SN1
SHORT NOTE
5M
★ High-yield
Classify glands with examples. Describe the modes and nature of secretion.
Definition and Classification
Glands are epithelial cells specialised for secretion, developing as downgrowths from a surface epithelium.
| Basis | Types |
|---|---|
| Presence of a duct | Exocrine — secretes through a duct onto a surface; endocrine — ductless, secretes into the blood |
| Number of cells | Unicellular (goblet cell) or multicellular |
| Shape of the secretory unit | Tubular, acinar (alveolar), tubulo-acinar |
| Branching of the duct | Simple (unbranched duct) or compound (branched) |
Mode of Secretion
| Mode | Mechanism | Examples |
|---|---|---|
| Merocrine (eccrine) | Exocytosis; the cell remains intact | Most glands — salivary, pancreas, eccrine sweat glands |
| Apocrine | Apical part of the cell is shed with the secretion | Lactating mammary gland (lipid), apocrine sweat glands of the axilla |
| Holocrine | The whole cell disintegrates and becomes the secretion | Sebaceous gland; tarsal (Meibomian) gland |
Nature of the Secretion
| Type | Features | Examples |
|---|---|---|
| Serous | Watery, enzyme-rich; cells pyramidal with a round basal nucleus and basophilic cytoplasm; narrow lumen | Parotid, pancreas |
| Mucous | Viscid, glycoprotein-rich; cells with a flattened basal nucleus and pale, foamy cytoplasm; wide lumen | Sublingual, goblet cells, palatine glands |
| Mixed | Serous demilunes of von Ebner capping mucous acini | Submandibular |
Duct System of a Salivary Gland
- Myoepithelial (basket) cells lie between the acinar cells and the basal lamina, and contract to expel the secretion
- The striated duct is the histological signature of a salivary gland
Applied Aspects
- Sebaceous glands are holocrine and open into hair follicles; blockage with hyperkeratinisation and Propionibacterium acnes causes acne
- Sebaceous cyst follows blockage of the duct; it is attached to the skin and may show a punctum
- Cystic fibrosis affects all exocrine glands — the secretion is abnormally viscid, and the sweat chloride is diagnostically raised
- Pleomorphic adenoma arises from the ducts and myoepithelial cells, which is why it contains such varied tissue — epithelial, myxoid and cartilaginous
- Goblet cells increase in chronic bronchitis and decrease in the terminal bronchioles; their hyperplasia is the histological basis of the productive cough
All questions in General Histology
- Q1Classify epithelium with sites and functions. Describe its surface specialisations, cell junctions and basement membrane. ★
- Q2Describe the cells, fibres and ground substance of connective tissue. Classify connective tissue with examples. ★
- Q3Compare the three types of muscle histologically. Describe the structure of skeletal muscle and the sarcomere. ★
- Q4Describe the structure of a neurone and classify neurones. Describe the neuroglia and add a note on nerve degeneration and regeneration. ★
- Q5Describe the histology of cartilage and bone. Add a note on the structure of blood vessels. ★
- SN1Classify glands with examples. Describe the modes and nature of secretion. ★
- SN2Describe the histology of the lymph node, spleen and thymus. ★
- SN3Describe the histology of the skin. Differentiate thick from thin skin. ★
- SN4Describe the preparation of a histological section and the common stains used. ★
- SN5Classify cell junctions and describe their structure and functions. ★
- SN6Describe the ultrastructure of a typical cell and the cytoskeleton.
- SN7Describe the histology of blood with its formed elements. ★