Histo Test 1 Pt 2

Comprehensive vocabulary flashcards covering the structural characteristics, cell types, functions, and clinical correlations of cartilage, bone, muscle, and nervous tissues.

Hyaline Cartilage

An avascular connective tissue containing type II collagen fibers and a matrix rich in proteoglycan aggregates, located in the trachea, bronchi, ventral ends of ribs, nose, articular surfaces, and epiphyseal plates.

Elastic Cartilage

A flexible type of cartilage containing type II collagen and abundant elastic fibers, located in the epiglottis, larynx, and pinna of the ear.

Fibrocartilage

A type of cartilage lacking a perichondrium that contains both type I and type II collagen fibers to provide high tensile strength and compression resistance, located in the pubic symphysis and intervertebral disks.

Perichondrium

A layer of dense connective tissue surrounding hyaline and elastic cartilage that provides the nearest blood supply and supplies chondrogenic cells for appositional growth.

Appositional Growth

A mechanism of cartilage growth where new matrix is deposited on the surface of pre-existing cartilage by chondroblasts derived from the inner layer of the perichondrium.

Interstitial Growth

A mechanism of cartilage growth where chondrocytes within lacunae divide and secrete new extracellular matrix, increasing cartilage volume from within.

Osteoarthritis

A degenerative joint disease of older individuals characterized by progressive loss of hyaline articular cartilage, altered joint shape, rough articular surfaces, and type II collagen present in the synovial fluid.

Osteoid

An uncalcified organic bone matrix secreted by osteoblasts, composed of type I precollagen, proteoglycans, and glycoproteins including osteocalcin, osteonectin, and osteopontin.

Hydroxyapatite Crystals

Inorganic mineral crystals with the formula $Ca_{10}(PO_4)_6(OH)_2$ that make up approximately 65% of the dry weight of mineralized bone matrix.

Osteoblast

A cuboidal or low columnar bone-forming cell derived from osteoprogenitor cells that synthesizes and deposits osteoid (prebone).

Osteocyte

A mature bone cell enclosed within a lacuna that maintains bone matrix, extending narrow cytoplasmic processes through canaliculi to communicate with neighboring cells via gap junctions.

Osteoclast

A large, multinucleated cell derived from monocytes that resides in Howship lacunae and functions in bone resorption and remodeling.

Parathyroid Hormone (PTH)

A hormone secreted by chief cells of the parathyroid gland that increases blood $Ca^{2+}$ levels by indirectly stimulating osteoclasts, inhibiting osteoblasts, and increasing calcium absorption in the GI tract and kidneys.

Calcitonin

A hormone secreted by parafollicular (C) cells of the thyroid gland that decreases blood $Ca^{2+}$ levels by directly inhibiting osteoclast activity and reducing bone resorption.

Osteon (Haversian System)

The structural unit of compact bone consisting of concentric lamellae of bone matrix surrounding a central Haversian canal that carries blood vessels and nerves.

Periosteum

A connective tissue layer covering the external surface of bone consisting of an outer dense fibrous collagenous layer and an inner osteogenic layer containing osteoprogenitor cells, attached to bone via Sharpey fibers.

Endochondral Ossification

The process of bone development in long bones where a hyaline cartilage model proliferates, calcifies, and is systematically replaced by bone across epiphyseal plate zones.

Intramembranous Ossification

Direct bone development where mesenchymal cells differentiate into osteoblasts and deposit osteoid without a precursor cartilage model, forming flat bones such as those of the facial skeleton and skull.

Sarcomere

The functional contractile unit of a myofibril bounded by two Z lines, containing overlapping thick (myosin) and thin (actin) myofilaments.

Skeletal Muscle Triad

A structural feature in skeletal muscle consisting of one transverse (T) tubule flanked by two terminal cisternae of the sarcoplasmic reticulum located at the A-I band junction.

Triad vs. Dyad Structural Comparison

Skeletal muscle contains a Triad (one T tubule + two terminal cisternae of sarcoplasmic reticulum), whereas cardiac muscle contains a Dyad (one T tubule + one terminal cisterna of sarcoplasmic reticulum).

Sarcoplasmic Reticulum

A specialized form of smooth endoplasmic reticulum in muscle cells that serves as the storage site and release reservoir for cellular calcium ions.

Dystrophin

A muscle cytoplasmic protein located between the sarcolemma and actin filaments that links the muscle cytoskeleton to extracellular collagen fibers, protecting the membrane during contraction.

Duchenne Muscular Dystrophy (DMD)

An inherited genetic disorder caused by mutations in the dystrophin gene, leading to skeletal muscle degeneration, variable fiber diameters, centrally displaced nuclei, endomysial fibrosis, and muscle weakness.

Muscle Spindle

An encapsulated stretch receptor containing intrafusal muscle fibers (nuclear chain and nuclear bag fibers) that monitors muscle length, changes in length, and rate of stretch.

Golgi Tendon Organ

A sensory receptor located at myotendinous junctions that detects changes in muscle tension and mediates a protective reflex against excessive muscle load.

Intercalated Disk

A specialized step-like junctional complex connecting adjacent cardiac muscle cells that contains fascia adherens, macula adherens (desmosomes), and gap junctions.

Dense Body

An intracytoplasmic structure containing ̑\alpha-actinin in smooth muscle cells that anchors actin filaments, serving a role analogous to Z lines in striated muscle.

Caveolae

Membrane invaginations or lipid rafts in smooth muscle cells that participate in the uptake and release of calcium ions during muscle contraction.

Peripheral Nerve Connective Tissue Sheaths

Connective tissue coverings of PNS nerves: the Epineurium (dense irregular CT surrounding the entire nerve), Perineurium (surrounding fascicles to form a blood-nerve barrier), and Endoneurium (delicate CT surrounding each individual axon).

Schwann Cell

The neuroglial cell of the peripheral nervous system responsible for forming the myelin sheath around individual myelinated axons or supporting groups of unmyelinated axons.

Oligodendrocyte

The neuroglial cell of the central nervous system that forms myelin sheaths around segments of multiple adjacent axons.

Posterior Root Ganglion (PRG)

A sensory ganglion located on the dorsal nerve root containing pseudounipolar neurons with central nuclei, surrounded by satellite cells, carrying sensory signals without synaptic relays.

Sympathetic Chain Ganglion

An autonomic ganglion containing multipolar neurons with eccentric nuclei and scattered satellite cells, serving as a site for synapses between preganglionic and postganglionic motor fibers.

Submucosal (Meissner) Plexus

An enteric autonomic ganglion plexus located in the submucosal layer of the gastrointestinal tract that regulates mucosal movement and secretions.

Myenteric (Auerbach) Plexus

An enteric autonomic ganglion plexus located between the inner circular and outer longitudinal smooth muscle layers of the gastrointestinal tract that controls GI motility and peristalsis.

Meissner Corpuscle

An encapsulated cutaneous sensory receptor situated in dermal papillae that detects light touch and low-frequency vibrations.

Pacinian Corpuscle

A large, encapsulated sensory receptor located deep in the dermis or hypodermis consisting of concentric connective tissue lamellae that responds to deep pressure and high-frequency vibrations.

Cerebral Cortex Layers

The six histological layers of gray matter in the cerebrum: Molecular (I), External Granular (II), External Pyramidal (III), Internal Granular (IV), Internal Pyramidal (V), and Multiform (VI).

Cerebellar Cortex Layers

The three distinct layers of gray matter in the cerebellum: the outer Molecular layer, middle Purkinje cell layer, and inner Granule cell layer.

Satellite Cells (Muscle)

Adult stem cells situated between the sarcolemma and basal lamina of skeletal muscle fibers that proliferate and differentiate to repair damaged muscle.

Myasthenia Gravis

An autoimmune disorder characterized by autoantibodies against acetylcholine receptors at the neuromuscular junction, leading to muscle weakness, wider synaptic clefts, and shallower subjunctional folds.

Node of Ranvier

An unmyelinated gap along a myelinated axon between adjacent Schwann cells where high concentrations of voltage-gated channels enable saltatory impulse conduction.