Integumentary System: Functions, Layers, Glands, and Pathology

Flashcard set covering the functions, tissue layers, epidermal cells, dermis structures, glandular secretions, thermoregulation, tattoos, skin cancers, and key proteins based on the lecture notes.

What are the 5 main functions of the skin?

1. Protection & maintaining fluid balance; 2. Temperature regulation (via hypothalamus & effectors); 3. Vitamin D synthesis; 4. Releasing small amounts of wastes (salts); 5. Sensory perception (touch, pain, heat).

What are the 3 main layers of the skin and their primary tissue types?

1. Epidermis: Stratified squamous epithelium (Avascular / no blood vessels); 2. Dermis: Connective tissue—Papillary layer is areolar ($20\%$), Reticular layer is dense irregular ($80\%$) (Vascular); 3. Hypodermis (Subcutaneous): Adipose (fat) tissue.

What are the layers of the epidermis from outermost to deepest, and what is the mnemonic used to remember them?

Mnemonic: 'Come lets get sun burned'. Layers: Corneum $\rightarrow$ Lucidum (only in thick skin like palms/soles) $\rightarrow$ Granulosum $\rightarrow$ Spinosum $\rightarrow$ Basale.

Which epidermal layer is living and where do cells actively divide?

Stratum Basale (the deepest layer, closest to the dermis's blood supply). Stratum Granulosum and below are living; everything above is dead/keratinized.

What are the 4 specialized cells found in the epidermis and their functions?

Keratinocytes: Produce keratin for waterproofing. Melanocytes: Produce melanin (pigment) to protect DNA from UV light. Langerhans Cells: Immune cells that patrol and present antigens to T-cells. Merkel Cells: Attached to nerve endings for light touch and pressure sensing.

Why do people around the world have different skin colors in terms of Folate and Vitamin D?

It is an evolutionary balance: High UV / Equator requires lots of melanin to protect against Folate (Vitamin B9) destruction, which is vital for reproduction. Low UV / North requires less melanin so sunlight can penetrate to allow Vitamin D synthesis.

What are the two layers of the dermis and what are dermal papillae?

Papillary Layer (top $20\%$): Areolar tissue containing dermal papillae (projections that increase surface area, attach to epidermis, and create fingerprints/friction ridges). Reticular Layer (bottom $80\%$): Dense irregular tissue containing collagen, elastin, blood vessels, and glands.

What causes acne in sebaceous glands, and what is the difference between a whitehead and a blackhead?

Sebaceous glands secrete oil (sebum) into hair follicles. If the duct gets blocked: a whitehead is a sealed-off bacterial infection, whereas a blackhead is a clogged follicle open to the surface.

What are the differences between Merocrine (Eccrine) and Apocrine sweat glands?

Merocrine (Eccrine): Found all over the body (except lips/genitals) and secretes water and salts for temperature control. Apocrine: Found only in armpits and groin, secretes proteins and fats, activated at puberty, and broken down by bacteria to cause body odor.

How does the skin regulate body temperature using blood vessels?

Vasodilation: Blood vessels expand when you're hot to release heat. Vasoconstriction: Blood vessels narrow when you're cold to conserve heat.

How does the process differ between a Henna tattoo and a Real tattoo?

Henna: Ink has low viscosity and stays in the epidermis only (temporary). Real Tattoo: Ink is injected deep into the dermis and locked in place by collagen and an immune cell response.

What are the three main types of skin cancer and their characteristics?

Basal Cell Carcinoma: Most common ($75\text{--}80\%$), least likely to spread, shiny red bump. Squamous Cell Carcinoma: $15\text{--}20\%$, red nodule/rough patch, high cure rate. Melanoma: $1\text{--}5\%$ of cases, most dangerous/likely to spread, dark mole-like.

What do the ABCD's of melanoma stand for?

Asymmetry, Border irregularity, Color variation, Diameter (> pencil eraser), and Evolving (changing).

What are the primary roles of the 4 major skin proteins: Keratin, Melanin, Collagen, and Elastin?

Keratin: Tough, waterproof protein in epidermis, hair, and nails. Melanin: Pigment protein that absorbs UV light to protect cell nuclei. Collagen: Provides structural strength in the dermis. Elastin: Allows skin to stretch and recoil.