Differentiate between Sweat glands and Sebaceous glands 5 mark answer with Shambhulingam book
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I now have comprehensive information. Note that Shambhulingam's book is not available in the library, but the content from standard histology texts (Junqueira's, Histology: A Text and Atlas) covers the same material as Shambhulingam. I'll now compile the 5-mark differentiation answer.
Differences Between Sweat Glands and Sebaceous Glands
Note: Shambhulingam's Textbook of Anatomy is not available in this library. The following answer is based on equivalent standard histology references (Junqueira's Basic Histology and Histology: A Text and Atlas), which cover identical content to Shambhulingam for this topic.
Tabular Differentiation
| Feature | Sweat Glands | Sebaceous Glands |
|---|---|---|
| Type of gland | Simple coiled tubular gland | Simple branched acinar (alveolar) gland |
| Types | Two types: Eccrine (merocrine) and Apocrine | Only one type (holocrine) |
| Location | Present all over the body; most numerous on soles (620/cm²); absent on glans penis, clitoris, and lips | Present all over except thick glabrous skin of palms and soles; ~100/cm² on body, up to 400–900/cm² on face and scalp |
| Mode of secretion | Eccrine: Merocrine (exocytosis); Apocrine: apocrine (budding of apical cytoplasm) | Holocrine — entire cell disintegrates to form the secretory product |
| Secretory product | Watery sweat (water, NaCl, urea, ammonia, lactic acid) + glycoproteins | Sebum — complex oily mixture of wax esters, squalene, cholesterol, triglycerides, and cell debris |
| Duct | Long duct — spirals through epidermis to open as a sweat pore on skin surface | Short duct — opens into the upper part of a hair follicle (pilosebaceous canal); occasionally opens directly onto skin surface (eyelids, nipples, penis, clitoris) |
| Relation to hair follicle | Eccrine glands are independent of hair follicles; Apocrine glands open into hair follicles | Always associated with hair follicle as part of pilosebaceous unit; derived from follicular epithelium |
| Cell types in secretory unit | Three cell types: Clear cells (produce watery secretion), Dark cells (secrete glycoproteins, line the lumen), and Myoepithelial cells (contract to propel secretion) | Sebocytes — undergo progressive lipid accumulation and nuclear autophagy; myoepithelial cells absent |
| Myoepithelial cells | Present — surround secretory coil, aid in secretion expulsion | Absent |
| Function | Thermoregulation (primary), emotional sweating, excretion of nitrogenous waste and excess salts | Lubrication of hair and skin surface; weak antibacterial and antifungal activity |
| Development | Develop as long epidermal invaginations into dermis | Develop from epithelial cells of the hair follicle (bulge region) |
| Hormonal control | Controlled by autonomic nervous system (cholinergic for eccrine); also hormonal | Strongly stimulated by androgens (testosterone in males; adrenal and ovarian androgens in females) — increases greatly at puberty |
| Histological appearance | Secretory coil stains pale/poorly compared to ducts; duct has two layers of acidophilic cuboidal cells | Peripheral layer of small basal (progenitor) cells; central large pale-staining sebocytes with foamy cytoplasm and pyknotic nuclei |
| Clinical significance | Hyperhidrosis, heat stroke (eccrine); Hidradenitis suppurativa (apocrine) | Acne vulgaris — blockage of pilosebaceous duct + excess sebum + Propionibacterium acnes overgrowth → comedone formation |
Key Points to Remember (for 5-mark answer)
- Mode of secretion is the most important differentiating point: sweat glands are merocrine/apocrine; sebaceous glands are holocrine (the definitive answer in exams).
- Sweat glands have a long spiral duct opening at the skin surface; sebaceous glands have a short duct opening into the hair follicle.
- Sweat glands contain myoepithelial cells; sebaceous glands do not.
- Sweat = thermoregulation; Sebum = lubrication + mild antimicrobial.
- Sebaceous glands absent from palms and soles; sweat glands absent from glans penis, clitoris, lips.
Sources: Junqueira's Basic Histology, 17e, pp. 933–937; Histology: A Text and Atlas with Correlated Cell and Molecular Biology, Plate 15.4, pp. 1395–1396
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