BIOH111. o Cell Biology Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system

Transcription

1 BIOH111 o Cell Biology Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system Endeavour College of Natural Health endeavour.edu.au 1

2 Textbook and required/recommended readings o Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 4 Endeavour College of Natural Health endeavour.edu.au 2

3 BIOH111 Tissue Module o Session 4 (Lectures 7 and 8): Tissue level organisation tissue types and general features of epithelial tissue o Session 5 (Lectures 9 and 10): Tissue level organisation general features of remaining tissue types and membranes Endeavour College of Natural Health endeavour.edu.au 3

4 BIOH111 Session 4: Lectures 7 and 8 Tissue Level Organisation Bioscience Department endeavour.edu.au

5 Objectives Lecture 7: Cell-to-cell connections and tissue types Describe types of cell-to-cell junctions Relate junctions to the types and function of different tissue types Lecture 8: General features of epithelial tissue Classify epithelial tissue types and describe their functions Endeavour College of Natural Health endeavour.edu.au 5

6 LEVELS OF ORGANIZATION Endeavour College of Natural Health endeavour.edu.au 6

7 TO BUILD A BODY YOU FIRST NEED TO PUT CELLS TOGETHER o In a multi-cellular organism most cells remain in place and anchored to other cells a basement membranes connective tissues o Exceptions include phagocytes and embryonic cells involved in differentiation and growth. o Connections between cells and basement membranes are provided by cell junctions Endeavour College of Natural Health endeavour.edu.au 7

8 CELL JUNCTIONS Definition: Cell junctions are points of contact between adjacent cell plasma membranes. o Depending on their structure, cell junctions may serve one of three functions. Some cell junctions form fluid-tight seals. Some cell junctions anchor cells together or to extracellular material. Some act as channels, which allow ions and molecules to pass from cell to cell. Endeavour College of Natural Health endeavour.edu.au 8

9 CELL JUNCTION TYPES a) Tight junctions b) Adherens junctions c) Gap junction d) Hemidesmosomes e) Desmosomes Endeavour College of Natural Health endeavour.edu.au 9

10 o Structure: plasma membranes fused with a strip of proteins TIGHT JUNCTIONS o Function: watertight seal between cells o Where can it be found: common between cells that line GI and bladder Endeavour College of Natural Health endeavour.edu.au 10

11 ADHERENS JUNCTIONS o Structure: plaque = dense layer of proteins inside the cell membrane where actin filaments extend into cytoplasm and integral membrane proteins connect membranes of the two cells o Function: Holds epithelial cells together o Where can it be found: common between cells that line GI Endeavour College of Natural Health endeavour.edu.au 11

12 GAP JUNCTIONS o Structure: Tiny space between plasma membranes of 2 cells that is crossed by protein channels called connexons forming fluid filled tunnels o Function: Cell communication with ions & small molecules o Where can it be found: heart and smooth muscle of gut; muscle and nerve impulses spread from cell to cell Endeavour College of Natural Health endeavour.edu.au 12

13 DESMOSOMES o Structure: Similar structure to adherens junction except connects to the intermediate filaments within the cytoplasm of the two connected cells o Function: Cell-to-cell stability o Where can it be found: skin and cardiac muscle Endeavour College of Natural Health endeavour.edu.au 13

14 HEMIDESMOSOMES o Structure: Half a desmosome; same structure as desmosome but it connects cell to the undelaying basement membrane and extracellular material using integrins NOT cadherins o Function: Cell-to-membrane stability o Where can it be found: any cell attached to the basement membrane Endeavour College of Natural Health endeavour.edu.au 14

15 HOW DO CELLS CONNECT TO THE BASAL MEMBRANE? THROUGH PROTEINS IN ECM.. Hemidesmosomes Endeavour College of Natural Health endeavour.edu.au 15

16 CELLS JOINED TOGETHER MAKE A TISSUE Definition: Tissue is a group of similar cells that are specialized for a particular function. Endeavour College of Natural Health endeavour.edu.au 16

17 TYPES OF TISSUES Four principal types based on function and structure: 1. Epithelial tissue: covers body surfaces, lines hollow organs, body cavities, and ducts; and forms glands lecture Connective tissue: protects and supports the body and its organs, binds organs together, stores energy reserves as fat, and provides immunity. lecture Muscle tissue: responsible for movement and generation of force. lecture Nervous tissue: initiates and transmits action potentials (nerve impulses) that help coordinate body activities. lecture 12 Endeavour College of Natural Health endeavour.edu.au 17

18 Revision Why does our body need 4 types of tissue? Did you think we have only 4 or did you expect more or less types? Talk among yourselves about: - Which type of cell junctions prevents the content of an organ from leaking out into the surrounding tissues? - Where you think you would find different types of tissue? Why is this important? Endeavour College of Natural Health endeavour.edu.au 18

19 Objectives Lecture 7: Cell-to-cell connections and tissue types Describe types of cell-to-cell junctions Relate junctions to the types and function of different tissue types Lecture 8: General features of epithelial tissue Classify epithelial tissue types and describe their functions Endeavour College of Natural Health endeavour.edu.au 19

20 EPITHELIAL TISSUE Structure: o Closely packed cells with little extracellular material that always have a free surface Many cell junctions often provide secure attachment. o Cells sit on basement membrane Apical (upper) free surface Basal surface against basement membrane o Avascular---without blood vessels nutrients and waste must move by diffusion o Good nerve supply o Rapid cell division (high mitotic rate) oerpub.github.io Endeavour College of Natural Health endeavour.edu.au 20

21 BASEMENT MEMBRANE o Structure: Basal lamina (composed of collagen fibers produced by the epithelial cells) and Reticular lamina (secreted by connective tissue cells and composed of reticular fibers) o Functions: guide for cell migration during development may become thickened due to increased collagen and laminin production Endeavour College of Natural Health endeavour.edu.au 21

22 Functions: EPITHELIAL TISSUE o Selective barrier helps transfer of substances in and out of the body filtration, absorption, digestion, transportation o Secretory surface releases molecules produced by the cells into the free surface secretion, excretion o Protective surface resists any abrasive influence of the environment sensory reception, reproduction Based on these functions epithelial tissue is divided into 2 types: o Covering and lining epithelium- e.g. epidermis of skin, lining of blood vessels, ducts, respiratory, reproductive, urinary & GI tract o Glandular epithelium e.g. secreting portion of glands (thyroid, adrenal, and sweat glands) Endeavour College of Natural Health endeavour.edu.au 22

23 CLASSIFICATION OF EPITHELIUM o Classified by arrangement of cells within a layer: simple = one cell layer thick stratified = two or more cell layers thick pseudo stratified = cells contact BM but all cells don t reach apical surface (nuclei are located at multiple levels so it looks multilayered) o Classified by the shape of cells: squamous = flat cuboidal = cube-shaped columnar = tall column transitional = shape varies with tissue stretching Endeavour College of Natural Health endeavour.edu.au 23

24 CLASSIFICATION OF EPITHELIUM Combining of the two classification characteristics yields 8 types of covering and lining epithelium (4 simple epithelia and 4 stratified epithelia) Endeavour College of Natural Health endeavour.edu.au 24

25 SIMPLE SQUAMOUS EPITHELIUM Single layer of flat, scale-like cells (tiled floor) - nuclei are centrally located and cells are in direct contact with each other - adapted for diffusion, osmosis &filtration - found in lungs and kidneys Endeavour College of Natural Health endeavour.edu.au 25

26 SIMPLE CUBOIDAL EPITHELIUM Consists of a simple layer of cube-shaped cells nuclei are round and centrally located adapted for secretion and absorption lines tubes of kidney Endeavour College of Natural Health endeavour.edu.au 26

27 SIMPLE COLUMNAR EPITHELIUM Consists of a single layer of columnar, rectangular cells and goblet cells (secrete mucus). Can exist in two forms: Non-ciliated simple columnar epithelium: columnar cells with microvilli - increase surface and the rate of absorption - Lines GI tract Ciliated simple columnar epithelium: columnar epithelial cells with cilia provides motility and helps to move fluids or particles along a surface Lines uterine tubes, bronchioles and brain ventricles Endeavour College of Natural Health endeavour.edu.au 27

28 PSEUDOSTRATIFIED COLUMNAR EPITHELIUM Consists of a single layer of columnar, rectangular cells BUT appears to have several layers because the nuclei are at various levels. Can exist in two forms: Non-ciliated pseudostratified epithelium: Nonciliated columnar epithelium contains no cilia or goblet cells. - absorption and protection - lines larger ducts, epididymis, male urethra Ciliated pseudostratified epithelium: columnar epithelial cells with cilia and goblet cells provides motility and helps to move fluids or particles along a surface lines airways Endeavour College of Natural Health endeavour.edu.au 28

29 STRATIFIED SQUAMOUS EPITHELIUM Consists of several layers of cells - top layer of cells is flat, deeper layers of cells vary from cuboidal to columnar. Basal cells replicate by mitosis. 2 types: o Keratinized stratified squamous epithelium - a tough layer of keratin (a protein resistant to friction and repels bacteria) is deposited in the surface cells; superficial layer of skin o Nonkeratinized epithelium remains moist; lines mouth and vagina Endeavour College of Natural Health endeavour.edu.au 29

30 STRATIFIED CUBOIDAL EPITHELIUM Consists of 2 or more layers of cells where top layer is cubeshaped; rare tissue - Protective role - Ducts of sweat glands Endeavour College of Natural Health endeavour.edu.au 30

31 STRATIFIED COLUMNAR EPITHELIUM Consists of 2 or more layers of cells where top layer is columnar and bottom layer(s) are irregular in shape - somewhat rare - protection and secretion - Lines large excretory ducts, part of conjunctiva of the eye Endeavour College of Natural Health endeavour.edu.au 31

32 TRANSITIONAL EPITHELIUM Consists of several layers of cells of variable shape. - capable of stretching, so it permits distention of an organ - lines the urinary bladder and portions of the ureters and the urethra Endeavour College of Natural Health endeavour.edu.au 32

33 Revision Talk in groups of 3-4: why do you think all these different epithelia are important? What is the difference between the cells that constitute the specific epithelia type? Can you connect this to the cell module think about cellular processes you learned there to understand the tissue module.. Glands and glandular epithelium next Endeavour College of Natural Health endeavour.edu.au 33

34 GLANDS Gland is a single cell or a mass of epithelial cells adapted for secretion. 2 types: o Endocrine glands are ductless. o Exocrine glands secrete their products into ducts that empty at the surface of covering and lining epithelium (e.g. skin surface or lumen of a hollow organ) Endeavour College of Natural Health endeavour.edu.au 34

35 GLANDULAR EPITHELIUM LINES THE GLANDS Exocrine glands o Glandular epithelium cells secrete sweat, ear wax, saliva, digestive enzymes onto free surface of epithelial layer and never into the bloodstream o connected to the surface by tubes (ducts) o Classified based on their structure and function Endocrine glands o secrete hormones into the interstitial fluid and then diffuse into the bloodstream. Once they reach their destination hormones help maintain homeostasis This epithelium will be covered in detail in Endocrine System Module Endeavour College of Natural Health endeavour.edu.au 35

36 STRUCTURAL CLASSIFICATION OF EXOCRINE GLANDS 2 types: Multicellular glands 1. Unicellular glands e.g. goblet cells 2. Multicellular glands - branched (compound) or un-branched (simple) - tubular or acinar (flasklike) shape Endeavour College of Natural Health endeavour.edu.au 36

37 FUNCTIONAL CLASSIFICATION OF EXOCRINE GLANDS 1. Merocrine glands Description: form the secretory products and discharge it by exocytosis most exocrine glands e.g. saliva, digestive enzymes & watery (sudoriferous) sweat Endeavour College of Natural Health endeavour.edu.au 37

38 FUNCTIONAL CLASSIFICATION OF 2. Apocrine glands EXOCRINE GLANDS Description: accumulate secretory products at the apical surface of the secreting cell; that portion then pinches off from the rest of the cell to form the secretion with the remaining part of the cell repairing itself and repeating the process e.g. smelly sweat; found in armpits and ear canal Endeavour College of Natural Health endeavour.edu.au 38

39 FUNCTIONAL CLASSIFICATION OF EXOCRINE GLANDS 3. Holocrine glands Description: accumulate the secretory product in the cytosol; cell dies and its products are discharged; the discharged cell is then replaced by a new one e.g. oil gland Endeavour College of Natural Health endeavour.edu.au 39

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