anatomy ch 6

Bone

Osseous tissue forming whole bone, vessels, and nerves.

Cartilage

Embryonic forerunner of most bones and covering of many joint surfaces.

Ligaments

Tissues that hold bone to bone at the joint.

Ligaments vs Tendons

Ligaments connect bone to bone at joints, whereas tendons attach muscle to bone.

Functions of the Skeleton

Support, movement, protection of delicate organs, blood formation in red bone marrow.

Hard Matrix

Bone is a connective tissue with a hard matrix.

Mineralization

Process of hardening of the bone; also known as calcification.

Types of Bone

Two types: Compact and Spongy.

Tissues Present in Bone

Bone, cartilage, ligaments, blood, bone marrow, adipose tissue, nervous tissue, fibrous connective tissue.

Compact Bone Features

Consists of osteons, perforating canals, circumferential lamellae, lacunae, and canaliculi.

Basic Unit of Compact Bone

Osteon.

Central Canal Contains

Vessels, nerves, and lymphatics for compact bone.

Circumferential Lamellae

Circles that fill in around the most superficial part of compact bone.

Lacunae

Small open spaces where osteocytes reside.

Canaliculi

Small canals for sharing nutrients among osteocytes in the lacunae.

Spongy Bone

Has trabeculae and spicules; has a porous appearance, lightweight but strong.

Trabeculae

Thin plates of bones.

Spicules

Rods and spines of bone.

Bone Marrow Location

Soft tissue located in medullary cavities of long bones and spaces within spongy bone.

Types of Bone Marrow

Red marrow (contains blood stem cells) and yellow marrow (mostly fat).

Red Marrow Location

Skull, vertebrae, sternum, ribs, pelvic girdle, proximal heads of humerus and femur.

Yellow Marrow Location

Shaft of long bones such as humerus, radius, ulna, femur, tibia, and fibula.

Bone Cells

Osteogenic, osteoblasts, osteocytes, osteoclasts.

Osteogenic Cells

Stem cells for osteoblasts and osteocytes.

Osteoblasts

Bone-forming cells that become osteocytes and are responsible for healing bones.

Osteocytes

Mature bone cells that reside in lacunae.

Osteoclasts

Bone-dissolving macrophages, derived from the fusion of multiple stem cells.

Ossification

Also called osteogenesis; the process of bone formation.

Mesenchyme

Embryonic connective tissue where ossification begins.

Methods of Ossification

Intramembranous and endochondral.

Intramembranous Ossification

Produces flat bones of the skull and clavicle; bone develops in a fibrous sheet.

Endochondral Ossification

Most bones develop from the hyaline cartilage model.

Bone Elongation

Bones grow longer at epiphysial plates.

Epiphysial Plates

Plates made of hyaline cartilage; remnants of the growth plate.

Appositional Growth

Growth in diameter and thickness of bones.

Intramembranous Ossification Process

• Osteoblasts in periosteum deposit matrix. - Cells become osteocytes once the matrix hardens.

Osteoclasts Function

Widen the medullary cavity.

Flat Bones

Thin, often curved bones (e.g., ribs).

Irregular Bones

Bones with complex shapes (e.g., vertebrae).

Long Bones

Rigid levers for movement (e.g., femur).

Short Bones

Bones that glide within joints (e.g., wrist carpals).

Features of Long Bones

• Compact and spongy bone tissues - Two epiphyses - Marrow cavity - Epiphysial line - Periosteum covering - Nutrient foramina - Endosteum lining - Articular cartilage.

Osteopenia

Loss of bone density leading to increased fracture risk.

Osteoporosis

Severe bone loss leading to increased risk of pathological fractures.

Skeletal System After Age 35

Osteoblast activity decreases compared to osteoclast activity.

Bone Mass Loss After Age 40

Females lose 8% and males lose 3% of bone mass per decade.

Who Loses More Bone Mass After Age 40?

Women.

Pathological Fracture

Occurs in bone weakened by disease such as osteoporosis.

Closed vs Open Reduction

Open reduction uses surgical methods; closed reduction is nonsurgical manipulation.

Fracture Healing Time

8-12 weeks including rehabilitation.