Chapter 5: The Integumentary System

Q1: What are the functions of the integumentary system?

1. Protection: The body’s primary physical barrier

2. Temperature Regulation: Homeostasis; -Sweat, Blood Flow, Hair (“we try”)

   1. Blood Flow: Helps to regulate our body in our skin 

   2. Perspiration: Attempts to cool our body like sweating 

3. Sensation: Sensory receptors like touch, temperature, pain 

4. Vitamin D Production: Some vitamin D precursors (early molecules) are made in the epidermis 

   1. Primarily helps with calcium uptake from food 

5. Excretion of wastes: gets rid of H₂O(water), wastes, salts, and nitrogen wastes 

Q2: What are the layers of human skin, and how are they described?

1. Epidermis: 40 to 45 layers of stratified squamous epithelium

2. Dermis: dense irregular connective tissue with accessory structures, also has blood vessels in it 

3. Hypodermis: Is not part of the skin

Q3: What are the characteristics of the epidermis, and what are its cell types and layers?

• Characteristics of the epidermis: The epidermis is the outermost skin layer, mainly composed of keratinocytes that produce keratin, a protein that provides strength and protects against mechanical stress. 

• Layers (from deepest to outermost):

  • Stratum basale: 1 layer of cuboidal, the youngest keratinocytes, has lots of mitosis, a few melanocytes, cells connected by desmosomes, where basement membrane is, and where vitamin D precursors are made  

  • Stratum spinosum: 8 to 10 layers of keratinocytes (thickest), has some mitosis, has some keratin production

  • Stratum granulosum: 2 to 5 layers of keratinocytes, keratin production, and keratohyalin production, Lipid production that dehydrates or kills the cells

  • Stratum lucidum (only in thick skin): 4 to 6 layers of dead, flat, clear keratinocytes, are not present everywhere in the body 

  • Stratum corneum: highly variable, has 15 to 30 layers of keratinocytes, really just bags of keratin

• Cell Types:

  • Keratinocytes: Around 95% of cells, make keratin (water-resistant protein), a fibrous protein that is water resistant 

  • Melanocytes: Are sound 5-10% of epidermal cells (makes melanins)

  • Intraepidermal macrophages: Cells wander around looking for debris, pathogens (less than 1%)

Q4: What are the functions of the different epidermal cell types?

• Keratinocytes: Around 95% of cells, make keratin (water-resistant protein), a fibrous protein that is water resistant 

• Melanocytes: Are sound 5-10% of epidermal cells (makes melanins)

• Intraepidermal macrophages: Cells wander around looking for debris, pathogens (less than 1%)

Q5: How does human skin produce melanin, and what are the sources of carotenoids and hemoglobin?

• Melanin: Primarily pigment responsible for skin color 

• Carotenes: A yellow-orange pigment obtained from diet vegetables like carrots. 

• Hemoglobin: The iron-containing protein found within our red blood cells that binds oxygen and transports it through the body

Q6: How does the epidermis grow, and what are the differences between thick and thin skin?

• Growth: The epidermis, the outermost layer of the skin, grows through a continuous cycle of cell production and shedding

• Thick Skin: Skin that has all 5 stratum (has stratum lucidum), where we leave prints (palms, fingers, soles of feet, toes), No hairs, does have sweat glands 

• Thin Skin: Skin that does NOT have all 5 stratum (Has NO stratum lucidum)

Q7: What are the structure and function of the dermis layers, and how are the dermis and epidermis held together?

• Papillary Layer: Loose connective tissue with dermal papillae that supply nutrients to the epidermis and contain sensory receptors for light touch.

• Reticular Layer: Dense irregular connective tissue providing strength and elasticity, containing hair follicles, glands, and blood vessels.

• Connection: The dermis and epidermis are held together by collagen fibers that extend from the dermis into the basement membrane of the epidermis.

Q8: What are cleavage lines/tension lines, and why are they important in surgery?

• Definition: Cleavage lines also known as tension lines are natural patterns of collagen fibers bundled in the reticular layer of the dermis.

• Importance: Surgical incisions parallel to these lines heal faster and with less scarring, while those made perpendicular are more likely to gape and scar.

Q9: What are the types of skin cancer and their severities?

1. Basal cell carcinoma: It is the least severe, has a 90% cure rate, doesn’t often spread, and starts in the stratum basal; it can be cut out.

2. Squamous cell carcinoma: Stats in the stratum spinosum may metastasize or spread; it can be cut out. 

3. Malignant Melanoma: The most severe, is a cancerous tumor of melanocytes, looks for violations called the A, B, C, D, E rule 

   1. A- Asymmetry shape 

   2. B- Border irregularity 

   3. C- Color change

   4. D- Diameter change 

   5. E- Evolving nature 

Q10: What are the structures of hair follicles and nails, and how do they grow?

• Hair Follicle Structures:

  • Hair Shaft: Visible part of the hair above the skin’s surface, composed of dead, keratinized cells.

  • Hair Root: The part embedded in the dermis, containing living cells undergoing keratinization.

  • Hair Bulb: Enlarged base where hair growth occurs, containing the matrix with actively dividing cells.

  • Papilla: Connective tissue supplying nutrients via blood vessels.

• Hair Growth: Cells in the matrix divide, pushing older cells upward, which keratinize and form the hair shaft.

• Hair Color: Is determined by melanin produced by melanocytes in the bulb

• Nails Structures:

  • Nail Plate: The hard part of the nail, divided into the visible nail body and the hidden nail root 

  • Nail Bed: The epidermal layer beneath the nail plate.

  • Nail Matrix: Located in the root, where cells actively divide

  • Lunula: The half-moon-shaped area at the base of the nail, where cells accumulate keratin.

• Nail Growth: New cells form in the nail matrix, pushing older cells forward, where they harden and from the visible nail plate

Q11: What are the glands of the integumentary system and their functions?

1. Sebaceous glands: Makes sebum (hair oil, naturally produced), produces the hair; sebaceous glands are holocrine

2. Sweat glands: produce sweat 

   • Merocrine: Most of the body, only produces sweat

   • Apocrine: Are larger with larger ducts often attached to the hair follicle they are found in the armpits, genital, and areolas, they make sweat and some organic molecules (not cell fragments)

3. Ceruminous glands: Makes earwax

4. Mammary glands: Makes milk 

Q12: What are the types of hair found on humans?

1. Lanugo: Thin and non-pigmented hair; Location covers nearly the entire body of the fetus; Life Cycle typically falls out around birth.

2. Vellus: Thin and non-pigmented hair; Location covers most of the body; Lifecycle is present from birth and is replaced by terminal hair in certain areas after puberty.

3. Terminal: Thicker, more coaster, and pigmented; Location is found on the scalp and around the eyes; Lifecycle replaces much of the vellus hair after puberty, especially in males.

Q13: How does the integumentary system regulate body temperature?

1. Stimulus: Body temperature increases above the normal range (36.1–37.2°C or 97–99°F).

2. Receptor: Thermoreceptors in the brain detect the increased temperature.

3. Control Center: The heat-loss center in the hypothalamus receives signals from the thermoreceptors.

4. Effector/Response:

   1. Sweating: Sweat glands release sweat, which evaporates and cools the body.

   2. Vasodilation: Blood vessels in the skin dilate, increasing blood flow to the skin and releasing heat.

5. Return to Normal Range: Body temperature returns to normal, and the hypothalamus stops the heat-loss response.

Q14: How are burns classified, and what is the "rule of nines"?

• Classification:

  1. First-degree: Burns are least severe and only involve the epidermis (skin gets red, is painful, and is minor)

  2. Second-degree: Burns involves the epidermis and is part of the dermis (often sees blistering)

  3. Third-degree: Burns involving the epidermis and dermis are both destroyed (often called full thickness burns) is the most severe

     • Secondary infection problems in the future

     • Fluid loss problem in the future 

• Rule of Nines: This is a way to estimate total skin damage on a person; separating the adult body into regions based on the number nine

Definitions:

• Psoriasis: Autoimmune disorder causing rapid skin cell turnover and scaling

• Acne: Inflammation of sebaceous glands and hair follicles

• Jaundice: Yellowing of skin due to excess bilirubin

• Cyanosis: Blue skin due to lack of oxygen 

• Albinism: Lack of melanin production

• Erythema: Redness due to increased blood flow 

• Pallor:  Pale skin from reduced blood flow

• Decubitus ulcers: Bedsores from prolonged pressure

• Stretch marks/striae: Dermal tears due to rapid stretching

• Callus: Thickened skin from repeated friction

• Botox: Neurotoxin used to reduce wrinkles

• Fillers: Substances used to restore volume in skin