Structure and Function Bones Structure 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

We will use long bones as our example. Bone Types We will use long bones as our example.

Long Bone – Macroscopic Anatomy Epiphysis (end) covered with hyaline cartilage compact bone forms exterior spongy bone forms interior contains epiphyseal line/plate Diaphysis (middle) 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

Specialized Connective Tissue Connective Tissue Proper 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 Bone Functions 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 Bone Functions 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 Cartilage Functions 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 Physiology Living 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 17

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 18

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