Bones and Bone Structure

Vocabulary flashcards based on Chapter 6 lecture covering bone shapes, markings, microscopic structures, cells, ossification processes, calcium regulation, and fracture repair.

Sutural Bones

Also called Wormian bones, these are small, flat, oddly shaped bones found between the flat bones of the skull, ranging in size from a grain of sand to a quarter.

Irregular Bones

Bones with complex shapes containing short, flat, notched, or ridged surfaces, such as the vertebrae, pelvic bones, and several skull bones.

Short Bones

Bones that are boxlike in appearance, such as the carpal bones (wrists) and tarsal bones (ankles).

Flat Bones

Bones with thin, parallel surfaces that form the roof of the skull, sternum, ribs, and scapulae, providing protection and muscle attachment areas.

Long Bones

Relatively long and slender bones found in the arm, forearm, thigh, leg, palms, soles, fingers, and toes.

Femur

The long bone of the thigh, which is the largest and heaviest bone in the body.

Sesamoid Bones

Usually small, round, and flat bones that form within tendons near joints of the knees, hands, and feet.

Patella

A small, shallow dish-shaped sesamoid bone commonly known as the kneecap.

Process

A bone marking characterized as any projection or bump.

Ramus

Part of a bone that forms an angle with the rest of the structure.

Sinus

A chamber within a bone that is normally filled with air.

Foramen

A rounded passageway through a bone for blood vessels and/or nerves.

Fissure

A deep furrow, cleft, or slit in a bone.

Meatus

A passage or channel in a bone, especially the opening of a canal.

Canal

A duct or channel passing through a bone.

Sulcus

A narrow groove on a bone surface.

Fossa

A shallow depression in a bone.

Trochanter

A large, rough projection on a bone where muscles, tendons, or ligaments attach.

Crest

A prominent ridge on a bone where connective tissues attach.

Spine

A pointed process on a bone.

Line

A low ridge on a bone surface.

Tubercle

A small, rounded projection on a bone.

Tuberosity

A rough projection on a bone.

Head

An expanded articular end of an epiphysis, often separated from the shaft by a narrower neck.

Neck

A narrow connection between the epiphysis and diaphysis of a bone.

Facet

A small, flat articular surface on a bone.

Condyle

A smooth, rounded articular process on a bone.

Trochlea

A smooth, grooved articular process shaped like a pulley.

Diaphysis

The extended tubular shaft of a long bone, featuring a wall of compact bone surrounding a medullary cavity.

Medullary Cavity

The central space within the diaphysis of a long bone, also called the marrow cavity.

Epiphysis

The expanded wide part at each end of a long bone, consisting mostly of spongy (trabecular) bone.

Metaphysis

The narrow region of a long bone where the diaphysis and epiphysis meet.

Diploë

The layer of spongy bone situated between the inner and outer layers of compact bone (cortex) within the cranium.

Canaliculi

Narrow passageways in the bone matrix that allow exchange of nutrients, wastes, and gases between osteocytes and blood vessels.

Hydroxyapatite

Mineral crystals with the formula $\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2$, formed by the interaction of calcium phosphate and calcium hydroxide to give bone rigidity.

Osteogenic Cells

Stem cells located in bone whose divisions produce osteoblasts.

Osteoblasts

Immature bone cells that secrete organic components of the bone matrix (osteoid).

Osteocytes

Mature bone cells located within lacunae that maintain the bone matrix.

Osteoclasts

Large multinucleate cells that secrete acids and enzymes to dissolve bone matrix.

Osteon

The basic functional unit of compact bone, containing concentric lamellae surrounding a central canal.

Perforating Canals

Passageways running perpendicular to the bone surface that carry blood vessels into deep bone tissue and the medullary cavity.

Trabeculae

The open meshwork matrix struts characteristic of spongy bone structure.

Red Bone Marrow

Tissue located between trabeculae of spongy bone that forms blood cells and supplies nutrients to osteocytes.

Yellow Bone Marrow

Adipose tissue found in certain spongy bone regions that serves as an energy reserve by storing fat.

Periosteum

A two-layer membrane covering the outer surface of bones (except inside joint cavities) that isolates bone, provides vessel routes, and aids growth and repair.

Perforating Fibers

Collagen fibers from the periosteum that become embedded into bone tissue, anchoring tendons and joint capsules securely.

Endosteum

An incomplete cellular layer containing osteogenic cells, osteoblasts, and osteoclasts that lines the medullary cavity, covers trabeculae, and lines central canals.

Ossification

The formal process of bone tissue formation, also known as osteogenesis.

Calcification

The deposition of calcium salts within tissue during the ossification process.

Endochondral Ossification

The form of bone development in which an initial hyaline cartilage model is progressively replaced by bone.

Primary Ossification Center

The initial region inside the diaphysis where blood vessels enter and spongy bone formation begins during endochondral ossification.

Secondary Ossification Center

Site formed in the epiphysis when capillaries and osteoblasts migrate there during endochondral ossification.

Epiphyseal Cartilage

A narrow cartilaginous zone in the metaphysis (epiphyseal plate) separating the epiphysis from the diaphysis during lengthening of growing bones.

Epiphyseal Closure

The completion of epiphyseal growth at puberty when epiphyseal cartilage production stops and the plate disappears.

Epiphyseal Line

The distinct line visible on x-rays at the former site of the epiphyseal cartilage after bone growth has ended.

Appositional Growth

The process where a bone increases in diameter and width by depositing new matrix layers at the outer surface while removing matrix at the inner medullary surface.

Intramembranous Ossification

Also called dermal ossification, this process forms dermal bones directly within fibrous connective tissues of the deep dermis without a cartilage model.

Spicules

Small struts of developing bone that radiate outward from the ossification center during intramembranous ossification.

Parathyroid Hormone (PTH)

Hormone released by the parathyroid glands when blood calcium falls below $8.5\,\text{mg/dL}$ to stimulate osteoclasts, increase intestinal absorption, and decrease urinary calcium loss.

Calcitonin

Hormone secreted by thyroid gland C cells when blood calcium rises above $11\,\text{mg/dL}$ to inhibit osteoclasts, decrease absorption, and promote urinary calcium excretion.

Fracture Hematoma

A large blood clot formed immediately following a bone fracture that isolates the damaged area and establishes a fibrous repair network.

Callus

A collar of cartilage and bone (external callus) and internal spongy bone mass formed during fracture repair to stabilize the broken bone ends.