Integumentary System Flashcards
What are the two major components of the integumentary system? What are the 5 subtypes?
Skin (cutaneous membrane) –> epidermis, dermis
Accessory structures –> exocrine glands, hair, nails
What are the major functions of the integumentary system?
- Physical and immunological protection
- Thermoregulation
- Sensation
- Metabolic functions (VitD synthesis, stores NRG as subcutaneous fat)
What is the tissue composition of the integumentary system?
- Epithelium: covers surface, forms boundary
- Connective tissue: supports epithelium, provides strength and resiliency
- Muscle tissue: controls diameter of blood vessels, adjusts hair position
- Nerve: controls smooth muscle, generates sensation, stimulates exocrine glands
What are the three major characteristics of the skin?
- Largest organ in the body (15% of total body mass)
- Covers areas of 2m squared
- Ranges in thickness between 0.5-4.0 mm (average of 1-2 mm)
What are the three layers of the skin from superficial to deep?
Epidermis (stratified squamous)
Dermis (elastic fibers)
Hypodermis (subcutaneous layer of fat)
What forms the interface between dermis and epidermis? Where do we find differences?
Epidermal ridge (on the epidermis)
Dermal papilla (on the dermis)
Peak and valley between dermis and epidermis allows for a tight bond between different layers of skin (resists shearing)
Stronger in thick skin because it shears and moves more, this is where the interface is more pronounced
What is the structure of the epidermis from surface level to deep? (7) Which layer is only in one spot?
Stratum corneum
Stratum lucidum (ONLY in sole and palm)
Stratum granulosum, stratum spinosum, stratum germinativum
Dermal papilla and Dermis
What is the structure of the stratum germinativum? (4)
Also known as stratum basale
Composed of large basal cells (stem cells that divide give rise to new keratinocytes, most abundant epithelial cells in epidermis)
Firmly attached to basal lamina
What is the structure of the stratum spinosum? (4)
ALso known as spiny layer
Composed of keratinocytes containing bundles of tonofilaments (protein filaments) that act as cross braces (begin and end between adjacent cell junctions, desmosomes)
Desmosomes attach keratinocytes together
Keratinocytes still capable of division
What is the structure of the stratum granulosum? (4)
Granular layer
Production of large quantities of keratohyalin and keratin (accumulation of keratohyalin leads to keratohyalin granules)
Granules excrete lipids that fill spaces between keratinocytes (form water repellent sealant)
Sealant prevents cell diffusion leading to keratinocyte death
What is the structure of the stratum lucidum? (3)
Clear layer
Large amounts of keratin and thickened plasma membranes
Only found in volar skin (palmar and plantar)
What is the structure of the stratum corneum? (5)
Corne (hoof like or hard)
Multiple layers of dead cells
Cells continuously shed and replaced
Water repellant layer
Protection against abrasion and microbial invasion
What is the difference between thick and thin skin?
Thin skin has thinner stratum corneum, other epidermal layers are less clear, dermal papillae and epidermal ridges are less developed
Thick skin has more shearing and abrasive stress
What is the structure of the papillary layer of the dermis? (4)
Thinner layer, areolar connective tissue, dermal papillae increase area of contact with epidermis, contains nerve endings (touch, temperature, pain)
What is the structure of the reticular layer of the dermis? (4)
Thicker layer, dense irregular connective tissue, many elastic fibers, provides extensibility and elasticity to the skin
What are lines of cleavage? Why are these significant?
Collagen fiber bundles in dermis align differently in different regions of the body
Collagen fibers align along lines of tension and form lines of cleavage (depressions, small)
Clinically significant- cut parallel to line of cleavage will close, cut perpendicular will remain open and scar
What is the structure of the hypodermis? (4)
Also known as superficial fascia (fat)
Stabilizes position of skin relative to underlying tissues
Loose connective tissue that stores fat (distribution of subcutaneous fat differs between sexes, and influences shape and contours of the body)
What are Merkel cells? (4)
Specialized skin cells, least common cell type, located in stratum germinativum (basal layer)
Important role in touch sensation
What are Langerhans cells? (4)
Specialized skin cells, originate from bone marrow and migrate to epidermis
Phagocytic abilities
Important role for immune response
What are melanocytes? (4)
Specialized skin cells, about 8% of epithelial cells
Produce melanin pigment
Contain long and slender processes (insert between keratinocytes)
Transfer melanin granules to keratinocytes
What is involved in the anatomy of skin colour?
BLood supply to dermis- hemoglobin in dermal blood vessels, O2 HB leads to pink hue, deO2 HB leads to blue hue (cyanosis), and blood vessel dilation (more blood) leads to redness of skin
Thickness of the stratum corneum
Variable quantities of three pigments- carotene (yellow/orange), pheomelanin (red/yellow), melanin (brown/black)
What is the function of melanin? How does it make lighter and darker skin?
Melanosomes (vesicles) are transferred to keratinocytes and color them (pigmentation)
Keratinocytes move superficially, melanosomes destroyed by lysosomes (pigmentation lose)
Darker skin- larger melanosomes, transfer to K persists to more superficial layers of skin (more present pigment)
Melanocytes increase rate of melanin synthesis and transfer in response to UV radiation exposure to prevent DNA damage
How does UV induced skin damage affect the epidermis and dermis?
Epidermis: chromosomal damage, causes skin cancer (basal cell carcinoma)
Dermis: damage to fibroblasts, alters composition of ECM, premature wrinkling
What are the two types of exocrine glands found in the IS (accessory structures)
- Sweat glands: secrete H20 and electrolytes (merocrine secretion via exocytosis, also known as eccrine)
- Sebaceous glands: secrete oily lipid (sebum) that coats hair shafts and skin surface (holocrine secretion, cell dies)
What are some features of the sweat gland? (3)
Simple, coiled tubular glands
Release secretions onto skin via merocrine (eccrine)
secretion
Two types: apocrine SG (secrete odiferous sweat), and merocrine (eccrine) SG (secrete normal sweat)
What are some features of merocrine sweat glands? (3)
Widespread, distributed across most of body
Secrete water and electrolytes
Regulate body temp
What are some features of apocrine SG?
Merocrine (eccrine) secretion mechanism
Specific to some body regions (groin, axilla, breast areola, male facial hair)
Secretion of water, electrolytes, lipids, proteins (acted on by bacteria to produce odor)
Stimulated during emotional stress and arousal
What are the two types of special apocrine glands?
Ceruminous glands: modified apocrine SG, secrete waxy cerumen (ear wax) via merocrine/ eccrine secretion
Mammary glands: modified apocrine SG specialized for milk production, true apocrine secretion method (sheds cytoplasm), regulation by interaction of sexual and pituitary hormones
What are some features of sebaceous SG? (3)
Acne is inflammation of sebaceous SG and follicles
Inflammation results from blockage of ducts and bacterial infection of glands
Usually occurs at onset of puberty (glands increase in size and sebum secretion increases in response to sex hormones)
What are some features of hair (another accessory structure)? (5)
About 5 million hairs on body (2% on the head)
Covers all body surfaces except volar skin (hand/feet)
UV protection and thermal insulation of head
Particle filtration for eye and nose
Touch sensation for most of body
What is the anatomy of a hair follicle?
Exposed shaft of hair, hair shaft (boundary between shaft and root), sebaceous gland, arrector pili muscle (autonomic smooth muscle), hair root, connective tissue sheath, hair bulb, hair papilla
What are the three types of hair?
Vellus hairs (fine, peach fuzz, over most of body)
Intermediate hairs (hairs of the limbs, change in distribution in response to sex hormones)
Terminal hairs (heavier more pigmented, scalp, eyebrow, eyelash)
What is the hair growth cycle? (scalp hair)
Grows for about 2-6 years
Rests for 3 months (club hair), then new hair pushes out old one
85% of hairs in growth phase at any given time
What is the structure of the nail bed?
Nail root: where the nail grows from
Nail bed: root/body sit here, epithelial cells from epidermis
Nail body: visible part of the nail, free edge is not attached
Lunula: white crescent, not present if you have kidney or heart disease
Eponychium: cuticle forms, seals nail (stratum corneum), prevents infection
