Histology and Physiology of Bones and Articulations

Vocabulary flashcards covering bone histology, development, growth, homeostasis, axial/appendicular anatomical structures, and joint classifications based on Seeley's Principles of Anatomy & Physiology.

Chondroblasts

Cells that produce cartilage matrix and eventually become chondrocytes.

Chondrocytes

Mature cartilage cells located within lacunae and surrounded by extracellular matrix.

Perichondrium

A double-layered connective tissue sheath surrounding cartilage, consisting of an outer fibrous layer with fibroblasts and an inner layer containing chondroblasts.

Appositional growth

The process of adding new cartilage or bone matrix onto the surface of existing older tissue.

Interstitial growth

The process where cartilage grows from within through the division of chondrocytes and production of additional matrix.

Hydroxyapatite

Calcium phosphate crystals that constitute approximately $65\%$ of bone matrix and provide weight-bearing strength.

Osteoblasts

Bone-forming cells derived from osteochondral progenitor cells that produce bone matrix and surround themselves with matrix to become osteocytes.

Osteocytes

Mature bone cells residing within lacunae that connect to one another through cell processes housed in canaliculi.

Osteoclasts

Large bone-resorbing cells originating from stem cells in red bone marrow that break down bone matrix.

Woven bone

Immature bone tissue characterized by randomly oriented collagen fibers, which is subsequently remodeled into lamellar bone.

Lamellar bone

Mature bone tissue organized into thin layers called lamellae, containing parallel-oriented collagen fibers.

Cancellous bone

Spongy bone tissue consisting of an interconnecting lattice of trabeculae with spaces filled with bone marrow and blood vessels.

Trabeculae

Interconnecting beams of bone that form the structural lattice of cancellous bone, oriented along lines of stress.

Compact bone

Dense external layer of bone tissue consisting of highly organized lamellae with few spaces.

Osteon

The structural unit of compact bone, composed of concentric lamellae surrounding a central canal; also known as a Haversian system.

Diaphysis

The main tubular shaft forming the axis of a long bone, composed of compact bone surrounding a medullary cavity.

Epiphysis

The expanded terminal end of a long bone, featuring an outer layer of compact bone and an inner core of spongy bone.

Epiphyseal plate

A layer of hyaline cartilage separating the diaphysis from the epiphysis in growing bones, serving as the site of growth in bone length.

Periosteum

A double-layered membrane covering the outer surface of bone, consisting of an outer dense regular connective tissue layer and an inner osteogenic layer.

Endosteum

A delicate membrane lining internal surfaces of bone, containing osteoblasts, osteoclasts, and osteochondral progenitor cells.

Intramembranous ossification

The formation of bone directly within a fibrous connective tissue membrane, producing skull bones, parts of the mandible, and clavicle diaphyses.

Endochondral ossification

The formation of bone tissue by replacing a pre-existing hyaline cartilage model.

Fontanels

Unossified membrane-covered regions between skull bones present at birth in infants.

Basic multicellular unit (BMU)

A temporary assembly of osteoclasts and osteoblasts that tunnels through bone to carry out remodeling.

Parathyroid hormone (PTH)

The major regulator of blood $Ca^{2+}$ levels, secreted when blood $Ca^{2+}$ drops to indirectly stimulate osteoclast activity, renal calcium reabsorption, and active vitamin D synthesis.

Calcitonin

A hormone released by the thyroid gland in response to elevated blood $Ca^{2+}$ levels that inhibits osteoclast activity and decreases blood calcium.

Sella turcica

A saddle-shaped bony structure on the sphenoid bone within the cranial cavity that houses the pituitary gland.

Crista galli

A process in the anterior cranial fossa on the ethmoid bone to which the dura mater attaches.

Sutures

Fibrous joints between skull bones featuring interdigitating bone margins joined by dense fibrous connective tissue.

Syndesmoses

Fibrous joints in which bones are held together by fibrous ligaments, permitting slight movement.

Gomphoses

Fibrous joints in which peg-like structures fit into sockets and are anchored by periodontal ligaments, such as teeth in alveolar processes.

Synchondroses

Cartilaginous joints where bones are united by hyaline cartilage, such as epiphyseal plates.

Symphyses

Cartilaginous joints united by fibrocartilage that permit slight movement, such as intervertebral disks and the symphysis pubis.

Bursae

Fluid-filled sac extensions of synovial joints that reduce friction between skin, tendons, or bones.

Chondroblasts

Cells that produce cartilage matrix and eventually become chondrocytes.

Chondrocytes

Mature cartilage cells located within lacunae and surrounded by extracellular matrix.

Perichondrium

A double-layered connective tissue sheath surrounding cartilage, consisting of an outer fibrous layer with fibroblasts and an inner layer containing chondroblasts.

Appositional growth

The process of adding new cartilage or bone matrix onto the surface of existing older tissue.

Interstitial growth

The process where cartilage grows from within through the division of chondrocytes and production of additional matrix.

Hydroxyapatite

Calcium phosphate crystals that constitute approximately $65\%$ of bone matrix and provide weight-bearing strength.

Osteoblasts

Bone-forming cells derived from osteochondral progenitor cells that produce bone matrix and surround themselves with matrix to become osteocytes.

Osteocytes

Mature bone cells residing within lacunae that connect to one another through cell processes housed in canaliculi.

Osteoclasts

Large bone-resorbing cells originating from stem cells in red bone marrow that break down bone matrix.

Woven bone

Immature bone tissue characterized by randomly oriented collagen fibers, which is subsequently remodeled into lamellar bone.

Lamellar bone

Mature bone tissue organized into thin layers called lamellae, containing parallel-oriented collagen fibers.

Cancellous bone

Spongy bone tissue consisting of an interconnecting lattice of trabeculae with spaces filled with bone marrow and blood vessels.

Trabeculae

Interconnecting beams of bone that form the structural lattice of cancellous bone, oriented along lines of stress.

Compact bone

Dense external layer of bone tissue consisting of highly organized lamellae with few spaces.

Osteon

The structural unit of compact bone, composed of concentric lamellae surrounding a central canal; also known as a Haversian system.

Diaphysis

The main tubular shaft forming the axis of a long bone, composed of compact bone surrounding a medullary cavity.

Epiphysis

The expanded terminal end of a long bone, featuring an outer layer of compact bone and an inner core of spongy bone.

Epiphyseal plate

A layer of hyaline cartilage separating the diaphysis from the epiphysis in growing bones, serving as the site of growth in bone length.

Periosteum

A double-layered membrane covering the outer surface of bone, consisting of an outer dense regular connective tissue layer and an inner osteogenic layer.

Endosteum

A delicate membrane lining internal surfaces of bone, containing osteoblasts, osteoclasts, and osteochondral progenitor cells.

Intramembranous ossification

The formation of bone directly within a fibrous connective tissue membrane, producing skull bones, parts of the mandible, and clavicle diaphyses.

Endochondral ossification

The formation of bone tissue by replacing a pre-existing hyaline cartilage model.

Fontanels

Unossified membrane-covered regions between skull bones present at birth in infants.

Basic multicellular unit (BMU)

A temporary assembly of osteoclasts and osteoblasts that tunnels through bone to carry out remodeling.

Parathyroid hormone (PTH)

The major regulator of blood $Ca^{2+}$ levels, secreted when blood $Ca^{2+}$ drops to indirectly stimulate osteoclast activity, renal calcium reabsorption, and active vitamin D synthesis.

Calcitonin

A hormone released by the thyroid gland in response to elevated blood $Ca^{2+}$ levels that inhibits osteoclast activity and decreases blood calcium.

Sella turcica

A saddle-shaped bony structure on the sphenoid bone within the cranial cavity that houses the pituitary gland.

Crista galli

A process in the anterior cranial fossa on the ethmoid bone to which the dura mater attaches.

Sutures

Fibrous joints between skull bones featuring interdigitating bone margins joined by dense fibrous connective tissue.

Syndesmoses

Fibrous joints in which bones are held together by fibrous ligaments, permitting slight movement.

Gomphoses

Fibrous joints in which peg-like structures fit into sockets and are anchored by periodontal ligaments, such as teeth in alveolar processes.

Synchondroses

Cartilaginous joints where bones are united by hyaline cartilage, such as epiphyseal plates.

Symphyses

Cartilaginous joints united by fibrocartilage that permit slight movement, such as intervertebral disks and the symphysis pubis.

Bursae

Fluid-filled sac extensions of synovial joints that reduce friction between skin, tendons, or bones.

Organic bone matrix

The portion of bone matrix composed of collagen fibers and proteoglycans, providing flexible strength and accounting for approximately $35\%$ of total bone mass.

Osteochondral progenitor cells

Stem cells derived from connective tissue that give rise to osteoblasts during bone formation and repair.

Canaliculi

Tiny canals radiating through bone matrix that house osteocyte cell processes, enabling intercellular communication and nutrient transport.

Perforating canals

Transverse channels carrying blood vessels and nerves from the periosteum or endosteum into central canals; also called Volkmann's canals.

Concentric lamellae

Circular rings of bone matrix surrounding the central canal within an osteon.

Circumferential lamellae

Layers of bone matrix that extend around the outer and inner perimeter of a compact bone shaft.

Interstitial lamellae

Remnants of partially resorbed osteons located in the spaces between active osteons.

Hematopoiesis

The physiological process of blood cell production occurring within the red bone marrow.

Medullary cavity

The central internal cavity of a long bone diaphysis filled with yellow bone marrow in adults.

Soft callus

A mass of fibers and cartilage formed by fibroblasts and chondroblasts that holds fractured bone ends together during repair.

Bone fracture repair stages

The four sequential steps of healing: 1. Hematoma formation, 2. Callus formation, 3. Callus ossification into cancellous bone, 4. Bone remodeling into compact bone.

Active Vitamin D

A hormone synthesized with PTH stimulation in the kidneys that promotes calcium absorption from the small intestine.

Axial skeleton

The central core framework of the body consisting of $80$ bones, including the skull, auditory ossicles, hyoid bone, vertebral column, and thoracic cage.

Appendicular skeleton

The skeletal division consisting of $126$ bones, comprising the upper limbs, lower limbs, pectoral girdle, and pelvic girdle.

Paranasal sinuses

Air-filled cavities within the frontal, sphenoid, ethmoid, and maxillary bones that open into the nasal cavity and lighten the skull.

Hard palate

Bony wall separating the oral and nasal cavities, formed anteriorly by maxillae palatine processes and posteriorly by palatine horizontal plates.

Hyoid bone

A solitary neck bone that does not articulate with any other bone, serving as an attachment point for muscles involved in tongue movement and swallowing.

Lordosis

An abnormal exaggerated anterior curvature of the lumbar spine.

Kyphosis

An abnormal exaggerated posterior curvature of the thoracic spine.

Scoliosis

An abnormal lateral curvature of the spinal column.

Intervertebral disk

A fibrocartilaginous pad between adjacent vertebrae containing a tough outer annulus fibrosus and a gelatinous inner nucleus pulposus.

Atlas (C1)

The first cervical vertebra that lacks a body and spinous process, articulating with the skull's occipital condyles to allow head nodding.

Axis (C2)

The second cervical vertebra featuring a dens (odontoid process) that acts as a pivot point for cranial rotation.

Transverse foramina

Passageways unique to cervical vertebrae that house the vertebral arteries supplying blood to the brain.

True ribs vs false ribs

Rib pairs 1-7 that attach directly to the sternum via costal cartilages, versus rib pairs 8-12 that attach indirectly or lack anterior attachment (floating ribs 11-12).

Sternum

The anterior thoracic breastbone consisting of the manubrium, body, and xiphoid process.

Glenoid cavity

The shallow depression on the lateral angle of the scapula that articulates with the humerus head to form the shoulder joint.

Acetabulum

The deep lateral socket of the coxal bone formed by the ilium, ischium, and pubis that articulates with the head of the femur.

Pelvic inlet differences by sex

Anatomical variation where the female inlet is oval and broader with a subpubic angle of $90^\circ$ or more, whereas the male inlet is heart-shaped with a subpubic angle under $90^\circ$.

Tibial tuberosity

An anterior elevation on the proximal tibia that serves as the attachment site for the patellar ligament.

Malleoli

Distal bony prominences at the ankle joint, consisting of the medial malleolus on the tibia and lateral malleolus on the fibula.

Synovial fluid

A viscous fluid produced by the inner membrane of a joint capsule that lubricates articular cartilages and reduces friction.