Anatomy and Physiology I: Tissues, Integumentary System, Bone Tissue, and the Skeletal System

Comprehensive vocabulary flashcards covering Human Tissues (Chapter 5), the Integumentary System (Chapter 6), Bone Tissue (Chapter 7), and the Skeletal System (Chapter 8).

Histology

The microscopic study of tissues.

Endoderm

The innermost primary embryonic germ layer that gives rise to the digestive and reproductive tracts, including many internal organs.

Mesoderm

The middle primary embryonic germ layer that gives rise to muscle tissue, bone tissue, and other connective tissues.

Ectoderm

The outermost primary embryonic germ layer that gives rise to the epidermis, nervous system, hair, and nails.

Simple Squamous Epithelium

A single row of thin, flat cells that permits rapid diffusion or transport of substances and secretes serous fluid; located in alveoli, glomeruli, endothelium, and serosa.

Simple Cuboidal Epithelium

A single layer of square or cube-like cells specialized for absorption, secretion, and mucus production; found in the thyroid, kidney tubules, liver, and salivary glands.

Simple Columnar Epithelium

A single row of tall, slender cells with oval nuclei in the basal half, featuring an apical brush border of microvilli and often goblet cells; lines the GI tract, uterus, and uterine tubes.

Pseudostratified Epithelium

An epithelium that appears multilayered due to nuclei located at several depths, but in which all cells touch the basement membrane; possesses cilia and goblet cells to secrete and propel mucus.

Nonkeratinized Stratified Squamous Epithelium

A multilayered abrasion-resistant epithelium lacking a surface layer of dead cells; found lining moist internal passages such as the esophagus, vagina, tongue, and oral mucosa.

Urothelium (Transitional Epithelium)

A multilayered epithelium whose apical cells change from rounded to flattened when stretched; permits expansion and filling of the urinary bladder and ureter.

Areolar Connective Tissue

A loose connective tissue with randomly organized fibers, abundant ground substance, and blood vessels; found in the upper dermis, serous membranes, and around neurovascular bundles.

Reticular Connective Tissue

A supportive network of branching reticular fibers and fibroblasts that forms the stroma (framework) of lymphatic organs such as the spleen, lymph nodes, thymus, and bone marrow.

Dense Regular Connective Tissue

A type of connective tissue composed of densely packed, parallel collagen fibers with compressed fibroblast nuclei; forms tendons and ligaments.

Dense Irregular Connective Tissue

A connective tissue containing randomly arranged, densely packed collagen bundles with few visible cells; withstands unpredictable multi-directional stresses in the deep dermis and organ capsules.

Hyaline Cartilage

A glassy-appearing cartilage with fine collagen fibers that eases joint movement, keeps airways open, and facilitates bone growth in juveniles; located at articular surfaces, costal cartilages, and the trachea.

Fibrocartilage

A tough cartilage containing coarse, visible bundles of parallel collagen fibers that absorbs shock and resists compression; located in the intervertebral discs, pubic symphysis, and menisci.

Cardiomyocytes

Short, branched, striated cardiac muscle cells with a single centrally located nucleus, joined end-to-end by intercalated discs.

Intercalated Discs

Specialized complex intercellular junctions that join individual cardiomyocytes together in cardiac muscle tissue.

Neuroglia (Glial Cells)

Non-conducting supportive cells of the nervous system that protect, nourish, and assist neurons.

Tight Junction

A cell junction formed by the fusion of outer plasma membrane proteins between adjacent cells, sealing off the intercellular space to prevent substance leakage.

Desmosome

A patch-like intercellular junction with protein plaques and intermediate filaments that fastens cells together, enabling tissues to resist mechanical stress.

Gap Junction

A communicating cell junction composed of ring-like connexons surrounding a central water-filled pore, allowing ions and small solutes to pass directly between cells.

Holocrine Gland

An exocrine gland whose secretory cells accumulate products until they disintegrate and die, releasing the entire cellular contents as the secretion.

Hyperplasia

Tissue growth accomplished through an increase in cell number via mitosis.

Hypertrophy

Tissue growth accomplished through the enlargement of preexisting cells rather than an increase in cell number.

Atrophy

The shrinkage of a tissue through a loss in cell size or cell number, often resulting from normal aging or disuse.

Necrosis

Pathological tissue death resulting from trauma, toxins, or infection.

Fibrosis

The replacement of damaged or dead cells with nonfunctional collagenous scar tissue, holding organs together without restoring original function.

Dermatology

The medical branch specializing in the care, diagnosis, and treatment of skin disorders.

Dendritic (Langerhans) Cells

Antigen-presenting immune macrophages originating in bone marrow that migrate to the epidermis to guard against pathogens.

Tactile (Merkel) Cells

Specialized sensory receptors for touch situated in the basal layer of the epidermis, paired with an underlying dermal nerve fiber.

Stratum Lucidum

A translucent, featureless fifth epidermal layer found exclusively in thick skin (palms and soles), situated between the stratum corneum and stratum granulosum.

Dermal Papillae

Upward, finger-like extensions of the dermis that interlock with downward epidermal ridges to prevent epidermal slipping.

Reticular Layer of Dermis

The deeper and thicker zone of the dermis composed of dense irregular connective tissue; tearing of its collagen fibers results in stretch marks (striae).

Eumelanin

The brownish-black form of the melanin pigment synthesized by melanocytes to protect epidermal DNA from ultraviolet radiation.

Pheomelanin

A sulfur-containing, reddish-yellow variant of melanin pigment found in red hair and fair skin.

Cyanosis

An abnormal blueness of the skin resulting from a deficiency of oxygen in circulating blood.

Jaundice

A yellow discoloration of the skin and whites of the eyes caused by elevated bilirubin levels resulting from compromised liver function.

Hematoma

A bruise; a mass of clotted blood trapped under the skin usually caused by trauma or impact.

Friction Ridges

Markings on fingertips, palms, and soles formed during fetal development that leave unique fingerprints and enhance friction.

Lanugo

Fine, unpigmented, downy hair that appears on the fetus during the last three months of development.

Vellus Hair

Fine, pale hair that replaces lanugo by birth and covers two-thirds of the female body and one-tenth of the male body.

Terminal Hair

Coarse, heavily pigmented hair forming the scalp, eyebrows, and eyelashes, as well as axillary and pubic hair after puberty.

Arrector Pili (Piloerector) Muscle

A bundle of smooth muscle cells extending from dermal collagen fibers to the connective tissue root sheath of a hair follicle; contracts to pull the hair erect (producing goose bumps).

Alopecia

Abnormal thinning or baldness of the hair, potentially worsened by disease, poor nutrition, or emotional stress.

Hirsutism

Excessive or undesirable hairiness in areas that are typically not hairy, especially in women and children.

Eponychium (Cuticle)

A narrow zone of dead skin that overhangs the proximal end of the nail plate.

Bromhidrosis

Disagreeable body odor produced by the bacterial breakdown of fatty acids in apocrine gland secretions.

Diaphoresis

Copious sweating accompanied by noticeable wetness of the skin, with losses up to $1\,\text{L}$ per hour during exercise.

Cerumen

Earwax; a yellow, waxy secretion composed of sebum and dead epidermal cells that repels water and coats the auditory canal.

Basal Cell Carcinoma

The most common and least dangerous form of skin cancer, originating from cells of the stratum basale and presenting as a shiny bump with central depression and beaded edges.

Squamous Cell Carcinoma

A malignant skin cancer arising from keratinocytes of the stratum spinosum; appears as a raised, scaly, reddened lesion that can metastasize to regional lymph nodes.

Malignant Melanoma

The most lethal form of skin cancer, accounting for less than $5\%$ of cases, which arises from melanocytes and has a strong familial risk factor.

Eschar

Burned, dead tissue resulting from severe burns whose toxic effects and infection risk necessitate debridement.

Third-Degree Burn (Full-Thickness Burn)

A severe burn involving the complete destruction of the epidermis, the entire dermis, and often deeper muscle or bone tissue, requiring skin grafting and fluid replacement.

Autograft

A tissue graft transplanted from one site to another on the same person's body.

Osteology

The study of bone tissue and the skeletal system.

Diaphysis

The elongated cylinder or shaft of a long bone that provides leverage for locomotion.

Epiphysis

An expanded head located at each distal and proximal end of a long bone, serving to strengthen joints and anchor ligaments.

Epiphyseal Plate

A hyaline cartilage zone at the metaphysis of growing long bones where lengthwise (interstitial) elongation occurs, persisting in adults as an epiphyseal line.

Periosteum

A two-layered sheath enveloping the external surface of a bone, containing an outer fibrous collagen layer and an inner osteogenic cellular layer.

Endosteum

A thin layer of reticular connective tissue lining the internal marrow cavity and honeycombed surfaces of spongy bone.

Osteoblasts

Bone-building cells that synthesize and secrete the organic components of bone matrix (osteogenesis) and promote mineralization.

Osteocytes

Former osteoblasts that have become entrapped within lacunae of the calcified matrix; act as strain sensors to regulate bone remodeling.

Osteoclasts

Large, multinucleated bone-dissolving cells developed from hematopoietic stem cells that dissolve osseous tissue at a ruffled border.

Hydroxyapatite

A crystallized calcium phosphate salt ($\text{Ca}_{10}(\text{PO}_4)_6(\text{OH})_2$) constituting approximately $85\%$ of the inorganic matter of bone matrix.

Osteon (Haversian System)

The basic structural and functional unit of compact bone, composed of concentric lamellae arranged around a central canal containing blood vessels.

Intramembranous Ossification

The process of bone development directly within embryonic mesenchymal membranes; produces the flat bones of the skull, the clavicles, and part of the mandible.

Endochondral Ossification

The process of bone development in which a pre-existing hyaline cartilage model is broken down and replaced by osseous tissue.

Achondroplastic Dwarfism

A genetic condition caused by a dominant allele failure of cartilage growth in the metaphyses, resulting in short limbs with a normal-sized torso.

Wolff's Law of Bone

The physiological principle stating that the architecture and density of bone are determined by the mechanical stresses placed upon it.

Calcitriol

The hormonally active form of vitamin D synthesized by sequential actions of skin, liver, and kidneys that acts to raise blood calcium levels.

Calcitonin

A peptide hormone secreted by the clear (C) cells of the thyroid gland in response to hypercalcemia, acting to lower blood calcium concentration.

Parathyroid Hormone (PTH)

A hormone secreted by the parathyroid glands during hypocalcemia that raises blood calcium by activating osteoclasts, stimulating calcitriol synthesis, and conserving renal calcium.

Hypocalcemia

A blood calcium deficiency (plasma concentration below $9.2\,\text{mg/dl}$) that increases nervous system excitability and induces muscle tetany.

Rickets

A childhood disorder characterized by soft, deformed bones resulting from vitamin D or calcitriol deficiency.

Pathological Fracture

A bone fracture caused by stress on a bone already weakened by an underlying disease such as osteoporosis or cancer.

Fracture Repair

A four-stage healing sequence consisting of hematoma formation, soft callus formation, hard callus formation, and bone remodeling.

Osteoporosis

The most common metabolic bone disorder, marked by a severe loss of bone density, porous trabeculae, and vulnerability to pathological fractures.

Axial Skeleton

The skeletal division forming the central supporting axis of the body, including the skull, vertebral column, sternum, ribs, sacrum, coccyx, and hyoid.

Appendicular Skeleton

The skeletal division comprising the limbs and the girdles (pectoral and pelvic) that attach them to the axial skeleton.

Sesamoid Bones

Small rounded bones that develop within tendons in response to strain, the largest of which is the patella.

Sutural (Wormian) Bones

Small extra island bones that develop along the suture lines between larger cranial bones.

Fontanelles

Fibrous membrane-covered spaces between unfused cranial bones in infants that allow deformation during birth and rapid brain growth.

Sella Turcica

A saddle-shaped saddle-like depression in the sphenoid bone that houses and protects the pituitary gland.

Crista Galli

A vertical median blade of the ethmoid bone that projects superiorly into the anterior cranial fossa to attach to the dura mater.

Hyoid Bone

A U-shaped bone in the anterior neck suspended from the styloid processes that does not articulate with any other bone; fracture indicates strangulation.

Scoliosis

An abnormal lateral deviation of the vertebral column, most commonly occurring in the thoracic region of adolescent girls.

Hyperkyphosis

An exaggerated posterior thoracic curvature of the spine (hunchback), typically caused by osteoporosis, osteomalacia, or spinal tuberculosis.

Hyperlordosis

An exaggerated anterior lumbar curvature of the spine (swayback), commonly resulting from pregnancy or obesity.

Nucleus Pulposus

The gelatinous, water-rich inner core of an intervertebral disc that distributes compressive forces and absorbs shock.

Anulus Fibrosus

The ring of fibrocartilage forming the tough outer perimeter of an intervertebral disc that confines the inner gelatinous core.

Atlas (C1)

The first cervical vertebra, which lacks a body and spinous process, articulating with the occipital condyles to enable the head-nodding gesture for 'yes'.

Axis (C2)

The second cervical vertebra, characterized by a prominent superior projection called the dens, allowing head rotation for the gesture 'no'.

Dens (Odontoid Process)

A prominent tooth-like vertical projection arising from the anterosuperior side of the axis (C2) around which the atlas pivots.

Glenoid Cavity

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

Carpal Bones

Eight small bones of the wrist arranged in two transverse rows: scaphoid, lunate, triquetrum, and pisiform proximally; trapezium, trapezoid, capitate, and hamate distally.

Pollex

The thumb, which contains only two phalanges (proximal and distal) compared to the three present in other digits.

Acetabulum

The deep, cup-shaped socket on the lateral surface of the hip bone where the ilium, ischium, and pubis fuse; articulates with the head of the femur.

Pubic Symphysis

The cartilaginous joint in the anterior pelvis where the two pubic bones meet and are united by an interpubic disc of fibrocartilage.