PBHM Week 5 -Integumentary System Must-know list PDF

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These are comprehensive notes for everything you need to know to be successful for the topic of the integumentary system within the PBHM course...

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Integumentary System Must-know list 5.1 What is the structure of skin? The skin consists of two layers: the epidermis and dermis • List the two layers of skin and briefly describe subcutaneous tissue. - The 2 layers of the skin consist of the Epidermis and Dermis. 1. Epidermis: superficial region of skin - consists of epithelial tissue - avascular (no blood vessels in area) 2. Dermis: underlies/deep to Epidermis - mostly fibrous connective tissue - vascular 3. Hypodermis (subcutaneous tissue) - the Hypodermis is not part of the skin, but plays a role in anchoring the skin to underlying structures, mostly muscles. - mostly consists of Adipose tissue that shock absorbs and insulates.

5.2 Epidermis The epidermis is a keratinized stratified squamous epithelium •

Name the tissue type composing the epidermis. - the Epidermis consists mostly of keratinized stratified squamous epithelium - 4 cell types are found in the Epidermis:

1. Keratinocytes: - produce fibrous Keratin - major cells of the Epidermis - tightly connected by desmosomes - millions are slought off every day 2. Melanocytes: - located in the deepest Epidermis - produce a pigment called melanin 3. Dendritic (Langerhans) cells: - Macrophages that patrol deep epidermis, key activators of immune system 4. Tactile (Merkel) cells: - Sensory receptors that sense touch

Cross section of the Skin.

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List its major layers and describe the functions of each layer. - the Epidermis consists of 4 or 5 layers (strata) depending whether it is Thick skin that has 5 layers (found on hands and feet) or Thin skin which has 4 layers. - 5 layers of the skin:

1. Stratum Basale: - this layer is the base (deepest) layer - responsible for proliferation of cells via Mitosis, cells that are old or die move towards surface of skin - this layer firmly attached Epidermis to Dermis. 2. Stratum Spinosum: - Several cell layers thick - Cells contain weblike system of intermediate prekeratin filaments attached to desmosomes, allows them to resist tension and pulling (provides strength) - Keratinocytes in this layer appear spikey, so they are called prickle cells 3. Stratum Granulosum: - this layer is 4-6 cells thick, but cells are flattened, so therefore the layer is thin. - Keratinization begins in the Stratum Granulosum - Cells also accumulate lamellar granules, water-resistant glycolipid that slows water/fluid loss. This essentially provides a water-proofing mechanism in the layer. 4. Stratum Lucidum (Found only in thick skin) - Consists of thin, translucent band of 2-3 rows of clear, flat, dead keratinocytes - Lies superficial to the Stratum Granulosum - responsible for the capability of the skin to stretch - this thick layer also lowers the effects of friction in skin, especially in regions like the soles of feet and palms of hands 5. Stratum Corneum: - 20–30 rows of flat, anucleated, keratinized dead cells - Accounts for 3/4 of epidermal thickness - Though dead, cells still function to: 1) Protect deeper cells from the environment 2) Prevent water loss 3) Protect from abrasion and penetration 4) Act as a barrier against biological, chemical, physical assault - Cells change by going through apoptosis (controlled cell death) - Dead cells slough off as dandruff and dander

5.3 Dermis The dermis consists of papillary and reticular layers • Background of the Dermis layer: - Strong, flexible connective tissue - Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells - Fibers in matrix bind body together - Contains nerves, blood vessels, lymphatic vessels - Contains epidermal hair follicles, oil glands, sweat glands •

Name the tissue types composing the dermis. - the dermis is a fibrous structure composed of collagen, elastic tissue, and other extracellular components that includes vasculature, nerve endings, hair follicles, and glands

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List its major layers and describe the functions of each layer. 1. Papillary - Superficial layer of areolar connective tissue consisting of collagen, elastic fibers, & blood vessels - Loose fibers allow phagocytes to patrol for microorganisms - Dermal papillae: superficial region of dermis that sends fingerlike projections up into epidermis - In thick skin, Dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges - Collectively ridges are called friction ridges • Enhance gripping ability • Contribute to sense of touch • Sweat pores in ridges leave unique fingerprint pattern

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Reticular Makes up ~80% of dermal thickness Consists of coarse, dense fibrous connective tissue Cutaneous plexus: network of blood vessels between reticular layer and Hypodermis Extracellular matrix contains pockets of adipose cells Cleavage (tension) lines in reticular layer are caused by many collagen fibers running parallel to skin surface Externally invisible Important to surgeons because incisions parallel to cleavage lines heal more readily

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Flexure lines of reticular layer are dermal folds at or near joints Dermis is tightly secured to deeper structures Skin’s inability to slide easily for joint movement causes deep creases Visible on hands, wrists, fingers, soles, toes

5.4 What causes skin color? Melanin, carotene, and hemoglobin determine skin color • Describe the factors that normally contribute to skin color. - 3 pigments contribute to skin colour, Melanin, Carotene and Hemoglobin 1. Melanin • Only pigment made in skin; made by melanocytes - Packaged into melanosomes that are sent to keratinocytes to shield DNA from sunlight - Sun exposure stimulates melanin production • Two forms: reddish yellow to brownish black • All humans have same number of keratinocytes, so color differences are due to amount and form of melanin • Freckles and pigmented moles are local accumulations of melanin 2. Carotene • Yellow to orange pigment • Most obvious in palms and soles • Accumulates in stratum corneum and hypodermis • Can be converted to vitamin A for vision and epidermal health 3. Hemoglobin • Pinkish hue of fair skin is due to lower levels of melanin • Skin of Caucasians is more transparent, so color of hemoglobin shows through

• Briefly describe how changes in skin color may be used as clinical signs of certain disease states. • Homeostatic imbalances lead to clinical signs of certain disease states of skin colour. - Excessive sun exposure damages the skin, this causes: - Elastic fibers clump, causing skin to become leathery - Can depress immune system and cause alterations in DNA (mutations) that may lead to skin cancer - UV light destroys folic acid - Photosensitivity is increased reaction to sun - Some drugs (e.g. antibiotics, antihistamines) and perfumes cause photosensitivity, leading to skin rashes • Alterations in skin colour can indicate disease Disease

Cause

Skin colour

Cyanosis

Low oxygenation of hemoglobin

Blue

Erythema

Fever, hypertension, inflammation, allergy

Redness

Pallor

Anemia, low blood pressure, fear, anger

Blanching or pale colour

Jaundice

Liver disorders

Yellow cast

Bronzing

Inadequate steroid hormones

Bronze

Bruises

Clotted blood beneath the skin

Black and blue marks

The appendages of the skin 5.5 Hair Hair consists of dead, keratinized cells • List the functions of the hair. 1. Warn of insects on skin 2. Hair on head guards against physical trauma 3. Protect from heat skin 4. Shield skin against sunlight •

Name the chief regions of a hair. - Hairs (pili): flexible strands of dead, keratinized cells - Produced by hair follicles - Contains hard keratin, not like soft keratin found in skin - Hard keratin is tougher and more durable, and cells do not flake off • Regions: 1. Shaft: area that extends above scalp, where keratinization is complete 2. Root: area within scalp, where keratinization is still going on

5.6 Nails Nails are scale-like modifications of the epidermis • Describe the structure of and function of nails. Structure -

Modifications of epidermis that contains hard keratin Consists of free edge, nail plate and root Nail bed is epidermis underneath keratinized nail plate Nail folds: skin folds that overlap border of nail

Function -

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Nail matrix: thickened portion of bed responsible for nail growth Nails act as a protective cover for the external distal end of fingers and toes. The hard keratin provides the hardness of the nail and is different to the keratin found in the skin and

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Eponychium: nail fold that projects onto surface of nail body, also called Cuticle Hyponychium: area under free edge of plate that accumulates dirt Lunule: thickened nail matrix, appears white

hair.

Cross section of nail

5.7 Sweat and sebaceous glands Sweat glands help control body temperature, sebaceous glands secrete sebum • Compare the locations of sweat and oil glands. Sweat glands Location: found on all skin surfaces except for nipples and external genital region. - There are 2 types of sweat glands: 1. Eccrine - the most numerous type and is abundantly found on palms, soles and forehead 2. Apocrine - confined to axillary and anogenital areas. - Ceruminous glands: lining of external ear canal.

Sebaceous oil glands Location: Widely distributed except for thick skin found on palms and soles. • Most develop from hair follicles and secrete into hair follicles • Relatively inactive until puberty – Stimulated by hormones, especially androgens

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Compare the composition and functions of their secretions. Sweat glands Composition: Contain myoepithelial cells. Contract upon nervous system stimulation to force sweat into ducts Functions of Eccrine sweat glands: - Thermoregulation which is regulated by the sympathetic nervous system - Their secretion is sweat 99% water, salts, vit C, antibodies, dermcidin (microbe-killing peptide), metabolic wastes

Sebaceous oil glands Composition: oily holocrine secretion which is Sebum Function: these glands secrete Sebum to soften hair and skin, and also act as a bactericidal (bacteria-killing) property.

Functions of Apocrine sweat glands: • Secrete viscous milky or yellowish sweat that contains fatty substances and proteins – Bacteria break down sweat, leading to body odor • Begin functioning at puberty • Modified apocrine glands – Ceruminous glands: lining of external ear canal; secrete cerumen (earwax) – Mammary glands: secrete milk

5.8 What are the functions of the skin? • Describe how the skin accomplishes at least five different functions. 1. Protection - Skin is exposed to microorganisms, temperature extremes, abrasions and harmful chemicals. ☐ The skin has 3 barriers ● Chemical barrier, the skin secretes many chemicals, such as: • Sweat, which contains antimicrobial proteins • Sebum and defensins, which kill bacteria • Cells also secrete antimicrobial defensin – Acid mantle: low pH of skin retards bacterial multiplication – Melanin provides a chemical barrier against UV radiation damage ● Physical barrier – Flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and water soluble substances – Some chemicals have limited penetration of skin • Lipid-soluble substances • Plant oleoresins (e.g., poison ivy) • Organic solvents (acetone, paint thinner)

• Salts of heavy metals (lead, mercury) • Some drugs (nitroglycerin) • Drug agents (enhancers that help carry other drugs across skin) ● Biological barrier – Epidermis contains phagocytic cells • Dendritic cells of epidermis engulf foreign antigens (invaders) and present to white blood cells, activating the immune response – Dermis contains macrophages • Macrophages also activate immune system by presenting foreign antigens to white blood cells – DNA can absorb harmful UV radiation, converting it to harmless heat

2. Body temperature regulation • Under normal, resting body temp, sweat glands produce about 500 ml/day of unnoticeable sweat – Called insensible perspiration • If body temp rises, dilation of dermal vessels can increase sweat gland activity to produce 12 L (3 gallons) of noticeable sweat – Called sensible perspiration; designed to cool body • Cold external environment – Dermal blood vessels constrict – Skin temperature drops to slow passive heat loss – These responses are in negative feedback mechanisms which regulate body temperature.

3. Cutaneous sensations • Cutaneous sensory receptors are part of the nervous system – Exteroreceptors respond to stimuli outside body, such as temperature and touch – Free nerve endings sense painful stimuli 4. Metabolic functions • Skin can synthesize vitamin D needed for calcium absorption in intestine • Chemicals from keratinocytes can disarm some carcinogens • Keratinocytes can activate some hormones – Example: convert cortisone into hydrocortisone • Skin makes collagenase, which aids in natural turnover of collagen to prevent wrinkles 5. Blood reservoir • Skin can hold up to 5% of the body’s total blood volume • Skin vessels can be constricted to shunt blood to other organs, such as an exercising muscle 6. Excretion of wastes • Skin can secrete limited amounts of nitrogenous wastes, such as ammonia, urea, and uric acid • Sweating can cause salt and water loss

5.9 What happens when things go wrong? • Describe briefly: first-, second-, and third-degree burns 1. First degree burns - Epidermal damage only 2. Second degree burns - Epidermal and upper Dermal damage 3. Third degree burns - Entire thickness of skin involved (full-thickness burns)...