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Skin, hair and nails Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

The skin

A
  • The skin is the largest organ
  • Covers the whole body
  • Water resistant
  • Protects and shapes the body
  • Three layers
  • Epidermis
  • Dermis
  • Hypodermis
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2
Q

Epidermis

A
  • The visible layer of skin
  • Varies in thickness depending on the part of the body
  • Thickest on the soles of the feet and palms of the hand
  • Thinnest on eyelids and nipples
  • The cells on the surface are constantly shed
  • Desquamation
  • They are constantly replaced from below
  • Cells in the basal layer multiply and are pushed up to the surface
  • The basal layer of the epidermis receives its blood supply, nutrients and fluids from the dermis
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3
Q

Structure of the Epidermis 5 layers of epithelial cells

A
  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum germinativum
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4
Q

Stratum corneum

A
  • Most superficial layer of the epidermis
  • Layer exposed to the outside environment
  • Usually 15 to 30 layers of cells
  • Prevent the penetration of microbes and the
    dehydration of underlying tissues
  • The entire layer is replaced during a period of
    about 4 weeks
  • Cells are hardened and flattened (highly keratinized- cornification )
  • Cells are shed periodically (desquamation) and replaced by cells pushed up from the stratum granulosum
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5
Q

Stratum lucidum

A
  • A smooth clear layer
  • Cells contain the clear protein eleiden giving cells a transparent (lucid) appearance
  • Eleiden provides barrier to water
  • Cells dead and flattened
  • Cells are denucleated but not completely hard
  • Cell membranes becoming less visible
  • Found only in the thick skin of the palms, soles and digits
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6
Q

Stratum granulosum

A
  • Cells have a distinct nucleus but cell membranes are dying
  • Contains granules of keratohyalin which are visible in healing tissue after trauma
  • Cells generate large amounts of keratin
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7
Q

Stratum spinosum

A
  • Spiny in appearance
  • Composed of 8-10 layers of cells
  • Cells are living
  • Cell membranes are intact
  • Cells have protruding processes where they join to other cells
  • Capable of mitosis under friction or pressure e.g. soles of the feet and palms of hands
  • Langerhans cells also found in this layer
  • Macrophages that engulf bacteria, foreign particles and damaged cells
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8
Q

Stratum germinativum/basale

A
  • The basal layer
  • Primary site of cell division
  • Cells are living
  • Cuboidal shaped cells
  • Cells take 28-30 days to move from here through the 5 layers of the epidermis before being shed
  • Contains melanin pigment
  • Melanin produced by melanocytes
  • Merkel cells act as receptors (tactile)
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9
Q

Dermis

A
  • Known as the true skin
  • Connected to the blood, lymph supply and nerves
  • Contains sweat and sebaceous glands
  • Made of connective tissue (areolar) that is tough and elastic
  • Contains white collagen fibres and yellow elastic tissue (elastin)
  • Collagen plumps the skin
  • Elastin keeps skin supple and elastic
  • Collagen and elastin diminish with age
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10
Q

Dermis 8 main types of structures present

A
  • Specialised cells
  • Sweat glands
  • Nerve endings
  • Sebaceous glands
  • Hair follicles
  • Blood supply
  • Lymphatic capillary
  • Papilla
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11
Q

Specialised cells

A

Fibroblasts
Mast cells
Histiocytes
Leukocytes

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12
Q

Fibroblasts

A
  • Responsible for the production of areolar tissue, collagen and elastin
  • Responsible for generating connective tissue and allowing the skin to recover from injury
  • Can be damaged by UV light
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13
Q

Histiocytes

A
  • Produce histamine
  • Phagocytic cells
  • Develop into Langerhans cells
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14
Q

Mast cells

A
  • Produce histamine as an allergic response
  • Produce the anticoagulant heparin
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15
Q

Leukocytes

A
  • White blood cells
  • Help fight infection and disease
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16
Q

Nerve endings

A
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17
Q

Sweat glands

A
  • Stretch from deep in the dermis to the outer layer of the epidermis
  • Sweat contains mainly water, urea and salts. Produced by 2 glands
  • Eccrine glands
  • Excrete watery sweat
  • Control body temperature
  • Found all over the body
  • Apocrine glands
  • Found in the groin and armpits
  • Excrete a milky fluid
  • Fluid mixes with bacteria on the skin surface = body odour
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18
Q

Hair follicle

A
  • Travel through the epidermis and dermis
  • Erector pili muscles are attached to each hair – goose pimples
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19
Q

Sebaceous gland

A
  • Connected with hair follicles
  • Produce sebum
  • Fatty acid which keeps the skin moist
  • Lubricates the hair shaft
  • Found in hairy areas but not on the palms of the hands and soles of
    the feet
  • Sweat and sebum combine on the skin surface
  • Form the acid mantle
  • Control bacterial levels
  • Acts as a natural moisturiser
  • Skin pH = 4.5-5.6
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20
Q

Blood supply

A
  • A system of blood vessels including microscopic capillaries
    Plexus = network of vessels
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21
Q

Lymphatic capillary

A
  • Works in conjunction with
    the blood supply
  • Carries waste products away
    from the area
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22
Q

Papilla

A
  • Small conical projections at the base of the hair
  • Contain blood vessels and nerves which supply
    the hair with nutrient
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23
Q

Functions
of the skin

A

Secretion
Heat regulation
Absorption
Protection
Elimination
Sensation
Vitamin D formation
Melanin formation

24
Q

Secretion

A
  • The skin secretes sebum from the sebaceous glands
  • Sebum lubricates the hair shafts when combined with perspiration
  • Acts as a protective barrier against bacteria
25
Q

Heat regulation

A
  • Normal body temperature is maintained at 37oC
  • Muscles, liver and digestive organs are involved in heat production
  • Heat is absorbed and maintained in the subcutaneous layer of adipose tissue
  • Cooling
  • Vasodilation
  • Capillaries dilate allowing more blood to reach the
    surface of the skin
  • Pores dilate allowing heat to be lost from the body
  • Hyperaemia
  • Sweating occurs simultaneously with the
    evaporation of perspiration cooling the body
  • Warming
  • Vasoconstriction
  • Moves blood away from the extremities to the
    major organs
  • Capillaries constrict and also pores. Skin appears
    pale
  • Shivering
  • Goose pimples
26
Q

Absorption

A
  • The skin is a waterproof covering
  • Some substances e.g. drugs and essential oils can penetrate the skin
  • Amount of penetration is affected by the health and condition of the skin
27
Q

Protection

A
  • The skin is a continuous barrier
  • Prevents entry of microorganisms
  • The skin surface has an acidic pH which inhibits bacterial production
  • Splits, cuts, tears and irregularities increase the risk of infection
  • Melanin protects against UV light damage to tissues
  • Sensory nerve endings warn of possible trauma
  • Reflex action prevents greater damage
28
Q

Elimination

A
  • Some toxins are eliminated from the body through sweat
  • These include waste salts and water
29
Q

Sensation

A
  • Specialised nerve endings found in the dermis make the body aware of its surroundings
  • Pain, cold, heat, pressure, touch
  • Found at different levels in the skin
  • Help prevent trauma to the skin and underlying structures
30
Q

Vitamin D formation

A
  • Vitamin D is essential for the formation and maintenance of bone
  • Vitamin D production is stimulated by the ultraviolet light * Converts 7 -dehydro - cholesterol in the sebum into vitamin D
  • Circulates in the blood * Excess is stored in the liver
  • Lack of vitamin D can result in rickets in children
31
Q

Melanin formation

A
  • Produced by melanocytes in the basal layer of the epidermis
  • Production stimulated by the hormone MSH
  • Causes darkening of the skin
  • Melanin production is increased by exposure of the skin to ultraviolet rays
  • Protects against UV light damage to tissues since dark colours absorb
    radiation
  • In people with dark skin, the melanocytes continuously produce large
  • amounts of melanin
  • The melanocytes of light-skinned people produce less melanin
32
Q

Hair follicles

A
  • Hair follicles travel through the epidermis and dermis
  • Erector pili muscles are attached to each hair
  • Goose pimples form when hair is pulled upright to keep the body warm
32
Q

where does Hair grow

A

Hair grows in follicles which are in the dermis

33
Q

Sebaceous glands

A
  • Associated with each hair follicle
  • Produce sebum – fatty acid
  • Keeps skin moist and lubricates the hair shaft
  • Sweat + sebum = acid mantle
  • Protective shield which helps to control bacterial levels
34
Q

Hair layers

A

Cuticle
* The outer layer which consists of overlapping, transparent keratin scales
Cortex
* Middle layer consists of elongated cells which contain melanin = hair colour
Medulla
* Centre of the hair and is composed of loosely connected keratinsed cells

35
Q

Hair follicle layers

A

1-Inner root sheath
* Includes the cuticle which interlocks with the cuticle of the hair
* Huxley’s layer – 2 or more cell thick
* Henle’s layer – 1 cell thick
2-Outer root sheath
* Forms the follicle wall
* A continuation of the growing layer of the epidermis of the skin
3-Vitreous membrane
* Separates the connective tissue from the outer root sheath
4-Connective tissue
* Surrounds both the follicle and the sebaceous gland providing both sensory and blood supply
* Dermal papilla supplies the follicle with the blood and nourishment required for growth

36
Q

Types of hair

A

1-Lanugo hair
* A coat of fine soft downy hair develops about 6 months before birth
* Hair grow at the same time and rate
* Normally shed 1 month before birth
2-Vellus hair
* Follicles have no sebaceous glands
* Distributed over most of the body except palms, soles, lips and nipples
* Pale in colour
* 1-2cm
3-Terminal hair
* Produced by hair follicles with sebaceous glands
* Grows on the head, areas of the face, underarms and pubic area

37
Q

Hair growth cycle

A
  • The hair that we describe as growing is actually mostly dead
  • The hair grows at its base, the hair bulb in the follicle
  • The hair we see about 1cm from the skin is a dead shaft of keratin
  • The hair will grow from its base for many years and then falls out
  • The follicle rests for a while and then resumes production of a new hair
  • 3 stages
  • Anagen → Catogen → Telogen
38
Q

Anagen

A
  • Growing ohase
  • Can last from 2-7 years
  • Hair grows vigorously – 1cm/month
  • Hair can grow quicker in summer
  • Untrimmed hair can grow to 1 m long
39
Q

Anagen

A
  • Hair bulb generates melanin
  • Melanin gives the hair its colour
  • Length of this stage is an inherited characteristic
40
Q

Catagen

A
  • Lasts for 2-4 weeks
  • The follicle rests
  • Also called the intermediate phase
  • Bulb produces neither hair cells nor pigment
  • Bulb shrinks slightly becoming less deep
41
Q

Telogen

A
  • Lasts about 3 months
  • A new hair begins to grow in the hair follicle
  • The old hair will be shed during brushing or washing
  • Hair ready to enter into anagen phase after telogen
42
Q
  • Hormonal factors affecting the growth cycle
A
  • Changes in androgens affect the hair, its growth rate and thickness
  • Oestrogens slow hair growth and extend the growing phase of the hair growth cycle
  • During puberty a rise in androgen levels hair in the pubic area and underarms changes to recognisable terminal hair
  • Later in life changes in hormone levels increase face, chest, nose and ear hair growth
  • In women hair growth can be affected by hormonal changes during pregnancy and menopause
  • Thyroid hormone accelerates hair growth
43
Q

Diet and environmental factors affecting the growth cycle

A
  • General diet and specific dietary deficiencies affect hair growth
  • Poor diet can lead to hair loss
  • E.g. crash dieting and anorexia
  • Anaemia, alcohol consumption, lack of Vitamin B or Zinc also cause problems
44
Q

Nails

A
  • Fingernail/nail plate protects the end of the fingertip
  • Enhances sensitivity of the nerves in the fingertip
  • Made of translucent keratin
45
Q

Components
of the nail
system

A
  • Free edge – part extending beyond the end of the skin of the fingertip
  • Hyponchium- forms a seal between the free edge of the nail and skin of fingertip
  • Peronchyium
  • Eponchyium
  • Nail plate – protective shield of translucent keratin for the nail bed
  • Cuticle -layer of skin growing from the base of the nail over the nail plate. Protects the matrix from infection
  • Nail bend
  • Nail folds
  • Matrix – cells of the nail plate and nail bed are produced here. Keratin cells for the nail plate and bed are produced here pushing older cells forward
  • Mantle
  • Lunula
  • Nail wall
  • Nail groove
46
Q

Factors affecting nail growth

A

Health
*Shape integrity and colour of the nail can be affected by diseases of the lung, heart, kidney, liver or thyroid
Age
*Growth slows with age. Protein in the nail becomes more brittle and prone to splitting
Diet
*Diet does not generally cause abnormal nail changes except in cases of severe Diet malnutrition
Medication
*May affect the rate at which the fast growing cells of the body reproduce
Climate
*Blood increases in hotter climates increasing nail growth
Damage
*If the matrix is damaged nail growth can be affected
Lifestyle
*Environmental factors eg hands in water or chemical solutions

47
Q

Burns

A
  • A burn is tissue damage
  • Burns of the skin may be caused by flames, hot water or steam, sunlight, electricity, or corrosive chemicals
  • Bacterial infection is a serious problem for burn patients as pathogens may get into the blood (septicemia) and quickly spread throughout the body
  • Dehydration may also be fatal
48
Q

Squamous and basal cell carcinoma

A
  • The most common forms of skin cancer
  • Lesions are visible as changes in the normal appearance of the skin, and a biopsy is used to confirm the diagnosis
  • Basal cell carcinomas account for about 78% of all skin cancers
  • Tumours arise from cells in the stratum basale of the epidermis and rarely metastasize
  • Squamous cell carcinomas account for about 20% of all skin cancers
  • Tumours arise from squamous cells of the epidermis, and they have a variable tendency to metastasize.
49
Q

Malignant melanoma

A
  • Malignant melanoma is a more serious form of skin cancer, which begins in melanocytes
  • Any change in a pigmented spot or mole (nevus) should prompt a person to see a doctor
  • Melanoma is serious because it may metastasize very rapidly to the lungs, liver, or other vital organ
50
Q

Psoriasis

A
  • A skin disorder that causes skin cells to multiply up to 10 times faster than normal
  • The extra skin cells form scales and red patches that are itchy and sometimes painful
  • May cause thickened, pitted or ridged nails
  • There is no cure for psoriasis, but symptoms can be managed
51
Q

Eczema (atopic dermatitis)

A
  • A condition where patches of skin become inflamed, itchy, red, cracked, and rough
  • Eczema sometimes precedes asthma and hayfever
52
Q

Nail white spots (Leuconychia)

A
  • Common condition commonly caused by injury to the nail matrix allowing an air pocket to form
    Leukonychia striata - white streaks that appear on the nails due to trauma, manicuring or systemic diseases
53
Q

Discoloured nails

A

Yellow nails – most commonly caused by a fungal infection
Blue nails – poor circulation, anaemia or a heart problem
Black nails – usually the result of heavy bruising

54
Q

Alopecia areata

A
  • Known as spot baldness
  • A condition in which hair is lost from some or all areas of the body
  • A common autoimmune disorder
    *Can lead to the complete loss of hair on the scalp (alopecia totalis) or, in extreme cases, the entire body (alopecia universalis )

biology (15 decks)

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