Week 8: Skin histology Flashcards
What are the functions of the skin?
- protection- moisture control, barrier to pathogens, UV
- metabolic function e.g production of VitD
- thermoregulation
- sensory organ
- rapid repair of injury
What are the 3 layers of skin?
- Epidermis
- Dermis
- Subcutis
What type of cells are found in the epidermis (the most superficial layer)?
keratinised stratified squamous epithelial cells
keratinised just means produces keratin
What two layers is the dermis made up of and what does this layer contain?
-papillary dermis (top)
-reticular dermis
made up of fibrous and fibroadipose tissue
contains blood vessels, nerves, muscles and sensory receptors
What is the subcutis layer made of?
largely made up of adipose tissue, with supporting fibrous bands and larger blood vessels
What does stratified mean?
made up of different layers, where not all of the layers are in contact with the basement layer
What does glabrous skin mean?
non-hair bearing
What are the 5 layers of the epidermis in thick skin? (from bottom to top)
- Basal layer / stratum basale
- Prickle cell layer / stratum spinosum
- Granular layer / stratum granulosum
- Stratum lucidum
- Keratin layer / stratum corneum
Which layer of the epidermis is NOT in thin skin/ is only found in thick skin?
stratum lucidum
What happens to nuclear integrity as cells move further up the epidermis?
they start to loose nuclear integrity until they reach the top of the epidermis where there is no nuclear detail left
What cells do we find in the epidermis?
- keratinocytes
- melanocytes
- langerhans cells
What are melanocytes?
- cells responsible for pigment in the skin
- brown pigment = melanin
What are langerhans cells?
- found in the upper epidermis
- mostly cluster round blood vessels
- antigen presenting cells mostly visible in prickle cell layer
- when these cells are stimulated (when something is presented to them), they migrate down into the dermis to find the lymphatics and go to the lymph nodes
Name 5 appendages within the skin
- Sebaceous glands
- Hair follicles
- Eccrine glands
- Apocrine glands
- Arrector pilli
What do sebaceous glands do?
-secrete sebum
2 types:
-those associated with the hair follicle and secrete sebum into the hair follicle
-those that secrete directly onto the surface of the skin
What do eccrine glands do?
twisty glands that extend all the way to the top of epidermis –> thermoregulation function, produce sweat
What do apocrine glands do?
produce odour
What are arrector pili muscles and what is their function?
- bundle of smooth muscle fibres
- insert at one end into the follicle sheath just below sebaceous gland and the other in the superficial dermis
- function is to make hair stand on end or be flat depending on temperature of person
What is a pilosebceous unit?
made up of:
- sebaceous gland
- hair follicle
- arrector pilli muscle
What are the 4 types of skin receptors?
- Meissner corpuscles
- Merkel cells
- Pacinian corpuscles
- Ruffini endings
Where are meissner corpuscles found?
papillary (upper) dermis
What is the function of meissners corpuscles?
fast adapting for detecting discriminatory touch and vibration
What is the function of merkel cells?
slower adapting
discriminatory touch and pressure receptors
What is the function of pacinian corpuscles?
large encapsulated sensory receptors responsive to pressure, coarse touch and rapid vibration
Where are pacinian corpuscles found?
deep to the dermis, ligaments and joint capsules
What is the lamella of a pacinian corpuscle composed of?
flattened schwann cells and endoneurial fibroblasts
Where are merkel cells found?
in the basal layer of the epidermis (dermal-epidermal junction)
Where are meissner’s corpuscles found?
found in the papillary dermis of the fingertips, soles of the feet, nipples, eyelids, lips and genitalia
What is 1st degree burn?
- superficial burn that only effects the epidermis
- doesn’t extend into dermis or subcutaneous tissue
- quite painful but will resolve relatively quickly
- e.g sunburn
What is 2nd degree burn?
- burn reaches dermis
- epidermis is lost
- inflamed and painful (pain level is determined by how deep it goes)
Whats a third degree burn?
- full thickness burn
- goes through epidermis, dermis and subcutaneous tissue
- this might not be painful as all the nerve fibres and pain receptors could be damaged
What is the papillary layer of the dermis made up of?
small blood vessels, lymph & nerves, fine collagen and elastic fibres
What is the reticular layer of the dermis made up of?
vascular plexus
lymph
nerves & appendages
compact collagen fibres & thick elastic fibres
What is a difference between thin and thick skin?
thin skin has hair follicles while thick skin is glabourous (non-hairy)
Where is thick skin located in humans?
areas where there is lots of abrasion - fingertips, palms and soles of your feet
What is the stratum basal layer (deepest layer) made of?
basal cells, merkel cells and melanocytes
What is the stratum spinosum (prickle cell layer) made of?
made of keratinocytes, langerhans cell
What is found in the stratum granulosum and stratum lucidum?
keratinocytes
What is the function of langerhans cells?
they play an immunological role
What are the 3 types of skin cancer and from which layer does each originate?
- basal cell carcinoma –> basal cell layer, the lower part of the epidermis
- squamous cell carcinoma –> upper outer epidermis
- malignant melanoma
What are warts?
- small non-cancerous growths that appear when you’re skin is infected with a virus from the HPV family
- they appear on fingers, palms, knuckles and knees
except from hair follicles, which appendages are absent from thick skin?
sebaceous glands and apocrine sweat glands
How are the arrector pilli muscles innervated?
- sympathetic nerve fibres
- cause arrector pili to contract and trap heat
What is the dermis made up of?
connective tissue containing irregular bundles of collagen fibres plus networks of elastic fibres
What is a blister?
fluid filled bumps under the epidermis. can fill with pus, blood or serum
What is a dermatome?
an area of skin in which sensory nerves derive from a single spinal root
What are the two types of cutaneous sensory receptors?
- free nerve endings / unencapulated nerve endings / simple receptors
- encapsulated nerve endings/ compound receptors
What are free nerve endings?
-branching axons devoid of surrounding schwann cells
What do merkel cell-neurite complexes do?
mechanoreceptors
What do encapsulated nerve endings do?
mechanoreceptors
Where are ruffini endings found and what is their function?
- located in superficial dermis
- stretching, tension shearing, deformation within joints and warmth
