Histology of Supporting and Special Connective Tissues: Cartilage, Bone, and Adipose Tissue

Comprehensive vocabulary flashcards covering the histological classification, structural organization, cellular types, and functional features of cartilage, bone, and adipose tissues.

Supporting Connective Tissue

A functional category of connective tissue characterized by high mechanical resistance and structural rigidity, comprising cartilaginous tissue and bone tissue.

Special Properties Connective Tissue

Specialized types of connective tissue that fulfill specific systemic roles, including adipose tissue, elastic tissue, hematopoietic/reticular tissue (lymphoid and myeloid), and mucous tissue.

Chondroblasts

Immature cartilage cells located at the periphery of the cartilage tissue that actively synthesize matrix and differentiate into chondrocytes.

Chondrocytes

Mature cartilage cells that reside individually or in isogenous groups within extracellular matrix cavities termed lacunae.

Cartilage Extracellular Matrix

The intercellular substance of cartilage composed of collagen fibers and/or elastic fibers embedded in a ground substance rich in proteoglycans and adhesive glycoproteins such as fibronectin and laminin.

Perichondrium

A sheath of dense irregular connective tissue covering most cartilage; it provides vascular supply, oxygenation, nutrient and metabolite exchange, and serves as a source of new chondroblasts for appositional growth.

Hyaline Cartilage

The most common cartilage type, composed of type II collagen fibrils and surrounded by perichondrium (except on articular surfaces); found in the nasal fossa walls, trachea, bronchi, and articular surfaces of long bones.

Elastic Cartilage

Cartilage characterized by an abundant network of elastic fibers (elastin) alongside type II collagen fibrils, a less abundant matrix, and a perichondrium; found in the epiglottis, pinna of the ear, and external acoustic meatus.

Fibrocartilage

A transitional cartilage containing dense type I collagen bundles and chondrocytes arranged in linear rows, completely lacking a perichondrium; located in intervertebral discs, pubic symphysis, and menisci.

Conducting Portion (Respiratory System)

The series of flexible conduits that transport, warm, and humidify air, encompassing the nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles (with diameters up to $1\,\text{mm}$).

Respiratory Portion (Respiratory System)

The distal regions of the respiratory tract where gas exchange occurs, comprising respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Respiratory Epithelium

A pseudostratified ciliated columnar epithelium containing mucus-secreting goblet cells (células caliciformes) lining the conducting airways.

Tracheal Lamina Propria

The subepithelial layer of loose connective tissue in the trachea containing seromucous glands (glândulas seromucosas) and a rich vascular network.

Tracheal Cartilaginous Ring

Incomplete C-shaped rings of hyaline cartilage in the tracheal wall whose open posterior ends are bridged by smooth muscle tissue.

Tracheal Adventitia

The outermost layer of the trachea composed of loose connective tissue containing blood vessels, nerves, and adipose cells.

Compact Bone

Dense, solid osseous tissue that forms the outer protective shell of bones, characterized by a lack of macroscopic cavities.

Spongy Bone

Cancellous bone tissue structured as a 3D porous network of interconnected bony trabeculae enclosing bone marrow cavities.

Hematogenous Bone Marrow

Red bone marrow composed of hematopoietic tissue actively engaged in blood cell production; predominantly fills marrow cavities in newborns.

Yellow Bone Marrow

Inactivated bone marrow dominated by adipose tissue with reduced hematopoietic activity.

Periosteum

A dense fibrous connective tissue layer covering the external surface of bones, containing osteoprogenitor cells essential for bone growth and repair.

Endosteum

A thin cellular connective tissue layer lining the internal surfaces of bone, Haversian canals, and marrow cavities, containing osteoprogenitor cells.

Osteoblasts

Mononucleated bone-forming cells that synthesize and secrete the organic components of bone matrix (osteoid) and coordinate matrix mineralization.

Osteocytes

Mature bone cells derived from osteoblasts trapped in their own mineralized matrix, occupying small spaces called lacunae.

Osteoclasts

Giant, multinucleated bone-resorbing cells derived from the fusion of monocyte/macrophage precursor cells, essential for bone remodeling.

Organic Bone Matrix

The unmineralized fraction of bone matrix consisting predominantly of type I collagen fibers, proteoglycans, and structural glycoproteins.

Inorganic Bone Matrix

The mineralized fraction of bone matrix composed mainly of calcium and phosphate salts deposited as hydroxyapatite crystals, providing extreme hardness.

White Adipocyte

A unilocular fat cell characterized by a single large lipid droplet occupying the cytoplasm, a peripherally flattened nucleus, low mitochondrial density, absence of UCP1, and functions in energy storage as well as secretion of leptin and adiponectin.

Brown Adipocyte

A multilocular fat cell containing numerous small lipid droplets, a centrally located nucleus, high mitochondrial density, and positive expression of UCP1; specialized in non-shivering thermogenesis and secretion of FGF21.

Brite (Beige) Adipocyte

An inducible adipocyte found interspersed within white adipose tissue depots, possessing multilocular lipid droplets, medium mitochondrial density, and positive UCP1 expression.

Uncoupling Protein 1 (UCP1)

An inner mitochondrial membrane transport protein present in brown and beige adipocytes that dissipates the proton gradient to generate heat instead of ATP.

Adipose-Derived Stem Cells (ASCs)

Multipotent mesenchymal stromal/stem cells located within the vascular stromal fraction of adipose tissue (representing approximately $30\%$ of tissue cells) capable of differentiating into adipocytes and other lineages.