Tissues

Tissue Types Four Major Classifications –Epithelial –Connective –Muscle –Nervous

“Living Fabric” Epithelial Tissue –Surface Coverage Forms a boundary between environments –Where might we find this type of tissue?

Special Characteristics Cellularity –Composed of tightly packed cells Specialized Contacts –Fit closely to form continuous sheets How are these cells held together? Polarity –Apical Surface (Exposed to Environment) –Basal Surface (Attachment Point)

Apical and Basal Surfaces Most apical surfaces exhibit microvilla –What benefit do microvilla provide? –Cilla are also present in many cases… What do tissues use these for? Basal Lamina –Adhesive Sheet –Selective Filtering –Scaffolding for Wound Repair

Special Characteristics Continued… Supported by connective tissue Innervated and Avascular –Contain nerves but no blood vessels How are they nourished? Regeneration –Constantly lost and replaced Where might this be very common in the human body?

Types of Epithelia Simple Stratified Simple Cuboidal Simple Columnar Pseudostratified Columnar

Simple Epithelia Squamous –Flattened –Resemble a tile floor –Low in cytoplasm –Permeable Where might a flat, permeable surface be useful in body organs?

Simple Cuboidal Secretion and Absorption

Simple Columnar Dense Microvilli –Absorption and Secretion Goblet Cells –“Cups” of mucus Protective barrier Where would this type of tissue be useful?

Pseudostratified Columnar Heavily Ciliated Lots of Goblet Cells –Where might these two characterstics be useful?

Stratified Epithelium Stratified Squamous –Skin Stratified Cuboidal –Rare Found in lining of male urinary tract Transitional –Capable of stretching and recovering –Capable of holding pressurized liquids –Where are these found?

Connective Tissue Unique Characteristics –Common origin Arise from mesenchyme –Embryonic Tissue – Mesoderm Layer Low vascularity Extracellular matrix –Nonliving structural material that bonds connective cells

Three main elements of Connective Tissue 1. Ground Substance –Unstructured material that contains the fibers –Composed of: Interstitial Fluid – Nutrient Distribution Cell Adhesion Proteins (Glue) Proteoglycans – Intertwine and trap water

Fibers Collagen Fibers –Provide Tensile Strength Elastic Fibers –Provide Ability to Stretch Reticular Fibers –Support soft tissues of organs

Loose Connective Tissues Areolar –Predominately Fibroblasts Where have we seen these before? –“Packing Material” between other tissues Adipose –Fat Nutrient Storage –What does a fat cell look like? –Special prize to someone who can draw one…

Loose Connective Cont. Reticular Tissue (Do not confuse with reticular fibers) –Internal framework for storing free blood cells –Lymph Nodes, Bone Marrow, Spleen

Dense Regular Connective Tissue Predominantly composed of fibers Fibers aligned in direction of pulling force Tendons – Muscle to Bone Ligaments – Bone to Bone

Dense Irregular Connective Tissue It’s all about the direction of pull Collageneous, thicker than tendons Forms sheets that are strong in every direction Where might we find this type of tissue?

Cartilage Intermediate between dense connective and bone Strong but flexible –Hyaline Carilage Most abundant – “Gristle” –Nose –Trachea –Embryonic Skeleton

Elastic Cartilage Similar to Hyaline –External Ear –Epiglottis

Fibrocartilage Cushions between vertebral discs Soft tissue of knees

Bone Tissue Synonomous with “Osseous Tissue” Rocklike Hardness –Supports and protects softer tissues Osteoblasts produce organic part of bone Calcium salts are then deposited on and between osteoblasts for form what we know as bone Osteocytes – Mature Bone Cells imbedded in matrix

Blood Non-living plasma “Suspension” Fiber-like protein molecules clump together to form platelets which lead to clotting lead to clotting Red and white blood cells have unique functions –What’s the difference? Distributes nutrients to cells and removes wastes - VideoVideo

Nervous Tissue Makes up the nervous system –Brain, spinal cord, nerves Two major cell types –Neurons Generate and Conduct impulses –Supporting Cells Nonconductive cells that support, insulate, and protect delicate neurons

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Muscle Tissue Highly Cellular Highly Vasculated Myofilaments - Electric Impulses cause them to contract, causing movement Skeletal Muscle –Attached to bones –Long, cylindrical cells

Cardiac Muscle Solely in the walls of the heart Contractions pump blood though body Video

Smooth Muscle Primarily found in walls and linings of hollow organs

Muscles Concluded… Voluntary vs. Involuntary