Anatomy: Anatomy of the Skin Flashcards
Which layer of the epidermis varies the most throughout the different skin surfaces of the body?
Keratin layer
Which part of the hair bulb contains the keratin producing cells?
Hair matrix
What is the function of the granular layer of the epidermis?
Cells secrete lipids, keratin, filaggrin and involucrin which go on to form the cornified envelope of the keratin layer
What are the three distinguishing features of the keratinocytes of the prickle cell layer (epidermis)?
Lack of nuclei
High lipid content
Odland bodies
Which division of the autonomic nervous system controls the eccrine glands?
Sympathetic
In which layer of the epidermis does mitosis of keratinocytes occur?
Basal layer (stratum basale)
Which germ layer gives rise to the dermis?
Mesoderm
What is the function of the sebaceous glands?
Produce sebum
What is the main distinguishing feature of Langerhans cells?
Birckbeck granules
What stimulates the development of apocrine glands?
Androgens - develop at puberty
What are corneocytes?
Overlapping non-nucleated cell remnants of keratinocytes found in the keratin layer of the epidermis
Which germ layer gives rise to the epidermis?
Ectoderm
Name the 4 layers of the epidermis from superficial to deep
Keratin layer (stratum corneum), granular layer (stratum granulosum), prickle cell layer (stratum spinosum), basal layer (stratum basale)
Define melanocytes
Pigment-producing dendritic cells found in the basal layer and above which contain melanosomes
What is the arrector pili muscle?
Smooth muscle attached to hair fibres which can pull the hair perpendicular to the skin during cold/fright (goosebumps)
Define Meissners corpuscles
Groups of sensory nerves that are found high in the dermis which respond to light touch and vibration
What is the dermo-epidermal junction?
Interface between epidermis and dermis
Which part of the hair bulb contains the vasculature?
Dermal papilla
What are the 3 phases of the hair cycle?
Anagen, catagen, telogen
Define Blaschko’s lines
Lines of normal cell development in the skin; they are invisible under normal conditions but become apparent when some diseases of the skin or mucosa manifest themselves according to these patterns
Which layer of the epidermis consists of 2-3 layers of flattened keratinocytes and Langerhans cells?
Granular layer
What occurs during catagen in the hair cycle?
No active growth, involution of the hair
What is vellus hair?
Fine hair found on the face of women and in prepubertal children
What is the function of the keratin layer of the epidermis?
Acts as a waterproof barrier (most superficial layer)
How is hair pigmentation produced during hair growth?
Via melanocytes above dermal papilla
What are nails composed of?
Plates of cells filled with hard keratin
What is the function of melanin granules?
Full melanosomes (‘melanin granules’) protect basal keratinocyte DNA from damage by UV radiation by absorbing the rays
What is the primary function of the dermis?
To cushion and support the epidermis
What is the majority of the dermis composed of?
Connective tissue - collagen, elastin and ground substance
Name two functions of the eccrine glands other than thermoregulation
Control of salt loss, ultrafiltration
What is lanugo hair?
Soft hair found in newborns
Where is the nail plate found?
Sits on the nail bed
Describe the structure of eccrine glands
Coiled, tubular structures which open directly onto the skin
Bullae are associated with alterations of which structure?
Dermo-epidermal junction
What is the structure of the apocrine glands?
Found deep within the dermis, project up towards and open out into the hair follicle
What is terminal hair?
Course hair found on the scalp, beard and pubic region
Describe the structure of the sebaceous glands
Lobulated masses which wrap around hair follicles
Why is the blood supply to the dermis larger than the metabolic demand?
Allows the skin to undertake its role in thermoregulation
What stimulates the production of sebum by the sebaceous glands?
Hormones - sebaceous glands are quiescent pre-puberty
Which layer of the epidermis is composed of corneocytes and the cornified envelope?
Keratin layer
What is the cornified envelope?
Protective waterproof barrier found in the keratin layer
What occurs during telogen in the hair cycle?
Resting phase of the cycle when the hair falls out
What is the function of apocrine glands?
Produce an oily, scented fluid
What are Langerhans cells?
Dendritic cells found within the prickle cell level in epidermis, the dermis and lymph nodes
Where are apocrine glands found?
Primarily found in the axillae and perineum
Which germ layer gives rise to the melanocytes?
Ectoderm - migrate from the neural crest to the epidermis in the first 3 months of foetal development
What occurs at the nail matrix?
Cells divide and then produce hard keratin
Where are sebaceous glands found?
Primarily found in face, chest and upper back, not present in palm and sole skin
Define Pacinian corpuscles
Groups of sensory nerves found deeper in the dermis which respond to heavy, deep pressure
What is the epidermis?
The most superficial, protective layer of skin, which consists of stratified squamous epithelium that is mainly made up of keratinocytes
What is the primary function of Langerhans cells?
Antigen presentation to T cells
What do the free nerve endings in the basal layer of the epidermis and in the dermis respond to?
Pain
What occurs during anagen in the hair cycle?
Active growth
What are the functions of the dermo-epidermal junction?
Support, anchorage, adhesion, growth and differentiation of basal cells
Semi-permeable membrane acting as barrier and filter
What is sebum composed of?
Squalene, wax esters, TG and FFA
What is the hyponychium?
Area of epithelium underlying the free edge of the nail plate on the nail
Name the 4 layers of the dermo-epidermal junction, from superficial to deep
Basal cell plasma membrane, lamina lucinda, lamina densa, sub-lamina densa zone
What is the cuticle?
Extension of the skin fold covering the nail root
What is the function of melanosomes?
Convert tyrosine to melanin pigment
When full the melanin granules will protect basal keratinocyte DNA from damage by UV radiation
What are Merkel cells?
Cells found within the basal layer of the epidermis involved in mechanoreception
Which layer of the epidermis contains larger polyhedral keratinocytes joined by desmosomes?
Prickle cell layer
Which layer of the epidermis contains stem cells, Merkel cells, melanocytes, an abundance of intermediate filaments (keratin) and a single layer of small cuboidal keratinocytes?
Basal cell layer
What is the function of sebum?
Controls moisture loss and protects against fungal infection
