Principles of Biology

1. Principles of Biology By Frank H. Osborne, Ph. D. Cells and Tissues

2. Cells and Tissues Living things exhibit structure and organization. The basic unit of structure and function is the cell. Cells are organized into units containing similar cells. These are called tissues. Different types of tissues are found in an organ. Organs are organized into units of structure called organ systems.

3. Cells and Tissues A living creature, such as a human, is an organism containing various organ systems with their component organs.

4. PLANT TISSUES I. Meristematic tissues A. Shoot tip B. Root tip C. Cambium II. Permanent tissues A. Surface tissues 1. Epidermis 2. Periderm

5. PLANT TISSUES B. Fundamental tissues 1. Parenchyma 2. Collenchyma 3. Sclerenchyma 4. Endodermis C. Vascular tissues 1. Xylem 2. Phloem

6. PLANT TISSUES

7. Meristematic Tissues Meristematic tissues have embryonic, undifferentiated cells. Undifferentiated means that these cells have not changed into other cells yet. When they do change, the process is called differentiation because the cells become different. The shoot tip meristem is found on the end of each branch. It is protected by a bud. This meristem produces all the tissues in the branch.

8. The Shoot Tip Meristem

9. The Root Tip Meristem

10. Meristematic Tissues The root tip meristem is found on the tip of each root. It divides and produces all the cells found in the root. The cambium is found between the xylem (wood) and phloem (bark) of the tree. It is active only during the growing season, producing new xylem and phloem cells. This annual growth forms in rings.

11. Permanent Tissues Epidermis contains living cells and is found on the surfaces of young stems and leaves. The lower epidermis of leaves contains specialized occlusive cells called guard cells that surround openings in the leaves called stomates. The stomates permit exchange of gases (carbon dioxide and oxygen) with the air outside of the leaf. The guard cells prevent loss of water.

12. Onion skin epidermis Low Power (100x) High Power (400x)

13. Permanent Tissues Periderm contains non-living cells that have thick secondary walls. The walls are made waterproof with a material called suberin. Periderm tissue replaces epidermis on older stems of the plant. It prevents loss of water.

14. Periderm

15. Fundamental Tissues Parenchyma contains living cells that are capable of cell division. It is the least specialized of the plant tissues. These cells have thin primary walls. Parenchyma is used as a filler tissue in such plant structures as corn stalks.

16. Fundamental Tissues Collenchyma cells are usually alive. They have cell wall material that is deposited in the corners giving them a characteristic microscopic appearance. It serves as a support tissue in certain types of stems.

17. Parenchyma and Collenchyma

18. Fundamental Tissues Schlerenchyma cells are dead. They have thick secondary walls. Fibers are very long with thick walls and very small lumens. They provide vertical support structure in stems. Sclereids are also dead. They have thick walls with very tiny interior spaces. They are parts of such plant structures as peach pits.

19. Sclerenchyma cells Sclerenchyma fibers Sclereids

20. Fundamental Tissues Endodermis is a layer of living cells found in the root. It has a waterproofing layer known as the Casparian strip containing lignin and suberin. The plant uses the endodermis to regulate what materials enter the plant and are transported up to the stem and leaves.

21. Endodermis

22. Endodermis

23. Vascular Tissues Vascular tissues are specialized transport tissues. There are two kinds: xylem and phloem. Xylem cells are dead. Xylem transports water and nutrients upward in the plant. Phloem has living cells. Phloem cells come in pairs, the sieve tube and the companion cell. The sieve tube transports conducts materials both upwards and downwards in the plant. Phloem is the major component of the bark of the tree.

24. Xylem

25. Phloem

26. ANIMAL TISSUES I. Epithelium A. Simple epithelium 1. Simple squamous epithelium 2. Simple cuboidal epithelium 3. Simple columnar epithelium B. Stratified epithelium 1. Stratified squamous epithelium 2. Stratified cuboidal epithelium 3. Stratified columnar epithelium

27. ANIMAL TISSUES II. Connective tissue A. Tissues that connect body structures 1. Loose connective tissue (areolar) 2. Dense connective tissue 3. Adipose (fat) tissue 4. Cartilage B. Bone C. Vascular tissue 1. Blood 2. Lymph

28. ANIMAL TISSUES III. Muscle A. Smooth muscle B. Striated muscle C. Cardiac muscle IV. Nerve

29. Simple Epithelium Simple epithelium always contains a single layer of cells attached to a membrane. As this membrane is underneath the cells, it is called the basement membrane. There are three kinds of epithelium that differ in their shapes.

30. Simple Epithelium Simple Squamous Epithelium "Squamous" means flat. Simple squamous epithelium contains a single layer of flat cells attached to a basement membrane. An example is peritoneum, the tissue that surrounds and suspends the digestive organs in the abdominal cavity.

31. Simple Epithelium Simple Cuboidal Epithelium "Cuboidal" means having the shape of a cube. This tissue contains a single layer of cube-shaped cells on a basement membrane. An example of this type of tissue is the lining of the collecting duct in the kidney.

32. Simple Epithelium Simple Columnar Epithelium "Columnar" means that the cells are tall like columns. This tissue contains a single layer of tall cells on a basement membrane. An example of this type of tissue is the intestinal lining.

33. Stratified Epithelium "Stratified" means that the cells of the tissues are found in layers. All three types of stratified epithelium start out as several layers of cuboidal cells on a basement membrane. The other layers determine which type of tissue it is.

34. Stratified Epithelium Stratified Squamous Epithelium Stratified squamous epithelium contain several layers of cuboidal cells that flatten as you proceed away. An example is skin.

35. Stratified Epithelium Stratified Cuboidal Epithelium In stratified cuboidal epithelium, the cells in all layers of the tissue are cuboidal. An example is the lining of the ducts of the sweat glands.

36. Stratified Epithelium Stratified Columnar Epithelium In stratified columnar epithelium, all layers are cuboidal except for the top layer which contains tall cells. An example is the lining of the ducts of the mammary glands.

37. Connective Tissue Connective implies holding things together or joining things. Thus we expect to find tendons, ligaments and cartilage classified as connective tissue. In addition, the category of connective tissue also contains body-wide tissues such as bone, blood and lymph. In most cases, the cells that make up the tissue are surrounded by some kind of matrix or material characteristic of the tissue.

38. Connective Tissue Areolar (Loose) Connective Tissue Loose connective tissue contains cells surrounded by a matrix of collagenous fibers, elastic fibers and lymph. Collagenous fibers are made of collagen, a type of structural body protein. Lymph is also called tissue fluid. It is a liquid that is found in between the different parts of the body in the spaces known as connective tissue spaces.

39. Connective Tissue Elastic fiber Collagenous fiber Fat cell Lymphoblast Lymph Areolar (Loose) Connective Tissue

40. Loose Connective Tissue

41. Connective Tissue Dense Connective Tissue Dense connective tissue is made of collagenous fibers. It is found in the dermis of the skin, tendons and ligaments. A tendon connects a muscle to a bone while a ligament connects one bone to another bone.

42. Dense Connective Tissue

43. Connective Tissue Adipose Tissue (= Body Fat) Adipose tissue is made of fat cells. Each cell has a thin ring of cytoplasm that surrounds a large vacuole containing a fat droplet.

44. Connective Tissue

45. Connective Tissue Cartilage There are three kinds of cartilage. Each consists of cells surrounded by a matrix of small fibers. Yellow elastic cartilage is found in the arteries and between the rungs of the trachea. Hyaline cartilage forms the ridge of the nose and the rungs of the trachea. Elastic cartilage is found in the external ear, the epiglottis and the Eustachian tube.

46. Elastic Cartilage

47. Connective Tissue Cartilage Hyaline cartilage forms the ridge of the nose and the rungs of the trachea.

48. Connective Tissue Bone Bone cells are surrounded by a matrix of calcium phosphate. There are tunnels in the bone called Haversian canals that contain the blood supply. Bone has the most mineral matter.

49. Connective Tissue Bone There are two types of bone called spongy bone and compact bone. The ends of the long bones are made of spongy bone. "Spongy" means having the appearance of a sponge. Compact bone does not have spaces in it that give it a spongy appearance. The long parts of the long bones are made of compact bone tissue.