Histology of Glands 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. http://www.kcmetro.cc.mo.us/maplewoods/Biology/Bio110/Piks/pik14.html

Multicellular glands Formed by invagination of epithelial layer in deeper tissue to form a diverticulum: Proximal part forms duct. Distal part forms secretory element.

Endocrine (ductless): pour their secretions directly into the blood. 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: Compound glands: Simple tubular Compound tubular Simple coiled tubular Simple branched tubular Simple branched alveolar Compound glands: Compound tubular Compound alveolar Compound tubulo- alveolar

Simple glands http://www.kcmetro.cc.mo.us/maplewoods/Biology/Bio110/Piks/pik14.html

Compound glands

Sweat glands Fundic glands of stomach Meibomian glands Crypt of Lieberkuhn Brunner glands Submandibular gland 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 http://www.stanford.edu/group/Urchin/GIFS/exocyt.gif

Modes of secretion Merocrine: secretion by exocytosis

Modes of secretion Merocrine: secretion by exocytosis Apocrine

Merocrine: secretion by exocytosis Modes of secretion Merocrine: secretion by exocytosis Apocrine: secretion by loss of cytoplasm

Merocrine: secretion by exocytosis Modes of secretion Merocrine: secretion by exocytosis Apocrine: secretion by loss of cytoplasm Holocrine

Merocrine: secretion by exocytosis 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.

Salivary glands

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 Mucous cell EM LM

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