  Osteocytes are mature, inactive Osteoblasts. 

Osteoclasts are giant sized cells which resorb(dissolve) bone matrix to form spongy bone tissue and medullary cavities, shaping the bones.

(Ossification is not complete at birth. Fontanels ("soft spots") on the cranium illustrate this on the heads of infants.)

SKELETAL DEVELOPMENT

HORMONES

STH - Growth Hormone - Stimulates growth of epiphyseal cartilages (plates).

Thyroxin & PTH (Parathyroid Hormone)

Both stimulate osteoclast activity. (Resorption)

Calcitonin inhibits osteoclast activity.

Estrogen stimulates rapid skeletal growth; widens pelvis; inhibits osteoperosis.

Testosterone stimulates thickening of long bones.

STH

Growth Hormone - Stimulates growth of epiphyseal cartilages (plates).

Thyroxin & PTH (Parathyroid Hormone)

Both stimulate osteoclast activity. (Resorption)

Calcitonin

Inhibits osteoclast activity.

Estrogen

Stimulates rapid skeletal growth; widens pelvis; inhibits osteoperosis.

Testosterone

Stimulates thickening of long bones.

Fracture Healing

(Steps - Taking the bone from softer to harder)

1) Hematoma forms at fracture site.

2) Hematoma replaced by Dense White Fibrous connective tissue.

3) DWF tissue replaced by Fibrocartilage tissue.

4) Fibrocartilage tissue replaced by bone tissue.

Osteoporosis

Bone matrix resorption; weakening

Osteomyelitis

Bone infections.

Kyphosis

(Vertebral Curvature Abnormality)

Exaggerated posterior curvature of the thoracic vertebrae. (Hunchback)

Lordosis

(Vertebral Curvature Abnormality)

Exaggerated anterior

Scoliosis

(Vertebral Curvature Abnormality)

Lateral curvature of the vertebral column.

Synarthroses

Immovable, fibrous joints

EX: Cranial sutures, sacrum, pelvis.

Amphiarthroses

Slightly movable joints

EX: Articulating vertebrae (spine, etc.)

Cartilagenous (cartilage) joints, bound by ligaments and padded with cartilage. 

Diarthroses

Freely movable joints

EX: Many

Most complex design

Articulating cartilages, menisci, ligaments, synovial membranes.

Synovial Joints

Vitamins

A

C

D

A - Increases osteoclast activity

C - Stimulates osteoblasts to produce collagen protein for bone strength. (NOT HARDNESS)

D - Stimulates calcification (Deposition of calcium salts in bones for hardness.)