Flashcards in SDL: Skin and Sensory Receptors Deck (38):
List three functions of skin, other than sensation.
- Barrier against microbes
- Thermoregulation - i.e. sweating and rich vascular network
- Protection against UV light
Where is glabrous (thick) skin located in humans?
Ventral portion of the fingers
Palms, soles of feet
Lips, labia minora
The epidermis is made up of what type of epithelium?
Keritanised stratified squamous epithelium
What are the five layers of glaborous epidermis from deep to superficial?
What is the stratum basale?
The layer responsible, by repeated mitotic division, for the constant regeneration of the other layers of the epidermis. The cells are arranged as a single layer of cuboidal or low columnar cells which connect to the prickle cell layer above the basement membrane between epidermis and dermis below.
What is the stratum spinosum?
Composed of polyhedral keratinocytes with large, pale-staining nuclei and prominant nucleoli.
What is the stratum granulosum?
Begin to loose their polyhedral shape and become progressively more flattened near the surface. Very basophilic.
What is the stratum lucidum?
Clear layer of dead skin cells.
What is the stratum corneum?
Flat flakes and sheets of keratin, coated with anti-wetting agent. Some residue of cell structure may remain underlying this.
Which layer is very thin or absent from thin skin?
From which layer do basal cell carcinomas arise?
From which layer do squamous cell carcinomas arise?
From which layer do malignant melanomas arise?
From the melanocytes located in the stratum basale
What are warts?
Benign skin tumours caused by HPV.
Which of the epidermal appendages is absent from thick skin?
Which of the epidermal appendages is involved in the development of acne?
Where are the arrector pili muscles located? What is their function?
Bundle of smooth muscle fibres. The muscle inserts at one end into the sheath of the follicle at the point below the sebaceous glands, and at the the other end into the dermal papillary area beneath the epidermis.
Lifts the hair erect.
Which skin structures have sympathetic nerve supply?
- Arrector pili muscles
- Eccrine sweat glands
What is a blister?
Friction blisters are caused by excess shear stress between the surface of the skin and the body. The strata of skin around the Stratum spinosum are most susceptible to shear. As the Stratum spinosum tears away from the connecting tissues below, plasma from the cells diffuses out.
What is damaged in first degree burns?
Epidermis - erythema only.
What is damaged in second degree burns?
Epidermis (broken), and partial dermis damage.
What is damaged in third degree burns?
Epidermis, dermis (which contains the nerves), and subcutis. Underlying musculature and bones may be damaged (usually called a 4th degree burn).
What is a dermatome?
An area of the skin supplied by nerves from a single spinal root.
Where would you find the dermal nerve plexus and what supplies it?
At the base of the dermis.
Supplied by the cutaneous nerves.
What are the two morphological classifications of cutaneous sensory receptors?
1. Free nerve endings/unencapsulated nerve endings/simple receptors
2. Encapsulated nerve endings/compound receptors
What are free nerve endings?
Branching axons devoid of Schwann cells.
What sensations are free nerve endings responsible for?
Pain (nocicepters), itch, temperature (thermoreceptors) and some of them associate with hair follicles and act as mechanoreceptors.
Where would you find free nerve endings?
They occupy the papillary dermis and send twigs into the epidermis where some of them associate with Merkel cells.
What is the function of free nerve endings that associate with Merkel cells?
The form Merkel cell-neurite complexes and act as mechanoreceptors that respond to pressure.
What is the function of encapsulated nerve cell endings?
Mechanoreceptors of various types.
Where would you find a Merkel-cell neurite complex?
What is the speed of adaptation for Merkel cell-neurite complexes?
Where would you find a Pacinian corpuscles?
Deep in the subcutis
What stimuli do Pacinian corpuscles detect?
Detection of deep pressure and vibration
Where would you find Meissner's corpuscles?
Particularly prominent in the papillary dermis of the tips of the fingers, toes, soles of feet and palms.
What stimulus do Meissner's corpuscles detect?
Rapidly adapting mechanoreceptors responsible for light touch sensation.
Where would you find Ruffini's endings?
Dermal layer - particularly common in the sole.