Skin

Question 1

Name some other words for skin

Answer 1

Integumentary system
Cutis
Dermis

Question 2

What are epidermal cells called?

Answer 2

Keratinocytes

Question 3

What are the functions of epidermis and dermis?

Answer 3

The epidermis prevents water loss by evaporation. It is an epithelium which forms boundaries between internal and external compartments.
The dermis reduces risk of external injury, maintains the epidermis by its blood flow and permits body cooling. It also acts as immune surveillance, UV protection, energy storage and sensory information. The dermis is connective tissue which gives a structural strength.

Question 4

What epithelia is found in the epidermis?

Answer 4

Stratified squamous keratinising epithelium

Question 5

What are the four types of epidermal cells and what are their function?

Answer 5

Merkel cells are Touch receptors.
Langerhans cells act as immune surveillance.
Melanocytes form pigmentation.
Keratinocytes are the most frequent cell and they contain keratin which makes it hard and resistant to abrasions. They’re waterproof and extrude lipids and are constantly dividing to protect from trauma.

Question 6

Name the five layers of epidermis from bottom to top

Answer 6

Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

Question 7

Describe the structure of stratum basale

Answer 7

It is made up of columnar cells with melanocytes and merkel cells. The cells are bound to the basal membrane by hemidesmesomes. It has an irregular interface with dermis-dermal papillae. These proliferate continuously from stem cells.

Question 8

Describe the structure of stratum spinosum

Answer 8

This is a spinous layer created by desmesome junctions. It is a preparative layer for keratinisation.

Question 9

Describe the structure of stratum granulosum

Answer 9

The presence of granules defines the layer. The granules are a possible precursor of keratin called keratohyalin.

Question 10

Describe the structure of the stratum lucidum and stratum corneum

Answer 10

They are difficult to distinguish between. They involve the conversion of keratohyalin to keratin. They have lots of disulphide linkages to give strength but the stratum corneum has no organelles.
There is a 15-30 day turnover of cells.

Question 11

What is keratinisation?

Answer 11

Organic process where keratin is deposited in cells so they becomes horny.
Psoriasis is when there is over keratinisation.

Question 12

What are the two layers of the dermis called?

Answer 12

The papillary layer is loose connective tissue.

The reticular layer is dense irregular connective tissue and is fibrous.

Question 13

What is the function of the papillary layer?

Answer 13

It protects against pathogens.

It has blood vessels that thermoregulate and provide nutrients. It has nerve endings.

Question 14

What is the function of the reticular layer?

Answer 14

It has collagen bundles and elastic fibres. Loss of elasticity is normal in old age.

Question 15

How does the epidermis stay waterproof?

Answer 15

The keratin in the cells are waterproof.

Intercellular spaces filled with lipid cement stop water getting in.

Question 16

Where does keratin originate from?

Answer 16

Originates from lamellated granules in the stratum granulosum

Question 17

What factors give skin its colour?

Answer 17

Blood
Carotene
Melanin

Question 18

Describe the origin of hair follicles

Answer 18

They form from the epidermis in utero and grow down as epithelial cells. Blood vessels invade and the hair grows.

Question 19

Describe the structure of the hair follicle

Answer 19

The arrector pili muscles are attached to the follicle root and base epidermis at an angle. The hair straightens when the muscle contracts.
Sebaceous gland lie between the follicle and pili muscle and they secrete sebum.

Question 20

Name three skin glands and what they secrete

Answer 20

Sebaceous glands are beside hair follicles and they secrete sebum.
Apocrine sweat glands found in axilla and they have protein rich secretions.
Eccrine glands secrete sweat.

Question 21

Describe the structure of eccrine glands

Answer 21

They are simple tubular glands with a coiled secretory portion and coiled and straight duct in dermis and spiral channels in epidermis. They have a thermoregulatory function.