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BN541 Topic 1 > Unit 8 - Skin > Flashcards

Unit 8 - Skin Flashcards

1
Q

what are the 3 layers of the skin?

A
  1. epidermis
  2. dermis
  3. hypodermis
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2
Q

basic structure and function of the epidermis

A
  • Epithelial layer
  • Composed of stratified squamous epithelium
  • Avascular
  • Average thickness = 0.1 mm
  • Thick skin average = 1-2 mm

• Primary barrier to:

  • Mechanical damage
  • Desiccation
  • Microbial invasion
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3
Q

basic structure and function of the hypodermis

A
  • Aka superficial fascia or subcutaneous layer
  • Loose, irregular connective tissue with varying proportions of fat.
  • Fatty layer- acts as shock absorber.
  • It anchors skin with the underlying structures
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4
Q

what are the 5 layers of the epidermis (from deepest > superficial)

A
  1. Stratum basale /germinativum
  2. Stratum spinosum
  3. Stratum granulosum
  4. Stratum lucidum (present only in thick skin)
  5. Stratum corneum

Come Lets Get Sunburnt

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5
Q

Structure and function of Stratum basale

A

Structure: Composed of single layer of cuboidal or columnar stem cells

Function:
• Germinating layer from which all the keratinocytes are formed.
• capable of continual cell division and production of all the keratinocytes in the epidermis.
• Also contains melanocytes & merkel discs

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6
Q

Structure and function of Stratum spinosum

A

Structure:
• Contains 8 – 10 rows of many-sided cells that fit closely together.
• The keratinocytes have spine-like projections which holds the cells together.

Function:
• These cells obtain melanin from long processes of melanocytes.
• Langerhans’s cells are scattered among the keratinocytes

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7
Q

Structure and function of Stratum granulosum

A

Structure:
• Composed of 3 – 5 rows of flattened keratinocytes.

Function:
• Cells contain darkly stained granules of keratohyalin, a precursor of keratin.
• Nuclei are in various stages of degeneration
• Cells can no longer carry on vital metabolic reactions, and they die.

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8
Q

Structure and function of Stratum lucidum

A

• Normally only found in the thick skin of the palms and soles

Structure:
• Composed of 3 – 5 rows of clear, flat, dead keratinocytes

Function:
Contains droplets of an intermediate substance that will become Keratin.

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9
Q

Structure and function of Stratum corneum

A

Structure:
• Consists of 25 – 30 rows of flat, dead keratinocytes filled with keratin.

Function:
• Cells are continually being shed and replaced by cells from the deeper layers.
• Serves as an effective barrier against light, heat, bacteria, and chemicals.

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10
Q

what are the 4 types of cells found in the epidermis?

A
  1. Keratinocytes
  2. Melanocytes
  3. Langerhans’s cells
  4. Merkel cells
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11
Q

Function of keratinocytes

A
  • Comprise 90% of cells in epidermis
  • Produce keratin - fibrous, waterproof protein that gives the epidermis its protective properties, strength, and toughness
  • Keratinocytes divide and increase in number and keep moving to the superficial layers
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12
Q

Function of melanocytes

A
  • Make up about 8% of cells
  • Produce melanin which they transfer to keratinocytes
  • Melanin absorbs UV radiation and contributes to skin colour
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13
Q

function of Langerhans’s cells/dendritic cells

A

• Arise from bone marrow and migrate to epidermis.
• Involved in the immune response
- Ingest foreign substances
- Present antigens and stimulate production of T cells.
• Damaged by UV radiation

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14
Q

Function of Merkel cells/tactile cells

A
  • Located in the deepest layers of epidermis
  • Sensory reception for touch
  • Connected to sensory nerve fibres which carries message to brain
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15
Q

what gives rise to fingerprints?

A

Friction ridges in the palms and soles along with sweat

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16
Q

structure of dermis

A
  • Composed of connective tissue containing thick bundles of collagen and elastin fibres
  • The blood supply to the skin is all in the dermis.
  • The nerve supply serves the dermis and epidermis.
  • Contains glands and hair follicles.
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17
Q

what structures are located in the dermis?

A
  • abundant nerve fibres
  • blood vessels
  • lymphatic vessels
  • Hair follicles
  • Sweat glands
  • Sebaceous glands
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18
Q

what are the 2 layers of the dermis

A
  1. Papillary region

2. Reticular region

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19
Q

describe the papillary region of the dermis

A
  • Outer portion of the dermis
  • Approx. 1/5th of the total thickness of the dermis
  • Composed of areolar connective tissue with interlacing collagen and elastic fibres
  • Surface is covered in papilla/ dermal papilla which indent the epidermis above
20
Q

describe the reticular region of the dermis

A
  • Inner portion of the dermis

* Coarse, dense, irregular connective tissue with interlacing bundles of collagen and elastin.

21
Q

what are the 4 cell types of the dermis?

A
  1. Fibroblasts
  2. Mast cells
  3. Macrophages
  4. Adipocytes
22
Q

describe fibroblasts

A

Undifferentiated cells in connective tissue that give rise to various precursor cells such as collagenoblasts.

23
Q

describe mast cells

A
  • Found in areolar connective tissue

* Release histamine, which causes dilation of small blood vessels during inflammation.

24
Q

describe macrophages

A
  • Derived from monocytes.

* They phagocytose foreign materials.

25
Q

describe adipocytes

A

Fat cells that contain a large fat vacuole which potentially can contain triglycerides.

26
Q

describe the role of sebaceous glands

A
  • Secrete oily substance called sebum on to skin and hair.
  • Most open into hair follicles
  • Arrector pili muscle contractions force sebum out of the hair follicles to the skin.
  • Sebum aids in heat retention, softens skin and makes hair supple.
  • Fatty acids in sebum make skin slightly acidic which controls bacterial growth.
27
Q

what are the 2 types of Sudoriferous glands?

A
  • Eccrine and Apocrine
  • Each type consists of a coiled tube that straightens and opens out on the surface of the skin via a duct and a pore.
  • There are about 3 million sweat glands per person.
28
Q

describe Eccrine (Merocrine) glands

A
  • Most numerous type
  • abundant on the palms, soles of the feet and forehead
  • Its secretion is clear sweat containing water, NaCl, urea, lactic acid and breakdown products of food substances such as garlic.
  • Function is to cool the body by evaporation of the sweat.
29
Q

describe Apocrine glands

A
  • Approximately 2000 glands- located in axillary, anal, genital areas.
  • Become functional only at puberty.
  • Their sweat is thicker due to presence of fatty substances and proteins which is consumed by bacteria.
  • Characteristic odour is caused by bacterial waste.
30
Q

describe Ceruminous glands

A
  • Type of modified sweat gland

* Found in lining of the external ear canal which produce a waxy secretion.

31
Q

What is the structure and function of the hypodermis

A

Structure
• It is composed of a mixture of adipose tissue and loose areolar tissue.
• Interlaced with blood vessels and nerves

Function
• Main structural support for the skin
• Insulation
• Shock absorption

32
Q

what are the 4 types of protection offered by the skin

A
  1. Physical
  2. Osmotic
  3. Bacterial
  4. Ultraviolet Radiation
33
Q

describe the physical protection provided by skin

A

Skin forms the major interface between internal & external environments and protects from physical abrasion.

34
Q

describe Osmotic protection provided by skin

A

Sebum & keratin waterproof skin and restricts flow of water in either direction.

35
Q

describe bacterial protection provided by skin

A
  • Intact skin forms first line of defence against infection.

* Fatty acids in sebum create an acid environment = barrier to invasion by microorganisms.

36
Q

describe UV protection provided by skin

A

• Melanin absorbs U.V. light as it forms a protective veil over the nucleus preventing damage to genetic material.

37
Q

what are the 3 ways the skin controls the regulation of body temperature?

A
  1. Evaporation
  2. Changes in blood flow
  3. Erection of hair
38
Q

what are the 3 ways the skin in involved in sensation

A
  1. Temperature
  2. Touch
  3. Pressure and Pain
39
Q

what are 7 other functions the skin has?

A
  1. Endocrine function: vitamin D
  2. Blood reservoir: 8-10% of blood in dermis at rest
  3. Absorption: drug admin
  4. Excretion: sweat
  5. Immunity: Langerhans’ cells are ‘Antigen presenting cells’
  6. Social communication: vascular and muscular responses
  7. Locomotion: friction, grip, movement
40
Q

what are the 3 main structures of the nail?

A
  1. Free edge of nail
  2. Body of nail/nail plate: made of a plate of dead tightly compressed cells packed with hard keratin
  3. Root of nail: Proximal part covered by skin fold.
41
Q

Function of hair

A
  • Hair on the scalp protects head from physical injury, from ultraviolet radiation, reduces heat loss.
  • Eyebrows, eyelashes, nasal hairs and hairs of external ear canal prevent entry by foreign particles.
  • Hair on the skin sense insects before they bite or sting
42
Q

Structure of hair

A

• Composed of dead, keratinised (hard keratin) cells.
• Shaft: Part that emerges above the surface of the skin.
• Root: Embedded in the skin, generally in the dermis.
• Both made of 3 concentric layers
Inner medulla
Middle cortex
Outer cuticle

43
Q

what is the hair papilla?

A
  • A small connective tissue peg that protrudes into the hair bulb.
  • Contains blood capillaries and nerves.
44
Q

what is the hair matrix

A
  • Actively dividing cells that produces hair.

* New cells are formed at the base, older cells and parts are pushed upwards.

45
Q

structure and function of hair follicles

A

• Hairs develop in follicles.
• Follicle surrounds the root of the hair (under skin)
• Function:
- support, nourish and protect hair.
• Structure:
- A root hair plexus of sensory nerves surrounds the base of each follicle.
- Each hair follicle is associated with arrector pili muscles.

BN541 Topic 1 (10 decks)

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