Skin

Skin & appendages

A/P Dr. Joachim Perera

Learning outcomes 1. Describe the microscopic anatomy of the epidermis & dermis 2. Describe the structure of the hair follicle, sebaceous gland & sweat gland 3. Describe the structure of the nail 4. Describe the arrangement blood vessels of the skin

5. Describe the nerve supply of the skin

Layers of skin

Epidermis

Dermis

Epidermis

Keratinocytes

Melanocytes • Distributed in the

basal layer • Produce melanin as granules

• Transfer the melanin to keratinocytes

Langerhan cells • Distributed in the spiny layer • Antigen presenting cells

• Activates plasma cells to produce antibodies

Merkel cells

• Distributed in the basal layer • Are in contact with sensory nerve endings • Touch receptors

Thick skin

Thin skin

Dermis

Papillary layer • Loose connective tissue with thin collagen & elastic fibers • Dermal papillae extends into epidermis

Dermis

Reticular layer • Dense connective tissue thick collagen & elastic fibers • Give strength and elasticity

Blood supply

Sweat glands • Coiled simple tubular glands • Mostly Eccrine • Some apocrine

Hair shaft • Lies above the skin

Cuticle Cortex Medulla

Formed of hard keratin

Hair follicle • Epidermal down growth forming a sheath around the hair root Internal epithelial root sheath

External epithelial root sheath Connective tissue root sheath Hair matrix Hair papilla

Sebaceous glands

• Simple alveolar glands • Secretes sebum • Holocrine secretion

Arrector pili muscle Sebaceous gland

Nail Modified upper layers of the epidermis

Nerve supply and sensory receptors Unencapsulated

1. Free nerve endings 2. Merkel discs 3. Hair follicle receptors

Nerve supply and sensory receptors Encapsulated

1. Meissner’s corpuscles 2. Pacinian corpuscles 3. Ruffini endings

Do it yourself ! Function Protection

Microscopic adaptation Mechanical – Thick keratin layer Infection – tight cell junctions prevents entry of organisms. Langerhan cells helps in the production of antibodies