1. Classification of Tissues Martini Chapter 4
Lab Activity 4
Classification of Tissues
Martini Chapter 4
Portland Community College
BI 231

2. Tissues Groups of cells similar in structure and function
Each tissue is then further subdivided into categories.
All organs are made of a combination of different tissues.
The four types of tissues
Epithelial
Connective
Muscle
Nerve

3. Epithelial Tissue Distinguishing Characteristics
Cellularity: Composed almost entirely of cells
Polarity: apical and basal surfaces (top and a bottom)
Attachment: Supported by connective tissue (basement membrane)
Avascular: Contains no blood vessels: obtains nutrients by diffusion
Regeneration: Rapidly replaces lost cells by cell division

4. Classification of Epithelia
First name:
Simple: one layer
Stratified: more than one layer
Second name:
Based on the shape of the top layer of cells
Squamous (flat)
Cuboidal (square)
Columnar (rectangle)
Two additional categories
Transitional
Pseudostratified

5. Classification of Epithelia

6. Classification of Epithelia
Squamous
Cuboidal
Columnar

7. Simple Squamous Epithelium
Single layer of flattened cells with disc-shaped nuclei and sparse cytoplasm

8. Simple Squamous Epithelium
Top View

10. Simple Squamous Epithelium

11. Simple Squamous Epithelium
Functions:
Diffusion
Alveoli in the respiratory system allows for exchange of O2 and CO2
Filtration
Capillaries allow fluid and other substances out and holds blood cells and proteins in
Lubrication
Secretes lubricating substances in serosae

12. Simple Cuboidal Epithelium
Single layer of cube like cells with large, spherical central nuclei

14. Simple Cuboidal Epithelium

15. Simple Cuboidal Epithelium
Functions:
Secretion
Glands such as the thyroid are composed of simple cuboidal epithelium and secrete hormones ect…
Absorption
In the kidney, the proximal convoluted tubule is composed of simple cuboidal epithelium and reabsorbs water and other nutrients from the filtered fluid

16. Simple Columnar Epithelium
Single layer of tall cells with oval nuclei toward the basal surface
Goblet cells are often found in this layer

17. Simple Columnar Epithelium

18. Simple Columnar Epithelium

19. Simple Columnar Epithelium
Functions
Secretion
Example: In the stomach, these cells secrete digestive enzymes
Absorption
Example: In the intestine, these cells absorb nutrients

20. Pseudostratified Columnar Epithelium
Single layer of cells with different heights; some do not reach the free surface
Nuclei are seen at different levels
May be ciliated (PCCE) or non-ciliated

21. Pseudostratified Columnar Epithelium

22. Pseudostratified Columnar Ciliated Epithelium (PCCE)

23. Pseudostratified Columnar Ciliated Epithelium (PCCE)
Functions
Protection
Example: Lines the upper respiratory tract. The cilia sweep debris toward the throat
Secretion
Example: May contain goblet cells (unicellular glands) that secrete mucus

24. Stratified Squamous Epithelium
Composed of several layers of cells
Top layer flat
Bottom layers any shape
Function in protection of underlying areas subjected to abrasion

25. Stratified Squamous Epithelium
Non-keratinized
Composed of several layers of cells
Top layer flat
Bottom layers any shape

26. Stratified Squamous Epithelium Non-Keratinized

27. Stratified Squamous Epithelium Non-Keratinized
Functions
Physical protection against abrasion and pathogens
Non-Keratinized is associated with “moist” areas
Mouth
Throat
Esophagus
Anus
Vagina

28. Stratified Squamous Epithelium Keratinized
Looks “flakey” on the top

29. Stratified Squamous Epithelium Keratinized

30. Stratified Squamous Epithelium Keratinized
Functions
Physical Protection
Found only in the epidermis of the skin
Keratin is a protein that helps strengthen the cells against abrasion

31. Transitional Epithelium
Several cell layers, basal cells are cuboidal
Apical cells are dome shaped when not stretched
Apical cells are flat when stretched
Only found in Urinary System
Functions:
Allows expansion and recoil after stretching

32. Transitional Epithelium
Distended bladder
Empty bladder

33. Stratified Cuboidal and Columnar
Typically two cell layers thick
Rare
Functions:
Secretion
Found in some sweat and mammary glands

34. Stratified Cuboidal Epithelium

35. Stratified Cuboidal Epithelium

36. Stratified Columnar Epithelium
Limited distribution in the body
To tell the difference between this and pseudostratified columnar, look at the nucleus.
The nuclei are lined up in a straight row
Function
Protection
Found in the pharynx, male urethra, lining some glandular ducts, and anus

37. Stratified Columnar Epithelium

38. Stratified Columnar Epithelium

39. Connective Tissue 4 Types Connective Tissue Proper Bone Blood
Cartilage

40. Connective Tissue Features
Specialized cells
Matrix: Nonliving material between the cells that makes up most of the volume (ground substance + fibers)
Extracellular fibers
Ground substance: Composed chiefly of interstitial fluid, cell adhesion proteins, and proteoglycans
Specific composition varies between tissues (Blood=fluid, Cartilage=gel like, Bone=Solid)

41. Connective Tissue Fibers
Collagen Fibers: Fibrous protein molecules
Extremely tough
High tensile strength
Strongest type of fibers in connective tissue.

42. Connective Tissue Fibers
Elastic Fibers: Form branching networks
Elastin: a rubber like protein that allow it to act like a rubber band and snap back to its original shape after it is stretched
Reticular Fibers: Forming delicate networks
Fine collagenous fibers (with a different chemical structure) branch extensively
Surround small blood vessels and support soft tissue organs

43. Cells of Connective Tissue Proper
Fibroblasts: Secrete the matrix
Macrophages: Scavenger cells that engulf pathogens or damaged cells
Adipocytes: Fat cells
Mesenchymal Cells: Stem cells
Mast cells: Stimulate local inflammation: contain histamine and heparin
Lymphocytes/microphages: WBC involved in immunity

44. Areolar Connective Tissue (Loose)
Gel like matrix
Contains all 3 fiber types
Functions:
Wraps and cushions organs
Holds and conveys tissue fluid
Locations:
Under epithelial tissues
Packages organs
Surrounds capillaries

45. Areolar Connective Tissue (Loose)
Fibroblast
Collagen fiber
Macrophage
Elastic fiber

46. Adipose Tissue (Loose)
Function:
Storage of lipid molecules
Insulation

47. Reticular Connective Tissue (Loose)
Network of reticular fibers in a loose ground substance
Functions
Soft internal skeleton that supports other cell types
Locations
Lymph nodes
Bone marrow
Spleen

48. Reticular Connective Tissue (Loose)

49. Dense Regular Connective Tissue
Primarily parallel collagen fibers
Major cell type: fibroblast
Functions:
Withstands great tensile stress pulling in one direction
Locations:
Tendons
Ligaments
Aponeuroses

50. Dense Regular Connective Tissue

51. Dense Irregular Connective Tissue
Irregularly arranged collagen fibers
Functions:
Withstands tension exerted in many directions
Provides structural strength
Locations:
Dermis of skin
Submucosa of digestive tract
Fibrous capsules of organs and joints

52. Dense Irregular Connective Tissue

53. Elastic Connective Tissue (Dense)
Dense regular CT dominated by elastic fibers
Functions:
Stabilizes positions of vertebrae and penis
Cushions and permits expansion and contraction of organs
Locations:
Between vertebrae
Ligaments supporting penis, transitional epithelia
Blood vessel walls

54. Elastic Connective Tissue (Dense)

55. Blood: Hematopoietic Tissue
Functions:
Transportation
Immunology
Hemostasis

56. Bone: Osseous Tissue Functions: Lever for muscles Mineral storage
protection

57. Hyaline Cartilage Functions: Locations: Stiff but flexible support
Reduces friction between bony surfaces
Locations:
Articular surfaces
Larynx
Trachea
Nasal septum

58. Elastic Cartilage Functions: Locations: Support, but flexible Ear
Epiglottis

59. Fibrocartilage Functions: Locations: Resists compression
Prevents bone-to-bone contact
Locations:
Meniscus of knee
Pubic symphysis
Intervertebral discs

60. Skeletal Muscle
Voluntary
Multiple peripheral nuclei
Striated

61. Skeletal Muscle: Peripheral Nuclei

62. Cardiac Muscle: Arrow: Intercalated Discs
One or two central nuclei
Striated
Involuntary
Found only in the heart

63. Smooth Muscle One central nuclei No striations Involuntary
Found in hollow organs, blood vessels

64. Nervous Tissue Functions: Neurons: Electrical signaling
Glial cells: Support of neurons

65. Nervous Tissue

66. The End
The End