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YBOD200 Physiology > Integumentary system > Flashcards

Integumentary system Flashcards

1
Q

How does keratin protect the skin?

A

(tightly interlocked keratinocytes) protects underlying tissues from microbes, abrasion, heat and chemicals.

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2
Q

How does lipid secretion protect the skin?

A

Lipids secreted by lamellar granules inhibit water evaporation from the skin surface (prevents dehydration); and entry (during showers and swims).

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3
Q

How does sebum protect the skin?

A

Sebum from sebaceous glands keep skin and hair from drying out, contains bactericidal chemicals.

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4
Q

How does the skin pH protect the skin?

A

Acidic pH prevents growth of some microbes

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5
Q

How do langerhans cells and macrophages protect the skin?

A

Epidermal Langerhans cells trigger immune system when microbes
invade.
Macrophages in the dermal layer phagocytize bacteria and virus that bypassed epidermal Langerhans cells.

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6
Q

Explain other functions of the skin

A

Regulation of body temperature
• Thermoregulation, homeostatic regulation of body temperature

Reception: general sensations e.g. touch, vibrations, temperature, pain, pressure
• Cutaneous sensations also include thermal sensations (warmth or coolness).

Excretion: sebaceous glands, apocrine glands, eccrine sweat glands • Evaporation of water ~400mL per day.

Absorption: UV sun rays → Vitamin D synthesis

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7
Q

Name the two abundant pigments in the epidermis

A

Carotene
Melanin

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8
Q

Describe Carotene

A

Orange-yellow pigment which accumulates in epidermal cells.
• Mostly found in cells of stratum corneum of light-skinned individuals.

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9
Q

Describe Melanin

A

Consists of 2 types of melanin, red-yellow form (pheomelanin) and
brown-black form (eumelanin).
• Also accumulates in fatty tissues in the deep dermis and subcutaneous layer.

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10
Q

Describe the process of melanin production

A

• Melanocytes produce both melanin types from amino acid tyrosine in the presence of tyrosinase enzyme and package it into intracellular vesicles called melanosomes.
• These melanosomes are transferred into keratinocytes in the basal layer and keratinocytes become pigmented temporarily. These melanosomes are then destroyed by lysosomes inside keratinocytes.

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11
Q

Where does melanosome destruction occur in light-skinned people?

A

Stratum basale and stratum spinosum
And cells in superficial layers loses their pigmentation

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12
Q

Where does melanosome destruction occur in dark-skinned people?

A

Stratum granulosum

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13
Q

T or F: difference in skin pigmentation is due to variation in number of melanocytes in each individual.

A

F

The difference in skin pigmentation amongst people does not reflect different numbers of melanocytes but rather different levels of melanin synthesis.

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14
Q

T of F: albinism is caused by abnormal distribution of melanocytes in the skin.

A

F

People with albinism have normal distribution of melanocytes but the cells are incapable of producing melanin.

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15
Q

Describe freckles

A

Freckles= small, pigmented areas on relatively pale skin.
• These spots typically have irregular border & reflect an area where melanocytes produce larger than average amount of melanin.

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16
Q

What are lentogos?

A

Lentigos= similar to freckles but have regular borders and contain abnormal melanocytes.
• Senile lentigos (liver spots)= variably pigmented area developing on sun-exposed skin surfaces in older individuals with pale skin.

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17
Q

What is the function of melanin?

A

The melanin in keratinocytes protects both epidermis and dermis from harmful effects of
sunlight, ultraviolet (UV) radiation.

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18
Q

How does melanin perform its function?
(Protection of the skin from harmful effect of the UV radiation and sunlight )

A

Melanosomes in keratinocytes perform this function by increasing their concentration in regions around nucleus, melanin pigment acts
as a sunshade, to provide some UV protection for DNA in exposed epidermal cells.

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19
Q

________________ is the partial or complete loss of melanocytes. It may be due to Immune system malfunctioning in which antibodies attack the melanocytes.

A

Vitiligo

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20
Q

Explain the process of keratinisation

A

Newly formed cells in the stratum basale are slowly pushed to the surface.
As cells move from one epidermal layer to the next, they accumulate more and more keratin = keratinization.
• Keratinized cells undergo apoptosis and eventually slough off (takes about 4 weeks from being formed in stratum basale until sloughing off in the surface) and are replaced by underlying cells; and the cycle continues again.

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21
Q

How does the epidermis get its nutrients?

A

Nutrients diffuse from the vascularized dermal layer into the avascular epidermis. Cells in the stratum basale receive these nutrients due to their close proximity to the dermal layer, and are mitotically and metabolically active to produce new keratinocytes.

22
Q

What causes an increase in cell division of the stratum basale?

A

Cell division in the stratum basale increases when outer epidermal layers are stripped off (abrasion, burns). The mechanism regulating this process is not fully understood. However, epidermal growth factor (EGF), a hormone-like protein play a role.

23
Q

Where are the Langerhans cells produced? And where are they located?

A

Arise from the red bone marrow and migrate to the epidermis. They are antigen- presenting cells located in the stratum spinosum of epidermis, can also be found in the dermis.

24
Q

What is the function of langerhans cells?

A

Participates in immune response by defending against microorganism invasion and against superficial skin cancers.

25
Q

Langerhans cells have membrane-bound_________ __________ which contain an integral protein called___________ (a lectin receptor), which assist in engulfing antigens.

A

Birbeck granules
Langerin

26
Q

What is the function of Birbeck granules in the skin immune response?

A

The Birbeck granules degrade and process antigens into epitopes→ Langerhans cells migrate to lymph nodes and present epitopes of processed foreign antigens to T- lymphocytes, hence Langerhans cells are called antigen-presenting cells.

27
Q

Describe Merkel cells

A

Are found in the deep layer of the epidermis, stratum basale. It is in very close proximity with flattened processes of a sensory neuron called tactile disc.
This association makes them sensitive to touch sensation, hence, may act as mechanoreceptors.

28
Q

Function of Meissner’s corpuscles

A

Detection of Fine touch and vibration

29
Q

Function of pacinian corpuscles

A

Deep pressure detection

30
Q

Function of Ruffini endings

A

slow adapting receptors responding to stretching of the skin.

31
Q

How does the body respond to increased body temp?

A

Higher body temperatures in response to high environmental temperatures or heat produced by exercise; eccrine glands increases their sweat production→ increase sweat evaporation from the skin surfaces→ cools the body.

32
Q

How does the body respond to low body temp?

A

In response to low environmental temperatures→ sweat production from eccrine glands decreases→helps conserve heat.
e) Blood vessels in the dermal layer constrict→ decrease blood flow through the skin surfaces→ reduce heat loss from the body.
f) Skeletal muscle contractions (shivering) generate body heat.

33
Q

What causes burns?

A

Heat, electricity, radiation, corrosive chemicals

34
Q

Describe 1st degree burn, give an example

A

Only affects the epidermis; characterized by mild pain and erythema (redness) but no blisters. Skin still functions properly.
E.g mild sunburn

35
Q

How long does a 1st degree burn take to heal?

A

• Healing usually takes 3 to 6 days, may be accompanied by flaking or peeling.

36
Q

Describe a 2nd degree burn

A

It destroys the epidermis and part of the dermis.
Some skin functions are lost. Redness, blisters, oedema, and pain will result.
Blisters: epidermal layer separates from the dermis due to accumulation of tissue fluid between them.
Hair follicles, sebaceous glands, sweat glands, are usually not injured

37
Q

How long does a 2nd degree burn take to heal?

A

If not infected, 2nd degree burns heal (without grafting) within 3 to 4 weeks, but scarring may result

38
Q

Both the 1st and 2nd degree burns are collectively referred to as_________________.

A

partial-thickness burns

39
Q

Describe 3rd degree burn

A

Destroys epidermis, dermis and subcutaneous layer.
• Most skin functions are lost.
• These burns vary in appearance from marble-white to mahogany coloured to charred, dry wounds.
- There are marked oedema, burned region is numb because sensory nerve endings have been destroyed.
- Regeneration occurs slowly, most granulation tissue forms before being covered by epithelium

40
Q

Which degree of burn usually needs skin grafting?

A

3rd degree burn

41
Q

Describe local effect of a burn

A

Local effect of a burn: an injury to the skin directly in contact with the damaging agent

42
Q

Describe systemic effect of a burn

A

Systemic effect: major burns are a greater threat to life. The effect include: a) Large loss of water, plasma, plasma proteins, which cause shock.
b) Bacterial infection
c) Reduced blood circulation
d) Reduced urine production
e) Diminished immune response

43
Q

List common types of epidermal wounds

A

Common types of epidermal wounds include: abrasions, minor burns (sun-burns)

44
Q

Describe epidermal wound healing

A

In response to epidermal injury, basal cells of the epidermis surrounding the wound break contact with the basement membrane.
• Basal cells then enlarge→migrate across the wound.
• The cells appear to migrate as a sheet until advancing cells from opposite side meet.
• When epidermal cells encounter one another, they stop migrating due to cellular response (contact inhibition).

Migration of epidermal cells stops completely when each cell is finally in contact with other epidermal cells on all sides.
• As basal epidermal cells migrate, a hormone called epidermal growth factor (EGF) stimulates basal stem cells to divide and replace ones that have moved into the wound.
• The relocated basal epidermal cells divide to build new strata, thus thickening the new epidermis.

45
Q

List the 4 phases of deep wound healing

A
  1. Homeostasis and inflammation phase
  2. Migratory phase
  3. Proliferative phase
  4. Maturation phase
46
Q

Describe the homeostasis and inflammatory phase of healing

A

Blood clot forms in the wound→loosely unites wound edges.
• Vasodilation and increased blood vessel permeability allows for delivery of neutrophils, monocyte (macrophages), mesenchymal cells (develop into fibroblasts) into the injured area.

47
Q

Describe the migratory phase of healing

A

Clot becomes scab→bridge the wound.
• Fibroblastsmigratealongfibrinthreads→synthesizescartissue (collagen fibers and glycoproteins)→ damaged blood vessels begin to regrow.
• The tissue filling the wound is called granulation tissue.

48
Q

Describe the proliferative phase of healing

A

Extensive growth of epithelial cells beneath the scab as a result of fibroblasts; continued growth of blood vessels.

49
Q

Describe the maturation phase of healing

A

Scab sloughs off once epidermis has been restored to normal thickness.
• Collagen fibres become more organized,fibroblasts decrease in number, blood vessels are restored to normal.

50
Q

The process of scar tissue formation is called______________.

A

Fibrosis

51
Q

Differentiate between the two types of scar tissue

A

Hypertrophic scar: scar that remains within the boundaries of the original wound.

• Keloid (cheloid) scar: scar that extends beyond the boundaries into normal surrounding tissues.

52
Q

Why are scars different from normal skin tissue?

A

More densely arranged collagen fibres, Decreased elasticity, Fewer blood vessels,

Different or same number of hairs, skin glands, or sensory structures as undamaged skin.

Scars are lighter in colour than normal skin due to the arrangement of collagen fibres, scarcity of blood vessels.

YBOD200 Physiology (18 decks)

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