INTEGUMENTARY SYSTEM HUMAN ANATOMY AND PHYSIOLOGY   SUMMER, 2002

 

MAJOR COMPONENTS: skin, skin derivatives; specialized receptors

 A.       SKIN: Gen'l Features/Functions:

•         largest body organ; 3000sq. "

•         maintains body temp.

•         provides protection

•         specialized receptors for pain, temp., pressure, touch

•         performs excretory functions

•         synthesizes Vit D

•         bolster immune response

•         blood reservoir   (approx. 10%)

B.      ANATOMY

1.        EPIDERMIS- outer thinner portion; primarily epithelium

a.          Cellular components:

-         KERATTNOCYTES - most numerous; produce keratin
(waterproofs skin, aids in immunity)
MELANOCYTE - produce melanin - skin color pigment
LANGERHAN - aids in immunity; produced by bone marrow

-         MERKELS - tactile

b.          ORGANIZATION: 4-5 layers

1)    STRATUM BASALE (Germativum) - innermost; single
layer of cubodial or columnar; capable of continued cell
division; upward movement of cells to surface takes 2 weeks

2)                                   STRATUM SPINOSUM -8-10 rows of polyhedral cells;
prickly surface; where hairless, has touch/tactile nerve
endings (MERKEL'S DISC)

3)                                   STRATUM GRANULOSUM - 3-5 rows of flattened cells;
darkly staining due to KERATOHYALIN (precursor of
keratin); nuclei/cells eventually die

4)                                   STRATUM LUCIDUM - several rows of clear flattened
dead cells; contain ELEIDEN( formed from keratohyalin):
only in thick skin(sole/palm)

5)                                   STRATUM CORNEUM - 25-30 rows of dead flat cells
filled with Keratin

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c.         EPIDERMAL GROOVE/RIDGES

1)    EPIDERMAL RIDGES - at 3-4th fetal month epidermis
conforms to contour of underlying dermal papillae;
genetically determined and unique; enlarge with age.

2)                                  EPIDERMAL GROOVES - divide surface into a # of
diamond shapes with hairs usually at groove as intersections

DERMIS - inner thicker portion; primarily connective tissue with some fibers extending into subcutaneous layer; varies in thickness with location

a.          Cellular components:

Fibroblasts - manufacture various fibers

Macrophages- specialized WBC

Plasma Cells - specialized WBC, produce antibodies

Mast Cells - specialized WBC

b.          Organization - 2 regions

1)    PAPILLARY REGION - outermost; loose connective tissue
with some elastic fibers; 1/5 total layer; has DERMAL
PAPILLAE - fingerlike projections increasing surface area;
has MEISSNER'S CORPUSCLES (touch receptors) in
projections

2)                                   RETICULAR REGION - 4/5 of total layer; dense irregular
connective tissue with collagenous and coarse elastic fiber
bundles - provides extensibility and elasticity to skin; spaces
between fibers have adipose tissue, hair follicles, nerves, oil
glands, sweat gland ducts and PACINIAN CORPUSCLES
(pressure receptors)

•    STRIAE (stretch marks) - created by tears in this region

c.          LINES OF CLEVAGE- Collagen and elastic fibers in one location
are usually arranged in parallel bundles. This accommodates
applied forces and becomes clinically significant for cuts or surgical
procedures.

SUBCUTANEOUS LAYER/HYPODERMIS/SUPERFICIAL FASCIA –

layer beneath dermis; areolar and adipose tissue. Attaches to underlying organs/tissues.

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C.      SKIN COLOR - based on:

1.          MELANIN CONTENT - produce by basale and spinosum layers by
melanocytes

•         Mechanism: Tyrosine under enzymatic influence of tyrosinase produces
melanin; influenced by UV exposure and MSH from ant. pituitary

•         ALBINISM -inherited inability to produce melanin

•         VITILIGO - partial loss of melanocytes; patchy white spots

 

2.                                    CAROTENE CONTENT - produce in dermis and stratum corneum

3.                                    BLOOD CONTENT (Hemoglobin) - in capillaries of dermis

D.     WOUND HEALING

1.        EPIDERMAL ONLY -abrasion or 1-2 degree burns

Mech.: Basal cells break contact with basement membrane, enlarge and migrate to wound area. Migration occurs as sheets of cells from opposite sides until they meet (CONTACT INHIBITION). These divide to form new strata thereby thickening new epidermis. Once coverage beneath scab is sufficient, scab sloughs off.   Simultaneously, basal epidermal cells divide to replace migrated ones.

2.              DEEP WOUNDS

a.          Inflammatory Phase - increase localized circulation to dispose of
foreign matter, dying tissue and prepare for wound repair. Blood
clot forms in wound and loosely unites wound edges; epithelium
migrates across. Vasodilatation and increase blood vessel
permeability brings Neutrophils and Monocytes to phagocytize
microbes. Local mesenchymal cells generate fibroblasts.

b.         Migratory Phase - clot forms scab; epithelial cells migrate beneath

it.  Fibroblasts migrate along fibrin threads and begin scar tissue synthesis (collagenous fibers + protein polysaccharides). Damages BV begin to grow FIBROPLASIA - period of scar tissue formation.

c.         Proliferative Phase – extensive growth beneath scab (epithelial cells,

collagenous fibers and BV)

d.              Maturation Phase – scabs sloughs off once epidermis is normal
thickness; collagenous fibers become organized; fibroblasts are
absorbed; BV are restored to normal

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     EPIDERMAL DERIVATIVES

       I - HAIR (PILI): primarily used for protection

     A.     COMPOSITION

                1 .         SHAFT- superficial portion

a.          MEDULLA - inner area; rows of polyhedral cells containing eleidin
and air spaces

b.          CORTEX - middle area; major portion of shaft; elongated cells
containing pigment granules (more in dark hair than in light)

c.          CUTICLE - outer area; single layer of thin flat scablike heavily
keratinized cells; interleafed arrangement

2.         ROOT - portion below skin surface; penetrates into dermis and
subcutaneous layer

a.        HAIR FOLLICLE - sheath surrounding root

b.        LAYERS (from cuticle outward)

•         INTERNAL ROOT SHEATH - formed by proliferating cells of
matrix; forms cellular tubular sheath

•         EXTERNAL ROOT SHEATH - downward continuation of
basale and spinosum layers; near surface contain all epidermal
layers

•         GLASSY MEMBRANE - thickened basement membrane
sheathed in dense connective tissue

3.         BULB - enlarged base of hair follicle; contains indentation (Papillae of
hair); filled with loose connective tissue; has BV for nourishment

a.         MATRIX - region of cells with bulb (germinal layer); area which produce new hair by cell division

 

4.       ARRECTOR PILI - smooth muscle associate with hair; extends from

dermis to side of hair follicle; pulls hair vertical when stressed

5.       Hair Growth, Removal and Color

a.                        Growth Cycle - growth for 3 years followed by resting phase of 1-2

years
b.          Color - determined by melanin concentration; Dark- pure melanin;

light/red-melanin +sulfur/iron; gray - decreased in melanin; white-

air in hair shaft

c.         Removal

•         Depilatory - any substance which remove superfluous hairs by
dissolving protein in hair shaft; non-permanent

•         Electrolysis - hair bulb is destroyed; permanenet

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II - GLANDS

A.     SEBACEOUS (OIL)

1.          Type of functional glandular epithelium: Holocrine delivery

2.                                         Simple branched acinar

3.                                         Produces SEBUM - mix of fats, cholesterol protein and inorganic salts.
Protects skin/hair by reducing evaporation and bacteria growth

4.                                         Usually connected to hair follicle, secreting portion in dermis; those not
associated with hair opening directly on skin surface (e.g. lips, glands penis &
labia minora)

B.      CERUMINOUS

1.    Simple coiled tubular; secretory portion in submucosa and excretory ducts
open directly onto surface of meatus or into sebaceous ducts; found only in
external auditory meatus (canal)

2.                                     produces CERUMEN - secretions of ceruminous and sebaceous glands

C.      SUDORIFEROUS (SWEAT)

1.    Type of functional glandular epithelium: Apocrine delivery

2.                                     Produces SWEAT (Perspiration) - mix of water, salts, urea, uric acid, AA,
ammonia, sugar ascorbic and lactic acid; maintains body temp, and voids
wastes

•    Mammary glands - specialized sudoriferous glands; produce milk instead of sweat

3.         Major Categories:

a.          APOCRINE - simple branched tubular; secretory portion in dermis
or sub Q, excretory portion opens into hair follicle; found in skin of
axilla, pubic region and areolar of breasts; more viscous than eccrine
glands

b.         ECCRINE - most common; simple coiled tubular; secretory portion
in sub Q and excretory ducts project upward and terminate on
epidermis surface; found throughout skin EXCEPT margins of lips,
nail beds, glands of penis, glands clitoris, labia, minora, and eardrums

III - NAILS - hard keratinized epidermal cells; form clear solid covering over dorsal surfaces on terminal portion of toes/fingers

 A.        COMPONENTS

1.    FREE EDGE – portion which projects beyond distal end of digit

2.                                    NAIL ROOT – portion hidden in proximal nail groove

3.                                    NAIL BODY – portion of nail visible

•    LUNULA - whitish semilunar area at proximal end of body; vascular tissue doesn’t show through here

4.                                    NAIL FOLD - fold of skin extending around proximal and lateral

5.                                    NAIL GROOM - furrow between nail bed and nail proper

6.                                    NAIL BED - epidermis beneath nail

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7.         NAIL MATRIX - proximal portion of nail bed; brings about nail
growth

•    Mech.: transforms superficial cells of matrix into nail cells. The outer, harder layer is pushed forward over the stratum germinativum. Rate 1 MM/week; slower with toenails

8.                                     EPONYCHIUM (CUTICLE) - narrow band of epidermis extending
from margin of nail wall (lateral); occupies proximal border of nail;
consists of stratum corneum

9.                                     HYPONYCHIUM - thickened area of stratum corneum below free
edge of nail

SKIN DISORDERS

BURNS

1st degree - only surface epithelium; no blister or edam

2nd degree - deeper layer of epidermis and upper layer of dermis; blister

(BULLAE) formation

3rd degree - destruction of epidermis/dermis and loss of skin function;

regeneration is slow and much granular tissue formation

LUND-BROWDER Method / rule of 9's- technique for estimating

extent of burn.