Skin as a semi-permeable membrane

What are the four functions of the skin

Protection- against pathogens?UV light

Thermoregulation- hair and sweating

Sensation- many sensory nerve endings for pressure, temperature and pain which allow interpretation of the external environment

Metabolism- produces vitamin D used in calcium and phosphate metabolism

What are the skin composed of ?

The outer epidermis and the inner dermis and the hypodermis

Outline the epidermis

Protective barrier layer

Give rise to sweat glands, sebaceous glands and mammary glands

How long is the entire epidermal cycle

Takes around 27days

What are the three factors that determine human skin colour

An inherent yellowish colour form the carotene in the subcutaneous fat

the conc and oxygenation of hemoglobin in the dermal capillaries

melanin

what is melanocytes and melanosomes

Melanocytes produce melanin

Melanocytes package melanin into vesicles called melanosomes. These are taken up by keratinocytes and accumulate on top of the nucleus and protect the DNA from ionising UV radiation.

What’s the function of melanin

Melanin functions to protect the body from UV radiation

Name and explain the other cells of the epidermis

Keratinocytes- protective barrier against environmental damage

Melanocytes- role in skin pigmentation, Produce and distribute melanin

Langerhans cells- Specialist in antigen presentation and belong to the skin immune system

Merkel cells-

Name some keratinized structures

Hair, nails

Short overview of how hair grows

Is an elongated rod of keratinised cells (hair shaft), which grow from a root (hair bulb) lying in the dermal layer of the skin but formed by epidermal cells.

Differentiate sebaceous glands and sudoriferous glands

Sebaceous glands- connected to the hair follicles, produce sebum which helps to protect skin and hair

Sudoriferous glands- apocrine glands and eccrine glands

What’s a ceruminous glands

Modified apocrine glands- ducts open into larger ducts that drain into the hair follicles of the external sudatoory canal

Secretions combine with sebum secreted by sebaceous glands to form cerumen (ear wax)

What is the dermis composed of

Composed of fibroblasts, which secrete large amounts of extracellular matrix

elastin

Blood vessels

Nerves

What’s the subcutaneous tissue also called the hypodermic composed of •Primarily composed of loose connective tissue.

•Contains large blood and lymphatic vessels and nerves that supply those of the overlaying dermis.

•Major site of fat storage in the body.

What’s the routes of drug transport

Intracellular

Intercellular

Transappendageal