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Tissues Introduction • Cells are arranged in organized groups called tissues • Each type of tissue has its own special function Types of Tissue • There are four basic types of tissue (1) Epithelium (2) Connective (3) Muscular (4) Nervous 1 Epithelial Tissue • There are two basic types of epithelium (1) Covering and lining epithelium (2) Glandular epithelium Covering and lining epithelium • Forms the outer covering of: - external body surfaces (like the skin) - some internal organs (like the stomach) Lines body cavities Lines the interiors of: - respiratory and gastrointestinal tract - blood vessels, ducts - Hollow reproductive organs (like the uterus) Glandular Epithelium • Makes up the secreting portion of glands 2 The Basement membrane • All epithelium adheres to a connective tissue membrane layer referred to as the basement membrane • The basement membrane attaches the epithelium to the underlying connective tissue The flow chart below illustrates the different types of epithelial tissue 3 Simple Squamous Epithelium • Consists of a single layer of flat cells Description: Looks like a platter of fried eggs “sunny-side up” Location: Air sacs (alveoli) of lungs, lines the inside of heart and blood vessels Function: Filtration, diffusion, osmosis Drawing of Simple Squamous Epithelium Light Micrograph of Simple Squamous Epithelium (Superior aspect) 4 Light micrograph of Simple Squamous Epithelium (Lateral aspect) Simple Cuboidal Epithelium Description: Consists of a single layer of cube-shaped cells Location: Lines kidney tubules and the small ducts of many glands Function: Secretion and absorption Drawing of Simple Cuboidal Epithelium 5 Light micrograph of Simple Cuboidal Epithelium Simple Columnar Epithelium Description: A single layer of tall rectangular cells Location: Lines the gall-bladder and most of the gastrointestinal tract Function: Absorption and secretion Photomicrograph of Simple Columnar Epithelium 6 Stratified Squamous Epithelium Description: Many layers of cells with squamous shaped cells located next to the lumen (light) Location: Keratinized variety on palms of hands and soles of feet Nonkeratinized variety lines the mouth, vagina, and esophagus Function: Protection Drawing of Stratified Squamous Epithelium Photomicrograph of Stratified Squamous Epithelium (Nonkeratinized) 7 Photomicrograph of Stratified Squamous Epithelium (Keratinized) Pseudostratified Ciliated Columnar Epithelium Description: Looks like a stratified tissue but is not. Each cell extends from the basement membrane to the lumen Location: Lines the upper respiratory tract Function: Secretion and movement of mucous by ciliary action Photomicrograph of Pseudostratified Ciliated Columnar Epithelium 8 Transitional Epithelium Description: The appearance can vary greatly, that is why it is called transitional Location: Lines the urinary bladder and ureter Function: Permits distention (stretching) Drawing of Transitional Epithelium Photomicrograph of Transitional Epithelium 9 Connective Tissue • The most abundant tissue type in the body • Most types have a rich blood supply (except Hyaline Cartilage) The flow chart below illustrates the different types of connective tissue The composition of connective tissue • There are three basic elements found in connective tissue (1) Fibers (such as collagen, reticular, and elastic) (2) Cells (such as fibroblasts, macrophages, and adipose) (3) A ground substance (matrix) that surrounds the fibers and cells 10 The matrix (ground substance) of connective tissue (1) Fluid – as in blood (2) Semifluid – as in loose connective tissue (3) Gelatinous – as in mucous connective tissue (4) Fibrous – as in dense regular connective tissue (5) Calcified – as osseous connective tissue (bone) Loose (areolar) Connective Tissue Description: consists of collagen, elastic, and reticular fibers; together with several cell types Location: Hypodermis, around most body organs Function: Loosely binds organs together Photomicrograph of Loose Connective Tissue 11 Vascular Connective Tissue (Blood) • Blood is a connective tissue with a fluid matrix called plasma • Three basic types of cells are found suspended in plasma (1) Erythrocytes (2) Leukocytes (3) Thrombocytes Erythrocytes (Red Blood Cells) Description: Biconcave cells that are stained pink. The inner center of the cell is lighter than the rim Location: Suspended in blood plasma Function: Transports respiratory gases (oxygen and carbon dioxide) Leukocytes (White Blood Cells) Description: Stained cells with an obvious nucleus Location: Suspended in blood plasma, also found in lymphatic tissues Function: Involved in immunity 12 Thrombocytes (Platelets) Description: Small darkly stained structures Location: Suspended in blood plasma Function: Involved in blood clotting Adipose Connective Tissue Description: Resembles a chicken-wire fence. The individual adipocytes have a large central storage area where fats and oils are stored Location: Subcutaneous layer of skin; fatty capsule of kidney, yellow bone marrow; around the heart Function: Energy storage, insulation, protection 13 Photomicrograph of Adipose Connective Tissue Dense Fibrous Connective Tissue (Regular) • Contains numerous collagen fibers oriented in the same direction. This produces great strength in the direction that the fibers run Description: Many collagen fibers running in the same direction. Appears to be “wavy” Location: Tendons and ligaments Function: Attaches muscles to bone (tendons), and bone to bone (ligaments) Further notes on Dense Connective Tissue (Regular) • Is less flexible than Areolar Connective Tissue but is more resistant to stress. The collagen fibers are densely packed and run in on direction. • There is great strength in the direction of the fibers, but relatively weak in a direction at right angles to the direction of the fibers. • The wavy configuration allows some stretching. 14 Photomicrograph of Dense Regular Connective Tissue (Regular) Hyaline Cartilage Connective Tissue • Has a matrix firm enough to bear great pressure without permanent distortion Description: Chondrocytes (cartilage cells) Located in spaces called lacuna, surrounded by a bluish matrix with collagen fibers Location: Ends of long bones, between ribs and sternum, tracheal rings, larynx Function: Reduces fiction in joints, support with flexibility Photomicrograph of Hyaline Cartilage Connective Tissue 15 Osseous Connective Tissue (Bone) • Bone tissue has a hard matrix containing ions such as calcium and phosphorus • The matrix is laid around a dense network of collagen fibers in a layer called lamella • Canals called Haversian are filled with nerves, arteries, veins, and lymphatics Osseous Connective Tissue (Continued) Description: A network of Haversian systems (osteons) Location: Make up the bones of the body Function: Protection, support, mineral and storage. Together with skeletal muscle is responsible for movement Photomicrograph of Bone 16 Muscle Tissue • Muscle tissue is composed of fibers that function to contract and shorten the muscle for contraction • There are three type of muscle based on location, structure and function (1) Skeletal muscle tissue (2) Cardiac muscle tissue (3) Smooth muscle tissue Skeletal Muscle • So-called because it attaches to bones and moves bones. Also called voluntary or striated muscle • Description: Long striated fibers with the nuclei located at the edge of the fibers • Location: Attached to bones by tendons • Function: Moves bone, posture, heat production Photomicrograph of Skeletal Muscle Tissue 17 Smooth Muscle Tissue • Composed of elongated cells that are not striated Description: Long tapered fibers with a centrally located nucleus Location: The walls of hollow organs (such as the stomach and urinary bladder) Function: Movement of substance inside the hollow organ Photomicrograph of Smooth Muscle Tissue Cardiac Muscle Tissue Description: Branched striated fibers with a centrally located nucleus Location: Wall of the heart Function: Pumps blood to all parts of the body 18 Photomicrograph of Cardiac Muscle Tissue Nervous Tissue Description: Large cell bodies with obvious processes extending from them. Many small nuclei of neuroglia cells Location: Nervous system Function: Conducts nerve impulses (Action potentials) 19