Transcript Chapter 05 - Skin - Anatomy and Physiology

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 Skin
2 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 types
1. 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
Epidermal Cell Layers
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 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 - Melanin
1. 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
albino
vitiligo
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
3 Skin Pigments - Carotene & HgB
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
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
Erythema: Parvovirus /
“fifth disease”
Cyanosis
bluish, no oxygen
babies not breathing,
heavy
smokers/emphysema
Pernicious anemia
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
autograft
 from
the same person
 donated from a different site
 can be tissue cultured first
Autograft to knee
isograft - identical twins
homograft - skin from another human
heterograft - skin from an animal
Epidermal Derivatives: Hair = Pili
Hair functions
protection
 increase
surface area for evaporative heat loss;
 increased length (scalp) for sunburn and heatstroke
 eyebrows, eyelashes - insects, foreign particles
 nostril hair – same
 ear 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
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 Hormones
Testosterone
 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 prepubertal males
Hair and Hormones
Male pattern baldness
Genetic predisposition – sex-linked trait –
testosterone inhibits scalp hair growth in these
individuals
Finasteride (Propecia) - anti-testosterone agent
 must
be taken for remainder of life
Minoxidil (Rogaine)
 anti-hypertensive
medicine
 widens 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) Glands
Two 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