C: Skin Flashcards
What are the 4 main functions of the skin?
1) Protection
2) Thermoregulation
3) Providing sensory input from outside world
4) Metabolic function (synthesis vit D)
What 2 layers is the skin comprised of?
1) Epidermis - outer epithelial layer
2) Dermis - underlying area of connective tissue
What layer lies deep to the dermis, what does it contain?
Hypodermis or subcutis - layer of loose connective tissue containing variable amounts of fat
How is skin classified as thick or thin?
According to the thickness of the epidermis
How does the presence of hair follicles vary between thick and thin skin?
Thick skin is glabrous (non hairy)
Think skin has hair follicles
The epidermis is made up of what kind of epithelium?
Keratinised stratified squamous epithelium
What are the 5 layers recognised in thick skin?
1) Basal cell layer/ stratum basale/ stratum germinosum
2) Prickle cell layer/ stratum spinosum
3) Stratum granulosum/ granular cell layer
4) Stratum lucidum
5) Stratum corneum/ keratinised squamous layer
Describe the basal cell layer of the skin?
Single layer of basal cells (cuboidal/ low columnar) closet to the dermis
Describe the prickle cell layer/ stratum spinosum?
8-10 layers of keratinocytes, all with lots of desmosomes anchoring cells together and contain thick tufts of intermediate filaments
Describe the granular cell layer?
3-5 layers of cells, cells become gradually flatter as reach the surface, losing their nuclei and organelles and turn into keratinised squamous of next layer
Describe the stratum lucidum?
Thin. transparent layer, difficult to recognise in routine histological sections
Describe the stratum corneum/ keratinised squamous layer?
Layers of dead cells reduced to flattened scales or squames, filled with densely packed keratin, cells are flat and hard to see
What are the 3 types of non-epithelial cells present in the epidermis and what is their rough function?
1) Melanocytes - pigment cells of the skin
2) Langerhans cells - play an immunological role
3) Merkel cells - act as mechanoreceptors
Which of the 5 layers of the skin is absent or very thin in thin skin?
Stratum lucidum
What are the 3 main types of skin cancer and from which layer of the skin does each originate?
1) Basal cell carcinoma - stratum basale
2) Squamous cell carcinoma - stratum spinosum
3) Malignant melanoma - stratum basale
Which type of skin cancer is the least common and most dangerous?
Malignant melanoma
What are warts?
Benign skin growths caused by a viral infection in the skin - hyperkeratonic papules with a rough irregular surface
During development a number of downgrowths from the epidermis invade the underlying dermis to form which 3 structures?
1) Sweat glands
2) Sebaceous glands
3) Hair follicles
Which of the 3 structures found in the dermis are absent from thick skin?
All 3
Which structure in the dermis is involved in the development of acne, how?
Sebaceous glands
In puberty, size and activity of sebaceous glands increases, if the gland becomes blocked the sebum can be forced out into the dermis where it illicits and inflammatory response
Where are erector pili muscles located and what is their function?
Small bundles of smooth muscle associated with hair follicles, contraction of the muscles elevate the hair forming goose bumps to trap heat and help sebum be released from the gland into the duct
What is the nerve supply of the erector pili muscles?
Sympathetic
Other than the erector pili muscles, what other structures in the skin have a sympathetic nerve supply and what are the consequences of stimulating these fibres?
Sweat glands - cause glands to produce sweat
What fibres are contained in the connective tissue making up the dermis?
Irregular bundles of collagen fibres and networks of elastic fibres
What 2 layers is the dermis subdivided into?
1) Papillary layer - superficial and loosely woven
2) Reticular layer - deeper, thicker and denser
In areas of thick skin that are subjected to friction and shearing forces, how do the dermis and epidermis interdigitate?
Epidermal downgrowths - rete ridges
Upwardly projecting dermal papillae
Which layer of the skin contains the blood and nerve supply of the skin?
The dermis
What is a blister?
Split in the stratum spinosum, blister roof consists of normal and necrotic keratinocytes. Blister roof = normal and degenerating keratinocytes. Blister cavity’s filled with clear transudate
What is damaged in first degree burns?
Superficial - just epidermis (eg. sunburn)
What is damaged in second degree burns?
partial thickness - epidermis and part of dermis
What is damaged in third degree burns?
Full thickness - destroy the epidermis and dermis and may go into the subcutaneous tissue
What is a dermatome?
The area of skin supplied by afferent nerve fibres of a single posterior spinal root
Branches of cutaneous nerves form a dermal nerve plexus where?
At the base of the dermis
Cutaneous nerve receptors are classified into what 2 groups?
1) Free nerve endings/unencapsulated nerve endings/ simple receptors
2) Encapsulated nerve endings/ compound receptors
What are free nerve endings?
Branching axons devoid of surrounding schwann cells
What 3 kinds of receptors can free nerve endings function as?
1) Nociceptors
2) Thermoreceptors
3) Mechanoreceptors (in the skin associated with the shaft of hair follicles and firing when the hairs are moved)
Some free nerve endings are associated with Merkel cells in the basal epithelium, what do the resulting Merkel-neurite complexes function as?
Mechanoreceptors which respond to pressure
Encapsulated nerve endings in the skin function as what kind of receptors?
Mechanoreceptors
Name 3 encapsulated nerve endings found in the skin?
1) Meissner’s corpuscle
2) Pacinian corpuscle
3) Ruffini endings
Where are Merkel cell-neurite complexes found?
In the dermal-epidermal junction
What is the speed of adaptation of Merkel cell-neurite complexes and what do they detect?
Slowly adapting - detects pressure
Where are Pacinian corpuscle’s located?
Deep in the subcutis
What is the speed of adaptation of Pacinian corpuscles and what do they detect?
Rapidly adapting - detects mechanical distortion. especially vibration
Where are Meissner’s corpuscles located?
Dermal papillae
What is the speed of adaptation of Meissner’s corpuscles and what do they detect?
Rapidly adapting - detects fine or discriminative touch
Where are Ruffini endings found?
In the dermis
What is the speed of adaptation of Ruffini endings and what do they detect?
Slow adapting - stretching and shearing forces
