1. I. Histology – the study of tissues
A. Tissue – group of similar cells that work together to perform a certain function.
1. Cells in tissues have the same basic structures of all human cells – plasma membrane, nucleus, cytosol, organelles.

2. 2. Particular tissues vary in the amount of each type of organelle and in the size, shape, etc of the cells.
Pathologist – scientist who studies cells and tissues for abnormalities to help a physician make an accurate diagnosis.

3. II. Four major tissue types
A. epithelial
B. connective
C. nervous
D. muscular

4. Cell junctions - Connections between cells within a tissue
A. tight junctions – plasma membranes of the cells within the tissue are fused together.
1. prevents substances from passing between the cells
2. found in stomach, intestines, urinary bladder to prevent leaking
3. Diagram:

5. protein fibers connect the cells
B. desmosomes
protein fibers connect the cells
1. prevents separation of the cells while they perform their function
2. diagram

6. 1. found in muscles and some nerves 2. diagram:
C. gap junctions
– channels that connect one cell to another so they can communicate easily.
1. found in muscles and some nerves
2. diagram:

7. IV. Epithelial Tissue –also called epithelium (singular) or epithelia(plural)
A. 2 types:
1. covering and lining epithelium
a. outer covering of the skin
b. outer covering of some organs
c. lines the insides of respiratory, digestive, reproductive and urinary organs

8. a. makes up the secreting part of glands b. Ex. sweat glands
2. glandular epithelium
a. makes up the secreting part of glands
b. Ex. sweat glands

9. B. General features of epithelial tissue
1. cells are closely packed with little extracellular material between them
2. cells are arranged in continuous sheets
3. avascular – no blood vessels. Cells get necessary materials from nearby connective tissue using diffusion.

10. 4. has a nerve supply
5. easily able to renew itself by cell division
6. surfaces of epithelial cells
Diagram:

11. Epithelial cell surfaces
a. apical surface – toward a body cavity, inside of an organ or the outside of the body.
b. lateral surface – toward adjacent cells on either side

12. More Epithelial cell surfaces
c. basal surface – bottom which attaches to a basement membrane
d. basement membrane – fibers that connect epithelium to connective tissue below it.

13. C. Four basic shapes of covering and lining epithelium
1. squamous – flat
a. allow rapid passage of materials through them
b. found lining the inside of the lungs and kidneys
c. found in layers on the surface of the skin

14. Another shape of epithelial tissue
2. cuboidal – square
a. function in secretion of mucus, sweat, enzymes
b. function in absorption of fluids and digested food molecules
c. may have microvilli on their apical surface

15. Another shape of epithelial tissue
3. columnar – tall rectangles
a. function in secretion and absorption
b. may have microvilli on their apical surface
c. may have cilia on their apical surface

16. A final shape of epithelial tissue
4. transitional – change shape between cuboidal and flat

17. 1. simple – a single layer of cells
D. Layers of epithelium
1. simple – a single layer of cells
2. stratified – 2 or more layers of cells

18. E. Keratin
a tough protein that protects skin from bacteria, heat and chemicals

19. F. Types of simple epithelium
1. simple squamous epithelium – 1 layer of flat cells (See p. 77)
a. found lining the inside of lungs, heart, blood vessels and kidneys
b. used for diffusion, osmosis and some secretion

20. More types of simple epithelium
2. simple cuboidal epithelium – 1 layer of square cells (See p. 77)
a. lines kidney tubules and surface of the ovary
b. secretion and absorption

21. More types of simple epithelium
simple columnar epithelium – 1 layer of tall, thin cells (See p. 78)
a. nonciliated – has no cilia
1. has absorptive cells with microvilli
2. has goblet cells which secrete mucus
3. lines digestive tract ducts

22. More types of simple epithelium
b. ciliated – has cilia
1. also has goblet cells
2. lines the inside of the respiratory tract and fallopian tubes
3. the cilia all beat together to move substances along the tubes they line

23. a. keratinized types form the outer skin layers
4. stratified squamous epithelium
– several layers of flat cells (See p. 79)
a. keratinized types form the outer skin layers
b. nonkeratinized types line wet surfaces such as the inside of the mouth
c. protective
d. as upper layers are lost, the basal layer produces more cells by cell division

24. 5. stratified cuboidal epithelium –
_several_ layers of cube-shaped cells (See p. 79)
a. found in the _ducts__ (tubes) of sweat glands and glands in the esophagus
b. protection and some _secretion_ and absorption

25. 6. stratified columnar epithelium –
several layers of column-shaped cells (p. 80)
a. lines part of the urethra (tube out of the bladder), large ducts of esophageal glands
b. protection and secretion

26. G. Glandular epithelium
1. A gland secretes substances into ducts, onto a surface or into the blood
2. 2 types of glands
a. endocrine gland – secretes hormones into the blood without a duct
Ex. pituitary gland, thyroid gland, adrenal gland

27. 2nd kind of glandular epithelium
b. exocrine gland – secretes its product into a duct, at the skin surface or into an organ.
Ex. sweat glands, salivary glands, glands lining the inside of the stomach

29. 2. protects and insulates body organs
V. Connective tissue
A. Functions of connective tissue 1. binds together, supports and strengthens other body tissues
2. protects and insulates body organs
3. compartmentalizes structures such as muscles

30. More connective tissue functions
5. major transport tissue (blood is connective tissue)
6. major energy storage tissue (fat is connective tissue)
7. main site of immune responses (white blood cells & lymph are connective)

31. B. General features of connective tissues
1. Composed of 2 parts:
a. cells
1. fibroblasts – large, flat, branching cells which move and secrete fibers and the ground substance of the matrix.
2. macrophages – irregular cells with branching projections that can
engulf bacteria and cellular debris by phagocytosis

32. More types of connective tissue cells
3. mast cells – produce histamine to dilate small blood vessels when the body is injured.
4. adipocytes – fat cells that store triglycerides

33. 2nd Connective tissue part
b. matrix – the materials between the cells.
Made of:
1. ground substance – water, proteins and polysaccharides
2. fibers – strands of proteins

34. 3 kinds of fibers in the matrix
a. collagen fibers – strong, thickest fibers. Collagen is their protein.
b. elastic fibers – strong, but stretchy
c. reticular fibers – branching, thinnest fibers

35. More Connective tissue features
2. Usually not found on external or internal surfaces
3. Usually has a nerve supply
4. Usually vascular – has a blood supply

36. C. Six types of connective tissue -
Loose,
Dense,
Cartilage,
Bone,
Blood
and Lymph

37. 1. Loose connective tissue (3 types)
a. areolar connective tissue –
forms the subcutaneous layer (connects skin to underlying tissues and organs) (See p. 85)
1. contains all four cell types (fibroblasts, macrophages, mast cells and adipocytes) and all three fiber types (collagen, elastic and reticular)
2. for strength, elasticity and support

38. 2nd type of loose connective tissue
b. adipose tissue – contains adipocytes which fill with a large triglyceride droplet. (See p. 85)
1. the triglyceride droplet pushes the cytoplasm and nucleus off to 1 side
2. for insulation and energy storage
3. formation of more adipose tissue results in more blood vessels forming which can cause high blood pressure in obese people.

39. 3rd type of loose connective tissue
c. reticular connective tissue – network of reticular fibers and reticular cells (p.86)
1. supporting framework of the liver, lymph nodes, spleen and red bone marrow
2. forms the basement membrane which other tissues attach to
3. filters and removes worn out blood cells in the spleen and microbes (bacteria, protists and viruses)in the lymph nodes

40. 2nd of the six types of connective tissue
2. Dense connective tissue
– Contains more and thicker fibers than loose connective tissue

41. 3 types of dense connective tissue:
a. dense regular connective tissue – collagen fibers are arranged in bundles
with fibroblasts between the rows (See p. 86)
1. forms tendons (attaches muscle to bone)
and most ligaments (attaches bone to bone)
2. used in areas that pull in one direction

42. 2nd type of dense connective tissue
b. dense irregular connective tissue – randomly arranged collagen fibers with a few fibroblasts (See p. 87)
1. forms fasciae (tissue beneath the skin and around muscles and other organs)
2. pericardium – membrane around the heart
3. periosteum – membrane around bone
4. heart valves

43. 3rd type of dense connective tissue
c. elastic connective tissue – branching elastic fibers with fibroblasts (p. 87)
1. found in tissues that stretch such as lung tissue, artery walls, trachea and bronchial tubes, ligaments between vertebrae

44. The other 4 types of connective tissue:
3. Cartilage – found between the ends of bones to cushion them
4. Bone - a living tissue used to give shape and support to the body
5. Blood – used for transporting gases, nutrients and wastes
6. Lymph – a liquid which is produced from plasma that squeezes out of the capillaries and is returned to the blood after being filtered to remove invading microbes in the lymph nodes. Involved in the immune system.