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Chapter 4: The Tissue Level of Organization (4-2 Epithelial Tissue…
Chapter 4: The Tissue Level of Organization
4-2 Epithelial Tissue
Functions
Produce specialized secretions- cells that produce secretions are called gland cells.
Exocrine-produce mucus and secretions discharged onto surface of epithelium.
ex.) enzymes entering digestive tract, perspiration on skin, milk produced by mammary glands.
Endocrine- secretions are released into the surrounding tissue and blood stream. These are called hormones, act as chemical messengers and regulate or coordinate tissues, organs, or organ systems. ex.) pancreas, thyroid, and pituitary gland
merocrine-produce and release, no loss of gladular cells (ie. salivary glands)
apocrine- some cells will be lost (ie.mammary glands)
holocrine-cell goes with it (ie. sebacous glands)
Control permeability-any substance that enters or leaves body must cross epithelium
Provide physical protection- protect exposed and internal surfaces from abrasion, dehydration, and destruction ( ie. epidermis)
Provide sensation- specialized cells can detect change in environment and relay information about the changes to nervous system (ie. pressure receptors)
filtration- (ie. kidney capillaries)
absorption- (ie. lining of intestine)
Types
Epithelia
Layers of cells that cover internal ad external surfaces
Gland-
Composed of secreting cells derived from epithelia
Epithelial Characteristics
basement membrane- basal surface ; anchored to underlying CT
avascularity- contain no blood cells, they are nourished by underlying connective tissue through basement membrane
Free surface- apical surface which opens to outside or to internal space (may have cilia (aid in movement) or microvilli (increase membrane surface)
regeneration- rapid cell division and high regeneration (stem cells)
Bound closely
Intercellular Connections
desmosomes- hold adjacent cells, and layer of cells together
tight junctions- zipper-like to prevent intercellular leakage
gap junctions- intercellular communication
4-1 Identify the bodies 4 basic types of tissues and their roles.
Muscle Tissue
Contracts to produce active movement
Neural Tissue
Conducts electrical impulses
Carries Information
Connective Tissue
Fill internal spaces
Provide structural support
Store energy
Epithelia
Line internal passageways and chambers
Produces glandular secrections
Cover exposed surfaces
4-3 Cell shape and Number of layers
Cell Layers
Simple epithelium
Single layer of cells covering the basement membrane. ( Line ventral body cavities, heart chambers, and blood vessels)
Stratified epithelium
Several layers of cells; provides greater protection. (Found in areas subject to mechanical or chemical stress; surface of skin + lining of mouth)
Cell Shapes
Cuboidal- resemble boxes, nuclei lie near center of each cell
Squamous- cells are thin and flat, nucleus occupies center portion of cell (yolk in fried egg), cells look like fried eggs when laid side by side
Columnar- shaped as columns, tall and slender, nuclei are crowded into narrow band , close to the basement membrane
Classification of Epithelia
Simple Cuboidal Epithelia
Provides limited protection and occurs where secretion or absorption takes place.( central nuclei) (ie. kidney tubules)
Simple Columnar Epithelia
Combines squamous and cuboidal to form something that does both (found in lining of stomach) (nuclei located at the bottom) (ie. small intestines)
modifications- microvilli and goblet cells( protective mucus)
Simple Squamous Epithelia
found in protected regions where absorption takes place or slippery surface reduces friction, allows for easy passage/diffusion (lining of ventral body cavities) (ie. air sacs of lungs or Alveoli) (ie.2- blood vessels)
Stratified Squamous Epithelia
found where mechanical stresses are severe ( mouth + anus)
transitional- many layers that change shape ( stretches) (ie. urinary bladder)
stratified cuboidal- (ie. sweat, mammary, salivary glands)
pseudostratified columnar epithelia- functions are secretions and protections- scattered nuclei (ie. trachea)
mods- cilia and goblet
stratified squamous- protection ( non keratinized- lining mouth, vagina,throat,vagina, anus) (keratinized- epidermis of skin)
stratified columnar- 2-3 layers of elongated cells
Surrounding all body cells is extracellular fluid
transport
plasma- liquid portion of blood
lymph- in lymphatic vessels
interstitial- fills space between cells in tissue
transcellular- cerebrospinal fluid , synovial fluid, humors of the eyes, serous and exocrine secretions
site of chemical reactions
medium to dissolve solutes
4-4 Connective tissue (ex. bone, blood, fat)
Connective tissue functions
Transport Materials-Fluid connective tissue provide efficient means of moving dissolved materials from one body region to another
Storage of Energy Reserves- Fats are stored in connective tissue cells called adipose cells, until needed
Support and Protect- minerals and fibers establish a bony structural framework for the body, protects delicate organs, and surround and connect other tissue types
Defends Body- Specialized connective tissue cells respond to invasions by microorganisms through cell- to - cell interaction and the production of antibodies
Classifying Connective Tissues
Connective Tissue proper- many types of cells and fibers within a matrix containing a syrupy ground substance . (ie. tendons and ligaments)
Major Cell Types
Macrophages- scattered through matrix, "big eater"; engulfs, or phagocytizes, damaged cells or pathogens that enter the tissue; also release chemicals that mobilize immune system, attrating additional macrophages to provide tissue defense
Fixed Macrophages- spend long periods of time in connective tissues
Free Macrophages- migrating cells that are drawn to affected area
Fat Cells ( Adipose Cells)- permanent residents, typically contains such a large droplet of lipid that the nucleus and other organelles are pushed to the side of the cell. Number of fat cells varies from one connective tissue to another.
Fibroblasts- most abundant cells in connective tissue proper. Permanent; responsible for producing connective tissue fibers and ground substance.
Mast Cells-Small, mobile cells, often found near blood vessels.Cytoplasm of a mast cell is packed with vesicles filled with chemicals that are released to begin the body's defensive activities after injury/infection
Fibrocytes- following after fibroblasts as the second most abundant; maintain the connective tissue fibers of connective tissue proper
Reticular- loose ground substance; used for support and located in basement membranes and lymphatic organs ( thymus + spleen)
Areolar- covering organs and beneath epithelium, cushions organs and diffusion
Connective Tissue Fibers-
Reticular Fibers- least common of the three, thinner than collagen fibers and commonly form a branching/ interwoven framework in various organs
Elastic Fibers- contain protein "elastin", brached and wavy and return to original size after stretching
Collagen- long, straight, and unbranched. strong but flexible are the most common in connective tissue
Types of Connective Tissue Proper
Loose Connective Tissue( areolar tissue)- contains all of the cells and fibers found in connective tissue proper, extensive blood supply. Form a layer that separates skin from underlying muscle, providing both padding and independent movement
Dense Connective Tissue- consist mostly of collagen fibers,parrallel to each other and aligned with the forces applied to the tissues (ie. tendons & ligaments)
Fluid Connective Tissues- cells suspended in a matrix of watery ground substance containing dissolved proteins (ie. blood and lymph)
Plasma-In blood, watery matrix
White Blood cell- contains important components of the immune system
Red blood cell-Accounts for almost half the volume of blood, transport oxygen.
Platelets- cell fragments that aid in blood clotting
Blood and Lymph-contain distinctive collections of cells in a fluid matrix
Supporting Connective Tissues- less diverse cell population than proper, a matrix of dense ground substance and closely packed fibers.(ie. cartilage and bone) Bone is said to be calcified because it contains mineral deposits
Cartilage- firm gel containing embedded fibers, gain nutrients and eliminate waste with diffusion, surrounded by perichondrium (contains inner cellular layer and an outer fibrous layer), chondrocytes ( cells within the matrix)
Elastic cartilage- extremely resilient and flexible , forms external flap of outer ear, the epiglottis, and the airway to the middle ear
Fibrous cartilage- less firm than elastic; functions for strength and shock absorption, located in inter vertebral discs, and pubic symphysis
Hyaline cartilage- most common; matrix contains closely packed collagen fibers,tough but somewhat flexible. Connects ribs to sternum, supports conducting passageways of respiratory tract, covers opposing bone surfaces within joints
Bone-hard calcified matrix containing osteocytes, located in bone and used for protection and support, calcium store, and hematopoiesis
Three basic components of all connective tissues
Protein FIbers
Ground Substance fluid
Specialized Cells
4-5 Muscle Tissues
Types
Cardiac Muscle Tissue
Pumps blood from heart to lungs and body, involuntary
Smooth Muscle Tissue
movement of food through digestive tract (ie. hollow visceral organs, blood vessels, and hair follicles in dermis)
Skeletal Muscle Tissue
attached to bones, moves bones of skeleton
Characteristics
Muscle fibers are contractile ( they change their shape [shorten] which causes attachments to move)
Cells are elongated ( muscle fibers)