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INTEGUMENT DERIVATIVES Integument - skin and
certain specialized derivatives nails, hair and
several kinds of glands
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SKIN external covering of body 0.5 to 5.0 mm.
thick Epithelium epidermis dermis (corium)
dense bed of vascular connective tissue
lamina propria of a mucous membrane subcutaneous
layer deeper, looser, fibrous superficial
fascia submucosa of a mucous membrane boundary
epidermis and corium - uneven, abrupt even,
smooth junction forehead, ear and scrotum
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free surface furrowed form small rhomboidal or
rectangular areas palmar and plantar surfaces
parallel ridges (cristae) and furrows (sulci)
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EPIDERMIS stratified squamous epithelium 0.1
mm. thick Palm and sole 0.8 and 1.4 mm. thick,
respectively superficial layers cornified
Palmar and plantar surfaces. Maximum
layering and cellular differentiation (1)
germinative (2) granular (3) lucid (4)
horny
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Stratum Germinativum - Malpighian layer basal
cells are columnar elements stratum basale
Next higher - prickle cells of the stratified
stratum spinosum intercellular bridges
desmosome tonofibrils pass into the bridges
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Stratum Granulosum cells somewhat flattened
thick epidermis - palm or sole - 3 to 5 cells
deep Elsewhere layer is thinner or lacking
cells are diamond-shaped nucleus pale and
indistinct degenerative changes cytoplasm
(some mammals) - irregular-shaped granules
(keratohyalin)
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Stratum Lucidum clear, translucent layer 3 to
5 cells deep only in especially thick epidermis
(palm sole) flattened, dying cells
homogeneous, glassy plate nuclei indistinct
or invisible cytoplasm - semifluid substance,
eleidin
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Stratum Corneum Layer of cornified cells
progressively flattened and fused each
retains its cell membrane Cytoplasm replaced -
material is dry, shiny and highly refractile -
keratin
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Stratum corneum
Stratum lucidum
Stratum spinosum
Stratum germinativum
Stratum basale
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Regional Differences Palm, Sole all layers
present General body thinner, simpler Germinativ
e layer, horny layer constant Lucid layer
usually not present Junctional regions lip,
nostril, anus, vulva Transition to mucous
membrane Epithelium thick/moistened
(mucous) S. corneum thin blood shows through
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Pigmentation Skin basic color yellow
(carotene) Blood adds reddish tint Melanin
granules ? adds brown In basal
cells Disappears as cells move to surface (S.
corneum) Melanin derived from
tyrosine Enzyme tyrosinase White/light
skin pigment basal cells only except areola,
circumanal more pigment moles localized
heavily pigmented areas Dark skinned pigment
extends into S. granulosum
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Pigmentation Pigment produced in melanoblasts
(neural crest derivatives) Neural crest cells
migrate into basal layer Synthesize melanin
transfer pigment to germinative cells
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melanin
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DERMIS (CORIUM) Thickness 0.3 to 4 mm. Thin
epidermis backed by either thin (eyelid) or thick
dermis (back) 2 Strata Papillary Reticular
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Papillary Layer of Dermis Ridges Papillae
protrude into epidermis Up to 65,000 / square
inch Papillae tall palm sole (50 -
200µ) Double row Often branched Papillae
tall lips, penis, nipple Papillae
mechanically advantageous Low demand papillae
low, few, and irregular Two types of papillae
tactile (with tactile sensory corpuscle, e.g.
Meissners Corpuscle) vascular Tissue of
papillae interwoven mesh thin collagenous
fibers elastic fibers
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Reticular Layer of Dermis main fibrous bed of
dermis Coarse, densely interlacing
fibers Fiber direction parallel to
surface Elastic networks mingle with
collagenous fiber bundles Pigmented C.T.
cells (chromophores) possible If present
usually superficial More abundant in people
with darker skin Ingest store pigment, NO
synthesis True melanoblast (dopa positive)
occur locally Produce Mongolian spot (sacral
region) certain tumors (blue naevi)
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Hairs, sweat glands, sebaceous glands, lamellar
corpuscles when present Smooth muscle fibers in
dermis perineum, scrotum, penis, nipple
(dartos reflex of scrotum nipple
erection) Small bundles arrector muscles of
hair follicle Face neck skeletal muscle
fibers terminate in dermis Skin
movement Better developed in lower mammals
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Subcutaneous Layer superficial fascia of
body NOT PART OF SKIN blends with
dermis Looser network of C.T. bands
septa Skin mobility related to density
arrangement of this layer Spaces in
subcutaneous layer occupied by fat lobules If
abundant panniculus adiposus Panniculus of
abdomen 1 inch or more Fat never occurs
eyelids, scrotum, penis
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Skin Derivatives Nails Hair Cutaneous Glands
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The Nails Humans primates (claws in other
forms) Convex, rectangular structure Components
Nail plate (horny) Nail bed (less
modified) Nail plate in nail groove (formed by
skin) Nail plate free edge a body (exposed
above, attached below) root (covered above,
attached below)
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Junction of body root Whitish zone
lunule Concealed by fold of skin, except on
thumb Similar fold forms wall of nail
groove Nail wall overlaps nail
plate Laterally groove is shallow Proximall
y a deep pocket Nail bed under nail
plate Consists of germinative layer of
epidermis and underlying dermis
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HAIR Tapering, horny thread (Mammals
only) length 1 mm. to 5 feet thickness 0.005
mm. (lanugo) to 0.2 mm. (beard) Humans hair
covers entire body except palm, sole, region of
anal urogenital apertures Frequency 1300 /
sq. inch (vertex) 140 / sq. inch (chin) Hairs
enter skin at an angle (not perpendicular) Hair
root enclosed by tubular hair follicle Follicle
part epidermal part dermal Associated
structures sebaceous glands arrector
muscles Curly hair flatter than straight hair
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STRUCTURE OF SHAFT AND ROOT Epidermal cells
arranged in three concentric, cylindrical layers
Medulla, Cortex, Cuticle Medulla a looser
central axis two or three cells thick Hairs
of the axilla, beard and eyebrows contain a
medulla Hairs of the head may or may not
possess this core Cells shrunken, cornified
cuboidal Cells partly separated by air spaces
Contain refractile droplets and, often,
pigment Keratin of medullary cells is of the
'soft' type
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Cortex - main bulk of a hair Compact and
longitudinally striate Long, flattened,
spindle-shaped, cornified, acidophilic cells
Pigment, in solution and as granules, occurs in
and between cells Black hair much pigment
well-oxidized tyrosin Red hair pigment product
of limited oxidation Air vacuolesbetween cells
can modify hair color
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Cuticle Superficially a very thin, single
layer of cells Cornified scales that have lost
nuclei scales overlap, like shingles free
edges directed upward Keratin of the cortex and
cuticle is of the 'hard' type Compacted cells
do not desquarnate
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STRUCTURE OF FOLLICLE A hair follicle consists
of a compound sheath Externally there is a
dermal root sheath Internally, an epidermal
root sheath Deep end follicle expands into a
hair bulb
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Dermal Root Sheath Fibrous sheath only around
the lower two-thirds of follicle Represented
best in coarse hairs (scalp) Three layers,
corresponding to strata of the corium. Oute
r, Middle, and Inner Layers
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OUTER LAYER A poorly defined layer of
longitudinally directed fibers. Corresponds to
deep (reticular) layer of dermis. MIDDLE
LAYER Thicker, more cellular, denser layer of
circular, fine fibers. Corresponds to the
papillary layer of the dermis The hair
papilla is like an ordinary dermal papilla,
but far larger. Contains capillaries, nerve
fibers and, sometimes, pigment cells.
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INNER LAYER Most internally, next to the
follicle, there is a homogeneous glassy
membrane. Corresponds to the basement membrane
Consists of reticular fibers and amorphous
ground substance.
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Epidermal Root Sheath An outer and an inner
epidermal sheath, each with subordinate
strata The outer sheath corresponds to the less
modified, deep epidermal layers The inner
sheath corresponds to the more specialized,
superficial layers.
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OUTER ROOT SHEATH Above the outlet of the
sebaceous gland, ordinary epidermis lines
follicle Below this level the germinative layer
alone continues as the outer sheath Thins as
it approaches the bulb Sheath has its two
subordinate layers arranged as in the
epidermis. COLUMNAR LAYER. single layer of
taller cells, next to the glassy
membrane PRICKLE-CELL LAYER. Several layers of
cells, with intercellular bridges.
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INNER ROOT SHEATH Constitutes a keratinized,
cellular sheath enveloping the growing
root Pushed up by additions from the
bulb Gives out before reaching the
sebaceous-gland Elaborates 'soft keratin, with
a keratohyalin stage, like epidermis Nuclei
and discernible cells occur only at the deeper
levels of the sheath Three layers like
specialized epidermal strata. Corresponding
strata of the epidermis are granular, lucid
and cornified.
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HENLE"S LAYER Outer, single layer of elongate,
low cells Clear cells containing hyaline
fibrils at the deeper follicular
levels HUXLEY'S LAYER Consists of several
layers of transparent, precornified
cells Contain acidophilic trichohyalin
granules, much like epidermal
eleidin CUTICLE This is a single layer of
thin, transparent, horny scales. The cells
overlap like shingles, with their free edges
directed downward. Interlocking with similar
cells of the hair cuticle explains why the inner
root sheath is also removed when a hair is
extracted.
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CUTICLE Single layer of thin, transparent,
horny scales Cells overlap like shingles, with
their free edges directed downward Interlock
with similar cells of the hair cuticle
Explains why the inner root sheath is
removed when a hair is extracted.
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ASSOCIATED MUSCLE AND GLANDS Arrector muscle of
a hair is a characteristic accessory A band of
smooth muscle, 0.05 to 0.2 mm. wide Large hairs
have thick bands, but there are exceptions
(axilla beard) Some hairs lack an erector
muscle (eyelashes nasal hairs) A muscle
arises high in the dermis and, for a distance,
is a single bundle
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Arrector Pili Muscle then subdivides, each
division passing to a hair of a hair
group Such a terminal bundle usually joins the
follicle below the sebaceous gland The
muscle may be perforated by a large, branched
gland The muscle inserts on the dermal root
sheath, slightly above its mid-level
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Sebaceous Glands One to several sebaceous
glands always connect with a hair No direct
correlation between the sizes of the hair or
gland Some of the smallest hairs have the
largest glands A gland usually is located
in the angle between the follicle and its
muscle Its short duct empties into the
follicle at a level three-fourths of the way
up.
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Holocrine glands in which secretory cells are
lost along with the secretion Most occur in
company with a hair Usually several glands
drain into a hair follicle hence the total
number is large. Glands independent of hairs
occur in a few locations Duct then opens onto
the free surface of the skin Example
margin of lips glans penis inner
surface of prepuce labia minora nipple
tarsal (Meibomian) glands of eyelids. Entirely
lacking from the palm and sole.
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Dermal sheath
Hair, root
Hair, epidermal sheath
Glassy membrane
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Polyhedral cells
Henles layer
Huxleys layer
Tall cells
Cuticle
Connective tissue layers
shaft of hair
Glassy or Vitreous Membrane/layer
Cortex
Medulla
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