Histology and Tissues Lecture Review

Flashcards covering histology, including the four primary tissue types (epithelial, connective, muscular, and nervous), their subtypes, structures, and functions.

Histology

The study of tissues, also known as microscopic anatomy.

Organ

A structure with discrete boundaries composed of two or more tissue types.

Ectoderm

The outer primary germ layer that gives rise to the epidermis and the nervous system.

Endoderm

The inner primary germ layer that gives rise to mucous membranes, the GI tract, respiratory linings, and digestive glands.

Mesoderm

The middle primary germ layer that forms mesenchyme and gives rise to muscle, bone, and blood.

Basement membrane

A layer at the basal surface of cells that anchors epithelium to underlying connective tissue.

Simple epithelium

A type of epithelium that contains only one layer of cells and is named by the shape of those cells.

Stratified epithelium

A type of epithelium containing more than one layer of cells, named by the shape of the apical (top) cells.

Pseudostratified Epithelium

A structure with a single row of cells where not all reach the free surface, with nuclei at different levels; it secretes and propels mucus.

Keratinized Stratified Squamous

Epithelium covered with compact, squamous cells without nuclei, packed with the protein keratin; it forms the epidermal layer of skin.

Nonkeratinized Stratified Squamous

A multilayered epithelium that lacks a surface layer of dead cells, forming a moist, slippery layer in locations like the tongue, esophagus, and vagina.

Transitional Epithelium

A multilayered epithelium with rounded surface cells that allow for stretches and distension; found in the urinary tract.

Glycosaminoglycans (GAGs)

Polysaccharides in the ground substance of connective tissue that attract sodium and hold water.

Proteoglycan

A bottlebrush-shaped molecule that forms a thick gel to slow the spread of pathogens in connective tissue.

Collagen fibers

Known as white fibers, these are the most abundant proteins in the body; they are thick, tough, flexible, and resist stretch.

Elastic fibers

Known as yellow fibers, these allow for elasticity and recoil like a rubber band; found in skin, lungs, and arteries.

Reticular fibers

Thin collagen fibers coated with glycoprotein that form the framework for the spleen and lymph nodes.

Fibroblasts

Connective tissue cells that produce fibers and ground substance.

Macrophages

Large phagocytic cells that arise from monocytes and function in phagocytosis.

Mast cells

Oval-shaped cells clustered along blood vessels that secrete heparin and histamine.

Adipocytes

Fat cells that store triglycerides.

Loose Connective Tissue

A category of fibrous connective tissue that contains more gel-like ground substance between cells; includes areolar, reticular, and adipose tissue.

Areolar Tissue

A loose arrangement of collagenous and elastic fibers with abundant ground substance; underlies all epithelia.

Dense Regular Connective Tissue

Connective tissue consisting mainly of densely packed, parallel fibers with compressed fibroblast nuclei; located in tendons and ligaments.

Dense Irregular Connective Tissue

Tissue with collagen fibers running in different directions to withstand stresses applied in many directions; found in the capsules around organs and the deeper skin.

Chondrocytes

Cartilage cells that result when chondroblasts surround themselves with matrix.

Osseous tissue

Bone tissue, which can be spongy (filling heads of long bones) or compact (solid external surfaces).

Skeletal muscle

Voluntary muscle tissue that is striated and attaches to bone, skin, or fascia.

Cardiac muscle

Involuntary, striated muscle tissue with branching fibers and a built-in pacemaker.

Smooth muscle

Involuntary, nonstriated muscle tissue found in the walls of hollow organs like blood vessels and the GI tract.

Sarcolemma

The cell membrane of a muscle fiber.

Myoglobin

A red-colored, oxygen-binding protein found in the sarcoplasm of muscle cells.

Sarcoplasmic Reticulum (SR)

A system of tubular sacs that stores $Ca^{2+}$ in relaxed muscle and releases it to trigger contraction.

Sarcomeres

Compartments separated by Z discs where thick and thin filaments overlap, forming the functional unit of muscle contraction.

Rigor mortis

A state of muscular rigidity starting 3-4 hours after death because $Ca^{2+}$ leaks from the SR and ATP synthesis has ceased.

Neuromuscular Junction (NMJ)

The synapse or myoneural junction where an axon terminal nears the motor end plate of a muscle fiber.

Perikaryon

Also called the cell body or soma, it is the trophic center of the neuron containing the nucleus and cytoplasm.

Nissl bodies

Granular material in the neuronal cytoplasm that stains intensely with basic dyes; also called Nissl granules.

Neurofibrils

Thin black fibers observed in neurons with silver nitrate stains, composed of microtubules and filaments.

Dendrites

Short branching neurites that carry impulses toward the soma and contain Nissl granules.

Axon

A single long process arising from the axon hillock that carries impulses away from the cell body.

Axon hillock

A special region of the neuron cell body from which the axon arises; it is devoid of Nissl bodies.

Collaterals

Branches of an axon that arise near the cell body and lie at right angles to the axon.