chapter 5 the integumentary system j.f. thompson, ph.d. & j.r. schiller, ph.d. & g. pitts,...
TRANSCRIPT
Chapter 5
The Integumentary System
J.F. Thompson, Ph.D. & J.R. Schiller, Ph.D. & G. Pitts, Ph.D.
The Skin - General 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 Architecture 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 Pigments - Melanin1. 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
Skin Pigments – 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
3 Skin Pigments - Carotene & HgB2. 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
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
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 depositedinto the shaft
Red, blond – variantsof 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
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
Sudoriferous (Sweat) Glands Sweat: a plasma filtrate
consisting of water, salts, urea, uric acid, amino acids, ammonia, sugar, lactic acid, ascorbic acid, and 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
Two types (a merocrine process):
1. Eccrine sweat glands
2. Apocrine sweat glands
Eccrine Sweat Glands Most abundant (3-4
million), especially on the palms and soles and the forehead
Lifetime performance influenced by environmental experience in infancy
Secretory portion located in the dermis
Apocrine Sweat Glands Less abundant,
merocrine glands confined mostly to 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 or sexual arousal http://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 antibacterial secretion (cerumen)
open into the external auditory meatus (ear canal) or into local sebaceous glands
Modified Sudoriferous (Sweat) GlandsTwo types of modified sweat glands
2. Mammary glands – highly specialized for milk production hormonally regulated by estrogens,
prolactin, and oxytocin
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
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
Nails Tightly packed cells
with hard keratin
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
End Chapter 5
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