it describes the microanatomy of skin and its appendages in a concise format. it will give the overview of the integumentary system of our body and largest organ of our body.

1. Histology of Skin and its
Appendages.
(Integumentary system)
To
MBBS unit-4
Dr. Laxman Khanal
Asst. Professor, department of Human Anatomy
BPKIHS, Dharan, Nepal

2. Q. Variation in thickness of epidermis of skin (0.1 to 1mm) is mainly due to
variation in:
a. Stratum corneum
b. Stratum lucidum
c. Stratum granulosum
d. Stratum spinousm
Q. ‘Superficial fascia’ described in gross anatomy is equivalent to which
of the following histological layer?
a. Stratum basale + stratum spinousm
b. Whole of the epidermis of skin
c. Dermis
d. Hypodermis

3. Q. Epidermis of the skin is attached to the dermis with the help of:
a. Desmosome
b. Hemi desmosome
c. Gap junctions
d. Tight junctions
Q. Image shows the case of acne vulgaris.
Which glands are involved in this case?
a. Eccrine sweat gland
b. Apocrine sweat gland
c. Holocrine gland
d. Glands of Moll

4. Skin + its appendages= integumentary system
Skin (Cutis): covers the entire outer surface of the body.
Structurally, the skin consists of two layers.
These layers have different
• Functions
• Histological appearance
• Embryological origin
Beneath these two layers, layer of loose connective tissue,
the hypodermis or subcutis is found which binds the skin to underlying
structures. It is equivalent to superficial fascia.
Appendages of skin
• Hair
• Nail
• Sebaceous gland
• Sweat gland

5. Epidermis
• The epidermis is a keratinized stratified squamous epithelium.
• The main function of the epidermis is to protect the body from harmful
influences from the environment and against fluid loss.
• Five different histological layers constitute the epidermis.
1. Stratum basale (Layer of stem cells)
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum (Keratinized cells)
Cells of the epidermis of the skin will at some time of their life (3-4 week)
keratinize and are collectively also called keratinocytes.
Cells of epidermis of skin
1. Keratinocytes
2. Nonkeratinocytes

6. Functions of skin
• Barrier
• Drug absorption: eg. Nicotine patch, Steroids
• Immunologic functions
• Homeostasis
• Sensory information
• Endocrine functions
• Excretory function

8. Thick Skin Thin SkinThickness (mm) 0.1-0.20.5-4.5
Sites
S. Lucidum ×
Epidermal RidgesWell developed poorly developed
Hair follicle
Arrector pili
Sebaceous gland
Sweat gland
Sensory receptors
×
×
×



More Few
More Few

9. Stratum Basale (Basal Layer)
• It is responsible for the continuous regeneration of
the other layers of the epidermis.
• Cells are attached to the basement membrane by
Hemidesmosome.

10. Stratum spinosum (Prickle cell layer)
• Polyhedral cells with prominent nucleoli.
• Synthesize the intermediate filament: cytokeratin.
• Cytokeratin aggregate and form tonofilaments.
• Tonofilaments give resistance to abrasion.
• Binding of tonofilaments to desmosome give
spined appearance.

11. Stratum Granulosum
• Transition between metabolically active cell layers
and dead cell layers.
• Cells progressively flattened and undergo apoptosis.
• Presence of basophilic keratohyaline granules.
• Tonofilaments + KHG = Keratin
• Presence of lamellar bodies (Odland bodies) makes
it water resistant.
• Keratohyaline granule
• Lamellar bodies (Odland bodies)

12. Stratum lucidum
• Only found in thick skin.
• Cells are translucent in appearance.
Stratum corneum
• 20-25 cell layer thick.
• Made up of dead keratinocytes (Corneocytes).
• Cells are arranged like ‘brick in the wall’
• Epidermal turnover time: 52-75 days

13. Keratinocyte
Melanocyte
Langerhans cell
Merkel’s cell
Cells of epidermis of the skin

14. • Source: Neural Crest Cell
• Place: Basal layer
• Function: color of skin and hair
• More numerous in area exposed to sunlight.
Epidermal melanin Unit:
36 keratinocytes associated with
each melanocytes.

15. Langerhans cells (antigen presenting cells)
• Langerhans cells are dendritic cells of the skin.
• Derived form mesenchymal cells of bone marrow
• Most numerous in stratum spinosum
• Have branched shape &central nuclei
• Presence of Birbeck’s granules

16. Merkel’s cell
• Found in basal cell layer
• Originated from keratinocytes
• Function as touch receptors (slowly adapting)

17. Dermis
• Overall thickness of skin depends upon
thickness of dermis.
• Mainly consists of collagen and elastic
fibers.
• Responsible for tone and texture of the
skin.
• Neurovascular structures and skin
appendages are found in dermis.
• It has two layers:
1. Papillary layer – toward epidermis
2. Reticular layer- toward hypodermis

18. Papillary layer
Reticular layer
• The collagen and elastic fibers are
not randomly oriented but form
regular lines of tension in the skin
called Langer’s lines.
• Skin incisions made parallel to
Langer’s lines heal with the least
scarring.

19. Blood circulation of skin
Deep plexus
(cutaneous plexus)
superficial plexus
(sub-papillary plexus)
Large blood vessels

20. Glomus bodies
A/C to circulation
A. Apical skin
B. Non apical skin

21. Skin appendages
• These are developed as a result of down growth of the epidermis of
skin toward dermis and hypodermis.
• It includes
1. Hair follicle: give rise to the hair
2. Sebaceous gland
3. Eccrine sweat gland
4. Apocrine sweat gland
5. Nail

22. Skin appendages
Hair cycle
Anangen phase- fast growing phase
Catangen phase- involution phase
Telogen phase- rest phase
Types of hair
1. Laungo hairs
2. Vellus hairs
3. Terminal hairs

23. Eponychium
Nail body
Free edge
Lunula
Nail root
Hyponychium
Epidermis
Dermis
Nail bed
1. Basal layer
2. Spinous layer
Nail plate
(keratinized)
Nail matrix
(site of nail growth)

24. Sweat gland Sebaceous gland
Open into hair follicle
Active only after pubertyOpen into surface of skin
Active throughout life
Sweat gland

25. which gland ?
Skin appendages

26. Pilosebaceous unit