1. Histology: The Study of Tissues

2. Tissues
A tissue is a group of similar cells specialized for a particular function
Classified according to their structure & function
Four Primary Tissue Types
Epithelial – covering
Connective – support
Muscular – movement
Nervous - control

3. Epithelial Tissue - Epithelium
Lining, covering, & glandular tissue of the body.
Forms glands, outer layer of skin, & lines body cavities
Contains many cells, close together with no blood vessels. Can easily regenerate
Rely on diffusion from capillaries for food & oxygen
Functions
Protection, absorption, filtration, & secretion

4. Classification of Epithelium
Classified according to cell shape & arrangement
3 cell shapes
Squamous: flattened
Cuboidal: cube-shaped
Columnar: column shaped
2 Arrangements
Simple epithelium: one layer of cells
Stratified epithelium: more than one cell layer

6. Classification of Epithelium
Simple Squamous
Single layer of flattened cells
Diffusion & filtration
Lines the lungs, kidneys, heart & blood vessels
Simple Cuboidal
Single layer of cube-shaped cells
Secretion & absorption
Covers ovaries, kidneys, & eyes
Simple Columnar
Single layer of elongated cells
Absorption & secretion of mucus
Lines the entire digestive tract

7. Simple Squamous

8. Simple Cuboidal

9. Simple Columnar

10. Classification of Epithelium
Stratified Squamous
Protective tissue – outer portion of the skin
Lines the mouth & esophagus
Stratified Cuboidal
Adult sweat glands, portions of the pharynx, & epiglottis
Stratified Columnar
Protects & secretes
Male urethra & large excretory ducts

11. Stratified Squamous

12. Stratified Cuboidal

13. Stratified Columnar

15. Connective Tissue Most abundant tissue in the body
Fewer cells with a rich blood supply
except for tendons, ligaments, & cartilage
Produces an extracellular matrix (ECM)
Non-living substance found outside of cells
Allows connective
tissue to bear weight, stretch, & tolerate abrasion
Can be soft (fat)
or hard (bone)
Functions
Protects, supports,
and binds together organs

16. Types of Connective Tissue
Bone
Bone cells surrounded by very hard ECM
Protects & supports body organs
Cartilage
Less hard & more flexible then bone
Embryonic skeleton, ends of bones, nose, attaches ribs to breast bone, external ear, between vertebrae, etc.
Provides for movement & support
Dense Connective Tissue
Forms tendons & ligaments
Close packing of fibers

17. Types of Connective Tissue
Loose Connective Tissue
Softer with more cells & fewer fibers
Various types
Adipose tissue – fat storage + body insulation
Areolar tissue – cushions & protects body organs
Reticular connective tissue – interlacing reticular fibers
Found in the liver, spleen, & lymph nodes
Blood – Vascular Tissue
Blood cells & blood plasma
Transport vehicle for the cardiovascular system

18. Bone

20. Muscle Tissue
Highly specialized to contract (shorten) to produce movement
Three types
Skeletal muscle
Striated – banded
Voluntary movement
Smooth muscle
No striations
Involuntary movements
Breathing, digestion, birth, reflexes, etc.
Cardiac muscle
Found only in the heart – striated
Involuntary control – pumps the heart

21. Nervous Tissue Neurons – nerve cells Unique structure: 3 parts
Receive & conduct impulses from one part of the body to another
Unique structure: 3 parts
Dendrites – receive message
Cell body – interprets message
Axon – conducts the message
There are 100 billion neurons in the brain alone

22. Nervous Tissue Supporting cells
(neuroglia)
insulate, protect, & supports the neurons

24. Tissue Inflammation & Repair
An attempt to restore homeostasis
Damage causes inflammatory response
Redness, pain, heat, swelling
Chemicals in the body initiate inflammatory responses & isolate infected area
Pus is often produced – can form an abscess
Damaged tissue is then replaced by healthy cells
Tissue repair is completed after harmful substances are removed/neutralized
Vit. A,B,C,D,E,&K help tissue repair
Needs adequate blood circulation – process slows with aging