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Objectives
To explain the function of the integumentary system.
To identify the components of the epidermis.
To list the strata of the epidermis.
Definitions
Epi – upon, on top of Hypo – under Derm – skin Serous membrane – membranes that
line the body cavities Mucous membrane – membranes that
open to the outside of the body Synovial membrane – Membranes in
our joints
The Integumentary System: An Overview
Introduction
Organs are body structures composed of two or more different tissues.
The skin and its accessory organs make up the integumentary system
Parts of the integumentary system Skin – largest organ in our body Body membranes Hair Nails
Functions:
Protective covering Helps regulate body temperature
(homeostasis) Prevents water loss from deeper
tissues Houses sensory receptors Synthesizes biochemicals Excretes small quantities of waste
Consists of…
Cutaneous membraneEpidermis – Outermost layerDermis – Middle layer
Accessory structures- hair, sweat glands, sebaceous glands etc.
Subcutaneous layer (hypodermis) – innermost layer
Components
Figure 5.1
Cutaneous Membrane Cutaneous membrane is another word for
skin.Dry membrane
Act as protective covering from….Mechanical damage (bumps)Chemical damage (acids and bases)Bacterial damageUV radiationThermal damageDesiccation (drying out)
Cutaneous Membrane
Regulate body temperature Prevent water loss House sensory receptors
Send signals to your brain about what you can feel
Synthesize various biochemicalsLike Vitamin D
3 Layers of Cutaneous Membrane
Epidermis:Structure: Top layer; stratified squamous tissueFunction: protection
Dermis:Structure: middle layer, largest layer. Hair, sweat
glands, nails, oil glands
Hypodermis:Structure: Bottom layer. Loose connective tissue
and adipose tissue.Function: Insulation, houses major blood vessels.
The Epidermis
Thin Skin and Thick Skin The epidermis is composed of layers of
keratinocytes- cells that produce keratinThin skin = four layers (strata)Thick skin = five layers
Figure 5.2
The Epidermis Composed of stratified squamous epithelium Lacks blood vessels Older cells are pushed to the top and harden in
a process called keratinization.
Layers of the epidermis:
Stratum basale/ germinativum (cells undergoing mitosis)
Stratum spinosum Stratum granulosum Stratum lucidum (only occurs in thick, hairless
skin of palms and hands and soles of feet) Stratum corneum (cells filled with keratin to
protect and prevent water loss from skin)
From deep…….
…… to superficial
The Structure of the Epidermis
Figure 5.4
Epidermis Cell Layers Germinative
Basal cells (stem) are reproducing Spinosum- spiny layer Granulosum- grainy layer
Stops dividing, start producing keratin Lucidum
The clear layer found only in thick skin Corneum
Exposed to surface and shed every 2 wks.
Skin color depends on… GeneticsDiffering amounts of melanin and size of melanin
granules
Blood supply Interrupted blood supply leads to cyanosis- blue!
CaroteneOrange-yellow pigment found in orange vegetables
MelaninYellow-brown pigmentProtects deeper cells from UV radiationProduced by melanocytes
Melanocytes
Figure 5.5a, b
Epidermal cells Synthesize vitamin D3 (cholecalciferol) when
exposed to UV
Aids in absorption of calcium and phosphorus- needed for bone strength
Respond to epidermal growth factorGrowthDivisionRepairSecretion
Objectives
The explain the components of the dermis.
To understand why tattoos are permanent.
To identify accessory organs of the integument and explain their function.
The Dermis
Dermal Organization Located between epidermis and subcutaneous
layer Consists of connective tissue with collagen and
elastic fibers within a gel-like substance Anchors accessory structures- hair follicles,
sweat glands, blood vessels etc. Carry nutrients to upper layers of skin and
help regulate temperature. Two components:
Outer papillary layerDeep reticular layer
Layers of the Dermis
Papillary layerAreolar tissueContains blood vessels, lymphatics, sensory
nerves of epidermis
Reticular layerDense irregular connetive tissueContains network of collagen and elastic
fibers to resist tension
Stretch Marks
Caused by excessive stretching of the dermis
Patterns of collagen and elastic fibers form lines of cleavage
Lines of Cleavage of the Skin
Figure 5.7
Hypodermis (subcutaneous)
Elastic areolar tissue and adipose tissue Stabilizes skins position against
underlying organs and tissues Shock absorber and insulator Few capillaries and no vital organs Subcutaneous injection is useful to
administer drugs
Structures Hair papilla
Connective tissue containing capillaries and nerves
RootAnchors hair into skin
ShaftPart we see on the surfaceConsists of three layers
○ Cuticle- overlapping shingle layer○ Cortex- underlying layer- pigments○ Medulla- core of hair
Structures Contd. Sebaceous Glands
Also called holocrine glandsAssociated with hair folliclesDischarge oily substance into hair follicles
(waterproofs and moisturizes the hair shafts)Inhibits growth of bacteriaActivated at puberty
Arrector pili musclePulls on follicle, forcing the hair to stand upCold or emotional states- goosebumps
Anatomy of a Single Hair
Figure 5.9
Hair Follicles and Hair
Hair Follicles
Figure 5.10a-c
Hair
Hairs
Individual hairs develop from cells at the base of the hair follicle, an invagination of the lower epidermis that dips down into the dermis.
As new cells are formed, old cells are pushed outward and become keratinized, forming the hair shaft.
Project deep into the dermis and often into the hypodermis
Hair Color
Melanin produced by melanocytes at the hair papilla
Red hair also contains the pigment trichosiderin
Determined by genetics
Function of Hair Head
Protection from UV lightCushion a light blow to headInsulation
Nostrils, ears, and eyesPrevent entry of particles
SensorySensory nerve fiber at base of every hair
Appendages of the Skin
Appendages of the Skin
Exocrine Glands- Reach Outside
Sebaceous glands (Oil glands)Associated with hairSecrete sebum, which lubricates and
inhibits bacteria growthAcne- condition when they are clogged
Sweat glands (Watery Glands)2 kinds
○ Eccrine: all over the body ○ Apocrine: armpits and groin (hormonal)
Sweat Glands Eccrine – respond to body temperature;
open via duct to pore on skin surface Apocrine – responds to body temperature,
stress; ducts empty into hair follicles Ceruminous glands – modified sweat
glands that secrete wax in the ear canal Mammary glands – modified type of sweat
glands that secrete milk
Sebaceous Glands and Hair
Figure 5.11
Sweat Glands
Figure 5.12 Sweat Glands
Figure 5.12a, b
Sweat and Its Function Composition:
Mostly waterSalts and vitamin CSome metabolic wasteFatty acids and proteins (apocrine only)
Function:Helps dissipate excess heatExcretes waste productsAcidic nature inhibits bacteria growth
Odor is from associated bacteria
Regulation of body temperature Heat may be lost to surroundings from the
skin. Body responds to excessive heat by
dilation of dermal blood vessels and sweating.
Body responds to excessive cooling by constricting dermal blood vessels, inactivation sweat glands and shivering.
Nails
Keratinized cells that protects the tips of fingers and toes
Stratified squamous overlying the nail bedLunula is the most actively growing
region of the nail root
Structures Nail Body
Covers an area of the epidermis called the nail bed
Nail RootWhere nail production occursNot visible on surface
CuticlePortion of stratum corneum
Structure Contd.
LunulaPale crescent area near the root were
blood vessels are absent
Figure 5.13 The Structure of a Nail
Figure 5.13
Loss of Homeostasis in Skin
Skin Homeostatic Imablance Infections
Athlete’s foot (tinea pedis) – fungal infectionBoils and carbuncles – bacterial infectionCold sores – caused by virus
Skin Homeostatic Imbalance
Skin Homeostatic Imabalance Burns
Tissue damage and cell death caused by heat, electricity, radiation, or chemicals
Associated dangers○ Dehydration○ Electrolyte imbalance ○ Circulatory shock
Severity of Burns
First-degree burnsOnly epidermis is damagedSkin is red and swollen
Second-degree burnsEpidermis and upper dermis are damagedSkin is red with blisters
Third-degree burnsDestroys entire skin layerBurn is gray-white or black
Severity of Burns
Critical Burns
Burns are considered critical ifOver 25% of the body has second-degree
burnsOver 10% of the body has third-degree
burnsThere are third-degree burns on the face,
hands, or feet
Healing of Wounds Inflammation – blood vessels dilate and become more
permeableCauses tissues to become red and swollenThis is the body’s normal response to injury
Superficial cuts are filled in by reproducing epithelial cells
Deeper cuts are closed off by clots, covered by scabs and eventually filled in by fibroblasts, making connective tissue.
Blood vessels extend into the area, the injured tissues are replaced, and the scab falls off.
Large wounds leave scars and helping may be accompanied by the formation of granulations.
Skin Cancer
Cancer – unregulated mitotic cell division producing abnormal mass
Classified in two waysBenign – does not spreadMalignant – metastasized (moves) to
other parts of the body
Skin cancer is the most common type of cancer!!
Basal Cell Carcinoma
Least malignant Most common type Arises from stratum basale
Squamous Cell Carcinoma Metastasizes to lymph nodes if not removed
Early removal allows a good chance of cure
Believed to be sun-induced Arises from stratum spinosum
Malignant melanoma Most deadly of skin cancers Caner of melanocytes Metastasizes rapidly to lymph and
blood vessels Detection uses ABCD rule
ABCD rule
A = AsymmetryTwo sides of pigmented mole do not match
B = Border irregularityBorders of mole are not smooth
C = ColorDifferent colors in pigmented area
D = DiameterSpot is lager than 6 mm in diameter
The Skeletal System
• The Skeletal System provides structural support• The Integumentary System
synthesizes vitamin D3, essential for calcium and phosphorus absorption (bone maintenance and growth)
Copyright © 2010 Pearson Education, Inc.
The Muscular System
• The Muscular System’s facial muscles pull against skin of face, producing expressions important in communication
• The Integumentary System synthesizes vitamin D3 , essential for normal calcium absorption (calcium ions play an essential role in muscle contraction)
Copyright © 2010 Pearson Education, Inc.
The Nervous System
• The Nervous System controls blood flow and sweat gland activity for thermoregulation; stimulates contraction of arrector pili muscles to elevate hairs
• The Intergumentary System’s receptors in dermis and deep epidermis provide sensations of touch, pressure, vibration, temperature, and pain
Copyright © 2010 Pearson Education, Inc.
The Endocrine System
• The Endocrine System includes the sex hormones that stimulate sebaceous and apocrine gland activity, and develop secondary sexual characteristics; suprarenal hormones alter blood flow to skin and mobilize lipids from fat cells
• The Integumentary System synthesizes vitamin D3, precursor of calcitriol, a hormone produced by the kidneys
Copyright © 2010 Pearson Education, Inc.
The Cardiovascular System
• The Cardiovascular System provides oxygen and nutrients; delivers hormones and cells of immune system; carries away carbon dioxide, waste products, and toxins; provides heat to maintain normal skin temperature
• The Integumentary System’s mast cells produce localized changes in blood flow and capillary permeability
Copyright © 2010 Pearson Education, Inc.
The Lymphatic System
• The Lymphoid System assists in defending the integument by providing additional macrophages and mobilizing lymphocytes
• The Integumentary System provides physical barriers that prevent pathogen entry; macrophages resist infection; mast cells trigger inflammation and initiate the immune reponse
Copyright © 2010 Pearson Education, Inc.
The Respiratory System
• The Respiratory System provides oxygen and eliminates carbon dioxide
• The Integumentary System’s hairs guard entrance to nasal cavity
Copyright © 2010 Pearson Education, Inc.
The Digestive System
• The Digestive System Provides nutrients for all cells and lipids for storage by adipocytes
• The Integumentary System synthesizes vitamin D3, needed for absorption of calcium and phosphorus
Copyright © 2010 Pearson Education, Inc.
The Urinary System
• The Urinary System excretes waste products, maintains normal body fluid pH and ion composition
• The Integumentary System assists in elimination of water and solutes; keratinized epidermis limits fluid loss through skin
Copyright © 2010 Pearson Education, Inc.