Tissues

Tissue A group of similar cells, usually of similar embryonic origin, that function together to carry out specialized activities A group of similar cells, usually of similar embryonic origin, that function together to carry out specialized activities

Histology The science that deals with the study of tissues The science that deals with the study of tissues Pathologist – a scientist who specializes in laboratory studies of cells and tissues to make accurate diagnoses. A pathologist examines tissues for any changes that might indicate disease. Pathologist – a scientist who specializes in laboratory studies of cells and tissues to make accurate diagnoses. A pathologist examines tissues for any changes that might indicate disease.

Types of Tissues Epithelial Tissue Epithelial Tissue Covers body surfaces; lines body cavities, hollow organs and ducts; forms glands Covers body surfaces; lines body cavities, hollow organs and ducts; forms glands Connective Tissue Connective Tissue protect and supports the body and its organs, binds organs together, stores energy reserves as fat, provides immunity protect and supports the body and its organs, binds organs together, stores energy reserves as fat, provides immunity Muscular Tissue Muscular Tissue Generates the force needed to make body structures move Generates the force needed to make body structures move Nervous Tissue Nervous Tissue Detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis Detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis

Cell Junctions Points of contact between plasma membranes of different cells that join them into functional units. Points of contact between plasma membranes of different cells that join them into functional units.

Epithelial Tissue AKA Epithelium AKA Epithelium 2 types: 2 types: Covering and Lining Epithelium Covering and Lining Epithelium Forms the outer covering of the skin and some internal organs. It also lines body cavities, blood vessels, ducts, and the interiors of many of the body systems. Forms the outer covering of the skin and some internal organs. It also lines body cavities, blood vessels, ducts, and the interiors of many of the body systems. Glandular Epithelium Glandular Epithelium Makes the secreting portion of glands Makes the secreting portion of glands

General Features of Epithelium 1. Closely packed cells with little extracellular material between them arranged in sheets 1. Closely packed cells with little extracellular material between them arranged in sheets 2. Surfaces: 2. Surfaces: Apical Surface – exposed to a body cavity, the outside of the body or lining an internal organ Apical Surface – exposed to a body cavity, the outside of the body or lining an internal organ Lateral Surface – Face adjacent cells Lateral Surface – Face adjacent cells Basal Surface – bottom layer attached to a basement membrane (extracellular structure composed mainly of fibers located between epithelium and underlying connective tissue) Basal Surface – bottom layer attached to a basement membrane (extracellular structure composed mainly of fibers located between epithelium and underlying connective tissue)

General Features of Epithelium 3. Avascular – no blood vessels. Epithelial cells must get their nutrients from underlying connective tissue through diffusion 3. Avascular – no blood vessels. Epithelial cells must get their nutrients from underlying connective tissue through diffusion 4. Innervated (have a nerve supply) 4. Innervated (have a nerve supply) 5. High mitotic rate – high capacity for cell division because of wear and tear and injury 5. High mitotic rate – high capacity for cell division because of wear and tear and injury

Covering and Lining Epithelium – Cell Shapes Squamous – flat cells that attach to each other like tiles Squamous – flat cells that attach to each other like tiles Allows for rapid passage of substances through them Allows for rapid passage of substances through them Cuboidal – cells are as tall as they are wide, sometimes contain microvilli Cuboidal – cells are as tall as they are wide, sometimes contain microvilli Function in Secretion and Absorption Function in Secretion and Absorption Columnar – Taller than they are wide, sometimes contain microvilli or cilia Columnar – Taller than they are wide, sometimes contain microvilli or cilia Function in Secretion, Absorption and Protection Function in Secretion, Absorption and Protection Transitional – Cells that have the ability to change shape from Cuboidal to Squamous and back as organs stretch Transitional – Cells that have the ability to change shape from Cuboidal to Squamous and back as organs stretch

Simple Epithelium A single layer of cells found in areas where diffusion, osmosis, filtration, secretions and absorption occur A single layer of cells found in areas where diffusion, osmosis, filtration, secretions and absorption occur

Simple Squamous Epithelium A single layer of flat cells that resembles a tile floor when viewed from the apical surface A single layer of flat cells that resembles a tile floor when viewed from the apical surface Nucleus is a flattened oval found in the center of the cell Nucleus is a flattened oval found in the center of the cell Found where filtration or diffusion take place, not found in areas of high wear and tear Found where filtration or diffusion take place, not found in areas of high wear and tear

Simple Squamous Epithelium Endothelium – simple squamous that lines the heart, blood vessels and lymphatic vessles Endothelium – simple squamous that lines the heart, blood vessels and lymphatic vessles Mesothelium – simple squamous that lines serous membranes (lines cavities not open to the outside of the body, like the abdomen or thorax) Mesothelium – simple squamous that lines serous membranes (lines cavities not open to the outside of the body, like the abdomen or thorax)

Simple Cuboidal Epithelium Single layer of cube shaped cells Single layer of cube shaped cells Found on the surface of the ovary, the lens of the eye and lining of glands as well as the secreting portion of glands Found on the surface of the ovary, the lens of the eye and lining of glands as well as the secreting portion of glands Function in Secretion and Absorption Function in Secretion and Absorption

Simple Columnar Epithelium Single Layer of Column Shaped Cells Single Layer of Column Shaped Cells 2 Forms – cilliated and noncilliated 2 Forms – cilliated and noncilliated

Non-cilliated Simple Columnar Epithelium Contains absorptive cells and goblet cells Contains absorptive cells and goblet cells Absorptive Cells – have microvilli to increase surface area Absorptive Cells – have microvilli to increase surface area Goblet Cells – modified Columnar cells that secrete mucus at the apical surface Goblet Cells – modified Columnar cells that secrete mucus at the apical surface Lines most of the GI tract, ducts of glands and gallbladder Lines most of the GI tract, ducts of glands and gallbladder

Ciliated Simple Columnar Epithelium Cells with cilia at the apical surface, usually interspersed with goblet cells Cells with cilia at the apical surface, usually interspersed with goblet cells Mucus secreted by goblet cells forms a thin layer over the cell surface which is moved by the ciliated cells. Mucus secreted by goblet cells forms a thin layer over the cell surface which is moved by the ciliated cells. Found in the respiratory tract Found in the respiratory tract

Stratified Epithelium Contains 2 or more layers of cells used for protection of underlying tissue in area where there is a lot of wear and tear Contains 2 or more layers of cells used for protection of underlying tissue in area where there is a lot of wear and tear The name of the tissue depends on the shape of the cell on the apical layer The name of the tissue depends on the shape of the cell on the apical layer

Stratified Squamous Epithelium Cells in the apical layer are flat Cells in the apical layer are flat Cells in the deep layers vary in shape Cells in the deep layers vary in shape Basal cells continuously undergo mitosis Basal cells continuously undergo mitosis As they move farther from the basal layer they become dehydrated and harder As they move farther from the basal layer they become dehydrated and harder

Keratinized Stratified Squamous Epithelium Tough layer of keratin is deposited on the top layers to help protect the skin and underlying tissues from microbes, heat and chemicals Tough layer of keratin is deposited on the top layers to help protect the skin and underlying tissues from microbes, heat and chemicals

Nonkeratinized Stratified Squamous Epithelium Does not contain keratin Does not contain keratin Found on the lining of the mouth, esophagus, and tongue Found on the lining of the mouth, esophagus, and tongue

Stratified Cuboidal Epithelium Fairly Rare Fairly Rare 2 or more layers of cells, apical layer is cuboidal 2 or more layers of cells, apical layer is cuboidal Found in sweat glands Found in sweat glands

Stratified Columnar Epithelium Fairly Rare Fairly Rare 2 or more layers of cells, the top layer is columnar 2 or more layers of cells, the top layer is columnar Found in excretory ducts of some glands and some mucous membranes Found in excretory ducts of some glands and some mucous membranes

Transitional Epithelium Varies in appearance depending on whether the organ it lines is distended or relaxed. Varies in appearance depending on whether the organ it lines is distended or relaxed. Looks similar to stratified cuboidal except the top layer is large and rounded Looks similar to stratified cuboidal except the top layer is large and rounded

Pseudostratified Columnar Epithelium Appears to have several layers because the nuclei of the cells are at various depths. Appears to have several layers because the nuclei of the cells are at various depths. All of the cells are attached to the same basement membrane so there is only 1 layer of cells All of the cells are attached to the same basement membrane so there is only 1 layer of cells

Glandular Epithelium Functions in Secretion Functions in Secretion A gland consists of one cell or a group of cells A gland consists of one cell or a group of cells Endocrine Glands – secretions enter the interstitial fluid Endocrine Glands – secretions enter the interstitial fluid Hormones Hormones Exocrine Glands – secrete their products into ducts (tubes) that empty at the surface of the covering/lining epithelium Exocrine Glands – secrete their products into ducts (tubes) that empty at the surface of the covering/lining epithelium Mucus, oil, earwax, digestive enzymes Mucus, oil, earwax, digestive enzymes