Skin Flashcards
Skin is said to be a combination of which tissues?
All four, epithelial, connective, muscle and nerve
Why are epidermal cells classed as kertainocytes?
They make keratin
What does the epidermis do?
Prevents water loss by evaporation
Epithelium
Separates internal and external compartments
What is the function of the dermis?
Reduces risk of external injury
Maintains the epidermis by its blood flow
Permits body cooling
Immune surveillance
UV protection
Energy storage
Sensory information
Connective tissue - gives structural strength
What is the hypodermis?
Adipose layer below the dermis, anchors the skin to the underlying structures
What does the epidermis consist of?
5 strata (layers) of stratified squamous epithelium
What are the 4 types of epidermal cells?
Keratinocytes
Melanocytes
Langerhans cells
Merkell cells
Describe the structure of Keratinocytes
Contains keratin, hard, resistant to abrasion, most abundant cell type?
Extrudes lipids providing waterproofing
Constantly dividing - protecting from trauma and other damage
What are melanocytes responsible for?
Pigment formation
What are langerhans cells responsible for?
Immune surveillance
What are Merkell cells responsible for?
Touch receptors
What are the five layers of epidermis made by?
Maturing keratinocytes
Where does the epidermis span to and from?
From the basement membrane to the skin layer
What are the names of the five layers in descending order?
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Describe the cell arrangement in the stratum basale
Tall collumnar cells with melanocytes and merkel cells interspersed
Cells linked to the basal membrane by hemisdesmosomes
Cells linked to each other by desmosomes
What is the stratum basale predominantly composed of?
Basal keratinocyte stem cells, irregular interface with dermis, forms dermal papillae
When is the stratum spinosum created?
After cell death
How are the spines created in the stratum spinosum?
Cell shrinks but the desmosome junctions create spines
What does the stratum granulosum contain?
Granules of keratohyalin (possible precursors of keratin)
Where is keratohyalin converted into keratin?
In the stratum corneum
How are cells bound together in the stratum corneum?
By desmosomes, disulphide linkage gives strength
What is keratinization?
The process whereby keratin hardens
Which layer of skin varies in thickness most around the body?
Stratum corneum
What are the two layers of dermis?
The papillary layer, forming papillae
AND
The reticular layer, forming a network of fibres
Describe the tissue of the papillary layer
Loose connective, cellular
Describe the tissue of the reticular layer
Dense irregular connective, fibrous
What is the dermis protective against?
Pathogens
What are the blood vessels in the dermis responsible for?
Thermoregulation and nutrition
What type of structural proteins exist in the reticular dermis?
Densely packed collagen fibers in three planes. It is the primary location of dermal elastic fibers.
What gives the dermis its properties of strength, extensibility and elasticity?
Collagenous, elastic and reticular fibres
What deteriorates in old age within the reticular dermis?
Elasticity
What can you find in the reticular layer?
Roots of the hair, sebaceous gland, sweat glands, receptors, nails, and blood vessels
As cells approach the surface how do they become waterproof?
The cytoplasm is replaced with a tough waterproof protein called keratin. Intercellular glycolipid exists between cells which are waterproof
What protects the skin from UV?
Melanin
How does a hair stand on end?
When the arrector pili muscle contracts
What does the sebaceous gland secrete?
Sebum
What types of sweat glands exist?
Apocrine (armpits)(secretes into the hair follicle) and eccrine
What type of glands are eccrine sweat glands?
Simple tubular glands
What type of secretion leaves both types of sweat gland?
Apocrine - protein rich
Eccrine - watery thermoregulatory secretion
