Bone Histology & Skeletal System – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering bone ECM, bone development and growth, remodeling, fracture repair, skull and vertebral anatomy, and the axial and appendicular skeleton.

Extracellular Matrix (ECM)

Noncellular bone component comprising collagen fibers for tensile strength, mineral salts (calcium phosphate/hydroxyapatite) for hardness, and proteoglycans to trap water for resilience.

Collagen fibers

Protein fibers in bone ECM that provide tensile strength and resistance to pulling/twisting.

Hydroxyapatite

Mineral form of calcium phosphate in bone; contributes to hardness and compressive strength.

Calcium phosphate

Mineral component in bone that forms hydroxyapatite, aiding hardness.

Proteoglycans

Glycosaminoglycans in ECM that trap water to increase bone resilience and elasticity.

Long bones

Bones longer than wide with a diaphysis (shaft) and epiphyses (ends); e.g., femur, humerus.

Diaphysis

Shaft of a long bone containing the medullary cavity.

Medullary cavity

Cavity inside the diaphysis that contains yellow marrow in adults.

Epiphysis

Ends of a long bone containing spongy bone and red marrow.

Epiphyseal plate

Growth region (cartilage) at the end of long bones that ossifies to form the epiphyseal line.

Periosteum

Dense outer covering of bone providing nutrition and a surface for tendon/ligament attachment.

Endosteum

Thin lining inside bone, lining the medullary cavity and spaces of spongy bone.

Articular cartilage

Hyaline cartilage covering joint surfaces to reduce friction and absorb shock.

Short bones

Cube-like bones (e.g., carpals, tarsals) with similar length and width.

Flat bones

Thin, flattened bones that protect organs and provide surfaces for muscle attachment (e.g., skull, sternum, ribs).

Irregular bones

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

Hemopoiesis (hematopoiesis)

Blood cell production, primarily in red marrow.

Red marrow

Marrow in which hematopoiesis occurs; abundant in children and in certain bones of adults.

Yellow marrow

Marrow that stores fats; increases with age as red marrow decreases.

Osteoblasts

Bone-building cells that synthesize and secrete bone matrix.

Osteocytes

Mature bone cells embedded in lacunae that maintain the bone matrix.

Osteoclasts

Bone-resorbing cells that break down bone tissue during remodeling.

Lamellae

Concentric lamellar rings of bone matrix forming osteons in compact bone.

Canaliculi

Tiny channels connecting osteocytes, allowing nutrient and waste exchange.

Compact bone (cortical bone)

Dense bone tissue composed of osteons with a central Haversian canal; strong and load-bearing.

Spongy bone (cancellous)

Lattice-like bone with trabeculae, contains red marrow, lighter but weaker than compact bone.

Ossification

Bone formation process.

Intramembranous ossification

Direct bone formation from mesenchyme; forms flat bones like skull, mandible, clavicle.

Endochondral ossification

Bone formation by replacing cartilage; most bones develop this way.

Epiphyseal line

Remnant of the epiphyseal plate after growth ends; marks where growth occurred.

Appositional growth

Growth in bone thickness due to periosteal osteoblast activity and inner surface osteoclast activity.

Longitudinal growth

Growth in bone length at the epiphyseal plate; cartilage on the epiphyseal side is replaced by bone on the diaphyseal side.

Parathyroid Hormone (PTH)

Hormone that stimulates osteoclast activity to raise blood calcium levels.

Calcitonin

Hormone that stimulates osteoblast activity to lower blood calcium levels.

HGH (Human Growth Hormone)

Hormone that stimulates cartilage and bone growth during development.

IGF (Insulin-like Growth Factor)

Growth-promoting factors that mediate HGH effects on cartilage and bone growth.

Scoliosis

Lateral curvature of the spine (often affecting the thoracic cage).

Estrogen

Sex hormone that contributes to growth spurts and closes epiphyseal plates at puberty.

Testosterone

Sex hormone that contributes to growth spurts and closes epiphyseal plates at puberty.

Calcium

Mineral essential for bone hardness and metabolic processes.

Phosphorus

Mineral component of bone matrix alongside calcium.

Magnesium

Mineral that strengthens bone and contributes to bone metabolism.

Vitamin A

Vitamin that regulates bone cell activity.

Vitamin C

Vitamin necessary for collagen synthesis in bone.

Vitamin D

Vitamin that enhances calcium absorption in the gut.

Exercise

Physical activity that strengthens bones and improves density.

Balanced diet

Diet providing adequate minerals and vitamins for bone health.

Hematoma

Localized swelling of clotted blood at a fracture site during repair.

Fibrocartilage callus

Initial soft tissue bridge that forms between fracture ends during repair.

Bony callus

New bone tissue that replaces fibrocartilage during fracture healing.

Remodeling

Bone reshaping process after fracture, restoring original structure and strength.

Closed fracture

Fracture where the bone does not break the skin.

Open fracture

Fracture where the bone breaks the skin.

Partial fracture

Incomplete fracture where the bone is not completely broken.

Complete fracture

Fracture where the bone is completely broken apart.

Comminuted fracture

Fracture with multiple bone fragments.

Axial skeleton

Skull, vertebral column, and thoracic cage; 80 bones total.

Skull bones

Total 22 bones forming the skull: 8 cranial and 14 facial bones.

Cranial bones

Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.

Facial bones

Nasal (2), maxilla (2), palatine (2), mandible, zygomatic (2), lacrimal (2), inferior nasal conchae (2), vomer.

Sutures

Rigid joints between skull bones: coronal, sagittal, lambdoid, squamous.

Sinuses

Air-filled cavities: sphenoid, frontal, ethmoid, maxillary.

Fontanels

Soft spots in infant skulls that allow brain growth; typically close by ~2 years.

Hyoid bone

Bone that supports the tongue and does not articulate with other bones.

Vertebral column

26 vertebrae: 7 cervical (C1 Atlas, C2 Axis), 12 thoracic, 5 lumbar, plus sacrum and coccyx.

Atlas (C1)

First cervical vertebra; supports the skull.

Axis (C2)

Second cervical vertebra; contains the odontoid process for rotation.

Cervical vertebrae

Vertebrae of the neck (C1–C7).

Thoracic vertebrae

Vertebrae of the chest (T1–T12) with rib attachments.

Lumbar vertebrae

Lower back vertebrae (L1–L5); largest and weight-bearing.

Sacrum

Five fused vertebrae forming the posterior wall of the pelvis.

Coccyx

Tailbone; four fused vertebrae.

Kyphosis

A thoracic curvature; a humped appearance.

Lordosis

A lumbar curvature; swayback.

Sternum

Breastbone with three parts: manubrium, body, xiphoid process.

Ribs

12 pairs of bones forming the thoracic cage; protect organs and aid breathing.

True ribs

Ribs 1–7 attached directly to the sternum via costal cartilage.

False ribs

Ribs 8–12 attached indirectly to the sternum (or not at all for 11–12).

Floating ribs

Ribs 11–12 that do not attach to the sternum.

Appendicular skeleton

Pectoral girdle, upper limbs, pelvic girdle, lower limbs; 126 bones.

Pectoral girdle

Shoulder bones: clavicle and scapula.

Glenoid cavity

Socket that articulates with the humerus to form the shoulder joint.

Humerus

Upper arm bone.

Ulna

Medial forearm bone.

Radius

Lateral forearm bone.

Carpals

Eight wrist bones.

Metacarpals

Five hand bones.

Phalanges (hand)

Fingers; fourteen bones in each hand (proximal, middle, distal).

Pelvic girdle

Hip bones (ilium, ischium, pubis) fused; plus sacrum and coccyx.

Acetabulum

Hip socket where the femur head fits.

Female pelvis features

Wider pubic arch (>90°), oval pelvic inlet, broader sacrum.

Male pelvis features

Narrower pubic arch (<90°), heart-shaped pelvic inlet.

Femur

Longest bone in the body.

Patella

Kneecap; protects the knee joint.

Tibia

Medial, weight-bearing bone of the lower leg.

Fibula

Lateral, slender bone of the lower leg.

Tarsals

Seven ankle bones, including the talus and calcaneus.

Talus

Ankle bone that forms the ankle joint with tibia and fibula.

Calcaneus

Heel bone.

Metatarsals

Five foot bones.