Integumentary System - Lecture Notes (Flashcards)

Flashcards covering major topics from the notes: skin structure, epidermal/dermal anatomy, cells, layers, glands, hair, nails, and skin functions.

What is the largest organ in the body?

Skin (the integumentary system).

What is the range of skin thickness from eyelids to heels?

Less than 0.5 mm at eyelids to 4 mm on the heels.

What is the typical thickness of skin over most of the body?

About 1–2 mm.

What are the main components of the integumentary system?

Skin and accessory structures: hair, sebaceous glands, sudoriferous (sweat) glands, nails, and sensory receptors.

List the epidermal layers from outermost to innermost.

Stratum corneum, stratum lucidum (thick skin only), stratum granulosum, stratum spinosum, stratum basale.

Name the four main epidermal cell types.

Keratinocytes, melanocytes, Langerhans cells, Merkel cells.

What percentage of epidermal cells are keratinocytes?

About 90%.

What do keratinocytes produce and release?

Keratin; lamellar granules release a water-repellant sealant that reduces water loss and entry of microorganisms.

What percentage of epidermal cells are melanocytes?

About 8%.

Which epidermal layer contains melanocytes?

Stratum basale.

What is the Merkel cell and what does it do?

A touch receptor located in the deepest layer of the epidermis (stratum basale) that detects touch.

Where are Meissner's corpuscles located and what do they sense?

In the dermal papillae of the papillary layer; sense light touch.

What are Langerhans cells and their role?

Immune cells in the epidermis that help other immune cells recognize invaders.

What is stratum granulosum known for?

3–4 layers of flattened keratinocytes undergoing apoptosis; keratohyalin and lamellar granules; final stages of keratinization.

What is stratum spinosum known for?

8–10 layers of polyhedral cells with spine-like projections; beginning keratinization.

What is stratum lucidum and where is it found?

A clear layer present in thick skin (fingertips, palms, soles).

What is stratum corneum and its characteristics?

25–30 layers of dead keratinocytes; inner cell contents mainly keratin; desquamation; lamellar granules between cells; friction can form callus.

What is stratum basale's function and features?

Single layer of actively mitotic keratinocytes; attached to dermis; nutrients from dermal vessels; melanocytes and Merkel cells scattered; melanin produced here.

Name the two main layers of the dermis.

Papillary region and Reticular region.

What structures are located in the papillary region?

Areolar connective tissue with dermal papillae containing capillary loops, Meissner's corpuscles, and free nerve endings; contributes to fingerprints.

What is the dermo-epidermal junction?

A junction where dermal papillae fit with epidermal ridges to form a strong boundary that resists shearing.

Which dermal fibers provide skin strength and elasticity?

Collagen provides strength, Reticular fibers provide support, Elastic fibers provide elasticity.

What are the main cell types in the dermis?

Fibroblasts, macrophages, and a few adipocytes near the boundary with subcutaneous tissue.

What structures are contained in the reticular dermis?

Sebaceous and sweat glands, arrector pili muscles, hair follicles, Pacinian corpuscles, and some adipose tissue.

What is the function of Pacinian (Lamellar) corpuscles?

Detect deep pressure and vibration; located in the dermis.

Where are sebaceous glands located and what do they secrete?

Connected to hair follicles; secrete sebum.

Where are eccrine sweat glands most abundant and what do they secrete?

Most abundant on the forehead, palms, and soles; secrete a watery sweat composed of water, ions, wastes; about 600 mL/day.

What are the two main sweat gland types?

Eccrine (merocrine) and Apocrine.

Where are eccrine glands distributed and where do they open?

Distributed throughout the skin; secretory portions in the deep dermis; ducts open to the surface as pores.

Where are apocrine glands located and how do they secrete?

Mainly in the groin, axilla, areola, and beard areas; secretory portions in subcutaneous layer; ducts open into hair follicles; secretions are viscous and milky with lipids and proteins.

What is the function of apocrine secretions and when do they function?

Contribute to body odor; become active after puberty; function not primarily in thermoregulation.

What is the role of the arrector pili muscle?

Contraction pulls hair upright (goose bumps) and elevates the skin around hair follicles.

What is sebum and its function?

Sebaceous gland secretion; coats hair, prevents drying, reduces water loss, and inhibits some bacteria.

What are ceruminous glands and where are they located?

Modified sweat glands in the external ear; produce cerumen (earwax) with sebaceous secretions.

What are nails and what are their parts?

Plates of tightly packed dead keratinized cells; parts: nail body, free edge, nail bed, lunula, nail root.

What is the primary function of nails?

Protect the dorsal distal tips of the digits.

What are the hair types listed in the notes?

Lanugo, Terminal, and Vellus hairs.

Describe lanugo hair.

Very fine, non-pigmented downy hair present by the fifth month of fetal development.

Describe terminal hair.

Long, coarse, heavily pigmented hairs found on the scalp, eyebrows, eyelashes, and in areas like axilla and pubic regions.

Describe vellus hair.

Short, fine pale hairs that are barely visible; puberty-related transformation to terminal hair in some regions.

What are the hair shaft, root, and papilla?

Shaft is the visible part; root penetrates the dermis; papilla contains connective tissue and blood vessels.

What is the glycorlipid-containing layer in the epidermis that aids water loss prevention?

Lamellar granules in the stratum granulosum release a water-repellant sealant.

What role does the epidermis play in vitamin D synthesis?

Activation of precursor molecules by UV rays in sunlight.

What portion of total blood flow is stored in the skin?

About 8–10% of the total blood flow.

What is the hypodermis and its function?

Also called the subcutaneous layer or superficial fascia; lies below the dermis; primarily adipose tissue; anchors skin and insulates; energy reserve.