Marieb Human Anatomy & Physiology - Chapter 06: Bones and Skeletal Tissues

Comprehensive vocabulary flashcards covering the structure, cellular biology, growth, remodeling, fracture repair, and clinical pathologies of bone tissue.

Ligaments

Bands of dense regular connective tissue that stabilize and connect bone to other bone.

Skeletal Cartilage

Highly resilient, molded cartilage tissue consisting primarily of water, which contains no blood vessels or nerves.

Perichondrium

A layer of dense connective tissue surrounding cartilage like a girdle; it helps resist outward expansion and contains blood vessels for nutrient delivery.

Chondrocytes

Cartilage cells that are encased in small cavities called lacunae within a jelly-like extracellular matrix.

Hyaline Cartilage

The most abundant cartilage type containing only collagen fibers; provides support, flexibility, and resilience in articular, costal, respiratory, and nasal cartilages.

Elastic Cartilage

A type of cartilage similar to hyaline cartilage but containing both collagen and elastic fibers; located in the external ear and epiglottis.

Fibrocartilage

Cartilage with thick collagen fibers providing great tensile strength, found in the menisci of the knee, pubic symphysis, and intervertebral discs.

Appositional Growth (Cartilage)

Cartilage growth that occurs when cartilage-forming cells in the perichondrium secrete new matrix against the external face of existing cartilage.

Interstitial Growth (Cartilage)

Cartilage growth from within that occurs when chondrocytes within lacunae divide and secrete new matrix, expanding cartilage tissue internally.

Hematopoiesis

Blood cell formation that occurs within the red bone marrow of certain bones.

Osteocalcin

A hormone produced by bones that helps regulate insulin secretion, glucose homeostasis, and energy expenditure.

Axial Skeleton

The skeletal division forming the long axis of the body, consisting of the skull, vertebral column, and rib cage.

Appendicular Skeleton

The skeletal division comprising the bones of the upper and lower limbs and the girdles that attach limbs to the axial skeleton.

Long Bones

Bones that are longer than they are wide, with a medullary cavity extending the length of the shaft (e.g., most limb bones).

Short Bones

Cube-shaped bones such as those in the wrist and ankle.

Sesamoid Bones

Special short bones that form within tendons, such as the patella, which vary in size and number among individuals.

Flat Bones

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

Irregular Bones

Bones with complicated shapes that do not fit into other shape categories, such as vertebrae and hip bones.

Compact Bone

Dense outer layer found on every bone that appears smooth and solid to the naked eye.

Spongy Bone

Internal bone tissue made up of a honeycomb of small, needle-like or flat pieces called trabeculae.

Diploë

The internal thin layer of spongy bone sandwiched between plates of compact bone within short, irregular, and flat bones.

Diaphysis

The tubular shaft that forms the long axis of a long bone, composed of compact bone surrounding a medullary cavity filled with yellow bone marrow in adults.

Epiphyses

The ends of long bones that consist of compact bone externally and spongy bone internally, covered on joint surfaces by articular cartilage.

Epiphyseal Line

The remnant of the childhood epiphyseal plate located between the diaphysis and epiphysis where longitudinal bone growth occurred.

Periosteum

A white, double-layered membrane covering external bone surfaces (except joints), consisting of an outer fibrous layer and an inner osteogenic layer.

Sharpey’s Fibers

Dense irregular connective tissue fibers in the fibrous layer of the periosteum that secure the membrane to the bone matrix.

Endosteum

A delicate connective tissue membrane covering internal bone surfaces, lining canals of compact bone and trabeculae of spongy bone.

Red Bone Marrow

Hematopoietic tissue found within trabecular cavities of spongy bone and diploë of flat bones (such as the sternum), and in adult heads of the femur and humerus.

Osteoprogenitor Cells

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

Osteoblasts

Actively mitotic bone-forming cells that secrete unmineralized bone matrix called osteoid.

Osteoid

The unmineralized organic bone matrix secreted by osteoblasts, composed of ground substance and collagen fibers (which constitute $90\%$ of bone protein).

Osteocytes

Mature, non-dividing bone cells located in lacunae that monitor and maintain the bone matrix and act as mechanical stress or strain sensors.

Bone-Lining Cells

Flat cells on bone surfaces that help maintain matrix; called periosteal cells on the external bone surface and endosteal cells on internal surfaces.

Osteoclasts

Giant, multinucleate cells derived from hematopoietic stem cells that perform bone resorption (matrix breakdown) via lysosomal enzymes and protons.

Resorption Bays

Depressions or grooves on bone surfaces occupied by active osteoclasts as they break down bone matrix.

Osteon (Haversian System)

The structural unit of compact bone; an elongated cylinder parallel to the long axis of the bone that acts as a tiny weight-bearing pillar.

Lamellae

Concentric rings of bone matrix within an osteon in which collagen fibers run in alternating directions in adjacent rings to resist twisting stress.

Central (Haversian) Canal

A canal running through the core of an osteon containing blood vessels and nerve fibers.

Perforating (Volkmann’s) Canals

Canals lined with endosteum that run at right angles to central canals, connecting vessels and nerves of the periosteum, medullary cavity, and central canal.

Canaliculi

Hairlike canals that connect lacunae to each other and to the central canal, allowing communication and relay of nutrients and wastes between osteocytes.

Interstitial Lamellae

Incomplete lamellae that fill gaps between forming osteons or represent remnants of osteons partially destroyed by bone remodeling.

Circumferential Lamellae

Layers of lamellae extending around the entire surface of the diaphysis, just deep to the periosteum and superficial to the endosteum, that resist twisting.

Sacrificial Bonds

Bonds in or between collagen molecules that stretch and break to dissipate energy and prevent bone fractures during trauma, and re-form if no additional trauma occurs.

Hydroxyapatites

Inorganic mineral salts, primarily tiny calcium phosphate crystals in and around collagen fibers, which make up $65\%$ of bone mass and provide hardness and compression resistance.

Endochondral Ossification

Bone formation process where hyaline cartilage is broken down and replaced by bone tissue, forming essentially all bones inferior to the base of the skull except the clavicles.

Intramembranous Ossification

The process of bone formation directly within fibrous connective tissue membranes formed by mesenchymal cells, producing cranial bones and clavicles.

Primary Ossification Center

The region in the center of the hyaline cartilage shaft where endochondral ossification initiates as blood vessels infiltrate the perichondrium.

Periosteal Bud

A collection of blood vessels, nerves, red bone marrow, osteogenic cells, and osteoclasts that invades internal cavities of the calcified cartilage model during endochondral ossification.

Proliferation Zone

Area of cartilage on the diaphysis side of the epiphyseal plate where cells rapidly divide, pushing the epiphysis away from the diaphysis to lengthen the bone.

Hypertrophic Zone

Zone of the epiphyseal plate containing older chondrocytes whose lacunae enlarge and erode, creating interconnecting spaces.

Calcification Zone

Zone of the epiphyseal plate where surrounding cartilage matrix calcifies and chondrocytes die and deteriorate.

Ossification Zone

Zone where calcified cartilage spicules are eroded by osteoclasts and covered with new bone matrix by osteoblasts to form spongy bone.

Epiphyseal Plate Closure

The fusion of the epiphysis and diaphysis occurring around age $18$ in females and age $21$ in males, terminating longitudinal bone growth.

Bone Remodeling

A continuous lifelong cycle of bone deposition and bone resorption orchestrated by remodeling units of adjacent osteoblasts and osteoclasts, replacing $5\text{--}10\%$ of bone each year.

Osteoid Seam

An unmineralized band of newly deposited bone matrix marking the active site of bone deposit by osteoblasts.

Calcification Front

The abrupt transition zone between the newly deposited unmineralized osteoid seam and older, fully mineralized bone.

Parathyroid Hormone (PTH)

Hormone released by the parathyroid glands in response to falling blood calcium levels that stimulates osteoclasts to resorb bone and release calcium into the bloodstream.

Wolff’s Law

The physiological law stating that bones grow or remodel in direct response to the mechanical demands and stresses placed upon them.

Comminuted Fracture

A fracture where the bone fragments into three or more pieces; particularly common in older adults whose bones are more brittle.

Compression Fracture

A fracture in which the bone is crushed, common in porous (osteoporotic) bones subjected to extreme trauma such as a fall.

Spiral Fracture

A ragged break occurring when excessive twisting forces are applied to a bone; common in sports injuries.

Epiphyseal Fracture

A break where the epiphysis separates from the diaphysis along the epiphyseal plate, occurring where cartilage cells are dying and matrix is calcifying.

Depressed Fracture

A fracture in which the broken bone portion is pressed inward, typical of skull fractures.

Greenstick Fracture

An incomplete break where one side of the shaft breaks and the other side bends, common in children whose bones have relatively more organic matrix.

Reduction (Bone)

The realignment of broken bone ends, categorized as closed (manual manipulation) or open (surgical pins or wires).

Hematoma (Fracture Repair)

A localized mass of clotted blood formed by torn hemorrhaging blood vessels at the site of a bone break during the first stage of fracture repair.

Fibrocartilaginous Callus

A mass of repair tissue composed of collagen fibers, cartilage matrix, and spongy bone that bridges broken bone ends in the second stage of fracture healing.

Stages of Bone Fracture Repair

The four sequential stages of healing: (1) hematoma forms, (2) fibrocartilaginous callus forms, (3) bony callus forms, and (4) bone remodeling occurs.

Osteomalacia

A disorder in adults in which bones are poorly mineralized because calcium salts are not adequately deposited into osteoid, leading to soft, weak, painful bones.

Rickets

The childhood form of osteomalacia caused by vitamin D deficiency or insufficient calcium, resulting in bowed legs and abnormally long, enlarged bone ends.

Osteoporosis

A group of diseases in which bone resorption outpaces bone deposition, leading to declined bone mass while matrix composition remains normal, frequently affecting postmenopausal women.

Paget’s Disease

A bone disorder characterized by excessive and haphazard bone deposit and resorption, resulting in poorly mineralized Pagetic bone with an abnormally high ratio of spongy to compact bone.