SKELETAL SYSTEM

Skeletal System

Accounts for approximately 20% of the body weight

Axial Skeleton, Appendicular Skeleton

Main divisions of skeletal system

Axial Skeleton

central core of the human body that consists of 80 bones along the body’s main axis to protect vital organs

Axial Skeleton

It forms the framework that supports your head, neck, and torso

Appendicular Skeleton

consists of 126 bones that form the upper and lower limbs, shoulder girdles, and pelvic girdle

Appendicular Skeleton

comprises the body’s appendages and the connection points linking them to the central trunk

Bones

Provide support, protection, movement, mineral storage, and blood cell production

Cartilages

Connective tissue that provides support and flexibility

Cartilages

Important during skeletal development

Tendons

Connect muscle to bone, Made up of dense regular connective tissue

Ligaments

Connect bone to another bone, Made up of dense regular connective ti

206 bones

how many bones in total

Support

Bones are suited for bearing weight and are the major supporting tissues of the body [Functions of the Skeletal System]

Support

Cartilage provides firm and flexible support within certain structures [Functions of the Skeletal System]

Support

Ligaments hold the bones together [Functions of the Skeletal System]

Protection

Protects internal organs [Functions of the Skeletal System]

Movement

Bones provide attachment points for muscles and act as levers [Functions of the Skeletal System]

Movement

Joints allow movement between bones [Functions of the Skeletal System]

Movement

Ligaments allow some movement between bones but prevent excessiveness [Functions of the Skeletal System]

Mineral Homeostasis

Bones store and release minerals, especially calcium and phosphorus [Functions of the Skeletal System]

Mineral Homeostasis

Calcium is important for muscle contraction and normal heart function [Functions of the Skeletal System]

Storage

Stores minerals such as calcium and phosphorus [Functions of the Skeletal System]

Storage

Yellow bone marrow stores fat [Functions of the Skeletal System]

Blood Cell Production

Red bone marrow contains hematopoietic tissue responsible for blood cell formation (RBCs, WBCs, platelets)[Functions of the Skeletal System]

Yellow Bone Marrow

mainly stores fat

Red Bone Marrow

Contains hematopoietic tissue responsible for blood cell formation (RBCs, WBCs, platelets)

Compact and spongy

types of bone tissue

Cortical Bone

other word for Compact Bone

Compact Bone

forms the solid outer casing of bone

Compact Bone

Dense and strong

Compact Bone

Contains a large amount of bone matrix

Compact Bone

Organized into structural units called osteons

Osteons

main functional and structural unit of compact bone

Volkmann’s Canals

allow blood vessels and nerves to communicate between different areas of bone

Interstitial Lamella

remnants of older osteons (located between osteons)

Cancellous Bone

other word for Spongy Bone

Spongy Bone

Contains numerous spaces

Spongy Bone

More porous than compact bone

Spongy Bone

Contains less bone matrix

Spongy Bone

consists of trabeculae

Trabeculae

Thin plates or fragments of bone

Trabeculae

Form the framework of spongy bone

Trabeculae

Spaces between _____ contain bone marrow

Long Bone

Longer than they are wide

Long Bone

Characterized by a shaft

Short Bone

have approximately equal length and width

Short Bone

No distinct shaft

Short Bone

May appear relatively square or cube-like

Flat Bone

relatively thin and flattened

Flat Bone

Often provide protection and broad surfaces for muscle attachment

Irregular Bone

Do not fit into bone shape categories

Irregular Bone

Have irregular and complex shapes

Sesamoid Bones

Bones develop inside tendons

Sesamoid Bones

Commonly found in the tendons of the lower extremities

Diaphysis

The shaft of the long bone, long and elongated

Epiphysis

The two ends of a long bone

Epiphysis

Includes proximal epiphysis and distal epiphysis

Epiphysis

Involved in joint formation

Metaphysis

Region between the diaphysis and epiphysis

Metaphysis

Contains the epiphyseal plate during bone growth

Epiphysis Plate

made of hyaline cartilage

Epiphysis Plate

Allows the bone to increase in length

Epiphysis Plate

It lasts until 18-20 years old

Epiphysis Plate

Once it closes, it become the epiphyseal line

Epiphysis Plate

After closure, the bone can no longer increase in length

Periosteum

External covering/lining of the bone, Contains dense irregular connective tissue

Medullary Cavity

Internal cavity of the bone

Medullary Cavity

Contains bone marrow

Medullary Cavity

Helps lighten the weight of the bone

Endosteum

Internal lining of the bone

Articular Cartilage

Made of hyaline cartilage

Articular Cartilage

Covers the surfaces of the bones involved in joints

Articular Cartilage

Helps reduce friction during movement

Extracellular Matrix

Bone is made of; 25% water, 25% collagen fibers, 50% crystallized mineral salts

Extracellular Matrix

consists of mineral salts and collagen fibers

Mineral Salts

provide rigidity/hardness

Collagen fibers

provide flexibility and help bones withstand stress

Collagen

A tough, rope-like protein

Collagen

Provides flexibility and tensile strength

Proteoglycans

Large molecules consisting of many polysaccharides attached to and surrounding core proteins

Proteoglycans

Important components of connective tissue, especially cartilage

Osteogenesis imperfecta

brittle bone disease, a rare condition caused by an abnormality in collagen fibers

Osteoprogenitor Cells

stem cells of bone

Osteoblasts

Responsible for bone formation

Osteocytes

Mature bone cells

Osteocytes

Surround by bone matrix

Osteocytes

Located in the lacunae

Osteoclasts

Responsible for bone breakdown/resorption

Osteoclasts

Digest and remove bone tissue

Osteoclasts

contain Howship’s lacunae

Osteogenesis

Process of bone formation

Osteogenesis

Initial bone formation begins around the 6th week of embryonic development

Intramembranous Ossification

Bone develops directly from mesenchymal connective tissue membranes

Intramembranous Ossification

Formation of flat bones and some irregular bones

Ossificiation Center Development, Calcification, Trabeculae Formation, Periosteum Development

Steps for Intramembranous Ossification

Ossificaiton Center Development

Mesenchymal cells differentiate into osteoproenitor cells

Ossification Center Development

Osteoprogenitor cells develop into osteoblasts

Calcification

Osteoblasts produce bone matrix

Calcification

Deposition of minerals

Calcification

Osteoblasts became osteocytes as they become surround by bone matrix