Chapter 4: Tissues

• Covering and Lining Epithelium
• Glandular Epithelium

• Protection (skin)
• Absorption (digestive tract)
• Filtration (kidneys)
• Sensory (chemical detection on tongue)
• Secretion (hormones, saliva)

• Polarity (apical and basal surface)
• Specialized Contacts (held together by tight junctions and/or desmosomes)
• Supported by connective tissue (basal and reticular lamina)
• Avascular (no blood vessels) but innervated (supplied by nerve fibers)
• Regenerative (able to reproduce)

• Basement membrane: provides point of attached end mechanical support
• Basal lamina: selective filter made up of epithelial tissue
• Reticular lamina: deeper "cushion" made of connective tissue

• Tight Junctions—pushes back passage of substances; prevents seepage in cavity (stomach, intestines, urinary bladder)
• Desmosomes —"clamp";prevent separation under tension (outer layer of skin)
• Gap Junctions—allow cell to cell communication (nerve and muscle tissue)

Cell shape and number of layers

Covers of ventral body cavity and covers the organs within the cavity

• Endothelium: lines inside of heart, blood vessels, and lymph nodes
• Mesothelium: serous membranes that line the body cavity and covers organs

Diffusion and filtration; found in air sacs, lining of ventral cavity body, lining of heart, blood vessels, and lymph nodes.

Protection; keratinized—epidermis of skin, nonkeratinized—esophagus, mouth, vagina

A single cell or a group of cells that make and secrete substances into ducts, onto a surface, or into the blood

• Where their products is released
• Relative cell number

• Exocrine: glands that secrete products onto body surfaces or into body cavities
• Endocrine: "ductless" glands that secrete hormones into blood

• Endocrine—thyroid glands, adrenal glands
• Exocrine—mucous, sweat/oil glands, salivary glands, pancreas/liver

Mucous and goblet cells

Secretes mucin that will become mucus; found in trachea (pseudostratified columnar epithelium)

• Merocrine—secrete products by exotysis
• Holocrine—accumulate products until cell ruptures

• Merocrine—pancreas, sweat, and salivary glands
• Holocrine—sebaceous or oil glands of skin

• Exocytosis: process where cell releases materials to the outside through membrane-bounded vesicles passing through the cell membrane.
• V(vesicle)-SNAREs and T(target)-SNAREs are signaling molecules that fuse to the vesicle.

• Connective tissue proper—fibroblasts
• Cartilage—chondroblasts
• Bone—osteoblasts
• Blood—red and white blood cells

• Embryonic origin (mesenchyme)
• Various degrees of vascularity (avascular and vascular)
• Composed of "living" cells and a "non-living" extracellular matrix

Mesenchyme

• Immature (—blast) cells—active, fast mitosis; secrete extracellular matrix
• Mature (—cyte) cells—less active, slow mitosis; maintain health of extracellular matrix; carry out specialized function

• Ground substance: unstructured, fills space between cells (interstitial, or extracellular, fluid; cell adhesion proteins, proteoglycans)
• Fibers (collagen, elastic, reticular)

• Loose connective tissue
• 1. Areolar
• 2. Adipose
• 3. Reticular
• Dense connective tissue
• 1. Dense, Regular
• 2. Dense, Irregular
• 3. Elastic

• Structure: Gel like matrix with collagen, elastic, and reticular fibers (loose arrangement); fibroblasts, macrophages, mast cells, and some white blood cells
• Functions: Wraps and cushions organs, plays important role in inflammation, holds and conveys tissue fluid, serves as general packing material
• Found in lamina propria of mucous membranes and supports and surrounds capillaries

Connective tissue supporting mucous membranes (line body cavities open to outside of body)

Fluid retention in areolar tissue; role in inflammation

• Structure: little matrix; closely packed fat cells, or adipocytes (store triglycerides); vascularized for high metabolic activity; accumulates in subcutaneous tissue
• Functions: protection; insulation; fuel storage; supports and protects organs
• Found in yellow bone marrow; under skin; surrounding kidneys and eyeballs; within abdomen; in breasts

• Structure:parallel strands of thick collagen fibers; few cells (major cell—fibroblast); very little ground substance; poorly vascularized; 
• Functions: high tensile strength when pulling force in one direction; attaches bones to bones; attaches muscles to bones or muscles
• Found in tendons and ligaments

• Structure: irregularly arranged collagen fibers; few cells; very little ground substance; poorly vascularized
• Functions:high tensile strength when pulling force is in many directions
• Found in dermis; fibrous capsules of organs and joints

• Intradermal: administered into dermis; longest absorption time (tuberculosis tests)
• Subcutaneous: administered into adipose tissue layer below epidermis and dermis; slow sustained rate of drug absorption into blood (insulin)
• Intramuscular: administered through skin and subcutaneous tissue and into the underlying muscle; faster rate of absorption and onset of action (hormones, antibiotics, vaccines)

• Hyaline
• Elastic
• Reticular

• Structure: amorphous but firm matrix (pits within matrix); most abundant (yet weakest) cartilage
• Function: provides flexibility and support; reduces friction and absorbs shock
• Found in nose, trachea, larynx, covering long end of bones

• Structure: strongest cartilage in body; matrix similar but less firm than hyaline
• Function: provides strong support and withstands heavy pressure (high tensile strength)
• Found in intervertebral discs

• Structure:similar to hyaline but more elastic fibers in matrix
• Function: maintains the shape of a structure while allowing great flexibility
• Found in external ear

• Structure: additional collagen fibers and calcium salts found in hard calcified matrix
• Function: support and protect body structures; resists compression and tension

• Structure: red and white blood cells in a fluid matrix (plasma)
• Function: transport respiratory gases, nutrients, wastes, and other substances

• Structure: Long, cylindrical, multinucleate cells; striations 
• Function: voluntary movement/control; locomotion; manipulation of the environment; facial expressions

• Structure: contains neurons (generate nerve impulses) and supporting cells (do not generate nerve impulses)
• Function: supports, insulates, and protects neurons

• Skeletal—muscles attached to bones 
• Cardiac—muscles of heart 
• Smooth—muscles of walls of hollow organs (stomach)

• Dry membrane
• Keratinized, stratified squamous epithelium (epidermis); thick layer of dense irregular tissue (dermis)
• Found in skin

• Lines the closed ventral cavities; wet or moist membranes
• Non-keratinized stratified squamous or simple columnar; epithelia on top of loose connective tissue (lamina propria) and rests on top of smooth muscle
• Found in nasal cavity, mouth, esophagus lining, bronchi in lungs

• Lines the closed ventral cavities; wet or moist membranes
• Simple squamous epithelium (mesothelium) on top of layer of loose areolar connective tissue
• Found in heart, lungs, abdomen

• Pleurae—membrane that lines lungs
• Pericardium—membrane that lines heart
• Peritoneum—membrane that lines abdomen

• High regenerative capacity—Epithelia, areolar connective tissue, dense irregular connective tissue, bones, blood
• Moderate regenerative capacity—Dense regular connective tissue, smooth muscle
• Weak regenerative capacity—Cartilage, skeletal muscle
• Little or no regenerative capacity—Cardiac muscle, nervous tissue