Cytology, embryology, General histology
1. Lecture 3Cytology, embryology,
1. Epithelial tissue.
2. Definition• Tissues -- groups of cells organised
to perform one or more functions.
3. Please, note and write down:4 basic types of tissues:
• Epithelial (Epithelium)
There are two main types of Epithelial Tissue:
1. Covering and lining
Covering and lining epithelia lie on the free
- cover outer body surfaces (i.e. skin) and
- line inner body surfaces:
-- lumen of hollow organs (i.e. intestine)
-- cavities (i.e. peritoneal cavity),
-- blood vessels,
-- ducts (in glands),
-- tubules (in kidneys).
6. Characteristics1. Consists of cells only (there is no matrix).
2. Cells tightly appose in sheets.
3. Cells rest on the basement membrane.
Note: connective tissue lie under the basement membrane
7. Importance :• Epithelium create a selective barrier
between the organism and its external
any substances must pass through the epithelial
cell, not between them.
8. Please, note and write down:Two types of surface epithelia:
• epithelium is simple, when it is one cell
• and stratified when it is two or more cell
9. Maine functions• protection
• diffusion or absorption or excretion =
10. Another functionsCharacteristics.
3. polarity - cells have 2 surfaces :
the apical or free surface - towards the lumen or
the basal surface, closest to the basement
4. Epithelia are avascular, do not contain blood
vessels, but are nourished by diffusion of
substances from capillaries in underlying
5. It is frequently mitotically active
11. Characteristics.Shape of cells:
The morphology of the epithelium
correlates with its function:
• - Epithelia involved in secretion or absorption
are typically simple.
• -- Stratified epithelia usually impermeable
– lines blood vessels (endothelium), closed body
cavities (mesothelium), alveoli in the lungs
– Function: controls diffusion, osmosis and filtration
14. Please, note and write down: The morphology of the epithelium correlates with its function:Simple Cuboidal Epithelium
• lines tubules and ducts
• Lines stomach, intestine.
• Usuallly has microvilli = finger-like projections of cell
• Function – absorption.
• Single cell layer
• All cells attach to
basement membrane but
not all reach free surface
• Nuclei at varying depths
Several cell layers thick,
Surface cells flat
Keratinized = surface
cells dead and filled with
– Example - Skin
• Nonkeratinized = no
keratin in moist, living
cells at apical surface
– Example - Cornea
• Surface cells cuboidal
Lie in sweat gland ducts,
• Surface cells columnar
• Line very large ducts of gland, male urethra
• Surface cells varying in shape from round to flat if
• Lines hollow organs of the urinary tract that expand
• - form glands.
• Function – secretion = synthesis and
releasing of substances.
exocrine and endocrine.
• Exocrine glands
secrete through ducts
or directly onto an
surface (skin or cavity
of inner organs).
• Endocrine secrete
hormones into the
23. Please, note and write down: !! The morphology of an epithelium often correlates with its function:By cell number
Ex.: Goblet cell
secrete mucus and lubricate small and large intestine,
24. GLANDULAR EPITHELIATwo type of secretion
of Exocrine Glands
• Mucous - viscous, slimy
(mucus lines and lubricates cavities of
all inner hollow organs)
• Serous - watery
Ex.: exocrine pancreas (enzymes),
Fluid in serous cavities, joints.
25. GLANDULAR EPITHELIA
26. There are two types of gland in the body: exocrine and endocrine.3 types of secretion mechanism:
Merocrine (= eccrine)
27. By cell numberMerocrine (most common):
Secretory granules fuse
with the apical
and are secreted
into the lumen of
28. 2 portions of gland: Parenchyma and StromaApocrine
(ex.: lactating mammary gland (fat droplet))
small portion of apical cytoplasm with
secretory granules is pinched off
29. Two type of secretion of Exocrine GlandsHolocrine - ex: Sebaceous glands of skin
the cell fills with its secretory product (lipids),
dies and disintegrates, releasing its product.
31. Classification of Exocrine Glands by type of secretionMechanisms of Glandular Secretion
32. 3 types of secretion mechanism:A Structural Classification of Exocrine Glands
33. Merocrine (most common):A Structural Classification of
• By branching of duct exocrine glands may
be: simple (b-) or compound (b+)
• By shape of secretory ends – tubular or
• By branching of secretory ends exocrine
glands may be: branched (b+) or nonbranched (b-)