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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
Quiz – Next Quiz – Next time!time!
I will be checking study guides up to 1-
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