Lexture - 18 Epidermis And Dermis

Question 1

Integumentary system

Answer 1

Consists of skin
hair
nails
sweat gland
and sebaceous (oil) glands

Question 2

Epidermis

Answer 2

Outermost layer
Avascular epithelial tissue

Question 3

Dermis

Answer 3

Inner layer
Papilllary layer, reticular layer
Vascular connective tissue
Composed of :
Strong, flexible connective tissue, supplied with blood vessels, nerves and lymphatic vessels

Question 4

Hypodermis

Answer 4

Also called superficial fascia

Subcutaneous tissue beneath the skin (NOT PART OF THE INTEGUMENTARY SYSTEM)
Consists mostly of adipose tissue that anchors the skin to underlying muscle, allows skin to slide over muscle and act as a shock absorber and insulator

Question 5

Keratinocytes

Answer 5

Keratinized stratified squamous epithelium
Produce fibrous protective protein called keratin

Question 6

Melanocytes

Answer 6

Epithelial cells
Synthesize pigment melanin and transfer it to keratinocytes to protect nucleus from UV damage

Question 7

Langerhans cells

Answer 7

Intraepidermal macrophages
Activate immune system

Question 8

Tactile (merkel) cells

Answer 8

Associated with touch sensory nerve endings

Question 9

Layers of epidermis and dermis

Answer 9

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

Come Lets Get Sun Burnt

Question 10

Stratum corneum

Answer 10

Anucleated, keratinized dead cells
Accounts for 3/4 of epidermal thickness

Though cells are dead, they still function to:
Protect deeper cells from the environment
Prevent water loss
Protect from abrasion and penetration
Act as barrier against biological, chemical and physical assaults

Question 11

Stratum lucidum

Answer 11

Found only in thick , hairless skin
Ex. Covers palm of hands, soles of feet, surfaces of fingers and toes

Consists of thin, translucent band, two to three rows of clear,flat,dead keratinocytes

Lies superficial to stratum granulosum

Question 12

Stratum granulosum

Answer 12

Four to six cells thick, cells flattened so layer is thin

Cell appearance changes, cell flattens, nuclei and organelles disintegrate and keratinization begins.
Cells accumulate keratohyaline granules that help form keratin fibres in upper layers
Cells also accumulate lamellar granules, a water resistant glycolipid that slows water loss

Cells above this layer die, too far from dermal capillaries to survive

Question 13

Stratum spinosum

Answer 13

Three to five cells thick

Cells contain weblike system of intermediate prekeratin filaments attached to desmosomes, allowing them to resist tension and pulling

Keratinocytes appear spikey, so they are called prickle cells

Scattered among the keratinocytes are abundant melanosomes and langerhan cells

Question 14

Stratum basale

Answer 14

Deepest of all epidermal layers, firmly attached to dermis

Consists of a single row of stem cells that actively divide, producing two daughter cells each time

AKA stratum germinatibum because of active mitosis

10-25% of layer composed of melanocytes

Question 15

Papillary layer

Answer 15

Top layer of dermis

Thin, superficial papillary layer of Areolar connective tissue forms dermal papillae that result in fingerprints

Dermal papillae are a superficial region of dermis that’s ends finger like projections up into epidermis, contain capillary loops, nerve endings and touch receptors

Question 16

Reticular layer

Answer 16

Consists of dense fibrous connective tissue with stretchy elastic fibres and durable collagen fibers

Flexure lines, deep dermal folds at or near joints, dermis is tightly secured to deeper structures,so it cannot slide easily for joint movement

Tension lines, caused by many collagen fibres running parallel to skin surface,externally invisible but are important to surgeons becaus eincisions parallel to cleavage lines heal more readily

Extreme stretching of skin can cause dermal tears, leaving silvery white scars called striae, sometimes referred to as “stretch marks”

Question 17

Blisters

Answer 17

Fluid filled pockets where the epidermal and dermal layers have been separated

Caused by acute, short term traumas:
Friction or rubbing
Burns or frostbite
Harsh chemicals
Pinching or crushing
Acute inflammation from some disease

Question 18

Melanin

Answer 18

Group of skin and hair pigments
Brown or black (eumelanin)
Pinkish red (pheomelanin)

All humans have same number of keratinocytes, so skin colour differences are due to the amount and form of melanin

Sunlight causes keratinocytes to secrete a signal, stimulating melanin production, which is packaged into melanosomes and sent to keratinocytes to protect DNA from damaging UV rays

Question 19

Carotene and hemoglobin

Answer 19

yellow-orange pigment found in certain foods. tends to accumulate in the stratum corneum and subcutaneous layer, most obviously in the palms and soles, intensifies as more carotene-containing foods are eaten. can be converted to vitamin A for vision and epidermal health.

The pinkish hue seen in fair skin is due to hemoglobin in the blood, seen through the transparency of the skin.

Question 20

Excessive sun exposure

Answer 20

Excessive sun exposure can cause elastic fibers to clump, making the skin leathery. can also depress the immune system and cause alterations in DNA that may lead to skin cancer.

UV light destroys folic acid, which is necessary for DNA synthesis.

Some drugs (e.g., antibiotics, antihistamines) and perfumes cause photosensitivity (an increased reaction to sunlight), leading to skin rashes

Question 21

Changes in skin colour

Answer 21

Cyanosis (blue skin colour)
• Low oxygenation of hemoglobin

Jaundice (yellowish skin)
• Liver disorders can inhibit the processing of yellow bilirubin from damaged red blood cells.

Erythema (redness)
• Fever, hypertension, inflammation, allergy

Pallor (pale colour)
• Anemia, low blood pressure, fear, anger

Bronzing
• Inadequate steroid hormones causes over- expression of melanin (example: Addison’s disease)

Bruises (black-and-blue marks)
• Clotted blood beneath skin