Student made handout... Credits to the owner of original pictures used in this handout.

1. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao
INTEGUMENTARY SYSTEM
Functions:
1. Body temperature regulation.
2. Reservoir for blood
3. Protection from external environment
4. Cutaneous sensations
5. Excretion and Absorption
6. Vitamin D synthesis
Composition:
- Skin
- Accessory structures:
o Hair
o Nails 1. Keratinocytes: keratin & lamellar granules
o Various glands - 90% of the epidermal cells
- Produced keratin (protein)
Skin  Tough fibrous protein that help the skin
- Largest organ of the body from heat, microorganisms, underlying
tissues of skin and chemicals.
Two principal parts: - Lamellar granules
 Stratum granulosum
1. Epidermis  Functions: Releases a water and proofing
- Superficial portion sealant
- With 5 layers
2. Dermis
- Inner portion
- With 2 regions
2. Melanocytes: melanin
- 8% of the epiderma cells
- Produce pigment – melanin  skin color
Epidermis
- A keratinized stratified squamous epithelium
- Consists of 4 principal types of cells: 3. Langerhans cells
- Arise from the bone marrow
- Migrate to epidermis
- Participate in immune responses

2. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao
- Shed off when you take a bath
 Continuous Friction
- Callous  an abnormal thickening of epidermis due
to friction
2. Stratum Lucidum
- “lucid” – “clear”
- Present in the skin of finger tips, palms, and soles.
- 3 – 5 clear layers of flat dead keratinocytes with
intermediate filaments and thickened plasma
4. Merkel cells membrane.
- It is the least numerous of epidermal cells
- Located at the deepest part of stratum 3. Stratum Ganulosum
basale/geminativum. - 3 – 5 layers of flattened keratinocytes
- In contact with tactile disc or merkel disc - Consists of keratohyaline and lamellar granules
Function: o A distinctive feature of the layer
- Both participate in sensation of touch o Darkly staining granules of the
stratum
Function: Organized intermediate filaments into thicker
bundles.
4. Stratum Spinosum
- The superficial of basale
- 8 – 10 layers of polyhedral keratinocytes
- Fit closely together
- Thorn – like spines bundles of intermediate
filaments of the cytoskeleton joins the cell tightly to
one another to provide strength and flexibility of
Layers of the Epidermis the skin.
5. Stratum Basale/Geminativum
- Active in cell division
- Compose of one layer of simple cuboidal/columnar
keratinocytes.
 Some considered them as stem cells
 Continue cell divisions to produce new
keratinocytes
- Merker cell
- Melanocytes
Dermis
- Second deeper part of the skin
- Composed of connective tissue containing collagen
and elastic fibers
1. Stratum Corneum o Functions: for extensibility (stretch; obesity)
- 25 – 30 layers of dead flat keratinocytes. and flexibility (Return to its original form)
- Contains the dead flat intermediate filaments - Include cells such as fibroblasts, macrophages, and
- Consists of keratohyaline some adipocytes
o Function: Water repellant barrier - Blood vessels, nerves, glands, and hair follicles are
- Lamellar granules embedded in dermal tissue
- Lipid from lamellar granules (barrier in between)

3. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao
Two regions of Dermis: 3. Meissner’s corpuscle
- Encapsulated
1. Papillary region - Palmar and planthar
- The superficial portion of the dermis - Fingertips
- Consists of areolar connective tissue with tissue
with elastic fibers 4. Ruffini corpuscles
- Contains dermal papillae - Type II cutaneous mechanoreceptor
 Finger-like projections that indent the
epidermis to the dermis. 5. Pacinian corpuscle
Contains the following: - Located deeper part of the dermis
- Encapsulated with multicellular ovoid structures
a. Meissner’s corpuscle Function: Respond to deeper pressure.
- For touch sensation
b. Free nerve endings
- Contains the dendrites that initiates signals that are
felt such as warm, coolness, pain, tickling and
itching.
*Papillary layer – small fine collagen
2. Reticular region
- Deeper portion of dermis
- Consists of dense irregular connective tissue
containing bundles of collagen and some elastic
fibers.
*Reticular layer – more coarsely-textured collagen
fibers.
Functions of the connective tissue of the dermis:
1. Tough collagen fibers and resilient elastic fibers
provide mechanical strength for skin. Lines of
tension in the dermis called Langer’s lines, affect
healing after surgical incision
2. The ground substances of the dermis serve as the
substrate for diffusion of nutrients and wastes to
and from various other tissue components.
3. Mast cells, lymphocytes and macrophages in the
connective tissue carry our surveillance for the
immune system.
4. Finally, the dermis together with its associated
blood vessels and nerves is capable of active
responses to injury, yielding the defensive reaction
Sensory receptors / free nerve endings of the reticular
of inflammation, followed by the healing processes
layer:
of growth and repair
1. Nociceptotrs – pain receptor
Subcutaneous layer (Hypodermis)
2. Tactile/Merkel disc
- The hypodermis (hypo – “under” + dermis – “skin”)
- Type one cutaneous mechanoreceptor
or subcutaneous (sub – “below” + cutaneous) layer
- For sensation touch

4. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao
lies below the skin and is made up of loose - Scatters light from the dermis without altering its
connective and adipose tissues. color
- The hypodermis binds the skin to underlying organs - Whiteness of white skin
while allowing the skin to move somewhat - Reflection of collagen
independently of underlying structures.
- Adipose tissue in the hypodermis provides padding 3. Blood
and shock-absorption that helps to protect - Hemoglobin and RBC
underlying tissues from damage; it is also important - Scatters red light
in insulating against loss of body heat. - Responsible for the pinkness in pigmented skin
- Because the subcutaneous layer contains numerous ***The amount of pigment, the thickness of dermis,
blood vessels but no vital organs, it is a near-ideal and the degree of perfusion in dermal capillaries vary.
place to inject drugs. This is why so many drugs are
administered through subcutaneous injection by a Skin texture
hypodermic (hypo-“under”+ dermic – “skin”) - Affect the thickness and smoothness of the
needle. epidermis, by the quality of fibers in the dermis, and
by the amount of fluid in dermal connective tissue.
Types of skin
Note:
1. Thin skin Both edema (accumulation of excess fluid in connective
- Covers all parts of the body except palms, palmar tissue) and dehydration can dramatically alter the
surfaces of the digits, and soles appearance of skin
- Epidermis is thin
- Stratum lucidum lacking; stratum spinosum and Accessory structures of the skin
stratum Corneum are thin 1. Hairs
- Has fewer dermal papilla, lacks epidermal ridges 2. Glands
- Has hair follicles, arrector pili muscle and oil glands 3. Nails
but fewer sweat glands than thick
- Sparser distribution of sensory receptors. Hairs
- Composed of columns of dead, keratinized cells
2. Thick skin bounded together by extracellular proteins
- Covers palms, palmar surfaces of digits and soles Parts:
- Thick epidermis 1. Shaft – superficial portion
- With stratum lucidum and thicker stratum 2. Roots – penetrates into the dermis
spinosum and stratum corneum. Concentric layers of shaft and root:
- More numerous dermal papillae thus has epidermal
ridges a. Medulla
- Lack hair follicles, arrector pili muscle, sebaceous - Inner portion
gland. - 2 or 3 rows of polyhedral-shaped cells containing
- Has more sweat glands that thin skin pigment granules and hair spaces.
- Sensory receptors are more densely clustered.
b. Cortex
Skin color - Middle portion
- It forms the major part of the shaft
1. Melanin - Contains pigments granules of the hair
- Produced by melanocytes - White/gray hair – air bubbles
- Yellowish-brown color of the epidermis
- Lesser melanin – Light will penetrate easily into the c. Cuticle
skin --- prone to cancer. - Outermost layer
- Single layer of flat cells that are heavily keratinized
2. Collagen

5. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao
3. Follicle – tubular invagination lined by stratified
squamous epithelium similar to epidermis; 6. Hair root plexuses
surrounds the root of the hair; made up of: - Dendrites of neurons sensitive to touch
a. External root sheath - Generate nerve impulses in hair shaft is moved.
- Downward continuation of epidermis
- Contains the stratum basale Glands
b. Internal root sheath
- It forms the cellular tubular sheath between the
external root and the hair.
Hair follicles are associated with:
a. Sebaceous glands – secrete oil into the hair follicle
as well as nerve ending and smooth muscle to form
the pilosebaceous apparatus.
b. Nerve endings – detects deflection of the hair shaft
and also controls piloerection.
c. Smooth muscle – arrector pili ; affect piloerection
4. Bulb – the base of hair follicle; onion-shaped
structure; houses
a. Papilla of the hair
- Nipple-shaped indentation
- Contains areolar connective tissue
- A lot of Blood vessels that nourish the growing hair
follicle
b. Matrix
- Germinal layer of the cell w/c rise from stratum
basale.
Function:
- Responsible for growth of existing hairs
- Produce new hairs when old hairs are shed.
 Sebaceous glands
5. Arrector pili muscle – smooth muscle cells - Associated with hair follicles
- Stimulated by autonomic nerve endings to contract - Holocrine glands
pulling the hair shaft perpendicular to the skin  The whole cell is secreted
surface during cold or fright.

6. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao
Function:
- It coats the surface of the hair and help keep them
from drying and becoming brittle
- It prevents excessive evaporation of water from the
skin.
- It keeps the skin soft and pliable
- It inhibits growth of certain bacteria
 Sweat glands
- 3-4 millions producing their secretion
- Exocytosis – release secretion
Two types:
a. Ecrine 1. Nail body – visible portion of the nail
- Simple coiled tubular gland 2. Free edge – part of that may end pass the distal
- Common sweat gland ends of digits
Function: 3. Nail root – proximal edge of the nail plate that
- Regulates body temperature is buried in the skin.
- Waste removal 4. Lunula – whitish crescent shaped covered by
portion of the nail bed.
b. Apocrine 5. Hyponichium – nail bed; skin of nail bed;
- Simple coiled tubular gland provide support
- Stimulated during emotional stress and sexual 6. Eponychium/cuticle – a horny epidermal
excitement extension of the tip of the nail folds.
- Secretion of cold sweat
Nails
- Plates of tightly packed, hard, keratinized epidermal
cells.
- Cells form a clear, solid covering over the dorsal
surfaces of the distal portions of the digits
- Parts: