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Integumentary System

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Greg Horesovsky

on 27 June 2017

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Transcript of Integumentary System

Integumentary
System

General Structure of the Integumentary System
Subcutaneous Layer (Superficial Fascia or Hypodermis)
Loose connective tissue
Sub- (below or under) Below the dermis
Location of hypodermic injections
Hypo- (below or under)
Derma- (skin) Dermatologist
Introduction to the Integumentary System
Accessory Structures
Originate in the dermis
Extend through the epidermis to the skin surface:
Hair
Nails
Multicellular exocrine glands
Introduction to the Integumentary System
The cutaneous membrane has two components
Outer epidermis:
Superficial epithelium (epithelial tissues)
Epi- (above or over)
Inner dermis:
Connective tissues
Introduction to the Integumentary System
The integument is the largest system of the body
16% of body weight
1.5 to 2 m2 in area
The integument is made up of two parts:
Cutaneous membrane (skin)
Accessory structures
Introduction to the Integumentary System
Functions of Skin
Protects underlying tissues and organs
Maintains body temperature (insulation and evaporation)
Synthesizes vitamin D3
Stores lipids
Detects touch, pressure, pain, and temperature
Excretes salts, water, and organic wastes (glands)
Introduction to the Integumentary System
Introduction
Epidermis
Vitamin D3
Epidermal cells produce cholecalciferol (vitamin D3):
UV radiation stimulates production of vitamin D3
Liver and kidneys convert vitamin D3 into calcitriol:
To aid absorption of calcium and phosphorus in the large intestine
Insufficient vitamin D3:
Can cause rickets
The Epidermis and Vitamin D3
Function of Melanocytes
Melanin protects skin from sun damage
Ultraviolet (UV) radiation
Causes DNA mutations and burns that lead to cancer and wrinkles
UV radiation stimulates melanin production (sun tan!)
Skin color depends on melanin production, not on the number of melanocytes
Albinoism (defect in production of melanin pigment)
Albinos have melanocytes, just no melanin
Skin Color
Two pigments
Carotene:
Orange-yellow pigment
Found in orange vegetables
Accumulates in epidermal cells and fatty tissues of the dermis
Can be converted to vitamin A
Melanin:
Yellow-brown or black pigment
Produced by melanocytes in stratum germinativum
Stored in transport vesicles (melanosomes)
Transferred to keratinocytes
Blood circulation (red blood cells)
The Role of Pigmentation
Keratinization
The formation of a layer of dead, protective cells filled with keratin (a tough waterproof protein)
Occurs on all exposed skin surfaces except eyes
Skin life cycle
It takes 2 to 4 weeks for a cell to move from stratum germinativum to stratum corneum
Epidermis
The “Horn Layer”
Corn- (horn) Cornucopia
Exposed surface of skin
15 to 30 layers of keratinized cells
Water resistant
Shed and replaced every 2 weeks
Stratum Corneum
Stratum Spinosum
The “spiny layer”:
Produced by division of stratum germinativum
Eight to ten layers of keratinocytes bound by desmosomes
Cells shrink until cytoskeletons stick out (spiny)
Cyto- cell
Intermediate Strata
The “germinative layer”
Germinare (to start growing)
Has many germinative (stem) cells or basal cells
Forms epidermal ridges (e.g., fingerprints)
Dermal papillae (tiny mounds):
Increase the area of basal lamina
Strengthen attachment between epidermis and dermis
Stratum Germinativum
Structures of the Epidermis
The five strata (layers) of keratinocytes in thick skin
From basal (bottom) lamina (thin flat plate) to free surface:
Stratum germinativum GOOD
Stratum spinosum STUDENTS
Stratum granulosum GENERALLY
Stratum lucidum LOVE
Stratum corneum CLASS
Epidermis
Structure of the Epidermis
Thin Skin
Covers most of the body
Has four layers of keratinocytes (Keros- horn; cyte- cell)
Thick Skin
Covers the palms of the hands and soles of the feet
Has five layers of keratinocytes
Epidermis
Epidermis is
Avascular ( a- no ; vascular- blood vessels) stratified squamous epithelium:
Nutrients and oxygen diffuse from capillaries in the dermis
Stratified (stacked in layers)
Squamous (squama- scale)
Epidermis
UV radiation stimulates vitamin D3 production which is essential for maintaining calcium homeostasis

BUT…

UV radiation also damages DNA and destroys folate (which is necessary for successful reproduction)
Melanin production helps mitigate this damage by absorbing harmful UV radiation
Sunlight: friend and foe
Capillaries and Skin Color
Oxygenated red blood contributes to skin color:
Blood vessels dilate from heat, skin reddens, heat is lost
Blood flow decreases, skin pales, heat is conserved
This is why fair-skinned people appear red during exercise or hot weather
Cyanosis:
Bluish skin tint
Caused by severe reduction in blood flow or oxygenation
Skin Color
Stratum Granulosum
The “grainy layer”
Stops dividing, starts producing keratin
Extremely durable, water-resistant, outer surface of skin, but also nails horns and hair
Stratum Lucidum
The “clear layer”:
Found only in thick skin
Covers stratum granulosum
Densely packed cells filled with keratin
Intermediate Strata
Structure of the Epidermis
Uncommon, often aggressively malignant
Common, usually benign
Types of Skin Cancer
Dermis and Hypodermis
General Structure of the Integumentary System
The subcutaneous layer or hypodermis
Lies below the integument
Stabilizes the skin
Allows separate movement
Is made of elastic loose connective tissue and adipose tissues
Is connected to the reticular layer of integument by connective tissue fibers
Has few capillaries and no vital organs
Is the site of subcutaneous injections using hypodermic needles
Deposits of subcutaneous fat
Have distribution patterns determined by hormones
Are reduced by cosmetic liposuction (lipoplasty)
The Hypodermis
The Papillary Layer (tiny mounds)
Contains smaller capillaries, lymphatics, and sensory neurons
Has dermal papillae projecting between epidermal ridges (underlying the epidermal ridges)
The Reticular Layer (having the form of a net)
Consists of dense irregular connective tissue
Contains larger blood vessels, lymph vessels, and nerve fibers
Contains collagen and elastic fibers
Contains connective tissue proper
The Dermis
The Dermis
Is located between epidermis and subcutaneous layer
Anchors epidermal accessory structures (hair follicles, sweat glands):
Has two components
Outer papillary layer
Deep reticular layer
The Dermis
Accessory Structures
Nails protect fingers and toes
Made of dead cells packed with keratin
Metabolic disorders can change nail structure
Nail growth
Occurs in a deep epidermal fold near the bone called the nail root
Nails
Sweat Glands
Sebaceous Glands and Sebaceous Follicles
Sebaceous (Oil) Glands
Simple branched alveolar glands:
Associated with hair follicles
Sebaceous follicles:
Discharge directly onto skin surface
Sebum:
contains lipids and other ingredients
lubricates and protects the epidermis
inhibits bacteria
Sebaceous Glands and Sweat Glands
Exocrine (secrete to the exterior)
Sweat Glands
Two types: apocrine glands and merocrine glands
Apocrine (armpits) secretions are decomposed by bacteria producing odor
Merocrine (all over the body) secretions not broken down by bacteria
Exocrine Glands in Skin
Exocrine (secrete to the exterior)
Sebaceous Glands (Oil Glands)
Holocrine glands (releasing a secretion that is a product of disintegrating cells.)
Secrete sebum
Lubricates hair and skin and inhibits growth of bacteria
Exocrine Glands in Skin
Hair Color
Produced by melanocytes at the hair papilla
Determined by genes
Arrector Pilli Muscle
Muscle which extends from the pappilary dermis to each hair follicle, forcing hair to stand up (goosebumps)
Hair
Hair is formed by the repeated divisions of epithelial stem cells surrounding the papilla
As cells divide they become keratinized and are pushed to the surface forming hair
Halfway to surface of skin the hair root becomes the hair shaft
Hair
Hair, hair follicles, sebaceous glands, sweat glands, and nails
Are integumentary accessory structures
Are located in dermis
Project through the skin surface
Accesory Structures
The Structure of a Nail
Merocrine Sweat Glands
Widely distributed on body surface
Especially on palms and soles
Discharge directly onto skin surface
Sensible perspiration
Water, salts, and organic compounds
Functions of merocrine sweat gland activity:
Cools skin
Excretes water and electrolytes
Flushes microorganisms and harmful chemicals from skin
Sweat Glands
Apocrine sweat glands
Found in armpits, around nipples, and groin
Secrete products into hair follicles
Produce sticky, cloudy secretions
Break down and cause odors
Surrounded by myoepithelial cells:
Squeeze apocrine gland secretions onto skin surface
In response to hormonal or nervous signal
Sweat Glands
Protect the scalp from UV light
Provide light cushioning for head
Hair guarding entrance to nostrils and ear canals prevent entry of foreign objects
Eyelashes protect eye
Hair connected to nerves aids in sensory perception
Functions of Hair
Hair Follicles and Hairs
Hair follicles project deep into the dermis
The walls of each follicle contain all the layers found in the epidermis (GSGLC)

The epithelium at the base of a follicle forms a cap over the hair papilla
A peg of connective tissue containing capillaries and nerves
The human body is covered with hair, except
Palms
Soles
Lips
Portions of external genitalia
Functions of Hair
Protects and insulates
Guards openings against particles and insects
Is sensitive to very light touch
Hair
Repair
Repair of Skin Injuries
Step 4
After several weeks the scab is shed
Epidermis is complete
Injury site marked by a shallow depression
Fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis
Repair of Skin Injuries
Step 3
One week after injury, scab is undermined by epidermal cells migrating over the meshwork produced by fibroblast activity
(Fibroblast – a cell that produces fibrous connective tissue like collagen etc)
Phagocytic activity is over and the fibrin clot disintegrates
Repair of Skin Injuries
Repair of Skin Injuries
Step 2
After several hours, a scab forms.
Cells of the stratum germinativum migrate along the edges of the wound.
Phagocytic cells (macrophages) remove debris ( Phagia- eat )
Clotting (fibrin) around the edges of the wound partially isolate the region.
The combination of blood clot, fibroblasts, and extensive capillary network is called granulation tissue.
Repair of Skin Injuries
Step 1
Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.
Mast cells: a large granular cell, common in connective tissue, that produces heparin, histamine, and serotonin.
Repair of Skin Injuries
Skin can regenerate effectively even after considerable damage because stem cells are present in both the epithelium and connective tissue layers
Repair of Skin Injuries
Where do the RACES come from?
The Biology of skin color

http://www.pbs.org/wgbh/evolution/library/07/3/text_pop/l_073_04.html
The Science of Race:
"A tale of two "vitamins"
Decubitus Ulcers
Pressure or bedsore

Usually found on pressure points such as: sacrum, coccyx, heels or the hips, elbows, knees, ankles or the back of the cranium

The cause of pressure ulcers is pressure applied to soft tissue so that blood flow to the soft tissue is completely or partially obstructed.
Decubitus Ulcers
Sebaceous Cysts
Blocked sebaceous glands, swollen hair follicles and excessive testosterone production will cause such cysts.

They are generally mobile masses that can consist of:
Fibrous tissues and fluids, a fatty (keratinous) substance that resembles cottage cheese, in which case the cyst may be called "keratin cyst"

This material has a characteristic "cheesy" or "foot odor" smell, a somewhat viscous, serosanguineous fluid (containing purulaent and bloody material).
Sebaceous Cysts
Warning!
Disgusting!
Integumentary Accessory Structures gone WILD!
Vitamin D and Folic acid (folate)
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