Deep to the epidermis lies the dermis. It is a thick layer of connective tissue consisting of collagen and elastin which allows for skin's strength and flexibility, respectively. The dermis also contains nerve endings, blood vessels, and adnexal structures such as hair shafts, sweat glands, and sebaceous glands.

1. Histology of Skin & Applied Anatomy
Dr Mathew Joseph MBBS, MD(AIIMS), BCC(Palliative Medicine)
Assistant Professor
Department of Anatomy
Amala Institute of Medical Sciences
Thrissur

3. Skin Facts
• The human skin (cutis) - outer covering of body & is
continuous with mucous membrane in the region of
mouth, nose, urogenital organs & anus.
• The mass of skin an adult accounts for approx 5 %
while together with subcutaneous fat for about 16 to
18 per cent of the total body mass.

4. • Largest sensory organ
• Weighs 4 kg
• Thickness – 0.3 – 3 mm
• Integumentary system
• Rule of nine
• Surface area: 1.5-2.0 sq meters
• Growth rate of nail: 0.1mm per
day
• Growth rate of hair: 1.5-2.2 mm
per week
• Life span of hair:
Eyelashes, axilla- 4 months
Scalp – 4 years

5. •The skin surface is covered with hairs over a
great area.
•The areas devoid of hairs are lips (vermilion
border), palms & soles, palmar surface of
fingers & plantar surface of toes, glans penis,
inner surface of prepuce, & inner surface of anus.

6. Histology of Skin

7. Layers of Skin
Epidermis:
Composed of keratinized
stratified squamous epithelium.
Dermis:
Papillary region composed of
loose connective tissue.
Reticular region composed of
dense irregular connective tissue.
Hypodermis:
Composed of areolar tissue with
abundant adipocytes.

8. Epidermis

10. Germinative layer
(stratum basale or stratum
germinativum)
• It consists of a single layer of columnar cells arranged
like a palisade.
• Between these cells slit-like spaces called intercellular
bridges.
• Among the cells of germinative layer localize
melanocytes, which produce melanin.
• Skin color straightly depends on the amount of
melanin.
• This layer presents stem cells conerned to
mitosis.

15. Prickle cell layer (stratum
spinosum)
• Consists of 5 - 10 rows of cells , cuboid in deep parts of
layer but become flatter gradually as they approach next
layer, the granular layer
• The cells of the prickle-cell layer are marked by presence
of specific tonofibrils in their cytoplasm.
• Special Langerhan's cells are demonstrated in this
layer, which carry immunological function.

17. Granular layer (stratum
granulosum)
• Contains 1-5 rows of cells elongated parallel to
epidermis
• It was considered previously that they were formed of a
special substance called keratohyalin
• The presence of the keratohyalin granules is the first visible
stage, of the beginning of the process of keratinization of the
epidermal cells.
•Serve as water-proof layer.

18. The epidermal germinative, prickle-cell, and
granular layers are sometimes embraced under the
name of Malpighian layer.

19. Lucid layer (stratum
lucidum)
• Composed of elongated cells containing a special protein
substance which refracts light strongly
• This substance resembles drops of oil and is called eleidin.
• Besides its main component, eleidin, the stratum lucidum
contains glycogen and fatty substances (lipoids, oleic acid)

20. Horny layer (stratum
corneum)
• It is composed of fine, anuclear keratinized elongated cells
• They are firmly attached to one another and are filled with a
horny substance (keratin) the chemical structure of which has
still not been finally determined
• It is believed that this is an albuminoid substance poor in water
and rich in sulphur and contains fats and polysaccharides.
• The outer part of stratum corneum is less compact and occasional
lamina separate from the main bulk, i.e. the process of
physiological desquamation occurs

22. Dermis
Papillary layer - consists of thin bundles of astructural
amorphous interstitial substance, collagen fibres & many fine
elastic fibres
Reticular layer - consists of collagen bundles are more
compact and thick and intertwine into a thick network of loops
The reticular and particularly the papillary layer of normal skin
have a small number of various cell elements: fibroblasts,
histiocytes, lymphocytes, mast, plasma cells & peculiar pigment
cells
Hairs, glands (epithelial appendages of the skin), muscles,
vessels, nerves and nerve endings are located in the dermis

26. Hypodermis
Consists of thick bundles of collagen and elastic fibres
stretching from the reticular dermal layer and forming a
wide-loop reticulum in which accumulations of large fat
cells, lobules of fatty tissue, are lodged
The thickness of the hypoderm varies from 2mm till 10cm
and more, and in some areas there is no hypoderm at all
(eyelids, prepuce, small pudendal lips, scrotum)

28. Skin Microscopy

30. Functions of the Skin
Immunological
Secretory
Thermoregulation
Receptory
Excretory
Protective

33. Receptors

34. Receptors

35. Cells of skin
• Melanocytes
• Keratinocytes
• Langenhan cells
• Merkel’s cells

36. Appendages of skin
• Hair
• Sebaceous gland
• Sweat glands
• Nail

38. Embryology
▪ The skin develops from two germinative zones:
▪ Ectoderm (the outermost embryonal layer)
which is represented by the epidermis (the
most superficial skin layer)
▪ Mesoderm (the middle embryonal layer)
represented by two-layers, namely the true
skin, or dermis (the middle layer) & the
subcutaneous fat, or hypoderm (the deepest
skin layer).

39. Summary
Stratum Basale (Germinal/
Malpighian layer):
Single layer of cuboidal cells resting on
basement membrane.
High mitotic activity.
Stratum Spinosum:
Several layers of polygonal cells.
Cells are held together by desmosomes.
Stratum Granulosum:
3-5 layers of flattened polygonal cells.
Cells contain keratohyaline granules.

40. contd….
Stratum Lucidum:
Seen only in non-hairy or thick skin.
Cells are flattened, translucent,
eosinophilic with indistinct boundaries &
nucleus.
Contains a product of keratohyaline i.e.
eleidin.
Stratum Corneum:
Composed of structureless dehydrated
dead cells.
Flattened & scale-like.
Filled with keratin.
Superficial layer is continuosly sloughed
off.

41. Stratum Basale

42. Stratum Spinosum

43. Stratum Granulosum

44. Stratum Lucidum

45. Stratum Corneum

46. TYPES OF SKIN
Thin Skin Thick Skin
Layers of epidermis St. corneum &
spinosum are thin while
lucidum is absent.
St. corneum & spinosum are
thick while lucidum is
present.
Thickness of epidermis 0.10-0.15 mm 0.6-4.5 mm
Epidermal ridges Absent Present (well developed
dermal paplillae)
Hair follicles, arrector pili
muscle & sebaceous
gland
Present Absent
Sweat glands Few Many
Sensory receptors Less More
Distribution Covers all parts of body
except palms & soles
Present in palms, palmar
surface of digits & soles

47. Self Assesment
Q1. Which layer is present only in thick skin:
a. Stratum basale
b. Stratum spinosum
c. Stratum granulosum
d. Stratum lucidum

48. Q2. The characteristic feature of reticular layer of
dermis is:
a. High mitotic activity
b. Contains keratin granules
c. Dense irregular connective tissue
d. Finger like processes

49. Q3. Secretion of sebaceous glands is aided by
contraction of:
a. Arrector pilorum muscle
b. Myoepithelial cells
c. Papillary layer of dermis
d. Reticular layer of dermis

50. Q4. Langerhans cells are present in:
a. Stratum basale
b. Stratum spinosum
c. Stratum granulosum
d. Stratum lucidum

51. Q5. The sensory cells of epidermis are:
a. Melanocytes
b. Keratinocytes
c. Langerhans cells
d. Merkel cells