1. Chapter 4

2. Tissue: group of cells that are similar in structure and function
Histology: study of tissues
Types of Tissues:
Epithelium (covering)
Connective (support)
Muscle (movement)
Nervous (control)

3. Preparing tissues for microscopy
Specimen is fixed (preserved)
Cut into thin sections (slices)
Stained with colored dyes

4. Part I: Epithelial Tissue

5. Epithelial Tissue “epithe” = laid on, covering Structure:
Covering and lining epithelium
Glandular epithelium
Function:
Protection
Absorption
Filtration
Secretion

6. Special Properties Polarity
Apical surface = exposed free surface or edge (some with microvilli, cilia)
Basal surface = lower, attached surface
Specialized contacts
Fits close together to form continuous sheets

7. Special Properties Supported by connective tissue
Rests on basement membrane
No blood supply (avascular)
Rely on diffusion and underlying connective tissue for food/O2
Regeneration – Replace lost cells

8. Classification Two names = (# cell layers) + (shape of cells)
Cell Layers: simple or stratified
Shapes: squamous, cuboidal, or columnar

12. Simple Epithelium
Absorption, secretion, filtration
Very thin

13. Simple Epithelium

14. Simple Epithelium Simple squamous Filtration, rapid diffusion
Capillary walls, air sacs in lungs, kidney filtration
Serous membranes: slick layer lining ventral body cavity and its organs

15. Simple Epithelium Simple cuboidal Secretion & absorption
Lines ducts of glands (salivary), kidney tubules, ovary surface

16. Simple Epithelium Simple columnar Absorption and secretion
Lines digestive tract
Microvilli, cilia
Mucous membranes: lubricating mucus

17. Simple Epithelium Pseudostratified columnar
Rests on basement membrane – false impression (pseudo) of being multi-layered
Secretes or absorbs
Respiratory tract – cilia propels mucus from lungs

18. Stratified Epithelium
2+ layers, more durable
Main function = protect

19. Stratified Epithelium
Stratified squamous
Withstand abuse, friction
Esophagus, mouth, outer portion of skin

20. Stratified Epithelium
Stratified cuboidal
Usually 2 layers
Mainly in ducts of large glands (sweat, mammary, salivary)
Sweat Gland
Esophageal Gland

21. Stratified Epithelium
Stratified columnar
Thick, waterproof layer
Pharynx, male urethra, lining ducts

22. Transitional Epithelium
Able to change shape (cuboidal → squamous)
Lining of hollow urinary organs (bladder, ureter, urethra)
Stretches when filled with urine

23. Glandular Epithelium Gland: make and secrete a particular product
2 Types:
Endocrine gland: produce hormones secreted into tissue fluid or bloodstream
Exocrine gland: secrete products into ducts → onto body surfaces or body cavities
Eg. mucous, sweat, oil, saliva, bile

24. Exocrine Glands Unicellular Multicellular Mucus cells or goblet cells
Duct structure

25. Part II: Connective Tissue

26. Connective Tissue Most abundant and widely distributed tissue
Main classes:
Connective tissue proper (loose & dense)
Cartilage
Bone
Blood
Functions:
Binding and support
Protection
Insulation
Transport substances

27. Classification Variations in blood supply Extracellular matrix
Avascular (no blood) – cartilage
Poorly vascular – tendons, ligaments
Extracellular matrix
Produced by cells, secreted to exterior
Ground substance: “glue” - fills space between cells & fibers
water + adhesion proteins + polysaccharides
Fibers: provide support
Collagen - strength
Elastic – stretch
Reticular – fine network, “skeleton” of organs

28. Loose Connective Tissue
Universal packing material
Subclasses: areolar, adipose, reticular
Structure: softer, fewer fibers, gel-like matrix
Functions:
Cushion & protect organs (areolar, fat)
Store nutrients (fat)
Internal framework (reticular)
Fight infection (areolar)
Cells: fibroblasts, adipocytes (fat cells)
Locations: under skin, lymph nodes, hips, behind eyeballs

32. Dense Connective Tissue
Tendons & ligaments
Subclasses: dense regular, dense irregular, elastic
Structure: mainly collagen fibers
Functions:
Elastic
Resist tension
Cells: fibroblasts
Locations: tendons (muscle-bone), ligaments (bone-bone), lower layers of skin

34. Cartilage Subclasses: hyaline, elastic, fibrocartilage
Structure: flexible, no nerves or blood
Functions:
Support
Compression
Cells: chondroblasts, chondrocytes
Locations: larynx, joints, tip of nose, ear, intervertebral discs, rib-breastbone, knee joint

36. Bone Osseous tissue Subclasses: compact, spongy
Structure: hard, calcified matrix; blood vessels
Functions:
support & protect
Store calcium
Blood cell formation (marrow)
Cells: osteoblasts, osteocytes
Locations: bones

38. Blood Vascular tissue Subclasses: blood cells, plasma
Structure: fluid within blood vessels, no fibers
Functions:
Transport vehicle (nutrients, wastes, gases, hormones)
Cells: white blood cells (leukocytes), red blood cells (erythrocytes), platelets
Locations: blood vessels

40. Part III: Muscle Tissue
3 types:
Skeletal muscle
Cardiac muscle
Smooth muscle

41. Skeletal Muscle Description: Function: Location in the body:
Long, cylindrical
Multinucleate (2+ nuclei)
Striated (banded appearance)
Function:
Muscles contract, pull on bones or skin → cause body movements
Location in the body:
Attached to skeleton
Other features:
Voluntary control

43. Cardiac Muscle Description: Function: Locations in the body:
Striated
Uninucleate (1 nucleus)
Branching cells – fit at junctions called intercalated discs
Function:
Propel blood through blood vessels to all parts of body
Locations in the body:
Walls of the heart
Other features:
Involuntary control

45. Smooth Muscle Description: No visible striations 1 central nucleus
Spindle-shaped (pointed ends)
Function:
Propel substances through hollow organs
Locations in the body:
Walls of organs (stomach, bladder, uterus, blood vessels)
Other features:
Involuntary control
Contracts slowly
Peristalsis: wavelike motion that moves food through SI

47. Part IV: Nervous Tissue
2 Major Cell Types:
Neurons
Respond to stimuli
Transmit electrical impulses
Other cells
Support, insulate, protect neurons

48. Part IV: Nervous Tissue
Main component of nervous system
Structure: neuron = dendrite + cell body + axon
Function: regulates and controls body functions
Location in the body: brain, spinal cord, nerves

50. Tissue Repair Wound healing Two ways:
Regeneration: replace destroyed tissue by same kind of cells
Fibrosis: form scar tissue (dense fibrous connective tissue)
Depends on:
Type of tissue damaged
Severity of injury

51. Steps to Tissue Repair:
Inflammation
Capillaries become very permeable
WBC’s and clotting proteins seep into injured area
Clot prevents loss of blood (surface dries, forms a scab)

52. Steps to Tissue Repair:
Granulation tissue forms
Delicate pink tissue with new capillaries
Connective tissue produces collagen fibers
Epithelial cells multiply over granulation tissue

53. Steps to Tissue Repair:
Surface epithelium regenerates
Surface epithelium thickens
Fibrous tissue matures – forms scar tissue

54. Regenerative Capacity of Different Tissues
Extremely Well
Moderate
Weak
Virtually None
(mostly scar tissue)
Skin epidermis
Mucous membranes
Fibrous connective
Blood
Bones
Smooth muscle
Tendons, ligaments
Skeletal muscle
Cartilage
Cardiac muscle
Nervous tissue