Cells into Tissues

1. Cells into Tissues • Differentiating of cell types during development • Germ Layers • Endoderm • Mesoderm • Ectoderm

3. Endoderm

4. Endoderm • epithelial lining of the whole of the digestive tube • lining cells of all the glands which open into the digestive tube • the epithelium of the auditory tube and tympanic cavity; trachea, bronchi, and air cells of the lungs; urinary bladder and part of the urethra; and follicle lining of the thyroid gland and thymus. • stomach, colon, liver, pancreas, urinary bladder, lining of the urethra, epithelial parts of trachea, lungs, pharynx, thyroid, parathyroid, intestines.

5. Mesoderm

6. Mesoderm • The formation of a mesoderm led to the development of a coelom. • Organs formed inside move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks. • Forms skeletal muscle, skeleton, dermis of skin, connective tissue, urogenital system, heart, blood and vessels, spleen.

7. Ectoderm

8. Ectoderm • Forms CNS, the lens of the eye, cranial and sensory, ganglia and nerves, pigment cells, head connective tissues, epidermis, hair, and mammary glands.

9. 4 Types of Tissue • Epithelium • Connective • Muscle • Nervous

10. Tissues: groups of cells closely associated that have a similar structure and perform a related function • Four types of tissue • Epithelial = covering • Connective = support • Muscle = movement • Nervous = control • Most organs contain all 4 types • Connective tissue has non-living extra-cellular material (matrix) between its cells

11. Epithelial and Connective Tissues • Epithelial tissues • Classes • Junctions • Glands • Connective Tissues • Matrix • Cells • Types

12. EPITHELIAL TISSUES • Sheets of cells • Specialized contacts/cell junctions (see below) • Basal lamina: protein scaffolding secreted by epithelial cells • Basement membrane: reticular fibers (crossed collagen network) that supports epithelium--really associated connective tissue

13. EPITHELIAL TISSUES CON’T… • Connective tissue support • Nutrients from capillaries in underlying connective tissue • Nerves pass through • Easily regenerates • E.g. skin, lining of gut, mucous membranes

14. Simple: just one layer or cell shape Stratified: multiple layers and cell shapes Classes of Epithelia

15. Simple Epithelia

16. Squamous E.g. epidermis Transitional epithelium E.g. urinary structures--bladder Stretches from 6 cells to 3 cells thick as bladder fills and expands Stratified Epithelia

18. Quiz!! E Can You Identify the Classes of Epithelium? D A B C

19. Cell Junctions • Desmosome: binding spots between cells with proteins called cadherins • Tight junctions: impermeable • E.g. gut tube, doesn’t let enzymes from gut into blood stream • Gap junctions: tubes that let small molecules pass between cells

21. Features of Apical Surface of Epithelium • Microvilli:(ex) in small intestine • Finger-like extensions of the plasma membrane of apical epithelial cell • Increase surface area for absorption • Cilia: (ex) respiratory tubes • Whip-like, motile extensions • Moves mucus, etc. over epithelial surface 1-way • Flagella:(ex) spermatoza • Extra long cilia • Moves cell

22. Features of Lateral Surface of Epithelium • Cells are connected to neighboring cells via: • Proteins-link cells together, interdigitate • Contour of cells-wavy contour fits together • Cell Junctions • Desmosomes-adhesive spots on lateral sides • Tight Junctions-at apical area, plasma membrane of adjacent cells fuse, nothing passes • Gap junction-spot-like junction occurring anywhere, lets small molecules pass

23. Features of the Basal Surface of Epithelium • Basal lamina: supportive sheet between epithelium and underlying connective tissue • Selective filter • Basement membrane = basal lamina plus underlying reticular fiber layer • Attaches epithelium to connective tissue below • Sometimes the two are used interchangeably

24. Name that Epithelial Feature!(name and location on cell) 3 • Cilia • Tight junction • Microvilli • Basement membrane 3 1 1 2 2 4 4

25. Glands: epithelial cells that make and secrete a water-based substance • Exocrine Glands • Secrete substance onto body surface or into body cavity • Have ducts • E.G., salivary, mammary, pancreas, liver • Endocrine Glands • Secrete product into blood stream • Either stored in secretory cells or in follicle surrounded by secretory cells • Hormones travel to target organ to increase response • No ducts

27. CONNECTIVE TISSUES • “Areolar tissue” as model • Connects skin to underlying structures • Universal in body • Underlies epithelium, supports capillaries, small. • Always originates from mesenchyme • CELLS in MATRIX

28. Extracellular matrix • Fibers • Collagen gives structure • Reticular fibers (crossed collagen) gives order • Elastin gives elasticity • Ground substance • Jelly-like material made of sugar-protein molecules (proteoglycans)

29. Cells of Connective Tissues • Fibroblasts make fibers • Immune cells in areolar tissue • Macrophages • Plasma cells • Mast cells • Neutrophils, Lymphocytes

31. “Loose” connective tissues • Adipose tissue mostly under skin and in mesenteries • Reticular: organized 3-D network of fibers that support lots of cells • E.g. marrow, spleen, lymph nodes

32. “Dense” Connective tissues • Irregular • Thick fibers running in many planes • E.g. dermis, fibrous capsules around organs • Regular • Aligned parallel fibers • Resists tension • E.g. tendon, ligaments, aponeuroses • Sometimes with elastic fibers (e.g. ligamentum nuchae)

33. Other Connective Tissues • Bone • Cartilage • Blood