skin

Question 1

what is the skin

Answer 1

The skin is the biggest organ of the human body and is continuous with its membranes lining the body’s orifices.

• protects underlying structures from injury and invasion from microbes
• contains sensory nerve endings that enable discrimination between pain, touch and temperature
• involved in thermoregulation
• surface area of 1.5-2m squared in adults
• sensory nerve endings found in the dermis, make the skin a sensory organ

Question 2

epidermis

Answer 2

outer layer of skin that is made of keratinised squamous epithelium. it varies in thickness (e.g. thicker on the palms and soles) and lacks blood vessels and nerve endings.

Question 3

name for shedding of epidermis surface cells

Answer 3

desquamation

Question 4

epidermis connection to dermis

Answer 4

hair, secretions and subcutaneous glands and sweat glands pass through the epidermis to reach the surface.

upward projections of the dermal layer (dermal papillae) anchor this securely to the epidermis and allow passage and exchange of nutrients and wastes.

dermal papillae arranged in parallel lines produce one’s fingerprints.

Question 5

skin colour

Answer 5

melanin, a dark pigment derived from the amino acid tyrosine and secreted by melanocytes is absorbed by epithelial cells.

melanin protects the skin from the harmful effects of ultraviolet rays in sunlight whilst the sun promotes synthesis of melanin.

excessive levels of bile pigments in the blood and subcutaneous fat gives the skin a yellow colour

Question 6

dermis

Answer 6

the dermis is tough and elastic, formed from connective tissue and contains collagen fibres and elastic fibres. this gives the skin its strength.

fibroblasts, macrophages and mast cells are the main cells within the dermis.

blood and lymph vessels are found in the dermis, with arterioles forming a network for capillaries to supply sweat glands, sebaceous glands, hair follicles and overall dermis.