1 Chapter 5 Tissues – Epithelial

2 Introduction Similar cells with a common function are called tissues. The study of tissues is called histology. There are four (4) primary or major tissue types: 1. Epithelial Tissue (covering/lining; ET) 2. Connective Tissue (support; CT) 3. Muscle Tissue (movement; MT) 4. Nervous Tissue (control; NT)

Figure 4.1 Nervous tissue: Internal communication Brain, spinal cord, and nerves Muscle tissue: Contracts to cause movement Muscles attached to bones (skeletal) Muscles of heart (cardiac) Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters Skin surface (epidermis) Lining of GI tract organs and other hollow organs Connective tissue: Supports, protects, binds other tissues together Bones Tendons Fat and other soft padding tissue

Epithelial Tissue (Epithelium) Two main types (by location): 1.Covering and lining epithelia On external and internal surfaces obody (i.e. epidermis) and oventral cavity organs (i.e. visceral serous membranes) 2.Glandular epithelia Secretory tissue in glands o internal spaces (i.e. lumen of the intestine), o line body cavities (i.e. parietal membranes), o line ducts of exocrine glands (i.e. sweat glands). Epithelial Tissue

5 Functions of Epithelial Tissue Protection Absorption Filtration Secretion

1.Cells exibit polarity—apical (upper, free) and basal (lower, attached) surfaces –Apical surfaces may bear microvilli (e.g., brush border of intestinal lining) or cilia (e.g., lining of trachea). –Apical surfaces always have a free space, which opens to the outside or to an internal space (lumen) –Noncellular basal lamina of glycoprotein and collagen lies adjacent to basal surface Characteristics of Epithelial Tissue

2.Cellularity - cells are in close contact with each other with little or no intercellular space between them. 3.Supported by a connective tissue - reticular lamina (under the basal lamina) at the basal surface, both the epithelial tissue and the connective tissue contribute to the basement membrane 4.Avascular (no blood supply). 5.Innervated (supplied with nerves) 6.Rely on diffusion and underlying connective tissue for nutrients and O 2 7.High rate of regeneration Characteristics of Epithelial Tissue

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9 Cellularity - Intercellular Junctions Gap junctions Tubular channels between cells Located in cardiac muscle cells cardiac muscle cells digestive smooth muscle cells Tight junction Cell membrane Desmosome Gap junction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tight junctions Close space between cells Located among cells that form linings lining cells in small intestine kidney tubules blood-brain barrier Desmosomes Form “spot welds” between cells Found in tissues that undergo repeated episodes of tension and stretching skin, heart, uterus

Basement Membrane: The Basal Lamina Noncellular supporting sheet between the epithelium and the connective tissue deep to it Consists of proteins secreted by the epithelial cells Functions: –Acts as a selective filter, determining which molecules from capillaries enter the epithelium –Acts as scaffolding along which regenerating epithelial cells can migrate Basal lamina and reticular layers of the underlying connective tissue form the basement membrane

First name of tissue indicates number of layers –Simple – one layer of cells –Stratified – more than one layer of cells Classifications of Epithelia - Pseudostratified- tissue appears to be stratified, but all cells contact basement membrane so it is in fact simple

Last name of tissue describes shape of cells –Squamous – cells wider than tall (plate or “scale” like) –Cuboidal – cells are as wide as tall, as in cubes - Columnar – cells are taller than they are wide, like columns Classifications of Epithelia

13 Epithelial Tissue Simple squamous: Single layer of flat cells Substances pass easily through Line air sacs Line blood vessels Line lymphatic vessels Simple cuboidal: Single layer of cube-shaped cells Line kidney tubules Cover ovaries Line ducts of some glands (b)(a) Free surface of tissue Simple squamous epithelium Basement Nucleus Connective tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b,d: © Ed Reschke Nucleus Basement membrane Free surface of tissue Simple cuboidal epithelium Connective tissue Lumen (a)(b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer

Simple Squamous Epithelium Figure 4.3a

Simple Cuboidal Epithelium Figure 4.3b

16 Simple columnar: Single layer of elongated cells Nuclei usually near the basement Membrane at same level Sometimes possess cilia Sometimes possess microvilli Often have goblet cells Line uterus, stomach, intestines Pseudostratified columnar: Single layer of elongated cells Nuclei at two or more levels Appear striated Often have cilia Often have goblet cells Line respiratory passageways Nucleus Basement membrane Microvilli (free surface of tissue) Connective tissue Mucus Cytoplasm Goblet cell (a)(b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer. (a)(b) Cilia (free surface of tissue) Goblet cell Basement membrane Nucleus Connective tissue Cytoplasm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Epithelial Tissue

Simple Columnar Epithelium Figure 4.3c

Pseudostratified Ciliated Columnar Epithelium Figure 4.3d

Contain two or more layers of cells Regenerate from below Major role is protection Are named according to the shape of cells at apical layer Stratified Epithelial Tissue

Specific types –Keratinized – contain the protective protein keratin Surface cells are dead and full of keratin –Non-keratinized – forms moist lining of body openings Function –Protects underlying tissues in areas subject to abrasion Location –Keratinized – forms epidermis –Non-keratinized – forms lining of esophagus, mouth, and vagina Stratified Squamous Epithelium

21 Stratified squamous: Many cell layers Top cells are flat Can accumulate keratin Outer layer of skin Line oral cavity, vagina, and anal canal Stratified cuboidal: 2-3 layers Cube-shaped cells Line ducts of mammary glands, sweat glands, salivary glands, and the pancreas Basement membrane Layer of dividing cells Connective tissue Free surface of tissue Squamous cells (b)(a) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer (a)(b) Stratified cuboidal epithelium Free surface of tissue Lumen Basement membrane Connective tissue Nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer. Epithelial Tissue

Stratified Squamous Epithelium Figure 4.3e

Stratified Cuboidal Epithelium Description –generally two layers of cube-shaped cells Function –protection Location –Forms largest ducts of sweat glands –Forms ducts of mammary glands and salivary glands

24 Stratified columnar: Top layer of elongated cells Cube-shaped cells in deeper layers Line part of male urethra and part of pharynx Transitional: Many cell layers Cube-shaped and elongated cells Line urinary bladder, ureters, and part of urethra (b)(a) Lumen Stratified columnar epithelium Connective tissue Basement membrane Free surface of tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer Stretched transitional epithelium Basement membrane Underlying connective tissue Basement membrane Underlying connective tissue Unstretched transitional epithelium (b)(a) (d)(c) Free surface of tissue Free surface of tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b,d: © Ed Reschke Epithelial Tissue

Stratified Columnar Epithelium Description –several layers; basal cells usually cuboidal; superficial cells elongated Function –protection and secretion Location –Rare tissue type –Found in male urethra and vas deferens, largest ducts of salivary glands, nasopharynx

Figure 4.3h Transitional Epithelium

27 Glandular Epithelium A gland is one or more cells that makes and secretes an aqueous fluid Composed of cells that are specialized to produce and secrete substances There are two (2) types: Endocrine glands no contact with exterior of body; ductless; produce hormones (pituitary, thyroid, adrenals, pancreas) Exocrine glands o Exocrine glands classified either by structure or by the method of secretion o Classified by structure

Endocrine Glands Glands that do not have ducts or tubules and whose secretions are distributed throughout the body Produce and secrete hormones into the bloodstream or the lymphatic system Part of a complex, biochemical network known as the endocrine system 28

Exocrine Glandular Epithelium 29 Unicellular exocrine gland: Composed of one cell Goblet cell Multicellular exocrine gland: Composed of many cells Sweat glands, salivary glands, etc. Simple and compound

Unicellular Exocrine Glands (The Goblet Cell) Goblet cells produce mucin Mucin + water  mucus Protects and lubricates many internal body surfaces

Multicellular Exocrine Glands Classified by structure (branching & shape) of duct Classified on the basis of types of ducts or mode of secretion Types of ducts –Simple: ducts with few branches –Compound: ducts with many branches Mode of Secretion –Merocrine secretion – secretory vesicles released via exocytosis (saliviary glands) –Apocrine secretion – apical portion of the cell is lost, cytoplasm + secretory product (mammary glands) –Holocrine secretion – entire cell is destroyed during secretion (sebaceous gland)

May also be classified by types of secretions from exocrine glands Serous –mostly water but also contains some enzymes –Ex. parotid glands, pancreas Mucous –mucus secretions –Ex. sublingual glands, goblet cells Mixes –serous & mucus combined –Ex. submandibular gland

33 Types of Glandular Secretions Merocrine Glands Fluid product Salivary glands Pancreas gland Sweat glands Apocrine Glands Cellular product Portions of cells Mammary glands Ceruminous glands Holocrine Glands Secretory products Whole cells Sebaceous glands (a) Merocrine gland(b) Apocrine gland(c) Holocrine gland Secretion Pinched off portion of cell (secretion) Intact cell Disintegrating cell and its contents (secretion) New cell forming by mitosis and cytokinesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

34 Structural Types of Exocrine Glands Duct Secretory portion Tissue surface Simple tubular Simple branched tubular Simple branched alveolar Simple coiled tubular Compound tubular Compound alveolar Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Exocrine Vs. Endocrine Glands Endocrine Gland Characteristics: –Ductless glands –Secrete substances directly into bloodstream –Produce molecules called hormones Which is Which?