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Disease Processes > Biology of skin > Flashcards

Biology of skin Flashcards

1
Q

Epithelium type of the epidermis?

A

Stratified squamous epithelium keratinised

Cornified

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2
Q

Keratinocytes secrete? What is the function of these proteins

A

Keratin

Contribute to the formation of the ECM and provide mechanical strength to the skin

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3
Q

Which cells are found within the epidermis? Function of each?

A
  • Keratinocytes = form 95% of the epidermis!
  • Melanocytes - Secrete melanin which is responsible for skin pigmentation and protection against UV
  • Langerhans cells - APCs/Dendritic cells. Responsible for immune defence. Arise in the bone marrow and migrate via the blood
  • Merkel cells - Receptor cells. Responsible for fine sensation as they are in association with nerve fibres
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4
Q

What are the different layers of the epidermis?

A
  • Basal layer
  • Spinous layer
  • Granular layer
  • Cornified layer
  • YOU WILL NOT FIND BLOOD VESSELS HERE
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5
Q

Characteristics of the epidermis’ basal layer

A
  • Cuboidal shaped DIVIDING cells
  • Stem-cell like properties (regenerating/proliferating)
  • Cells differentiate upwards!!
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6
Q

Characteristics of the epidermis’ spinous layer

A
  • Prominent intracellular keratin filaments & desmosomes (linking them to adjacent cells = looks like a spike)
  • Further differentiation of cells here leads to more keratin being made
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7
Q

Characteristics of the epidermis’ granular layer

A
  • Contain keratohyalin granules. These bind intermediate keratin filaments together
  • Develop lamellar bodies which contain the lipid components important for the hydrophobic barrier function of skin
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8
Q

Characteristics of the epidermis’ cornified layer?

A
  • Cells that have differentiated upwards from the granular layer undergo apoptosis. So this layer has 15-20 layers of dead cells called CORNEOCYTES, which fall apart and are shed
  • This layer is responsible for the barrier function of the skin. It is rich in lipids and insoluble
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9
Q

Difference between thick and thin skin?

A
  • Thick skin has a larger/more well-defined cornified layer
  • Thick skin has an undulating basement membrane, making it more liable to abrasion
  • Thick skin does not contain hair or sebaceous glands
  • Thin skin is more abundant
  • Thick skin contains a 5th layer called the stratum lucidum
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10
Q

Layers of the dermis?

A
  1. Papillary region

2. Reticular region

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11
Q

Characteristics of the dermis’ papillary region?

A
  • UPPERMOST LAYER
  • Loose connective tissue made of collagen and elastin fibres
  • Contains capillary networks, lymphatics and nerve endings
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12
Q

Characteristics of the dermis’ reticular region?

A
  • DEEPER LAYER
  • Thicker than the papillary region and makes up majority of skin overall
  • Dense, irregular connective tissue containing thick bundles of collagen fibres
  • Contains fibroblast cells (secrete ECM)
  • Contains immune cells (mast cells, macrophages, lymphocytes)
  • Provides strength to our cells
  • Contains vessels, nerves, nerve endings
  • Site of various skin appendages e.g hair follicles, sweat and sebaceous glands
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13
Q

Characteristics of the hypodermis?

A
  • Made of mature adipose tissue
  • Not part of the skin, lies below the dermis
  • Functions as an insulator, protector and energy store
  • Attaches the skin to underlying bone and muscles, supplies it with vessels and nerves
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14
Q

Physiology of the skin?

A
  1. Protection: barrier against pathogens, mechanical damage, infectious agents, UV radiation
  2. Sensation: Nerve endings for temperature, touch, pressure, vibration, and pain
  3. Thermoregulation: Eccrine (sweat) glands and dilated blood vessels aid heat loss. Erector pili muscles adjust the angle of the hair shafts to change the degree of insulation provided by hair
  4. Control of evaporation: Skin provides a dry and semi-impermeable barrier to reduce fluid loss
  5. Storage and synthesis: Storage centre for lipids and water. Vit D synthesis by keratinocytes
  6. Absorption: O2, N2, CO2 can diffuse into the epidermis in small amounts
  7. Water resistance: Water resistant barrier so essential nutrients are not washed out of the body
  8. Contains appendages: hair, nails, and glands
  9. Immunological role: Langerhans cells (APC) and lymphocytes in the epidermis. Macrophages, mast cells and lymphocytes in the dermis.
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15
Q

3 stages of hair growth?

A
  1. Growth phase
  2. Transition phase: hair slows down in terms of growth, loosens in attachment to the hair follicle. It is then shed and the follicle becomes s resting follicle
  3. Resting phase: Resting follicle, it will eventually regrow and enter the growth phase once more
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16
Q

Function of sebaceous glands?

A

Responsible for secreting sebum, an oily extract which coats our hair, making it soft and waterproof

  • Epithelium is continuous with the basal layer of the epidermis
17
Q

Eccrine sweat glands location & role? What makes up sweat?

A
  • Found in deep reticular dermis. It is a coiled-tubular gland
  • Secrete water/sweat directly onto the skin by merocrine secretion = thermoregulation
  • Water, Na+, Cl-, urea, low mol wt. metabolites
  • Epithelium is continuous with the basal layer of the epidermis
18
Q

Function and location of apocrine glands?

A
  • Coiled-tubular structures but DO NOT release contents onto the skin surface, they are more associated with hair follicles.
  • Localised to axillae, mammary and groin regions. Thought to become active during puberty.
  • Contribute to body odour.
  • Epithelium is continuous with the basal layer of the epidermis
19
Q

How do burns heal? Superficial, partial deep and deep burns.

A

Superficial: Basal cells from the hair roots and sweat skin glands move to the surface of the burn and build a new surface layer of skin. Epidermal growth factor stimulates basal cells to divide and replace the ones that have moved into the wound.

Partial deep: Cells from hair roots are the only ones contributing to skin healing because most of the skin glands were damaged.

Deep burns: All layers of skin are damaged and the wounds will not heal alone

  • If the wound is TOO deep, clinical intervention may be required = skin graft
20
Q

Deep wound healing process (extending into the dermis)

A
  1. Haemostasis: Fibrin clot formation to stop blood loss and fill the wound
  2. Inflammation: Removal of bacteria and clean damaged tissue
  3. Fibroplasia: Fibroblasts lay down new collagen, accompanied by angiogenesis
  4. Epithelialisation: Migration and mitosis of keratinocytes from edge of the wound and grow in size to find a neighbour, form tight junctions, restoring a new basal layer
  5. Remodelling: Initial tissue is replaced through turnover to create a stronger structure

Disease Processes (31 decks)

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