Four Basic Tissues - Epithelium and Muscle PDF

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Summary

- Cells are the functional unit of all living tissues. - Tissues, a collection of similar cells (muscle). - Organs, a combination of two or more tissues (heart, spleen). - Body System, collections of organs that work together to perform a common function (nervous system, digestive system).Visualizin...

Description

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Cells are the functional unit of all living tissues. Tissues, a collection of similar cells (muscle). Organs, a combination of two or more tissues (heart, spleen). Body System, collections of organs that work together to perform a common function (nervous system, digestive system).

Visualizing Cells -

Some cell structures can be viewed using light microscopy. With an H and E stain you can see nuclear proteins and basophilic granules. Hematoxylin stains nuclear detail and eosin stains the cytoplasm, collagen and RBCs.

Four Basic Tissues -

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Epithelium, includes the skin and serves as coverings, linings and makes up glandular tissues. Classified by its arrangement and morphology. Also protects organs and absorbs/secretes/excretes substances. Connective, serves in support and connections of structures. Classified by its components and proportions. Also serve to transport materials (blood) and store energy (adipose tissues). Muscle, functions to allow movement. Classified by its morphology and arrangement. Seen as skeletal, cardiac and smooth muscle. Nervous, functions to transmit electrical impulses. Classified by its location, morphology, and function. Controls the bodies activities and response to stimulus.

Epithelium -

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This tissue is composed entirely of cells without fibres and have little intercellular substances. Cells are packed closely together and tightly bound by junctional complexes. Have regular shape and arrangement. Avascular, epithelium tissue contains no blood vessels. All nutrients and oxygen must diffuse from the underlying tissue since it has no blood flow. Epithelium is associated with a basement membrane. The membrane is responsible for attachment and nutrient diffusion. Epithelium also exhibits polarity on the apical and basal surfaces. It means that the cells look different than they do at the top. Apical surfaces are at the top that face the outer body. Basal surfaces are at the bottom of the cell and face toward the inner body. Attachment means the basal surfaces of the cells are attached to the basal membrane (basal lamina). The basal lamina anchors the cells and itself to the connective tissue. Every epithelial tissue can repair and regenerate itself better than any other tissue. This is helpful because the epithelial tissues, like the skin, is frequently scratched and torn. Protection occurs through many layers of epithelium allowing for high impermeability.

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The epithelium in the intestines however are highly permeable for water and nutrients, while still keeping bacteria from passing through it. Epithelium are classified by their layers. o Stratified, tissue is composed of multiple layers of epithelial cells. o Simple, tissue is composed of one layer of epithelial cells. o Pseudostratified, tissue is composed of one layer of epithelial cells, but appears to have multiple layers since not all cells reach the surface. Epithelium are also classified by their cell shape o Squamous, flattened cells that look like fried eggs. o Cuboidal, cube shaped cells. o Columnar, rectangular shaped cells that are taller on one side.

Simple Tissue -

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Simple Squamous, one layer of flattened cells. Located on the endothelium lining (blood vessels), mesothelium of body cavities and the glomerulus. Function in filtration, diffusion and osmosis. Simple Cuboidal, single layer of cube shaped cells. The nucleus is commonly in the centre of the cube. Located in kidney tubule lining, ovary surfaces, excretory ducts, and the secretory portions of glands. Microvilli may be present depending on the location. Simple Columnar, single layer of column shaped cells. The nuclei are elongated along the long side of the cell. Located in the digestive tract, large excretory glands, and the gall bladder. Functions in secretion and absorption. Pseudostratified Columnar, a variation of simple columnar. Nuclei are found at various levels of the cell, causing them to look stratified when they are not. Resemble wine goblets and are called goblet cells. Located in the respiratory tract where they have cilia and in the male reproductive tract where they do not have cilia.

Stratified Tissue -

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Stratified Squamous, have two types, those with keratin (skin) and those without keratin (oral cavity, esophagus, anus, vagina). Functions mainly in protection through sloughing off during abrasion. The keratinized cells protect tissue from water loss. Stratified Cuboidal, usually confined to the lining of the larger excretory ducts of exocrine glands such as salivary glands. Found in the ducts of larger glans and possess 23 layers of cuboidal cells. Serves in excretion and secretion. Stratified Columnar, seen in the pharynx, epiglottis, anus, mammary glands, salivary glands, and urethra. Serves in minor protection. Transitional Epithelium, tissue that can stretch and/or distend. The first layer is made of large, round binucleated cells on the surface. The second layer is made up of intermediately sized cells that are polygonal. The third layer of cells is the basal layer and is cuboidal. Found only in the urinary system to enable the ureter and bladder to distend.

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Surface Specializations -

Microvilli, tiny finger-like projections that increase the cellular surface area to amplify absorption. Found in the intestines and are composed of microfilaments. Cilia, long hair-like projections found on columnar cells only (respiratory tract, fallopian tubes). These serve to move substance along and are composed of microtubules. Stereocilia, these are long microvilli made of microfilaments. Function in the male reproduction tract. Goblet Cells, synthesize and secrete mucin and look like wine glasses. Found in the respiratory tract and female genital tract. Keratinization, a specialization of stratified squamous to protect epithelium that are subject to abrasion and desiccation. Stratified squamous epithelium are usually described as being keratinized or non-keratinized. Keratin is an amorphous protein made from skin cells. Keratinized skin cells that have arrived at the surface have no nuclei and are sloughed off in abrasion.

Cell Junction -

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Junctions serve to join epithelial cells together and make barriers in between them. There are three types of cell junctions. Tight Junctions, seals adjacent cells in a narrow band just beneath their apical surface. Molecules and ions pass through this junction through diffusion or active transport. Other larger molecules cannot pass through. Desmosomes, localized patches that hold two cells tightly together. o Hemi-Desmosomes, link cells to underlying basement membranes. Gap Junctions, allow adjacent cells to communicate. Permit free transfer and exchange of materials between cells.

Glandular Epithelium -

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Include exocrine and endocrine glands. Exocrine, excretes products to the surface via a duct. o Simple, has one duct (sweat glands) o Compound, have multiple ducts (salivary glands) Endocrine, excretes products into the blood without ducts (thyroid hormones). o Follicles, hormones are stored in follicles and the epithelium is simple cuboidal. o Clump and Cord, secretory cells are surrounded by a rich network of blood supply since the products are secreted into the blood system directly (pituitary and pancreatic glands).

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Muscle -

Can be seen as smooth, cardiac, and skeletal muscle. Composed of cells that optimize the cellular contractibility. All three muscle types have actin and myosin, but cardiac muscles are the only ones to have them in a regular arrangement. Skeletal muscle is subject to voluntary control, while cardiac and smooth muscle are subject to involuntary control. All muscle types are vascularized, with skeletal muscle being the most vascularized.

Skeletal Muscle -

Most vascularized and is striated due to actin and myosin. The cells are multinucleated with nuclei being on the cell periphery. Function in movement and are frequent connected to tendons to attach to bones. Located mostly on bones for movement and occasionally in the skin.

Cardiac Muscle -

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Straited like skeletal muscle but is under involuntary control. Serve to cause heart beats. Muscle fibres are branched with usually 1 or 3 centrally placed nuclei. The cells are much shorter than skeletal muscle. Have a stippled appearance and contain intercalated disks that are specific to cardiac muscles and allow the muscle fibres to join. Intercalated disks allow for heart rhythms. Found in the myocardium. Cells are branching with central nuclei with their junctions made on intercalated disks. Intercalated disks contain three different types of cell-cell junction. o Fascia Adherens, where actin filaments attach thin filaments in the muscle sarcomeres to the cell membrane o Expanded Desmosomes, strong adhesion sites that keep the muscles together during contractions. o Gap Junctions, provide direct contact between cardiac cells. Can be big or small and facilitate electrical communication (depolarization signals) between cardiac muscle cells.

Smooth Muscle -

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Non-branching muscle with elongated nuclei. They are closely arranged in sheets and often described as fusiform, or spindle shaped. They are found in all blood vessels except for capillaries, the respiratory tract and the esophagus (peristalsis). They have actin and myosin but are not striated. The cells tend to overlap each other and are small. There is usually not a lot of space between smooth muscle cells.

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Smooth muscle can be arranged longitudinally or latitudinally. This facilitates peristalsis in the digestive system....