Thursday, August 26

Skin care -Skin histology

Skin histology shows two main regions namely epidermis and dermis.

Skin histology

Skin consists of squamous keratinised outer layer called epidermis and fibrous and elastic connective tissue called dermis.
The dermis is connected to underlying subcutaneous connective tissue layer called hypodermis (primarily made up of adipose tissue).

Skin histology: epidermal layers

The epidermal cells are arranged into four/five distinct layers.
  1. Stratum basale layers
    Stratum basale, also known as stratum germinativum, contains dividing stem cells.
  2. Stratum spinosum The cells have spiny projections in this layer which is made up of several cell layers.
  3. Stratum granulosum
    Keratohyaline protein granules are found in cells in Stratum granulosum
  4. Stratum Lucidum (histology image) Stratum Lucidum layer is found only in thick skin like palm.
  5. Stratum corneum layers Stratum corneum layer consists of layers of dead cells (corneocytes) containing keratin.

Skin histology: dermal layers

Dermis is made up of two layers.
  1. Papillary dermis
    Papillary dermis is the upper layer of dermis and is intertwined with ridges of epidermis.
  2. Reticular dermis
    Reticular dermis is found beneath the papillary dermis and is packed densely with collagen fibers.

Skin histology - specialized cells of epidermis

  1. Melanocytes
    Melanocytes are located in the bottom layer of epidermis (stratum basale) and skin pigment is produced by them.
  2. Langerhans cells
    Langerhans cells are dendritic cells (with immune function) with clear cytoplasm having antigen-presenting function.
  3. Merkel cells
    Merkel cells are small cells associated with nerve endings, found in stratum basale, at the bottom of seat duct ridges.

Skin histology - image of layers
A. Epidermis layers
B. Dermis layers
C. Subcutis/ Hypodermis
D. Blood and Lymph Vessels
E. Stratum Germinativum
1.Hair Shaft
2.Stratum Corneum
3.Pigment Layer
4.Stratum Spinosum
5.Stratum Basale
6.Arrector Pili Muscle
7.Sebaceous Gland
8.Hair Follicle
9.Papilla of Hair
10.Nerve Fiber
11.Sweat Gland
12.Pacinian Corpuscle
15.Skin sensory Nerve ending (for touch)
16.Dermal Papillary
17.Sweat Pore

Skin histology: epidermal appendages

  1. Hair follicles
    Hair follicles are tubular invaginations towards the bottom of which are processes of cell multiplication, growth and differentiation yielding a cylindrical column of dead cells with keratin deposit, emerging as hair.(see histology image) Small packs of smooth muscle cells (arrector pili) are connected to the connective tissue of each hair follicle.
  2. Sebaceous glands
    Sebaceous glands are associated with hair follicles with function of secretion of sebum.
  3. Skin histology: sweat glands
    a)Ecrine sweat glands
    Ecrine sweat glands are the common sweat glands and are distributed throughout the body. b)Apocrine sweat glands
    Apocrine sweat glands are found on circumanal region, axilla, external genitalia and areola.
Epidermal layers
Hair follicle
Skin histology studies give us clear information in knowing its functions.

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