Integumentary System Quiz

Integumentary System

• The integumentary system is made up of skin, glands, hair, nails, and other associated structures
• It forms a protective barrier, the largest organ of the body in surface area and weight (approximately 2 square meters and 4.5-5kg)
• It plays a crucial role in regulating body temperature and preventing dehydration
• It provides protection from the external environment, protecting from light, heat waves, bacteria, and chemicals.

Skin Structure

• The skin has three main layers: epidermis, dermis, and subcutaneous layer (or hypodermis)

Epidermis

• The outermost layer of the skin, avascular (lacking blood vessels)
• Composed of keratinized stratified squamous epithelium
• Divided into 4-5 layers of cells: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale
• Stratum corneum - outermost layer; dead, keratinized cells
• Stratum lucidum - translucent layer, only present in thick skin (palms and soles)
• Stratum granulosum - contains keratin and lamellar granules, where keratinization begins
• Stratum spinosum - several layers of keratinocytes
• Stratum basale - deepest layer, closest to the dermis; contains melanocytes and tactile epithelial cells (for sensory reception); Contains stem cells that form new cells

Epidermis Clinical Applications

• Dandruff - excess of keratinized cells shed from the scalp
• Psoriasis - chronic skin disorder characterized by rapid keratinocyte division and movement through the epidermal layers
• Skin cancers - prolonged exposure to UV radiation in sunlight can lead to basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.
• Skin grafts - necessary when stratum basale is destroyed

Dermis

• The middle layer of the skin; rich in blood vessels, nerves, hair follicles, and various glands
• Composed of papillary and reticular regions
• Papillary region - lies just below the epidermis, containing blood vessels, free nerve endings, hair follicles, and touch receptors (Meissner corpuscles)
• Reticular region - consists of dense irregular connective tissue, containing collagen and elastic fibers, adipose cells, hair follicles, sebaceous glands, and sweat glands.

Dermis Clinical Applications

• Striae (stretch marks): rupture of elastic fibers in the dermis, caused by over stretching the skin.
• Lines of cleavage (tension lines): predominant directions of underlying collagen fibers in the dermis; useful for surgeons.
• Fingerprint formation: dermal papillae contours reflected in the epidermal ridges, forming unique fingerprints.

Subcutaneous Layer

• Also called the hypodermis
• Not part of the skin itself
• Attaches the skin to underlying tissues and organs
• Contains blood vessels, nerves (pacinian corpuscles - detect pressure), and fatty tissue (cushioning and insulation)

Sensory Receptors

• The skin contains various sensory receptors to detect different sensations (e.g., touch, pressure, temperature, pain)
• Superficial receptors: Merkel discs, free nerve endings, Meissner corpuscles, and hair root plexuses.
• Deep receptors: Pacinian corpuscles

Skin Color

• Melanin, hemoglobin, and carotene are the main factors influencing skin color.
• Melanin - produced by melanocytes in the stratum basale; determines skin color from pale to black; protects from harmful UV radiation
• Hemoglobin - oxygen-carrying pigment in red blood cells; gives pink/red hue to skin due to blood flow in the dermis.
• Carotenes - yellow-orange pigments found in the stratum corneum, dermis, and subcutaneous layer

Skin Color Clinical Applications

• Freckles - increased melanin concentration in response to sunlight exposure
• Erythema - redness caused by dilated capillaries due to injury, heat, infection, or inflammation.
• Jaundice - yellow discoloration caused by bilirubin buildup; indicative of liver disease.
• Pallor - paleness caused by reduced blood flow, shock, or anemia
• Albinism - congenital disorder characterized by complete or partial absence of pigment in skin, hair and eyes due to an enzyme defect
• Vitiligo - autoimmune disease causing depigmentation patches due to destruction of melanocytes.
• Nevi (moles) - chronic, benign lesions of skin; distinguished from cancerous melanomas.

Tattooing and Body Piercing

• Tattooing - permanent coloration of dermis with foreign pigment using needles.
• Body piercing - insertion of jewelry through the skin using needles; can result in infections, allergic reactions, and anatomical damage (such as nerve or cartilage deformation)

Accessory Structures of the Skin

• Hair
• Sebaceous glands
• Nails
• Sweat glands

Hair

• Shaft - superficial portion
• Root - penetrates the dermis and hypodermis; consists of follicle, matrix (produce new hairs), and associated structures (arrector pili muscles & sebaceous glands)
• Papilla - contains blood vessels that nourish the growing hair
• Hair Growth Cycle - a growing stage and a resting stage; can be affected by various factors (illness, diet, stress, gender)
• Hair Removal - methods like electrolysis

Hair Clinical Applications

• Chemotherapy - hair loss due to drug effects on hair matrix
• Hirsutism - excessive body hair in abnormal amounts in females or prepubertal males

Skin Glands

• Sebaceous glands (oil glands)
• Sudoriferous glands (sweat glands): eccrine and apocrine sweat glands

Sebaceous Glands

• Connected to hair follicles
• Secrete sebum (oil)
• Located in the dermis
• Absent in palms and soles
• Sebum prevents water loss, softens/moistens hairs & skin.

Sudoriferous Glands (Sweat Glands)

• Eccrine & Apocrine sweat glands
• Eccrine sweat glands: widespread throughout the body; regulate body temperature through evaporation; produce sweat, eliminate urea, and activated soon after birth; stimulated by sympathetic nerve signals
• Apocrine sweat glands: located in axilla, pubis, areola; secrete a slightly viscous sweat; become active during sexual excitement and emotional stress causing odor in presence of bacteria.

Ceruminous Glands

• Present in external auditory canal (outer ear canal)
• Secrete cerumen (earwax); which protects from foreign materials, bacteria and fungi.

Nails

• Keratinized plates; composed of tightly packed, hard, and dead epidermis cells

Nail Structure

• Nail body
• Free edge
• Nail root
• Lunula (whitish area)
• Eponychium (cuticle, skin covering base of nail)
• Hyponychium (nail bed at tip of finger)

Nail Function

• Aid in grasping and manipulating small objects
• Protect the ends of the digits
• Produce new nails via cell division of nail matrix

Skin Functions

• Body temperature regulation
• Blood storage
• Protection from the external environment
• Detection of cutaneous sensations
• Excretion of substances
• Synthesis of vitamin D