The Integumentary System Flashcards
The integumentary system consists of the skin and various accessory structures
Describe the tissue structure of the integument (i.e., skin).
Two main parts of the integumentary system are the cutaneous membrane (made up of the epidermis and dermis) and the accessory structures.
Cutaneous membrane
- The epidermis consists of a stratified squamous epithelium.
- The dermis consists of a papillary layer of areolar tissue and a reticular layer of dense irregular connective tissue → the papillary layer is superficial to the reticular layer.
- The subcutaneous layer (i.e., hypodermis) separates the integument from the fascia around deeper organs. → this layer is not part of the integument.
Accessory structures
- Hair shaft
- Sweat gland ducts’ pores
- Tactile (Meissner’s) corpuscle
- Sebaceous gland
- Arrector pili muscle
- Sweat gland ducts
- Hair follicle
- Lamellar (Parcinian) corpuscle
- Nerve fibers
- Sweat glands
The epidermis is composed of strata (layers) that have various functions.
Describe the main structural features of the epidermis, and explain the functional significance of each feature.
- The epidermis is dominated by keratinocytes, the body’s most abundant epithelial cells → form strata that are continually produced in the deepest layers and shed at the exposed surface
- The deeper layrs of the epidermis form epidermal ridges that extend to the dermis and are adjacent to dermal projections called dermal papillae that project into the epidermis → significant beause they greatly increase the surface area for attachment, firmly binding the epidermis to the dermis.
- Like all other epithelia, the epidermis lacks local blood vessels → rely on diffusion of nutrients and oxygen from capillaries within the dermis → cells with the highest metabolic demand are closest to the underlying dermis
Explain what accounts for individual differences in skin colour.
Factors influencing skin colour include:
- presence of pigments in the skin
- the degree of dermal circulation
- thickness and degree of keratinization in the epidermis
Note: increased pigmentation (i.e., tanning) occurs in response to ultraviolet radiation.
The subcutaneous layer connects the dermis to underlying tissues
Describe the structures of the dermis and subcutaneous layer.
- The dermis lies between the epidermis and the subcutaneous layer
- Two fiber types are present → elastic and collagen
- Collagen fibers limit the flexibility of elastic fibers
- Aging, hormonal changes, and UV radiation permanently reduce the elasticity of the demris
- Collagen fibers limit the flexibility of elastic fibers
- The papillary layer of the dermis consists of highly vascularized areolar tissue → contains capillaries, lymphatic vessels, and sensory nerve fibers.
- The reticular layer consists of an interwoven meshwork of dense irregular connective tissue
- Two fiber types are present → elastin and collagen
- Both the papillary and reticular layer contain networks of blood vessels, lymphatic vessels, nerve fibers, and accessory organs (e.g., hair follicles and sweat glands)
- Two fiber types are present → elastic and collagen
- The subcutaneous layer is not part of the skin
- Separates the skin from deeper structures
- Stabilizes the skin’s position relative to underlying tissues while permitting independent movement
- Often dominated by adipocytes
Burns are significant injuries that damage skin integrity.
Describe the classification of burns.
-
First degree burn
- Only the surface of the epidermis is affected
- erythema (redness) results from inflammation of damaged tissues (e.g., sunburn)
-
Second degree burn
- The entire epidermis and some of the dermis are damaged
- Blistering, pain, and swelling occur
-
Third degree burn
- Destroys the epidermis and dermis, extending into the subcutaneous layer
- Less painful than 2nd degree, since sensory nerves are destroyed
- Cannot repair themselves because granulation tissue cannot form and epithelial cells are unable to recover
- Skin grafting is usually necessary
NOTE: Burns that cover more than 20% of the skin surface threaten critical homeostatic functions of the skin
Summarize the effects of aging on the skin. [10]
- Fewer melanocytes
- Drier epidermis
- Thinning epidermis
- Diminished immune response
- Thinning dermis
- Decreased perspiration
- Reduced blood supply
- Slower skin repair
- Fewer active follicles
- Altered hair and fat distribution
List some hormones that are necessary for maintaining health integument.
The integument responds to circulating hormones and has endocrine functions that are stimulated by ultraviolet radiation.
- Glucocorticoids
- Released during times of stress → loosen the connection between keratinocytes and reduce the effectiveness of the epidermis as a barrier to infection
- Thyroid hormones
- Maintain normal blood flow to the subpapillary plexus
- Sex hormones
- stimulate epidermal cell divisions, increasing thickness and accelerating wound repair
- also increase dendritic cell number
- stimulate epidermal cell divisions, increasing thickness and accelerating wound repair
- Growth factors
- stimulate cell growth and division
- Epidermal growth factor
- Produced by the salivary glands and glands of the duodenum
- Plays a role in
- Promoting basal cell division in the stratum basale and stratum spinosum
- Accelerating keratin production in maturing keratinocytes
- Stimulating epidermal development and epidermal repair after injury
- Stimulating sytheic activity and secretion by epithelial glands
- Growth hormone
- Stimulates fibroblast activity and collagen synthesis
- Also stimulates basal cell divisions, thickens epidermis, and promotes wound repair.
Explain how the skin responds to injury and is able to repair itself.
There are four phases in skin regeneration:
- Inflammation: mast cell activation triggers inflammation, which produces swelling, redness, heat, and pain.
- Migration: cells of the stratum basale are migrating along the edges of the wound, macrophages are removing debris (more are arriving via enhanced circulation, clotting around the edges of the area partially isolates the region from adjacent undamaged tissues
- The combination of blood clot, fibroblasts, and an extensive capillary network is called granulation tissue.
- Proliferation: phagocytic activity has almost ended, and the blood clot is disintegrating
- Scarring: a hollow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis
The integumentary system consists of skin and various accessory structures.
Describe the functions of the integumentary system. [8]
- Protect underlying tissues and organs against impact, abrasion, fluid loss, and chemical attack.
- Excrete salts, water, and organic wastes by integumentary glands.
- Maintain normal body temperature through either insulation or evaporative cooling, as needed.
- Produce melanin, which protects the underlying tissue from ultraviolet radiation
- Produce keratin, which protects against abrasion and serves as a water repellent.
- Synthesize vitamin D3, a steriod that is subsequently converted to calcitrol, a hormone important to normal calcium metabolism.
- Store lipids in adipocytes in the dermis and in adipose tissue in the subcutaneous layer
- Detect touch, pressure, pain, and temperatures stimuli, and relay that information to the nervous system.
What is the cutaneous plexus?
The network of arteries and veins connected to smaller vessels servicing the tissues of the integumentary system.
Compare thick skin and thin skin.
- Thin skin: covers most of the body surface and contains four strata
- Thick skin: found on the palms of the hands and the soles of the feet → contains a fifth stratum.
Identify the five layers of the epidermis (from superficial to deep).
- Stratum corneum → water-resistant not water-proof → contains 15-30 layers of keratinized cells
- Stratum lucidum → separates stratum corneum from deeper layers → cells are flattened, densely packed, and largely without organelles → contains dead and dehydrating proteins
- Stratum granulosum → by the time cells reach this layer, most have stopped dividing and started making large amounts of keratin and keratohyalin → cells grow thinner and become less permeable
- Stratum spinosum → contains dendritic cells, which participate in the immune response by stimulating defense against (1) microorganisms that manage to penetrate the superficial layers of the epidermis and (2) superficial skin cancers.
- Straum basale → basal layer dominated by basal cells (stem cells whose divisions replace the more superficial keratinocytes that are lost or shed at the surface → also contains Merkel cells involved with touch sensation
What is melanin?
A brown, yellow-brown, or black pigment produced by melanocytes.
What is the function of a melanosome?
Melanosomes travel within the processes of melanocytes and are transferred intact to keratinocytes. The transfer of pigmentation colours the keratinocyte temporarily, until the melanosomes are destroyed by fusion with lysosomes. In people with pale skin, this transfer occurs in the stratum basale and stratum spinosum, and the cells of the more superficial layers lose their pigmentation. In dark-skinned people, the melanocytes are more active, melanosomes are larger and more numerous, and the transfer may occur in the stratum granulosom as well. As a result, skin pigmentation is darker and more persistent.
What is a melanocyte?
Melanocytes are located in the stratum basale, squeezed between or deep to the epithelial cells. Melanocytes manufacture melanin from the amino acid tyrosine and package it in intracellular vesicles called melanosomes.
What is carotene?
Carotene is an orange-yellow pigment that normally accumulates in epidermal cells. It is most apparent in the stratum corneum cells of light-skinned people, but it also accumulates in fatty tissues in the deep dermis and hypodermis. Carotene is found in orange vegetables, such as carrots and some squashes.
How does the blood supply affect skin colour?
Blood cells are filled with red pigment (hemoglobin). When hemoglobin is bound to oxygen it appears bright red, giving capillaries in the dermis a reddish tint that is most apparent in lightly pigmented people. If the vessels dilate (e.g., when exercising), the red tones become more pronounced. A light-skinned person may ‘turn white’ from a sudden drop of blood supply to the skin (e.g., when frightened).
