Histology is the study of tissues. Tissues are composed of cells and intercellular material specialized for a particular function. There are four basic tissue types: epithelial, connective, muscular, and nervous. Epithelial tissues form protective barriers and linings and come in several forms defined by cell shape and layer arrangement including simple squamous, stratified squamous, simple cuboidal, simple columnar, and pseudostratified columnar epithelium. Each type has characteristic features and locations within the body related to its specialization for functions like secretion, filtration, and protection.

1. HISTOLOGY
THE STUDY OF
TISSUES

2. TISSUES
 A tissue is a
functional collection of
cells and associated
intercellular material
that is specialized to
carry out a specific
role.

3. Technique of
Tissue
Sectioning
1. Tissue is preserved in a fixative
(chemical)
2. Cut into very thin slices by a special
machine
- slices are called histological
sections
3. Sections are mounted on microscope
slides
4. Sections on slides are stained

7. Classification of the FOUR basic
tissues
 1- Epithelial
 2- Connective (CT)
 3- Muscular
 4- Nervous

8. Connective vs Epithelial
 Lots of extra-cellular  Little extra cellular
material, few cells material, lots of cells
 Lots of blood vessels  No blood vessels
 Covered by other  Usually form surface
tissues layers and are NOT
covered by another
tissue (*except blood
vessels)
Epithelial tissue
Connective tissue

9. Epithelial Tissues
 Flat sheet of cells with upper surface exposed to
environment or internal space. (Barriers!
Protection!)
 Covers body surface & lines body cavities
 Forms external & internal lining of organs
 Constitutes most gland tissues (Secretion!)
 Little extra cellular material
 No room for blood vessels (avascular) so
depends on blood vessels in CT for food and
waste movement

10. Epithelial Tissue Specifics
 Basement membrane:
membrane

Anchors epith to CT
Apical Surface- faces surface, may have

Made of proteins, cilia, microtubules
acellular
 Basal surface - epith
surface that sits on Connect cells
basement membrane to basement
membrane
 Apical surface - epith Basal
surface that faces away Surface-
Adheres to
from basement. “Free
Basement
Surface” membrane
A thickening of the basement
membrane is a contributing cause
of blindness and kidney in diabetes.

11. Basement Membrane

12. Classification of Epithelial Tissues
 Arrangement of Cells  Shape of Cells

Simple (single layer)  Squamous

Stratified (multiple layers) 
Cuboidal
 Pseudostratified (single 
Columnar
layer, but looks multilayered

13. Simple Squamous (“fried eggs”)
 Flat & thin, form linings
 Location:

Mesothelium

Endothelium
 Bronchioles and alveoli
of lungs, kidney,
tympanic membrane
 Function:

Filtration

Diffusion
 Secretion

14. Mesothelium is the simple squamous
epithelium lining body cavities.

15. Endothelium is the simple squamous
epithelium lining blood vessels
Two blood vessels seen in cross section

16. Quick Review
13. Identify the tissue.
14. Identify the structure.
15. What tissue makes up
this (#14) structure?
16. Identify the cellular
structure.
Click for Answers
13. Simple Cuboidal Epithelium
14. Blood Vessel
15. Simple Squamous epithelium
16. Nucleus

17. Stratified Squamous Epithelial
 Characteristics:

Many layers becoming
flatter from basal to
Stratified layers
apical surfaces
of epithelial cells

Basal cells are mitotic
 Apical cells are dead
Basal cells
 LOCATIONS: Mitotic area
Cells are rounder

Keritanized
• skin
Stratified layers

Nonkeritanized
• Mouth, esophagus,
Apical cells will be sloughed off and
pharynx, vagina replaced by cells in layer below.
 FUNCTION:
 protection

19. Simple Cuboidal Epithelium
 Characteristics: single layer, square or
roundish
 Location: Ducts of many glands, lines
kidney tubules, surface of ovary
 Function: secretion and absorption

20. Simple cuboidal epithelium lining a
tubule (longitudinal cut).

21. Simple Columnar Epithelium
 Characteristics: tall, narrow cells
• May contain brush borders (microvilli) & goblet
cells
 Location: lines the gastrointestinal tract from stomach to
anus, ducts of glands, gallbladder
 Function: secretion and absorption
Nucleus

22. Simple columnar epithelium with very
regular line-up of nuclei.

23. Pseudostratified Ciliated Columnar
Epithelium
 Location: Respiratory tract
 Function: secrete mucous to trap foreign particles
 Not all cells reach apical layer BUT all cells are connected
to basement membrane!
 Cilia (sweep), Goblet cell (secrete mucous)
Cilia

24. Microvilli
Goblet Cell
Basement Membrane