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Human Anatomy > The integumentary system lectures 17&18 > Flashcards

The integumentary system lectures 17&18 Flashcards

1
Q

The integumentary system

A

Composed of the skin, hypodermis, glands, hair and nails

• Key function: ‘Protects the body from the external environment

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2
Q

functions of the integumentary system

A

protection
regulation
sensation (detects stimuli)
metabolic

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3
Q

How does the integumentary system support other systems?

A

• Synthesises vitamin D3, which governs for Ca and P absorption
(digestive system) and which is required for bone maintenance and growth (skeletal system) and muscle contraction (muscular
system)
• Vitamin D 3 is also a precursor of the hormone calcitrol (endocrine system)
• Receptors in dermis and deep epidermis provide sensory input to nervous system
• Keratinised epidermis limits fluid loss through skin, maintaining
body’s water balance (urinary system)
• Provides physical barrier that prevents entry of pathogens;
Langerhans cells and macrophages resist infection (immune system)

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4
Q

Components of the integumentary system

A

skin

hypodermis

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5
Q

skin

A 
made up of 2 layers
• Epidermis
– Greek epi, ‘upon’ and derma, ‘skin’
– Thick, epithelial superficial layer
• Dermis
– Fibrous connective tissue
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6
Q

hypodermis

A
  • Greek hypo, ‘under’
  • Subcutaneous fibrous connective tissue

Lies between dermis and underlying organs
Consists of
– areolar tissue (general connective tissue)
–adipose tissue (similar to areolar tissue, but with many more fat cells) – more predominant
Anchors skin to underlying muscles

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7
Q

what cells is the epidermis made up of?

A
  1. Keratinocytes (~90% of epidermis)
  2. Melanocytes (~8%)
  3. Merkel cells (~1%)
  4. Langerhans cells (~1%)
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8
Q

keratinocytes

A
  • Most abundant cell of the epidermis
  • Develop from stem cells at the base of epidermis
  • Pushed up as new cells form beneath them; eventually die
  • Produce keratin, a fibrous protein – tough, scaly, water-resistant
  • Keratinocytes also produce antibiotics and enzymes to detoxify chemicals to which the skin is exposed
  • Millions of these cells rub off every day; the epidermis is totally replaced about every 30 days
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9
Q

Melanocytes

A
  • Originate from embryonic cells called neural crest cells
  • Produce the skin pigment, melanin, in granules called melanosomes
  • Melanin transferred to nearby keratinocytes, so keratinocytes can contain more melanin than melanocytes
  • Melanin shields cell nuclei from U V radiation, which can damage DNA and cause cancer
  • In Caucasians, melanin digested by lysosomes just above the stratum basale
  • Skin colour differences due to levels of melanin, not numbers of melanocytes
  • In all but the darkest people, melanin increases with exposure to UV; this is suntanning
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10
Q

Merkel cells

A
  • Associated with sensory nerve endings – lots on finger tips and oral cavity
  • Play a role in sensing touch
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11
Q

Langerhans cells (epidermal dendritic cells)

A
  • Star-shaped
  • Part of immune system – unique population of tissue-resident macrophages
  • Arise in bone marrow and migrate to epidermis
  • Take up foreign proteins (antigens) that have entered the epidermis, and transport them to killer T lymphocytes (Antigen-presentation cells).
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12
Q

layers of the epidermis

A 
Thick skin (palms and soles)
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale (basal layer)
Thin skin (everywhere else)
• Stratum corneum
• Stratum granulosum
• Stratum spinosum
• Stratum basale (basal layer)
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13
Q

Stratum corneum

A
  • Thick; thicker in thick skin than in thin skin
  • 20-30 cells thick, accounting for about 75% of epidermis
  • High in dead keratinocytes, filled with keratin after nuclei/organelles disintegrate after cell death
  • Keratin and thickened plasma membrane of cells protect the skin against abrasion/penetration
  • Glycolipid between cells keeps layer waterproof
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14
Q

Stratum lucidum (clear layer), or transition layer

A
  • Thick skin only; absent in thin skin
  • Thin translucent band under light microscope
  • Consists of a few rows of dead keratinocytes
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15
Q

Stratum granulosum (granular layer)

A
  • Consists of 3-5 layers of flattened keratinocytes
  • Contain waterproofing glycolipid
  • Above the stratum granulosum, cells are too far from dermal capillaries and die
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16
Q

Stratum spinosum (spiny layer)

A
  • Keratinocytes in this layer typically have spiny extensions; however these do not occur in living cells – they are an artefact created as cells shrink during preparation
  • Contain thick bundles of intermediate filaments called tonofilaments
  • Also contain Langerhans cells
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17
Q

Stratum basale (basal layer)

A
  • Deepest layer of epidermis
  • Continually renewing cell population
  • Single layer of cells with the youngest keratinocytes
  • Also contains occasional Merkel cells
  • 10-25% of cells in basal layer are melanocytes
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18
Q

the dermis

A

• Strong, flexible connective tissue
• Consists of
o fibroblasts ( secrete proteins that make collagen/reticular/elastic fibres – provides support)
o macrophages (non-specific phagocytes)
o mast cells (secretory cells)
o scattered white blood cells
• Contains sebaceous glands, sweat glands, hair follicles - APPENDAGES
• Consists of two layers:
– Superficial papillary layer (20% of dermis)
– Deep reticular layer (80% of dermis)

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19
Q

appendages of the skin

A 
The integumentary system includes the following derivatives of the epidermis:
• Hair and hair follicles
• Sebaceous glands
• Sweat glands
• Nails
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20
Q

hair

A
  • Hair is a flexible strand made of dead, keratinised cells
  • This keratin is harder than the keratin found in the epidermis
  • The life span of scalp hairs is approximately 4 years; in the eyebrows, only about 4 months
  • Scalp hair is not in synchrony - otherwise, approximately every 4 years all of the hair on your head would fall out at once!
  • Since chemotherapy drugs target rapidly dividing cancerous cells, they also destroy hair stem cells, leading to baldness
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21
Q

Hair colour and shape

A
  • Hair pigment (either black-brown, or rust) is made by melanocytes at the base of the follicle and transferred to the cells of the hair root
  • The proportions of these two pigments determine hair colour
  • White or grey hair is due to an absence of melanin, and its replacement in the shaft with air bubbles
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22
Q

sebaceous glands

A

• Occur over the whole body, except the palms of the
hands and the soles of the feet
• Produce oily sebum; this accumulates within secretory epithelial cells and is released when these cells burst
• Mostly associated with hair follicles
• Softens and lubricates hair and skin, slows water loss and kills bacteria

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23
Q

acne

A
  • In acne, too much sebum is produced and blocks the sebaceous gland
  • Sebum forms ‘whitehead’; this can dry and oxidise to form a blackhead
  • Blocked sebaceous glands are more susceptible to infection leading to inflammation: spots
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24
Q

sweat glands

A

• Humans have > 2.5 million sweat glands
• All over skin, except nipples and external genitalia
• We produce about 500ml of sweat per day
• Sweat glands are unique to mammals, and prevent overheating
• Sweat is 99% water, with some salts plus urea, ammonia and uric acid
• Acidic, so also retard growth of bacteria
• Two main types of sweat glands (eg mammary glands are modified sweat glands):
– Eccrine glands
– Apocrine glands

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25
Q

Eccrine glands

A
  • More numerous
  • Produce true sweat
  • Most abundant on palms, soles of feet and forehead
26
Q

Apocrine glands

A
  • Axillary, anal and genital areas
  • Larger
  • Produce sweat which also contains fatty substances and proteins
  • Initially odourless but can be decomposed by skin bacteria and starts to smell: B O!
  • Begin to operate at puberty
27
Q

nails

A

• Modified part of epidermis, comprising hard
keratin (as in hair)
• Nails comprise:
– distal free edge
– body
– proximal root embedded in the skin
• Rests on epidermal nail bed, corresponding to deeper parts of epidermis; the nail itself corresponds to the outer, keratinised layers
• Nails appear pink because of rich blood supply, except at the nail matrix, the actively growing part, which is thicker and appears as a white crescent: the lunula

28
Q

Developmental disorders of the integumentary system

A
  • Chromosomal abnormalities such as trisomy 21 (Down syndrome) can lead to distinctive ridge patterns on hands and feet
  • These include so-called simian lines, which are otherwise rare
29
Q

Ichthyosis

A

refers to a group of disorders resulting from excessive keratinisation
o Skin is hard and dry, with some resemblance to scales

30
Q

Angiomas

A

of the skin (which may not be true tumours) arise
transitory or surplus blood/lymphatic vessels persist
o Those composed of blood vessels may be arterial, venous, cavernous or mixed
o True angiomas are benign endothelial tumours: birthmarks

31
Q

Albinism

A

skin, hair and retina lack pigment (the iris may be pigmented) because melanocytes fail to produce melanin because of an enzyme deficiency

32
Q

Macule

A

Flat lesion with skin discolouration, <1cm

33
Q

Nodule

A

Round, elevated lesion,

>1cm

34
Q

Plaque

A

Superficial, elevated flat lesion > 1cm

35
Q

Vesicle

A

Fluid filled lesion (blister) <1cm

36
Q

Bullae

A

Fluid filled lesion > 1cm

37
Q

Pustule

A

Vesicle containing pus (inflammatory cells)

38
Q

Papule

A

Superficial solid elevated lesions <1cm

39
Q

vitiligo

A

Pale white patches on skin – lack of melanin

40
Q

Freckles (ephelides)

A

Small, light brown/tan mark on the skin
Particularly common in fair-skinned individuals
Inherited characteristic – produce more pigment (melanin)
Typically sun-exposed sites such as the nose and cheeks, can fade during winter months

41
Q

Melasma, also called “mask of pregnancy”

A

Skin pigmentation – dark, blotchy skin in exposed areas – typically in young women during pregnancy

42
Q

lentigo

A

Type of freckle:
o tan/brown/black spot
o darker than freckles
o DOES NOT FADE IN THE WINTER

43
Q

NAEVI (Pigmented Mole)

A
  • Melanocytes cluster together to form naevi
  • Some moles are present at birth (congenital), others develop during childhood/early adulthood (acquired)
  • The MAIN thing is to differentiate from melanomas (cancers)
  • 3 main types of acquired melanocytic naevi:
  • Junctional (more pigmented, more closely associated with melanoma)
  • Intradermal
  • Compound (both)
44
Q

Junctional nevus

A

flat

brown to black

45
Q

compound nevus

A

slightly elevated

brown or light brown

46
Q

intradermal nevus

A

dome shaped, warty or sessile

light brown or flesh coloured

47
Q

MALIGNANT MELANOMA

A
  • Type of skin cancer that starts in the melanocytes
  • Related to the sun/UV
  • Used to be uniformly deadly as quickly metastises
  • Has both vertical and horizontal growth phase
  • Prognosis related to VERTICAL and linked to staging
  • Staging (how far has it spread) TNM (Tumour, Node, Metastasis) and thickness BRESLOW
  • Difficult to differentiate from nevus clinically and often microscopically
48
Q

How to check your moles – ABCDE(EFG) principle

A
  • Asymmetrical – two halves maybe different
  • Borders (irregular)
  • Colour (variegated, uneven)
  • Diameter (greater than 6 mm)
  • Evolving over time (enlarging, changing)

Nodular melanoma
• Elevated above the skin surface
• Firm to the touch
• Growing

49
Q

Acanthosis nigricans,

A

often associated with diabetes mellitus
• Thickened (acanthosis), hyperpigmented zones of skin
• Commonly flexural regions – armpits, folds of neck

50
Q

URTICARIA (Hives)

A

• Common disorder characterised by:
o localised mast cell degranulation (histamine)
o Dermal oedema and dilatation of vascular spaces
o Itchy raised oedematous plaques called WHEALS
• Caused by allergic reaction (e.g food), drugs, cold/heat exposure

51
Q

ECZEMA (aka, acute eczematous dermatitis)

A
  • A myriad of ACUTE inflammatory disorders, with allergic, drug related, sun related aetiologies
  • The common histologic feature is spongiosis
52
Q

PSORIASIS

A
  • Common chronic inflammatory dermatoses – affects about 1-2% of people in the UK
  • Frequently affects skin of elbows, knees , scalp
  • Typical lesion is well-demarcated pink to salmon-coloured plaque covered by loosely adherent scales (silver-white in colour)
  • Affects all ages – can be associated with arthritis, heart disease
53
Q

First-degree burns

A

affect only the epidermis; limited to redness and pain, very COMMON include sunburn, touching a hot iron/stove

54
Q

Second-degree burns

A

involve the superficial (papillary) dermis and sometimes the deep (reticular) dermis. Characterised by redness, pain, swelling and blistering

55
Q

Third-degree burns

A

occur when the epidermis is lost with damage to the subcutaneous tissue. Result in scars and may require grafts

56
Q

Fourth-degree burns

A

are life-threatening, and associated with major damage or loss of the hypodermis,
damage to muscle, tendon, and ligament tissue. Grafting is required if the patient survives

57
Q

Severe burns: dehydration and treatment

A
  • Damaged tissue releases ‘middle molecules’ (leukotrienes, prostaglandins, oxygen free radicals and histamine) into the circulation, leading to a systemic increase of capillary permeability
  • Burns victims lose catastrophically high amounts of liquid
  • The body attempts to compensate for this loss by shifting fluid around the body’s organs to keep each functioning
  • Kidneys, liver and brain are compromised by displacement of the loss of fluids and proteins – ORGAN HYPOPERFUSION and tissue injury – ‘BURN SHOCK’ – can be FATAL
58
Q

Parkland formula

A
  • Fluid needed in first 24 hrs = Total Body Surface Area (TBSA) burned (%) x W t (kg) x 4mL
  • Give half of fluid in first 8 hours and remainder in next 16hrs
  • So an average man (approx. 80kg) with 18% full thickness burns requires 5.76L of fluid, with 2.88L in the first 8 hours
  • The aim is to maintain fluid level to a point where urine output is 1 ml/kg/hour
59
Q

skin grafts

A
  • Autologous –from the same individual
  • Isogeneic –from a different, genetically identical, individual
  • Allogeneic – from a different individual
  • Xenogeneic – from a different species
  • Prosthetic – using artificial tissue
60
Q

Split thickness skin grafts (STSG)

A
  • Take just the epidermis and a portion of the dermis

* The parts of the dermis containing follicles and sebaceous glands remains in place

61
Q

Full thickness skin grafts (FTSG)

A

• More complicated, and may involve muscles and blood vessels

Human Anatomy (12 decks)

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