• Skin is the largest organ of the human body accounting for 15 to 20% of total body
weight.
• Also known as INTEGUMENT or CUTANEOUS LAYER, it is composed of:
◦ Epidermis- Epithelial cells
derived from Ectoderm. Which gives
rise to
‣ Hair
‣ Nails
‣ Sebaceous and Sweat Glands
◦ Dermis- Cells derived from
Mesoderm
◦ Dermal Papillae- between the two
laters. containing epidermal
ridges which strengthen the bond
between the two layers.
• Beneath the Dermis there is the
SUBCUTANEOUS TISSUE or HYPODERMIS
which is loose connective tissue
containing PADS OF ADIPOCYTES. It
Binds Skin to underlying tissues
producing the Superficial Fascia.
Ep- Epidermis
De- Dermis
BV- blood vessels
PC- Pacinian Corpuscules
SG- sweat glands
The Functions of Skin:
Protection
• Physical and Chemical Barrier that provides defense against
◦ Microbes
◦ Friction
◦ Suns UV rays
Sensory
• Various sensory receptors allow body to monitor the environment and regulate body's
interactions with physical objects
Thermoregulatory
• Keeps body's temperature in homeostasis by insulating substances such as hair and
adipose deposits by accelerating heat loss through sweating
Metabolic
• Synthesizes Vitamin D3
• Removes excess electrolytes through sweat
•Stores Energy as Fat
Sexual Signaling
• Visual indictor of health(hair, complexion) which is involved in attraction
• Sex pheromones produced by apocrine glands are excreted through sweat
Dermatoglyphs or fingerprints are interdigitations/sulci between dermis and
epidermis, which form an unique pattern of loops, arches and whorls for each
individual.
• Skin is Elastic and can stretch to accommodate swollen areas
• Self Renewing and Rapidly repairable
, EPIDERMIS:
• Consists of Stratified Squamous Keratinized Epithelia
composed of:
a. Keratinocytes
b. Melanocytes- pigment cells
c. Langerhans Cells- antigen presenting macrophages
d. Merkel Cells- tactile epithelial cells
• Epidermis is AVASCULAR, it receives its nourishment by
diffusion through Dermis.
• Thick Epidermis 400 to 14000μm(1.4mm) on palms and soles
• Thin Epidermis 75 to 150μm
Epidermis Consists of 4 layers or Strata of Keratinocytes:
• Basal Layer or Stratum Basale or Stratum Germinativum
◦ Single Layer of tightly packed Basophilic cuboidal or
columnar epithelial cells knows as Keratinocytes
◦ Keratinocytes are attacked to Basal membrane/lamina
by Hemidesmosomes and are attached to each other by
Desmosomes
◦ Keratinocytes have Oval Nuclei that show Intense
Mitotic Activity containing progenitor cells for
other Epidermal layers
◦ Contains Keratins which are 10nm dimeter Intermediate
Filaments
◦ Melanocytes and Merkel Cells are also found
• Spinous Layer or Stratum Spinosum
◦ The thickest layer
◦ Polyhedral Cells with prominent Nuclei and Nucleoli
that become flatter as they approach the surface.
◦ Active Cytoplasms synthesizing Keratins
◦ Keratin fibers are assembled into
Tonofibrils that converge and terminate on
desmosomes holding the cell layers together
◦ Langerhans Cells are found here
The Basal and Spinous layers together are called
STRATUM GERMINATIVUM or The Malphigian Layer
• Granular Layer or Stratum Granulosum
◦ Composed of THREE to FIVE layers of
flattened cells
◦ Cells undergo terminal differentiation of
KERATINIZATION
◦ Basophilic Keratohyline Granules fill the
Circle- Desmosome
cytoplasm Arrow- Hemidesmosome
◦ Dense Non-membrane bound masses of
FILAGGRIN, associated with
Tonofibrils
◦ Golgi-derived LAMMELAR
GRANULES, which are composed of
various glycolipids are
exocytosed and produce a lipid
rich membrane around the cell
which serves to: Prevent water
loss Physical Barrier
• Pale Layer or Stratum Lucidum
◦ Translucent slightly
eosinophilic layer
◦ Only found in Thick Skin with a
lot of cytoplasmic Keratin
Filaments
◦ Tightly packed squamous cells
that contain no nuclei or
organelles
• Corneal Layer ot Stratum Corneum
◦ 15 to 20 layer of Squamous
Keratinized Cells or SQUAMES
which are flat and Anucleated
‣ Keratin Replaces the cytoplasm in these cells
◦ Shed continuously and protects against FRICTION and WATER LOSS- Desquamation
weight.
• Also known as INTEGUMENT or CUTANEOUS LAYER, it is composed of:
◦ Epidermis- Epithelial cells
derived from Ectoderm. Which gives
rise to
‣ Hair
‣ Nails
‣ Sebaceous and Sweat Glands
◦ Dermis- Cells derived from
Mesoderm
◦ Dermal Papillae- between the two
laters. containing epidermal
ridges which strengthen the bond
between the two layers.
• Beneath the Dermis there is the
SUBCUTANEOUS TISSUE or HYPODERMIS
which is loose connective tissue
containing PADS OF ADIPOCYTES. It
Binds Skin to underlying tissues
producing the Superficial Fascia.
Ep- Epidermis
De- Dermis
BV- blood vessels
PC- Pacinian Corpuscules
SG- sweat glands
The Functions of Skin:
Protection
• Physical and Chemical Barrier that provides defense against
◦ Microbes
◦ Friction
◦ Suns UV rays
Sensory
• Various sensory receptors allow body to monitor the environment and regulate body's
interactions with physical objects
Thermoregulatory
• Keeps body's temperature in homeostasis by insulating substances such as hair and
adipose deposits by accelerating heat loss through sweating
Metabolic
• Synthesizes Vitamin D3
• Removes excess electrolytes through sweat
•Stores Energy as Fat
Sexual Signaling
• Visual indictor of health(hair, complexion) which is involved in attraction
• Sex pheromones produced by apocrine glands are excreted through sweat
Dermatoglyphs or fingerprints are interdigitations/sulci between dermis and
epidermis, which form an unique pattern of loops, arches and whorls for each
individual.
• Skin is Elastic and can stretch to accommodate swollen areas
• Self Renewing and Rapidly repairable
, EPIDERMIS:
• Consists of Stratified Squamous Keratinized Epithelia
composed of:
a. Keratinocytes
b. Melanocytes- pigment cells
c. Langerhans Cells- antigen presenting macrophages
d. Merkel Cells- tactile epithelial cells
• Epidermis is AVASCULAR, it receives its nourishment by
diffusion through Dermis.
• Thick Epidermis 400 to 14000μm(1.4mm) on palms and soles
• Thin Epidermis 75 to 150μm
Epidermis Consists of 4 layers or Strata of Keratinocytes:
• Basal Layer or Stratum Basale or Stratum Germinativum
◦ Single Layer of tightly packed Basophilic cuboidal or
columnar epithelial cells knows as Keratinocytes
◦ Keratinocytes are attacked to Basal membrane/lamina
by Hemidesmosomes and are attached to each other by
Desmosomes
◦ Keratinocytes have Oval Nuclei that show Intense
Mitotic Activity containing progenitor cells for
other Epidermal layers
◦ Contains Keratins which are 10nm dimeter Intermediate
Filaments
◦ Melanocytes and Merkel Cells are also found
• Spinous Layer or Stratum Spinosum
◦ The thickest layer
◦ Polyhedral Cells with prominent Nuclei and Nucleoli
that become flatter as they approach the surface.
◦ Active Cytoplasms synthesizing Keratins
◦ Keratin fibers are assembled into
Tonofibrils that converge and terminate on
desmosomes holding the cell layers together
◦ Langerhans Cells are found here
The Basal and Spinous layers together are called
STRATUM GERMINATIVUM or The Malphigian Layer
• Granular Layer or Stratum Granulosum
◦ Composed of THREE to FIVE layers of
flattened cells
◦ Cells undergo terminal differentiation of
KERATINIZATION
◦ Basophilic Keratohyline Granules fill the
Circle- Desmosome
cytoplasm Arrow- Hemidesmosome
◦ Dense Non-membrane bound masses of
FILAGGRIN, associated with
Tonofibrils
◦ Golgi-derived LAMMELAR
GRANULES, which are composed of
various glycolipids are
exocytosed and produce a lipid
rich membrane around the cell
which serves to: Prevent water
loss Physical Barrier
• Pale Layer or Stratum Lucidum
◦ Translucent slightly
eosinophilic layer
◦ Only found in Thick Skin with a
lot of cytoplasmic Keratin
Filaments
◦ Tightly packed squamous cells
that contain no nuclei or
organelles
• Corneal Layer ot Stratum Corneum
◦ 15 to 20 layer of Squamous
Keratinized Cells or SQUAMES
which are flat and Anucleated
‣ Keratin Replaces the cytoplasm in these cells
◦ Shed continuously and protects against FRICTION and WATER LOSS- Desquamation
