Ch. 4 Tissue: Lecture 5-6

Epithelial tissue

Lines body surfaces, forms boundaries between body spaces, and forms glands

Connective tissue

Supports, protects, and connects other structures together

Muscle tissue

Responsible for movement in the body

Nervous tissue

Transmits electrochemical signals throughout the body to coordinate functions

Epithelium

Sheet or membrane of cells covering body surfaces and cavities or forming glands

Lining epithelium

Epithelium that covers body surfaces and cavities

Glandular epithelium

Epithelium that forms glands

Function of epithelium

Protection of deeper tissue, absorption and filtration, secretion (glands), sensory reception (nerve endings embedded within epithelia)

Polarity of epithelium

The organization of epithelial cells into distinct apical and basal sides

Apical side

Side of an epithelial cell facing the external environment or lumen

Lumen

Space within a tube duct or gland

Basal side

Side of an epithelial cell facing deeper layers of connective tissue

Cell-to-cell adhesions of epithelium

Adjacent cells are joined mainly by tight junctions and desosome

Basement membrane

Structure that separates epithelium from deeper connective tissue, made up of basal lamina and reticular lamina

Basal lamina

Very thin sheet-like part of the basement membrane

Reticular lamina

Web-like network of fibers in the basement membrane

Characteristics of epithelium

polarity, cell-to-cell adhesions, supported by basement membrane, avascular but highly innervated, regenerative (stimulated by loss of polarity of contact with adjacent cells

Microvilli

Finger-like extensions of the apical cell membrane that increase surface area for absorption, non motile

Cilia

Extensions of the apical cell membrane that use whip-like motion to propel material along the cell surface. Typically longer than microvilli, motile

Simple epithelium

Epithelium consisting of one cell layer

Stratified epithelium

Epithelium consisting of more than one cell layer

Squamous

Flat cell shape

Cuboidal

Square-shaped cell shape

Columnar

Tall rectangular cell shape

Simple squamous epithelium

Single layer of flat cells specialized for rapid diffusion. Found in lungs, blood vessels, kidneys

Simple cuboidal epithelium

Single layer of square or rounded cells involved mainly in secretion and absorption. Found mainly lining glands and ducts

Simple columnar epithelium

Single layer of tall elongated cells (often with microvilli or cilia) involved in absorption, secretion, and mucus propulsion when ciliated. Found in digestive tract, smaller airways in lungs, uterus

Stratified squamous epithelium

Multiple cell layers with flat squamous cells at the apical surface

Non-keratinized stratified squamous epithelium

Stratified squamous epithelium forming a wet protective lining against abrasion. Apical: flat, squamous cells; basal: cuboidal or columnar in shape, actively undergoing mitosis. Found in oral cavity, esophagus, vagina, anal canal

Keratinized stratified squamous epithelium

Stratified squamous epithelium with a superficial layer of dead keratinized cells forming a dry water-repellant barrier. No nuclei on apical surface, most superficial layer of skin

Stratified cuboidal epithelium

Usually only two cell layers, rare and usually found in ducts of glands such as sweat and salivary glands

Stratified columnar epithelium

Apical layer: columnar; basal layer: cuboidal. Rare epithelium found in areas including the conjunctiva of eye, glands ,and male urethra and vas deferens

Transitional epithelium

Made up of cuboidal and columnar cell shapes, found in urinary structures that stretch and relax (bladder). Apical layer of cells is bulging, club-shaped when unstretched, but flattened out when stretched.

Pseudostratified columnar epithelium

Single layer of columnar cells of different heights that appears stratified because nuclei are at different levels. Nuclei at different levels, but all cells in contact with basal membrane. Function in absorption, secretion, propels mucus (if ciliated). Ciliated type found in airways, non-ciliated type found in epidydimis and vas deferens

Endocrine gland

Gland that releases substances directly into the bloodstream

Exocrine gland

Gland that releases substances into body cavities or onto the surface of the skin

Duct

Structure through which most exocrine glands release their products

Simple exocrine gland

Exocrine gland with an unbranched duct

Compound exocrine gland

Exocrine gland with a branched duct

Tubular gland

Exocrine gland with an elongated tubular secretory portion

Alveolar gland

Exocrine gland with a round grape-like secretory portion

Merocrine secretion

Secretion of products by exocytosis

Holocrine secretion

Secretion in which cells die and disintegrate to release their products

Apocrine secretion

Secretion in which the apical portion of the cell pinches off and the damaged portion regenerates

Goblet cell

Unicellular mucin-producing exocrine gland

Mucin

Substance produced by goblet cells that combines with water to form mucus

Mucus

Mucin combined with water

Connective tissue

Tissue derived from mesenchyme with cells embedded in extracellular matrix

Mesenchyme

Embryonic tissue composed of gel-like ground substance fibers and undifferentiated stem cells

Extracellular matrix

Material surrounding connective tissue cells consisting of ground substance and fibers

Ground substance

Gel-like material occupying the interstitial space of connective tissue

Collagen fibers

Fibers that provide tensile strength

Elastic fibers

Fibers that allow tissues to stretch and recoil

Reticular fibers

Fibers that form a structural network

Blast cells

Immature connective tissue cells that produce ground substance and fibers

Cyte cells

Mature connective tissue cells that maintain the extracellular matrix

Adipocyte

Cell specialized for storing fat

Fibroblast

Connective tissue cell that produces ground substance and fibers

Areolar connective tissue

Loose connective tissue that provides support and binds other tissues together

Lamina propria

Layer of loose areolar connective tissue just deep to epithelium

Adipose connective tissue

Loose connective tissue with closely packed lipid-filled adipocytes

Adipose tissue functions

Energy storage insulation heat generation and shock absorption

Reticular connective tissue

Connective tissue made primarily of reticular fibers that forms a structural network

Stroma

Web-like structural network that supports other cells

Dense regular connective tissue

Connective tissue with closely packed parallel collagen fibers providing high strength under tension

Dense irregular connective tissue

Connective tissue with collagen fibers arranged in multiple directions to resist tension in multiple directions

Elastic connective tissue

Connective tissue with densely packed elastic fibers that provides stretch and recoil

Cartilage

Firm but flexible connective tissue containing chondrocytes in lacunae

Chondrocyte

Mature cartilage cell located in a lacuna

Lacuna

Space containing a chondrocyte within cartilage

Hyaline cartilage

Most abundant cartilage type found at ends of bones nose and walls of airways

Elastic cartilage

Cartilage with a higher proportion of elastic fibers that allows stretching while maintaining original shape

Fibrocartilage

Cartilage with rows of chondrocytes between collagen fibers that withstands both tension and compression

Bone

Connective tissue with calcified matrix that supports and protects body tissues

Osteoblast

Cell that produces and calcifies bone matrix

Osteocyte

Cell that maintains bone matrix

Osteoclast

Cell that removes bone matrix

Osteon

Structural unit of bone

Blood

Connective tissue with plasma as ground substance and blood cells and platelets as cellular components

Plasma

Fluid ground substance of blood

Cutaneous membrane

Dry body membrane forming the outer surface of the skin

Epidermis

Epithelial layer of the cutaneous membrane consisting of keratinized stratified squamous epithelium

Dermis

Connective tissue layer beneath the epidermis

Mucous membrane

Wet membrane lining cavities that open to the external environment

Mesothelium

Simple squamous epithelium lining serous membranes

Serous membrane

Wet membrane lining closed ventral body cavities

Myofilaments

Protein filaments made of actin and myosin that produce muscle contraction

Actin

Contractile protein found in myofilaments

Myosin

Contractile protein found in myofilaments

Skeletal muscle

Voluntary striated muscle made of multinucleated cylindrical cells with peripheral nuclei

Smooth muscle

Involuntary non-striated muscle made of uninucleate spindle-shaped cells

Cardiac muscle

Involuntary striated muscle made of uninucleate branching cells found in the heart

Tissue repair

Process by which damaged tissue is repaired following injury

Inflammation

Initial response to tissue damage involving inflammatory signals and increased blood vessel permeability

Clot

Structure that initially seals a damaged site during tissue repair

Granulation tissue

Tissue containing an ingrowing capillary network that restores blood supply to a damaged area

Fibroblast activity during tissue repair

Fibroblasts secrete growth factors and collagen fibers near the damaged area

Fibrotic scar tissue

Scar tissue that remains deep to the epithelium depending on the extent of the wound