1. Tissues
The Living Fabric

2. Tissue
– a group of cells that have similar structure and that function together as a unit
Histology
– the microscopic study of tissues

3. Intracellular matrix
– a non-living material that fills the spaces between the cells; may contain special substances such as salts and fibers that are unique to a specific tissue and give that tissue distinctive characteristics

4. Intracellular Junctions
Holds groups of cells together to form tissues found in sheets or other continuous masses of cells
Three types:
Desmosomes
Gap junctions
Tight junctions

5. 1. Desmosomes – small “spot welds” that hold adjacent cells together; fibers interlock with each other

6. 2. Gap junctions – formed when membrane channels of adjacent plasma membranes adhere to each other
They form gaps or “tunnels” that join the cytoplasm of two cells
Fuse the two plasma membranes into a single structure (heart)
3. Tight junctions – occur in cells that are joined by “collars” of tightly fused membrane (lining of intestines and other parts of the body, where it is important to control what gets past a sheet of cells)

9. Categories of Tissues
Epithelial Tissue – covering; lining of surfaces (epi- “over” or “outer”)
Connective – support; bone, ligaments, fat (connect)
Muscle – movement (contract)
Nervous – control; brain, nerves, spinal cord

10. Function of Epithelial Tissue
Protection
- Skin protects from sunlight & bacteria & physical damage
Absorption
- Lining of small intestine, absorbing nutrients into blood
Filtration
- Lining of kidney tubules filtering wastes from blood plasma

11. Secretion
- Different glands produce perspiration, oil, digestive enzymes and mucus
Sensory Perception
- Sensory nerve endings embedded in epithelial tissue connect the body with outside stimuli

12. Characteristics of Epithelial Tissue
Form continuous sheets (fit like tiles)
Apical Surface (free)
-surface that can be exposed to the air or to fluid
- sometimes has cytoplasmic projections such as cilia or microvilli

13. Basement Membrane
- Underside of all epithelial cells which anchors them to connective tissue
Avascular (a= without)
- lacks blood vessels
- Nourished by connective tissue
Regenerate & repair quickly

14. Classification – two criteria: shape of cells and the number of cell layers
Cell height (shape) – the shape of the nucleus corresponds to the cell shape
Squamous – flat and nuclei are usually broad and thin; horizontal longer than vertical
Cuboidal – horizontal and vertical equal; nuclei are spherical and centrally located

15. Columnar – vertical greater than horizontal; nuclei are usually in the lower portion of the cell near the basement membrane
Cell layers (cell arrangement)
Simple – single cell layer
Stratified – multiple layers

19. Simple Squamous Epithelium
Structure
- single layer of flattened cells – allows for diffusion and osmosis; sparse cytoplasm
Function
- Absorption , secretion, and filtration
- Not effective protection – single layer of cells
Location
- Walls of capillaries, air sacs in lungs (alveoli)
- Form serous membranes in body cavities

23. Simple Cuboidal Epithelium
Structure
- Single layer of cube shaped cells
Function
- Secretion, absorption, and transportation in glands, filtration in kidneys
Location
- Glands and ducts (pancreas & salivary), kidney tubules, covers ovaries

27. Simple Columnar Epithelium
Structure
- Elongated layer of cells with nuclei at same level, close packed cells
Function
- Absorption, Protection & Secretion
- When open to body cavities – called mucous membranes

28. Special Features
- Microvilli, bumpy extension of apical surface, increase surface area and absorption rate
- Goblet cells, single cell glands, produce protective mucus
- Cilia – moves secretions along surface
Location
- Linings of entire digestive tract- secretes digestive enzymes and absorbs nutrients

32. Pseudostratified Epithelium
Structure
- Single layer
- Irregularly shaped cells with nuclei at different levels – appear stratified, but aren’t
- all cells reach basement membrane but not all cells reach the free surface

33. Function
- Absorption and Secretion
- Goblet cells produce mucus
- Cilia (larger than microvilli) sweep mucus
Location
- Respiratory tract in which mucus traps dust particles & is moved upward by the cilia
- Reproductive tract – lines some of the tubes of the male tract where the cilia propels sperm from one region to another

36. Here, we have pathogens traveling down the pharynx trying to attack the surface cells. How can they be repelled???

37. The mucosal cells lining the trachea have released a flood of mucus, trapping the pathogens! Now what???

38. The cilia successfully sweep the pathogens up and away!

40. Stratified Squamous Epithelium
Structure
- Many layers (usually cubodial/columnar at bottom and squamous at top)
- cells far away from basement membrane die because it is difficult to receive oxygen and nutrients from underlying connective tissues
Function
- Protection
- Keratin (protein) is accumulated in older cells near the surface – waterproofs and toughens skin

41. Location
- Skin (keratinized), extends a short distance into every body opening that is continuous with the skin (mouth, pharynx, esophagus, anal canal and vagina)

45. Stratified Cuboidal Epithelium
Structure
- 2 to 3 layers; cube shaped
Function
- protection
Location
- largest ducts of sweat, mammary and salivary glands, male urethra

49. Stratified Columnar Epithelium
Structure
- multiple layers, column shaped cells
Function
- secretion and protection
Location
- largest ducts of salivary glands, uterus, parts of eye, anus, male urethra

54. Transitional Epithelium
Structure
- many layers
- very specialized – cells at base are cuboidal or columnar, at surface will vary
- change between stratified & simple as tissue is stretched out
- stretches in response to tension

55. Function
- allows stretching (change size)
Location
- urinary bladder

59. Covering and Lining Epithelia
Body membranes are thin sheets of tissue that cover the body, line body cavities, cover organs within the cavities, and line the cavities in hollow organs
Epithelial membranes – consists of epithelial tissue and connective tissues to which it is attached

60. 4 main types of Epithelial membranes
Mucous (Mucosae) – consist of epithelial tissue that is attached to an underlying loose connective tissue
- lines body cavities that open to the outside (digestive, respiratory, excretory, and reproductive tracts)
- secretes mucus for lubrication and protection

62. 2) Serous (Serosa) – lines body cavities that do not open directly to the outside, and they cover the organs located in those cavities - consists of a thin layer of loose connective tissue covered by a layer of simple squamous epithelium (mesothelium) 2 parts: parietal – lines cavity wall visceral – covers organs in cavity - covered by thin layer of serous fluid- lubricates the membrane and reduces friction and abrasion when organs move against one another or the cavity wall

64. 3) Cutaneous – covers body surfaces that are exposed to the external environment (skin) dry membrane 4) Endothelial- thin layer of cells that line the interior surface of blood vessels - lines entire circulatory system from the heart to the smallest capillary

66. Glands One or more cells that make and secrete a product
Secretion - protein in aqueous solution: hormones, acids, oils
Endocrine glands ; Endo = within
- no duct, release secretion into blood vessels
- often hormones
- thyroid, adrenal and pituitary glands

68. Exocrine glands; Exo = outside crine = secrete
- contain ducts, empty onto epithelial surface
- sweat, oil glands, salivary glands, mammary glands

69. Can be multicellular or unicellular.
Pancreas, stomach, sweat glands, salivary glands, mammary glands, sebaceous glands, etc.
Unicellular:
Goblet cells- single cells called goblet cells that produce mucous

70. Exocrine glands come in a wide variety of shapes:

71. Exocrine Secretion:
Merocrine- hormones released through cell membrane (sweat & salivary glands, mucous producing goblet cells)
Apocrine- part of cell containing hormones pinches off (mammary gland- usually associated with a hair follicle; arm pit, groin)
Holocrine- cell bursts to secrete products and must be replaced (sebaceous gland)