Transcript Document

12.02.2015
Dr. Archana Rani
Associate Professor
Department of Anatomy
KGMU UP, Lucknow
Introduction
 A gland is an organ that consists of specialized
secretory cells.
 Secreted material is usually a liquid.
 Epithelial in origin.
 Present in singly or in groups.
 Unicellular or Multicellular
 2 types:
 Exocrine
 Endocrine
Unicellular glands
 Single cell distributed among non-secretory cells.
Multicellular glands
 Formed by invagination
of epithelial layer in
deeper tissue to form a
diverticulum:
 Proximal part forms
duct.
 Distal part forms
secretory element.
Exocrine: pour their
secretions onto an
epithelial surface,
directly or through
ducts.
Endocrine (ductless):
pour their secretions
directly into the blood.
Classification of exocrine glands
 Based on shape & branching pattern of duct
 Based on mode of release of their product
 Based on the nature of their secretion
Classification based on shape & branching
pattern of duct
 Based on shape of secretory units (tubular or alveolar)
& branching pattern of ducts.
 2 types:
Simple
Compound
Contd…
Simple glands:
 Simple tubular
 Simple coiled tubular
 Simple branched tubular
 Simple branched alveolar
Compound glands:
 Compound tubular
 Compound alveolar
 Compound tubuloalveolar
Simple glands


Compound glands
Crypt of Lieberkuhn
Brunner glands
Sweat glands
Submandibular gland
Fundic glands of stomach
Meibomian glands
Mammary gland
Classification based on mode of secretion
• Merocrine: secretion is released by
exocytosis of secretory granules
(pancreas, parotid gland, protein
component of milk from mammary
gland).
• Apocrine: apical portion of cell along
with secretory product is pinched off
(lipid component of milk from the
mammary gland).
• Holocrine: entire cell is shed along
with secretory product (sebaceous
glands).
• Modes of secretion
• Modes of secretion
Merocrine
• Modes of secretion
Merocrine: secretion by
exocytosis
• Modes of secretion
Merocrine: secretion by
exocytosis
Apocrine
• Modes of secretion
Merocrine: secretion by
exocytosis
Apocrine: secretion by loss
of cytoplasm
• Modes of secretion
Merocrine: secretion by
exocytosis
Apocrine: secretion by loss
of cytoplasm
Holocrine
• Modes of secretion
Merocrine: secretion by
exocytosis
Apocrine: secretion by loss
of cytoplasm
Holocrine: secretion
through loss of entire cell
Classification based on the nature of
secretion
• Serous glands
• Mucous glands
• Mixed glands
Serous glands
 Secretion: thin, watery,
rich in enzymes, protein in
nature.
 Cytoplasm: granular (stain
darkly from pink to dark
purple with H/E stain) &
rich in rER.
 Nuclei: rounded & basally
placed.
Mucous glands
 Secretion: contains
mucopolysaccharides
which collects in the apical
part of cell.
 Cytoplasm: stain very
lightly with H/E stain &
therefore gives empty look.
 Nuclei: basally placed &
flattened (mucoid pushes
the nuclei).
Mixed glands
 Contain both serous &
mucous secretory units.
 Sometimes serous cells
form crescentic caps on
mucous acini called as
serous demilunes.
Major glands
 Lie completely outside
the alimentary tract &
connected to it by an
excretory duct.
 Compound alveolar or
tubuloalveolar in type.
 Parotid, submandibular,
sublingual.
Minor glands
 Small salivary glands situated in the mucous
membrane of:
Lip (labial)
Cheeks (buccal)
Soft palate (palatine)
Tongue (lingual)
Functions of Salivary glands
 Secrete saliva composed of water, mucus, proteins,
salts, salivary amylase (ptyalin), immunoglobulins
(IgA) & lactoperoxidase.
 Serves to moisten food.
 Lubricates & moistens oral mucosa and lip.
 Initiates the digestion of carbohydrates.
Basic organization
Different types of acini
Mucous
Serous
Mixed
Features of serous & mucous cells
Serous cell
EM
LM
Mucous cell
Differences between serous & mucous acini
Differences between serous & mucous cells
Parotid gland
Submandibular gland
Sublingual gland
References
1. diFiore’s Atlas of Histology with functional
Correlations, 12th Edition.
2. Textbook of Human Histology. Inderbir Singh, 1st
Edition.
3. Textbook of Histology. GP Pal, 3rd Edition.
MCQ
1. All are major salivary glands except:
a) Palatine
b) Parotid
c) Submandibular
d) Sublingual
MCQ
2. Holocrine type of secretion is a feature of:
a) Mammary gland
b) Parotid gland
c) Sebaceous gland
d) Pancreas
MCQ
3. Sweat gland is an example of:
a) Simple tubular gland
b) Simple coiled tubular gland
c) Simple branched tubular gland
d) Simple alveolar gland
MCQ
4. All are true about serous acini except:
a) Smaller in size
b) Stain dark
c) May present as demilune
d) Wide lumen
MCQ
5. Expelling of secretion through contraction
is a feature of:
a) Serous cell
b) Mucous cell
c) Serous demilune
d) Myoepithelial cell