Skin

Question 1

Which are the three major regions of the Skin (Integument).

Answer 1

Skin (Integument)

Consists of three major regions ƒ

• Epidermis – outermost superficial region ƒ
• Dermis – middle region
• Hypodermis (subcutaneous fat) – deepest region

Question 2

Which are the functions of the Integumentary system?

Answer 2

Functions of the Integumentary System

1. ƒ Protection – chemical, physical, and mechanical barrier ƒ
2. Body temperature regulation is accomplished by: ƒ
   
   • Dilation (cooling) and constriction (warming) of dermal vessels ƒ
   • Increasing sweat gland secretions to cool the body ƒ
3. Cutaneous sensation – exoreceptors sense touch and pain
4. Metabolic functions – synthesis of vitamin D in dermal blood vessels ƒ
5. Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume ƒ
6. Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat

Question 3

Describe Epidermis.

Answer 3

Epidermis

1. Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers .
2. Cell types include keratinocytes, melanocytes, Merkel cells, and Langerhans’ cells.
3. Outer portion of the skin is exposed to the external environment and functions in protection

Question 4

Which are the cells of the Epidermis?

Answer 4

Cells of the Epidermis

1. Keratinocytes – produce the fibrous protein keratin ƒ
2. Melanocytes – produce the brown pigment melanin ƒ
3. Langerhans’ cells – epidermal macrophages that help activate the immune system
4. Merkel cells – function as touch receptors in association with sensory nerve endings

Question 5

Which are the layers of Epidermis?

Answer 5

Layers of Epidermis

1. Stratum Basale (Basal Layer)
2. Stratum Spinosum (Prickly Layer)
3. Stratum Granulosum (Granular Layer)
4. Stratum Lucidum (Clear Layer)
5. Stratum Corneum (Horny Layer)

Question 6

Explain Stratum Basale.

Answer 6

Layers of the Epidermis: Stratum Basale (Basal Layer)

1. Deepest epidermal layer firmly attached to the dermis ƒ
2. Consists of a single row of the youngest keratinocytes ƒ
3. Cells undergo rapid division, hence its alternate name, stratum germinativum

Question 7

Explain Stratum Spinosum.

Answer 7

Layers of the Epidermis: Stratum Spinosum (Prickly Layer)

1. Cells contain a weblike system of intermediate filaments attached to desmosomes ƒ
2. Melanin granules and Langerhans’ cells are abundant in this layer

Question 8

Explain Stratum Granulosum.

Answer 8

Layers of the Epidermis: Stratum Granulosum (Granular Layer)

1. ƒ Thin; three to five cell layers in which drastic changes in keratinocyte appearance occurs ƒ
2. Keratohyaline and lamellated granules accumulate in the cells of this layer

Question 9

Explain Stratum Lucidum.

Answer 9

Layers of the Epidermis: Stratum Lucidum (Clear Layer)

1. Thin, transparent band superficial to the stratum granulosum ƒ
2. Consists of a few rows of flat, dead keratinocytes ƒ
3. Present only in thick skin

Question 10

Explain Stratum Corneum.

Answer 10

Layers of the Epidermis: Stratum Corneum (Horny Layer)

1. Outermost layer of keratinized cells ƒ
2. Accounts for three quarters of the epidermal thickness ƒ
3. Functions include: ƒ
   
   1. Waterproofing ƒ
   2. Protection from abrasion and penetration ƒ
   3. Rendering the body relatively insensitive to biological, chemical, and physical assaults

Question 11

What are the differences between thick and thin skin?

Answer 11

See picture.

Question 12

Explain the Dermis.

Answer 12

Dermis ƒ

1. Second major skin region containing strong, flexible connective tissue ƒ
2. Cell types include fibroblasts, macrophages, and occasionally mast cells and white blood cells ƒ
3. Composed of two layers – papillary and reticular

Question 13

Explain Papillary Layer.

Answer 13

Layers of the Dermis: Papillary Layer ƒ

1. Areolar connective tissue with collagen and elastic fibers ƒ
2. Its superior surface contains peglike projections called dermal papillae ƒ
3. Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings

Question 14

Explain Reticular Layer.

Answer 14

Layers of the Dermis: Reticular Layer ƒ

1. Accounts for approximately 80% of the thickness of the skin ƒ
2. Collagen fibers in this layer add strength and resiliency to the skin ƒ
3. Elastin fibers provide stretch-recoil properties

Question 15

Explain Hypodermis

Answer 15

Hypodermis ƒ

1. Subcutaneous layer deep to the skin ƒ
2. Composed of adipose and areolar connective tissue

Question 16

Explain Skin Color.

Answer 16

Skin Color ƒ

Three pigments contribute to skin color:

1. Melanin – yellow to reddish-brown to black pigment, responsible for dark skin colors ƒ
   
   • Freckles and pigmented moles – result from local accumulations of melanin ƒ
2. Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet ƒ
3. Hemoglobin – reddish pigment responsible for the pinkish hue of the skin

Question 17

Explain different types of Sweat glands.

Answer 17

Sweat Glands ƒ

Different types prevent overheating of the body; secrete cerumen and milk ƒ

1. Eccrine sweat glands – found in palms, soles of the feet, and forehead ƒ
2. Apocrine sweat glands – found in axillary and anogenital areas ƒ
3. Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen ƒ
4. Mammary glands – specialized sweat glands that secrete milk

Question 18

Explain Sebaceous Glands.

Answer 18

Sebaceous Glands ƒ

1. Simple alveolar glands found all over the body ƒ
2. Soften skin when stimulated by hormones ƒ
3. Secrete an oily secretion called sebum

Question 19

Explain the structure of hair.

Answer 19

Hair ƒ

1. Filamentous strands of dead keratinized cells produced by hair follicles ƒ
2. Contains hard keratin which is tougher and more durable than soft keratin of the skin ƒ
3. Made up of the shaft projecting from the skin, and the root embedded in the skin ƒ
4. Consists of a core called the medulla, a cortex, and an outermost cuticle ƒ
5. Pigmented by melanocytes at the base of the hair

Question 20

Explain the function and distribution of hair.

Answer 20

Hair Function and Distribution ƒ

Functions of hair include: ƒ

1. Helping to maintain warmth ƒ
2. Alerting the body to presence of insects on the skin ƒ
3. Guarding the scalp against physical trauma, heat loss, and sunlight

Hair is distributed over the entire skin surface except: ƒ

1. Palms, soles, and lips ƒ
2. Nipples and portions of the external genitalia

Question 21

Explain the structure and functions of hair follicles.

Answer 21

Hair Follicle ƒ

1. Root sheath extending from the epidermal surface into the dermis ƒ
2. Deep end is expanded forming a hair bulb ƒ
3. A knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb ƒ
4. Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors

Question 22

Explain the structure of a nail.

Answer 22

Structure of a Nail ƒ

Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes

Question 23

Name three major types of skin cancer.

Answer 23

Skin Cancer ƒ

The three major types of skin cancer are: ƒ

1. Basal cell carcinoma ƒ
2. Squamous cell carcinoma ƒ
3. Melanoma

Question 24

Explain first degree burns.

Answer 24

Burns ƒ

First-degree – only the epidermis is damaged ƒ

Symptoms include localized redness, swelling, and pain

Question 25

Explain second-degree burns.

Answer 25

Burns ƒ

Second-degree – epidermis and upper regions of dermis are damaged ƒ

Symptoms mimic first degree burns, but blisters also appear

Question 26

Explain Third-degree burns.

Answer 26

Burns ƒ

Third-degree – entire thickness of the skin is damaged ƒ

Burned area appears gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed)

Question 27

Explain the Rule of Nines.

Answer 27

Rule of Nines

The rule of nines assesses the percentage of burn and is used to help guide treatment decisions including fluid resuscitation and becomes part of the guidelines to determine transfer to a burn unit.