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Tissues • Groups of cells similar in structure and function • The four types of tissues – Epithelial • Covers and lines body cavities both inside and outside of the body. – Connective • Protects and insulates vital organs and fills body cavity spaces. Connects different type of tissues to each other. – Muscle • Functions in locomotion, digestive and cardiovascular functions. – Nerve • Communicate electrical impulses which facilitates the action of both muscles and glands. Epithelial Tissue • Covers the entire surface of the body – Skin and reproductive tracts • Barriers between what is in and out of the body. – Lining of the lung, digestive and urinary tracts • controls what substances enter/exit the body and what substances stay in/out of the body • Specialized type types of epithelial tissue include: – exocrine glands • secrete substances outside of the body – (sweat, salivary) – endocrine glands • secrete substances (hormones) into the blood – (insulin, growth hormone) Epithelial Membranes • Serous – moist membranes that line internal organs. Epithelial Membranes Classification of Epithelial Tissues Epithelial tissue is classified based on 2 criteria: – Shape and number of layers • Cell shape – squamous (flattened cells) • cell width is larger than cell height – cuboidal (cube-like cells) • cell width is equal to cell height – columnar (column-like cells) • cell height is larger than cell width Classification of Epithelial Tissues • Number of layers of epithelial cells – Simple • Thin layer allows for exchange of substances into or out of the body – Stratified • Multiple layers protects act as a natural barrier to prevent abrasion, puncture. Epithelia: Simple Squamous Figure 4.2a Epithelia: Simple Cuboidal • Single layer of cubelike cells with large, spherical central nuclei • Function in secretion and absorption • Present in kidney tubules, ducts and secretory portions of small glands, and ovary surface Figure 4.2b Epithelia: Simple Columnar Figure 4.2c Epithelia: Pseudostratified Columnar • Single layer of cells with different heights; some do not reach the free surface • Nuclei are seen at different layers • Function in secretion and propulsion of mucus • Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated) Figure 4.2d Epithelia: Stratified Squamous • Thick membrane composed of several layers of cells • Function in protection of underlying areas subjected to abrasion • Forms the external part of the skin’s epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells) Figure 4.2e Epithelia: Transitional • Several cell layers, basal cells are cuboidal, surface cells are dome shaped • Stretches to permit the distension of the urinary bladder • Lines the urinary bladder, ureters, and part of the urethra Figure 4.2f Connective Tissue • Widely spaced cells separated by fibers and ground substance. Most abundant and variable tissue type – Connective tissue proper – Dense » Regular and Irregular – Loose » Areolar, Adipose, Reticular. – Cartilage • Hyaline, Elastic, Fibrocartilage – Bone • Spongy, Compact – Blood • Fluid connective tissue (plasma ) red blood cells, white blood cells, platelets • Functions – connects organs – gives support and protection (physical and immune) – stores energy and produces heat – movement and transport of materials Connective Tissue Figure 4.5 Structural Elements of Connective Tissue Cells of Connective Tissue • Fibroblasts produce fibers and ground substance – – – – Adipocytes store triglycerides Chondroblasts – produce cartilage Osteoblasts – build bone Hematopoietic stem cells – blood • White blood cells, plasma cells, macrophages, and mast cells Fibers of Connective Tissue • Collagen fibers (white fibers) – tough, stretch resistant, yet flexible • tendons, ligaments and deep layer of the skin • Reticular fibers – thin, collagen fibers coated with glycoprotein • framework in spleen and lymph nodes • Elastic fibers (yellow fibers) – thin branching fibers of elastin protein – stretch and recoil like rubberband (elasticity) • skin, lungs and arteries stretch and recoil Connective Tissue Ground Substance • Gelatinous material between cells – absorbs compressive forces – attract sodium and hold water Ground Substance: Proteoglycan Structure Figure 4.6b Fibrous Connective Tissue Types • Loose connective tissue – gel-like ground substance between cells – types • areolar • reticular • adipose • Dense connective tissue – fibers fill spaces between cells – types vary in fiber orientation • dense regular connective tissue • dense irregular connective tissue Loose Connective Tissue Proper: Areolar Areolar Connective Tissue Figure 4.8b Connective Tissue: Embryonic Figure 4.8a Adipose Connective Tissue Reticular Connective Tissue Figure 4.8d Connective Tissue: Dense Regular Figure 4.8e Connective Tissue : Dense Irregular Figure 4.8f Connective Tissue: Hyaline Cartilage Figure 4.8g Connective Tissue: Elastic Cartilage • Similar to hyaline cartilage but with more elastic fibers • Maintains shape and structure while allowing flexibility • Supports external ear (pinna) and the epiglottis Figure 4.8h Connective Tissue: Fibrocartilage Cartilage • Matrix similar to hyaline cartilage but less firm with thick collagen fibers • Provides tensile strength and absorbs compression shock • Found in intervertebral discs, the pubic symphysis, and in discs of the knee joint Figure 4.8i Connective Tissue: Bone Figure 4.8j Connective Tissue: Blood Figure 4.8k Nervous Tissue Figure 4.10 Muscle Tissue: Skeletal • Long, cylindrical, multinucleate cells with obvious striations • Initiates and controls voluntary movement • Found in skeletal muscles that attach to bones or skin Figure 4.11a Muscle Tissue: Cardiac • Branching, striated, uninucleate cells interdigitating at intercalated discs • Propels blood into the circulation • Found in the walls of the heart Figure 4.11b Muscle Tissue: Smooth Figure 4.11c Tissue Shrinkage and Death • Atrophy = loss of cell size or number – disuse atrophy from lack of use (leg in a cast) • Necrosis = pathological death of tissue – gangrene - insufficient blood supply • Diabetic complications. – infarction - death of tissue from lack of blood • Heart attack or cerebral vascular accident ( stroke) – decubitus ulcer - bed sore or pressure sore • Pressure cuts off blood supply to a specific part of body. • Diabetic Ulcer Bedsores