BonesStructure and Function

Skeletal System Organization System = Skeletal

Organs = Bones Each bone is an

individual organ Work together as joints

(considered later)

Tissues = Connective Compact Bone Spongy (cancellous)

Bone Hyaline Cartilage

Skeletal System – Macroscopic Anatomy

Axial Skeleton Head Vertebrae Ribs Pelvic Girdle

Appendicular Skeleton Arms Legs

Bone Types

We will use long bones as our example.

Long Bone – Macroscopic AnatomyEpiphysis (end)

• covered with hyaline cartilage

• compact bone forms exterior

• spongy bone forms interior

• contains epiphyseal line/plate

Diaphysis (middle)• compact bone forms exterior

• center composed of the medullary cavity containing yellow or red marrow

Fig 7.1

Long Bone – Macroscopic Anatomy

Fig 7.2

Long Bone – Microscopic Anatomy Osteon =

circular structure organized around blood vessels

Osteocyte = bone cells

Bone matrix = hard calcium-based material between cells

Fig 7.3

Bone – Tissue Types Bones and joints are composed primarily of

connective tissue Connective tissue is organized by type of

extracellular matrix

Connective Tissue

Specialized

Connective Tissue

Bone

Spongy Bone

Compact bone

Blood Cartilage

Hyaline Elastic Fibro

Connective Tissue Proper

Loose

Reticular Adipose Areolar

Dense

Tissue Types – Compact BoneFunctions

Hard and provides stability, framework, protection

Structure Matrix has hard mineral structure, based on calcium

Cells and matrix are arranged in regular, concentric pattern

Compact Bone

Tissue Types – Spongy BoneFunctions

Lightens total bone weight and provides space for bone marrow

Structure Matrix is softer mineral, less organized and less of it

Empty spaces between matrix structure are filled with bone marrow

Spongy (cancellous) Bone

Tissue Types – Hyaline CartilageFunctions

Provides soft and smooth covering to end of bone (articular surface)

Helps provide smooth and easy movement between bones (at joints)

Provides the starting material for new bone growth

Structure Matrix is spongy (like jello)

and evenly distributed between the cells

Cells (chrondocytes) are found in pairs within capsules called lacunae Hyaline Cartilage

Bone PhysiologyLiving bones perform the following processes:

Formation Starts as an embryo, continues through fetal

development and after birth

Growth Occurs from before birth through maturity

Remodel Old matrix is removed and replaced with new matrix

Repair Damaged bones will heal and return to normal

structure

Bone Physiology – Formation Fetal bones are made of hyaline cartilage As cartilage cells die, they are replaced with spongy bone in

diaphysis After birth, spongy bone invades diaphysis Compact bone replaces spongy bone in diaphysis Hyaline cartilage remains on epiphyseal surface and in growth plate

Fig 7.5

Bone Physiology – Growth Bones grow in length at the

epiphyseal plate – hyaline cartilage in the epiphysis

Cartilage cells divide causing the epiphyseal plate (and bone) to grow

Cartilage cells die and are replaced by spongy bone

As adolescence ends, the growth plate decreases in size and eventually is replaced by bone

bone growth video

Bone Physiology – Growth

Epiphyseal (Growth) Plate

Bone Physiology – Growth

Bone Anatomy and Physiology Lab – 2A

Cow = more compact bone; less hyaline cartilage; no active growth plate (bone not cartilage); yellow marrow

Calf = less compact bone; more hyaline cartilage; active growth plate (cartilage, not bone); red marrow

Bone Anatomy and Physiology Lab – 2A

Bone Physiology - Repair Hemotoma, a mass of

clotted blood, forms at the fracture site.

A fibrous callus forms, and cartilage matrix is secreted.

Spongy bone forms to replace cartilage.

Bone remodeling occurs to remove excess material and replace compact bone.

Bone Physiology - Remodeling Bone matrix is inorganic and

breaks down over time

Specific bone cells (osteoclasts) remove old, broken matrix

Other bone cells (osteoblasts) re-make/deposit new matrix

The entire skeleton is re-modeled every 7-10 years

Remodeling slows with age, elderly people have thinner bones and are more susceptible to broken bones as a result