Integument II Flashcards
How thick is the dermis
0.5 to 3 mm thick
Dermis corresponds to _______ of a mucous membrane
lamina propria
Synonyms for Subcutaneous tissue
- Sub Q
- Superficial fascia
- Hydodermis
What is directly related to finger prints
Primary dermal ridge
Primary dermal ridge is found everywhere except
forehead, external ear, perineum, and scrotum
Primary dermal ridges are formed during
3rd to 4th months of fetal life
Primary dermal ridges are subdivided into
two secondary ridges by interpapillary peg
What is the interpapillary peg
- It is a downward growth along the crest
- subdivides primary dermal ridge into two secondary dermal ridges
Secondary dermal ridges occur in ______ rows, Branched
double
Composition of the secondary dermal ridges
Thin collagenous, reticular, and elastic fibers
What are dermal papillae
upward projections from each secondary dermal ridge
Functions of the integument
- protection from mechanical injury
- Prevents desiccation
- Protects against foreign substances and microorganisms
- Protects against UV radiation
- Thermoregulation
- Regulation of blood pressure (via dermal capillary network)
- Excretion of metabolic waste products
- Synthesis of Provitamin D
Integument regulates blood pressure via
dermal capillary network
Thick and thin skin refers to the _______ only
epidermis
Characteristics of thick skin
- Occurs only on palm and soles and is HAIRLESS
- epidermis varies from 0.4 to 0.6 mm thick
- Displays all five epidermal layers
Characteristics of thin skin
- Occurs everywhere except for palms and soles
- epidermis varies form 75 to 150umm thick
- Thinnest skin is on the eyelids
- thickest thin skin is on the back
- thicker on extensor surfaces than flexor surfaces
- epidermal layers less distinct and lacking stratum lucidum
Where is the thinnest thin skin
eyelids
Where is the thickest thin skin
on Back
Epidermal layers of thin skin are _____ and lacking _______
less distinct, stratum lucidum
Epidermis is derived from
embryonic ectoderm
Layers of epidermis (from deepest to most superficial)
- Stratum basal (germinativum)
- Stratum spinosum (Stratum Malpighi)
- Stratum Granulosum
- Stratum lucidum
- Stratum corneum
Langerhans cells are found in what epidermal layer
Stratum spinosum (Stratum Malpighi)
The stratum lucidum is absent in
thin skin
in thin skin the stratum granulosum is represented by
only a few cells
Melanocytes originate in the _____ and are visible form the _____ embryonic week
neural crest, 8th
Characteristics of stratum Basale (germinativum)
- Deepest
- Columnar to high cuboidal keratinocytes
- Keratins 5 and 14 (low-molecular weight keratins)
- Single layer of cells
- Held together by desmosomes
- Hemidesmosomes hold layer to basal lamina
- High mitotic activity
- mitotic activity produces stem cells differentiating keratinocytes
- Affected by chemotherapeutic and radiation treatments
Characteristics of Stratum Spinosum
- Polyhedra-shaped cells (prickle cells)
- Keratins 1 and 10 (high molecular weight keratins)
- Keratohyalin granules develop
- Membrane-coating granules first appear
- Lamellar bodies
- Contain lipid, carbohydrate, and hydrolytic enzymes - Tonofibrils
- Form intercellular bridges
Characteristics of Stratum Granulosum
- Multilayered
- Keratins 2e and 9
- Flattened nucleated keratinocytes
- Keratohyalin aggregates:
- Fillagrin induces cross-linkage of keratin filaments by disulfide bonds
- no limiting membrane
- Fillagrin induces cross-linkage of keratin filaments by disulfide bonds
- Membrane-coating granules (lamellar bodies)
- Acylglucosylceramide—> intercellular spaces - Tonofilaments
General Organization of the Integument
- Epidermis
- Basement membrane
- Dermis
- Subcutaneous tissue
- Epidermal Ridges
What keratins are in the stratum basal (Germinativum)
Keratins 5 and 14 (low-molecular weight keratins)
Keratin-containing intermediate filaments that form intercellular bridges in the stratum spinosum
Tonofibrils
What are Lamellar bodies
- Membrane-coating granules that first appear in the stratum spinosum but are also present in the stratum granulosum
- Contain lipid, carbohydrate, and hydrolytic enzymes
Lamellar bodies contain
-lipid, carbohydrate, and hydrolytic enzymes
What keratins are present in the stratum granulosum
keratins 2e and 9
What keratins are present in the Stratum spinosum
Keratins 1 and 10 (high molecular weight keratins)
in what layer of the epidermis do keratohyalin granules develop
Stratum spinosum
Stratum lucidum
- Flat keratinocytes lacking nuclei and organelles
- only found in thick skin
- contains eleiden
Stratum Corneum
- Multilayered (5-50 layers)
- Thicker in thick skin
- Enucleated, flattened, dead keratinocytes
- Cytoplasm replaced by keratin
- cytoplasm contains:
- keratin cross-linked with filaggrin
- cornfield cell envelope
Keratin in the stratum corneum is cross-linked with
Filaggrin
The cornified cell envelope has a ____ and ____ component
- extracellular
- multi-lamellar lipid layer covalently linked to involucrine
- intracellular
- Involucrine
- Small proline-rich proteins
- Loricrin
- Fillagrin and keratin complexes
induces the aggregate of keratins
Filaggrin
mutation of Keratin 1 and keratin 10 is caused of
Epidermolytic hyperkeratosis (EHK)
Mutation of Keratin 5 and 14 is the cause of
epidermolysis bullosa simplex (EBS)
Defects in keratin 2e cause
ichthyosis bulls of Siemens (IBS)
A defect of keratin 9 is associated with
epidermolytic palmoplantar keratoderma (EPPK)
a specialized structure that reinforces the plasma membrane of keratinocytes
cornfield cell envelope
Keratinization
- ) lipids covalently linked to involucrin, thus contributing to the formation of the epidermal permeability barrier.
- ) The cornfield cell envelope is a specialized structure that reinforces the plasma membrane of keratinocytes when they reach their final stage of differentiation. it consists of aggregates of keratins and filaggrin and a complex of three proteins: involucrin, small proline-rich proteins (SPRs), and loricrin, cross-linked by the enzyme transglutaminase K (TGK)
- ) Keratin filaments, aggregated by filaggrin, interact with the inner side of the plasma membrane to form the cell envelope
- ) Tight junctions in the stratum granulosum, containing claudin-1 and claudin-4 are components of the permeability barrier
Dermis characteristics
- Dense fibrous irregular CT layer beneath epidermis
- Derived form Embryonic mesoderm
- Induces development of epidermis and epidermal derivatives
- Supports epidermis
Hypodermis characteristics
- Loose CT that underlies dermis
- Corresponds to superficial fascia of gross anatomy
- Technically not part of skin
- May contain fat cells that can form a thick layer called the panicles adiposus
What are the two layers of the dermis
- Papillary layer (closest to the epidermis)
- Reticular layer
Composition of the papillary layer of the dermis
- Closest to the epidermis
- Loose CT
- Separated form epidermis by basal lamina
- Network of fine elastic fibers and abundant capillaries
The papillary layer is separated form the epidermis by the
basal lamina
Composition of the Reticular layer of the dermis
- Dense irregular CT
- Includes fibrocytes, macrophages, and adipocytes
Langerhans cells
- dendritic cells
- Derived from monocytes
- Antigen-presenting cells
- primarily in the stratum spinosum
- Migrate from epidermis to lymph nodes
- Birbeck granules
Langerhans cells interact with keratinocytes through
E-Cadherins on their surface
Birbeck granules
Found in langerhans cells
contain the proteins langerin and CD1a (cell surface marker), involved in the uptake and delivery of antigens
Merkel Cells
- Mechanoreceptors
- May also act as diffuse neuroendocrine cells
- Usually in stratum germinative (basale)
- Contain catecholamine-like granules
Melanocytes
- Derived from melanoblasts
- Do not form desmosome attachements in epidermis
- Inject melanin granules into keratinocytes
- Pathway for melanin formation:
- Tryrosin–> 3,4-dihydroxyphenylalanine (DOPA) –> dopaquinone–> melanin
- Requires tyrosinase
What is the pathway for melanin formation
- tyrosin—> 3,4 dihydroxyphenylalanine (DOPA)—> dopaquinone—> melanin
- * requires tyrosinase***
Development of the integument
- Epidermis starts as a single layer of ectodermal cells
- divide during the sixth week to form:
- Periderm
- Sloughs off to form vernix caseosa
- Inner cuboidal germinal layer:
- Continues to proliferate to form adult layers of the epidermis and derivatives:
- 10 weeks: fingernails
- 12 weeks: Hair buds and toenails
- Periderm
- divide during the sixth week to form:
- Dermis is derived from mesoderm
Tactile receptor present in dermal papilla
Meissner’s corpuscle (note that they are present in fingers, hand, foot, front of forearm, lips, and tongue)
Merkel cells are usually located in
The stratum Germinativum
Do melanocytes form desmosome attachments in epidermis
No
