• Survival of all living organisms requires that
they should eliminate foreign invaders , such as
infectious pathogens & damaged tissues .
• These functions are mediated by complex host
immune response called as an
• Inflammation is a protective attempt by
the organism to remove the injurious
stimuli and to initiate the healing
• Hence without inflammation, wounds
and infections would never heal.
• Definition –
The word inflammation is derived from
Latin word inflammare, which means “to set
• It is a complex reaction to injurious agents
such as microbes & damaged, usually
necrotic, cells that consists of vascular
responses, migration & activation of
leukocytes & systemic reactions.
SIGNS OF INFLAMMATION
• RUBOR- REDNESS DUE TO INCREASED
BLOOD BLOW AND VASODILATION
• CALOR- OR HEAT DUE TO INCREASE
BLOOD FLOW TO THE PERIPHERY
• TUMOR- SWELLING FROM INFLAMMATORY
• DOLOR-PAIN FROM SWELLING AND
PRESENCE OF INFLAMMATORY
• FUNCTIO LAESA-LOSS OF FUNCTION DUE
AND STRUCTURAL NECROSIS
2nd Yr Pathology 2010
The basis of the five cardinal signs
• Increased blood flow due to vascular dilatation gives
redness and heat.
• Increased vascular permeability gives oedema causing
• Certain chemical mediators stimulate sensory nerve
endings giving pain. Nerves also stimulated by stretching
• Pain and swelling result in loss of function.
Types of inflammation
1. Acute inflammation –
It is the rapid response to the injury or microbes or
other foreign substances that is designed to deliver
leukocytes & plasma proteins to the site of injury .
1. Infections – Bacterial , viral , fungal or parasitic
2. Trauma –Blunt or Penetrating
3. Tissue necrosis-
4. Foreign bodies – sutures
5. Immune reactions
• Outcomes of acute inflammation-
2. Progression to chronic inflammion.
3. Scarring or fibrosis
2. Chronic inflammation –
• It is inflammation of prolonged duration in which
active inflammation, tissue injury & healing proceed
• Immunologists define as period when
• Clinicians define as recurrent inflammation prior
to completion of repair or resolution
• Causes –
1. Persistent infection
2. Immune mediated inflammatory diseases
3. Prolonged exposure to potentially toxic agents
Fibrotic diseases (Scaring)
combinations of the above
Differences between Acute & Chronic Inflammation
Acute inflammation Chronic inflammation
Definition It is the rapid response to
the injury or microbes or
other foreign substances
that is designed to deliver
leukocytes & plasma
proteins to the site of
It is inflammation of
prolonged duration in which
active inflammation, tissue
injury & healing proceed
Onset Rapid Insidious
Duration Short ( Few minutes to
Long (Days to years )
Acute inflammation Chronic inflammation
Specificity Non- specific Specific, where immune
response is activated
Cells involved Neutrophils Lymphocytes , plasma cells
, macrophages , fibroblasts
Active vasodilation ,
New vessels formation
Cardinal signs Present Absent
Outcomes of Acute Inflammation
• Resolution of tissue structure and function with elimination of
• Tissue destruction and persistent inflammation
• pus-filled cavity (neutrophils, monocytes and liquefied cellular debris)
• walled off by fibrous tissue and inaccessible to circulation
• tissue destruction caused by lysosomal and other degradative enzymes
• loss of epithelial surface
• acute inflammation in epithelial surfaces
• abnormal communication between organs or an organ and a surface
• Causes distortion of structure and sometimes altered function
• Chronic inflammation
– Marked by replacement of neutrophils and monocytes with lymphocytes,
plasma cells and macrophages
– Accompanied by proliferation of fibroblasts and new vessels with
• Definition – Chemical substances that trigger
certain processes in an inflammatory reaction.
Cell derived Plasma derived
Histamine Kinin system mediators
Serotonin C- reactive protein
Neutrophilic proteases Complement system
Interleukins( IL-1 . TNF- α )
Arachidonic acid (PG, LT)
• Removal of Debris
– begins early and initiated by liquefaction and
removal of dead cells and other debris
• Formation of Granulation Tissues
– connective tissue consisting of capillaries and
fibroblasts that fills the tissue defect created by
removal of debris
– fibroblasts produce collagen until granulation
tissue becomes less vascular and less cellular
– progessive contraction of the wound occurs,
resulting in deformity of original structure
Factors that Impede Repair
• Retention of debris or foreign body
• Impaired circulation
• Persistent infection
• Metabolic disorders
• Dietary deficiency
– ascorbic acid
Healing and granulation
• Fibroplasia is a response to
– Damaged connective tissue
– Parenchymal damage exceeds regenerative capacity
• Hyperplasia of connective tissue
– coordinated proliferation of fibroblasts with a rich bed of
– intensely hyperemic with a roughened or granular,
– healthy granulation tissue resists secondary infections
Healing by First Intention
• Clean, surgical incision or other clean narrow cut
• Focal disruption of epithelial basement membrane
with little cell damage
• Regeneration dominates fibrosis
• Scabbing with fibrin-clotted blood
• Neutrophils migrate to edges
• Epidermis becomes mitotic and deposits ECM
• Macrophages replace neutrophils
• Vascularization and collagen deposition fills gap
• Contraction of collagen minimizes epidermal
Healing by Second Intention
• Larger area of tissue injury such as abcess, ulcer,
infarction that destroys ECM
• Large clot or scab with fibrin and fibronectin fills gap
• Larger volume of necrotic debris must be removed
by more neutrophils and macrophages
– Opportunity for collateral damage by phagocytes
• Scar tissue formed from vascular cells, fibroblasts,
• Contraction of myofibroblasts distorts tissue
• More prone to infection
• Skin is the largest organ of the human body
• Accounts for 16-20% of body weight…it weighs twice as much
as your brain
• For the average adult human, the skin has a surface area of
between 1.5-2.0 sq.mtrs
• The skin is composed of two basic layers (regions)..
– Epidermis – outermost layer
– Dermis –underlying connective tissue
• Subcutaneous fat (Hypodermis),inspite of its close anatomic
relationship and tendency to respond jointly to pathologic
processes,is not a part of skin basic structure
• The skin is an organ of protection. The primary function of
the skin is to act as a barrier. The skin provides protection
from: mechanical impacts and pressure, variations in
temperature, micro-organisms, radiation and chemicals.
• The skin is an organ of regulation. The skin regulates
several aspects of physiology, including: body temperature
via sweat and hair, and changes in peripheral circulation
and fluid balance via sweat. It also acts as a reservoir for
the synthesis of Vitamin D.
• The skin is an organ of sensation. The skin contains an
extensive network of nerve cells that detect and relay
changes in the environment. There are separate receptors
for heat, cold, touch, and pain.
• Primarily made up of keratinized stratified squamous
• Gives strength to the skin.
• Varies in thickness from thick skin to thin skin
• Eyelids- 0.04 mm,Palms- 1.6 mm,average 0.1 mm
• It does not have any vascularization, so it relies on the connective
tissues deep to it.
• Also contain melanocytes, merkel’s cells and Langerhans cell
Layers of epidermis
• Stratum basale (the deepest layer)
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum
• Stratum corneum (most superficial layer of epidermis)
• The stratum germinativum (or basal layer, stratum basale) Consists of
single layer of basophilic columnar or cuboidal cells.
• Along with S. spinosum, it is a component of Malpighian layer
• Cells are bound to each other by desmosomes and to basal
lamina by hemidesmosomes.
• All cells contain intermediate keratin filaments, number of which
increases as cells progress upward.
• Also contain the dividing cells as in basale.
• Cells contain bundles of intermediate filament
(tonofilaments) projecting into the processses of cells which give
attachment to the desmosomes, so giving spined appearance.
• Tonofilaments provide resistant to the abrasion so this layer is
thicker in the areas prone to abrasion (thick skin) .
• Keratinization begins in the stratum spinosum.
• Consists of polygonal cells , cytoplasm of which is filled with
the basophilic granule , keratohyaline granules. It is rich in
phosphorylated histidine and cystine.
• Cells contain, lamellated bodies, made up of lipid. It fuses
with the cell membrane and it come out of cells and
function as a intercellular cement or sealing agent.
• This sealing effect is first evolutionary adaptation to
• More prominent in thick skin .Cellular organells and
nuclei are not prominent.
• It is composed of clear non-nucleated cells.
• In the palms and soles, the stratum
lucidum is present. The tan colored protein blocks the
underlying melanocytes from view
• The main difference between thick skin and thin skin relates
to the thickness of the Stratum corneum.
• These are the dead cells, flaking off. The cells lose their
nucleus and fuse to form squamous sheets, which are
eventually shed from the surface (desquamation).
• The mean turnover or renewal time of epidermis is 39
days(13+12+14) i.e.,time for a cell to move from the
stratum basale to the distal edge of the stratum corneum
• 13 days for proliferative compartment( lower two rows),12
days for differentiated compartment,14 days for cornified
• It is connective tissue that support the epidermis and attaches the epidermis
to the hypodermis.
• Dermis is 15-40 times thicker than the epidermis
• Its surface consists of many ridges (dermal papillae) which interdigitate with
• The dermis is also the area where all the glands of the body are located.
• Has 2 layers/compartments
1. A thin zone immediately beneath the epidermis (the papillary dermis) and
around adnexa ( the periadnexal dermis).The combination of papillary and
periadnexal dermis is called Adventitial dermis
2. A thick zone of Reticular dermis that extends from the base of the papillary
dermis to the surface of the subcutaneous fat
Papillary layer –The papillary dermis is the uppermost layer of the
dermis,composed of thin haphazardly arranged collagen bundles,delicate
branching elastic fibers,numerous fibrocytes,abundant ground
substance.A highly developed microcirculation composed of
arterioles,capillaries and venules
Its superior surface is uneven (fingerlike projections) which forms the
characteristic fingerprint of the finger. This layer provides the epidermis
with nutrients. Pain and touch receptors are found here
• Together,the papillary dermis and epidermis form a morphologic and
functional unit whose intimacy is reflected in their alteration jointly in
various inflammatory processes
• A similar interrelationship exists b/w periadnexal layer and its adjacent
• Dense irregular Connective Tissue
• Has thick bundles of Collagen and coarse Elastic fibers.Proportionally,
there are fewer fibrocytes and blood vessels and less ground substance
compared to papillary dermis
• Arrangement of bundle in the direction of mechanical force give rise to
the cleavage lines of Langer.
• Strongest layer of the Dermis.Gives the area strength.Contains
sweat,sebaceous glands and pressure receptors
• Leather is made of this layer.
•Consists of loose connective tissue which helps in sliding the skin over the
•Consists of layer of fat according to the nutritional status of the person.
•Also called as superficial fascia or panniculus adiposus
VESSELS IN SKIN
Arteries form the 2 plexuses. One at the junction of papillary and reticular
layer( sub- papillary plexus) and another at junction of dermis and hypodermis
Veins form the three plexuses – 2 in same position as for arterial and
another in the middle of the dermis
1. Sebaceous (oil) glands-Sebaceous glands are microscopic glands in
the skin which secrete an oily matter, called sebum, in the hair
follicles to lubricate the skin and hair. In humans, they are found in
greatest abundance on the face and scalp, though they are
distributed throughout all skin sites except the palms and soles. An
infection causes acne
2. Sweat (sudoriferous) glands - Sweat glands are exocrine glands, found
in the skin , that are used for body temperature regulation.
a) Eccrine glands -Eccrine glands (or merocrine glands) are found at
virtually all sites on the human body. They produce clear liquid
(perspiration), consisting of water, salts, and urea.
b) Apocrine glands- Apocrine glands are found in axillary and genital
areas, secrete a milky protein and fat substance. This mixture is an
excellent source of nutrients for bacteria which produce body odour.
• Follicle- A hair follicle is a part of the skin that grows hair by packing old cells together.
• Hair bulb
Arrector pili -Arrectores pilorum (singular Arrector pili) are tiny muscle fibers
attached to each hair follicle, which contract to make the hairs stand on end,
causing goose bumps. Arrectores pilorum are smooth muscle, not skeletal
muscle, which explains why humans cannot voluntarily give themselves goose
• Fingernails and toenails are made of a tough protein called keratin.
Along with hair and teeth they are an appendage of the skin.
• Free edge- The part of the nail that extends past the finger, beyond the
nail plate. There should always be a free edge present to prevent
• Nail folds (cuticle)- A fold of hard skin overlapping the base and sides of
a fingernail or toenail
• Nail Matrix- This is the only living part of the nail. It is situated behind
and underneath the Nail Fold and produces protein keratin which
makes up the Nail Plate.
PATCH AND BULLA
• PATCH IS A CIRCUMSCRIBED AREA OF
DISCOLORATION, GREATER THAN 2CMS
WHICH IS NEITHER ELEVATED OR
DEPRESSED RELATIVE TO THE
• BULLAE ARE RAISED, CIRCUMSCRIBED
LESION GREATER THAN 0.5 CM THAT
CONTAIN SEROUS FLUID
TUMOR and VESICLE
• TUMOR – is a solid, firm lesion about 2
cms in diameter that can be above,
level with or beneath the skin surface. It
is also called a mass.
• VESICLE – is a small , superficial
elevation of the skin, less than 0.5 cm,
that contains serous fluid.
PLAQUE AND PUSTULE
• PLAQUE IS A WELL-CIRCUMCRIBED,
ELEVATED, SUPERFICIAL, SOLID LESION,
GREATER THAN 1 CM IN DIAMETER
• PUSTULE IS A SMALL (1CM IN DIAMETER)
CIRCUMSCRIBED SUPERFICIAL ELEVATION
OF THE SKIN THAT IS FILLED WITH