1. The Tissue Level of Organization
Histology
The Tissue Level of Organization

2. Histology
The study of tissues and how tissues are combined in various ways to form organs & membranes of the human body.
The human body contains four primary types of tissues:
Epithelial
Connective
Muscle
Neural (nerve) tissue.

3. I. Epithelial Tissue Made of cells with little space between cells.
The cells are so tightly packed together that blood vessels can’t penetrate between them and is called avascular.

4. Epithelial Tissue
In certain areas of the body epithelial tissue may perform the following functions:
Control Permeability:
Provide Sensitivity
Provide Physical Protection:
Produce Secretions:

5. Epithelial Tissue Two Types Covering & Lining and Glandular.
Covering & Lining Epithelia is classified based on the number of cell layers and the cell shape.
Glandular Epithelia is classified based on if the tissue secretes its product into a gland or not.

6. Covering & Lining Epithelial
Classification based on:
Number of cell layers.
Simple- single layer.
Stratified- many layers.
Pseudostratified- appears to be many layers but is actually a single layer.
Cell Shape.
Squamous- Flat.
Cuboidal- Cube shaped.
Columnar- Rectangular.
Transitional- Cuboidal & Squamous.

7. Simple Squamous Flat cells with central nucleus.
Function: Permits the efficient diffusion of materials.
Location: Lining of body cavities, lines the walls of blood & lymphatic vessels, forms the walls of air sacs.

8. Simple Squamous

9. Simple Cuboidal
Single layer of cube-shaped cells with central nucleus, often have cilia and/or microvili.
Function: Forms the walls of small ducts and tubes that carry secretions.
Location: Kidneys, Liver, Glands.

10. Simple Cuboidal

11. Simple Columnar
Single layer of rectangle cells whose nuclei lie near the base (basal) of the cell.
Function: Absorb and secrete; mucus, enzymes, etc.
Location: Uterus, Stomach, Digestive Tract, Bronchi.

12. Simple Columnar

13. Stratified Squamous
Multiple layers, only top layer is squamous the deeper layers are cubiodal and or columnar.
Function: Covers areas that must resist wear & tear, protects openings of the body from abrasions.
Location: Esophagus, Mouth, Nose, Vagina, etc.

14. Stratified Squamous

15. Stratified Cuboidal Function: Protection.
Location: Sweat Glands. Mammary Glands, Salivary Glands.

16. Stratified Cuboidal

17. Stratified Columnar Function: Protection & Secretion.
Location: Male Urethra, some large ducts, rare in the body.

18. Stratified Columnar

19. Pseudostratified Columnar
Appears to be multilayered but is not.
Function: Often contains cilia which creates currents to move mucus.
Location: Lines parts of respiratory tract, such as the trachea & bronchi.

20. Pseudostratified Columnar

21. Pseudostratified

22. Transitional Multilayered cube-like cell shape.
Function: Can stretch(elasticity) and return to the original shape (extensibility).
Location: Lines Bladder, Urethra, Ureters.

23. Transitional

24. Glandular Epithelium
Tightly packed cells that specialize in manufacturing and secreting products.
Two categories:
Exocrine: Releases products into ducts.
sweat & oil glands, salivary, and mucus glands.
Endocrine: Releases products into extracellular space (blood)
pituitary gland, thyroid gland, and adrenal gland.

25. II. Connective Tissue
Is composed of scattered loosely packed cells that are within a large amount of nonliving intercellular material.
It is vascular
Its primary function is to hold other tissues and organs in place.
Two categories of connective tissue
Produces & Maintains-(matrix)
Protects From Infection (white blood cells)

26. Connective Tissue 4 Types of connective tissue
A. Connective tissue proper
B. Cartilage
C. Bone
D. Blood forming (spongy bone)

27. A. Connective Tissue Proper
Types of connective tissue proper: Areolar, Adipose, Reticular, Dense Connective.
1. Areolar Tissue:
AKA: Loose Connective Tissue.
Contains fibroblast(producing cells) and macrophages (protecting cells).
Function: Anchors and cushions organs, vessels, nerves. Fights bacteria. Stores lipids.

28. Areolar Tissue

29. A. Connective Tissue Proper
2. Adipose Tissue:
Contains adipocytes (producing cells which contain deposits of fat).
Function: Provides reserve energy, insulates & protects organs.

30. Adipose Tissue

31. A. Connective Tissue Proper
3. Dense Connective Tissue
Two Types:
Dense Regular- Fibers are arranged in parallel fashion. Extremely resistant to stress.
tendons (muscle to bone)
ligaments (bone to bone)
Dense Irregular- Fibers are arranged in an interwoven meshwork. Forms an external wrapping.
Location: Wrapped around bone, cartilage, kidneys, liver, spleen, and where the tendon connects to the bone.

32. Dense Regular

33. Dense Irregular

34. A. Connective Tissue Proper
4.Reticular
Location: Lymphoid organs
Function: Form a soft internal skeleton to support other tissues.

35. Reticular Tissue

36. B. Cartilage Harder than connective tissue proper.
Contains chondrocytes (producing cells).
There are three types of cartilage:
Hyaline, Elastic, Fibrocartilage.

37. B. Cartilage 1. Hyaline Cartilage- Bluish-white in color.
Most abundant of all three.
Function: Supports and reinforces, with-stands compression.
Location: Forms embryonic skeleton, upper respiratory tract, costal cartilage, moveable joints.

38. Hyaline Cartilage

39. B. Cartilage 2. Elastic Cartilage Yellowish in color.
Function: Maintains shape allows for flexibility.
Location: Ears, Nose, Epiglottis.

40. Elastic Cartilage

41. B. Cartilage 3. Fibrocartilage Has an abundance of collagen.
Is found in association with hyaline cartilage.
Function: Shock absorber.
Location:intervertebral disc, pubis symphysis, knee joint.

42. Fibro Cartilage

43. C. Bone
Has dense intercellular material composed of mineral salts and collagenous fibers.
Made up of osteocytes
Also known as osseous tissue.
Two Types of Bone
Compact and Spongy.

44. C. Bone Compact Bone: Forms the bones of the skeletal system.
Function: Provide structural support, stores calcium.
Location: All bones, the hard outside layer of bone.

45. Bone (compact)

46. C. Bone
Spongy Bone: Found inside of compact bone. Has blood forming tissue called red marrow.
Function: to produce blood cells.
Location: inside the bone of the skeletal system.
Blood: is a type of connective tissue known as formed elements.
Also know as liquid tissue
Has both solid (formed elements) and liquid components.

47. Red Blood Cells

48. Spongy Bone

49. III. Muscle
Tissue made of specialized cells that contain protein filaments which allow the cells to contract.
The protein fibers are arranged in parallel bundles.
The Three types of muscle are:
Skeletal, Smooth, and Cardiac.

50. A. Skeletal Muscle Striated (has bands of stripes). Multi-nucleated
Attaches to bone, is the primary mover in the muscular system.
Voluntary (you control).
Function: Body movement.

51. Skeletal Muscle

52. B. Smooth Muscle Not striated, Single Nucleus.
In the walls of blood vessels and visceral organs.
Involuntary (not consciously controlled).
Function: Movement of: food, blood urine, child birth etc.

53. Smooth Muscle

54. C. Cardiac Muscle Striated, Single Nucleus
Contains thick cell membranes called intercalated disks.
Found in the walls of the heart.
AKA myocardium.
Involuntary.
Function: move blood in the circulatory system.

55. Cardiac Muscle

56. IV. Nervous Tissue
Has well developed properties of conductivity and excitability.
Transmits electrochemical signals.
Two Types of Nervous Tissue:
Neurons-Basic functioning unit of nervous tissue conducts electrochemical messages.
Neuroglia- Cells of the spinal cord and brain that maintain and support neurons.

57. Nervous Tissue