Structure of skin Flashcards
Layers of epidermis in order top to bottom
Stratum corneum (horny layer) Stratum lucidum (clear) Stratum granulosm (granular) Stratum spinoseum (prickle cell) Stratum germinativum (basal or germinating)
Describe Stratum Corneum
Outer layer made up of scale like cells that continually shed (cornflakes)
Describe Stratum Lucidum
Made of small transparent cells through which light can pass. Only present in palms and soles of feet.
Describe Stratum granulosum
usually 1-3 layers thick. Cells have distinct granules and keratin is produced in this layer
Describe Stratum spinosum
3-6 layers thick cells are constantly dividing
Describe Stratum germinativum
Single basal layer of cells which contain melanocytes that produce the pigment melanin. The cells of the epidermis are produced in this layer and each has a distinct nuclei. These cells divide continuously by a process known as mitosis.
How does hyper pigmentation occur?
When the melanocytes over secrete.
What happens if melanocytes under secrete or stop secreting?
hypo-pigmentation or vitiligo
Description of dermis.
2 layers papillary and reticular. Good blood and lymph supply provided by lymph capillaries, arterioles and venules. Made up of connective tissue.
Description of papillary layer.
lies directly under the epidermis. Quite thin and has cone like projections called papillae. Provides nutrients and oxygen to the germinating layer of the epidermis.
Description of reticular layer
lies below papillary main section of dermis. Contains collagen and elastin These fibres are produced by fibroblasts and all held together in a ground substance. While the network is strong the skin will remain youthful and firm but as the fibres start to harden and split the network collapses and the ageing process starts to become visible. The appendages are also located in the dermis.
Description of the subcutaneous layer
under the dermis mainly made up of fat cells (adipose tissue) This fatty layer provides the plump contours of the body protection, insulation and support and food supply if needed.
Description of sweat glands
sudoriferous glands extend from the epidermis in to the dermis found all over the body, Regulate body temp. esp. numerous in palms and soles.
What are the two types of sweat glands
Aprocrine - larger and deeper found in the groin and under arms. Under hormonal control become active at puberty.
Eccrine - found all over the body secrete in response to heat.
what is the hair follicle?
Indentation of epidermis with the walls of the follicle being formed from a continuation of the cellular layer of the skins surface.
what is the inner root sheath?
Layer of the follicle closest to the hair has scale like cells that interlock with the cuticle to hold the hair firmly in place. The hair and the inner root sheath grow upwards together. the inner root sheath is made up of three layers - cuticle of inner root sheath, Henley’s layer and Huxley’s sheath
What is the outer root sheath?
This is the follicle wall does not grow upwards but remains stationary.
What is the connective tissue sheath?
surrounds the rest of the follicle and the sebaceous gland. Extension of the papillary layer of the dermis and provides a sensory nerve and blood supply.
what is hair?
Dead structures made of keratin (hardened protein). Keratin provides the body with a protective toughness for it’s entire surface.
Three areas of the hair?
Shaft - lies above the skin surface and runs through the centre of hair.
Root - lies under the skin inside the follicle.
Bulb - The large base at the bottom of the root and this encases the dermal papilla. the matrix is the lower region of the bulb where the cells divide rapidly to produce the new hair and follicle structure.
The three layers of the hair?
Cuticle - outer layer of scale like keratinised cells. No pigment protects hair.
Cortex - Main part. Elongated cells. Colour here. Strength thickness elasticity are held together.
Medulla - middle spongy. Not in vellus or fine terminal hair.
How is blood supplied to skin?
by capillaries. Arterioles supply oxygenated and venules remove waste. Capillaries also help maintain body temp by dilating and constricting.
What is dermal papilla and what is it’s function?
Blood supply for hair and its follicle. It provides food and oxygen essential for growth of hair. A separate organ.
Function of arrector pilli?
Muscle attached to follicle contracts when you are cold or frightened causing hair to stand up. this traps layer of warm air.
What are sebaceous glands?
Found all over body except palms of hands and soles of feet produce sebum. Gland attached to upper part of follicle duct enters directly in to the hair follicle. More active at puberty due to levels of androgen. Men secrete more and they become less active as we get older.
Function of sebum?
Bactericidal and fungicidal prevents against infection provides protection and stop skin dry out.
How sensory nerve endings work?
detect changes in environment send messages to the central nervous system which will send messages back via the motor nerves to stimulate a response.
Functions of the skin?
Sensation, Heat regulation, absorption, Protection, Excretion, secretion, vitamin d production.
Characteristics of black skin
usually looks shiny. thicker epidermis. Produces more sebum and sweat. Less hair. Desquamates quicker skin looks grey. erythema looks purple. Hair follicles curved. Prone to irregular pigmentation after waxing.
Characteristics of Asian skin
irregular pigmentation around eyes mouth, Sweat glands larger and more numerous, Skin usually ages well.
Characteristics of white skin
premature ageing. Thin prone to freckles. Fewer and less active sebaceous glands.
Characteristics of Chinese skin
more melanin that white. not many blemishes sebaceous glands less active. scarring more likely to occur resulting in unevenness, hyper-pigmentation and pitting.