Chapter 4 The Tissue Level of. Organization. The Cell (Review) What is a Tissue? 10/28/15. n A tissue is a group of specialized cells

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1 Chapter 4 The Tissue Level of Organization The Cell (Review) What is a Tissue? A tissue is a group of specialized cells Common embryonic origin Function together to carry out specialized activities Hard (bone), semisolid (fat), or liquid (blood) Histology is the science that deals with the study of tissues. Pathologist specialized in laboratory studies of cells and tissue for diagnoses 1

2 4 Types of Tissues Epithelial Covers body surfaces and lines hollow organs, body cavities, duct, and forms glands Connective Protects, supports, and binds organs. Stores energy as fat, provides immunity Muscular Generates the physical force needed to make body structures move and generate body heat Nervous Detect changes in body and responds by generating nerve impulses Cell Junctions Contact points between the plasma membranes of tissue cells 5 most common types: Tight junctions Adherens junctions Desmosomes Hemidesmosomes Gap junctions Tight Junctions Web-like strands of transmembrane proteins Fuse cells together Seal off passageways between adjacent cells Common in epithelial tissues of the stomach, intestines, and urinary bladder Help to retard the passage of substances between cells and leaking into the blood or surrounding tissues 2

3 Adherens Junctions Dense layer of proteins called plaque Resist separation of cells during contractile activities Located inside of the plasma membrane attached to both membrane proteins and microfilaments of the cytoskeleton Transmembrane glycoproteins called cadherins insert into the plaque and join cells In epithelial cells, adhesion belts encircle the cell Desmosomes Contain plaque and cadherins that extends into the intercellular space to attach adjacent cells together Desmosome plaque attaches to intermediate filaments that contain protein keratin Prevent epidermal cells from separating under tension and cardiac muscles cells from pulling apart during contraction Hemidesmosomes Resemble half of a desmosome Do not link adjacent cells but anchor cells to the basement membrane Contains transmembrane glycoprotein integrin Integrins attach to intermediate filaments and the protein laminin present in the basement membrane 3

4 Gap Junctions Connect neighboring cells via tiny fluid-filled tunnels called connexons Contain membrane proteins called connexins Plasma membranes of gap junctions are separated by a very narrow intercellular gap (space) Communication of cells within a tissue Ions, nutrients, waste, chemical and electrical signals travel through the connexons from one cell to another Epithelial Tissues Epithelial tissue consists of cells arranged in continuous sheets, in either single or multiple layers Closely packed and held tightly together Covering and lining of the body Free surface 3 major functions: Selective barrier that regulates the movement of materials in and out of the body Secretory surfaces that release products onto the free surface Protective surfaces against the environment 4

5 General Features of Epithelial Cells Surfaces of epithelial cells differ in structure and have specialized functions Apical (free) surface Faces the body surface, body cavity, lumen, or duct Lateral surfaces Faces adjacent cells Basal surface Opposite of apical layer and adhere to extracellular materials General Features of Epithelial Cells Basement membrane Thin double extracellular layer that serves as the point of attachment and support for overlying epithelial tissue General Features of Epithelial Cells Basement membrane Thin double extracellular layer that serves as the point of attachment and support for overlying epithelial tissue Basal lamina Closer to and secreted by the epithelial cells Contains laminin, collagen, glycoproteins, and proteoglycans Reticular lamina Closer to the underlying connective tissue Contains collagen secreted by the connective tissue cells 5

6 Epithelial Cells Epithelial Tissues Own nerve supply Avascular or lacks its own blood supply Blood vessels in the connective tissue bring in nutrients and eliminate waste High rate of cell division for renew and repair Numerous roles in the body (i.e. protection and filtration) Covering and lining epithelium Outer covering of skin and some internal organs Glandular epithelium Secreting portion of glands (thyroid, adrenal, and sweat glands) Covering and Lining Epithelium Normally classified according to: Arrangement of cells into layers Shapes of cells 6

7 Covering and Lining Epithelium Arrangement of cells in layers Consist of one or more layers depending on function Simple epithelium Single layer of cells that function in diffusion, osmosis, filtration, secretion, or absorption Pseudostratified epithelium Appear to have multiple layers because cell nuclei at different levels All cells do not reach the apical surface Stratified epithelium Two or more layers of cells that protect underlying tissues in areas of wear and tear Different Types of Covering and Lining Epithelium Cells vary in shape depending on their function Squamous Thin cells, arranged like floor tiles Allows for rapid passage of substances Cuboidal As tall as they are wide, shaped like cubes or hexagons May have microvilli Function in secretion or absorption Different Types of Covering and Lining Epithelium Columnar Much taller than they are wide, like columns May have cilia or microvilli Specialized function for secretion and absorption Transitional Cells change shape, transition for flat to cuboidal Organs such as urinary bladder stretch to larger size and collapse to a smaller size 7

8 Simple Epithelium Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium (nonciliated and ciliated) Pseudostratified columnar epithelium (nonciliated and cilated) Simple squamous epithelium Single layer of cells that resembles a tiled floor on the surface Nucleus is centrally located and appears flattened oval or sphere Found at sites for filtration or diffusion Simple cuboidal epithelium Cuboidal shaped cells Cell nuclei round and centrally located Found in thyroid gland and kidneys Functions in secretion and absorption 8

9 Simple columnar epithelium Column shaped cells Oval nuclei at near base Nonciliated and ciliated Nonciliated simple columnar epithelium Contains columnar cells with microvilli at their apical surface and goblet cells Secreted mucus serves as lubricant for the lining of digestive, respiratory, reproductive and urinary tracts Also prevents the destruction of the stomach lining by acidic gastric juices Ciliated simple columnar epithelium Columnar epithelial cells with cilia at the apical surface In respiratory tract, goblet cells are interspersed among ciliated columnar epithelia Secreted mucus on the surface traps inhaled foreign particles. Beating cilia moves particles to the throat for removal by coughing, swallowing, or sneezing Cilia also moves oocytes to the uterine tubes 9

10 Ciliated simple columnar epithelium Ciliated simple columnar epithelium Covering and Lining Epithelium Pseudostratified columnar epithelium Appears to have several layers due to nuclei are various depths All cells are attached to the basement membrane in a single layer but some do not extend to the apical surface Ciliated cells secrete mucus and bear cilia Nonciliated cells lack cilia and goblet cells 10

11 Covering and Lining Epithelium Stratified Epithelium Two or more layers of cells Specific kind of stratified epithelium depends on the shape of cells in the apical layer Stratified squamous epithelium Stratified cuboidal epithelium Stratified columunar epithelium Transitional epithelium Stratified Squamous Epithelium Several layers of cells that are flat in the apical layer New cells are pushed up toward apical layer As cells move further from the blood supply they dehydrate, harden, and die Keratinized form contain the fibrous protein keratin Found in superficial layers of the skin Nonkeratinized form does not contain keratin Found in mouth and esophagus 11

12 Stratified Cuboidal Epithelium Fairly rare type of epithelium Apical layers are cuboidal Functions in protection Stratified columnar epithelium Also very uncommon Columnar cells in apical layer only Basal layers has shorten, irregular shaped cells Functions in protection and secretion Transitional Epithelium Found only in the urinary system Variable appearance In relaxed state, cells appear cuboidal Upon stretching, cells become flattened and appear squamous Ideal for hollow structure subjected to expansion 12

13 Glandular Epithelium: Endocrine Glands Secretions, called hormones, diffuse directly into the bloodstream Function in maintaining homeostasis Glandular Epithelium: Exocrine Glands Secrete products into ducts that empty onto the surfaces of epithelium Skin surface or lumen of a hollow organ Secretions of the exocrine gland include mucus, sweat, oil, earwax, saliva, and digestive enzymes Examples of glands include sudoriferous (sweat) glands Structural Classification of Exocrine Glands Multicellular glands are categorized according to two criteria: Ducts are branched or unbranched Shape of the secretory portion of the gland Simple gland duct does not branch Compound gland duct branches Tubular glands have tubular secretory parts Acinar glands have rounded secretory parts Tubuloacinar glands have both tubular and rounded secretory parts 13

14 Structural Classification of Exocrine Glands Functional Classification of Exocrine Glands 14

15 What have we been talking about? Can you name Connective Tissues? Connective Tissues Name the types of connective tissues. Proper Cartilage Bone Blood 15

16 Connective Tissue Most abundant and widely distributed tissues in the body Numerous functions Binds tissues together Supports and strengthen tissue Protects and insulates internal organs Compartmentalize and transport Energy reserves and immune responses Cells and Fibers in Connective Tissue Connective Tissue Cells Fibroblasts Secrete fibers and components of ground substance Adipocytes (fat cells) Store triglycerides (fat) Mast cells Produce histamine White blood cells Immune response Neutrophil and Eosinophils Macrophages Engulf bacteria and cellular debris by phagocytosis Plasma cells Secrete antibodies 16

17 Do Now: Name as many cells of the Connective tissue as you can. (There are 6 we covered so far) Connective Tissue Extracellular Matrix Ground substance Between cells and fibers Fluid, semifluid, gelatinous, or calcified Functions to support and bind cells, store water, and allow exchange between blood and cells Complex combination of proteins and polysaccharides Fibers Collagen fibers Elastic fibers Reticular fibers 17

18 Remember we talked about all of these? Fibroblasts Secrete fibers and components of ground substance Adipocytes (fat cells) Store triglycerides (fat) Mast cells Produce histamine White blood cells Immune response Neutrophil and Eosinophils Macrophages Engulf bacteria and cellular debris by phagocytosis Plasma cells Secrete antibodies Classification of Connective Tissues Embryonic connective tissue Mesenchyme and mucous connective tissue Mature connective tissue Loose connective tissue Areolar, adipose, and reticular Dense connective tissue Dense regular, dense irregular, and elastic Cartilage Hyaline, fibrocartilage, and elastic cartilage Bone tissue Liquid connective tissue Blood and lymph Embryonic Connective Tissue Mesenchyme Gives rise to all other connective tissues Mesenchymal cells are the builders Mucous (Wharton s Jelly) Found in umbilical cord of the fetus 18

19 Loose Connective Tissue: Areolar Connective Tissue Most widely distributed in the body Contains several types of cells and all three fibers 19

20 Loose Connective Tissue: Adipose Tissue Contains adipocytes Good for insulation and energy reserves White (common) and brown adipose tissue 20

21 Adipose Tissue How much fat do you have in your body? Can you get rid of it? Can you gain more? Mesenchymal Cells didn t we talk about them. Loose Connective Tissue: Reticular Connective Tissue Fine interlacing reticular fibers and cells Forms the stroma of liver, spleen, and lymph nodes 21

22 Dense Connective Tissue Dense connective tissue Contains numerous, thicker, and denser fibers Packed closely with fewer cells than loose connective tissue Dense regular connective tissue Bundles of collagen fibers are regularly arranged in parallel patterns for strength Tendons and most ligaments Types of Mature Connective Tissue: Dense Irregular Connective Tissue Collagen fibers are usually irregularly arranged Found where pulling forces are exerted in many directions Dermis of skin and heart 22

23 Dense Connective Tissue: Elastic Connective Tissue Contain branching elastic fibers Strong and can recoil to original shape after stretching Lung tissue and arteries 23

24 Types of Mature Connective Tissue: Cartilage Cartilage is a dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate Chrondrocytes Cartilage cells found in the spaces called lucunae Pericondrium Covering of dense irregular connective tissue that surrounds the cartilage Two layers: outer fibrous layer and inner cellular layer No blood vessels or nerves, except pericondrium Hyaline cartilage Most abundant cartilage in the body Surrounding by perichondrium (some exceptions like articular cartilage) Provide flexibility and support. Reduces friction 24

25 Fibrocartilage Chondrocytes are scattered among bundles of collagen fibers within the extracellular matrix Lack a perchondrium Strongest type of cartilage Found in intervertebral disc (between vertebrae) Elastic Cartilage Chrondrocytes are located within a threadlike network of elastic fibers Pericondrium is present Provides strength and elasticity 25

26 Bone tissue Bones are organs composed of several different connective tissues: bone (osseous) tissue, periosteum, and endosteum. Compact or spongy Osteon or haversian system Spongy bone lacks osteons. They have columns called trabeculae 26

27 Liquid Connective Tissue Blood tissue Connective tissue with liquid extracellular matrix called blood plasma Lymph 27

28 Review What did we just learn about all of the connective tissues? What about the epithelial tissue? Muscle is next Muscular Tissue Consists of elongated cells called muscle fibers or myocytes Cells use ATP to generate force Several functions of muscle tissue Classified into 3 types: skeletal, cardiac, and smooth muscular tissue Skeletal Muscle Tissue Attached to bones of the skeleton Have striations Voluntary movement or contractions by conscious control Vary in length (up to 40 cm) and are roughly cylindrical in shape 28

29 Skeletal Muscle Tissue Attached to bones of the skeleton Have striations Voluntary movement or contractions by conscious control Vary in length (up to 40 cm) and are roughly cylindrical in shape Muscular Tissue Cardiac muscle tissue Have striations Involuntary movement or contraction is not consciously controlled Intercalated disc unique to cardiac muscle tissue Muscular Tissue Cardiac muscle tissue Have striations Involuntary movement or contraction is not consciously controlled Intercalated disc unique to cardiac muscle tissue 29

30 Smooth Muscle Tissue Walls of hollow internal structures Blood vessels, airways of lungs, stomach, and intestines Nonstriated Usually involuntary control Smooth Muscle Tissue Walls of hollow internal structures Blood vessels, airways of lungs, stomach, and intestines Nonstriated Usually involuntary control Nervous Tissue Consists of two principle types of cells Neurons or nerve cells Neuroglia 30

31 Excitable Cells Neurons and muscle fibers Exhibit electrical excitability The ability to respond to certain stimuli by producing electrical signals such as action potentials Actions potentials propagate along a nerve or muscle plasma membrane to cause a response Release of neurotransmitters Muscle contraction Aging and Tissues Tissue heal faster in young adults Surgery of a fetus normally leaves no scars Young tissues have a better nutritional state, blood supply, and higher metabolic rate Extracellular components also changes with age Changes in the body s use of glucose, collagen, and elastic fibers contribute to the aging process End of Chapter 4 Copyright 2009 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein. 31