Anatomy and Physiology: Skeletal System, Integumentary System, and Arthrology

Comprehensive vocabulary flashcards covering the skeletal system, integumentary system, and arthrology based on chapters 6, 7, and 9 of Anatomy & Physiology: An Integrative Approach.

Compact Bone

Dense or cortical bone connective tissue that appears white, smooth, and solid, accounting for approximately $80\%$ of total bone mass.

Spongy Bone

Cancellous or trabecular bone connective tissue located internal to compact bone that appears porous and accounts for approximately $20\%$ of total bone mass.

Bone Classification by Shape

The four structural categories of bones based on shape: long bones (e.g., femur), short bones (e.g., tarsal bone), flat bones (e.g., frontal bone), and irregular bones (e.g., vertebra).

Diaphysis

The elongated, cylindrical shaft of a long bone that provides leverage and weight support, containing compact bone with spicules of spongy bone extending inward.

Gross Anatomy of a Long Bone

The major regions of a long bone, including the proximal and distal epiphyses, metaphysis, cylindrical diaphysis, medullary cavity, periosteum, and articular cartilage.

Medullary Cavity

The hollow, cylindrical space within the diaphysis of a long bone that contains red bone marrow in children and yellow bone marrow in adults.

Epiphyseal Plate

A growth plate located in the metaphysis consisting of a thin layer of hyaline cartilage that permits lengthwise bone growth during childhood and narrows into an epiphyseal line upon skeletal maturity.

Periosteum

A tough sheath covering the outer bone surface composed of an outer fibrous layer of dense irregular connective tissue and an inner cellular layer of bone cells, secured to bone by perforating fibers.

Endosteum

An incomplete cellular layer lining all internal surfaces of bone within the medullary cavity, containing osteoprogenitor cells, osteoblasts, and osteoclasts.

Diploë

The internal layer of spongy bone sandwiched between two layers of compact bone within the flat bones of the skull.

Red Bone Marrow

Hemopoietic tissue containing stem cells that produce blood cells and platelets; located in the spongy bone and medullary cavities of children, but restricted in adults to selected axial skeleton bones and proximal epiphyses of the humerus and femur.

Yellow Bone Marrow

A fatty substance formed from the degeneration of red bone marrow as individuals mature; it stores lipids and can convert back to red bone marrow during severe anemia.

Osteoprogenitor Cells

Mesenchymal stem cells residing in the periosteum and endosteum that divide to yield another stem cell and a committed cell that matures into an osteoblast.

Osteoblasts

Cuboidal cells derived from osteoprogenitor cells that synthesize and secrete osteoid; they become entrapped within matrix to differentiate into osteocytes.

Osteocytes

Mature bone cells that reside in lacunae, maintain the extracellular bone matrix, and detect mechanical stress to trigger matrix deposition.

Osteoclasts

Large, multinucleated phagocytic cells derived from fused bone marrow cells located in resorption lacunae; they have a ruffled border and secrete enzymes and hydrochloric acid to break down bone matrix.

Bone Cells Lineage and Function

The cell types of bone connective tissue: osteoprogenitor cells giving rise to matrix-secreting osteoblasts, which differentiate into matrix-maintaining osteocytes, alongside multinucleated bone-resorbing osteoclasts.

Osteoid

The initial semisolid organic form of bone matrix synthesized by osteoblasts, composed of collagen protein and a ground substance of proteoglycans and glycoproteins that provides tensile strength and flexibility.

Hydroxyapatite

Inorganic salt crystals with the formula $\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2$, formed when calcium phosphate precipitates with calcium hydroxide around collagen fibers to harden bone matrix.

Osteon

The basic microscopic functional and structural unit of mature compact bone oriented parallel to the diaphysis, composed of concentric lamellae arranged around a central canal.

Canaliculi

Tiny interconnecting channels within bone connective tissue that travel through lamellae between lacunae and the central canal, housing osteocyte cytoplasmic projections.

Perforating Canals

Vascular canals (Volkmann canals) that run perpendicular to central canals, carrying blood vessels and nerves to link central canals of distinct osteons.

Compact and Spongy Bone Microscopic Organization

The microscopic architecture of bone showing circular osteons with central canals in compact bone alongside the porous crisscrossing trabeculae of spongy bone.

Interstitial Cartilage Growth

Internal cartilage growth in length occurring when chondrocytes in lacunae divide into chondroblasts, synthesize new matrix, push apart, and develop into individual chondrocytes.

Appositional Cartilage Growth

Cartilage growth in width occurring at the outer boundary when stem cells within the perichondrium divide and differentiate into chondroblasts that deposit new matrix at the periphery.

Intramembranous Ossification

Bone formation within thickened regions of mesenchyme that produces flat bones of the skull, facial bones, the mandible, and the central part of the clavicle.

Endochondral Ossification

Bone formation initiating from a fetal hyaline cartilage model during the $8\text{th to }12\text{th week}$ of development that produces most bones of the skeleton, including limb bones, vertebrae, pelvis, and ends of clavicles.

Calcitriol Activation

The three-step metabolic pathway where UV light converts $7\text{-dehydrocholesterol}$ to vitamin $\text{D}_3$ in skin, which is converted to calcidiol in the liver and then converted to active calcitriol in the kidneys.

Parathyroid Hormone

A hormone secreted by the parathyroid glands in response to low blood calcium levels that works synergistically with calcitriol to stimulate osteoclast activity and reduce renal calcium loss in urine.

Calcitonin

A hormone released from the thyroid gland in response to high blood calcium levels or exercise that inhibits osteoclast activity and stimulates renal excretion of calcium.

Osteopenia

A normal age-related loss of bone mass and mineral density beginning between ages $35\text{ and }40$, caused by a reduction in osteoblast activity while osteoclast activity remains steady.

Osteoporosis

A clinical condition characterized by severe reduction in bone mass sufficient to compromise normal physical function, resulting in weakened bones highly prone to fracture.

Four Stages of Bone Fracture Repair

The sequential steps of fracture healing: $1\text{)}$ fracture hematoma forms; $2\text{)}$ fibrocartilaginous (soft) callus forms; $3\text{)}$ hard (bony) callus forms; $4\text{)}$ bone is remodeled by osteoclasts and osteoblasts.

Integument

The skin; the body's largest organ, accounting for $7\text{ to }8\%$ of body weight, composed of a superficial stratified squamous epithelium (epidermis) and deeper connective tissue (dermis).

Layers of the Integument

The anatomical organization of the skin showing the superficial epidermis, the underlying dermis (papillary and reticular layers), and the deeper subcutaneous hypodermis.

Stratum Basale

The deepest epidermal stratum consisting of a single layer of cuboidal to low columnar cells contacting the basement membrane; contains dividing keratinocyte stem cells, melanocytes, and tactile cells.

Epidermal Dendritic Cells

Immune cells (Langerhans cells) located in the stratum spinosum and stratum granulosum that phagocytize pathogens and initiate immune responses against microbes and cancer cells.

Stratum Lucidum

A clear, translucent layer composed of $2\text{ to }3$ layers of dead, anucleate keratinocytes filled with eleidin; found exclusively in thick skin on palms and soles.

Stratum Corneum

The most superficial epidermal layer consisting of $20\text{ to }30$ layers of dead, interlocking, anucleate, keratin-filled keratinocytes that form a dry, protective barrier against pathogens.

Friction Ridges

Epidermal skin ridges on palms, fingers, soles, and toes formed by interlocking epidermal ridges and dermal papillae that produce arch, whorl, loop, and combination patterns for traction and identification.

Papillary Layer

The superficial layer of the dermis composed of areolar connective tissue that forms dermal papillae interdigitating with epidermal ridges to anchor the epidermis.

Reticular Layer

The deeper, major portion of the dermis composed of dense irregular connective tissue surrounding hair follicles, sebaceous glands, sweat glands, nerves, and blood vessels.

Subcutaneous Layer

Also called the hypodermis or superficial fascia; a tissue layer deep to the dermis composed of areolar and adipose connective tissue that pads the body, acts as an energy reservoir, and provides thermal insulation.

Eponychium

The cuticle; a narrow band of epidermis extending from the margin of the nail wall onto the proximal surface of the nail body.

Nail Matrix

The actively growing, thickened portion of the stratum basale located at the proximal end of the nail bed from which new nail cells are generated.

Hair Structure and Follicle

The structural anatomy of a hair (pilus) showing the hair shaft, root, hair bulb with hair papilla, surrounding epithelial and connective tissue root sheaths, and the arrector pili muscle.

Arrector Pili

Thin ribbons of smooth muscle extending from the hair follicle to dermal papillae that contract in response to emotional states or cold temperature, causing hair elevation and 'goosebumps'.

Merocrine Sweat Glands

Simple coiled tubular glands that release a watery solution ($99\%$ water and $1\%$ salts and wastes) directly onto the epidermal surface via exocytosis for thermoregulation.

Apocrine Sweat Glands

Coiled tubular sweat glands located in the axillary, pubic, and anal regions that release a viscous, cloudy secretion containing lipids and proteins into hair follicles via exocytosis starting at puberty.

Sebaceous Glands

Holocrine exocrine glands associated with hair follicles that produce oily sebum to lubricate and waterproof hair and skin, stimulated by androgens at puberty.

Stages of Integumentary Wound Healing

The repair process of cutaneous injury: $1\text{)}$ cut blood vessels bleed into the wound; $2\text{)}$ blood clot forms and leukocytes clean the wound; $3\text{)}$ blood vessels regrow and granulation tissue forms; $4\text{)}$ epithelium regenerates and fibrosis occurs.

Synarthrosis

A functional class of joint that is completely immobile; includes fibrous joints such as gomphoses and sutures, as well as cartilaginous synchondroses.

Amphiarthrosis

A functional class of joint that is slightly mobile; includes fibrous syndesmoses and cartilaginous symphyses.

Diarthrosis

A functional class of joint that is freely mobile; includes all synovial joints in the body.

Gomphosis

A specialized 'peg-in-a-socket' fibrous synarthrosis where a tooth root is anchored into the alveolar sockets of the mandible or maxilla by periodontal membranes.

Suture

An immobile fibrous synarthrosis found between cranial skull bones characterized by short dense connective tissue fibers and interlocking irregular edges that ossify into synostoses with age.

Syndesmosis

A fibrous amphiarthrosis in which articulating bones (such as the radius and ulna, or tibia and fibula) are bound by a broad sheet of dense regular connective tissue termed an interosseous membrane.

Synchondrosis

An immobile cartilaginous joint (synarthrosis) where articulating bones are united by hyaline cartilage, exemplified by epiphyseal plates and costochondral joints.

Symphysis

A cartilaginous amphiarthrosis containing a broad pad of fibrocartilage that resists compression and functions as a shock absorber, such as the pubic symphysis and intervertebral discs.

Synovial Joint Anatomy

The structural features of a synovial articulation: articular cartilage, a fluid-filled joint cavity, reinforcing ligaments, and a double-layered articular capsule consisting of an outer fibrous layer and an inner synovial membrane.

Synovial Fluid

A viscous, oily fluid secreted by the synovial membrane that lubricates articular surfaces, provides nutrients to avascular chondrocytes, and absorbs shock during joint motion.

Bursae

Closed, fibrous saclike structures lined internally by synovial membrane and filled with synovial fluid that reduce friction where bones, ligaments, tendons, or muscles rub against one another.

Circumduction

An angular movement in which the proximal end of an appendage remains relatively stationary while the distal end traces a wide circular path, generating an imaginary cone shape.

Opposition

A special movement at the carpometacarpal joint of the hand whereby the pad of the thumb moves toward the tips of the fingers to enable grasping of objects.

Talocrural Joint

A highly modified synovial hinge joint composed of two articulations (distal tibia with talus, and distal fibula with talus) that exclusively permits dorsiflexion and plantar flexion.

Osteoarthritis

A degenerative joint disease typically associated with aging and wear-and-tear in which the articular cartilage breaks down, commonly affecting the fingers, hips, knees, and shoulders.

Rheumatoid Arthritis

An autoimmune disorder occurring more commonly in younger to middle-aged adults, especially women, which begins with chronic inflammation of the synovial membrane.