CHAPTER 4
PART 2
STRATIFIED
GLANDULAR
DESCRIPTION
FUNCTIONS
PRESENCE
Figure 4.2e
... with keratin (keratinized)… DRY
KERATINIZED STRATIFIED
SQUAMOUS
DRY
moist
Stratified squamous epithelium
... without keratin (nonkeratinized)… MOIST
Stratified Cuboidal E.T.
Stratified Cuboidal E.T.
Stratified Columnar E.T.
• Several cell layers
with cuboidal basal
cells and columnar
superficial cells
• protection and
secretion
Figure 4.2f
Transitional E.T.
DESCRIPTION
FUNCTIONS
PRESENCE
Figure 4.2g
Transitional epithelium
... when the urinary bladder is full
GLANDULAR
EPITHELIA
Glandular Epithelia
• A gland is one or more cells that makes and
secretes an aqueous fluid
• Classified by:
– Type of product release –
– number of cells forming the gland
Endocrine Glands (-crine: to secrete)
• Ductless glands that secrete hormones
(exocytosis) into blood or lymph. They
travel to a target cell.
• Target cell secretions include:
Exocrine Glands
• More numerous than endocrine glands
• Secrete their products onto body surfaces
(skin) or into body cavities
• Examples include:
• Unicellular exocrine – goblet cell
• Multicellular exocrine - have a duct and
secretory unit
Goblet cell
Multicellular Exocrine Glands
• Classified
according to:
– Duct type
– Structure of
their secretory
units
Figure 4.3
Structural Classification of Multicellular
Exocrine Glands
Figure 4.4a-d
Structural Classification of Multicellular
Exocrine Glands
Figure 4.4e-g
Modes of Secretion
• Merocrine – “exocytosis”
• Holocrine – “apoptosis”
Figure 4.5
Merocrine secretion
Merocrine secretion
corresponds to the process of exocytosis. Vesicles open onto the
surface of the cell, and the secretory product is discharged from the
cell without any further loss of cell substance. Most glands – salivary,
pancreas (enzymes), eccrine sweat
Holocrine secretion designates the breakdown
and discharge of the entire secretory cell. It is
only seen in the sebaceous glands of the skin.
Apocrine secretion
designates part of the apical cytoplasm of the cells is lost together
with the secretory product. The continuity of the plasma membrane is
restored by the fusion of the broken edges of the membrane, and the
cell is able to accumulate the secretory product anew. This
mechanism was thought to be used by apocrine sweat glands, the
mammary glands and the prostate.