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Glandular Tissue
Curriculum : Phase 1/Semester2/TOB /Session 4
2017/2018
Lecturer : Dr. Rajaa Ali Al- Taee
Msc. PhD. Histology G.mail: [email protected]
Hammurabi Medical Collage / Babylon University
References:
• Histology Textbooks ‘Basic Histology’, Junqueira,13 th
Edition chapter 1,2,3.pp:1-72
• ‘Colour Atlas of Histology’ Gartner and Hiatt 5 th
Edition.
• http://www.histologyguide.com/
Glandular Tissue
Glandular Tissue
Objectives of the lecture:
1. Define a gland as an epithelial cell or aggregate of cells specialised for
secretion.
2. Classify glandular tissue, describing the meaning of the following
terms:
Exocrine or endocrine
Merocrine, apocrine or holocrine.
3. Describe the above mechanisms of secretion.
Glandular Tissue
4 . describe the mechanisms of endocytosis.
5. describe how endocytosis and secretion combine to give transepithelial transport.
6. explain the mechanism and importance of the glycosylation of newly synthesised
proteins in the Golgi apparatus.
7. describe the role of secretions in cell functions (e.g. in communication).
8. describe simple mechanisms of control of secretion (e.g. nervous, endocrine).
Glandular Tissue
Glandular Epithelium:
Glandular epithelium is more complex and varied than the epithelial
cells which cover surfaces or line tubules or vessels.
A gland is a single cell or a mass of epithelial cells adapted for
secretion.
Classification of Glands
• By destination
• By structure
• By nature of the secretion
• By the method of discharge
1. Exocrine glands
2. Endocrine glands:
• ductless glands
• Secretion
• Cells
By destination
Thyroid glandAdrenal gland
https://youtu.be/GUi84E6lUiY
Exocrine glands secrete into ducts or directly onto a free surface.
Their secretions include mucus, sweat, oil, ear wax and digestive
enzymes.
EXO = out side and crine = secret
Examples include :-
pancreas , stomach , sweat glands , salivary glands , mammary
glands , sebaceous glands , etc .
Endocrine glands - called “ductless glands” discharge their
secretions into the intracellular fluid, where it diffuses into the blood
stream. These secretions are hormones, or chemical messengers,
which regulate many body functions.
ee Examples include :-
Pituitary gland ,thyroid gland,adrenal gland,parathyroideees
exe
3. Mixed gland
(an exocrine and
endocrine gland)
The Pancreas.
Formation of glands from covering epithelia.
During fetal development epithelial cells proliferate and penetrate the
underlying connective tissue.
They may-or may not-maintain a connection with the surface
epithelium. When the connection is maintained, exocrine glands are
formed; with the connection lost, endocrine glands are formed.
Exocrine glands secrete to the body surface or gut via duct systems
formed from the epithelial connection.
Formation of glands from covering
epithelia.
The cells of endocrine glands, which secrete hormone) can be
arranged in cords or in follicles with lumens for storing the secretory
product.
From either the cords or follicles of endocrine cells, the secretory
product is released outside the cells and picked up by the blood
vessels for distribution throughout the body.
General structure of exocrine glands.
• Exocrine glands by definition have ducts that lead to an
organ or body surface.
• Inside the gland the duct runs through connecting septa and
branches repeatedly, until its smallest branches end in the
secretory portions of the gland.
Classification by
Structure
Secretory part: unicellular /
multicellular
acinar (alveolar) / tubular
coiled / branched *
Parotid gland: branched
Duct system:
1. Simple gland (single duct)
2. Complex gland (branched ducts)
Branching
ducts:
Main
↓
interlobular
↓
Intralobular
↓
Intercalary
Salivary gland
1-Exocrine glands:
Structural classification of exocrine glands:
1) unicellular glands
2) multicellular glands ↓
Goblet cell
Salivary gland
https://youtu.be/cdqLLa81-eE
Multicelular gland:
composed of :
1) An epithelial lined duct
2) A secretory unit called the acinus
3) Interstitial connective tissue
Classification by method of secretion:
Merocrine (exocytosis )
• secretion is released by exocytosis
of secretory granules (pancreas,
parotid gland, protein component
of milk from mammary gland).
Apocrine (pinch of )
• apical portion of cell along
with secretory product is
pinched off (lipid
component of milk from the
mammary gland).
Holocrine (rupture)
• entire cell is shed along with
secretory product (sebaceous
glands).
https://youtu.be/E5aJTpiwakI
• Classification by nature of secretion:
Ex: Salivary glands
• Classification by nature of
secretion:
mucous glands
Secretion: contains
mucopolysaccharides which collects in
the apical part of cell.
Cytoplasm: stain very lightly with H/E
stain
Nuclei: basally placed & flattened
(mucoid pushes the nuclei).
Secretion: thin, watery, rich in enzymes, protein in nature.
Cytoplasm: granular stain darkly & rich in rER.
Nuclei: rounded & basally placed.
serous glands
Sero-mucous gland
Mixed gland
muco-serous or mixed gland
Contain both serous & mucous secretory units.
Sometimes serous cells form crescentic caps on mucous acinicalled as serous demilunes.
According to above 4 criteria of classifications ,classify parotid
gland?
Endocytosis
• Engulfing
• Opposite of exocytosis
(merocrine secretion)
• Endo- & Exo-cytosis
(Transepithelial Transport)
https://www.youtube.com/watch?v=sBCDxPvu4F0&feature=youtu.be
Transepithelial Transport
• material endocytosed at one surface
• transport vesicle shuttles across cytoplasm
• material exocytosed at opposite surface
Golgi Apparatus:
Structure
Stack of disc-shaped cisternae
• One side of discs are flattened;
other concave
• Discs have swellings at their edges
• Distal swellings pinch off as
migratory Golgi Vacuoles
Golgy apparatushttps://youtu.be/3H5dSPQNlX8
Golgi Apparatus:
Function
• Packaging through condensation of contents
• Transport
• Adding sugars to proteins and lipids (Glycosylation)
Golgi Product Destinations
• Majority extruded in secretory vesicles
• Some retained for use in the cells (e.g. lysosomes)
• Some enters the plasma membrane (Glycocalyx)
Glycosylation & Specificity
• Branching sugars offer complex shapes for specific
interactions in the glycocalyx
• Destruction of this layer by enzymes alters many
specificity based properties of cells:
adhesion to substrates & neighboring cells
mobility of cells
communication with neighboring cells
contact inhibition of movement and division
Control of Secretion
• Nervous
• Endocrine control
• Neuro-endocrine control
• Negative feedback chemical mechanism
Q:Give one or more examples of glands for each type of above
controls?
Thank you for listen