The organs of the integumentary system include?
skin & accessory structures including hair, nails, glands, blood vessels, muscles and nerves
Dermatology
medical specialty for the diagnosis and treatment of disorders of the integumentary system.
Skin
aka?
location?
size?
subcutaneous membrane
covers body
largest organ of body by surface area & weight
Skin
area & weight
% of body weight
2 square metres (22 sq. feet)
4.5-5 kg (10-11 lb)
7%
Skin thickness
range & average
0.5-4.0 mm thick
thinnest on eyelids
thickest on heels
average = 1-2 mm
SKIN
(2) major layers
1) epidermis - outer, thinner layer; consists of epithelial tissue
2) dermis - inner, thicker layer
Beneath the dermis is?
a subcutaneous (subQ) layer (also called hypodermis)
which attaches the skin to underlying tissues & organs.
Important characteristics of the Epidermis
(2)
- composed of keratinized stratified squamous epithelium
contains 4 major types of cels
Epidermis
(4) major types of cells
1) keratinocytes
2) melanocytes
3) Langerhans cells
4) Merkel cells
Major cells of the epidermis: Keratinocytes
(90% of the cells)
- produce keratin (a tough fibrous protein that provides protection)
Major cells of the epidermis: Melanocytes
produce the pigment melanin that protects against damage by UV radiation
Major cells of the epidermis: Merkel cells
involved in immune responses, arise from red bone marrow
major cells of the epidermis: Merkel cells
function in sensation of touch along with adjacent tactile discs
The epidermis contains how many layers?
four major layers (thin skin)
five major layers (thick skin)
(5) layers of the epidermis
1) stratum corneum
2) stratum lucidum
3) stratum granulosum
4) stratum spinosum
5) stratum basale
Stratum Basale
aka stratum germinativum
deepest layer
continuous cell division occurs which produces all other layers
Stratum Spinosum
8-10 layers of keratinocytes
Langerham cells & projections of melanocytes present
Stratum Lucidum
present only in thick skin
(the skin of the fingertips, palms, and soles)
Stratum granulosum
includes keratohyalin and lamellar granules
consists of 3 to 5 layers of flattened keratinocytes undergoing apoptosis
marks transition between deeper metabolically active strata & dead cells of superficial strata
Stratum corneum
composed of many sublayers of flat, dead keratinocytes called corneocytes or squames that are continuously shed and replaced by cells from deeper strata;
constant friction can stimulate formation of a callus.
Formation of a callus
constant friction
Keratinization
the accumulation of more and more protective keratin, occurs as cells move from the deepest layer to surface layer
Dandruff
- an excess of keratinized cells shed from the scalp
Important characteristics of the Dermis
composed of connective tissue containing collagen & elastic fibers
contains 2 layers
(2) layers of the dermis
1) Papillary region
2) Reticular region
Papillary region
consists of?
containing?
outer region, consists of areolar (soft) connective tissue containing thin collagen, elastic fibers, dermal papillae (including capillary loops), corpuscles of touch & free nerve endings
Reticular region
deeper region,
consists of dense irregular connective tissue
containing collagen and elastic fibers, adipose cells, hair follicles, nerves, sebaceous (oil) glands, & sudoriferous (sweat) glands
Striae
stretch marks
- appear if the skin is stretched too much
Lines of Cleavage
tension lines” in the skin indicate the predominant direction of underlying collagen fibers
Epidermal ridges
function?
reflect contours of the underlying dermal papillae & form the basis for fingerprints (and footprints);
function: to increase firmness of grip by increasing friction.
Subcutaneous (subQ) Layer
aka hypodermis\
not part of the skin but attaches to skin to underlying tissue
The Subcutaneous Layer (and sometimes the dermis) contains?
lamellated (pacinian) corpuscles which detect external pressure applied to the skin
Accessory structures of the skin
include hair, skin glands & nails
Hair
aka?
(3) important functions
Pili
1) protection
2) reduction of heat loss
3) sensing light tough
Hair
composed of?
composed of dead, keratinized epidermal cells
Hair consists of?
shaft - mostly projects above
root - penetrates into dermis
hair follicle - surrounds root of hair, made up of external & internal root sheath referred together as the epithelial root sheath
dermal root sheath - dense dermis surrounding hair follicle
(3) different types of hair
1) lanugo
2) vellus haira
3) terminal hairs
Lanugo
fine, non-pigmented downy hairs on body
Vellus hairs
replace lanugo
short, fine, pale hairs
barely visible
terminal hairs
long, course, heavily pigmented
replace lanugo of eyebrows, eyelashes & scalf
Hair color is determined by ?
the amount and type of melanin
sebaceous (oil) glands
connected to?
secrete?
hair follicles
oily substance called sebum
Sebum
an oily substance secreted by sebaceous glands to prevent dehydration of hair & skin and inhibit growth of certain bacteria
(3) Types of Skin Glands
1) Sebaceous glands
2) Sudoriferous (sweat) glands
3) Ceruminous glands
Sudoriferous (sweat) glands
(2) types
1) Eccrine (merocrine) sweat glands
2) Apocrine sweat glands
Dermatoglyphics
the sutdy of the pattern of epidermal ridges
Eccrine (merocrine) sweat glands
function?
location?
helps to cool body by evaporating, & eliminates small amounts of wastes
distributed throughout skin of most regions especialy in skin of forehead, palms & soles
- located mostly in deep dermis (sometimes in subQ layer)
Apocrine sweat glands
located?
function?
located mainly in the skin of the axilla, groin, areolae,
and bearded facial regions of adult males.
- their excretory ducts open into hair follicles
- sweat secreted during emotional stress & sexual excitement
Ceruminous Glands
what are they & where are they located?
function?
Modified sweat glands located in the external auditory (ear) canal
secretary portion lie in subQ layer, deep to sebaceous glands
Along with nearby sebaceous glands, they are involved in producing a waxy secretion called cerumen (earwax) which provides a sticky barrier that prevents entry of foreign
bodies into ear canal.
Functions of Nails (3)
1) protect distal end of digits
2) provide support & counterpressure to palmar surface to enhance touch perception & manipulation
3) allow us to grasp & manipulate small objects + scratch & groom
What are Nails?
Where are they located?
composed of hard, keratinized epidermal cells
located over dorsal surfaces of the ends of fingers & toes
Each nail consists of? (6)
1) free edge
2) transparent nail body
3) whitish lunula
4) eponychium (cuticle)
5) nail root
6) hyponychium (nail bed)
Free Edge of Nail
part of nail body that may extend past distal end of digit
Nail Body
aka?
(plate)
transparent
whitish lunula at its base
comparable to stratum corneum of general epidermis
Lunula
whitish crescent-shaped area at base of nail body (plate)
white b/c vascular tissue underneath does not show through thickened region of epithelium
Nail Root
embedded in a fold of skin
Hyponychium
nail bed
thickened region of stratum corneum that secures nail to fingertip
Eponychium
cuticle
narrow band of epidermi
consists of stratum corneum
extends from & adheres to margin (lateral border) of nail wall
- occupies proximal border
(2) major types of skin
1) thin (hairy) skin
2) thick (hairless) skin
thin (hairy) skin
covers what body regions?
all body regions EXCEPT palms, palmar surfaces of digits & soles
thick (hairless) skin
covers what body regions?
palms, palmar surfaces of digits & soles
Integumentary System - functions? (6)
1) regulate body temp
2) store blood
3) protection from external environment
4) detect cutaneous sensations
5) excrete/absorb substances
6) synthesize vitamin D
(5) Hair functions
1) protection from injury (scalp)
2) protection from sun's rays
3) sensing light touch
4) decreasing heat loss
5) protect eyes from foreign particles
Main Organ of the Integumentary System
skin
(3) associated structures in the Integumentary system
1) nails
2) hair
3) glands
Most superficial region of the dermis
papillary region
Most common connective tissue fibre found in the dermis
collagen
Which layer of the integument releases the heat from the body via the blood vessels?
dermis
What material makes the epidermis tough?
keratin
Distinguish between Pacinian corpuscles, Meissner’s corpuscles and pain receptors in the skin
Pacinian - located deep in dermis & hypodermis
- function to recieve sensation of deep pressure
Meissner's - located just underneath epidermis
- function to percieve light tough
Pain Receptors - in the dermis
- respond to numerous pain stimuli
Approximately how long does it take for the epidermis to renew itself?
4-6 weeks
Piloerector Muscle
What is it?
What does it do?
smooth muscle that extends from superficial dermis to dermal root sheath
contracts which pulls hair shaft perpendicular to skin surface (upright)
What is the outermost portion of the hair?
cuticle
