Download 8.SKIN

Integument
(SKIN)
By Dr. Abdullah
Aldahmash
The single largest organ.
About 16% of the human body weight.
Its about 1.2- 2.3 m2.
Has two layers
1. epidermis : epithelial tissue
2. dermis: connective tissue
Two types
1.
thick skin (glabrous): Palms and soles (400-600µm, 0.8-1.4 mm)dermatoglyphs
2.
thin skin: the hairy: every where (75-150µm , 0.07-0.12 mm)
hypodermis (subcutaneous tissue) as a pad for the skin (the superficial
fascia of gross anatomy), helps the skin to slide over underlying organs.
–
Panniculus adiposus
Dermis epidermis junction
-
irregular
- dermis and epidermis
interdigitate though
1. dermis projection into
the epidermis {papillae
(P) papilla (s)}.
2. epidermis evaginations
- basement membrane
Epidermis
-
-
-
consist MAINLY of a
stratified sequamous
keratinized epithelium.
0.07 to 0.12 mm in
thickness
Epidermal layers
1. stratum basale (stratum
germinativum).
2. stratum spinosum
3.
4.
stratum granulosum
stratum lucidum
5. stratum corneum
stratum basale
Mitotically active
Cuboidal /low columnar
Large nucleus
stratum Spinosum
Thickest layer
Mitotically active (less!!)
Has more tonofilaments
Stratum granulosum
3-4 layer
The most superficial layer with nucleated cells
Has keratohyalin granules
Membrane-coating granules
Stratum Lucidum
Only in thick skin
No nuclei and organelles
Stratum Corneum
Flattened cells.
Has two layers
– squames or horny
– desquamated
Epidermal specialized cells
-
melanocyte
-
Lengerhans
-
melanin producing cells
1. star-shape cells
2. bone marrow derivative
3. play important role in skin immunology
Merkel’s
1.
present mainly in thick skin most abundant in
the fingertips
2. serve as mechanoreceptors
melanocytes
Located under or within
the basal layer (stratum
basale)
Produce melanin
Derived from neural crest
cells
Attached to basement
membrane by
hemidesmosomes
Developmental stages of
mature melanin granule
Tyrosine is synathesized in
the RER then accumulated
in vesicles (melanosomes)
by Golgi
Tryrosine; (inside
melanosomes), activated by
UV and after series of
activation, will be
converted into melanin
Melanosomes (containing
melanin only) travel through
melanocyte projections to be
deposited (Cytocrine
secretion)
Dermis
1- Development regulator (mesodermal
derivative).
2- Has two layer with indistinct boundaries:
1- papillary layer
2- reticular layer
- papillary layer
• mainly of loss connective tissue, fibroblasts and other connective
tissue cells (Mast, macrophages and leukocytes).
•
collagen, elastic and Anchoring fibrils
•
Mechanoreceptors (Meissner corpuscles & Krause end bulb)
-
reticular layer
•
dense connective tissue
•
more fibers and less cells
•
thick elastic fibers.
• Type I collagen fibers.
• Some smooth muscles.
• Mechanoreceptors (pacinian corpuscles & Ruffini corpuscles )
Vessels &skin sensorial
receptors
Two arterial plexuses, located between
- papillary and reticular layer
- dermis and subcutaneous
three veins plexuses, located between
- two in the same location as the arterial
- the 3rd in the middle of the dermis
Extensive sensory receptors are found in the skin:
- free nerve ending (touch-pressure)
- encapsulated: Vater-Pacini,Meissner and Krause corpuscles
- expanded: include Ruffini endings
Skin appendages or
derivatives
Hair
Nails
Gland
1. Sebaceous glands
2. Sweet glands
3. Mammary glands
Sweat gland
Eccrine:
1- Simple
2- Embedded in the dermis
3- two cell types in the secretory part:
-dark (pyramidal) lining the lumen & they
have secretory granules in their apical
surface.
-clear devoid of secretory granules and
accumulate glycogen.
4- surrounded by myoepithelial
Apocrine
1- present in axillary, areolar and anal
region.
2- hair associate.
3- their product is initially odorless.
• Acinar glands, i.e. have
several acini opening into a
short duct.
• holocrine gland.
• in some regions they open
directly into the epidermal
surfaces, e.g lips, penis and
clitoridis.
• secret sebum
•Controlled by testosterone in
men and by ovarian and adrenal
androgens in women.
Sebaceous
glands