Bell ringer

1. Bell ringer • What is the study of cells? • What is the study of tissues?

2. Chapter 3: Fundamental Cells and Tissues

3. Objectives – Lesson 1 • TSWBAT to define histology. • TSWBAT to identify the four basic tissue types. • TSWBAT to identify five important characteristics of epithelial tissue. • TSWBAT to identify four essential functions of epithelial tissue.

4. Cells In the late 1600’s British born Robert Hooke coined the term "cell" to describe the basic unit of life. • Where did the term cell come from? • In 1665 Robert Hooke inspected thin slices of cork and found that they consisted of millions of small, “irregular units” • He used the term cell because the small, bare spaces reminded him of cells in a prison

5. Cell Basics • Cells are the building blocks of all plants and animals • All cells come from the division of preexisting cells • Cells are the smallest units that perform all vital physiological functions • Each cell maintains homeostasis at the cellular level

6. Cell Basics continued Living cells are about 60 % H20 All body cells are constantly bathed in a dilute saltwater solution called interstitial fluid (18 pints). All exchanges between cells and blood are made through this fluid

7. Cell Facts • The human body contains trillions of cells (200 types of cells) • The average cells is just 0.02mm across • The largest cell in the body is an egg cell (0.15mm) • The longest cells are the nerve cells supplying your legs (some measure as much as 4ft in length) • Five million of your body cells die every second

8. Tissues Tissues - Groups of cells similar in structure and function • The four types of tissues: • Epithelial • Connective • Muscle • Nerve (Neural)

9. Tissues • Tissues can be distinguished from each other by variations in cell size, shape, organization, and function • Epithelial, connective, muscle, and nervous tissues associate, assemble, and interact to form organs that have specialized functions

10. Epithelial Tissue Epithelium – A sheet of cells that covers a body surface or lines a body cavity. Occurs in the body in two ways: 1. Epithelia – layers of cells that cover internal or external surfaces - Forms the outer layer of the skin - Lines the open cavities of the reproductive, cardiovascular, nervous, digestive, urinary and respiratory systems and covers the walls and organs (line all passageways that communicate with the outside world) 2.Glandular Epithelium - Forms the glands of the body (provide fluid secretions)

11. Epithelial Tissue Functions • Protection – protect exposed and internal surfaces from abrasion, dehydration, and destruction by foreign agents • Permeability – any substance that enters or leaves your body must cross an epithelium (provides selective absorption) • Sensation – provide information about the external and internal environments (example - sense smell) • Secretion – gland cells releases a substance (example – mucus)

12. Special Characteristics of Epithelium • Cells fit closely together to form continuous sheets (single/multiple layers) • Membranes always have one free surface or edge (exposed to body cavity, exterior of the body or lining an internal organ) • Lowest surface (basal surface) of epithelium rests on a basement membrane (a thin nonliving layer that anchors epithelium to underlying connective tissue) • Epithelial tissues have no blood supply (avascular) of their own (lack blood vessels); must obtain nutrients by diffusion or absorption from nearby tissues • If well nourished, epithelial cells regenerate themselves (high rate of mitosis)

13. Mitosis • Process where cells divide to produce new cells • Through a sequence of steps, the replicated genetic material in a parent cell is equally distributed to two daughter cells • Equal division of material in the nucleus, followed by division of the cell body (nuclear cell division) • Epithelial cells have a high rate of mitosis to allow for frequent repair

14. Check point • Define histology. • Identify the four major types of tissues in the body. • What two ways does epithelium occur in the body?

15. Classification of Epithelia • There are many different specialized types of epithelia • Organized into categories based on: • Cell shape • The number of cell layers between the basement membrane and the exposed surface of the epithelium

16. Classification of Epithelia Squamous(skwa’mus) Flattened and scalelike (attach like tiles) Cubodial (ku-boi’dahl) “Cube” like, as tall as they are wide. Columnar Tall and column shaped. Figure 4.1b

17. Classification of Epithelial Tissue Number of cell layers: Simple = one layer of cells covers the basement membrane • Thin/Fragile • Located in protected areas in the body (ventral body cavities, heart chambers and blood vessels). Why? • Regions in which secretion or absorption occurs (lining of the intestines, lungs) • Stratified = Multilayered (several layers cover basement membrane) • Located in areas that are exposed to stresses (mouth, skin) Why?

18. Classification of Epithelial Tissue Each epithelium is given two names. • The first name indicates the number of cell layers present • The second name describes the shape of its cells • Followed by epithelium or epithelial tissue Example : • Simple (1 layer) • Squamous (Flat cell shape) • Epithelium

19. Epithelia: Simple Squamous Figure 4.2a

20. Epithelia: Simple Cuboidal • Single layer of cubelike cells with large, spherical central nuclei • Function in secretion and absorption • Present in kidney tubules, ducts and secretory portions of small glands, and ovary surface Figure 4.2b

21. Epithelia: Simple Columnar Figure 4.2c

22. Pseudostratified Columnar • Includes several types of cells with varying shapes and functions • The distances between the cell nuclei and the exposed surface vary, so the epithelium appears to be layered (stratified) • It is not truly stratified because every epithelial cell contacts the basement membrane • Typically possess cilia (slender organelles that extends above the free surface of an epithelial cell and undergoes movement)

23. Epithelia: Pseudostratified Columnar • Single layer of cells with different heights; some do not reach the free surface • Nuclei are seen at different layers • Function in secretion and propulsion of mucus • Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated) Figure 4.2d

24. Epithelia: Stratified Squamous – Most Common • Thick membrane composed of several layers of cells • Function in protection of underlying areas subjected to abrasion • Forms the external part of the skin’s epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells) Figure 4.2e

25. Epithelia: Stratified Cuboidal and Columnar Stratified cuboidal • Quite rare in the body • Found in some sweat and mammary glands • Typically two cell layers thick Stratified columnar • Limited distribution in the body • Found in the pharynx, male urethra, and lining of some glandular ducts • Also occurs at transition areas between two other types of epithelia

26. Transitional Epithelium • Unusual stratified epithelium because it tolerates repeated cycles of stretching and recoiling without damage • It is called transitional because the appearance of the epithelium changes as stretching occurs

27. Epithelia: Transitional • Several cell layers, basal cells are cuboidal, surface cells are dome shaped • Stretches to permit the distension of the urinary bladder • Lines the urinary bladder, ureters, and part of the urethra Figure 4.2f

28. Epithelia: Glandular Gland - One or more cells that makes and secretes a particular product (secretion). Classified by: • Site of product release endocrine (internally secreting) exocrine (externally secreting) • Relative number of cells forming the gland unicellular (one-celled) multicellular (many-celled)

29. Endocrine Glands • Ductless glands that produce hormones (secrete directly into the bloodstream) • Hormones are regulatory chemicals that travel to organs • Each hormone prompts its target organ to respond in some characteristic way • Examples: Testes – Testosterone, Ovaries – Estrogen, Pancreas – Insulin, Adrenal Glands - Adrenaline

30. Exocrine Glands • More numerous than endocrine glands • Secrete their products onto body surfaces (skin) or into body cavities • Examples include mucus, sweat, oil, salivary glands, the liver (secretes bile), the pancreas (synthesizes digestive enzymes) • Unicellular & Multicellular

31. Connective Tissues

32. Connective Tissue • Found everywhere in the body; most abundant type of tissue by weightand the most widely distributed of the primary tissues (its amount in particular organs varies) • The dense layer of the basement membrane of all epithelial tissues is created by connective tissue • Connective tissue connects the epithelium to the rest of the body

33. Functions of Connective Tissue • Establish a framework and support • Transport fluids and materials • Protect organs • Produce blood cells • Support, surround, bind, and interconnect other types of tissue • Store energy reserves (fat) • Protect against infections

34. Connective Tissue Elements Three Main Elements: 1. Ground substance 2. Cells 3. Fibers

35. Structural Elements of Connective Tissue Ground substance • Unstructured material that fills the space between cells and contains the fibers • Composed of interstitial fluid and proteins • Holds large amounts of fluid • Functions as a medium through which nutrients and other substances can diffuse between the blood capillaries and the cells

36. Structural Elements of connective tissue Cells – each major class of CT has a fundamental cell type • Most common type is fibroblasts (produce fibers) • fibroblasts (connective tissue proper), chondroblasts (cartilage), osteoblasts (bone), hematopoietic stem cells (produces blood cells), and accessory cells (mast cells = cluster along blood vessels that detect foreign microorganisms; macrophages = “eat” foreign materials)

37. Structural Elements of connective tissue Fibers – provide support • Collagen – strongest and most abundant • Elastic – long and thin that form branching networks; stretch and recoil • Reticular – short and fine; branch extensively forming delicate networks

38. Classification of Connective Tissues • Classified on the basis of their physical properties Three general categories: • Connective tissue proper • Loose connective tissues – aerolar, adipose, and reticular • Dense connective tissues – dense regular, dense irregular, and elastic 2. Fluid connective tissues – blood and lymph 3. Supporting connective tissues • Cartilage – hyaline, elastic, and fibrocartilage • Bone

39. Connective Tissue Prosper • Sub-divisions: 1. Loose connective tissues (areolar, adipose, and reticular) 2. Dense connective tissues (dense regular, dense irregular, and elastic)

40. Connective Tissue Proper: Loose Areolar connective tissue • Most widely distributed connective tissue • Supports and binds other tissues • Holds body fluids • Defends against infection • Stores nutrients • Functions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and in their proper positions.

41. Connective Tissue Proper: Loose - Areolar Figure 4.8b

42. Connective Tissue Proper: Loose Adipose connective tissue • 90% of tissue’s mass is made of fat cells • Cells are packed closely together • Richly vascularized (high metabolic activity) • Abundant (approx. 18% of an average person’s body weight) • Acts as a shock absorber • Provides insulation • Stores energy • Prevents heat loss from body

43. Connective Tissue Proper: Loose - Adipose Figure 4.8c

44. Connective Tissue Proper: Loose Reticular connective tissue • The only fibers in its matrix are reticular fibers (reticular cells are scattered along) • Limited to certain sites • Forms a stroma (internal framework) that supports many blood cells in lymph nodes, spleen, and bone marrow

45. Connective Tissue Proper: Loose - Reticular Figure 4.8d

46. Connective Tissue Proper: Dense Dense Regular: • Parallel collagen fibers with a few elastic fibers • Provides great resistance to tension • Attaches muscles to bone or to other muscles, and bone to bone Tendons – attach skeletal muscles to bone Ligaments – connect bones to bones at joints Aponeuroses – sheet like tendons; attach muscles to other muscles or bones

47. Connective Tissue Proper: Dense Regular Figure 4.8e

48. Connective Tissue Proper: Dense • Dense Irregular: • Irregularly arranged collagen fibers with some elastic fibers • Forms sheets in body areas where tension is exerted from many different directions • Found in the dermis (skin), digestive tract, fibrous joint capsules, and the fibrous coverings that surround some organs (kidneys, bones, cartilages, muscles, and nerves)

49. Connective Tissue Proper: Dense Irregular Connective Tissue Proper: Dense Irregular Figure 4.8f

50. Connective Tissue Proper: Dense Elastic: • High proportion of elastic fibers • Allows recoil of tissue following stretching, maintains blood flow through arteries and recoil of lungs following inspiration • Found in walls of large arteries, walls of bronchial tubes and some ligaments of the vertebral column