Chapter 6 - Integumentary System

Question 1

Layers of the Skin

Answer 1

Cutaneous Layers of skin:
- Epidermis: stratified squamous tissue
- Basement membrane achors epidermis to dermis
- Dermis: made up of connective tissue including collagen, elastic fibers, smooth muscle tissue, nervous tissue and blood and lymphatic vessels

Subcutaneous Layers: not part of skin
- Hypodermis: composed of areolar and adipose connective tissue which bind skin to underlying organs
No distinct boundary

Question 2

Layer of Skin: Epidermis

Answer 2

• Lacks blood vessels
  ○ Cells in stratum basale are nourished by dermal blood vessels
  
  • The further cells are pushed away from the basal layer, the poorer their nutrient supply and in time they harden and die; keratinization
    ○ Cytoplasms fill with strands of tough fibrous waterproof keratin proteins
  • In healthy skin, production of epidermal cells occurs as frequently as loss of dead cells in stratum corneum occurs
  • Rate of cell division will occur faster where skin is rubbed or pressed, as this causes the growth of thickened areas(calluses)

Question 3

1st Layer of the Epidermis

Answer 3

Stratum Corneum: most superficial layer that has layers of keratinized, dead, flaky and scaly epithelial cells
○ Involved in resisting water loss, absorption, abrasion

Question 4

2nd Layer of the Epidermis

Answer 4

• Stratum lucidum: only found between stratum corneum and stratum granulosum on soles and palms of thick skin where the cells appear clear
  ○ 2nd layer in thick skin

Question 5

3rd Layer of the Epidermis

Answer 5

• Stratum Granulosum: 3-5 layers of flattened granular cells which contain fibers of keratin and shriveled nuclei which is involved in waterproofing and cuts off blood supply
  ○ 3rd layer in thick skin, 2nd layer in normal skin

Question 6

4th Layer of the Epidermis

Answer 6

• Stratum Spinosum: found beneath the granulosum where many layers of cells, which become flatter as they get more superficial, with large centrally located nuclei develop fibers of keratin
  ○ 4th layer in thick skin, 3rd layer in normal skin

Question 7

5th Layer of the Epidermis

Answer 7

• Stratum Basale: the deepest layer involving a single row of cuboidal or columnar cells which includes melanocytes and frequently divides to send cells into superficial layers.

Question 8

Cells in the Epidermis

Answer 8

Dendritic/Langerhans cells: phagocytes within stratum spinosum which protect the skin and deeper tissue from pathogen invasion
- Engulf invading microbes within skin, process and display parts of the microbe on their membrane and then migrate to lymphatic tissue to alert other immune cells

Tactile/Merkel cells: oval shaped cells scattered in the stratum basale which correspond to a nerve ending and release chemicals when lightly touched, stimulating the sensory nerve
- Tactile disc is the tactile cell with the sensory nerve ending

Melanocytes: epidermal cells in the stratum basale which produce and store melanin which absorbs UV light in order to protect DNA from mutations in skin cells
- As a result of absorbing UV light it is resposnible for the color of our skin

Question 9

Types of Melanin to make up skin color

Answer 9

○ Eumelanin: brownish black in the epidermis
- Pheomelanin is the reddish-yellow in certain locations such as lips

Question 10

Types of Skin Cancers

Answer 10

• Basal cell carcinoma: least malignant where the stratum basale cells proliferate and push down into the dermis
  ○ 99% cure rate with surgical removal
  • Squamous cell carcinoma: stratum spinosum cells that divide as they keratinize producing a nodular tumor
    ○ Sun induced and cure rate is good with surgical removal
  • Malignant Melanoma: Melanomas arise from melanocytes, usually arising from a preexisting mole which metastasizes to lymph nodes
    ○ Not always sun induced but often spontaneously

Question 11

Dermal Papillae

Answer 11

• Dermal and epidermal boundary is uneven and causing dermal papillae extend into the dermal spaces between epidermal ridges
  
  • They increase surface area where epidermal cells receive oxygen and nutrients from dermal capillaries
  • Most abundant in the hands and feet
  • Ridges form a patterned impression; fingerprint

Question 12

Layers of Dermis

Answer 12

• Papillary layer which is composed of areolar connective tissue
• Reticular layer: composed of dense irregular connective tissue which has lots of tough collagen fibers and elastic fibers, giving skin its toughness

Question 13

Cells in the Dermis

Answer 13

• Sensory receptors in dermis include:
  ○ Lamellated corpuscles: reside in the deeper dermis and respond to heavy pressure
  ○ Tactile corpuscles: reside in the upper dermis and respond to light touch and texture
• Sweat Glands
• Hair Follicles

Question 14

Nails

Answer 14

protective coverings on the ends of fingers and toes
- All of the nail is dead cells except for the lunula, however pain is felt due to it being attached to the bed which is alive

Question 15

Structure of Nails

Answer 15

• Nail bed is produced from deeper layers of epidermal skin
  
  • Nail plate: visible portion consisting of keratinized cells which overly the nail bed
  • Blood vessels under the nail give it a pinkish appearance
  • Nail matrix: active growth region not visible and at the proximal end of nail bed
  • Lunula is the whitish half-moon region due to the thick nail matrix concealing dermal blood vessels
  • Cuticle: a portion of stratum corneum extending over the proximal end of the nail
    
    • Free edge: the nail plate extending beyond the end of the nail bed

Question 16

Hair Follicles

Answer 16

a tube like depression where epidermal stem cells develop into hair

• Hair cycles through phases of active growth and inactive periods
  
  • 90% of hair at any time is growing

Question 17

Structure of Hair Follicle

Answer 17

• Hair bulb sits in the base of the follicle
• Hair matrix within the hair bulb contains epithelial cells which allow for division and growth
• Hair papilla: contain blood vessels to nourish the hair and anchor the hair bulb
• hair root extends from the skin surface to the subcutaneous layer
  
  • Hair shaft is composed of keratinized epithelial cells which extend away from skin surface

Question 18

Alopecia

Answer 18

Baldness occurs when hair sheds and is not replaced which is associated with lower levels of testosterone or estrogen:

Question 19

Sebaceous Glands

Answer 19

composed of groups of specialized epithelial cells which secrete sebum that is secreted into hair follicles through ducts and helps keep the hairs and skin soft, pliable and waterproof
- Its a holocrine gland meaning it secretes whole cells with fluid

Question 20

Sweat/Sudoriferous Glands

Answer 20

consist of a tiny tube that originates as a ball shaped coil which is lined with sweat secreting epithelial cells which secrete through pores to the surface
- Sweat is water with small amounts of salts, urea and uric acid

Question 21

2 Types of Sweat Glands

Answer 21

• Most are merocrine sweat glands which respond to elevated body temperatures, and do not go into hair follicles but release through pores in skin
  
  • Apocrine sweat glands do release into hair follicles and are found in axillary and groin areas

Question 22

Ceruminous Glands

Answer 22

glands found in the ear canals which secrete cerumen/ear wax which mixes with sebum to make a sticky substance, preventing entry of microbes and foreign substances

Question 23

Mammary Glands

Answer 23

develops during pregnancy and lactation which secretes milk through a duct to the nipple

Question 24

Functions of Skin

Answer 24

• Protection: protects against harmful substances, UV radiation, microorganisms and water loss
  
  • Sensation: contains sensory receptors for touch, pressure, temperature change and pain
  • Vitamin D synthesis: starts in skin and helps with calcium absorption
  • Body temp regulation: helps cool body by sweating and changing blood flow

Question 25

Function of Skin: Protection

Answer 25

• Keratinization and layering of skin provides a protective barrier against harmful diseases
  
  • Contains dendritic cells which initiate the immune response
  • Melanocytes secrete melanin which protects epidermal cells from harmful effects of UV
  • Sweat being slightly acidic inhibits growth of microorganisms
  • Sebum helps retard water loss

Question 26

Function of Skin: Sensation

Answer 26

• Skin houses tactile discs which detect touch
  
  • Receptors in hair follicles detect insects crawling, wind blowing or hair pulling
  • Othre sensors detect pressure, change in temp and pain

Question 27

Function of Skin: Vitamin D Production

Answer 27

3 step process which begins in the skin:
- Some skin cells produce dehydrocholesterol(precursor) which when exposed to sunlight changes to an inactive form of vitamin D(cholecalciferol)
- This is then taken to the liver for the 2nd and 3rd steps of making it active

- Vitamin D is necessary for the absorption of calcium from foods

Question 28

Ways heat is released by the skin

Answer 28

○ Heat is then primary released through radiation where infrared heat rays escape to the cooler surroundings
○ Can also be released through conduction when heat moves from the body to a cooler object or through convection where heat is lost to the cooler air which is taken away and replaced with cooler air again

Thermo receptors take signal to hypothalamus which results in vasodilation of dermal blood vessels and activation of sweat glands

Question 29

Ways heat is conserved by the skin

Answer 29

• Hypothalamus triggers smooth muscle cells in dermal blood vessels to vasoconstrict and decrease blood flow to the surface, reducing heat loss by radiation, conduction and convection
  
  • Merocrine sweat glands remain inactive
    Shivering: Muscle cells may be stimulated to contract forcefully increase cellular respiration

Question 30

Fever

Answer 30

set point in body is elevated by the immune system to fight infection
- Phagocytes release pyrogens in response to presence of bacteria viruses which triggers the hypothalamus to raise body temperature and destroy the pathogens

Question 31

Inflammation

Answer 31

response to injuries where blood vessels in affected tissues dilate and become permeable, allowing nutrients and oxygen to leak into damaged tissue and aid healing

Question 32

Epidermal Wounds

Answer 32

• If a break in skin is shallow, epithelial cells are stimulated to divide more rapidly along the border and fill the gap

Question 33

Dermal Wounds

Answer 33

• Blood vessels will be broken and blood begins to form a clot containing fibrin while tissue fluids seep into the area and begin to dry to form with the fibrin a scab
  
  • Under the scab, epithelial cells proliferate and bridge the wound while fibroblasts migrate into the region and secrete collagen fibers to stitch the edges together
  • Blood vessels extend beneath the scab allowing phagocytotic cells to remove debris
  • The scab will then fall off

Question 34

Superficial Partial Thickness(1st degree) burn

Answer 34

burn injuring only the epidermis
- Recovery is a few days to two weeks
- Due to minor sunburns

Question 35

Deep partial thickness(2nd degree):

Answer 35

burn destroying some epidermis as well as some underlying dermis
- Fluid escapes from damaged dermal capillaries and accumulates under the outer layer of epidermal cells, forming blisters
- Due to exposure to hot objects, liquids, flame or burning clothes
- Full recovery will occur in time unless an infection occurs

Question 36

Full Thickness(3rd degree)

Answer 36

burn destroying the epidermis, dermis and accessory structures of the skin
- Due to prolonged exposure to hot objects, flames or corrosive chemicals
- Treatment could involve an autograft which involves removing a thin layer of healthy skin from another area and transplanting it into the injured area
- Allograft is needed if extensive damage is done where cadaveric skin is taken from a skin bank and temporarily covers the wound until an autograft can be done

Question 37

Rule of 9’s for Burns

Answer 37

• Extent of affected body surface in burns is estimated using the rule of nines
  
  • The skin surface region is divided and each region accounts for either 9% or multiples of the total surface area
  • Used to estimate replacing body fluid, electrolytes and for covering burned area

Question 38

Ageing in skin

Answer 38

• Epidermis thins as the decades pass
  
  • As cell cycle slows, they grow larger and more irregular in shape
  • Dermis becomes reduced in volume and in function as synthesis of collagen and elastin slows
    ○ Results in wrinkling and sagging of skin
  • Wound healing slows due to fewer fibroblasts

Question 39

Ageing in skin accessory structures

Answer 39

• Slowed melanin production whitens hair as the hair shafts become more transparent
  
  • Hair growth slows, thins and number of follicles decrease
  • Sensitivity to pain and pressure diminishes as sensory receptors reduce in quantity
  • Due to older people not getting outdoors as much, less vitamin D is formed resulting in weaker bones
  • Sweat glands fall reducing the ability to cool themselves down
  • Hair follicles shrink resulting in a decreased ability to shiver