Biology Theory Lec. 7

1. University of Duhok
College of Health Sciences
Dep. of Medical Laboratories
Biology/1st Stage
Lecture 7
Dr.: Shameeran S. Ismael
BVM & S, M.Sc Medical Microbiology(Parasitology),
PhD Molecular Parasitology

2. Tissue:
• Groups of cells similar in structure and
function, that carry out a common function:
 Providing protection
 Facilitating body movement
• Study of tissues is called histology

3. Types of Tissue:
• There are four types of tissues in the body
including:
I. Epithelial Tissue (lining and covering)
II. Connective Tissue (support)
III.Muscle Tissue (movement)
IV.Nervous Tissue (control)

4. 4.Nervous tissue: Internal communication
• Brain, spinal cord, and nerves
3.Muscle tissue: Contracts to cause movement
• Muscles attached to bones (skeletal)
• Muscles of heart (cardiac)
• Muscles of walls of hollow organs (smooth)
1.Epithelial tissue: Forms boundaries between different
environments, protects, secretes, absorbs, filters
• Skin surface (epidermis)
• Lining of GI tract organs and other hollow organs
2.Connective tissue: Supports, protects, binds
other tissues together
• Bones
• Tendons
• Fat and other soft padding tissue

5. I.Epithelial Tissue:
• Epithelial tissue covers or lines every body
surface and body cavity
• Epithelium is composed of one or more layers
of closely packed cells between two
compartments

6. • There are two main types of epithelial tissue (by
location):
1. Covering and lining epithelia: On external and
internal surfaces
2. Glandular epithelia: Secretory tissue in glands

7. A. Covering and lining surfaces (a barrier):
Examples:
a. Skin
b. Epithelial cells (endothelium) lining blood vessels,
c. Mesothelium of peritoneal cavity (coelom)
Functions of Epithelia

8. D. Protection from the external environment
C. In some cases contractility (e.g. myoepithelium -
often associated with glands such as sweat and
mammary glands)
B. Regulation of materials and sensory information
passing between, into, or out of organs/tissues:
1. Absorption
2. Secretion
3. Sensation
4. Lubrication

9. Classification of Epithelia
a) Classification based on number of cell layers
into:
1. Simple epithelium (Have one layer)
2. Stratified epithelium (have >1 layers)

10. Figure 4.2a
2.Stratified
1.Simple
Apical surface
Basal surface
Apical surface
Basal surface

11. 1. Squamous: flat - very thin in cross-section.
2. Cuboidal: appear square in cross-section
(b) Classification based on cell shape:

12. 3. Columnar: appear rectangular (tall, column shaped)
in cross-section

13. (c)Luminal surface modifications:
1. Microvilli (Brush border)
2. Cilia
3. Stereocilia

14. I.Simple epithelia: epithelia consisting of one layer of cells:
1. Simple squamous: one layer of flattened cells covering
a surface, e.g. endothelium of blood vessels.
2. Simple cuboidal: one layer of cuboidal cells covering a
surface, e.g. epithelial lining of proximal and distal
convoluted tubules in kidney.
3. Simple columnar: one layer of columnar cells covering
a surface, e.g. epithelial lining of small intestine

15. 1.Simple Squamous Epithelium
Simple
squamous
lining the
walls of the
capillary
If it’s from a
mesothelial lining

16. 2.Simple Cuboidal Epithelium

17. 3.Simple Columnar Epithelium

18. II. Stratified epithelial types:
•Composed of more than one layer

19. 1.Stratified Squamous Epithelium
 Composed of many layers of cells (squamous in
shape)
 Deeper layers of cells appear cuboidal or columnar
 Its function is Protects underlying tissues in areas
subject to abrasion
 There are two types:
a. Keratinized: forms epidermis
b.Non-keratinized: forms moist lining of body
openings (esophagus, mouth, and vagina)

20. Stratified Squamous Epithelium
Non-keratinized vs. Keratinized

21. 2.Transitional Epithelium
• Transitional epithelium is made of cells that
can stretch. Cells are often bi-nucleate
• Cells look cuboidal when relaxed; look
squamous when stretched
• Found in lining of urinary bladder

22. Transitional Epithelium
Relaxed state
Stretched state

23. 3. Pseudostratified columnar
epithelium
• Looks stratified, but is actually one layer of
cells
• All cells in contact with basement membrane
• Stratified look because nuclei are at different
levels in cells
• May be ciliated or noncilia

24. Cilia
Basal cell
Nasal cavity lining
Pseudostratifie
d ciliated
columnar
epithelium
Columnar cell

25. 4.Stratified columnar epithelium: rare - e.g.
parts of urethra, some ducts of the paratid
gland. Only the cells at the free surface are
columnar.
5. Stratified cuboidal epithelium: rare, found in
some glandular ducts e.g. sweat glands, sub-
maxillary glands.

26. Cuboidal cell
Duct of sweat gland
LM100x
Stratified
cuboidal
epithelium
Male urethra
Columnar cell
Stratified
columnar
epithelium

27. Thanks for attention,,,