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Histo, Anat & Physiol > Skin > Flashcards

Skin Flashcards

1
Q

The Integument

A
  • The Integument system accounts for 16% of body weight
  • Is composed of the cutaneous membrane and accessory structures
  • Skin
  • Hair (accessory structures)
  • Sweat glands (accessory structures)
  • Nails (accessory structures)
  • Cutaneous membrane-Epidermis/Epithelium and Dermis/CT
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2
Q

Functions of Skin

A
  • Protection of underlying organs from dehydration, infection, abrasion, UV damage and cold/heat
  • Maintenance of normal body temperature through insulation or evaporative cooling
  • Synthesis of Vitamin D3
  • Excretion of water, salts and oils
  • Production of melanin to protect underlying tissue from UV radiation
  • Production of keratin which repels water and protects against abrasion
  • Sensory Perception at the tactile receptors and free nerve endings
  • Energy Storage (of lipid) in adipocytes in the dermis and in adipose tissue in the subcutaneous layer
  • Coordination of immune response to pathogens and cancers in the skin
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3
Q

Cutaneous membrane

A
  • Is skin, surface of the body
  • Thick, relatively waterproof, and dry
  • Epithelium in epidermis and CT in the Dermis
  • CT connects epith to underlying
    structures
  • Loose Aerolar first and then dense irreg CT proper
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4
Q

Skin Histology- layers

A
  1. Epidermis– keratinised stratified squamous epithelium, basement membrane (supported by areolar CT of dermis)
  2. Dermis– composed of loose areolar CT and dense irregular CT proper with accessory structures
  3. Hypodermis or subcutaneous layer (loose CT proper). (aka superficial fascia)
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5
Q

Types of skin cells

A

There are 3 main types of cells in the epidermis:
* Squamous cells: These are flat cells in the outer/superficial part of the epidermis that are constantly shed as new ones form
* Basal cells: These cells are in the lower/deeper part of the epidermis, called the basal cell layer
* Melanocytes: These cells make the brown pigment called melanin, which gives the skin its tan or brown colour. Melanin acts as the body’s natural sunscreen
* The epidermis is separated from the deeper layers of skin by the basement membrane
* When a skin cancer becomes more advanced, it generally grows through this barrier and into the deeper layers
* Epidermis may also have cells of the immune system and sensory nerve cells

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6
Q

Thick skin

A

on the palms of the hand and soles of the feet (5 epidermal layers) (0.5mm)

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7
Q

Thin skin

A

on the rest of the body (4 epidermal layers) (0.08mm)

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8
Q

The Epidermis

A

*Stratified squamous epithelium (keratinised)
*Epithelial cells called Keratinocytes
*4 or 5 layers
*Difficult to distinguish with light microscope
*Gives skin properties of water resistance; protection from microorganisms and abrasion; gland secretions; support some sensory cells
*Blister– water trapped between layers
*The fingerprint is a pattern of Epidermal ridges
*These ridges increase the surface area for contact between the epidermis and dermis and have a unique pattern

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9
Q

Layers of the Epidermis

A

Cover or Lets Get Sun Burned!!
1. Stratum Corneum
2. Stratum Lucidu
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Basale or stratum germinativum
There are tight connections between the cells that leads to loss as sheets of skin.

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10
Q

Stratum Corneum

A

has 15–30 rows of flat, dead cells completely filled with keratin. This layer is continually shed and replaced

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11
Q

Stratum Lucidu

A

only found in thick skin of the palms and soles. They are flat
densely packed cells

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12
Q

Stratum Granulosum

A

has 3–5 rows of flattened cells with degenerating nuclei.
These cells produce keratin

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13
Q

Stratum Spinosum

A

has 8–10 rows of polyhedral cells tightly packed

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14
Q

Stratum Basale or stratum germinativum

A

the deepest layer; has stem cells that continually divide. Some cells move to the surface – squamous cells. Others give rise to sweat or oil glands. Melanocytes may be found in this stratum

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15
Q

The Dermis

A
  • Between epidermis and subcutaneous layer
  • A connective tissue layer containing collagen and elastin fibres to support:
    -blood vessels
    -nerves
    -glands
    -hair follicles
  • adipocytes
  • The dermis is subdivided into the outer Papillary region and the inner Reticular region
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16
Q

Papillary Region (Dermis)

A

-Loose areolar CT (elastin)
-Loops of capillaries (thermoregulation), lymphatic vessels, sensory nerve fibres
-Meissner’s corpuscles (touch receptors)
-Is ridged

17
Q

Reticular Region (Dermis)

A
  • Dense irregular CT proper (collagen and elastin)
    -Thickness varies
    -Network of fibres
    -Spaces occupied by adipose tissue, hair follicles, nerves and oil glands and ducts of sweat glands
  • This reticular region enables the skin to be:
    -Strong
    -Extensible (stretchy in pregnancy, oedema and obesity)
    -Elastic (return to original shape after stretch or contraction)
  • The reticular region is attached to the underlying organs, such as bone and muscle, by the subcutaneous layer (superficial fascia)
18
Q

The Skin and Water Loss

A
  • The outermost layer of skin is water-resistant (not waterproof)
  • 0.5L of water migrate through the epidermis and is lost by evaporation -> this is called insensible perspiration
  • Sweating leads to additional fluid loss (and electrolyte loss). Sweating is varied as required for core temperature regulation called sensible perspiration.
19
Q

Subcutaneous Layer

A
  • Also called hypodermis or superficial fascia
  • Lies deep to the dermis
  • Connects the skin to the underlying tissue
  • The CT of the dermis and subcutaneous layers are interwoven
  • Quite elastic, consists primarily of adipose tissue
  • Functions to allow independent movement, as an energy store and to insulate the body
  • Subcutaneous layer has sensory nerve endings called lamellated or
    Pacinian corpuscles that are sensitive to touch (pressure and vibration)
20
Q

Subcutaneous fat deposition

A
  • NB in babies for insulation
  • Hormone dependant (puberty)
  • Varies in location; with:
    -None on backs of hand and top of feet
    -Pear or apple shape body
  • Fat deposits in the body are:
    -Subcutaneous
    -Visceral
    -Interscapular
  • Adipose tissue may be white or brown
21
Q

Skin Sweat (Sudoriferous) Glands

A

Apocrine Sweat Glands
Merocrine/eccrine Sweat Glands

22
Q

Apocrine Sweat Glands

A
  • Simple branched tubular glands.
  • Only found in axilla, pubic region
    and areolae of breast.
  • Secretary portion in dermis or
    subcutaneous.
  • Excretory duct opens into hair
    follicle.
  • Begin to function at puberty
  • Viscous secretion
23
Q

Merocrine/eccrine Sweat Glands

A
  • Coiled tubular gland
  • distributed widely in body (NB soles and palms)
  • Secretary portion in subcutaneous
    layer
  • Excrete onto surface
  • Functions include:
  • Cooling surface of skin; excreting
    water and electrolytes; protection
    from environmental hazards
24
Q

Skin Sebaceous (oil) glands

A
  • Holocrine glands
  • Discharge oily lipid secretion into hair follicles
  • Produce sebum
25
Q

Ceruminous glands

A
  • Modified sudoriferous (sweat) glands
  • Simple, coiled tubular glands
  • Present in the auditory canal (ear)
  • Secretory portion in subcutaneous layer
  • Excrete onto surface or into sebaceous glands.
  • Combined secretions of sebaceous and ceruminous glands give rise to ear wax (cerumen)
  • Function (along with hairs) to prevent entrance of foreign bodies, preventing them reaching the ear drum
26
Q

Mammary glands

A
  • Anatomically related to Apocrine glands
  • Development and secretion controlled by interaction between sex hormones and pituitary hormone
27
Q

Nervous Control of Secretion of Glands

A
  • Sebaceous and Apocrine -> collectively turned on/off by Autonomic Nervous System (e.g. in stressful situations)
  • Merocrine → areas of the body selectively turned on (sweaty hands) or all activated by ANS
  • During thermoregulation to cool the body all merocrine glands switched on
    -Thermoregulation is the homeostatic process of maintaining temperature
28
Q

Factors of Skin Colour

A
  • Melanin in the epidermis
  • Carotene in the dermis and epidermis
  • Capillaries in the dermis
29
Q

Melanin

A
  • Produced by melanocytes
  • Amount varies to give skin colour from pale yellow to black
  • Found in basale and spinosum layers
  • Synthesised in melanocytes of stratum basale
  • Total absence of melanocyte activity results in Albinism
  • Patchy absence of melanocyte activity results in Vitilgo
  • Patchy production of melanocytes results in freckles
30
Q

Carotene

A
  • Orange-yellow pigment that normally accumulates in epidermal cells
  • Found in stratum corneum and fatty areas of the deep dermis and subcutaneous layer
  • Together with melanin, carotene gives yellowish hue to their skin
  • Carotene also found in vegetables
  • Carotene → Vitamin A
  • Essential for maintenance of epithelia
  • Photoreceptor pigments in the eye
31
Q

Capillaries

A
  • Caucasian Skin Colour
  • Due to blood capillaries in the dermis
  • Redness not masked by pigments
  • Port wine stain – unusual dense
    collection of blood vessels in the dermis
32
Q

The Epidermis and Vitamin D3

A
  • Limited exposure to sunlight is very beneficial
  • UV light on the stratum spinosum and basale result in Vit D3 production
  • 7-dehydrocholesterol is converted to Vit D3 or cholecalciferol in the skin
  • In the Liver this is converted to 25-hydroxy-D3
  • This then is converted to calcitriol, the active form of the vitamin, in the kidney
  • Calcitriol is essential for Ca++ and PO4- absorption from the GIT
  • Deficiency in Vit D result in abnormal bone development in children (Rickets) and (Osteomalacia) in adults

Histo, Anat & Physiol (12 decks)

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