Chapter 5

The Integumentary System

The Skin epithelial and

connective tissues working together for specific purposes

the largest organ of the body 1.5 - 2 square meters 4 - 5 kg

variable thickness: 1.5 mm to 4 mm

Skin Physiology - Many Functions regulation of body temperature – insulator,

radiator protection – a physical barrier and for water

conservation sensation - varied sensory nerve endings communication – to other humans by

signals/expressions and by touch excretion – in sweat = H2O, salts, small organic

compounds (a minor contribution to excretion) immunity – certain phagocytes in the epidermis

are important from the immune system for defense

the dermis is a significant blood reservoir synthesis of Vitamin D – for calcium absorption

The Structure of the Skin2 Principal portions

1. Epidermis - epithelium

2. Dermis – areolar and dense irregular fibrous connective tissue

Hypodermis “beneath the dermis” the subcutaneous

layer next to: adipose layer or muscle or bone

The Epidermis Stratified Squamous

Epithelium

4 cell types1. Keratinocytes - 90%

filled with keratin (protein) waterproof barrier

2. Melanocytes - 8% produce melanin (pigment) pass melanin to keratinocytes

3. Langerhans cells phagocytes (from immune

system) easily damaged by UV light

4. Merkel cells in deepest layer of hairless skin sensory transduction - touch

Stratum basale A single layer of

cuboidal/columnar cells Stem cells,

melanocytes, Merkel cells

Stem cells keratinocytes, mitosis pushes the other layers to the top

Stratum spinosum 8 to 10 layers of closely

packed cells Cell junctions - spot

desmosomes Langerhan’s cells

Epidermal Cell Layers

Stratum granulosum 3-5 layers of flattened, with

keratohyaline granules beginning breakdown of

nucleus, cell death initiated

Stratum lucidum only in thick skin (palms, feet) 3-5 layers of clear, flat dead

cells with keratin

Stratum corneum 20-30 layers of flattened,

dead, keratin-filled cells continuously shed and

replaced

2-4 weeks for each cell to form and to move from the stratum basale to the surface

Epidermal Cell Layers

Epidermal Histology

Stratum Corneum

Stratum Granulosum Stratum Spinosum

Stratum Basale

The Dermis - General primarily irregular dense fibrous conn.

tissue variable thickness - thicker on palms and

soles; thicker on dorsal surfaces rather than on ventral; thicker on lateral surfaces than on medial surfaces

few cells present - fibroblasts, macrophages, adipocytes

matrix thick with many protein fibers: collagen, elastin, reticular

the location for blood vessels, nerves and sensory receptors, glands, hair follicles

Dermis - Structure Papillary region

(layer) - outer layer - 20% areolar connective

tissue, elastic fibers

dermal papillae – mound-like projections to increase the surface area for nutrition from capillaries

some papillae contain Meissner's corpuscles (for light touch)

Dermis – Structure (cont.) Reticular region -

80% dense, irregular

connective tissue collagen, elastic

fibers in a network surrounding the various cells

fibers give strength, elasticity, extensibility

tears in reticular region - "stretch marks“ - long straight red or white streaks

Three Skin Pigments1.Melanin - yellow to black

Made by melanocytes

Common in mucous membranes, penis, nipples, areolas, face, extremities

The number of melanocytes is similar in all races – but the amount and type of melanin produced and distributed to the keratinocytes varies

Freckles, livers spots - melanocyte clusters

Melanin is synthesized from tyrosine (amino acid) UV radiation increases enzyme activity (negative feedback) melanin production protects the body against UV radiation

Melanin Pathologies Albinism - inability to produce melanin;

cannot breakdown tyrosine, no melanin, inborn error of metabolism; recessive trait

Vitiligo - partial/complete loss of melanocytes from skin patches

albinovitiligo

Three Skin Pigments

2. Carotene - yellow-orange pigment in the dermis

Gives egg yolks, carrots, their color Used in the synthesis of a vision pigment Persons of Asian extraction have carotene

in their stratum corneum, in the fatty areas of the dermis and in their subcutaneous layers

3. Hemoglobin – because the skin is translucent

Caucasian skin – tinted red to pink depending on dermal capillary blood flow

Three Skin Pigments

Skin Color Skin color

Blood is bright red when carrying oxygen, dark red/purple when deoxygenated; the skin appears to have a blue or green or purple tinge depending on the individual

The relative color of skin and exposed mucous membranes can give clues to a person’s oxygenation status

Skin Color – Clinical Terminology Erythema

skin redness exercise,

embarrassment, high blood pressure, certain drugs, inflammation, etc.

Pallor pale cold temperatures,

stress or anemia Cyanosis

bluish, no oxygen babies not breathing,

heavy smokers/emphysema

Pernicious anemia

Erythema: Parvovirus / “fifth disease”

Cyanosis

Skin Color – Clinical Terminology Jaundice

yellow/orange after internal

hemorrhage liver problems disturbing

the breakdown & removal of RBC's

Bronzing Metallic appearance of

skin Addisons disease –

hypofunction of adrenal cortex

Black and blue marks, bruises (contusions)

Skin Pathologies Basal cell carcinoma

From stratum basale Least malignant - 99% full cure

Squamous cell carcinoma From stratum spinosum Prognosis is good if removed

early

Melanoma Melanocyte cancer Highly metastatic Resistant to chemotherapy

ABCD Rule Asymmetry Border irregularity Color: several present Diameter: greater than 6 mm

Skin Grafts Sometimes when the is skin severely

damaged, it cannot regenerate itself Success is dependent on the site of

origin of the transplanted tissue autograftautograft

from the same persondonated from a different sitecan be tissue cultured first

isograftisograft - identical twins homografthomograft - skin from another human heterograftheterograft - skin from an animal

Autograft to knee

Epidermal Derivatives: Hair = Pili Hair functions

protection increase surface area for evaporative heat loss; increased length (scalp) for sunburn and heatstrokeeyebrows, eyelashes - insects, foreign particlesnostril hair – sameear hair - same

mechanical dry lubricant for limb movements secondary sexual characteristic to attract

mates touch receptors respond to changes in position rate of growth & replacement affected by many

things: heredity, diet, illness, fever, blood loss, surgery, drugs, chemotherapy

Hair Anatomy Shaft

medulla - inner layer cortex - middle layer, pigments, air

spaces cuticle - outermost layer, hard

keratin

Root similar to shaft, but within dermis

Follicle - surrounds root

Sheath - supports shaft & root

Bulb - enlarged layered structure at base where hair is generated papilla - areolar connective tissue,

blood vessels supply nutrients matrix - germination layer of papilla

(stratum basale) builds hair shaft

Sebaceous glands – release oil

Arrector Pili – smooth muscle

Hair Follicle

Hair Color Brown, black - melanin deposited from

the matrix of the bulb into the shaft

Red, blond - variants of melanin with iron, sulfur in the molecule

Grey – some loss of melanocytes reduces melanin deposition

White - air bubbles accumulate in the cortex

Hair and HormonesTestosterone Secretion increases

at puberty

Male pattern of hair growth and distribution begins

Hirsutism excess testosterone

production, tumor or hormonal imbalance

excess hair production in females or pre-pubertal males

Hair and Hormones Male pattern baldness

Genetic predisposition – sex-linked trait – testosterone inhibits scalp hair growth in these individuals

Finasteride (Propecia) - anti-testosterone agentmust be taken for remainder of life

Minoxidil (Rogaine)anti-hypertensive medicinewidens blood vessels, increases blood flow topically (daily) promotes growth in people with

reduced hair growth (not much but some); but not in truly bald individuals

Male Pattern Baldness

Skin GlandsSebaceous (Oil) Glands

Sudoriferous (Sweat) Glands

1. Sebaceous (Oil) Glands Connected to hair

follicles; located in the dermis

Most secrete directly into follicles; some directly onto the skin

Gland shape differs depending on location

Holocrine gland

Secrete sebum (oil) fats, cholesterol, proteins,

inorganic salts keeps hair from drying prevents water

evaporation from skin keeps skin soft, supple inhibits growth of many

bacteria

2. Sudoriferous (Sweat) Glands

Two types of typical glands1.eccrine sweat glands

the majority; especially abundant on the palms and soles and the forehead

the secretory portion of the gland is located in the dermis

Sudoriferous (Sweat) Glands

Two types of typical glands

2.apocrine sweat glands located mainly in the

axillary and anogenital regions, and the areolae of the breast

secretory portion is located in the dermis or the subcutaneous region; secrete into hair follicles

secrete more during emotional stress, sexual arousal

a merocrine processhttp://faculty.une.edu/com/abell/histo/histolab3g.htm

Modified Sudoriferous (Sweat) Glands

Two types of modified sweat glands

1.Ceruminous glands – protect against ectoparasites (bugs)

produce a bitter waxy secretion (cerumen) open into the external auditory meatus (ear

canal) or into local sebaceous glands

2.Mammary glands – highly specialized for milk production

hormonally regulated by estrogens, prolactin, and oxytocin

Sweat produced primarily by the eccrine

glands water, salts, urea, uric acid, amino

acids, ammonia, sugar lactic acid, ascorbic acid – a plasma filtrate

pheromones for sexual attraction pH between 4 and 6 salty and acidic solution inhibits most

bacterial growth maintain body temperature, but

insignificant for waste removal

CF = Cystic Fibrosis patients have an autosomal recessive inborn

error of metabolism altered chloride transport which alters the

characteristics of most glandular secretions detected in infants with a simple chloride sweat

test – CF babies have elevated sweat chloride values

primarily affects the respiratory and digestive systems with thick clogging secretions

average lifespan approximately 30 years ~1/3900 newborns ~3/100 adults are

carriers

Glands Pathology

Nails tightly packed, hard,

keratinized cells nail matrix - under

root of nail site of nail growth transforms normal

skin cells into nail cells which push forward

1mm/week in fingers; slower in toes

the longer the finger the greater the growth rate

Good Day!