Ch. 4.1 - 4.3: Tissue Level Of Organization Flashcards
What are the important characteristics of epithelial tissue?
Cellularity, polarity, attachment, avascularity, regeneration
What are the 4 basic tissue types?
- Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Neural tissue
Tissues
Collections of specialized cells and cell products that perform a limited number of functions
Epithelial tissue
Covers exposed surfaces, lines internal passageways and chambers, and forms glands
Connective Tissue
- Structural framework for body 2. Transporting fluids and dissolved materials 3. Protects delicate organs 4. Supporting, surrounding, interconnecting other tissues 4. Stores energy reserves 5. Defense
Muscle tissue
Specialized for contraction, includes skeletal muscles, heart muscle, muscular walls of hollow organs
Neural Tissue
Carries information from one part of the body to the other via electrical impulses
Two types if epithelial tissue
Epithelial and glands
Four functions of epithelial tissue
- Physical protection 2. Controls permeability 3. Provides sensation 4. Produce specialized secretions
What three factors maintain integrity of the epithelia?
- Intercellular connections 2. Attachment to basement membrane 3. Regeneration - maintenance and repair
Cell adhesion molecules (CAM)
Transmembrane proteins that bind to each other and to extra cellular material
Hyaluronan, Hyaluronic acid;
An important component of the thin layer of proteogylcans that binds the membranes of adjacent cells
Cell Junctions (3)
Areas of the plasma membrane that attach a cell to another cell or extracellular material. 1. Tight junction 2. Gap junctions 3. Desmosomes
Tight Junction
- Interlocking membrane proteins bind the lipid portions of two plasma membranes. 2. A continuous adhesion belt forms a band inferior to the tight junction, which encircles the cells and binds to neighbors. Bands are attached to microfilaments of the terminal web. 3. TJs prevent prevent passage of water and solutes; isolate lumen from basolateral surfaces
Gap Junction
- Two cells held together by CONNEXONS, interlocking transmembrane proteins. These are channel proteins that form small passageways to transport small molecules/ions. 2. Needed where when tissue activity is coordinated: i.e. beating cilia or heart contractions.
Desmosomes
- Durable interconnections that provide resistance to mechanical stress. 2. CAMs and proteogylcans link opposing plasma membranes 3. Occurs at the ‘dense area’ of cell complex that is connected to the cytoskeleton
Two types of desmosomes
- Spot desmosomes: small discs connected to bands of intermediate filaments. Stabilize the shape of the cell 2. Hemidesmosomes: attaches cell to extracellular filaments in basal membrane. Stabilizes and anchors the position of the cell
Mesothelium
Simple squamous epithelium that lines the ventral body cavities
Endothelium
Simple squamous epithelium that lines inner surface of the heart and all blood vessels
Endocrine glands
Ductless glands. Release their secretions (“hormones”) into the interstitial fluid. Ex: pituitary gland and thyroid
Gland
Collection of epithelial cells that produce secretions
Exocrine Gland
Produce secretions discharged onto the epithelial surface. Most reach surface through tubular ducts Ex: enzymes entering the digestive tract, perspiration on skin, tears in eyes, milk from mammary glands
Modes of exocrine secretion (3)
- Merocrine 2 Apocrine 3. Holocrine
Merocrine Secretion
Released from secretory vesicles by exocytosis. The most common mode of secretion.
Mucin
A type of merocrine secretion that mixes with water to form mucus
Apocrine secretion
Involves the loss of cytoplasm as well as secretory product.
Holocrine secretion
Destroys the gland cell. Entire cell is packed with secretory particles then bursts. Ex: sebaceous gland
Types of secretions (3)
- Serous glands 2. Mucous glands 3. Mixed exocrine glands
Serous glands
Secrete a water solution that contains enzymes Ex: parotid salivary glands
Mucous glands
Secrete mucins that hydrate to form mucus
Mixed Exocrine Glands
Contain more than one type of gland cell and may produce two different exocrine secretions, one serous and mucous. Ex: submandibular salivary glands
Three ways to characterize exocrine glands
- Mode of secretion 2. Type of secretion 3. Gland structure
Unicellular exocrine glands
Mucous (goblet) cells. Located among paeudostratified ciliated columnar epithelia in trachea; columnar epithelia of stomach/intestines
How are multicellular exocrine glands characterized?
- Structure of the duct 2. Shape of the secretory portion of the gland 3. Relationship between ducts and glandular areas (i.e. branched)
Tubular
Glands whose ducts form tubes; can be straight or coiled
Alveolar (acinar) ducts
Glands whose glandular cells form pockets
Simple gland structures (5)
- Simple tubular 2. Simple coils tubular 3. Simple branched tubular 4. Simple alveolar (acinar) 5. Simple branched alveolar
Compound glands
- Compound tubular 2. Compound alveolar (acinar) 3. Compound tubuloaveolar