Anatomy of the Skin Flashcards
What are cells of epidermis? What are their characteristics?
- Keratinocytes
- Make up 90% of the cells in stratum corneum
- produce fibrous protein keratin giving skin elasticity - Melanocytes
- Make up 10-25% of cells in basal layer
- Produce pigment - Langerhans cells - epidermal dendritic cells
- Macrophages that help to activate immune system
- play role in facilitating contact dermatitis - skin allergic reactions - Merkel cells - Tactile cells
- touch receptors
- found mostly in thick skin
Name 5 layers of epidermis.
- Stratum Corneum (cornified layer)
- Stratum Lucidum (clear layer found in thick skin i.e. the palm & sole)
- Stratum Granulosum (granular layer)
- Stratum Spinosum (spinous or prickle layer
- Stratum Basale (basal layer)
Describe epidermal layer superficial to dermis.
- Stratum Basale
- firmly attached to the dermis, consisting of a single row of stem cells; for that reason also called stratum germinativum - undergoes rapid division
- cells travel from basal layer to the surface that takes about 25-45 days
Which layer of epidermis is abundant in melanin granules and Langerhans cells? Describe it.
- Stratum Spinosum
- 8-10 layers of cells wrapped with web-like intermediate pre-keratin filaments attached to desmosomal junctions
- has a “spiny” appearance
Which layer of epidermis consists of flattened cells deprived of nuclei and cytoplasmic organelles? Describe it.
- Stratum Granulosum
- thin 3-5 layers of cells where Keratohyalin and lamellated granules accumulate
- the granules of this layer contain secretion rich in lipids that acts as a sealant as well as protein filaggrin that retains water within keratinocytes
Which layer of epidermis consists of a layer that flakes off? Describe it.
- Stratum Corneum
- consists of 20-30 layers of flat, keratinized membranous sacs and is 3/4 thickness of epidermis
- keratinocytes are surrounded with a mixture of lipids that provide waterproof layer
- protects from abrasions, penetration and makes up a biological/chemical barrier
Which layer of epidermis is present only in thick skin? Describe it.
- Stratum Lucidum
- found only in palms, soles and flexor aspect of digits
- It is a thin and transparent layer superficial to stratum granulosum and consists of a few rows of dead keratinocytes with a main function to reduce friction between layers
Which layer of the skin contain fibroblasts and what is their role?
- Dermis
- Synthesizes most of the extracellular matrix of connective tissue
- active role in damage repair
What are dermal papillae? What can they contain?
They are protrusions of dermal connective tissue into the epidermal layer and can contain one of four:
1) Capillary loops
2) Pacinian corpuscule
3) Meissner’s corpuscule
4) Free nerve endings
Which papillary corpuscule recepts pressure and vibration and which responds to light tough only?
- Pacinian corpuscule pressure and vibration
- Meissner’s corpuscule light touch only
How thick (relatively) is reticular layer of the dermis? What does it contain?
- Reticular layer of the dermis constitutes ~80% of dermis
- contains thick collagen fibers that provide stretch-recoil property as well as resilience and strength
What factors can negatively affect fibroblasts? What condition can it cause?
Some of the factors are steroid hormones regime, diet poor in protein and vitamin C deficiency.
Fibroblasts impairment can cause condition called Keloid - abnormal scaring resulting from from uncontrolled synthesis and excessive deposition of collagen at sites of prior dermal injury and wound repair. Results in prominent scar that extends beyond the wound.
What cells present in dermis can release histamine and heparin? What is their role there?
Among others - mast cells. They are numerous around blood vessels and constitute a line of defense (phagocytes) against microorganisms. Their nucleus is surrounded with vesicles containing histamine, heparin or tryptase responsible for inflammation. Disrupted mast cell (mechanical, chemical or antigen match) releases substances. In severe case can cause anaphylaxis.
What are three substances mostly responsible for the skin color?
1) Melanin
2) Carotene
3) Hemoglobin
+ Other factors.
Where is hypodermis found and what tissue is it made of?
Hypodermis merges with the deep aspect of the dermis. It is made of loose connective tissue.
What are some functions of hypodermis?
It is rich in adipose component, contributes to thermal insulation, acts as a shock absorber and constitutes a store of metabolic energy.
Where are lipomas found? What are they and how are they dealt with?
Benign tumors of fat (hypodermis). Most common soft tissue tumors of adulthood. Usually mobile, slowly enlarging, painless masses. Mostly solitary lesions, but their numerous presence can be caused by rare autosomal disease.
Complete excision is usually curative.
What layer of skin is affected by Erythema Nodosum? What is the cause of this disease?
It is an inflammation of the Hypodermis. Can be idiopathic, medication or autoimmune disease like Crohn’s.
Name four derivatives of epidermis.
1) Sweat glands
2) Sebaceous (oil) glands
3) Hairs and hair follicles
4) Nails
Name 5 structures of the nail. What are their functions?
- Nail plate/body : strong plate of hard keratin
- Nail bed: is a specialized form of skin, and has the same four layers of the epidermis of skin
- Eponychium (cuticle): thickened layer of skin surrounding fingernails
- *Lunule: white crescent at the proximal end
Nail matrix: formed by proliferating cells in the nail root
