1. CHAPTER 4
TISSUES

2. TYPES OF TISSUES
TISSUE- groups of cells having similar structure and function
RECALL: HISTOLOGY- study of tissues
There are 4 primary kinds of tissues:
EPITHELIAL
CONNECTIVE
NEURAL
MUSCLE
- tissues combine to form organs of the body

3. EPITHELIAL TISSUE

4. EPITHELIAL TISSUE Epithelial tissue includes EPITHELIA and GLANDS
EPITHELIA (UM)- name given to those tissues that cover surfaces and line internal structures and cavities of the body
GLANDS- made up of secreting cells derived from epithelia

5. CHARACTERISTICS - cells are close together
- have a free surface exposed to environment or some internal passageway
- attached to underlying connective tissue by a BASEMENT MEMBRANE
- are AVASCULAR, meaning having no blood vessels; nutrients must be obtained from deeper tissues or exposed surfaces

6. Epithelia cover external and internal body surfaces:
- skin
- lining of digestive, respiratory, reproductive, and urinary tracts
* Separates deep tissues from external environment
Epithelia also line internal cavities and passageways:

7. - chest cavity
- fluid-filled chambers in brain, eye, and inner ear
- inner surfaces of blood vessels and heart

8. FUNCTIONS OF EPITHELIA
Four essential functions:
1. Provide physical protection- protects exposed surfaces from abrasion, dehydration, and destruction by chemical or biological agents
2. Control permeability- controls substances that enter and leave the body
3. Provide sensation- detect changes in the environment and relay info. to the nervous system

9. 4. Produce specialized secretions- cells that produce secretions are called GLAND CELLS
- EXOCRINE secretions are discharged onto the surface of the skin or other epithelial surface (Ex: perspiration)
- ENDOCRINE secretions are released into the surrounding tissue and blood (hormones)

10. INTERCELLULAR CONNECTIONS
To be an part of an effective barrier, epithelial cells must remain firmly attached to one another
- cells are attached by CELL JUNCTIONS
3 TYPES OF JUNCTIONS:
TIGHT JUNCTIONS- cell membranes are fused together
GAP JUNCTIONS- proteins in the membranes bind and create channels between the 2 cells

11. DESMOSOMES- cells are attached by protein filaments

12. SURFACE OF EPITHELIA Many epithelia have MICROVILLI
- small, finger-shaped projections of the cell membrane
- increases the surface area of the cell
Some epithelial cells have CILIA
- long, finger-shaped extensions of the cell membrane
- beat simultaneously to move materials across the epithelial surface

13. BASEMENT MEMBRANE
Epithelial cells also must remained attached to the rest of the body
- performed by the BASEMENT MEMBRANE- lies between the epithelium and underlying connective tissues
- consists of a network of protein fibers (no cells)
- basement provides strength, resists distortion, and provides a barrier

14. CLASSIFYING EPITHELIA
Epithelia are classified by the number of cell layers, and the shape of the exposed cells
2 TYPES OF LAYERING:
- Simple
- Stratified
3 CELL SHAPES:
- Squamous
- Cuboidal
- Columnar

15. LAYERS
SIMPLE EPITHELIUM- single layer of cells covering the basement membrane
- thin
- only found in protected areas in the body
- body cavities, interior of heart and blood vessels
STRATIFIED EPITHELIUM- several layers of cells above basement membrane

16. - found in areas subject to mechanical or chemical stresses
- surface of skin, linings of mouth and anus

17. CELL SHAPE Again, there are 3 basic cell shapes in the epithelium:
1. SQUAMOUS- cells are thin and flat; cells look like fried eggs (due to nuclei) laid side by side
2. CUBOIDAL- cells appear square; nuclei lie near the center of each cell and form a neat row
3. COLUMNAR- also square, but taller and more slender; nuclei crowded into narrow band close to basement membrane

18. SIMPLE SQUAMOUS EPITHELIA
- found in protected regions where absorption takes place or where a slick, slippery surface reduces friction
- linings of body cavities; lining of blood vessels and heart

19. SIMPLE CUBOIDAL EPITHELIA
- provides limited protection and occurs in regions where secretion or absorption takes place
- secrete enzymes and buffers in the pancreas; line portions of kidneys involved in production of urine

20. SIMPLE COLUMNAR EPITHELIA
- provides some protection and may also occur in areas of absorption or secretion
- line the stomach, intestinal tract, and many excretory ducts

21. PSEUDOSTRATIFIED EPITHELIA
- columnar epithelia that appears layered because nuclei are situated at varying distances from the surface, but is not actually layered
- typically has cilia
- lines nasal cavity, trachea, bronchi, portions of male reproductive tract

22. STRATIFIED SQUAMOUS EPITHELIA
- found where mechanical stresses are severe
- surface of skin, lining of mouth, tongue, esophagus, and anus

23. CONNECTIVE TISSUE

24. CONNECTIVE TISSUE - are the most diverse tissues of the body
All have 3 basic components:
1. Specialized cells
2. Protein fibers
3. Ground substance- a fluid that varies in consistency
- the protein fibers and ground substance make up the MATRIX that surrounds the cells

25. - connective tissues are made up mostly of this matrix
- never exposed to outside environment
FUNCTIONS:
- Support and protection
- Transport of materials
- Storage of energy reserves- fats
- Defense of the body- production of antibodies

26. CLASSIFYING CONNECTIVE TISSUES
There are 3 classes of connective tissue based on the physical properties of their matrix:
1. CONNECTIVE TISSUE PROPER- connective tissues with many types of cells and fibers surrounded by a syrupy ground substance
- tissues underlying the skin, fatty tissue, tendons, and ligaments

27. 2. FLUID CONNECTIVE TISSUES- have distinctive population of cells suspended in a watery ground substance containing dissolved proteins
- blood and lymph
3. SUPPORTING CONNECTIVE TISSUES- cartilage and bone
- less diverse cell population, dense matrix

28. CONNECTIVE TISSUE PROPER
CELL TYPES:
FIBROBLASTS- most abundant; produce and maintain connective tissue fibers and the ground substance
MACROPHAGES- engulf damaged cells or pathogens
FAT CELLS- adipose cells; number varies from one connective tissue to another
MAST CELLS- contain chemicals that are released in times of defense

29. - WHITE BLOOD CELLS- produce ANTIBODIES when tissue is damaged
3 TYPES OF FIBERS IN CONNECTIVE TISSUE:
1. COLLAGEN FIBERS- long, straight, unbranched; most common; strong; flexible
2. ELASTIC FIBERS- contain protein elastin; branched and wavy; after stretching will return to original length

30. 3. RETICULAR FIBERS- least common; thinner than collagen; form branching, interwoven network in organs
GROUND SUBSTANCE
- fills space between cells and surrounds connective tissue fibers
- normally clear, colorless, similar in consistency to maple syrup

31. CONNECTIVE TISSUE PROPER: LOOSE CONNECTIVE TISSUE
- least specialized connective tissue in body
- contains all cells and fibers in connective tissue proper
- forms a layer that separates the skin from underlying muscles
- provides padding

32. CONNECTIVE TISSUE PROPER: ADIPOSE TISSUE
- FAT
- loose connective tissue containing large numbers of fat cells
- loose connective tissue becomes adipose tissue when it is dominated by FAT CELLS
- more padding; shock absorption; insulation; energy storage
- skin of sides, buttocks; fills sockets behind eyes

33. CONNECTIVE TISSUE PROPER: DENSE CONNECTIVE TISSUE
- consists mostly of collagen fibers
TENDONS- cords of dense connective tissue that attach skeletal muscles to bones
LIGAMENTS- bundles of fibers that connect one bone to another
- contain elastic fibers and collagen fibers (stretchy)

34. FLUID CONNECTIVE TISSUE: BLOOD AND LYMPH
BLOOD and LYMPH contain distinct collections of cells in a fluid matrix
- RED BLOOD CELLS- account for more than ½ the volume of blood; transport oxygen
- PLASMA- watery matrix of blood
- WHITE BLOOD CELLS- important components of immune system
- PLATELETS- cell fragments that function in blood clotting

35. SUPPORTING CONNECTIVE TISSUE: CARTILAGE AND BONE
- provide strong framework that supports the rest of the body
CARTILAGE
- firm gel containing embedded fibers
- only cells found within the matrix are CHONDROCYTES, which live in small pockets called lacunae
- cartilage is avascular

36. SUPPORTING CONNECTIVE TISSUE: CARTILAGE
There are 3 major types of cartilage:
1. HYALINE CARTILAGE- most common
- tough and somewhat flexible
- connects ribs to sternum, covers surfaces of bones within joints
2. ELASTIC CARTILAGE- contains numerous elastic fibers that make it very flexible and resilient
- outer ear, epiglottis (covering of larynx)

37. 3. FIBROCARTILAGE- has little ground substance; dominated by collagen fibers
- extremely durable and tough
- between vertebrae of spinal column- resist compression, absorb shock

38. SUPPORTING CONNECTIVE TISSUE: BONE
- also called OSSEOUS TISSUE
- volume of ground substance compared to cartilage is very small
- matrix consists mainly of hard calcium compounds and flexible collagen fibers
- lacunae within the matrix contain bone cells, called OSTEOCYTES
- each bone is surrounded by a PERIOSTEUM- covering made of fibrous and cellular layers

39. Bone is constantly being remodeled throughout life
- complete repairs can be made even after severe damage

40. MUSCLE TISSUE

41. MUSCLE TISSUE Muscle tissue is specialized for contraction
- muscle cell contraction involves interactions between filaments of MYOSIN and ACTIN, which are proteins found in the cytoskeletons of cells
There are 3 main types of muscle tissue:
1. Skeletal
2. Cardiac
3. Smooth

42. MUSCLE TISSUE: SKELETAL MUSCLE TISSUE
- contains very large, multinucleated cells
- skeletal muscles are long and slender, so are usually called MUSCLE FIBERS
- these fibers are not capable of dividing, but new ones are produced through the division of stem cells in muscle tissue  some repair is possible after an injury

43. MUSCLE TISSUE: SKELETAL MUSCLE TISSUE
- because of how actin and myosin filaments are arranged, skeletal muscle appears to have a series of bands called STRIATIONS
- skeletal muscle is described as STRIATED VOLUNTARY MUSCLE because the nervous system provides voluntary control over its activities

44. MUSCLE TISSUE: CARDIAC MUSCLE TISSUE
- found only in the heart
- cells are much smaller than skeletal muscle fibers, and each cell usually has a single nucleus
- also have striations
- cardiac muscle cells are interconnected at INTERCALATED DISCS, special attachment sites that have gap junctions and desmosomes

45. - cells of cardiac muscle cannot divide; tissue cannot regenerate
- cardiac muscle cells do not rely on nerve activity to start a contraction; called STRIATED INVOLUNTARY MUSCLE

46. MUSCLE TISSUE: SMOOTH MUSCLE TISSUE
- found in the walls of blood vessels, around hollow organs (urinary bladder), in layers around respiratory, circulatory, digestive, and reproductive tracts
- cells are small and slender, tapering to a point at each end; each has one nucleus
- actin and myosin filaments are scattered, so there are no striations
- cells can divide, so smooth muscle can regenerate after an injury

47. - nervous system does not provide voluntary control, so smooth muscle is known as NONSTRIATED INVOLUNTARY MUSCLE

48. NEURAL TISSUE

49. Neural Tissue
- also known as nerve tissue; is specialized for the conduction of electrical impulses from one part of the body to another
- most of this tissue is concentrated in the brain and spinal cord
CONTAINS 2 TYPES OF CELLS:
1. NEURONS- control conscious and unconscious thought processes

50. 2. NEUROGLIA- provide physical support for neural tissue, maintain the chemical composition of the tissue fluids, defend the tissue from infection
STRUCTURE OF A NEURON
- neurons are the longest cells in your body (up to 1 m in length)
- limited ability to repair because are unable to divide

51. - a typical neuron has a CELL BODY with a large nucleus
- extending from the body are several branches called DENDRITES and one AXON
- DENDRITES receive information from other neurons and AXONS carry that information to other cells

52. TISSUE INJURY AND REPAIR
Tissue repair involves 2 related processes:
1. INFLAMMATION
- the injured area is isolated from neighboring healthy tissue while damaged cells, tissue components, and dangerous microorganisms are cleaned up
- produces swelling, warmth, redness, and pain
INFECTION- inflammation resulting from presence of bacteria

53. 2. REGENERATION
- damaged tissues are replaced or repaired to restore normal functioning
- fibroblasts produce a network of collagen fibers called SCAR TISSUE
- over time this scar tissue resumes a more normal appearance
- regeneration is most successful in epithelia and connective tissue

54. AGING
- there is a decrease in the speed and effectiveness of tissue repair
- epithelia get thinner; connective tissue gets more fragile
- individuals bruise more easily; bones become brittle
- cancer rates also increase with age