Cutaneous Membrane

Question 1

What is the integumentary system composed of?

Answer 1

Cutaneous membrane (epidermis and dermis) and accessory structures (, hair follicles, nails, exocrine glands)

Question 2

What is the cutaneous membrane composed of?

Answer 2

Epidermis and dermis make up the two layers of the skin

Question 3

What is the subcutaneous membrane?

Answer 3

Hypodermis; composed of loose connective tissue (not part of the integument but tissue fibres are interwoven with those of the dermis)

Question 4

What is the integument?

Answer 4

Epidermis + Dermis + Accessory structures

Question 5

What are the functions of the skin and hypodermis? (8)

Answer 5

1) Protection: from impact, abrasion, fluid loss, chemicals
2) Excretion: of salts, water, organic wastes
3) Regulation of body temperature
4) Synthesis of vitamin D3: a steroid that is converted into calcitriol hormone required for Ca2+ absorption from the intestine
5) Storage of lipids: in adipocytes
6) Sensation: innervated tactile receptors sensitive to different levels of touch and vibration
7) Production of melanin: protects cells from UV
8) Production of keratin: protects from dehydration

Question 6

What is the composition of the epidermis?

Answer 6

Stratified squamous epithelium which are avascular; superficial surface cells are inert/dead

Question 7

What are the characteristics of the epidermis?

(main cell type, nature of cell junctions)

Answer 7

Main cell type: keratinocytes
Nature of cell junctions: hemidesmosomes to basal lamina

Question 8

What is the origin and fate of keratinocytes in the epidermis?

Answer 8

Newly formed cells at the bottom are pushed further towards the surface of the cell and are eventually shed (die)

Question 9

What is the dermal papillae?

Answer 9

Dermal papillae are upward extensions of the dermis layer of the skin. The strength of attachment is proportional to the surface area

• named for its fingerlike projections called papillae
• little humps

They have two main functions: to help adhesion between the dermal and epidermal layers, and to provide a large surface area to nourish the epidermal layer

Question 10

What are the layers of the epidermis?

Answer 10

2 types of skin; thin or thick

Thin = 4 layers of keratinocytes
Thick = 5 layers of keratinocytes

Question 11

What are the (5) layers of skin in thick skin?

Answer 11

Stratum Corneum (thickest; 20-30 layers)
Stratum Lucidum (palms and soles only)
Stratum Granulosum
Stratum Spinosum
Stratum Germinativum/Basale

Question 12

What are the (4) layers of the skin in thin skin?

Answer 12

Stratum Corneum (thickest; outermost; 25-30 layers dead skin)
Stratum Granulosum
Stratum Spinosum
Stratum Germinativum/Basale

Question 13

What layer of skin is present in only thick skin?

Answer 13

Stratum Lucidum

Question 14

What contributes to the colour of skin?

Answer 14

Epidermis contains melanin which gives skin its colour and allows skin to tan

Carotene and oxygen-rich hemoglobin also contribute to the colour of skin

Question 15

What stiffens epidermal tissue to form fingernails?

Answer 15

Protein keratin

Question 16

Order the layers of the epidermis; deep to superficial

Answer 16

1) Stratum germinativum/basale- Deepest
2) Stratum spinosum
3) Stratum granulosum
4) Stratum lucidum
5) Stratum corneum - Surface

Question 17

What is the stratum germinativum/basale

Answer 17

• anchored to basal lamina by hemidesmosomes
• forms epidermal ridges which interlock with dermal papillae
• simple cuboidal/columnar epithelium (keratinocytes)
• provides strong attachment

Question 18

Why do you get calluses and what are they?

Answer 18

Pressure, wear and tear stimulates more rapid mitosis, which leads to thickening of the epidermis as a protective mechanism

Question 19

Why do you get blisters and what are they?

Answer 19

Friction or damage to the epidermis from extreme temperatures or chemicals cause layers of the epidermis to separate and the gaps fill with fluid from underlying tissue (clear, blood, or pus if infected)

The fluid stimulates healing and regrowth

Question 20

What is the purpose of ridges in the skin?

Answer 20

Ensures good grip of fingers and toes; creates fingerprint ridge pattern uniqueness

• genetics + in utero development

Question 21

Would identical twins have the same finger prints?

Answer 21

NO :3

• different level of hormones, growth factors

Question 22

Why do you get prune-y fingers in the bath?

Answer 22

Nervous system triggers blood vessel constriction

Question 23

What cell types are present in the stratum germinativum?

Answer 23

a) basal cells = germinative cells (stem cells)
b) melanocytes = pigment producing cells
c) merkel cells = sensitive to touch, activate nerve endings by releasing chemicals

Provides protection for DNA from the sun

Question 24

What is the stratum spinosum?

Answer 24

spiny layer; 8-10 layers of keratinocytes joined by desmosomes

includes langerhans (dendritic) cells (phagocytes)

defends against microorganisms and superficial skin cancer

Question 25

What is the stratum granulosum?

Answer 25

Grainy layer; 3-5 layers of keratinocytes which accumulate in granules, promoted dehydration, and cross links between keratin fibres

as cells move upwards through the stratum granulosum, they become thinner, flatter, and less permeable, creating a tightly interlocked layer of cells. Cells begin to die at this layer

Question 26

What are keratinocytes

Answer 26

cells that produce large amounts of protein keratin

Question 26

What is insensible water loss?

Answer 26

Water loss directly through the skin (not the sweat glands); evaporation through skin and respiration

500mL/day

Question 26

What are melanosomes?

Answer 26

Melanin packaged into vesicles

melanosomes passed to keratinocytes

Question 27

What are cells superficial to the stratum corneum?

Answer 27

Dead

Question 27

What is melanin?

Answer 27

A yellow/brown pigment made from tyrosine amino acid; a biochemical, not amino acid

produced by melanocytes in the stratum germinativum

Question 27

What is the stratum corneum?

Answer 27

Horny layer; 15-30 layers of keratinized, dead cells tightly interconnected by desmosomes

water resistant; insensible water loss

Question 27

What is the stratum lucidum?

Answer 27

Clear layer; present only in thick skin

cells are densely packed with keratin and devoid of organelles

Question 27

What are the pigments of epithelium?

Answer 27

Carotene and melanin

Question 28

What is sensible water loss?

Answer 28

Sweating through the sweat glands

Question 28

What is carotene?

Answer 28

An orange/yellow pigment (also found in orange vegetables; can be converted to vitamin A)

humans cannot produce carotene

fat soluble; located in fat cells

Question 29

What is vitiligo?

Answer 29

Vitiligo results from loss of melanocytes, causing white patches on the skin

causes are unknown but may result from autoimmune diseases, genetic factors, or other factors

Question 30

How does the number of melanocytes differ in people of different skin colours?

Answer 30

Everyone has approximately the same amount of melanocytes; melanosomes is what impacts skin colour

Question 31

Melanosomes in people with light skin

Answer 31

Breakdown of melanosomes occurs in the strata germinativum and spinosum by fusion with lysosomes

Question 32

Melanosomes in people with darker skin

Answer 32

Breakdown of melanosomes in the stratum granulosum

melanosomes are more numerous and larger in size

Question 33

What effect does UV have on skin?

Answer 33

Damage to DNA in stratum germinativum

Question 34

What influences skin colour?

Answer 34

Number and size of melanosomes, dermal circulation

Question 35

What is dermal circulation?

Answer 35

Influences skin colour;

a) oxygenates hemoglobin - bright red

-noticeable in light skinned individuals, especially when exercising or flushed (capillaries are dilated)

b) if cold temp. - skin capillaries constrict, making you look paler

• capillary constriction also occurs if blood flow is damaged/restricted

c) low oxygen - deoxygenated hemoglobin - appears dark red and through pale skin

-blue is called cyanosis

Question 36

What is cholecalciferol?

Answer 36

Vitamin D3; required for normal absorption of Ca++ from digestive tract

Vitamin D3 is produced by epithelial cells in the stratum spinosum and stratum germinativum in response to sunlight

the liver converts the vitamin into a product that the kidneys turn into calcitriol

Question 37

What causes ricketts?

Answer 37

Caused by a deficiency in Vitamin D3, resulting in the bending of abnormally weak and flexible bones under the weight of the body

Question 38

What are vitamins?

Answer 38

Essential organic nutrient

Question 39

Sources of vitamin D3?

Answer 39

** refer to diagram pg. 30

a) Sunlight: In response to sunlight, epithelial cells in the epidermis produce cholecalciferol, which then is converted in the liver to an intermediary product, which is then converted to calcitriol in the kidney.

Calcitriol stimulates calcium and phosphate ion absorption in the digestive tract

b) Dietary Sources: the body intakes VD3 consumption of dietary sources of VD3, which is then converted in the liver to an intermediary product, and then converted to calcitriol in the kidney.

Calcitriol stimulates calcium and phosphate ion absorption in the digestive tract (intestine)

Question 40

What is the composition of the dermis?

Answer 40

2 layers; papillary layer and reticular layer of the dermis

Question 41

What is the papillary layer of the dermis?

Answer 41

Areolar tissue

-thrown into folds on the surface = dermal papillae
-contains capillaries, lymphatics, and sensory neurons that supply the surface of the skin

Question 42

What is the reticular layer of the dermis?

Answer 42

Dense irregular connective tissue; interwoven meshwork of both collagen and elastin fibres. Contains reticular fibres

also contains:
-hair follicles
-sweat glands
-lymphatic vessels
-nerve fibres

Question 43

Dermal strength and elasticity: collagen, elastic fibres, water content of skin?

Answer 43

Collagen - very strong, resists stretching
Elastic fibres - stretchy
Water content of skin = skin turgor = stretchy

Question 44

What are the lines of cleavage?

Answer 44

Collagen and elastin fibres in the dermis that are arranged in parallel bundles

-strategically line up
-bundles oriented to resist forces normally applied to skin
-establishes lines of cleavage (a line of cleavage will usually remain close and heal with little scratching; whereas severed elastic fibres recoil creating greater scarring)

Question 45

Explain the healing of incisions made along vs perpendicular to tension lines

Answer 45

Incisions made along tension lines (following tension lines) heal faster and with less scarring

Incisions made perpendicular (going against tension lines) heal more slowly and tend to scar

Question 46

Describe dermal blood supply

Answer 46

Dermis is well supplied with blood vessels; has a network of arteries and veins between the dermis and epidermis known as the cutaneous plexuses

these feed into subpapillary plexuses that supply capillaries extending into papillae = source of O2 and nutrients for epidermis

Question 47

Why are the elderly more susceptible to bruising?

Answer 47

They have more fragile capillaries, and bruises are essentially the result of capillaries bursting beneath the skin

Question 48

Describe innervation to the skin

Answer 48

Nerve cells regulate: blood flow, adjust gland secretion rates, and monitor sensory receptors

Sensory receptors respond to: light touch, deep pressure, vibration, chemicals, temperature, and pain/damage