Glossary of Anatomy Chapter 4: Tissues
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- A group of cells that are similar in structure and perform a common or related function.
- Tissue Types (name)
- Epithelial, connective, muscle, nervous.
- Epithelial Tissue
- Covering tissue. A sheet of cells that covers a body surface or lines a body cavity. Forms boundaries between different environments. As an interface tissue, it protects, absorbs, filters, excretes, secretes, and participates in sensory reception.
Occurs in the body and covering/lining and glandular tissue.
- Characteristics of Epithelium
- Cellularity, specialized contacts (tight junctions and desmosomes), polarity, supported by connective tissue (basement membrane), avascular but innervated, high regenerative capacity.
- Apical Surface
- Upper free surface exposed to the body exterior or the cavity of an internal organ.
- Basal Surface
- Lower, attached surface of a polarized cell.
- Basal Lamina
- Thin, noncellular, adhesive sheet adjacent to the basal surface of an epithelium. Consists largely of glycoproteins secreted by epithelial cells.
Acts as a selective filter that determines which molecules diffusing from underlying connective tissue will be allowed to enter the epithelium.
- Reticular Lamina
- Layer of extracellular material containing a fine network of collagen fibres that "belongs to" the underlying connective tissue.
- Basement Membrane
- Basal lamina + reticular lamina. Reinforces the epithelial sheet and defines the epithelial boundary.
- Simple Epithelia
- Epithelium composed of a single layer of cells.
Found where absorption and filtration occur.
- Stratified Epithelia
- Epithelium consisting of two or more cell layers stacked one on top of the other.
Common in high-abrasion areas.
- Squamous Cells
- Flattened, scalelike epithelial cells with flattened nuclei.
- Cuboidal Cells
- Boxlike epithelial cells with round nuclei.
- Columnar Cells
- Tall epithelial cells with elongated nuclei.
- Naming of Epithelia
- *Number of layers (simple v. stratified)
*Type of cells (squamous, cuboidal, columnar)
*****Stratified epithelia are named according to the shape of the cells in the apical layer*****
- Simple Squamous Epithelium
- Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm. Simplest of the epithelia. Includes endothelium and mesothelium.
Function: Allows passage of materials by diffusion and filtration in sites where protection is not important. Secretes lubricating substances in serosae.
Location: kidney glomeruli, air sacs of lungs, lining of heart/blood vessels/lymphatic vessels, serosae
- Simple squamous epithelium which provides a slick, friction-reducing lining in lymphatic vessels and in blood vessels/heart.
- Simple squamous epithelium found in serous membranes lining the ventral body cavity and covering its organs.
- Simple Cuboidal Epithelium
- Single layer of boxlike cells with large, spherical central nuclei.
Function: Secretion and absorption.
Location: Kidney tubules, ducts and secretory portion of small glands, ovarian surfaces.
- Simple Columnar Epithelium
- Single layer of tall cells with round to oval nuclei. Some cells bear cilia. Layer may contain mucus-secreting unicellular glands (goblet cells).
Function: Absorption, secretion of mucus/enzymes/etc., ciliated type propels mucus or reproductive cells.
Location: Nonciliated--lining of digestive tract, gallbladder, excretory ducts of glands
Ciliated--lining of small bronchi, uterine tubes, uterus
- Pseudostratified Columnar Epithelium
- Single layer of cells of differing heights, some not reaching the free surface. Nuclei seen at different levels. May contain goblet cells and bear cilia.
Function: Secretion. Propulsion of mucus by ciliary action.
Location: Nonciliated--sperm carrying ducts, ducts of large glands
Ciliated--lining of trachea and upper respiratory tract
- Stratified Squamous Epithelium
- Thick membrane composed of several cell layers. Basal cells are cuboidal or columnar and metabolically active. Surface cells are squamous.
Function: Protects underlying tissues in areas subject to abrasion.
Location: linings of esophagus, mouth, and vagina. Epidermis of the skin (nonkeratinized).
- Stratified Cuboidal Epithelium
- Rare, boxlike, multilayered epithelium. Usually 2 layers of cuboidal cells. Found mostly in the ducts of the larger glands.
- Stratified Columnar Epithelium
- Stratified epithelium whose apical layer is columnar. Limited in distribution. Found in the pharynx, male urethra, and lining of some glandular ducts. Also occurs at transition areas or junctions between two other types of epithelia.
- Transitional Epithelium
- Epithelium which resembles both stratified squamous and stratified cuboidal epithelia. Basal cells are cuboidal or columnar. Surface cells are squamouslike/domelike.
Function: Stretches readily and permits distension of urinary organ.
Location: Lines ureters, bladder, and urethra.
- One or more cells that make and secrete a particular product (mostly water).
- Endocrine Glands
- Ductless glands that produce hormones.
- Exocrine glands
- Glands which secrete their products onto body surfaces or into body cavities.
- Unicellular Exocrine Glands
- Goblet cells. Produce mucin.
- Complex glycoprotein that dissolves in water to form mucus.
- Multicellular Exocrine Glands
- Glands consisting of epithelium-derived ducts and a secretory unit consisting of secretory cells.
Classified based on structure (simple/compound) and secretory unit type (tubular/alveolar/tubuloalveolar) and mode of secretion (merocrine/holocrine)
- Simple Glands
- Glands possessing unbranched ducts
- Compound Glands
- Glands possessing branched ducts.
- Tubular Glands
- Glands with secretory cells that form tubes
- Alveolar Glands
- Glands which have secretory cells that form small, flask-like sacs
- Tubuloalveolar/Acinar Glands
- Glands which have both types of secretory units.
- Merocrine Glands
- Glands which secrete their products by exocytosis. The secretory cells are not altered in any way.
- Holocrine Glands
- Glands which accumulate their products within them until they lyse.
(Oil glands of the skin = only real example)
- Connective Tissue
- Most abundant and widely distributed of the primary tissues. Major function include binding/support, protection, insulation, and transportation of substances within the body
- Characteristics of Connective Tissue
- Common origin as mesenchyme, varying degrees of vascularity, largely made of nonliving extracellular matrix.
- Ground Substance
- Unstructured material that fills the space between connective tissue cells and contains the fibres. Composed of interstitial fluid, cell adhesion proteins, and proteoglycans.
- Major classes of connective tissue
fibroblast / chondroblast/ osteoblast/ hematopoietic stem cell
fibrocyte / chondrocyte / osteocyte / blood cells & macrophages
connective tissue proper / cartilage / osseous (bone) / blood
loose connective tissue (areolar/adipose/reticular) & dense connective tissue (regular/irregular/elastic) / hyaline cartilage & fibrocartilage & elastic cartilage / compact bone & spongy bone / (blood stuff)
- Connective Tissue Fibres
- Provide support in connective tissue. Part of the connective tissue matrix. Three types: collage, elastic, & reticular.
- Collagen Fibres
- Connective tissue fibres constructed primarily of the fibrous protein collagen. Extremely tough and provide high tensile strength to the matrix.
- Elastic Fibres
- Long, thin fibres that form branching networks in the extracellular matrix. Made of rubberlike protein elastic that allows them to stretch and recoil.
- Reticular Fibres
- Fine collagenous fibres of the connective tissue matrix which are continuous with collagen fibres. Branch extensively, forming delicate networks that surround small blood vessels and support the soft tissue organs. Particularly abundant where connective tissue abuts other tissue types (eg: reticular lamina).
- Connective Tissue Proper Subclasses
- Loose connective tissue
Dense connective Tissue
- Loose Connective Tissue Types
- areolar, adipose, and reticular
- Dense Connective Tissue Types
- dense regular, dense irregular, elastic
- Areolar Connective Tissue
- Loose connective tissue type. Gel-like matrix with all three fibre types. Fibroblasts, macrophages, mast cells, and some WBC's.
Function: Wraps and cushions organs, phagocytize bacteria, plays role in inflammation, holds/conveys tissue fluid.
Location: Widely distributed under epithelia of body, packages organs, surrounds capillaries.
- Adipose Tissue
- Loose connective tissue. Matrix as in areolar, but very sparse. Closely packed fat cells. Nucleus pushed to the side by large fat droplets.
Function: Provides reserve food fuel. Insulates against heat loss. Supports and protects organs.
Location: Under skin, around kidneys/eyeballs, within abdomen/breasts.
- Fat cells.
- Reticular Connective Tissue
- Loose connective tissue type. Network of reticular fibres in a typical loose ground substance. Reticular cells lie on the network.
Function: Fibres form a soft internal skeleton that supports other cell types including WBC's mast cells, and macrophages.
Location: lymphoid organs
- Dense Regular Connective Tissue
- Dense connective tissue type. Primarily parallel collagen fibres, a few elastin fibres. Major cell type = fibroblast.
Function: Attaches muscles to bones or to muscles. Withstands great tensile stress when pulling force is applied in one direction.
Location: Tendons, most ligaments, aponeuroses.
- Dense Irregular Connective Tissue
- Dense connective tissue type. Primarily irregularly arranged collagen fibres, some elastic fibres. Major cell type = fibroblast.
Function: Able to withstand tension exerted in many directions. Provides structural strength.
Location: Dermis, submucosa of digestive tract, fibrous capsules of organs/joints.
- Cartilage Types
- hyaline, fibrocartilage, elastic cartilage
- Hyaline Cartilage
- Cartilage type. Amorphous but firm matrix. Collagen fibres form an imperceptible network. Chondroblasts produce the matrix when the mature chondrocytes lie in lacunae.
Function: Supports and reinforces. Has resilient cushioning properties. Resists compressive stress.
Location: Embryonic skeleton. Covers the ends of long bones in joint cavities. Forms costal cartilages & cartilages of the nose, trachea, and larynx.
- Elastic Cartilage.
- Cartilage type. Similar to hyaline cartilage, but more elastic fibres in matrix.
Function: Maintains the shape of a structure while allowing great flexibility.
Location: External ear, epiglottis
- Cartilage Type. Matrix similar to but less firm than that of hyaline cartilage. Thick collagen fibres predominate.
Function: Tensile strength with the ability to absorb compressive shock.
Location: Intervertebral discs, pubic symphysis, discs of knee joint.
- Osseous Tissue
- Bone. Hard, calcified matrix containing many collagen fibres. Osteocytes lie in lacunae. Very well vascularized.
Function: Bone supports and protects. Provides levers for the muscles to act upon. Stores Ca and other minerals and fat. Marrow inside bones it he site for blood cell formation.
- RBC's and WBC's in a fluid (plasma) matrix.
Function: Transport of respiratory gases, nutrients, wastes, and other substances.
Location: Contained within heart and blood vessels.
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