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Anatomy #1 > The Skin & specialized structures > Flashcards

The Skin & specialized structures Flashcards

1
Q

Skin as the largest organ in the body

A

15-20% total body weight

  • 24% of mass of newborn puppy, 12% of mass of adult dog
  • Contains about half the collagen in the body. About 20% of body’s protein
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2
Q

Layers of skin

A
  1. Epidermis (superficial epithelium)
  2. Dermis
  3. upper layers rest on Hypodermis or subcutis
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3
Q

Function of the Skin

A
  1. Thermoregulation- keep body temperature constant. Regulates heat loss
  2. Sensory- receptors allow skin to monitor environment
  3. Protection and barrier (from pathogens, water)
  4. Mechanical strength
  5. Twitching
  6. Olfactory signalling device
  7. Sexual signalling
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4
Q

Most important component of skin for protection and barrier

A

Collagen

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5
Q

Most abundant protein in the body

A

Collagen

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6
Q

How does skin play a role in sexual signalling?

A

Skin pigmentation and hair indicate health. Sex pheromones released by apocrine sweat glands.

Different Pigments
- Colour comes from melanin pigment. Two types: Brown present in almost all species, and red and yellow pigment.

  • Blue colour you often see is present due to formation of melanin that causes it to appear that way
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7
Q

Characteristics of epidermis

A

Mainly made of stratified squamous keratinized epithelium made up of cells called keratinocytes.

  • develops from ectoderm
  • No blood supply
  • Contain hair follicles and glands that reach from dermis
  • Secretion/nourishment done by diffusion
  • Ability to regrow- takes 2-3 weeks to cells to go from basal layer to top
  • 5 layers
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8
Q

Most important role of epidermis

A

Protection and barrier- inhibits diffusion and provides resistance to friction. Sustains homeostasis.

Also provides some mechanical strength but not much. Strongest piece of epithelium in body though

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9
Q

Strongest part of epithelium in the body

A

Epidermis

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10
Q

Cells within the epidermis

A
  1. Melanocytes
  2. Langerhans cells
  3. Merkel cells
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11
Q

Melanocytes

A

Pigment producing cells

Located in epidermal basal layer, synthesize melanin granules and transfer them into keratinocytes

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12
Q

Langerhans Cells

A

Antigen presenting cells

Purpose: defense

Migrate in blood and take place in the epidermis

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13
Q

Merkel Cells

A

Low threshold mechanoreceptors essential for sensing gentle touch

Located in the basal layer

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14
Q

What is different between thick and thin skin?

A

Thicker skin has more collagen and present in palms and soles

more stratum granulosum and stratum lucidum

depends on on mitotic rate within stratum basale which is adjusted by epidermal chalone

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15
Q

Layers of Epidermis

A
  1. Basal layer (stratum basale)
  2. Stratum Spinosum
  3. Stratum granulosum
  4. Stratum lucidum
  5. Stratum corneum
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16
Q

Basal layer (stratum basale)

A

A single layer of basophilic columnar cells on the basement layer (at the dermal and epidermal junction).

Intense mitotic activity

Contains progenitor cells

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17
Q

What holds the basal layer or stratum basale in place?

A

Hemidesmosomes in the basal cell membranes join these cells to the basal lamina.

Desmosomes bind the cells of this layer together in the lateral and upper surfaces (tonofilaments come from desmosomes to allow for separation)

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18
Q

Progenitor cells

A

Stem cell activity for differentiation into specific cell types

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19
Q

Stratum spinosum

A
  • Normally the thickest layer
  • Cells actively synthesizing keratin
  • Keratin filaments called tonofibrils assembled here and meet at the desmosomes
  • Some cell division may still be occurring in this layer
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20
Q

Stratum granulosum

A
  • 3-5 layers of flattened cells, differentiating into keratinized cells containing keratohyline granules
  • Keratohyline granules- don’t have membrane around them and glue tonofilaments together
  • Lamellar granules- contain lipids that is released between cells giving the keratinized cells an impermeable layer. Helps prevent against water loss.
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21
Q

Keratohyline granules

A

don’t have membrane around them and glue tonofilaments together

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22
Q

Stratum lucidum

A
  • Found only in thick skin
  • Made up of a thin, translucent layer of flattened eosinophilic keratinocytes held together by desmosomes. Cytoplasm of these cells is just packed keratin filaments
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23
Q

Stratum corneum

A
  • 15-20 layers of squamous, keratinized cells filled with birefringent filamentous keratins
  • These fully keratinized cells known as squames are continuously shed at the epidermal surface as the lipid rich membranes and desmosomes break down
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24
Q

Characteristics of Dermis

A

Supports epidermis and binds to subcutaneous tissue (hypodermis)

  • Irregular surface, contains many projections
  • Strong
  • Collagen rich; some elastin fibers
  • Vascular
  • Well innervated
  • Cannot maintain homeostasis
  • Contains glands
  • Where hair originates
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25
Q

What increases diffusion between dermis and epidermis?

A

Projections (ridges and papillae) between epidermis and dermis increase diffusion between the two

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26
Q

Nerve endings of the dermis

A
  • Tactile (Meissner) corpuscles (light touch)
  • Krause bulb (pressure/vibrations)
  • Free Nerve Endings (temp, pain, itching, touch)
  • Root Hair Plexus (mechanoreceptors for touch)
  • Lamellated (Picinian) corpuseles (sustained touch/pressure, vibrations)
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27
Q

Glands within the dermis

A
  1. Sebaceous glands
  2. Eccrine sweat glands
  3. Apocrine sweat glands
28
Q

Sebaceous (oil) glands

A

Embedded in dermis all over the body. Oil empties into a hair follicle

29
Q

Eccrine sweat glands

A

Empty secretion onto the skin surface via sweat pores

  • Areas without hair Ex. foot pads
  • Quite a watery secretion
  • use myoepithelial cells
30
Q

Apocrine sweat glands

A
  • Secrete a more protein-rich sweat into the follicles of hair
  • Smelly
31
Q

Myoepithelial cells

A

Within apocrine sweat glands and act like muscle cells so have the ability to expand and contract expelling the secretions from gland

32
Q

Components of hair

A
  1. Follicle
  2. Hair root
  3. Shaft
33
Q

Components of hair shaft

A
  1. Medulla
  2. Cortex
  3. Cuticle
34
Q

Stages of developing hair

A
  1. Anagen- dermal papilla present and growth phase
  2. Catagen- end of growth phase; dermal papilla reduced and club root fully formed
  3. Telogen- no growth, hair present within skin
  4. Anagen repeats- new hair growth begins beneath old club root
35
Q

Is hair growth continuous?

A

Some hair on the body continuously grows, BUT most hair on animals will only grow to a certain length and then stop (Telogen phase) growing, held in place at club root

**Hair will shed when new hair begins to grow

36
Q

Hypodermis- Subcutaneous Tissue/superficial fascia

A
  • Consists of loose connective tissue that binds skin loosely to organs
  • Very vascular, which contributes to rapid uptake
37
Q

Hair Types

A
  1. Guard hairs (coarse) – often primary hair
  2. Underfur (wool)- often secondary hair
  3. Tactile (whiskers)
38
Q

Primary Hairs

A
  • top coat
  • Usually guard hairs
  • 1 hair from 1 primary follicles
  • Associated with skin glands
  • Develop first
39
Q

Tylotrich Guard Hair

A
  • tactile hair
  • Cats and dogs have tactile elevations (raised barbs of epidermis) associated with their guard hairs
  • Also have small blood filled space (like tactile hair). Blood is dispersed with touch sending signal
40
Q

Secondary hairs

A
  • Usually underfur/wool
  • From secondary follicles
  • Not associated with skin glands
  • Develop later
41
Q

Fibre producing species (secondary hair)

A

Economic importance is in the under-fur
- Wool
- Cashmere and mohair
- Alpaca and Vicuna
- Qiviut
- And more!

From secondary follicles

Often selective breeding to increase the ratio of secondary to primary fibres

42
Q

Whiskers- Tactile hair

A

Similar structure to other hair, but there is a blood filled space filled with nerve endings, and the presence of Pacinian corpuscles.

Blood sinus and corpuscles receive vibrations from the hair, making them sensitive to touch. When blood is displaced, signal is sent allowing us to be aware of stimulus touch

43
Q

Hair orientation of pig

A

Guard hairs (primary hairs) in groups of 3, surrounded by under-fur (secondary hairs)

44
Q

Hair orientation of dog

A
  • Primary hair will grow first through follicle, secondary hairs will grow in afterwards using same follicle
  • Glands mostly with primary hair even though all hair are in same follicle
45
Q

Hair orientation of sheep

A
  • Primary hair grow first through hair follicles, glands in primary hair
  • Secondary hair will separate out and form own follicles
46
Q

Hair orientation of cat

A
  • 1 large primary hair, surrounded by multiple groups of 3 slightly smaller primary hairs
  • Smaller of the primary hairs are then surrounded by many secondary hairs
47
Q

Do animals sweat?

A

Yes! Less obvious but they have sweat glands scattered all over body

  • Sparse in carnivores and pigs
  • Cattle- sometimes visible along neck and flank
  • Horse profuse- Lathered up from apocrine glands (more protein)
48
Q

Sweat Glands

A
  1. Apocrine
  2. Eccrine
  3. Sebaceous glands
49
Q

Apocrine glands

A
  • Albuminous sweat; high proteins
  • Predominates
  • Release into hair follicle

Eg. Mammary glands
- Udder- Develops from sweat glands that penetrate inside the skin and separates everywhere. Produce milk. High in protein, and also producing fat

50
Q

Eccrine glands

A
  • Watery sweat; low proteins
  • Release onto skin surface via pores
  • 2 Types: Nasolabial plate and Nasolabial muzzle OR Digital pads
51
Q

Nasolabial plate (pig) and nasolabial muzzle (cow)

A
  • Type of eccrine gland
  • Firm, tough, fine hairs
  • Keep muzzle moist
52
Q

Digital pads

A
  • Type of eccrine gland
  • Thick epidermis; highly keratinized
  • No hair
  • Pacinian corpuscles located deep in digital pads
  • Helps sweat and provide friction
53
Q

Sebaceous glands

A
  • Release into hair follicle (guard hairs/primary hair)
  • Release sebum- fatty secretion
  • Many types (10)
54
Q

Function of sebum released from sebaceous gland

A
  • Lubricates and water-proofs (eg. Lanolin in sheep)
  • Promotes spread of sweat
  • Retards bacteria
  • Odor/phermomones
55
Q

Sebaceous gland types

A
  1. Cicumoral glands
  2. Horn glands
  3. Infraorbital pouch
  4. Carpal glands
  5. Interdigital pouch
  6. Inguinal pouch
  7. Preputial glands
  8. Tail glands
  9. Circumanal glands
  10. Anal sacs (Para-anal sinuses) – dogs and cats, mink
56
Q

cicumoral glands

A

found in lips of cats, used to mark territory

57
Q

Horn glands

A

Eg. Goats
- both males and females have them. Testosterone stimulates glands giving males strong stinky smell. Estradiol supresses them.

58
Q

Infraorbital pouch

A

Gland near eyes- great lubricant, territorial marker

Eg. Sheep

59
Q

Carpal glands

A

Glands release odor/pheromones used to mark territory.

Population marking when mating

Eg. Pigs, cats

60
Q

interdigital pouch

A

Release when walking which helps mark their territory

Ex. Sheep, caribou

61
Q

Inguinal pouch

A
  • Near mammary glands
  • Similar to wax from our ears
  • Could be used to mark scent on young or to let young know where udder is
62
Q

Tail glands

A
  • Near base of tail
  • Scent marking, species signalling

Eg. Dogs, foxes

63
Q

circumanal glands

A

Present in dogs, thought to be why dogs greet each other and sniff behind

64
Q

Anal sacs (Para-anal sinuses) – dogs and cats, mink

A

On sides of anus. Ducts open up in skin part of anus

Produce smelly material that exits with feces to mark territory

65
Q

Modifications of the skin

A

Claws

Nails

Horns

Anatomy #1 (13 decks)

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