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Histology > Skin > Flashcards

Skin Flashcards

1
Q

what is the average body weight in % of the skin?

A

16% - the skin is the heaviest organ of the body

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2
Q

what are the two layers that compose the skin?

A
  • superficial Epidermis layer
  • deeper Dermis layer

the layers interdigitate to form an irregular contour

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3
Q

what is the subcutis (hypodermis)?

A

the subcutis a layer deeper to the dermis and not part of the skin.
the subcutis consists of loose connective tissue that binds the skin to the subjacent tissue

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4
Q

what are the functions of the skin?

A
  1. protection against injury, desication and infection
  2. regulation of temperature
  3. absorption of UV radiation; synthesis of Vitamin D
  4. contains receptors for pain, touch and temperature
  5. waste excretion
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5
Q

what are the several appendages of the skin?

A

sweat glands, hair follicles, sebaceous glands and nails

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6
Q

what is the integument?

A

the integument is composed of the skin and its appendages

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7
Q

what is the epidermis?

  • embryonic origin
  • classification
A

the epidermis is the superficial layer of the skin.

the epidermis is of ectodermal origin

the epidermis is classified as stratified squamous keratinised epithelium

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8
Q

what are the layers of the epidermis?

A

there are 5 layers of the epidermis: (from superficial)

  • stratum corneum
  • stratum lucidum
  • stratum granulosum
  • stratum spinosum
  • stratum basale
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9
Q

what are the types of the cells that compose the epidermis?

A

the epidermis is composed predominantly of keratinocytes.

as well as: melanocytes, Langerhans cells, Merkel cells

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10
Q

how long does regeneration of the skin take?

how does it regenerate?

A

the skin constantly regenerates
the skin fully regenerates every 30 days
regeneration is carried our by the mitotic activity of karatinocytes, which normally divide at night

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11
Q

what are epidermal ridges?

A

epidermal ridges are deep downgrowths of the epidermis which interdigitate with projections of the dermis (dermal ridges), resulting in a highly irregular interface

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12
Q

what are dermal ridges?

A

dermal ridges are projections of the dermis that interdigitate with epidermal ridges of the epidermis.

dermal ridges are often subdivided into two secondary dermal ridges by a narrow downgrowth of the epidermis, called an interpapillary peg.

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13
Q

what are fingerprints?

A

fingerprints are surface ridges produced of epidermis overling the dermal ridges.

fingerprints are genetically determined and thus unique to individuals.

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14
Q

what is the stratum basale?

A

the stratum basale is the deepest layer of the epidermis and is composed of keratinocytes that are cuboidal to columnar in shape.

the keratinocytes are mitotically active cells attached to the basal lamina of the basement membrane by hemidesmosomes and to each other by desmosomes.

the stratum basale also contain melanocytes and merkel cells

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15
Q

what is the stratum spinosum?

A

the stratum spinosum consists of a few layers of polyhedral keratinocytes (prickle cells). their extensions (intercellular ridges) terminate in desmosomes.

the stratum spinosum contains langerhans cells
keratinocytes in the deepest aspects of the stratum spinosum are also mitotically active.

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16
Q

what is the stratum Malpighii?

A

the stratum malpighii or the malpighian layer is composed of the stratum basale and the stratum spinosum of the epidermis layer of the skin

17
Q

what is the stratum granulosum?

A

the stratum granulosum is the most superficial layer in which nuclei are still present.
it comprises of 3-5 layers of keratinocytes that contain keratohyalin granules

18
Q

what is the stratum lucidum?

A

the stratum lucidum is a clear, homogeneous layer just superficial to the stratum granulosum.
it is usually only present in thick skin
the layer contains cells that lack nuclei and organelles

19
Q

what is the stratum corneum?

A

the stratum corneum is the most superficial layer of the epidermis
the stratum corneum consists of 15-20 layers of flattened, nonnucleated dead ‘cells’ filled with keratin

the dead ‘cells’ are nonviable scalelike structures are called squames, 14-sided polygon

the outermost layer of squames is continuously shed by desquamation

20
Q

what is desquamation?

A

desquamation is the continuous shedding of the outermost layer of the epidermis of the skin

21
Q

what are the non-keratinocyte cells in the epidermis?

A
  • melanocytes
    • langerhans cells
    • merkel cells
22
Q

what are melanocytes?

  1. where in the epidermis are they present?
  2. function
A
  1. melanocytes are present in the stratum basale and originate from neural crest
  2. melanocytes synthesise a dark brown (melanin) pigment in oval shaped organelles (melanosomes). melanosomes contain tyrosinase a UV-sensitive enzyme directly involved in melanin synthesis
23
Q

what are langerhans cells?

  1. location
  2. function
A

langerhans cells are dendritic cells that originate in the bone marrow

they are located primarily in the stratum spinosum, containing paddle-shaped birbeck granules and function as antigen-presenting cells in immune responses to contact antigens and some skin grafts.

24
Q

what are merkel cells?

A

merkel cells are present in small numbers in the stratum basale, near areas of well-vascularised, righly innervated connective tissue.

merkel cells function as sensory mechanoreceptors, recieve afferent nerve terminals

25
Q

what is the dermis of the skin?

  • location
  • origin
  • composition
  • sublayers of the dermis?
A

the dermis of the skin is the layer underlying the epidermis.
the dermis of the skin is of mesodermal origin
the dermis of the skin is composed of dense irregular connective tissue that contains many type I collagen fibres and netwrok of elastic fibres
the dermis is subdivided into two non distinct layers:
- the dermal papillary layer
- the dermal reticular layer

26
Q

what is the dermal papillary layer?

- location
- composition
A

the dermal papillary layer is the superficial layer of the dermis. it is uneven and forms dermal ridges which interdigitate with the epidermal ridges.

ther dermal papillary layer is composed of thin, looselt arranged fibres and cells and contains capillary loops and meissner corpuscles which are fine-touch receptors

27
Q

what is the dermal reticular layer?

A

the dermal reticular layer is the deepest layer of the dermis and superficial to the hypodermis (not part of the skin)

the dermal reticular layer is the major portion of the dermis and is composed of dense bundles of collagen fibres and thick elastic fibres.
the deepest aspests of this layer may contain pacinian corpuscles, whcih are pressure receptors.

28
Q

what are the three types of glands found in the skin?

A
  1. eccrine glands
  2. apocrine glands
  3. sebaceous glands
29
Q

what are eccrine glands of the skin?

A

the eccrine glands are simple coiled tubular glands consisting of a secretory portion and a single duct.
they are present in skin throughout the body.

30
Q

what is the secretory unit of eccrine glands?

  • location
  • composition (3 cell types)
A

the secretory portion of the eccrine glands are found emedded in the dermis of the skin.
it is composed of three cell types:
1. dark cells: line the lumen of the gland and contain many micogen-righ secretory granules

  1. clear cells: underlie the dark cells and contain intercellular canaliculi that extend to the lumen of the gland. clear cells secrete a watery, electrolyte-rich material
  2. myoepithelial cells: lie scattered beneath the clear cells. they contract and aid expressing the glands secretions into the duct
31
Q

what is the duct unit of eccrine glands?

  • location
  • composition
A

the duct of eccrine sweat glands is narrow and lined by stratified cuboidal epithelial cells whcih contain keratin filaments and have a prominent terminal web.

the duct leads from the secretory portion to penetrate the interpapillary peg of the epidermis and spiral through its layers to deliver sweat to the outside.

as the secreted material pass through the duct, its cell resorb some electrolytes and excrete other substances (e.g. urea, lactic acid, ions)

32
Q

what are apocrine sweat glands?

A

apocrine sweat glands include large, specialised sweat glands in various areas of the body (e.g. axilla) and the ceruminous wax glands of the external auditory canal

these glands do not begin to function until puberty

their large coiled secretory unit are enveloped by scattered myoepithelial cells

these glands enter their vicous, odurless substance on hair follicles at a location superficial to the entry of sebaceous gland ducts. bacteria act on these secretions to produce odors.

apocrine secretions, like the name suggest, do not contain a portion of cytoplasm.

33
Q

what are sebaceous glands?

A

sebaceous glands are branched acinar glands having a lobular appearance. the cluster of acini of one sebaceous gland empty into a single short duct and then onto the neck of a hair follicle

sebaceous glands are embedded into the dermis over most of the body’s surface - absent in palms and soles.

sebaceous glands are holocrine glands that secrete sebum (an oily secretion that degenerates epithelial cells).

Histology (16 decks)

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