???
• largest organ in the body (both in weight and surface area)
•show regional variation :
• ___%-___% of its total mass
• ___mm- 4___mm thick
• ___ mm; lower/ upper eyelids
• ___ mm; palms/ soles of the feet and upperback (hairless) • elastic & self-renewing
SKIN
• 15%-20% of its total mass
• 1.5mm- 4.0mm thick
• 1.5 mm; lower/ upper eyelids
• 4.0 mm; palms/ soles of the feet and upperback (hairless) • elastic & self-renewin
(6) FUNCTIONS OF THE SKIN :
The skin’s structure is made up of an intricate network which serves as the body’s initial barrier against pathogens, UV light, chemicals, and mechanical injury.
It also regulates temperature and the amount of water released into the environment.
Protective
Sensory
Homeostasis/Thermoregulation
Metabolic
Wound repair/Regeneration
Sexual Signaling
whAT FUNCTIONS OF THE SKIN?
o Physical barrier (pathogens, thermal and mechanical insults; structural integrity)
o Immunoregulatory (antimicrobial properties)
o Ultraviolet protection (melanin
o The skin contains millions of nerve endings that transport stimuli.
These nerve endings allow humans to detect sensation such as heat, cold, pain and pressure.
o is important because it provides heat conservation as well as heat loss depending on what is needed this is especially done by the fatty layer of the skin and hair on the head
o Endocrine (Cells in the skin synthesize Vitamin ____ which is needed in calcium metabolism and proper bone formation)
o Thousands of pores on the surface of the skin can absorb vitamins, acids, water and oxygen in order to provide moisture and nourishment to our skin.
o Excretion (excess electrolyte can be removed via sweat) o Subcutaneous layer stores significant amounts of energy in the form of fat
o Functions in excretion through sweat, sebaceous and apocrine gland
o Vitamin D3
o Elastic
o Self-renewing
o Healthy individuals, wound heals rapidly
o Physical appearance influenced by pigmentation which is provided by melanocytes, body contours and actinic damage
o Pheromones - sex pheromones are produced by _______ sweat glands and other skin glands for attraction
apocrine
LAYERS OF THE SKIN
EPIDERMIS
DERMIS
HYPODERMIS / SUBCUTIS
????
- Surface layer which is in contact with the exterior
- ___________ (bld supply?)
- ___________ (___________) (type of tissue? what embronic layer?)
- Avascular (bld supply?)
- Stratified squamous keratinizing epithelium (ectodermal) (type of tissue? what embronic layer?)
- Composed of different glands, nerves and blood vessels
- Inferior to the epidermis
- Vascular
- Dense irregular C.T. (mesodermal)
- Varying amounts of adipose connective tissue - Located below the dermis
- Presence of adipocytes
- Also known as _________
- Also known as Panniculus
• Outermost layer of the skin
• Keratinized, stratified squamous epithelium
• 0.4 to 1.5 mm thick
o Thin skin - 75 to 150 μm
o Thick skin - 400 to 1400 μm
• Cornification (formation of the outermost dead layer of the skin – stratum corneum)
o Synthesis of lamellar granules & distinctive proteins (keratins, filaggrin, involucrin)
o Alterations of nuclei, cytoplasmic organelles, plasma membranes, & desmosomes
• Cornification/Keratinization — Basal cells divide by mitosis and as they move upward the cells flatten and nucleus disappears
o Takes place within 28 days
LAYERS OF THE EPIDERMIS
STRATUM BASALE
STRATUM SPINOSUM
STRATUM GRANULOSUM
STRATUM LUCIDUM
o also known as stratum ___________ or ___________
o the deepest layer of the epidermis
o separated from the dermis by the basal lamina.
o The cells found in this layer are single layer of cuboidal to columnar mitotically active stem cells that are constantly producing _____. This layer also contains ____ (e.g. stem cells) and _____
Increased mitotic activity due to _______ cells present
o______________– cell attachment / cell junctions
o ________– attachment to the basement membrane zone (BMZ
o also known as stratum germinativum or Basal Cell Layer
o The cells found in this layer are single layer of cuboidal to columnar mitotically active stem cells that are constantly producing keratinocytes. This layer also contains melanocytes (e.g. stem cells) and merkel cells
Increased mitotic activity due to germinative cells present
o Desmosomes – cell attachment / cell junctions
o Hemidesmosomes – attachment to the basement membrane zone (BMZ
o also known as _________
o ______ rows of cell
o Numerous cytoplasmic extensions / spines
▪ Represent the sites where desmosomes are anchored to …………
▪ ______________
• Maintain cell cohesion
• Provide resistance to abrasions
• Terminate at various desmosome
o Polyhedral cells with “intercellular bridges”
o consists of desmosomes spines; represents the sites where desmosomes are anchored to tonofilaments – keratin intermediate filaments that maintain cell cohesion and provide resistance to abrasions
o consists of ________
o _______ cells present
o also known as prickle cell layer
o 4-6 rows of cell
▪ Represent the sites where desmosomes are anchored to tonofilaments
▪ Tonofilaments
o Polyhedral cells with “intercellular bridges
” o consists of desmosomes spines; represents the sites where desmosomes are anchored to tonofilaments – keratin intermediate filaments that maintain cell cohesion and provide resistance to abrasions
o consists of fillagrin
o Langerhans cells present
o _______ flattened cell layers
o also known as ________ cell layer
o consists of filaggrin and filled with coarse, basophilic (…….) granules.
▪ _________ granules are hygroscopic. It is the repeated cycles of hydration and dehydration. Results in the soft and flexible keratin.
o secretory granules not surrounded by a membrane
o Contains the cells that move above the spinosum and will accumulate dense basophilic
o Repeated cycles of hydration and dehydration contribute to the normal desquamation of the stratum corneum results in the softand flexible keratin
o 3-5 flattened cell layers
o also known as Granular cell layer
o consists of filaggrin and filled with coarse, basophilic (keratohyalin) granules.
▪ Keratohyalin granules are hygroscopic. It is the repeated cycles of hydration and dehydration. Results in the soft and flexible keratin.
o Hygroscopic
o Repeated cycles of hydration and dehydration
o Results in the soft and flexible keratin
KERATOHYALIN GRANULES
o Absent or diminished granular layer, hard and rigid keratin
Ichthyosis Vulgaris
o _____ flat cell layers
o present in thicker skin found in ___ and _____.
o translucent and barely visible.
o ____ (yes or nah?) nucleated cells with ______ granules
o Flat cells - contains densely packed …….
o filaments
o Contains densely packed keratin filaments
o tightly packed cells that lacks ___ or _____
o 2-3 flat cell layers
present in thicker skin found in soles and palms.
o non-nucleated cells with eleidin granules
▪ thick skin – palms and soles
o Flat cells - contains densely packed keratin
o tightly packed cells that lacks nuclear or organelles
o also known as the ___________ layer
o ______ cell layers
o ______
o it is the uppermost/ superficial layer of the epidermis
o Consists of flattened, dead cells filled with soft keratin filaments
o This is the layer which varies most in thickness, especially in callused skin.
o within this layer, the dead keratinocytes secrete ________ which are part of our first immune defense.
o continuous shedding (________)
o Cornified layer with cornified cells called ________
o Most differentiated cells in the skin it also responsible for the formation of calluses which is a reactive process
o Thick plasma membrane of the keratinized cells is coated from the outside in the deeper portion of this layer with extracellular layer of lipids that form the major constituent of the _____ barrier in the epidermis
o Layer that varies most in thickness
o Thickness of this layer constitutes the principal difference between epidermis of a thick and thin skin; thick and thin skin differs on the thickness of the skin
o Cornified layer may become even thicker at the site that are subjected to unusual amounts of friction as in the formation of calluses on the palms of the hands and on the fingertips.
o Callus formation is a reactive process
STRATUM CORNEUM
o also known as the cornified layer
o 20-30 cell layers
o anucleate
o within this layer, the dead keratinocytes secrete defensins which are part of our first immune defense.
o continuous shedding (desquamation)
o Cornified layer with cornified cells called squames
o Thick plasma membrane of the keratinized cells is coated from the outside in the deeper portion of this layer with extracellular layer of lipids that form the major constituent of the water barrier in the epidermis
o Accelerated differentiation of keratinocytes
o keratinocytes are typically produced and they differentiate at accelerated rates causing a slight thickening of the epidermis or epidermal layer and an increase keratinization and desquamation
o caused by overactive T lymphocytes triggering autoimmune reactions in the skin which can also lead to inflammation with redness irritation itching and scaling with a defective skin barrier
Psoriasis
o Atypical keratinocytes
o characterized by highly atypical cells at all levels of epidermis
o the disruption of the basement membrane results in a spread or metastasis of tumor cells to the lymph nodes
o known for variable differentiation patterns ranging from polygonal squamous cells arranged in orderly lobules in zones of keratinization to rounded cells with foci of necrosis and occasional single keratinized cells
Squamous Cell Carcinoma
is a combined layer of the Strata Basale, Spinosum, and Granulosum. It also constitutes the nucleated viable epidermis.
STRATUM MALPIGHI
BASIC SKIN CELL TYPES
• 3 Basic Cell Types
a. ________ – most abundant
b. ________– pigment - producing
c. ________ – antigen – presenting cells
• Additional Cells
d. ________ – tactile epithelial cells
e. ________
a. Keratinocytes – most abundant
b. Melanocytes – pigment - producing
c. Langerhan cells – antigen – presenting cells
d. Merkel Cells – tactile epithelial cells
e. Indeterminate dendritic cells
o most abundant in the epidermis
o squamous cells
o ______ in origin
o 80% of cells
▪ Tough and protective that separates the organism from the external environment
▪ Intermediate filaments about 10 nm in diameter. These keratin squames connect at their edges and in transverse sections form a folded basket-weave pattern called ____(). The squames are water repellent, in part because they are coated with lipid-containing anti-wetting agents synthesised during maturation in the granular layer
KERATINOCYTES
o ectodermal in origin
o Keratin
▪ Intermediate filaments about 10 nm in diameter. These keratin squames connect at their edges and in transverse sections form a folded basket-weave pattern called orthokeratosis (OK). The squames are water repellent, in part because they are coated with lipid-containing anti-wetting agents synthesised during maturation in the granular layer
o produces melanin, which is responsible for the dark brown pigment of the skin o Melanin also absorbs harmful UV rays and protect the skin from sun damage, also they:
• Synthesized from _____
• Dark color of the skin
MELANOCYTES
• Synthesized from tyrosine
SKIN COLOR
o Number, size, and distribution of Melanosomes = pigment granules within the keratinocytes
o Vascular pigments (_______ and _______)
o Dietary pigments (_______ and _______)
o Skin Color is not directly affected by melanocytes but rather by _______ which are within the _______.
o _______ Scale - as the number increases, so does the pigmentation
o Vascular pigments (oxyhemoglobin and deoxyhemoglobin)
o Dietary pigments (carotene and lycopene)
o Skin Color is not directly affected by melanocytes but rather by melanosomes which are within the keratinocytes. o Fitzpatrick Scale - as the number increases, so does the pigmentation
o UV light darkens the melanin and speeds up ____ synthesis, thus increasing melanin production. Also, pituitary ________ also influences pigmentation.
o Insufficient production of ___ by Adrenal cortex, so there is excess ______ produced which led to hyperpigmentation.
Addison Disease
o UV light darkens the melanin and speeds up tyrosinase synthesis, thus increasing melanin production. Also, pituitary Adrenocorticotropic hormone also influences pigmentation.
o Insufficient production of cortisol by Adrenal cortex, so there is excess ACTH produced which led to hyperpigmentation.
o Destruction of melanocytes
o Acquired condition
o Involves skin depigmentation often only in affected patches due to the loss or decrease activity of melanocytes. The causes of melanocytes loss are not clear, but they may include environmental, genetic, or autoimmune conditions.
Vitiligo
o Normal number of melanocytes but unable to synthesize melanosomes
o congenital disorder which produces skin hypopigmentation due to a defect in ________ or some other components of ________ producing pathway. You have a normal number of melanocytes but they are unable to synthesize the ________ .
Albinism
o congenital disorder which produces skin hypopigmentation due to a defect in tyrosinase or some other components of melanin producing pathway. You have a normal number of melanocytes but they are unable to synthesize the melanosome.
o Increased production of melanin by normal number of melanocytes
o lay term for ___ and _____ (both are flat macules) are the most important pigmentation characteristics observed in humans. But they differ significantly in development and morphology. Essentially, there's an increase production of melanin by a normal number of melanocytes
Freckles
o lay term for Ephelides and lentigines (both are flat macules) are the most important pigmentation characteristics observed in humans. But they differ significantly in development and morphology. Essentially, there's an increase production of melanin by a normal number of melanocytes
o Benign proliferation of melanocytes
o Increased number in melanocytes
Nevus
o Star shaped cells with numerous dendritic processes found in stratum _______
o Originate from the _______ , specifically form _______ . They migrate via the blood stream and reside in the skin mainly in the stratum ………..
These are antigen presenting cells are dendritic type cells and participate in the body's immune responses.
o Electron microsopy, well developed RER and Golgi complex, clear cytoplasm with rodlike inclusion: _______ granules ( _______ / _______ inclusion)
o Potent stimulators of _______ -cell mediated immunoreactions
LANGERHAN’S CELLS
o Star shaped cells with numerous dendritic processes found in stratum spinosum
o Originate from the bone marrow, specifically form melanocytes. They migrate via the blood stream and reside in the skin mainly in the stratum spinosum.
o Electron microsopy, well developed RER and Golgi complex, clear cytoplasm with rodlike inclusion: Birbeck granules (Rod/Racquet inclusion)
o Potent stimulators of T-cell mediated immunoreactions
o Found in stratum germinativum in association with intraepithelial nerve endings
o Palms, soles, infundibula, epithelium of nail beds, oral mucosa, genital regions
o EM: possess distinctive electron dense granules within their cytoplasm
o __________ (gentle touch)
▪ Most abundant in __________
o They are closely associated with the afferent or sensory unmyelinated axons
o Functions as …………. for cutaneous sensation particularly responding to gentle touch.
MERKEL’S CELLS
o Mechanoreceptors (gentle touch)
▪ Most abundant in fingertips
o Functions as mechanoreceptors for cutaneous sensation particularly responding to gentle touch.
o Maintenance of body homeostasis
o Established primarily by two factors:
o Deposition of insoluble proteins on the inner surface of the plasma membrane
o Lipid layer that is attached to the outer surface of the plasma membrane
EPIDERMAL WATER BARRIER
As keratinocytes in the stratum spinosum begin to produce keratohyalin granules, they also produce (2) :
• Lamellar bodies (membrane-coating granules)
• Probarrier lipids + lipid-processing enzymes
• _______ bodies (membrane-coating granules)
o Tubular or ovoid-shaped membrane-bound organelle
o Unique to mammalian epidermis
• Probarrier lipids + lipid-processing enzymes o assembled into lamellar bodies o Spinous and granular cells synthesize probarrier lipids and lipid processing enzymes including sphingolipids, phospholipids, ceramides, sphingomyelinase, and phospholipase o This mixture is assembled in lamellar bodies in Golgi apparatus o Lamellar bodies contain proteases o The contents of granules are secreted via exocytosis into the intercellular spaces between stratum granulosum and stratum corneum
Organization of these intercellular lipid lamellae is responsible for the formation of the epidermal water barrier has two structural elements:
o The cell envelope
o Lipid envelope
• a mature epidermis is an effective barrier which prevents dehydration from the loss of body water, poisoning from the absorption of noxious substances, and systemic infection from invading surface microorganisms to maintain homeostasis. • it resides within the most superficial layer of the skin, the stratum corneum.
BASEMENT MEMBRANE ZONES (BMZ) • junction between epidermis and dermis. aka(dermoepidermal junction or DEJ); right below the stratum basale. • contains specialized components which provide added adhesion to counteract disruptive external forces; it maintains tissue architecture and provides resistance.
Functions: o Attaches the epidermis to the dermis o Separates components of the epidermis and dermis o Provides resistance against external shearing forces o Maintains tissue architecture during remodeling and repair.
FOUR ZONES OF BMZ
1. HEMIDESMOSOME
2. LAMINA LUCIDA
3. LAMINA DENSA
4. SUBLAMINA DENSA
• attachment of cells to the extracellular matrix if of crucial importance in maintenance of tissue structure and integrity.
• Plasma membrane of the basal keratinocytes that constitute the upper boundary of the interface
• Plasma membranes of the basal cells with the specialized attachment plates
HEMIDESMOSOME
• found between the epidermis and dermis. Functions to bind epithelial cells to basement membrane.
• Electron-lucent region that lies beneath basal keratinocytes
• Portion of papillary dermi
LAMINA LUCIDA
• consists of lattice network of structural proteins. Main component is type IV collagen that provides added strength to the basement membrane.
• Electron-dense plate below lamina lucida & above papillary dermis
• a.k.a ______
LAMINA DENSA
• a.k.a basal lamina
• lies beneath the lamina densa
• fibrous components are present; anchoring fibrils, dermal microfibrils & collagen fibers
SUBLAMINA DENSA
TYPES OF COLLAGEN
• TYPE IV COLLAGEN
• TYPE VII COLLAGEN
TYPE OF COLLAGEN ?
o Major component of the basal lamina
o Most abundant
• TYPE IV (4) COLLAGEN
TYPE VII COLLAGEN
o Major component of the anchoring fibrils
o Predominantly localized to the epidermal basementnmembrane zone (EBMZ) within the lamina densa and sublamina densa
o Provides structural support and stability to EBMZ
TYPE VII (7) COLLAGEN
2 MAJOR HEMIDESMOSOMAL PROTEINS
o Both are basementmembrane proteins
o _______ (_______)
▪ autoantibody against this is thought to be secondarily produced.
▪ direct target of autoantibody because of its location along the basement membranes
o BP 230 (Bullous Pemphigoid Antigen 2)
o BP 180 (Bullous Pemphigoid Antigen 1 or Type VII/7 Collagen)
- a chronic blistering of the skin that ranges from mildly itchy welts to severe blisters & infection and may affect a small area or spreads all over the body. An autoimmune disorder
o Most common autoimmune subepidermal blistering disease of the skin, their antibodies produce against the BP 230 & BP 180 which are important membrane proteins in BMZ
o Usually, a disease of elderly with male predominance but can still occur in children presents as a generalized pruritic bullous eruption. Bullae are tense and develop on normal orerythematous skin
• BULLOUS PEMPHIGOID
___________ (antibodies against collagen ________)
- a rare autoimmune disease characterized by sub-epithelial blistering of the skin and mucosal membranes in response to injury
o In general, is a group of inherited disorders characterized by blister formation in response to mechanical trauma
o Slowly or poorly healing wounds
o They encompass defects in all areas of basement membrane
EPIDERMOLYSIS BULLOSA ACQUISITA (antibodies against collagen VII)
• is caused by unprotected long-term exposure to the sun's UV radiation. 3 major types of skin cancer that originates form the epidermal layer
SKIN CANCER
THREE MAJOR TYPES OF SKIN CANCER:
▪ Basal Cell Carcinoma
▪ Squamous Cell Carcinoma
▪ Malignant Melanoma
TYPE OF SKIN CANCER?
• Most common type, microscopically resemble cells form the stratum _______
• Slow growing tumor that usually does not metastasize. Typically, cancer cells arise from follicular bulge of the outer root sheath of the _______
Basal Cell Carcinoma
• Most common type, microscopically resemble cells form the stratum basale
• Slow growing tumor that usually does not metastasize. Typically, cancer cells arise from follicular bulge of the outer root sheath of the hair follicle
• Second most common • Usually develops a small painless nodule or a patch that issurrounded by an area of inflammation. • Characterized by highly atypical cells at all levels of the epidermis
• Most serious form of skin cancer if not recognized at an early stage
• Individual melanoma cells which originate from melanocytes will contain large nuclei with irregular contours and prominent eosinophilic nuclei. They aggregate in nest orscattered throughout the entire thickness of the epidermis.
• With time, melanoma will undergo a radial growth phase andt hey grow in all directions – upward in the epidermis, downward into the dermis & peripherally as well
• At early stage they tend not to metastasize but in the ___________ phase they will exhibit mitotic activity and will form round nodules that grow perpendicular to the surface of skin.
• By this time, melanocytes will display a little or no pigment in they usually start to metastasize to the original lymph nodes in vertical growth phase
Malignant Melanoma
• At early stage they tend not to metastasize but in the vertical growth phase they will exhibit mitotic activity and will form round nodules that grow perpendicular to the surface of skin.
• a deep layer forming a thick layer of dense connective tissue that constitutes the bulk of dermis
• collagen fibers have parallel orientation (____ lines or ____ lines) or skin tension lines thick collagen bundles arranges in orthogonal pattern
• has ____ (abundance) of fibrocytes
RETICULAR DERMIS
• has fewer fibrocytes
• collagen fibers have parallel orientation (Cleavage lines or Langer’s lines) or skin tension lines thick collagen bundles arranges in orthogonal pattern
• Thin zone immediately beneath/below the epidermis
• Haphazardly arranged collagen bundles
• highly irregular
• accounts for the whorls, loops and arches found on the tips of fingers
• composed of loose connective tissue that is highly vascular
• highly developed circulation made up mostly of capillaries
PAPILLARY DERMIS
• has a lot of fibrocytes
________ BLOOD SUPPLY
• the largest blood supply composed of arteries and veins that branch superficially into the middermis to form the cutaneous plexus.
• ________ function
• decrease/ increase blood flow in the papillary layer to minimize or facilitate heat loss
DERMAL BLOOD SUPPLY
Thermoregulatory function
TWO MAJOR PLEXUSES
1. SUBPAPILLARY PLEXUS
2.DEEP PLEXUS
____________ PLEXUS
• between papillary & reticular dermis
o Layers form which your capillary branches extend into the dermal papillae, and they form rich nutritive capillary network just below the epidermis
SUBPAPILLARY PLEXUS
PLEXUSES
___________ FUNCTION
• arteriovenous anastomoses or shunts and they are located between the two plexuses
o These shunts decrease blood flow into papillary layer to minimize heat loss or increase flow to facilitate heat loss depending on the need
o Lymphatic vessels begin at the dermal papillae and they converge to form two plexuses located within the blood vessel
THERMOREGULATORY FUNCTION
• near the interface of dermis and subcutis
o Larger blood and lymphatic vessel connection which at the interface of dermis and subcutaneous layer
DEEP PLEXUS
PRINCIPAL COMPONENTS OF DERMIS (2)
COLLAGEN
ELASTIC TISSUE
• family of fibrous proteins consisting of 15 types in human skin
• Major structural protein for the entire body found in tendons, ligaments and in the dermis
• Synthesized by fibroblasts
• Type _____ Collagen - major component of the dermis
• Collagen in papillary dermis is loosely arranged and highly irregular
• FUNCTIONS:
o stress-resistant material of the skin
o integrity, firmness, and elasticity
• Type 1 Collagen - major component of the dermis
• Minority of the dermis is made of …… tissue
• _______ for retractile properties of the skin also synthesized by fibroblasts
• its fibromatrix component is ……
• responsible for the retractile properties of the skin or the skin's elasticity
• synthesized by fibroblasts
• Elastin for retractile properties of the skin also synthesized by fibroblasts
• its fibromatrix component is elastin
– amorphous protein; fiber matrix component
o _______ dermis: thin and run at right angles to the skinsurface
o _______ dermis: thicker and oriented parallel to skin surface o Demonstrated/ Appreciated by _______ stain
ELASTIN
o Papillary dermis: thin and run at right angles to the skinsurface
o Reticular dermis: thicker and oriented parallel to skin surface o Demonstrated/ Appreciated by van Gieson stain
o Excessive collagen deposition
o _______ and hypertrophic scars are dermal form of fibroproliferative disorders that are caused by aberrant wound healing due to the injuries in the deep dermis
• KELOID
o Decreased expression of collagen
o …….. / _______ marks - form of dermal scarring and they are associated with the stretching of the dermis
o Often result from a rapid change in weight or can also be associated with endogenous or exogenous corticosteroids Proposed mechanisms are related to hormones, physical stretch, and structural alterations of dermal collagen and elastic tissue.
STRIAE
o Striae/ Stretch marks - form of dermal scarring and they are associated with the stretching of the dermis
o decreased elastin synthesis
▪ there is considerable increase in skin and ligament extensibility caused by defective collagen fibril processing
CUTIS LAXA
SKIN ____ ( ______ )
o Loss of collagen (____) and elastin (______)
o With age, there are changes in the dermal ECM; like the thickening of collagen fibers, less collagen synthesis, and the loss of hyaluronan and other glycosaminoglycans that will cause skin to hang loosely. Natural aging process is affected by exposure to the sun which is why doctors advise to avoid too much sun exposure. When you age, epidermis becomes thinner and more transparent.
SKIN AGING (Dermatophilosis)
o Loss of collagen (wrinkling) and elastin (sagging)
• Beneath the dermis is the ___ or ____ or __
o Layer rich of adipose tissues
o Deepest layer, derived from _______
o Lobules of adipocytes separated by _____
▪ Consists of adipose tissue, blood vessels & nerves
▪ Also contains sweat glands & bases of hair follicles
• Particularly thick in individuals who live in ______ climates
• This layer and its associated loose connective tissue constituting of hypodermis or subcutaneous facia, it is predominantly composed of adipose tissue in many areas it is separated by a _____________
• Repository of energy
• Endocrine organ
• _____ (body weight regulation)
• Conversion of _________ into ____ by ________
o This layer produces …… a hormone that regulates body weight via the ________.
SUBCUTIS/SUBCUTANEOUS/HYPODERMIS
• Beneath the dermis is the subcutis or hypodermis or panniculus
o Deepest layer, derived from mesenchyme
o Lobules of adipocytes separated by fibrous SEPTA
• Particularly thick in individuals who live in cold climates
• This layer and its associated loose connective tissue constituting of hypodermis or subcutaneous facia, it is predominantly composed of adipose tissue in many areas it is separated by a vertical fibrous septum
• LEPTIN (body weight regulation)
• Conversion of androstenedione into estrone by aromatase
o This layer produces leptin a hormone that regulates body weight via the hypothalamus.
o Inflammation of the adipose tissue
LOBULAR & SEPTAL PANNICULITIS
o Selective loss of body fat
LIPODYSTROPHY
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