1. The Tissue Level of Organization
Chapter 4
The Tissue Level of Organization

2. Tissues:
The “Real” A&P

3. Histology: The Study of Tissues

4. Tissues and Histology Tissue Level of Organization
Epithelial
Connective
Muscle
Nervous
Histology: Microscopic Study of Tissues

5. Embryonic Tissue Germ layers Endoderm Mesoderm Ectoderm Inner layer
Forms lining of digestive tract and derivatives
Mesoderm
Middle layer
Forms tissues as muscle, bone, blood vessels
Ectoderm
Outer layer
Forms skin and neuroectoderm

6. Epithelium Characteristics
Consists almost entirely of cells
Covers body surfaces and forms glands
Has free and basal surface
Specialized cell contacts
Avascular
Undergoes mitosis

7. Functions of Epithelia
Protecting underlying structures
Acting as barriers
Permitting the passage of substances
Secreting substances
Absorbing substances

8. Classification of Epithelium
Simple
Squamous, cuboidal, columnar
Stratified
Pseudostratified
columnar
Transitional
Cuboidal to columnar when not stretched and squamouslike when stretched

9. Types of Epithelium

10. Types of Epithelium

11. Types of Epithelium

12. Types of Epithelium

13. Types of Epithelium

14. Types of Epithelium

15. Types of Epithelium

16. Types of Epithelium

17. Functional Characteristics
Cell layers and shapes
Diffusion, Filtration, Secretion, Absorption, Protection
Cell surfaces
Microvilli: Increase surface area absorption or secretion
Cilia: Move materials across cell surface
Cell connections
Desmosomes, tight, gap
Glands
Exocrine: Have ducts
Endocrine: Have no ducts

18. Cell Connections Functions Types Bind cells together
Form permeability layer
Intercellular communication
Types
Desmosomes
Tight
Gap

19. Exocrine Glands
Unicellular
Goblet cells

20. Multicellular Exocrine Glands

21. Exocrine Glands and Secretion Types
Merocrine
Sweat glands
Apocrine
Mammary glands
Holocrine
Sebaceous glands

22. Connective Tissue Abundant
Consists of cell separated by extracellular matrix
Diverse
Performs variety of important functions

23. Functions of Connective Tissue
Enclosing and separating as capsules around organs
Connecting tissues to one another as tendons and ligaments
Supporting and moving as bones
Storing as fat
Cushioning and insulating as fat
Transporting as blood
Protecting as cells of the immune system

24. Connective Tissue Cells
Specialized cells produce the extracellular matrix
Suffixes
-blasts: create the matrix
-cytes: maintain the matrix
-clasts: break the matrix down for remodeling
Adipose or fat cells
Mast cells that contain heparin and histamine
White blood cells that respond to injury or infection
Macrophages that phagocytize or provide protection
Stem cells

25. Extracellular Matrix Components Protein fibers Ground substance Fluid
Collagen which is most common protein in body
Reticular fill spaces between tissues and organs
Elastic returns to its original shape after distension or compression
Ground substance
Shapeless background
Fluid

26. Connective Tissue Categories
Embryonic or mesenchyme
Adult
Loose
Dense
Connective tissue with special properties
Cartilage
Bone
Blood

27. Loose Connective Tissue
Also known as areolar tissue
Loose packing material of most organs and tissues
Attaches skin to underlying tissues
Contains collagen, reticular, elastic fibers and variety of cells

28. Dense Connective Tissue
Dense regular
Has abundant collagen fibers
Tendons: Connect muscles to bones
Ligaments: Connect bones to bones
Dense regular elastic
Ligaments in vocal folds
Dense irregular
Scars
Dense irregular collagenous
Forms most of skin dermis
Dense irregular elastic
In walls of elastic arteries

29. Dense Regular Connective Tissue

30. Dense Irregular Connective Tissue

31. Connective Tissue with Special Properties
Adipose tissue
Consists of adipocytes
Types
Yellow (white)
most abundant, white at birth and yellows with age
Brown
found only in specific areas of body as axillae, neck and near kidneys
Reticular tissue
Forms framework of lymphatic tissue
Characterized by network of fibers and cells

32. Adipose Tissue

33. Reticular Tissue

34. Cartilage Composed of chondrocytes located in spaces called lacunae
Next to bone firmest structure in body
Types of cartilage
Hyaline
Fibrocartilage
Elastic

35. Hyaline Cartilage
Found in areas for strong support and some flexibility
Rib cage and cartilage in trachea and bronchi
Forms most of skeleton before replaced by bone in embryo
Involved in growth that increases bone length

36. Fibrocartilage Slightly compressible and very tough
Found in areas of body where a great deal of pressure is applied to joints
Knee, jaw, between vertebrae

37. Elastic Cartilage Rigid but elastic properties
External ears, epiglottis

38. Bone
Hard connective tissue that consists of living cells and mineralized matrix
Organic and inorganic
Types
Cancellous or spongy bone
Compact bone

39. Bone

40. Blood Matrix between the cells is liquid Hemopoietic tissue
Forms blood cells
Found in bone marrow
Yellow
Red

41. Bone Marrow

42. Muscle Tissue Characteristics Types Contracts or shortens with force
Moves entire body and pumps blood
Types
Skeletal
Striated and voluntary
Cardiac
Striated and involuntary
Smooth
Nonstriated and involuntary

43. Skeletal Muscle

44. Cardiac Muscle

45. Smooth Muscle

46. Nervous Tissue Found in brain, spinal cord and nerves
Ability to produce action potentials
Cells
Nerve cells or neurons
Consist of dendrites, cell body, axons
Consist of multipolar, bipolar, unipolar
Neuroglia or support cells

47. Neurons

48. Neuroglia

49. Membranes Mucous Serous Synovial
Line cavities that open to the outside of body
Secrete mucus
Serous
Line cavities not open to exterior
Pericardial, pleural, peritoneal
Synovial
Line freely movable joints
Produce fluid rich in hyaluronic acid

50. Inflammation Response when tissues damaged or with an immune response
Manifestations
Redness, heat, swelling, pain, disturbance of function
Mediators
Include histamine, kinins, prostaglandins, leukotrienes
Stimulate pain receptor and increase blood vessel permeability

51. Tissue Repair Substitution of viable cells for dead cells Skin repair
Primary union: Edges of wound close together
Wound fills with blood
Clot forms
Scab
Pus
Granulation tissue
Scar
Secondary union: Edges of wound not close
Clot may not close gap
Inflammatory response greater
Wound contraction occurs leading to greater scarring

52. Tissue Repair

53. Tissues and Aging
Cells divide more slowly in older than younger people
Tendons and ligaments become less flexible and more fragile
Arterial walls become less elastic
Rate of blood cell synthesis declines in elderly
Injuries are harder to heal in elderly