The skin consists of a
keratinised squamous epithelium (epidermis) and a fibroelastic
connective tissue layer (dermis) separated by a basement membrane zone
The dermis is attached to underlying
loose connective tissue (subcutaneous layer or hypodermis)
which contains primarily adipose tissue.
The junction between the epidermis and dermis is characterised by
downward folds of the epidermis called epidermal ridges or rete which
interdigitate with upward projections of the dermis called dermal
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum corneum
Specialized cell of the epidermis:
2. Langerhans cells
3. Merkel cells
Epidermal appendages :
Sweat glands (eccrine and apocrine glands)
Regional variation of skin:
The terminal hair follicles extend into subcutaneous fat.
Numerous piloseaceous units are present. Sebaceous glands are
particularly large and prominent on the nose.
The epidermis is thin and there are glands of Moll in the
Thicker reticular dermis than elsewhere.
Palms and soles -
The stratum corneum is thick and compact.
There is no basket weave pattern of keratin and no pilosebaceous units are present in the dermis.
Thick walled venules in the papillary dermis due to
effects of gravity & stasis.
Genitalia and areola -
Contain muscle fibres.
Some normal features such as keratinization & dermal thickening
occur in inflammatory conditions therefore site of the
biopsy should be taken into account before making any diagnosis.
The hair follicles
are cylindrical downgrowth of surface epithelium.
The pilosebaceous unit consists of follicle, attached smooth muscle (arrector pili muscle) and a sebaceous gland.
Hair follicle is divided into 3 regions:
1. Lower segment (bulb & suprabulb)-
from the base of the hair follicle to the insertion of the arrector
2. Middle segment (isthmus) -
Extends from the insertion of the
arrector pili muscle to the entrance of the sebaceous gland duct.
3. Upper segment (infundibulum)-
Entrance of the sebaceous gland duct
to the follicular orifice.
The hair bulb encloses dermal papilla.
The hair follicle consists of five concentric layers:
4. Internal root sheath
5. External root sheath