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Microanatomy > Integument > Flashcards

Integument Flashcards

1
Q

T/F: Skin is the largest organ in the body.

A

True

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2
Q

Functions of the skin

A
  • protection
  • prevents loss of water and electrolytes
  • temperature regulation
  • sensation
  • elasticity permits movement
  • immune function
  • excretion
  • calcium homeostasis
  • energy storage
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3
Q

Functions of hair

A
  • insulation
  • camouflage
  • social display
  • sense/protect
  • sex recognition
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4
Q

What kind of epithelium is found in the epidermis?

A

Stratified squamous keratizined epithelium

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5
Q

Desribe thick skin and give examples

A
  • epidermis is thin
  • hairless
  • merocrine sweat glands are present
  • ex.) digital pads, muzzle
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6
Q

Describe thin skin

A
  • epidermis is thin
  • hair follicles with arrector pili muscle
  • sebaceous and sweat glands
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7
Q

Epidermal pegs/ridges

A

Downward projections of the epidermis into the underling dermis

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8
Q

Dermal papillae

A

Upward projections of the superficial dermis; increase area of contact between epidermis and dermis; bring blood vessels near the epithelium

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9
Q

What is the principal component of dermis and describe the two layers?

A
  • connective tissue is principal component
  • papillary layer
    • loose CT
    • type I, III collagen
    • mast cells, macrophages, vessels, nerves
  • reticular layer
    • dense irregular CT
    • type I collagen
    • network of elastic fibers
    • blood vessels, nerves
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10
Q

What contributes to skin’s elasticity?

A

A network of elastic fibers in the reticular layer of the dermis

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11
Q

Cells of the epidermis

A
  • keratinocytes - most common cell, account for 95% of the total number of cells in the epidermis
  • non-keratinocytes
    • Langerhans cells
    • Merkel’s cells
    • melanocytes
    • variable numbers of intraepithelial lymphocytes
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12
Q

Desmosomes vs. Hemidesmosomes

A
  • desmosomes are found between cells
  • hemidesmosomes attach basal cells to the basal lamina
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13
Q

Name the layers of epidermis

A
  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum (not present at all sites)
  • Stratum corneum
  • Ball Sacs Get Licked Constantly
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14
Q

Stratum basale

A
  • epidermal-dermal junction
  • single layer of cuboidal to columnar cells
  • rests on basal lamina
    • hemidesmosomes bind cells to basal lamina
    • desmosomes bind neighboring cells together
  • area of mitotic activity
    • stem cells proliferate by mitotic division, new cells move up and keratinize
  • may see melanocytes in this layer
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15
Q

Stratum spinosum

A
  • cuboidal or slightly flattened
    • thin skin: 1-2 cells thick
    • thick skin: many layers thick
  • desmosomes and increased number of tonofilaments give spiny appearance –> “prickle cells layer”
  • cells are cohesive and they resist abrasion
  • cells in this layer retain some capacity for division if needed
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16
Q

Stratum granulosum

A
  • 3-5 layers, cells begin to flatten; may be difficult to see in thin skin
  • keratohyalin granules –> bind with keratin filaments
  • staining appearance: basophilic
  • lamellar granules (EM) - secreted by cells to form waterproof lipid sheets, “intercellular cement”
  • no mitotic activity, last living layer, nucleus and organelles soon to be lost
17
Q

Stratum lucidum

A
  • translucent layer (present in thick skin only)
  • many keratin filaments, desmosomes present
  • cellular organelles are gone - cells are fully keratinized
  • cytoplasm contains eleidin - protein chemically related to keratin
18
Q

Stratum corneum

A
  • 15-20 layers thick, thickness varies by location
  • cells consist of keratin, a water-resistant protein that forms a barrier against the destructive forces of the environment
  • known as horny cells surrounded by a thicker plasma membrane coated by the exterior lipid matrix; “bricks and mortar”
  • cells continually shed at surface
19
Q

Keratinization

A

Process by which keratinocytes differentiate, about 21 days in length in the dog

20
Q

Cornification

A

Production of stratum corneum by terminal epidermal differentiation

21
Q

Langerhans cells

A
  • found in stratum basale, stratum spinosum
  • small percentage of total cells, 2-8%
  • intra-epidermal macrophages: bone-marrow derived (from monocytes)
  • role in immunological skin reactions as
    • APCs
    • internalize surface-bound antigen for processing and presenting at its cell surface to T lymphocytes
22
Q

Merkel’s cells

A
  • present in thick skin near stratum basale
  • may be sensory mechanoreceptors for cutaneous sensation or diffuse neuroendocrine system
  • free nerve endings seen at base of these cells
23
Q

Melanocytes

A
  • present in stratum basale
  • neural crest origin
  • stable cell, live years
  • produce pigment melanin –> migrates within cytoplasmic extensions –> transferred to keratinocytes of stratum basale and spinosum
  • protects cell from effects of UV radiation
  • must have tyrosinase for proper function
24
Q

Melanin

A
  • absorbs harmful UV-radiation
    • transforms the energy into harmless amounts of heat
    • keeps the generation of free radicals at a minimum
  • eumelanin - most common form of melanin, brown black pigment
  • pheomelanin - a red-brown polymer largely responsible for red hair and freckles
  • no tyrosinase –> no melanin –> albino!
25
Q

Sensory nerves of dermis

A
  • free nerve endings to stratum granulosum
    • nociceptors - pain, itch, temperature
  • encapsulated nerve endings
    • meissner’s corpuscles
    • pacinian corpuscle
    • ruffini corpuscle - sense stretching
26
Q

Hair follicle

A
  • epidermal invagination
  • glassy membrane - a thick basement membrane
  • hair
    • medulla - loose cuboidal cells; air filled in areas
    • cortex - dense compact keratinized cells parallel to hair shaft
    • cuticle - single layer of flat keratinzied cells
  • the pattern of cuticle and medulla is characteristic for each species
27
Q

Layers of hair follicle

A
  • dermal papilla
    • carries blood supply to the cells of the hair
    • hair matrix cells comparable to stratum basale
  • root sheath
    • external glassy membrane - basal lamina; external to external root sheath
    • external root sheath - continuous with epidermis
    • internal root sheath - a few layers of squamous cells
    • cuticle - internal to internal root sheath; formed by overlapping keratinized cells but with free edges oriented in the opposite direction from the hair cuticle, towards the hair bulb
28
Q

Primary hair follicle

A
  • large diameter
  • rooted deep in dermis
  • sebaceous glands, arrector pili muscle, sweat glands
  • primary or guard hair
29
Q

Secondary hair follicle

A
  • smaller diameter
  • rooted nearer the surface
  • +/- sebaceous gland; no sweat glands, no arrector pili muscle
  • secondary or under hairs
30
Q

Compound hair follicle

A
  • clusters of several hair follicles
  • the follicles merge at the level of the sebaceous gland and emerge through one external orifice
  • compound follicles usually have one primary follicle and several secondary hair follicles
31
Q

Sebaceous glands

A
  • produce sebum - mixture of lipid and disintegrated cells
  • acts as an antibacterial and waterproofing agent
  • ducts empty into hair follicle or skin surface
  • cells accumulate lipid droplets as they differentiate towards the center of the gland
32
Q

Uropygial/Preen gland

A

Sebaceous glands that are strongly developed in many waterbirds such as ducks (but not in cormorants which are highly aquatic)

33
Q

Sweat glands

A
  • epithelial cells of apocrine sweat glands with apical secretory caps
  • simple saccular or tubular glands with coiled secretory portion and strait duct
  • contractile myoepithelial cells surround secretory units and help express the product
  • in domestic animals, located throughout most of the skin, in contrast to humans
  • function is mainly communication (attraction, marker)
34
Q

Eccrine/Merocrine sweat glands

A
  • open directly onto skin surface vs. hair follicle
  • minor in domestic animals
  • thermoregulation and electrolyte balance; secrete fluid onto skin surface when body temperature rises
  • vs apocrine glands - where hair is, smelly
35
Q

Hooves and claws

A
  • modification of skin
  • variation of the stratum corneum
  • underlain by highly vascular dermis
  • lack stratum granulosum and stratum lucidum
36
Q

Epidermal layers of the hoof wall

A
  • stratum tectorium/externum
    • thin orange layer
    • external layer is known as the ‘glaze’
    • continuation of perioplic epidermis
  • stratum medium
    • yellow
    • the main supportive layer
    • tubular and intertubular horn produced by the stratum basale and stratum spinosum of the epidermis of the coronary groove
    • stratum lamellatum/internum
      • blue
      • lamellar horn = insensitive lamellae
  • laminar corium/dermis
    • laminar corium (red area) = sensitive lamimnae

Microanatomy (4 decks)

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