بسم الله الرحمن الرحيم Practical histopathology Lab 11

1. بسم الله الرحمن الرحيم Practical histopathology Lab 11 (General Methods in preparation of skin biopsies)

2. Introduction • The skin together with its accessory organs, sweat glands, sebaceous glands, hair and the nails forms the largest organ in the human body. • This system covers 1.5-2m2 and represents 16% of body weight. • The skin and its accessory organs form the integumentary system.

3. Functions of the Skin • Protection. • Temperature regulation. • Sensations. • Storage of chemical compounds. • Excretion of wastes. • Synthesis of compounds. • Determines characteristics.

4. Layers of the Skin • The human skin is composed of three major layers of tissue: • The epidermis is the top layer of skin made up of epithelial cells. • The dermis is the middle layer of skin, composed of dense irregular connective tissue such as collagen with elastin. • The subcutaneous layer is the innermost layer, containing fatty tissue.

5. Epidermis • The epidermis main functions are protection, absorption of nutrients and homeostasis. • It contains different types of cells: keratinocytes, melanocytes, Merkel cells and Langerhans cells. • Accumulations of melanin are packaged in melanosomes. These granules form a pigment shield against UV radiation. • It does not contain blood vessels.

7. Dermis • The dermis is the middle layer of the skin that offers elasticity. • It is composed of connective tissues and collagen fibers. • The dermis provides a site for the hair follicles, sweat glands, sebaceous glands, blood vessels, lymph vessels, sensory receptors, nerve fibers and muscle fibers.

8. Subcutaneous Layer • The subcutaneous is the layer of tissue directly underneath the dermis. It is also called hypodermis. • This layer of tissue is composed of fat cells and connective tissue. • Its functions include insulation, the storage of energy and aiding in the anchoring of the skin. • It is the thickest layer of the integumentary system.

9. Overview • Cutaneous Pathology (dermatopathology) is the microscopic examination of skin biopsies in order to determine a specific diagnosis or a list of differential diagnoses. • Usually the diagnosis can be determined by the routine stain for tissue sections (Hematoxylin and Eosin).

10. Skin lesion selection • The skin lesions which developed recently according to the patient history should be selected for that purpose. • Detailed clinical information (age, sex and site of skin biopsy) of the investigated patients should be provided. • Biopsies from healthy donors may be analyzed for control purposes in some cases.

11. Fungal Infections Hyperkeratosis Canker sores Skin Disorders ViralInfections SkinInfestations Secondary bacterial infections

12. Acne • Acne is a very common skin condition characterized by comedones (blackheads and whiteheads) and pus-filled spots (pustules). • It usually starts at puberty and varies in severity from a few spots on the face, back and chest, which most adolescents. 

13. Basal Cell Carcinoma • A basal cell carcinoma (BCC) is a type of skin cancer. There are two main types of skin cancer: melanoma and non-melanoma skin cancer. • BCC is a non-melanoma skin cancer, and is the most common type (> 80%) of all skin cancer. 

14. Melanoma • Cutaneous malignant melanoma is a cancer of the pigment cells of the skin. If it is treated early, the outlook is usually good. • Melanocytes sometimes grow together in harmless groups or clusters, which are known as moles. • Most people have between 10 and 50 moles and often they are darker than the surrounding skin. • They can then invade the skin around them and may also spread to other areas such as the lymph nodes, liver and lungs.

15. Contact Dermatitis • The words ‘dermatitis’ and ‘eczema’ are interchangeable and mean the same thing.  • Dermatitis means an inflammation of the skin. • The term ‘contact dermatitis’ is used when this inflammation is caused by contact with something in the environment.

16. Fungal infection of the nails • Fungal infections of the nails are also known as onychomycosis, as tineaunguium, and as ringworm of the nails. • The fungi are usually those that cause athlete’s foot – a common infection of the skin of the feet. • In athlete’s foot the fungi live in the keratin that makes up the outer layer of the skin, but they can also invade the hard keratin of which nails are made. When this happens, the result is a fungal infection of a nail.