This is a comprehensive and detailed note on Chapter 4;Tissue level of organization
5;The integumentary system 6; Bones and bone structure for Bio 2311.
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Fundamentals of Anatomy & Physiology Study Guide CH 4 – 6
Chapter 4: The Tissue Level of Organization
An Introduction to Tissues
Tissues
o Collections of specialized cells and cell products that perform specific functions
o Tissues in combination form organs, such as the heart or liver
o Histology is the study of tissues
4 – 1 Four Types of Tissues
Four types of tissue
1. Epithelial
2. Connective
3. Muscle
4. Nervous
Epithelial tissue
o Covers exposed surfaces
o Lines internal passageways
o Forms glands
Connective tissue
o Fills internal spaces
o Supports other tissues
o Transport materials
o Stores energy
Muscle tissue
o Specialized for contraction
o Skeletal muscle, heart muscle, and muscular walls of hollow organs
Nervous tissue
o Carries electrical signals from one part of the body to another
4 – 2 Epithelial Tissue
Epithelial tissue includes epithelia and glands
o Epithelia (singular, epithelium)
Layers of cells covering internal or external surfaces
o Glands
Structures that produce fluid secretions
Functions of epithelial tissue
1. Provides physical protection
2. Controls permeability
3. Provide sensation
4. Produce specialized secretions
Characteristics of epithelia
, o Polarity (apical and basal surfaces)
o Cellularity (cell junctions)
o Attachment (basement membrane)
o Avascularity (avascular)
o Regeneration
Specialization of epithelial cells
1. Move fluids over the epithelium (protection)
2. Move fluids through the epithelium (permeability)
3. Produce secretions (protection and messaging)
Polarity
o Apical surface
Microvilli increase absorption or secretion
Cilia on a ciliated epithelium move fluids
o Basolateral surface
Integrity of epithelia is maintained by
1. Intercellular connections
2. Attachment to the basement membrane
3. Epithelial maintenance and repair
Intercellular connections
o Support and communication
Cell adhesion molecules (CAMs)
Transmembrane proteins
Proteoglycans act as intercellular cement
Contain glycosaminoglycans such as hyaluronan (hyaluronic acid)
o Cell junctions
Form bonds with other cells or extracellular material
1. Gap junctions
2. Tight junctions
3. Desmosomes
Gap junctions
o Allows rapid communication
o Cells held together by interlocking transmembrane proteins (connexons)
o Allows small molecules and ions to pass
o Coordinate contractions in heart muscle
Tight junctions
o Between two plasma membranes
o Adhesion belt attaches to terminal web
o Prevent passage of water and solutes
o Keep enzymes, acids, and wastes in the lumen of the digestive tract
Desmosomes
o CAMs and proteoglycans link opposing plasma membranes
o Spot desmosomes
Tie cells together
, Allow bending and twisting
o Hemidesmosomes
Attach cells to the basement membrane
Attachment to the basement membrane
o Basal lamina
Closest to the epithelium
o Reticular lamina
Deeper portion of basement membrane
Provides strength
Epithelial maintenance and repair
o Epithelial cells are replaced by continual division of stem cells
Located near basement membrane
4 – 3 Classification of Epithelia
Classification of epithelia
1. Based on shape
o Squamous – thin and flat
o Cuboidal – square shaped
o Columnar – tall, slender rectangles
2. Based on layers
o Simple epithelium – single layer of cells
o Stratified epithelium – several layers of cells
Squamous epithelia
o Simple squamous epithelia
Absorption and diffusion
Mesothelium
Lines body cavities
Endothelium
Forms inner lining of heart and blood vessels
o Stratified squamous epithelia
Protects against mechanical stresses
Keratin adds strength and water resistance
Cuboidal epithelia
o Simple cuboidal epithelia
Secretion and absorption
Glands and portions of kidney tubules
o Stratified cuboidal epithelia
Relatively rare
Ducts of sweat glands and mammary glands
Transitional epithelia
o Tolerate repeated cycles of stretching without damage
o Appearance changes as stretching occurs
o Found in urinary bladder
, Columnar epithelia
o Simple columnar epithelia
Absorption and secretion
Found in stomach, small intestine, large intestine
o Pseudostratified columnar epithelia
Typically have cilia
Found in nasal cavity, trachea, bronchi
o Stratified columnar epithelia
Relatively rare
Provide protection in pharynx, anus, urethra
Glandular epithelia
o Glands are collection of epithelial cells that produce secretions
o Endocrine glands
Releases hormones that enter bloodstream
No ducts
o Exocrine glands
Produces exocrine secretions
Discharge secretions through ducts onto epithelial surfaces
Gland structure
o Unicellular glands
o Multicellular glands
Unicellular glands
o Goblet cells are unicellular exocrine glands
In epithelia of intestines
Secret mucin, which mixes with water to form mucus
Multicellular exocrine glands are classified by
1. Structure of the duct
o Simple (undivided)
o Compound (divided)
2. Shape of secretory portion of the gland
o Tubular (tube shaped)
o Alveolar or acinar (blind pockets)
3. Relationship between ducts and glandular areas
o Branched (several secretory areas sharing one duct)
Methods of secretion
1. Merocrine
2. Apocrine
3. Holocrine
Merocrine secretion
o Released by secretory vesicles (exocytosis)
o Example: merocrine sweat glands
Apocrine secretion
o Released by shedding cytoplasm
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