TISSUES 1 Introduction Similar cells with a common

TISSUES 1

Introduction • Similar cells with a common function are called tissues. • The study of tissues is called histology. • There are four (4) primary or major tissue types: 1. 2. 3. 4. Epithelial Tissue Connective Tissue Muscle Tissue Nervous Tissue 2

Intercellular Junctions Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Tight junctions • Close space between cells • Located among cells that form linings Desmosomes • Form “spot welds” between cells • Located among outer skin cells Gap junctions • Tubular channels between cells • Located in cardiac muscle cells Cell membrane Tight junction Cell membrane Desmosome Cell membrane Gap junction 3

Epithelial Tissue • General characteristics: • Cover organs and the body • Line body cavities • Line hollow organs • Have a free surface • Have a basement membrane • Are avascular • Cells readily divide • Cells tightly packed • Cells often have desmosomes • Function in protection, secretion, absorption, and excretion • Classified according to cell shape and number of cell layers 4

Epithelial Tissue • Simple squamous: • Simple cuboidal: • Single layer of flat cells • Substances pass easily through • Line air sacs • Line blood vessels • Line lymphatic vessels • Single layer of cube-shaped cells • Line kidney tubules • Cover ovaries • Line ducts of some glands Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Free surface of tissue Lumen Nucleus Simple squamous epithelium Basement membrane Basement Free surface of tissue Nucleus Simple cuboidal epithelium Connective tissue (a) (b) b, d: © Ed Reschke (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer 5

Epithelial Tissue • Simple columnar: • Pseudostratified columnar: • Single layer of elongated cells • Nuclei usually near the basement • Membrane at same level • Sometimes possess cilia • Sometimes possess microvilli • Often have goblet cells • Line uterus, stomach, intestines • Single layer of elongated cells • Nuclei at two or more levels • Appear striated • Often have cilia • Often have goblet cells • Line respiratory passageways Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Cilia (free surface of tissue) Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Mucus Goblet cell Nucleus Cytoplasm Basement membrane Microvilli (free surface of tissue) Connective tissue Goblet cell (a) (b) Basement membrane b: © The Mc. Graw-Hill Companies, Inc. /Dennis Strete, photographer Connective tissue (a) (b) 6 b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer.

Epithelial Tissue • Stratified squamous: • Stratified cuboidal: • Many cell layers • Top cells are flat • Can accumulate keratin • Outer layer of skin • Line oral cavity, vagina, and anal canal • 2 -3 layers • Cube-shaped cells • Line ducts of mammary glands, sweat glands, salivary glands, and the pancreas Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Free surface of tissue Stratified cuboidal epithelium Nucleus Squamous cells Lumen Free surface of tissue Basement membrane (a) Connective tissue (b) Layer of dividing cells Basement membrane b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer. Connective tissue (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer 7

Epithelial Tissue • Transitional: • Stratified columnar: • Many cell layers • Cube-shaped and elongated cells • Line urinary bladder, ureters, and part of urethra • Top layer of elongated cells • Cube-shaped cells in deeper layers • Line part of male urethra and part of pharynx Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Free surface of tissue Unstretched transitional epithelium Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Lumen Basement membrane Free surface of tissue Stratified columnar epithelium (a) Basement membrane Free surface of tissue Stretched transitional epithelium Connective tissue (a) Underlying connective tissue (b) Basement membrane Underlying connective tissue b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer (c) (d) b, d: © Ed Reschke 8

Glandular Epithelium • Composed of cells that are specialized to produce and secrete substances • There are two (2) types: • Endocrine glands are ductless (key word: hormone) • Exocrine glands have ducts • Unicellular exocrine gland: • Composed of one cell • Goblet cell • Multicellular exocrine gland: • Composed of many cells • Sweat glands, salivary glands, etc. • Simple and compound 9

Structural Types of Exocrine Glands Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Tissue surface Duct Secretory portion Simple tubular Simple branched tubular Compound tubular Simple coiled tubular Compound alveolar Simple branched alveolar 10

Types of Glandular Secretions • Merocrine Glands • Apocrine Glands • Fluid product • Salivary glands • Pancreas gland (? ) • Sweat glands • Serous Fluid • Mucus Intact cell Secretion • Cellular product • Portions of cells • Mammary glands • Ceruminous glands Pinched off portion of cell (secretion) • Holocrine Glands • Secretory products • Whole cells • Sebaceous glands Disintegrating cell and its contents (secretion) New cell forming by mitosis and cytokinesis (a) Merocrine gland (b) Apocrine gland (c) Holocrine gland 11

Connective Tissues • General characteristics: • Most abundant tissue type • Many functions: • Bind structures • Provide support and protection • Serve as frameworks • Fill spaces • Store fat • Produce blood cells • Protect against infections • Help repair tissue damage • Have an extracellular matrix • Have varying degrees of vascularity • Have cells that usually divide 12

Connective Tissue Major Cell Types Present • Fibroblasts • Fixed cell • Most common cell • Large, star-shaped • Produce fibers • Macrophages • Wandering cell • Phagocytic • Important in injury or infection • Mast cells • Fixed cell • Release heparin • Release histamine 13

Connective Tissue Fiber Types Present • Collagenous fibers • Elastic fibers • Thick • Bundles of microfibrils • Composed of collagen embedded in elastin • Great tensile strength • Fibers branch • Abundant in dense CT • Elastic • Hold structures together • Vocal cords, air passages • Tendons, ligaments • Reticular fibers • Very thin collagenous fibers • Highly branched • Form supportive networks 14

Connective Tissues • Connective Tissue Proper: • Specialized Connective Tissue: • Loose connective tissue • Cartilage • Adipose tissue • Bone • Reticular connective tissue • Blood • Dense connective tissue • Elastic connective tissue 15

Connective Tissue Types • Loose Connective Tissue • Adipose Tissue • Mainly fibroblasts • Fluid to gel-like matrix • Collagenous fibers • Elastic fibers • Bind skin to structures • Beneath most epithelia • Blood vessels nourish nearby epithelial cells • Between muscles • Adipocytes • Cushions • Insulates • Store fats • Beneath skin • Behind eyeballs • Around kidneys and heart Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Cytsol Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Fat droplet Collagenous fiber Cell membrane Fibroblast Nucleus (a) Ground substance (b) Elastic fiber (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Dennis Strete, photographer 16 b: © The Mc. Graw-Hill Companies, Inc. /Dennis Strete, photographer

Connective Tissue Types • Reticular Connective Tissue • Dense Connective Tissue • Composed of reticular fibers • Supports internal organ walls • Walls of liver, spleen, lymphatic organs • Packed collagenous fibers • Elastic fibers • Few fibroblasts • Bind body parts together • Tendons, ligaments, dermis • Poor blood supply Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Fibroblasts Collagenous fibers White blood cell (a) (b) Fibroblast (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Dennis Strete, photographer b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer 17

Connective Tissue Types • Elastic Connective Tissue • Bone (Osseous Tissue) • Abundant in elastic fibers • Some collagenous fibers • Fibroblasts • Attachments between bones • Walls of large arteries, airways, heart • Solid matrix • Supports • Protects • Forms blood cells • Attachment for muscles • Skeleton • Osteocytes in lacunae Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Collagenous fibers Osteon Lamella Fibroblast Central canal Elastic fibers Osteocyte in lacuna (a) (b) Canaliculi (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer Osteocyte Nucleus Cell process in canaliculus b: © The Mc. Graw-Hill Companies, Inc. /Dennis Strete, photographer 18 21

Connective Tissue Types • Hyaline cartilage • Cartilage • Rigid matrix • Chondrocytes in lacunae • Poor blood supply • Three (3) types: • Hyaline Cartilage • Elastic Cartilage • Fibrocartilage • Most abundant • Ends of bones • Nose, respiratory passages • Embryonic skeleton • Elastic cartilage • Flexible • External ear, larynx • Fibrocartilage • Very tough • Shock absorber • Intervertebral discs • Pads of knee and pelvic girdle 19

Connective Tissue Types Three (3) types of cartilage: Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Elastic fibers Nucleus Lacuna Chondrocyte Extracellular matrix (a) Extracellular matrix (b) (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer Hyaline Cartilage Elastic Cartilage Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Lacuna Chondrocyte Nucleus Collagenous fiber Extracellular matrix (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer Fibrocartilage 20

Connective Tissue Types • Blood • Fluid matrix called plasma • Red blood cells • White blood cells • Platelets • Transports • Defends • Involved in clotting • Throughout body in blood vessels • Heart Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. White blood cell Red blood cells Plasma (extracellular matrix of blood) Platelets (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer 21

Types of Membranes • There are four (4) types of epithelial membranes: 1. Serous Membranes • Line body cavities that do not open to the outside • Reduce friction • Inner lining of thorax and abdomen • Cover organs of thorax and abdomen • Secrete serous fluid 2. Mucous Membranes • Line tubes and organs that open to outside world • Lining of mouth, nose, throat, etc. • Secrete mucus 3. Cutaneous Membranes • Covers body • Skin 4. Synovial Membranes • Composed entirely of connective tissue • Lines joints 22

Muscle Tissues • Skeletal muscle • General characteristics: • Muscle cells also called muscle fibers • Contractile • Three (3) types: • Skeletal muscle • Smooth muscle • Cardiac muscle • Attached to bones • Striated • Voluntary • Smooth muscle • Walls of organs • Skin • Walls of blood vessels • Involuntary • Non-striated • Cardiac muscle • Heart wall • Involuntary • Striated • Intercalated discs 23

Muscle Tissue Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Striations Cytoplasm Nucleus Nuclei Portion of a muscle fiber (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Dennis Strete, photographer b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer Skeletal Muscle Smooth Muscle Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Striations Nucleus Intercalated disc (a) (b) b: © The Mc. Graw-Hill Companies, Inc. /Al Telser, photographer Cardiac Muscle 24

Nervous Tissue • Found in brain, spinal cord, and peripheral nerves Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. • Functional cells are neurons Cellular process Cytoplasm • Neuroglial cells support and bind nervous tissue components • Sensory reception Nucleus Cell membrane Neuroglial cells (a) (b) b: © Ed Reschke. • Conduction of nerve impulses 25