Tissues and Histology - Seeley BIOL 319 Lab/Lecture Notes (Chapter 04)

Vocabulary-style flashcards covering key concepts in tissues, histology, epithelial and connective tissues, muscle and nervous tissue, membranes, glands, inflammation, cancer, aging, and wound repair as presented in the lecture notes.

Tissue

A group of cells and/or fluids designed to perform a specific function.

Histology

Microscopic study of tissues.

Biopsy

Removal of tissue for diagnostic purposes by a pathologist; can indicate benign or malignant.

Autopsy

Postmortem examination of organs to determine cause of death.

Endoderm

Inner embryonic germ layer; forms lining of the GI tract and derivatives.

Mesoderm

Middle embryonic germ layer; forms muscle, bone, blood vessels, and other tissues.

Ectoderm

Outer embryonic germ layer; forms skin and neuroectoderm (neural crest cells give rise to peripheral nerves, skin pigments, adrenal medulla, and facial tissues).

Epithelial tissue

Tissues that cover body surfaces and line cavities; mostly cells; avascular; have apical, basal, and lateral surfaces; basement membrane; high regeneration.

Avascular

Lacking blood vessels; nourished by diffusion from underlying tissues.

Endothelium

A type of epithelium that lines the interior surfaces of blood and lymphatic vessels.

Basal lamina

Component of the basement membrane; contains lamina lucida and lamina densa; secreted by epithelial cells; rich in collagen, laminin, fibronectin, and proteoglycans.

Reticular lamina

Part of the basement membrane produced by underlying connective tissue; works with the basal lamina.

Basal surface

Surface of an epithelium that rests on the basement membrane.

Apical surface

Surface of an epithelium facing the lumen or external environment.

Goblet cells

Mucus-secreting cells in epithelia; contribute to defense by mucus production.

Carcinoma

Cancers arising from epithelial tissue; adenocarcinoma is glandular epithelial origin.

Simple epithelium

One cell layer thick; extends from basement membrane to free surface.

Pseudostratified columnar epithelium

Epithelium that appears multi-layered but all cells contact the basement membrane; often ciliated with goblet cells.

Transitional epithelium

Stratified epithelium that stretches; cuboidal when not stretched and squamous when stretched; lines urinary bladder, ureters, and part of urethra.

Stratified squamous epithelium

Multiple cell layers; surface cells flatten toward the apex; can be keratinized or nonkeratinized.

Simple squamous epithelium

Single layer of flattened cells; functions include diffusion and filtration; locations include vessels, alveoli, and kidney tubules.

Simple cuboidal epithelium

Single layer of cube-shaped cells; functions in secretion and absorption; locations include kidney tubules and glands.

Simple columnar epithelium

Single layer of tall, column-like cells; involved in secretion and absorption; may have microvilli or cilia.

Microvilli

Small projections that increase surface area for absorption/secretion.

Cilia

Hairlike structures that move mucus and trapped particles; part of the mucociliary escalator.

Stereocilia

Long, immotile projections (modified microvilli) in sensory cells of the inner ear.

Desmosomes

Cell–cell adhesion junctions (spot welds) that provide mechanical strength.

Hemidesmosomes

Junctions that attach epithelial cells to the basement membrane.

Tight junctions

Junctions that seal cells together to prevent passage between cells; create a permeability barrier.

Adhesion belts

Belt-like junctions (zonula adherens) below tight junctions that strengthen cell–cell adhesion.

Gap junctions

Protein channels allowing ions and small molecules to pass between cells; coordinate cell activity (important in cardiac and smooth muscle).

Endocrine glands

Glands that secrete hormones directly into the bloodstream; no ducts.

Exocrine glands

Glands that secrete into ducts that open to an external or internal surface (e.g., GI tract); many ducts.

Unicellular glands

Glands consisting of a single cell, e.g., goblet cells that secrete mucus.

Simple glands

Multicellular glands with a single, nonbranched duct; secretory portions may be tubular or acinar.

Compound glands

Multicellular glands with ducts that branch; secretory portions may be tubular or acinar or both.

Merocrine secretion

Secretions released by exocytosis; cells remain intact (e.g., salivary and pancreatic glands, some sweat glands).

Apocrine secretion

Secretory products accumulate at the apical part of the cell; a portion of the cell is shed (e.g., mammary glands).

Holocrine secretion

Secretions released by shedding entire cells (e.g., sebaceous glands).

Connective tissue (CT)

Tissue abundant in extracellular matrix; supports and binds other tissues; derived from mesoderm.

Extracellular matrix (ECM)

Noncellular component of CT consisting of protein fibers, ground substance, and fluid.

Collagen

Most abundant protein; provides strength and structural support; relatively inelastic.

Elastic fibers

Fibers containing elastin that allow tissues to stretch and recoil.

Ground substance

Hydrated gel in ECM; composed of hyaluronic acid, proteoglycans, and glycosaminoglycans.

Hyaluronic acid

Polysaccharide in ground substance; retains water and lubricates tissues.

Proteoglycans

Protein–polysaccharide complexes in ECM that trap water and provide resilience.

Glycosaminoglycans (GAGs)

Long polysaccharide chains that form part of proteoglycans; contribute to ECM hydration.

Adhesive molecules (ECM)

Proteins like fibronectin, chondronectin, osteonectin that help bind ECM to cells.

Areolar connective tissue

Loose CT with a loose network of fibers; provides support and nourishment.

Adipose tissue

Loose CT specialized for fat storage; adipocytes store triglycerides; energy reserve and insulation.

Reticular tissue

Loose CT with a fine network of reticular fibers; supports lymphoid and hemopoietic tissues.

Dense connective tissue

CT with densely packed fibers; includes dense regular, dense irregular, and dense elastic types.

Dense regular connective tissue

Collagen fibers arranged in parallel; forms tendons and ligaments; withstands pull in one direction.

Dense irregular connective tissue

Collagen fibers in multiple directions; provides tensile strength in many directions (e.g., dermis, organ capsules).

Dense elastic connective tissue

Dense CT with abundant elastic fibers; allows recoil (e.g., elastic arteries, ligaments of the vertebrae).

Cartilage

Avascular, aneural connective tissue with a semi-solid matrix; chondrocytes in lacunae.

Chondroblasts

Cells that form cartilage; differentiate into chondrocytes.

Chondrocytes

Mature cartilage cells housed in lacunae within the matrix.

Perichondrium

Dense irregular connective tissue surrounding cartilage; contains fibroblasts that can become chondroblasts.

Bone

Hard connective tissue with a mineralized matrix; osteoblasts build, osteocytes maintain, osteoclasts resorb.

Osteoblasts

Bone-forming cells that synthesize the organic matrix.

Osteocytes

Mature bone cells that maintain bone tissue within lacunae.

Osteoclasts

Bone-resorbing cells that break down bone matrix.

Osteon (Haversian system)

Structural unit of compact bone consisting of concentric lamellae around a central canal.

Spongy bone

Bone with trabeculae; lighter than compact bone; contains hemopoietic tissue in spaces.

Compact bone

Dense bone with an organized lamellar structure and central canals; strong supporting tissue.

Hematopoietic tissue

CT tissue in red marrow that produces blood cells; stimulated by EPO.

Red marrow

Hematopoietic tissue in bone marrow producing blood cells.

Yellow marrow

Marrow rich in adipose tissue; stores fat; limited blood cell production in adults.

Blood (fluid connective tissue)

Fluid CT with plasma as matrix and formed elements (RBCs, WBCs, platelets) for transport and defense.

Erythropoietin (EPO)

Hormone produced mainly by kidneys that stimulates red blood cell production.

Nervous tissue

Tissue of the nervous system consisting of neurons and supporting glial cells.

Neuron

Nerve cell capable of generating and conducting electrical impulses (action potentials).

Dendrites

Neuron processes that receive signals from other neurons.

Axon

Neuron process that transmits impulses away from the cell body.

Multipolar neuron

Neuron with many processes (multiple dendrites and a single axon); common in the CNS.

Bipolar neuron

Neuron with two processes (one dendrite, one axon); found in special sensory organs.

Pseudo-unipolar neuron

Neuron with a single process that splits into two; common in dorsal root and sensory ganglia.

Tissue membranes

Thin sheets of tissue that cover surfaces or line cavities; include mucous, serous, synovial, and cutaneous membranes.

Mucous membranes

Line cavities open to exterior; secrete mucus; contain goblet cells and lamina propria.

Serous membranes

Line closed cavities; produce serous fluid to reduce friction; mesothelium forms the lining.

Synovial membranes

Line freely movable joints; secrete lubricating synovial fluid rich in hyaluronic acid.

Cutaneous membrane

Skin; a dry membrane forming a barrier against the external environment.

Inflammation

Protective response with five signs: redness, heat, swelling, pain, disturbs function; involves mediators like histamine, prostaglandins, leukotrienes.

Histamine

Chemical mediator released during inflammation that increases vascular permeability and causes vasodilation.

Prostaglandins

Group of lipid mediators involved in inflammation and pain; potent vasodilators and permeability factors.

Leukotrienes

Inflammatory mediators contributing to increased vascular permeability and leukocyte recruitment.

Edema

Swelling caused by excess fluid in interstitial spaces during inflammation.

Epidermal Growth Factor (EGF)

Protein that stimulates cell growth and differentiation via EGFR; involved in skin repair.

EGF receptor (EGFR)

Cell surface receptor for EGF; mediates EGF signaling.

Carcinomas

Cancers arising from epithelial tissues.

Adenocarcinomas

Cancers derived from glandular epithelium.

Sarcomas

Cancers arising from mesoderm-derived tissues (connective and muscular tissue).

Aging effects on tissues

Age-related changes include slower cell division, reduced remodeling, less elasticity, wrinkling, and reduced tissue perfusion.

Inflammatory stages (three core steps)

Vasodilation and increased permeability; leukocyte recruitment; clot formation and debris clearance initiating repair.

Regeneration vs. Replacement

Regeneration restores tissue by making new cells of the same type; replacement forms a different tissue (scar).

Labile vs Stable vs Permanent cells

Categories of cells by regenerative capacity: Labile (continuous mitosis), Stable (low turnover but can divide after injury), Permanent (little or no regenerative capacity).

Wound repair: primary vs secondary union

Primary union: wound edges close; secondary union: edges not closed; more inflammation and scarring.

Granulation tissue

Delicate connective tissue with fibroblasts, collagen, and capillaries that replaces a clot during healing.