1. CONNECTIVE AND SUPPORTIVE TISSUES
THE GROUND TISSUES
EPITHELIAL TISSUES
CONNECTIVE AND SUPPORTIVE TISSUES
MUSCLE TISSUES
NERVOUS TISSUE

2. HISTOLOGY 1.3.: EPITHELIAL TISSUES 1. SURFACE EPITHELIA
Diverse group of tissues, cover or line external and internal body surfaces,
cavities and tubes, thus, function as interfaces between different
biological compartments.
Epithelia mediate a wide range of activities:
selective diffusion
absorption
secretion
physical protection
sensory function
Origin of the epithelial tissues:
ectoderm (corneal epithelium, epidermis of skin, glands)
entoderm (alimentary tract, intestinal glands, liver, pancreas)
mesoderm (kidney, male and female reproductive system,
endothelium, mesothelium)

3. Blood supply of the epithelial tissue:
normally it is avascular
exception: pharyngeal epithelium of frog
urinary bladder of rabbit
Nerve supply of the epithelial tissue:
it is an innervated tissue containing free nerve endings
and nerve endings associated to specialized cells
of sensory function
Tissue components of epithelial tissues:
Cells (squamous, cuboidal, columnar) closely packed
Intercellular matrix is reduced to the glycocalyx of the adjacent cells

4. THE POLARITY OF THE EPITHELIAL CELLS

5. Membrane modifications of the apical surface of epithelial cells: cilia
Membrane specialization of the basal
membrane surface of epithelial cells:
basal striation + basal lamina (green
arrows)

6. CLASSIFICATION OF EPITHELIAL TISSUES
FUNCTIONAL BASIS:
SURFACE EPITHELIA
GLANDULAR EPITHELIA
ABSORPTIVE EPITHELIA
PIGMENT EPITHELIA
SENSORY EPITHELIA

7. SURFACE EPITHELIA:
Further classification: on the basis of the number of cell layers
on the basis of the shape of the cells
Simple epithelia: a single layer of cells
simple squamous
simple cuboidal
simple columnar
Pseudostratified epithelia: single layer of cells, with nuclei in more than one layer
pseudostratified columnar
transitional
Stratified epithelia: several layers of cells on top of each other
stratified squamous (non-keratinized, keratinized)
stratified cuboidal
stratified columnar

8. Simple epithelia: simple squamous epithelium

9. OCCURRENCE OF SIMPLE SQUAMOUS EPITHELIUM IN THE BODY
PULMONARY ALVEOLI
PARIETAL LAYER OF BOWMAN’S CAPSULE – KIDNEY
THIN SEGMENTS OF HENLE’S LOOP – KIDNEY
RETE TESTIS
INNER ASPECT OF THE TYMPANIC MEMBRANE IN THE MIDDLE EAR
ENDOTHELIUM LINING THE BLOOD AND LYMPHATIC VESSELS
SEROUS MEMBRANES LINING BODY CAVITIES AND INTERNAL ORGANS

10. SOME EXAMPLES: Cross-section of the simple squamous epithelium:
Kidney glomerulus, Bowman’s capsule
Mesothelial lining of the peritoneal
cavity: „fried-egg” appearance

11. Endothelium: lining of the blood vessels
and heart (arrows). Note the flattened nuclei
The alveoli of the lung
are composed
of similar cells

12. Simple epithelia: simple cuboidal epithelium

13. OCCURRENCE OF SIMPLE CUBOIDAL EPITHELIUM IN THE BODY
LINING THE FOLLICLES IN THE THYROID GLAND
THE SURFACE OF OVARY
CHOROID PLEXUS – BRAIN
THE CAPSULE OF LENS – EYE
PIGMENTED EPITHELIUM OF RETINA – EYE
DUCTS OF MANY GLANDS
SECRETORY ACINI OF MANY GLANDS
SEVERAL SEGMENTS OF KIDNEY TUBULES

14. Kidney: proximal and distal convoluted tubules, collecting tubules are
lined by simple cuboidal epithelium
Proximal tubules in cross-section and in longitudinal section (arrow)

15. The follicles of the thyroid gland are formed by simple cuboidal cells

16. Simple epithelia: simple columnar epithelium

17. OCCURRENCE OF SIMPLE COLUMNAR EPITHELIUM IN THE BODY
DIGESTIVE TRACT FROM THE CARDIA OF THE STOMACH TO THE ANUS
LARGER EXCRETORY DUCTS OF SOME GLANDS
UTERUS (CILIATED) IN HUMAN
OVIDUCT (CILIATED) IN HUMAN
PULMONARY BRONCHI (CILIATED) - LUNG
PARANASAL SINUSES – NOSE
CENTRAL CANAL OF SPINAL CORD (EPENDYMA)

18. Pseudostratified epithelia: pseudostratified columnar epithelium

19. OCCURRENCE OF PSEUDOSTRATIFIED COLUMNAR EPITHELIUM
THE MALE URETHRA
EPIDIDYMIS – MALE GENITAL ORGAN
TRACHEA (CILIATED)
PRIMARY BRONCHI (CILIATED) – LUNG
THE AUDITORY TUBE
PART OF THE TYMPANIC CAVITY – EAR
LACRIMAL SAC

20. Transitional epithelium, or urothelium

21. Urinary bladder, fixed in empty
state: note the thickness of the urothelium: 8-10 cell layers
(arrow)
Urinary bladder, fixed in full
state: note the thickness of the
urothelium: 4-5 cell layers
(arrow)

22. The luminal surface of the umbrella cells is covered by a specialized
cell membrane called calyx, or crusta

23. Stratified epithelia: stratified squamous non-keratinized epithelium
Layers from the basal lamina to the surface:
stratum basale/germinativum: columnar cell layer with mitotic division
stratum spinosum: cuboidal poligonal cell layers with many desmosomes
stratum planocellulare: fusiform or flattened cell layers
Occurrence: cornea, internal body surfaces, e.g. esophagus (see above)

24. Stratified epithelia: stratified squamous keratinized epithelium4. 1. 2. 3.
5. Str. corneum
Layers from the basal lamina to the surface: 1. stratum germinativum,
2. stratum spinosum, 3. stratum granulosum (fusiform cells with keratohyalin granules),
4. stratum lucidum (flattened layer with eleidin), 5. stratum corneum (dead cell layer)
Occurrence: epidermis of skin, beginning and end-portions of the gastrointestinal tract

25. (cisterna lactis of teat- not shown)
STRATIFIED CUBOIDAL EPITHELIUM
VERY RARE: TWO ROWS OF CUBOIDAL CELLS ON TOP OF EACH OTHER
Duct of the sweat gland
(cisterna lactis of teat- not shown)
STRATIFIED COLUMNAR EPITHELIUM:
Cavernous urethra,
Large excretory ducts
of some glands,
Larynx (ciliated),
Fetal esophagus
(transiently)