Tissues: The living fabric Ch 4 a Epithelial Tissue

Tissues: Tissues: The living fabricThe living fabric

Ch 4 aEpithelial Tissue

Tissues

• Histology = Study of tissues• Tissue = Groups of cells

similar in structure and function

• The four types of tissues–Epithelial - covering–Connective - support–Muscle - movement–Nerve - control

Epithelial Tissue

•2 types–Covering and lining epithelium

–Glandular epithelium

Epithelial TissueEpithelial Tissue

Covering and lining epithelium

Epithelial Tissue

•A sheet of cells that covers a body surface or lines a body cavity

•Forms boundaries between different environments

Epithelial Tissue Functions

•Protection•Absorption•Filtration•Excretion•Secretion (from glands)

•Sensory reception

Characteristics of Epithelial Tissue

•Cellularity – composed almost entirely of cells–Very little extracellular material

•Special contacts – form continuous sheets held together by tight junctions and desmosomes

Characteristics of Epithelial Tissue

•Polarity – apical and basal surfaces–Apical = free upper surface exposed to exterior of body or cavity (some are slick, some have cilia, most have microvilli)

–Basal = lower surface attached

Characteristics of Epithelial Tissue

•Basal surface attached to basement membrane–basal laminae – thin, adhesive, non-cellular

–reticular laminae – fine network of collagen fibers belonging to the connective tissue underneath, non-cellular

Characteristics of Epithelial Tissue

•All epithelial tissue are supported by and rest upon connective tissue

Characteristics of Epithelial Tissue

•Avascular but innervated – contains no blood vessels but supplied by nerve fibers – nourished by diffusion

•Regenerative – rapidly replaces lost cells by cell division

Classification of Epithelia

•Simple •stratified

Figure 4.1a

Classification of Epithelia

•Squamous

•Cuboidal

•Columnar

Figure 4.1b

Epithelia: Simple Squamous

•Single layer of flattened cells with disc-shaped nuclei and sparse cytoplasm

Epithelia: Simple Squamous

•Functions –Diffusion and filtration–Provide a slick, friction-reducing lining in lymphatic and cardiovascular systems

•Present in the kidneys, lungs, lining of heart, blood vessels, lymphatic vessels

Epithelia: Simple Squamous

Figure 4.2a

Epithelia: Simple Cuboidal

•Single layer of cubelike cells with large, spherical central nuclei

•Function in secretion and absorption

•Present in kidney tubules, ducts and secretory portions of small glands, and ovary surface

Epithelia: Simple Cuboidal

Figure 4.2b

• Single layer of cubelike cells with large, spherical central nuclei

• Function in secretion and absorption• Present in kidney tubules, ducts and

secretory portions of small glands, and ovary surface

Epithelia: Simple Columnar

•Single layer of tall cells with oval nuclei; many contain cilia

•Goblet cells are often found in this layer

–Cells that secrete a protective lubricating mucus

•Function in absorption and secretion

Epithelia: Simple Columnar

•Nonciliated type line digestive tract and gallbladder

•Ciliated type line small bronchi, uterine tubes, and some regions of the uterus

•Cilia help move substances through internal passageways

Epithelia: Simple Columnar

Figure 4.2c

Epithelia: Pseudostratified Columnar

•Single layer of cells with different heights; some do not reach the free surface

•Nuclei are seen at different layers

Epithelia: Pseudostratified Columnar

•Function in secretion and propulsion of mucus

•Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated)

Epithelia: Pseudostratified Columnar

Figure 4.2d

• Single layer of cells with different heights; some do not reach the free surface

• Nuclei are seen at different layers• Function in secretion and propulsion of

mucus• Present in the male sperm-carrying

ducts (nonciliated) and trachea (ciliated)

Epithelia: Stratified Squamous

•Thick membrane composed of several layers of cells

•Function in protection of underlying areas subjected to abrasion

Epithelia: Stratified Squamous

•Forms the external part of the skin’s epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells)

Epithelia: Stratified Squamous

Figure 4.2e

• Thick membrane composed of several layers of cells

• Function in protection of underlying areas subjected to abrasion

• Forms the external part of the skin’s epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells)

Epithelia: Stratified Cuboidal

•Stratified cuboidal–Quite rare in the body–Found in some sweat and mammary glands

–Typically two cell layers thick

Epithelia: Stratified Columnar

•Stratified columnar –Limited distribution in the body–Found in the pharynx, male urethra, and lining some glandular ducts

–Also occurs at transition areas between two other types of epithelia

Epithelia: Transitional

•Several cell layers, basal cells are cuboidal, surface cells are dome shaped

•Stretches to permit the distension of the urinary bladder

•Lines the urinary bladder, ureters, and part of the urethra

Epithelia: Transitional

Figure 4.2f

• Several cell layers, basal cells are cuboidal, surface cells are dome shaped

• Stretches to permit the distension of the urinary bladder

• Lines the urinary bladder, ureters, and part of the urethra

Epithelial TissueEpithelial Tissue

Glandular Epithelia

Epithelia: Glandular

• A gland is one or more cells that makes and secretes an aqueous fluid

Epithelia: Glandular

• Glands Classified by:–Site of product release –

•Endocrine (internally secreting) or Exocrine (externally secreting)

–Relative number of cells forming the gland – •Unicellular (one cell) & Multicellular (many cells)

Endocrine Glands

•Ductless glands that produce hormones

•Secretions include amino acids, proteins, glycoproteins, and steroids

Exocrine Glands

•More numerous than endocrine glands

•Secrete their products onto body surfaces (skin) or into body cavities

Exocrine Glands

•Examples include mucous, sweat, oil, and salivary glands, the liver (which secrets bile), the pancreas (which secrets enzymes) and others

Unicellular Exocrine Glands

•The only important unicellular exocrine gland is the goblet cell–Found in linings of intestinal and respiratory tracts

–Secrets mucus

Multicellular Exocrine Glands

•Multicellular exocrine glands are composed of a duct and secretory unit

•Classified according to:–Simple or compound duct type–Structure of their secretory units

Figure 4.3a-d

Structural Classification of Multicellular Exocrine

Glands

Structural Classification of Multicellular Exocrine

Glands

Figure 4.3e-g

Modes of Secretion•Merocrine – products are

secreted by exocytosis (e.g., pancreas, sweat, and salivary glands)

•Holocrine – products are secreted by the rupture of gland cells (e.g., sebaceous glands)

Modes of Secretion

Figure 4.4Merocrine Holocrine

• http://www.youtube.com/watch?v=7z2vYr5YjD8

Simple cuboidal epithelium

Simple cuboidal epithelium

Transitional epithelium

Transitional epithelium

Pseudostratified epithelium

Stratified squamous epithelium

What tissue is

this?

Simple columnar epithelial tissue

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8

• Ap = tip• Areola = space• Basal =

foundation• Blast = forming• Chyme = juice• Crine = separate• Endo = within• Epi = upon, over• Glia = glue

• Holo = whole• Hormon = excite• Hyal = glass• Lamina = thin

plate• Mero = part• Meso = middle• Retic = network• Sero = watery fluid• Squam = a scale• Strat = layer