Micro quiz 11

what is integument?

skin+epidermal derivatives

what are 9 epidermal derivatives?

• Foot pads

-claws

• Hooves

• Horns

• Glands (including anal sacs)

• Uropygial gland (birds)

• Wattles and combs

• Spurs

-feathers

what are 7 functions of skin?

• Protection: a barrier against physical, chemical and biological agents

• Prevents water and electrolyte loss

• Temperature regulation

• Sensation

• Calcium homeostasis

• Energy storage

• Immune function

is skin the largest organ in the body?

yes

what are the 3 components of skin?

epidermis

dermis

hypodermis (subcutis)

what is the epidermis of skin?

stratified squamous keratinized epithelium

what are the 3 layers of the dermis?

papillary layer

reticular layer

what is the hypodermis?

loose connective tissue that may be rich in adipocytes

what call it if hypodermis rich in adipocytes?

panniculus adiposus

what is epidermis dervived from?

ectoderm

is epidermis vascular or avascular?

avascular

what is dermis derived from?

mesoderm

does the dermis support the epidermis?

yes

where are blood vessels and nervous tissue found in skin?

dermis

what is thick skin? 3 exs?

Thick hairless epidermis that contains merocrine/eccrine sweat glands

• Examples: paw pads, muzzle

what is thin skin?

Epidermis is thin and contains hair follicles often with arrector pili muscles and sebaceous glands and apocrine sweat glands

what gland type in thick skin?

merocrine/eccrine

what gland type in thin skin?

sebaceous glands and apocrine sweat glands

what are the 5 layers of the epidermis from outer to inner?

stratum corneum

stratum lucidum

stratum granulosum

stratum spinosum

stratum germinativum/basale

what is the dermo-epidermal junction?

Interface between the dermis and epidermis

what is epidermal pegs/ridges?

Downward projections of the deep epidermis into the dermis

what are dermal papillae?

Upward projections of the superficial dermis to increase surface area between both layers

what is function of dermal papillae?

Brings blood supply closer to the epithelium

what are 4 examples of the dermo-epidermal junction?

Footpads, nasal planum, scrotum and areas subjection to traction

where dermal papillae often not seen?

Not normally seen in haired skin

what are the 2 zones of the dermis? what tissues seen mainly in each?

Papillary = loose connective tissue within the dermal papillae

Reticular = dense irregular connective tissue

what 7 structures commonly found in dermis?

• Collagen fibres

• Elastic fibres

• Resident cells

• Transient cells

• Blood vessels

• Nerves

• Lymphatics

what is the most common cell in epidermis? how much of epidermis is this cell type?

keratinocytes

95%

what 3 non-karatinocytes seen in epidermis? function of each?

• Langerhans cells –immunity (tissue macrophage)

• Merkel’s cells-mechanoreception

• Melanocytes- UV protection

what cell junctions seen in epidermis to facilitate cell adherence? where seen?

• Desmosomes – between cells

• Hemidesmosomes – between basal cells and basal lamina

what occurs to cytoplasm of keratinocytes as get closer to surface?

cytoplasm replaces with keratin

do the flatten cells of the epidermis make it water proof?

yes

what epidermis layer is mitotically active?

stratum basale

what epidermis layer is capable of mitosis and cell division?

stratum spinosum

what epidermis layer is mitotically inactive?

stratum granulosum

what epidermis layer is deceased?

stratum lucidum and stratum corneum

where see stratum basale?

located at the epidermal-dermal junction

what epithelium arrangement is stratum basale?

Single layer of cuboidal to columnar epithelium

what attaches stratum basale to basal lamina?

hemidesmosomes

are both keratinocytes and melanocytes found in stratum basale?

yes

what does it mean that keratinocytes of the stratum basale are functionally heterogenous?

Some act as stem cells, whilst some function to anchor the epidermis

what do both desmosomes and hemidesmosomes connect to?

intermediate filaments

what do hemidesmosomes bind?

cells to basal lamina

what do desmosomes bind?

neighboring cells together

what are the shape of the cells in stratum spinosum?

polygonal

how many layers of cells in stratum spinosum in thick skin and thin skin?

• Thin skin: 1-2 cells-thick

• Thick skin: many layers thick

what give the cells of the stratum spinosum their spiny appearance?

increased number of tonofilaments (cytokeratin) and desmosomes

Cells of the stratum spinosum are c___ and they resist ___

Cells are cohesive and they resist abrasion

do cells of stratum spinosum maintain some capacity for division?

yes

what is the last living layer of the epidermis?

stratum granulosum

how many cell layer sin stratum granulosum?

3 to 5

what do cells of stratum granulosum contain?

basophilic keratohyalin granules and lamellar granules

what layer of epidermis do the cells start to flatten?

stratum granulosum

what is function of lamellar bodies in cells of stratum granulosum?

secreted by cells to form waterproof lipid sheets, “intercellular cement”

where is stratum lucidum only present?

only in thick skin

are cells fully keratinized in stratum lucidum?

yes

what epidermal layer is translucent?

stratum lucidum

what 2 structures are abundant in stratum lucidum?

keratin filaments

desmosomes

what does the cytoplasm of cells of stratum lucidum produce?

eleidin

what is eleidin?

a protein chemically related to keratin

what is the outermost epidermal layer?

stratum corneum

how many layers is stratum corneum?

depends on location but can be up to 20 layers thick

what do the cells of the stratum corneum made of?

keratin only

do cells of stratum corneum have organelles?

no organelles

are the cells at the surface of the stratum corneum constantly shed?

yes

is keratin water resistant?

yes

what is keratinization?

Process by which keratinocytes

differentiate, about 21 days in length in the dog

what is cornification?

Production of stratum corneum by terminal epidermal differentiation