LESSON 4 - INTERGUMENTARY SYSTEM

Integumentary System

consists of the skin and accessory structures, such as hair, glands, and nails.

Skin

Largest organ of the body

Integumentary System

consists of the skin and accessory structures, such as hair, glands, and nails.

Skin

Largest organ of the body

Epidermis

is the superficial layer of the skin.

Dermis

epidermis rests on it, a layer of connective tissue.

Structural Strength

Cleavage lines

2 Layers: Reticular & Papillary

Keratinocytes

most cells of the epidermis; they produce a protein mixture called keratin

Cornification

the process in which body tissues, such as nails, hair, and skin in humans, and horns in animals, become dry and hard.

Keratinization

as keratinocytes move from the deeper epidermal layers to the surface, the cells change shape and chemical composition.

Melanocytes

produce the pigment melanin, which contributes to skin color

Langerhans cells

part of the immune system;  Dendritic cell on the skin

Merkel cells

specialized epidermal cells associated with the nerve endings responsible for detecting light touch and superficial pressure; Mechanoreceptors cells for tough sensation

Stratum Basale

·       Stratum germinativum

·       Deepest portion of epidermis

·       Single layer of cuboidal or columnar cells

·       Produces cells of the most superficial strata

·       Active mitosis – undergo mitotic divisions approximately every 19 days

·       It takes approximately 40-56 days for the cell to reach the epidermal surface and slough off

Stratum Spinosum

·       Consisting of 8-10 layers of many-sided cells

·       Produces keratin fibers

·       Lamellar bodies form inside keratinocytes

Stratum Granulosum

·       2-5 layers of flattened diamond-shaped cells

·       Produces keratohyalin granules

·       Lamellar bodies release lipids from cells

·       Cells die

Stratum Lucidum

·       3-5 layers of dead cells

·       Appears transparent

·       Present in thick skin

·       Absent in most thin skin

Stratum Corneum

·       Most superficial

·       25 or more layers of dead squamous cells

·       Consists of cornified cells – dead keratinocytes, with a hard protein envelope, filled with the protein keratin.

·       Provide structural strength – keratin within cells

·       Prevents water loss – intercellular lipids

·       Resists abrasion

Stratum Disjunctum

·Sloughed off from day to day during rubbing

Stratum Compactum

superficial layer of stratum corneum

Thick Skin

·       Has all 5 epithelial strata

·       Found in areas subject to pressure or friction

o   Palms of hands, fingertips, soles of feet

Thin Skin

·       More flexible than thick skin

·       Covers rest of the body

Callus

forms when the stratum corneum of the epidermis increases in thickness

Corn

skin over bony prominences develop a cone-shaped structure

Melanin

the group of pigments primarily responsible for skin, hair, and eye color.

Melanosomes

Melanocytes produce and package melanin into vesicles called

Albinism

absence of melanin

Carotene

a yellow pigment found in plants, such as carrots and corn.

Cyanosis

blue color caused by decreased in blood oxygen content

Papillary layer (Dermal Papillae)

·       Loose connective tissue within thin fibers

·       Contains blood vessels

·       Superficial layer

Friction Ridges

ridges shape the overlying epidermis into patterns

Reticular layer

·       Main layer of the dermis composed of dense irregular connective tissue

·       Deeper layer

Cleavage or Tension Lines

·       Elastin and collagen fibers oriented in some directions more than others

·       Important in surgery

o   If incision is parallel to lines there is less gaping, faster healing, less scar tissue

Stretch marks

if the skin is overstretched, the dermis may rupture and leave lines that are visible through the epidermis.

Hypodermis (Subcutaneous Tissue)

connects the skin to underlying muscle or bone.

Intradermal injection

used for the tuberculin skin test, goes into the dermis.

Subcutaneous injection

extends into the subcutaneous tissue

Intramuscular injection

 reaches a muscle deep to the subcutaneous tissue.

Hair

·       Found everywhere on human body except palms, soles, lips, nipples, parts of external genitalia, and distal segments of finger and toes.

·       Act as sense organs

·       Protection, regulation of body temperature, and facilitation of evaporation of perspiration

Lanugo

delicate, unpigmented hair developed and covered the fetus, prior to birth

Terminal Hairs

replace the lanugo of the scalp, eyelids, and eyebrows

Vellus Hairs

short, fine, and usually unpigmented, replace the lanugo on the rest of the body; time of birth changes the lanugo

Medulla

central axis of the hair, and it consists of two or three layers of cells containing soft keratin.

Cortex

surrounds the medulla and forms the bulk of the hair

Cuticle

a single layer of cells also containing hard keratin, covering the cortex.

Dermal Root Sheath

portion of the dermis that surrounds the epithelial root sheath

External ERS

has all the strata found in thin skin

Internal ERS

raised edges that mesh closely with the raised edges of the hair cuticle and this arrangement holds the hair in place.

Hair bulb

expanded knob at the base of the hair root.

Matrix

inside the hair bulb that is a mass of undifferentiated epithelial cells.

Hair papilla

the dermis of the skin projects into the hair bulb as

Hair shaft

 the visible part of the hair that sticks out of the skin

Round shaft

straight hair

Oval Shaft

Wavy hair

Flat Shaft

Curly hair

Anagen (growth)

·       Hair increases in length as new matrix cells are produced, differentiate, become keratinized, and die.

·       Hair grows longer as cells are added at the base of the hair root.

Catagen (growth stops)

·       Hair growth stops: the hair follicle shortens and holds the hair in place

Telogen (rest)

·       Resting stage

Arrector pili

smooth muscle cells associated with each hair follicle.

Sebaceous Glands

·       Located in the dermis

·       Holocrine gland

·       Simple or compound alveolar glands that produce sebum

Sebum

oily, white substance rich in lipids

Eccrine Glands (Merocrine gland)  

o   Common type of sweat gland

o   Sweat pores

o   Found in palms, soles of the feet

Sweat

resulting hypoosmotic fluid that leaves the duct

Apocrine Glands

o   Found in the axillae and genitalia (scrotum and labia majora) and around the anus

o   Do not help regulate temperature in humans

o   Active at puberty

o   Body odor

o   May signal sexual maturity

Ceruminous Glands

·       Modified eccrine sweat glands

·       Located in the external auditory canal

·       Produce cerumen or ear wax

·       Helps trap foreign particles from reaching the eardrum

Mammary glands

·       Modified apocrine sweat glands

·       Located in the breasts

Nails

·       Thin plate

·       Consists of dead stratum corneum cells that contain a very hard type of keratin

·       Located on the distal ends of the fingers and toes

Nail Root

covered by the skin

Nail body

visible portion of the skin

Nail fold

lateral and proximal edges of the nail

Nail groove

edges

Cuticle (Eponychium)

stratum corneum of the nail fold grows onto the nail body

Hyponychium

beneath the free edge of the nail body

Nail matrix

distal extension of nail root

Nail bed

located between the nail matrix and the hyponychium

Lunula

small part of the nail matrix; whitish crescent shaped area

Burns

·       Injury to a tissue cause by heat, cold, friction, chemicals, electricity, or radiation

First-degree burns

·       Partial thickness burns

·       Involve only the epidermis

·       May result in redness, pain, and slight edema (swelling)

Second-degree burns

·       Partial thickness burns

·       Damage the epidermis and dermis

·       Minimal dermal damage causes redess, pain, edema, and blisters

·       Healing takes approximately 2 weeks

·       No scarring Results

Third-degree burns

·       Full-thickness burns

·       Epidermis and dermis are completely destroyed

·       Deeper tissue may be involved

Birth Mark

·       Congenital disorders of the dermal capillaries

Ringworm (Tinea)

·       Fungal infection that produces patchy scaling and inflammatory response in the skin

Tinea corporis

ringworm on the skin

Tinea capitis

ringworm in scalp

Tinea pedis (athlete’s foot)

ringworm in feet

Tinea cruris (jock itch)

ringworm in groin

Dermatitis & Eczema

·       Inflammatory conditions of the skin

·       Red and itchy

·       Causes

o   Allergy

o   Infection

o   Poor circulation, or

o   Exposure to chemical or environmental factors

Psoriasis

·       Chronic skin disease

·       Thicker than normal epidermal layer

·       Sloughs to produce large & silvery scales

·       Bleeding may occur if the scales are scraped away

Vitiligo

·       Development of patches of white skin

·       Melanocytes are destroyed

·       By an autoimmune response

Impetigo

·       Small blisters containing pus

·       Organisms: staphylococcus aureus or streptococcus pyogenes

·       Usually affects children

Erysipelas

·       Swollen patches

·       Organism: Streptococcus pyogenes

Decubitus ulcers

·       Bedsores/ Pressure sores

·       Develop in people are bedridden or confined to a wheelchair

·       Compression of tissue

·       Reduced circulation

·       Result in destruction of the skin & subcutaneous tissue – later become infected by bacteria, forming ulcers

Acne

·       Disorder of sebaceous glands & hair follicles

·       Occurs when sloughed cells block the hair follicle

·       Affected by:

o   Hormones

o   Sebum

o   Abnormal keratinization within hair follicles

o   Bacterium – Propionibacterium acnes

Rubeola (measles)

·       Measles morbillivirus

·       Infects the respiratory system

·       May develop into pneumonia or infect the brain – severe and can be life threatening

·       Red or reddish-brown rash

Rubella (German measles)

·       Rubella virus

·       Usually, mild viral diseases contracted through the respiratory tract

·       May be dangerous if contracted during pregnancy because the virus can cross the placenta and damage the fetus

Chicken pox

·       Skin lesions

·       Virus: Varicella-Zoster Virus

·       Usually mild viral disease contracted through the respiratory tract

Shingles

·       Painful skin lesions

·       Caused by the chicken pox virus after childhood infection

·       Recur when the dormant virus is activated by trauma, stress, or another illness

Cold sores (fever blisters)

·       Skin lesions

·       Caused by Herpes Simplex I Virus

·       Transmitted by oral or respiratory routes

Genital herpes

·       Genital lesions

·       Caused by Herpes Simplex II Virus

·       Transmitted by sexual contact

Skin Cancers

·       Result usually from damage caused by UV radiation in sunlight

Basal cell carcinoma

·       Most Common type

·       Affects cells in the stratum basale

Squamous cell carcinoma

·       Second most common type of skin cancer

·       Affects cells in the stratum spinosum

·       Can appear as a wart like growth

Melanoma

·       Least common

·       Most deadly

·       Stops producing melanin and appears skin-colored, pink, red, or purple

·       Detected by routine examination of the skin and application of the ABCDE rule