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Microanatomy > Integument > Flashcards

Integument Flashcards

1
Q

Integument

A 
Skin + epidermal derivatives
foot pads, claws
Hooves
horns
glands 
feather etc
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2
Q

Skin

A

Considered the largest organ in the body

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3
Q

Skin functions

A 
Protection: barrier against physical, chemical and biological agents
Prevents water and electrolyte loss
Temperature regulation
Sensation
Calcium homeostasis
Energy storage
Immune function
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4
Q

Components of skin

A

Epidermis- stratified squamous keratinized epithelium
Dermis- papillary layer and reticular layer
Hypodermis- loose CT that may be rich in adipocytes

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5
Q

Epidermis characteristics

A

Ectoderm derived
Avascular
Thick barrier
Composed of epithelium

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6
Q

Dermis Characteristics

A

Mesoderm derived
Contains blood vessels + nervous tissue
Supports the epidermis

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7
Q

Thick skin

A

Thick epidermis
Hairless
Contains merocrine sweat glands
Paw pads, muzzle

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8
Q

Think skin

A

Epidermis is thin
Contains hair follicles often with arrestor pills muscle
Sebaceous and sweat glands

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9
Q

The demo-epidermal junction

A

Interface between the dermis and epidermis
Epidermal pegs
-downward projections of the deep epidermis into dermis
Dermal Papillae
-upward projections of superficial dermis
-Increased surface area between both layers
-Brings blood supply closer to the epithelium

Examples: footpads, nasal planum, scrotum
Areas subjected to traction
not seen on haired skin normally

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10
Q

Dermis

A 
2 layers:
Papillary layer
-loose connective tissue
-type I and III collagen
-mast cells and macrophages
-vessels and nerves

Reticular layer

  • dense irregular CT
  • type I collagen
  • elastic fibers
  • blood vessels and nerves
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11
Q

Cells of epidermis

A

Keratinocytes: most common cell (95% of the total number of cells) in epidermis

Non-keratinocytes

  • langerhans cells
  • merkel’s cells
  • melanocytes
  • variable numbers of intraepithelial lymphocytes
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12
Q

Basic plan of epidermal layers

A 
Generate constant supply of cells
Facilitate cells adhering
-desmosomes (between cells)
-hemidesmosomes (between basal cells and basal lamina)
Replace cytoplasm with keratin
-waterproof
-flatten cells
-provide many layers of this cellular barrier
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13
Q

Layers of the Epidermis

A

As cells mature and progress to the next layer, they move closer to the surface where they eventually die and slough off
From superficial to Deep
1. Stratum corneum: very dead
2. Stratum lucidum (not always present) : dead
3. Stratum granulosum: non- active, alive
4. Stratum spinosum: active and alive
5. Stratum basale: active and alive

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14
Q

Stratum Basale

A

Deepest layer of the epidermis, located at the epidermal-dermal junction
Single layer of cuboidal to columnar epithelium
Attached to basal lamina via hemidesmisomes
Actively dividing (area of mitotic activity)
Basal keratinocytes are functionally heterogenous. Some act as stem cells, whilst some function to anchor the epidermis
May see melanocytes

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15
Q

Hemidesmosomes vs desmosomes

A

Hemidesmosomes bind cells to basal lamina
Desmosomes bind neighboring cells together
Both connect intermediate filaments

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16
Q

Stratum Spinosum

A

Cuboidal or slightly flattened
-Thin skin: 1-2 layers
-Thick skin: many layers thick
Increased number of monofilaments and desmosomes give spiny appearance
Cells are cohesive and they resist abrasion
Cells in this layer retain some capacity for division if needed

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17
Q

Stratum Granulosum

A

Layer that is 3-5 cells thick
Cells begin to flatten
Contain basophilic Keratohyalin granules–> bind with keratin filaments
Lamellar granules (not visible via LM)- secreted by cells to form waterproof lipid sheets, “Intercellular cement”
No mitotic activity, last living layer, nucleus and organelles soon to be lost

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18
Q

Stratum Lucidum

A

Translucent layer
Present in thick skin only
Many keratin filaments, desmosomes present
Cellular organelles are gone- cells are fully keratinized
Cytoplasmplasm contains eleidin- protein chemically related to keratin

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19
Q

Stratum Corneum

A

Outermost layer
Many (up to 20) layers thick, thickness varies by location
Cells consist entirely of Keratin, a water-resistant protein
No nuclei or organelles
Known as horny cells surrounded by a thicker plasma membrane coated by the exterior lipid matrix “bricks and mortar”
Cells continually shed at surface

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20
Q

Keratinization

A

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

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21
Q

Cornification

A

Production of stratum corner by terminal epidermal differentiation

22
Q

Non-Keratinocytes of the epidermis

A

Langerhan’s Cell- immune system
Merkel’s cells- sensory
Melanocytes- protection

23
Q

Langerhan’s Cell

A 
Located in the stratum basal and spinous
Intra-epidermal macrophages
Derived from bone-marrow monocytes
Role in immunity
-antigen presenting to T-cells
-mediators of tolerance
Not often seen without Hand E
24
Q

Merkel’s cells

A

Located in stratum basal of thick skin
Connected to adjacent keratinocytes via desmsosomes
Can act as sensory mechanoreceptors for cutaneous sensation
Can also function to attract nerve endings and stimulate growth
Free nerve endings seen at the base of these cells
Fingertips, feet

25
Melanocytes
Present in the stratum basale Neural crest origin Produce melanin pigment --> migrates within cytoplasmic extensions --> transferred to keratinocytes of stratum basale and spinosum Protects cells from effects of UV radiation Must have tyrosinase for proper function
26
Melanin
Absorbs harmful UV radiation Transformed 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 Pheolmelanin- a red brown polymer largely responsible for red hair and freckles
27
Sensory nerves of the dermis
Nociceptors- free nerve ending that reach the stratum granulosum. Detect pain, itch, temperature Encapsulated nerve endings: -Meissner's corpuscles: light pressure/touch -Pacinian corpuscle: deep pressure -Ruffini corpuscle: senses streatch
28
Epidermal structures/derivatives
``` Hair follicles Compound hair follicles SInus (tactile) hair Sebaceous glands Sweat glands-apocrine or merocrine Udders, mammary glands Hooves, claws, nails Footpads (have merocrine sweat glands) Anal sac glands and anal sacs (paraxial sinuses) Circumanal glands ```
29
Functions of hair
``` Insulation Camouflage Social display Sense/protect Sex recognition ```
30
Anatomy of hair
Produced by hair follicle Hair shaft is above the surface of the skin Hair root is within the follicle and ends with bulb Components: -medulla: loose cuboidal cells with areas of air -Cortex: dense compact keratinized cells -Cuticle- single layer of late keratinized cells
31
Anatomy of hair follicle
Invagination of the epidermis Basement membrane is thickened (glassy membrane) Hair root is within the follicle and ends with bulb Root sheath and dermal papilla
32
Root sheath
External glassy membrane= basal lamina 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 in the opposite direction from the hair cuticle
33
Dermal papilla
Carries blood supply to the cells of the hair | Hair matriculates cells comparable to stratum basale
34
Primary hair follicle
Large diameter Rooted deep in dermis Sebaceous glands, arrestor pili muscle, sweat glands Primary or guard hair
35
Secondary hair follicle
Smaller diameter Rooted nearer the surface +/- sebaceous gland; no sweat glands, no arrestor pili muscle Secondary or under hairs
36
Compound follicles
Cluster 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 and several secondary
37
Arrector pili
Smooth muscle attached to follicle of primary hairs Contraction causes hair to stand up Role in insulation
38
Sinus hairs/whiskers
Tactile hairs Composed of a very large single follicle Blood filled sinus between inner and outer dermal root sheath (movement of hair moves the blood and is a sensory signal) Attached to skeletal muscle to allow for voluntary movement
39
Sebaceous glands
Located in the dermis Produce sebum a mixture of lipid and cell debris Holocrine secretion Antibacterial and waterproofing Ducts empty into a follicle Can be simple, branched or compound glands
40
Specialized sebaceous glands
``` Supracaudal glands- dog Mental glands-cat Horn glands- buck goat Circumanal glands-ruminants Preputial glands- smegma in horse Tarsal (meibomian) glands- eyelids Uropygial glands in birds ```
41
Uropygial gland
Strongly developed in many waterbirds such as ducks
42
Aprocrine sweat glands
Secrete by apical budding/piches Epithelial cells have apical secretory caps Simple saccular or tubular glands with coiled secretory portion and straight duct which opens into the distal hair follicle Contractile myoepithelial cells help express the product In domestic animals, located throughout most of the ski Function is mainly communication (attractions, marker)
43
Specialized apocrine sweat glands
Mammary gland Glands of Moll (in eyelid, make tear film) Apocrine glands of the anal sac Ceruminous glands (ear wax)
44
Anal sacs
Are supplied by perianal glands (sebaceous) and apocrine glands, that should be empty to be manually empties
45
Merocrine sweat glands
Excrete via exocytosis Open directly on to skin surface vs hair follicle Minor in domestic animals Thermoregulation and electrolyte balance; secrete fluid onto skin surface when body temperature rises
46
Hooves and claws
Modification of skin Variation of the stratum corneum Underlain by highly vascular dermis Lack stratum granulosum and stratum lucidum
47
Hoof
``` A highly modified, specialized skin derivative that protects and encloses the end of the digit of an ungulate mammal Equivalent to a nail or claw The hoof has two main layers: -the outer epidermis -the underlying dermis (corium) ```
48
Stratum externum (Hoof)
External layer is known as the glass | Continuation of the periodic epidermis
49
Stratum medium (hoof)
Main supportive layer Tubular and intertubular horn produced by the stratum basale and stratum spinosum of the epidermis of the coronary groove
50
Stratum lamellatum/internum (hoof)
Lamellar horn= insensitive lamellae
51
Laminary corium
Sensitive lamimnae

Microanatomy (21 decks)

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