Appendageal Glands and Nerves A. GLANDS| | | | | | Presence of eosinophilic cuticle helps distinguish eccrine duct from coil histologically | | | | | |
|
- Most important function is to regulate body temperature through evaporative heat loss
- Composed of three sections:
- Acrosyringium: intraepidermal spiral duct opening to surface of skin
- Straight duct: within dermis and consisting of double layer cuboidal epithelium lined by eosinophilic cuticle on luminal side
- Secretory eccrine coil: within deep dermis/subcutaneous fat and consists of two different cells (glycogen-rich, pale cells, and smaller darker cells) which appear to fit together in one layer, outer portion contains myoepithelial cells
- Positive for S100, keratin, and carcinoembryonic antigen (CEA)
- Found everywhere except: clitoris, glans penis, labia minora, external auditory canal, and lips
- Eccrine glands possess cholinergic innervation (acetylcholine) but paradoxically derived from sympathetic outflow (which typically uses norepinephrine, not acetylcholine), thus functionally cholinergic but anatomically sympathetic; merocrine secretion
Apocrine Glands- Generally confined to axillae, breast (mammary gland), anogenital region, external auditory canal (ceruminous gland), and eyelids (Moll’s gland)
- Secretion via decapitation (portion of cell pinched off and enters lumen)
- Responds mainly to sympathetic adrenergic stimuli
Sebaceous Glands- Formed initially as outgrowth from upper portion of hair follicle; contains lobules of pale-staining cells characterized by lipid vacuoles; holocrine secretion with distention of sebocytes (filled with lipid vacuoles) until shed into lumen
- Found throughout skin except palms and soles
- Always associated with follicles except following locations (‘free’ sebaeceous glands):
- Gland of Zeis → found on superficial eyelid margin (near Moll’s gland)
- Meibomian gland → tarsal plate of eyelids (behind Moll’s gland)
- Montogomery tubercle → nipple and areola
- Tyson’s gland → external fold of prepuce (genitalia)
- Fordyce spot → vermilion border of the lips and buccal mucosa
- Gland under adrenergic hormonal control; enlargement at puberty due to ↑ androgens
- Lipid composition of sebum: 57% triglycerides, 25% wax esters, 15% squalene, <3% cholesterol and cholesterol esters
B. NERVES- Sensory receptors divided into corpuscular (which contains non-nervous components) and free nerve endings; positive for S100 immunostain and contains neurofilaments
- Two main types of corpuscular endings: nonencapsulated (merkel cells) and encapsulated (Meissner’s and Pacinian corpuscles)
- Pain detected by nociceptors via either Aδ-type fibers (large) or C-type fiber
Nonencapsulated Endings- Free nerve endings : rapidly adapting receptors; majority consist of nonmyelinated C-type fibers and some myelinated Aδ-type fibers; terminal endings within epidermis and papillary dermis; mainly detects touch, pressure, and pain
- Merkel cells : found in basal layer and makes close contact with sensory nerve terminal (Merkel disc), detects touch
Encapsulated Endings- Vater-Pacini (Pacinian) corpuscle
- Rapidly adapting mechanoreceptor resembling an onion; found in deep dermis/subcutis
- Detects deep pressure and vibration; increased concentration in palms/soles, nipples, and anogenital region
- Meissner’s corpuscle
- Elongated mechanoreceptor detecting light touch (resembles pine cone); located just below DEJ (dermal papillae)and highest density in palmoplantar skin
- Ruffini corpuscle
- Thin, encapsulated, fluid-filled slow adapting receptor; found in deep dermis and detects continuous pressure
- Mucocutaneous end organs (Krause end bulbs)
- Mucocutaneous receptors found on vermilion lip, perianal region, glans penis, clitoris, and labia minora
|
