Summary (gb)

The skin is composed of two distinct layers:
1. The epidermis connective tissue
2. Dermis connective tissue
Beneath the 2nd layer is loose connective/adipose tissue called hypodermis

epidermis
The epidermis has five layers:
1. Stratum Germinativum (deepest)
2. Stratum Spinosum
3. Stratum Granulosum
4. Stratum Lucidum
5. Stratum Corneum (most superficial)

The two deepest layers are called the Germinative Zone or Basal Zone
The other layers are called the Horny Zone
Epithelial cells in the skin undergo a process called keratinisation, which means the cytoplasm is replaced with keratin.
Keratin contains nitrogen, amino acids and varying propotions of sulphur.
Hard Keratin contains 4-5 % and is found in nails and hair.
Soft Keratin contains 2 % and is found in skin.

Cells found in epidermis are
1. Epithelial cells
2. Melanocytes

Features of:
Stratum germinativum: consists of a single layer of columnar shaped cells with nuclei. These cells have tiny processes on their lower surfaces, which seem to anchor them to the underlying dermis.

Stratum spinosom is several layers thick, and is composed of irregular cells, slightly separated from each other. There are intercellular bridges between these cells, which appear as spiny processes.

Stratum granulosum is a layer consisting of three or five rows of flattened cells,lying parallel to the skin surface,

Stratum lucidum is a clear, translucent layer of three or five cell thickness. The cells cannot be identified as separate entities, but are flattened and densely packed.

Stratum corneum is the outermost layer, and is composed of clear, dead, scale-like cell, which are flattened and fused.

Colour of the skin depends on
1. Melanin pigment
2. Carotene pigment
3. blood flow

Melanocytes are located