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Tissues Tissue: Group of cells with the same function. Types of tissue: Epithelial, connective, muscle and nervous Cells vary in size, arrangement, shape and function but those of a tissue are similar. Classification of tissue is done by 2 general characteristics Arrangement of cells One layer of cells is called simple More than one layer is called stratified 2.. Type of cells: squamous, cuboidal. and columnar Squamous: looks like a fried egg, or fish scale, unicellular Cuboidal: looks like a dice, unicellular Columnar: looks like a column on a basement membrane Epithelial Tissue Epithelial tissue functions: Cover organs Forms inner lining of body cavities Lines hollow organs The underside of tissue is anchored to connective tissue by a basement membrane. Generally, they lack of blood vessels. The cells are going through mitosis constantly because skin and cells of stomach are constantly being damaged The cells are tightly packaged, with little intercellular material Desmosomes sometimes attach cells in this tissue Types of Epithelial Tissue The types of epithelial tissue are classified according to cell shape and layers. Simple Cuboidal Epithelium. They have a central located nucleus Covers ovaries and kidney tubules Simple Columnar Epithelium; Single layer of elongated cells with nucleus close to the basement. They can be ciliated or non ciliated. They can move the egg of the female ovaries Specialized for absorption Gladular cells that are called goblet cells, secrete protective mucous Simple Squamous Epithelium: Single layer of thin, flattened cells and fit tightly together. Substances pass easily Characteristic of alveolis and kidneys Types of Epithelial Tissues Pseudostratified Columnar Epithelium; Columnar epithelium that appears stratified but it is not, appears stratified because cell nucleus is located at different positions. The cells are generally ciliated The cells secreat mucous Lines the passages of respiratory system Types of Epithelium Stratified Squamous Epithelium: Contain many layers making the tissue thick Cells nearest surface are flattened, deeper layers where cell division occurs are cuboidal or columnar. Newest cells, push old one upper. Older cells accumulate keratin, protective rough material . Lines oral cavities, throat, esophagus, vagina… Stratified Cuboidal Epithelium: Two or three layers of cuboidal cells Lining of lumen Located in sweat glands, salivary glands, mammary glands and pancreas. Stratified Columnar Epithelium: Several layers of cells The superficial cells are elongated, whereas the basal layers a cube shaped. Located in vans deferens, urethra and pharynx Types of Epithelial Cells Gladular Epithelium: Composed of cells that secrete substances in body or outside body. Cells are found within columnar or cuboidal epithelium and one or more cells constitute a gland. Two types of glands: Exocrine: Glands that secrete their products into ducts, onto some internal or external surface Endocrine: Glands that secrete their products into tissue fluid or blood. A simple gland (single epithelial cell) communicates with surface by unbranched duct A compound gland (multicellular gland) communicates by branched ducts Tubular glands have epithelial lined tubes Alveolar glands have saclike dilatation tubes Epithelial Tissue Glands Exocrine glands are also classified according to the ways they secrete their products: Merocrine glands: release products by exocytosis Serous cells: high concentration of enzymes Mucous cells: thicker fluid mucus, rich in mucin (glycoprotein) Apocrine glands: Lose small portions of glandular cells bodies Holocrine glands: release entire body Epithelial Tissue- Transitional Specialized to change in response to pressure. Inner part of urinary bladder Several layers of cuboidal cells. Connective Tissue Much of body weight. Most abundant Provide support and protection and framework Fill spaces, store fat, produce blood cells, prevent against diseases and help to repair tissue damage. The cells are farther apart than epithelial cells. They have abundant intercellular material or matrix. This matrix consist of fibers or ground substances that varies from solid to semiliqid. Cells can divide Vascular Types of Connective Cells Fixed cells- they are present in stable numbers (present in stable numbers) Fibroblasts- large and star shaped, produce fibers by secreting fibrin Wandering cells- they appear in tissues temporarily( macrophages) Macrophages or histiocytes, they are white cells, specialized in phagocytosis, clear blood from pathogens Mast cells –widely distributed, located near blood vessels and release heparin and histamine.(inflammation) Connective Tissue Fibers Collagenous Fibers: thick threads of protein collagen, major structural protein in the body. They are long, parallel bundles, they are flexible but partially elastic, lots of tensil strength. Hold structures together(ligaments) Elastin Fibers: Bundles of microfibrils embedded in a protein called elastin, weaker than collagen but very elastic, branched in networks. Reticular Fibers: thin collagenous fibers, highly branched, they form supporting networks. Types of Connective Tissue Two categories: Connective tissue proper includes loosed connective tissue, adipose tissue , reticular tissue, dense connective tissue and elastic connective tissue Specialized Connective tissue: includes cartilage, bone and blood Types of Connective Tissue Loose Connective Tissue or Areolar Tissue Delicate thin membranes throughout the body. Cells are mainly fibroblasts, separated by gel like ground substance with lots of collagen. Adipose Tissue or fat. Store fat in droplets within connective tissue, at first they resemble fibroblasts, they enlarge when they accumulate fat, and push their nuclei to a side. This tissue lies beneath the skin, in spaces between muscles, around kidneys, behind eyes and in abdominal membranes, around joints and in the surface of heart. Types of Connective Tissue Dense Connective Tissue: many closely packed, thick, collagenous fibers, fine network of elastic fibers, and a few cells mostly fibroblasts. Subclasses are regular or irregular, according to organization. Fibers of regular dense connective tissue are very strong, and binds together, poor blood supply, slow tissue repair (ligament) Fibers of irregular dense connective tissue are thicker, interwoven and more randomly organized.Found in dermis, inside layers. Elastic Connective Tissue: Consist of yellow, elastic fibers in parallel strands or in branching networks. Collagenous fibers and fibroblasts. Attachments of vertebrae, lining of arteries. Cartilage Cartilage is a rigid connective tissue. Provides support, framework, attachments and protects underlying tissues, and forms structural models for developing bones. Cartilage matrix is abundant and composed of collagenous fibers embedded in gel like ground substance. Ground substance is rich in protein-polysaccharide substance and contains a large amount of water. Cartilage cells or chondrocytes occupy small chambers called lacunae and lie completely in matrix Connective tissue is covered by perichondrium, a cartilaginous structure. Lack of blood supply Get nutrients by diffusion aided by water in matrix Types of Cartilage Three types of cartilage distinguished by the type of intercellular material Fibrocartilage: Contains many large collagen fibers in matrix Tough tissue, shock absorber for structures subject to pressure Found in pads of intervertebral discs, cushion knee and pelvic girdle. Elastic Cartilage: Contains dense network of collagen fibers in matrix Flexibel because contains elastic fibers Found in ears and larynx Hyaline cartilage; it has fine collagen fibers in matrix Most common Looks like white glass Found in bones, nose in embryos skeleton. Bone It is the most rigid connective tissue Its hardness is due to mineral salts, such calcium phosphate and calcium carbonate in its matrix The intercellular material contains a large amount of collagen. Internally supports structures, and protects cranial and thoracic cavities Attachment for muscles Contains red bone marrow Stores and releases inorganic salts Bone matrix is deposited by bone cell, osteocytes. Bone Bone matrix is deposited by osteocytes in thin layers called lamellae, which form concentric patterns around capillaries. These capillaries are located in longitudinal tubes called central, or Harvesian canals. Osteocytes are located in lacunae in the lamellae, and also form concentric circles. The osteocytes and layers of intercellular materials are around a central canal called osteon or Harvesian system. Each central canal contains a blood vessel, cytoplasmic processes that extend outward and pass through minute tubes in the matrix called canaliculi. Gap junctions attach these cellular processes. Materials move rapidly between blood vessels, injured bone heals faster than injured cartilage. Blood It is a connective tissue which cells are suspended in a gluid intercellular matrix called plasma. These cells include, white cells, red cells, and cellular fragments called plasma. Red blood cells transport gases White blood cells fight infections Platelets are involved in blood clotting. Most blood cells form in special tissues in red marrow in the hollow parts of bones. Only red blood cells function within blood vessels, white blood cells migrate from blood to capillary walls and reside in there until they die. Muscle Tissue The cells are called muscle fibers because they are elongated. Cells are contractile, they can shorten and thicken. Three types: skeletal, smooth and cardiac Skeletal: Attach bones Conscious- voluntary Long cells Striated Multinucleated Move head, trunk, facial expressions… Types of Muscle Tissue Cardiac Muscle Involuntary Striated The cells are intercalated by special intercellular junction (intercalated discs) only in cardiac muscle Found in heart. Smooth Muscle Tissue No striations Involuntary Shorter than skeletal, spindle shaped Mononuclei Found in stomach, intestines, bladder, uterus, blood vessels. Nervous Tissue Its cells are called neurons Found in brain, spinal cord and peripheral nerves. The neurons are highly specialized The neurons cordianate, regulate and integrate body functions. Neuroglial cells or supporting cells , carry on phagocytosis and help supply blood vessels. Types of Membranes Two or more types of tissues together and performing the same function is called organ. Epithelial membranes are thin, sheetlike structures that are composed of epithelial and underlying connective tissue and covers body surface and lining cavities. There major types Synovial: composed of connective tissue Serous membranes: line up cavities that lack openings to the outside and reduce friction. Composed of one simple squamous layer and one cuboidal layer. They produce serous fluid. Line thorax and abdomen Mucous membranes: line cavities and open to the outside of body.One epithelium layer over a layer of connective tissue. Line respiratory, urinary and reproductive system.
