1. HISTOLOGY
THE STUDY OF TISSUES

2. GENERAL
Tissue = Cells with similar structure & function organized into groups or layers
Four major types:
Epithelial (Covers or lines surfaces, found in glands)
Connective (Binds & supports body parts)
Muscle (Movement)
Nervous (Detects changes & transmits info.)

3. CHARACTERISTICS OF EPITHELIAL TISSUE
Covers all body surfaces inside & out
Many tightly packed cells, usually arranged into layers
Free surface & basement membrane
Functions: protection, absorption, sensation, secretion
High rate of cell division (healing)
Avascular (rely on diffusion)

4. Epithelial Cell Surface - May be variously modified
Cilia move substances across the free surface. Microvilli increase surface area for absorption. Stereocilia vibrate in response to sound waves. Apical cells may be keratinized for protection.

5. CLASSIFICATION OF EPITHELIAL TISSUE
Layers
Simple (one layer)
Stratified (>1 layer; Note: only cells at surface have characteristic shape)
Shapes
Squamous (thinnest, if simple)
Cuboidal
Columnar
Transitional (changes shape)

7. CONNECTIVE TISSUE - GENERAL
Few cells widely spaced in non-living matrix
Matrix may be fibrous, solid, semi-solid, fluid
Largest % of tissue by weight; found in all body parts
Binds, protects, supports, transports, storage, insulation
May be vascular

8. CONNECTIVE TISSUE - GENERAL
Fibroblast
Most common cell
Secretes fibers
Collagen – strong, flexible, structural
Elastic – stretch & recoil
Reticular – highly branched, supportive
Differs in type, amount, and arrangement of fibers in matrix
Loose or dense; regular or irregular

10. MUSCLE TISSUE Contract, provide movement
3 types based on location, morphology, & function:
Skeletal (attached to bones; voluntary movement)
Smooth (moves substances through hollow organs)
Cardiac (heart; moves blood)

12. NERVOUS TISSUE Rapidly regulates & coordinates body functions
Brain, spinal cord, nerves
2 types of cells:
Neuron (nerve cell)
Most specialized cell in body
Generates & transmits nerve impulses
Neuroglia (“nerve glue”)
Assist neurons (bind, protect, supply)

14. Hollow Organs Substances pass through Wall is composed of 3-4 layers
Lumen is term for inner space
Septum (internal wall) may subdivide lumen
E.g. digestive organs, urinary tract, heart, blood vessels, ducts

15. Solid Organs Outer Cortex Deeper Medulla May require internal support
Parenchyma is functional tissue; stroma is supportive/filler tissue (usually deeper)
E.g. brain, spleen,
kidney