Basic Tissue Types Flashcards
Tissues
Aggregates or groups of cells organized to perform one or more specific functions. The cells within a tissue work collaboratively, forming functional units.
4 basic tissues
Epithelial tissue
Connective Tissue
Muscular tissue
Nervous tissue
Epithelial tissue functions
- Protection: by forming a barrier between the external environment and underlying connective tissue
- Absorption
- Secretion
Characteristics of epithelial cells
- Closely apposed and adhere by specialized cell junctions.
- Exhibit polarity (3 distinct domains: apical, lateral, basal)
- Lowermost cells are always attached by basal surface to an underlying basement membrane.
Classification of epithelia
- The number of layers of cells
2. The shape of the surface cells
Number of layers
simple= one cell layer thick stratified= more than one layer of cells pseudostratified = looks stratified, but all cells rest on the basement membrane (not all cells reach the free surface)
Shape of the cells on the surface layer
Squamous= falt Cuboidal= width, depth, and height are approximately equal Columnar= height of the cell exceeds its width
Apical domain modifications
Microvilli
Cilia
Stereocilia
Primary Cilium
Microvilli
Small finger-like cytoplasmic projections of the luminal plasma membrane that increase the surface area of the cell.
Internal structure consists of actin filaments cross-linked by actin-bundling proteins which confer rigidity.
Cilia
Motile hair-like extensions of the apical plasma membrane with a microtubule-based internal structure (axoneme) associated with motor proteins. Capable of moving fluid and particles along epithelial surfaces.
-Longer than microvilli
Primary Cilia
Solitary projections that are found on almost all eukaryotic cells (not just epithelial).
immotile due to microtubule arrangement and lacking of motor proteins
Function:
- Signal detectors: sense chemical, osmotic, and mechanical stimuli from outer environment.
Sterocilia
Unusually long, immotile microvilli that are located on the sensory cells of the inner ear and parts of male repro tract
Epithelial tissues organized in 2 ways
- Sheets: cells cover or line a free surface
2. Glands
In certain locations, epithelium is given a specific name:
Endothelium= the epithelial lining of blood and lymphatic vessels, simple squamous
Endocardium= the epithelial lining of the heart, simple squamous
Mesothelium= the epithelium lining of closed cavities of the body, simple squamous
Transitional epithelium= the epithelium lining the lower urinary tract, stratified with special characteristics that allow for distention
Connective Tissue function
Forms a continuous compartment through the animal body. It provides structural and functional support for the other 3 tissue types
Connective Tissue Types
- Embryonic Connective tissue (mesenchyme)
- Specialized connective tissue: bone, cartilage, adipose, hematopoietic tissue, blood
- Connective tissue “proper”
Connective tissue (Looks?)
-Composed of cells suspended within a tissue- specific extracellular matrix composed of protein fibers suspended in a watery gel
Characteristics of connective tissue
- Connective tissue cells are not connected to each other.
2. The spaces between cells are occupied by extracellular matrix.
Extracellular matrix
Consists of protein fibers and an amorphous component (ground substance)
2 basic forms:
1. Interstitial matrix
2. Basement membrane
Interstitial matrix
Present between cells (Within connective tissue or between an epithelium and vascular/smooth muscle structures)
Synthesized by fibroblasts
Basement membrane
Highly organized form of extracellular matrix which underlies all epithelial tissue. Synthesized by both overlying epithelial cells and cells in underlying connective tissue
Extracellular Matrix
- Provides structural, biochemical, and mechanical support for connective tissue.
- Provides pathways for cell migration, and allows for diffusion of small molecules
- Lies between the connective tissue cells consisting of fibers dispersed in a viscous clear watery gel called ground substance.
Connective tissue cells
-Fibroblasts are principle cell type
Other cells include:
1. Resident cell population
2. Wandering cell population
Resident cell population
Exhibit little movement
-fibroblasts, myofibroblasts, macrophages, adipocytes, mast cells, adult stem cells
Wander cell population
Consists of cells that have migrated into the tissue from the blood in response to specific stimuli
-Lymphocytes, plasma cells, neutrophils, eosinophils, basophils, monocytes
Fibroblasts
- Principal cell of connective tissue
- Most important cells of connective tissue because they synthesize the extracellular matrix
Myofibroblasts
Display properties of fibroblasts and smooth muscle cells. Elongated and spindly with contractile proteins.
-do not have external lamina and usually exists as isolated cells
3 principal fiber types in connective tissue
- Collagen fibers
- Elastic fibers
- Reticular fibers