Download
1 / 44
440 likes | 645 Vues
Unit 2: Histology. The Tissue Level of Organization. 4-1 The Tissue Level of Organization. 1. Definitions : a. Tissues – collections of specialized cells and cell products that perform a limited number of functions b. Histology – the study of tissues.
E N D
Unit 2: Histology The Tissue Level of Organization
4-1 The Tissue Level of Organization 1. Definitions: a. Tissues – collections of specialized cells and cell products that perform a limited number of functions b. Histology – the study of tissues
4.1 – The body’s four basic tissue types • Epithelium – covering • Connective – support • Muscle – movement • Nervous - control Some organs may be composed primarily of one type of tissue, but usually all four types are found All 4 tissue types have a variety of sub-types with a unique set of characteristics & functions
4.2 – Epithelial Tissue Epithelial tissue includes: 1. Epithelia – layers of cells that cover internal and external surfaces 2. Glands – composed of secreting cells derived from epithelia
4.2 – Epithelial Tissue Characteristics APPEARANCES: - Cells fit closely together & are usually irregular in shape -A free (apical surface) exposed to the environment or to some internal chamber or passageway. - apical surface may have specialized projections such as cilia (hair-like structures) or microvilli (increase surface area for absorption) - Attached to underlying tissue by a basement membrane (protein fibers that connect epithelium to underlying connective tissue). - Avascular (absence of blood vessels) – obtain nutrients from deeper tissues - Continual regenerationof epithelial cells lost from the surface (stem cells or germinative cells found deep near the basement membrane
4.2 – Epithelial Tissue Characteristics LOCATIONS: - line inner surface of passageways through organs - cover outer surfaces - make up glandular tissue
4.2 – Epithelial Tissue Characteristics FUNCTIONS: - Physical protection - Controls permeability - Provide sensation - Produce secretions(gland cells – cells that produce secretions, glandular epithelium – most or all cells produce secretions) 1. Exocrines– secretions are discharged onto the surface of the epithelium (digestive enzymes, perspiration, milk) 2. Endocrine – secretions are released into the surrounding tissue (hormones)
4-3. Classification of Epithelia. 1. Cell Layers - Simple – single layer of cells (found in protected areas of the body) - Stratified – several layers of cells (found in areas of heavy mechanical or chemical stress)
4-3. Classification of Epithelia. 2. Cell Shapes - Squamous – thin and flat - Cuboidal – cube- shaped, usually form neat rows - Columnar - rectangular
4-4. Connective Tissue Connective Tissues Include: 1. Specialized cells 2. Protein fibers* - collagen – (white) fiber that has a high tensile strength, the most common type - elastic – (yellow) fiber that is very flexible - reticular – fine collagen fiber that forms the internal “skeleton” of soft organs such as the spleen 3. Ground substance* - extracellular fluid composed of water, adhesion proteins & polysaccharides 1. protein fibers and ground substance make up the matrix that surrounds the cells 2. Whereas epithelial tissue consists almost entirely of cells, the extracellular matrix accounts for most the volume of connective tissues.
4-4. Connective Tissue Characteristics APPEARANCE: - CT has fewer cells than epithelial tissue with space between cells - the matrix between cells is produced by CT cells and secreted outside the cells - the matrix is unique to CT
4-4. Connective Tissue Characteristics Functions: - Support and protection (bone, ligaments, tendons) - Transportation of materials (blood) - Storage of energy reserves (adipose/fat) - Defense of body (specialized cells)
. c. Three major types of connective tissues
4-4 Supportive Connective Tissue - Cartilage CARTILAGE INCLUDES: - cells called chondrocytes - intercellular matrix - as cells secrete the intercellular matrix, they become trapped in spaces known as lacunae APPEARANCE: - has no blood vessels passing through, the cells exchange materials through diffusion - all cartilage is covered by an outer sheath of dense CT called the perichondrium, except on surfaces of joint cavities
4-4 Supportive Connective Tissue - Cartilage LOCATION: - a highly specialized CT most commonly found in the skeletal system, but is also found in other places of the body FUNCTION: - firm, tough and flexible
4-6 Muscle Tissue MUSCLE TISSUE CONTAINS: - specialized muscle fibers with myosin and actin filaments LOCATION: - muscles FUNCTION: - specially designed to contract (contractility = elasticity) - responsible for ALL movement by the human body
4-8 Response to Tissue Injury Any injury affects several tissue types simultaneously, and they respond in a coordinated manner. Homeostasis is restored through two processes: 1. Inflammation (inflammatory response) – isolates the injured area while damaged cells, tissue components, and any dangerous microorganisms are cleaned up (will cover in more detail in Chap. 14) 2. Regeneration - the repair process that restores normal function 1. Fibroblasts produce a dense network of collagen fibers – scar tissue
4-9 Effects of Age EFFECTS OF AGING ON TISSUE - decreasing ability to repair damage - repair mechanisms slow down - less energy - cumulative damage over many years - epithelial thins, CT becomes more fragile, cardiac muscle and neurons can’t be replaced - increase in occurrence of cancer
