Bones and Skeletal Tissue in Human Anatomy

Hyaline cartilage

Provides support, flexibility, and resilience; most abundant type; contains collagen fibers only.

Elastic cartilage

Similar to hyaline cartilage, but contains elastic fibers; found in external ear and epiglottis.

Fibrocartilage

Contains thick collagen fibers with great tensile strength; found in menisci of knee and vertebral discs.

Perichondrium

Layer of dense connective tissue surrounding cartilage that helps resist outward expansion and contains blood vessels for nutrient delivery.

Hematopoiesis

Blood cell formation that occurs in red marrow cavities of certain bones.

Osteocalcin

Hormone secreted by bones that helps to regulate insulin secretion, glucose levels, and metabolism.

Axial skeleton

Consists of the long axis of the body, including the skull, vertebral column, and rib cage.

Appendicular skeleton

Includes bones of the upper and lower limbs and girdles attaching limbs to the axial skeleton.

Long bones

Bones that are longer than they are wide, such as limb bones.

Short bones

Cube-shaped bones found in the wrist and ankle; sesamoid bones form within tendons (e.g., patella).

Flat bones

Thin, flat, slightly curved bones such as the sternum, scapulae, ribs, and most skull bones.

Irregular bones

Bones with complicated shapes, such as vertebrae and hip bones.

Spongy bone

Bone that has a mesh of bony spines called trabeculae.

Compact bone

Bone that looks smooth and solid.

Articular cartilage

Cartilage found at joints.

Costal cartilage

Cartilage that connects ribs to the sternum.

Intervertebral disc

Cartilage found between vertebrae.

Meniscus

Padlike cartilage in the knee joint.

Trabeculae

Bony spines that form the mesh structure of spongy bone.

Red marrow

Bone marrow responsible for blood cell production.

Yellow marrow

Bone marrow primarily involved in fat storage.

Calcium and phosphorus

Minerals stored in bones, serving as a reservoir for the body.

Flat Bones

Consist of a layer of spongy bone sandwiched between two thin layers of compact bone.

Diaphysis

Tubular shaft that forms long axis of bone.

Epiphyses

Ends of long bones that consist of compact bone externally and spongy bone internally.

Articular cartilage

Covers articular (joint) surfaces.

Epiphyseal line

Remnant of childhood epiphyseal plate where bone growth occurs.

Periosteum

White, double-layered membrane that covers external surfaces except joints.

Fibrous layer

Outer layer of periosteum consisting of dense irregular connective tissue with Sharpey's fibers that secure to bone matrix.

Osteogenic layer

Inner layer of periosteum abutting bone that contains primitive osteogenic stem cells that give rise to most all bone cells.

Endosteum

Delicate connective tissue membrane covering internal bone surface.

Hematopoietic tissue

Red marrow found within trabecular cavities of spongy bone and diploë of flat bones.

Red marrow

Found in newborns' medullary cavities and all spongy bone, and in adults located in heads of femur and humerus.

Yellow marrow

Can convert to red if a person becomes anemic.

Bone markings

Sites of muscle, ligament, and tendon attachment on external surfaces.

Projection

Outward bulge of bone, may be due to increased stress from muscle pull or is a modification for joints.

Depression

Bowl- or groove-like cut-out that can serve as passageways for vessels and nerves, or plays a role in joints.

Opening

Hole or canal in bone that serves as passageways for blood vessels and nerves.

Osteoprogenitor cell

Mitotically active stem cells in periosteum and endosteum that can differentiate into osteoblasts or bone-lining cells.

Osteoblast

Matrix-synthesizing cell responsible for bone growth.

Osteocyte

Mature bone cell that monitors and maintains the mineralized bone matrix.

Osteoclast

Bone-resorbing cell derived from the same hematopoietic cells that become macrophages.

Ossification (osteogenesis)

The process of bone tissue formation.

Bone remodeling

Occurs throughout life as part of bone development and repair.

Endochondral ossification

Process where bone collar forms around the diaphysis of the hyaline cartilage model.

Endochondral Ossification

The process where cartilage is replaced by bone in the development of long bones.

Primary ossification center

The region in the center of the diaphysis where cartilage calcifies and cavities develop.

Bone collar

A layer of bone that forms around the diaphysis of the hyaline cartilage model.

Secondary ossification center

The area where ossification occurs in the epiphyses after birth.

Medullary cavity

The central cavity of bone shafts where red marrow is stored.

Epiphyseal plate

The area of hyaline cartilage that remains between the epiphysis and diaphysis during growth.

Articular cartilage

Hyaline cartilage that covers the ends of bones in joints.

Intramembranous ossification

The process of bone development from fibrous connective tissue membranes.

Osteoblast

A cell that secretes the matrix for bone formation.

Osteoid

The unmineralized organic component of bone matrix secreted by osteoblasts.

Osteocyte

A mature bone cell that maintains the bone matrix.

Collagen fiber

A protein that provides strength and structure to bones.

Ossification center

The site in the bone where ossification begins.

Fibrous periosteum

The outer layer of connective tissue surrounding the bone.

Compact bone

The dense outer layer of bone that provides strength.

Immature spongy bone

The initial form of spongy bone that is later remodeled into mature spongy bone.

Diploë

The spongy bone found between the inner and outer layers of compact bone in flat bones.

Red marrow

The tissue found in the medullary cavity that produces blood cells.

Vascularized mesenchyme

Mesenchymal tissue that contains blood vessels and contributes to bone formation.

Trabeculae

The small rod-like structures in spongy bone that provide support.

Hyaline cartilage

A type of cartilage that is glossy and provides support and flexibility.

Spongy bone formation

The process of creating spongy bone from cartilage or other tissues.

Interstitial growth

Requires presence of epiphyseal cartilage in the epiphyseal plate.

Epiphyseal plate

Maintains constant thickness.

Rate of cartilage growth

On one side balanced by bone replacement on the other.

Zones of the epiphyseal plate

Consists of five zones: Resting (quiescent) zone, Proliferation (growth) zone, Hypertrophic zone, Calcification zone, Ossification (osteogenic) zone.

Resting zone

Zone in the epiphyseal plate where cartilage cells are quiescent.

Proliferation zone

Zone where cartilage cells undergo mitosis.

Hypertrophic zone

Zone where older cartilage cells enlarge.

Calcification zone

Zone where matrix becomes calcified; cartilage cells die; matrix begins deteriorating.

Ossification zone

Zone where new bone is forming.

Bone remodeling

About 5-7% of bone mass is recycled each week.

Spongy bone replacement

Replaced approximately every 3-4 years.

Compact bone replacement

Replaced approximately every 10 years.

Bone remodeling process

Consists of both bone deposit and bone resorption.

Remodeling units

Packets of adjacent osteoblasts and osteoclasts coordinate the remodeling process.

Parathyroid hormone (PTH)

Produced by parathyroid glands in response to low blood calcium levels.

Calcitonin

Produced by parafollicular cells of thyroid gland in response to high levels of blood calcium levels.

Calcium homeostasis of blood

Normal range is 9-11 mg/100 ml.

Fractures

Breaks in bones.

Nondisplaced fracture

Ends retain normal position.

Displaced fracture

Ends are out of normal alignment.

Complete fracture

Broken all the way through.

Incomplete fracture

Not broken all the way through.

Open (compound) fracture

Skin is penetrated.

Closed (simple) fracture

Skin is not penetrated.

Fracture treatment

Involves reduction, the realignment of broken bone ends.

Closed reduction

Physician manipulates to correct position.

Open reduction

Surgical pins or wires secure ends.

Stages of bone fracture repair

Includes hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling.

Classification of bones

Based on their shape, including long, short, flat, and irregular.