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FoundSci Unit 7 > Integument > Flashcards

Integument Flashcards

1
Q

What is the integumentary system?

A

Skin and its epidermal derivatives

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2
Q

What are the skin (cutis, integument) layers?

A

Epidermis

Dermis

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3
Q

What are the epidermal derivatives of skin?

A

Hair follicles and hair

Sebaceous glands

Sweat (sudoriferous) glands - eccrine and apocrine

Nails

Mammary glands

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4
Q

What is the hypodermis made up of?

A

Subcutaneous fascia

Mostly white fat

Also has CT septa, sensory receptors, vessels, and nerves

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5
Q

What are the functions of the skin?

A

Barrier that protects the body

Homeostasis - regulates body temperature and water loss

Sensory organ

Excretion of exocrine products

Endocrine organ

Selective absorption

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6
Q

What are the characteristics of thin skin?

A

Most skin is thin skin

Epidermis is thin and has 4 layers (strata)

Thicker dermis than thick skin

Has eccrine and sometime apocrine sweat gland, sebaceous glands, hair.

Surface lacks alternating ridges and grooves

Fewer nerve endings and fewer sensory receptors than thick skin

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7
Q

What are the characteristics of thick skin?

A

Skin of palms and soles

Epidermis is thick and has 5 layers. Thinner dermis than thin skin

Only has eccrine sweat glands

Lacks sebaceous glands, hair

Surface has alternating ridges and grooves

Always sensitive - many nerve endings and sensory receptors

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8
Q

What is the function of thick skin?

A

Protects against damage

Increased ability to grip surfaces and objects

Increased sensitivity for object manipulation and where our body weight contacts ground

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9
Q

What are characteristics about epidermis?

A

Keratinized stratified squamous epithelium - avascular, from ectoderm, and 4-5 strata

Grows continuously, but thickness is consistent - new cells added to basal layers via mitosis at same rate cells are lost from superficial layers (desquamation)

Contact with dermis is very distinct - locks both layers in place and reduces risk of epidermal delamination

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10
Q

What are the 5 epidermal strata?

A

Stratum corneum - thin/thick, flaky, superficial layer

Stratum lucidum - thick skin only

Stratum granulosum - thin/thick

Stratum spinosum - thin/thick

Stratum basale - thin/thick, basalmost layer

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11
Q

What are the cells of the epidermis and their function?

A

Keratinocytes

Synthesize a type of keratin called soft keratin

Help form the epidermal water barrier by synthesizing and secreting lipids and soft keratin also contributes

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12
Q

What are the names and functions of other keratinocytes?

A

Basal cells - stem cells that generate new keratinocytes (stratum basale)

Prickle cells - synthesize keratin protein (stratum spinosum)

Granular cells - synthesize lipids and undergo keratinization (stratum granulosum)

Keratinized cells - forms a physical barrier of dead cells (stratum lucidum and stratum corneum), in stratum corneum they are called squames

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13
Q

What are the characteristics of the stratum basale?

A

Single layer of cells in contact with BM

Deepest layer of epidermis

Cells are mainly basal cells - stem cells of epidermis and are cuboidal and divide to create new keratinocytes

Other cells include melanocytes that make melanin and Merkel cells that are mechanoreceptors

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14
Q

What are the characteristics of the stratum spinosum?

A

second thickest stratum

Several to many layers of tightly linked cells

Spiny appearance

Most cells are prickle cells that make lots of keratin that aggregate into tonofilaments

Intercellular bridges extend between adjacent cells

Other cells include Langerhans cells (dendritic cells) which are antigen presenting cells

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15
Q

What are the characteristics of the stratum granulosum?

A

3-5 layers of flattened cells - cells in most layers are alive, cells in superficial layer are dying and those that finish dying cross into stratum lucidum/corneum

All cells are granular cells

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16
Q

What is the function of granular cells in the stratum granulosum?

A

Undergo keratinization - named for intensely basophilic keratohyalin granules in cytoplasm

Synthesize lipid components of epidermal water barrier - has organelles called lamellar bodies that synthesize and store lipids that help waterproof skin

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17
Q

What are the characteristics of stratum lucidum?

A

Only in thick skin

1-2 indistinct, homogenous layers of cells

Cells lack visible organelles/granules - stains acidophilic or is unstained

All cells in this layer are dead keratinocytes called keratinized cells - fully keratinized with no visible nuclei, granules, or other organelles

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18
Q

What are the characteristics of stratum corneum?

A

Most superficial stratum

Several to many layers of flattened and desiccated dead cells

Change in pH moving from basal layers to the surface

All cells are dead keratinocytes called keratinized cells or squames (horny cells) that are fully keratinized with no visible nuclei/organelles and no desmosomes

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19
Q

Where is stratum corneum thickest?

A

Areas subject to higher amounts of friction, shearing forces, or focal pressure (calluses and corns)

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20
Q

What is desquamation or exfoliation?

A

Cells on surface are sloughed off or worn off by abrasion

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21
Q

Describe the process of keratin synthesis

A

All living keratinocytes of the epidermis synthesize a type of keratin called soft keratin

Prickle cells synthesize LOTS of keratin protein and aggregate it into bundles called tonofilaments

Granular cells are where keratinization occurs - as apoptosis begins, filaggrin and tricohyalin surrounded and crosslink keratin tonofilaments and form water insoluble tonofibrils

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22
Q

What are keratohyalin granules?

A

Clusters of proteins filaggrin and tricohyalin in the cytoplasm of granular cells

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23
Q

What is keratinization?

A

Process of converting all keratin tonofilaments into tonofibrils

Keratinized cell cytoplasm is mostly tonofibrils and other water insoluble proteins that create a mechanically strong barrier

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24
Q

How is the epidermal water barrier formed?

A

Lamellar bodies synthesize and store lipids that help waterproof skin

Granular cells secrete lamellar body contents into ECM of stratum granulosum and deepest corneum

Lipids form waterproof barrier but also prevent nutrient diffusion to cells so superficial layer of stratum granulosum starve and it initiates apoptosis

Proteases are activated by low pH in superficial layer of stratum corneum which degrades desmosomes and allows desquamation

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25
Q

What are the functions of melanocytes?

A

Cell bodies in basale and long processes extend into spinosum

Synthesize melanin (endogenous pigment) in specialized organelles called melanosomes (melanin granules)

Multistep process that involve oxidation of tyrosine

Melanin absorbs UV radiation

26
Q

Where does melanin migrate to after being made?

A

Melanosomes synthesize melanin and migrate to tips of melanocyte cell processes

Tips of processes exocytosed into ECM of spinosum and phagocytosed by prickle cells

Melanosomes released into prickle cell cytoplasm and aggregate along superficial side of nucleus

Forms dark umbrellas of melanin that shield nuclear DNA in dividing cells from UV radiaiton

27
Q

How do we get differences in skin pigmentation?

A

Melanocyte number and ratio of melanocytes to prickle cells vary in different part of the body

Melanocyte number and ratio of melanocytes to keratinocytes very similar across all people

Exposing skin to sunlight promotes melanin synthesis in melanosomes

Differences in baseline skin pigmentation among people of different skin tones and races results from difference in the number, size, and distribution of melanosomes, and rate of melanin breakdown

28
Q

In darker skin tone, melanosomes are ______

A

Larger and more numerous

Distributed throughout prickle cell cytoplasm

Present in more cells/layers of the stratum spinosum

Rate of melanin breakdown is slower

29
Q

In lighter skin, melanosomes are ______

A

Smaller and less numerous

Only accumulate in umbrella of cytoplasm above nucleus

Not in superficial layer of stratum spinosum

Rate if melanin breakdown is faster

If sun exposed (tanned), melanosome distribution becomes similar to darker skin

30
Q

What are Merkel cells?

A

In stratum basale

Mechanoreceptors that likely transmit fine/detailed touch sensation about shape and texture

Associated with sensory nerve endings with flat, expanded ends (merkel discs)

31
Q

What is the Merkel cell + nerve ending?

A

Merkel corpuscle

Both parts are the mechanoreceptor

32
Q

What are Langerhans cells and their function?

A

In stratum spinosum

Antigen presenting cells and part of immune response to contact allergens - they present epitopes to T lymphocytes to initiate delayed type hypersensitivity reactions

Actively defend the skin versus the bacteria that causes leprosy

33
Q

What is the function and characteristics of the dermis?

A

Strong tissue layer that provides structural support to the skin

Vascularized CT and rich in collagen I fibers and elastic fibers

Contains most sensory receptors of skin as well as motor ends that supply vessels, arrector pili, and glands

Derived from mesoderm

Dermal papillae form boundary with epidermal ridges/pegs of epidermis

2 layers - papillary layer and reticular layer

34
Q

What are the characteristics of the papillary layer?

A

Superficial and thinner layer of dermis

Named for dermal papillae

Loose CT: mainly elastic and reticular fibers

Well vascularized with abundant capillary loops in dermal papillae

Cells in papillary layer are CT cells (fibroblasts, macrophages, mast cells)

Sensory receptors in papillary layer - Meissner corpuscles

35
Q

What are Meissner corpuscles?

A

Encapsulated mechanoreceptors local in dermal papillae

Detect light touch on skin surface

36
Q

What is the function of the papillary layer of the dermis?

A

It is well vascularized so it helps with thermoregulation and supplies oxygen and nutrition to papillary layer and epidermis

37
Q

What are the characteristics of the reticular layer?

A

Deeper and much thicker dermis

Refers to appearance of collagenous CT that contains collagen I fibers

Dense irregular collagenous CT that contains collagen I and elastic fibers ONLY

Cells of reticular layer are CT cells (fibroblasts, lymphocytes, white adipocytes)

Sensory receptors are all encapsulated and include Pacinian corpuscles, Ruffini corpuscles, and Krause end bulbs

38
Q

What is the function of the collagen I fibers and elastic fibers and ECM in the reticular layer of the dermis?

A

Collagen I fibers - provide structural support and allow dermis to resist tensile forces from multiple direction

Elastic fibers give the skin elasticity

ECM rich in GAGs that drive hydration of the tissue

39
Q

What are the functions of the sensory receptors in the reticular layer?

A

Pacinian corpuscles - mechanoreceptors that detect deep pressure and vibration on skin surface

Ruffini corpuscles - mechanoreceptors that detect stretching and torque of skin

Krause end bulbs - thermoreceptors that detect the cold

40
Q

What are the characteristics and function of the hypodermis?

A

Hypodermis is subcutaneous or superficial fascia of gross anatomy and is transition zone between dermis and deep fascia

Technically not part of the skin

Mostly white fat that provides insulation and energy storage

Some CT

Vascularized and inenrvated

Contains some Pacinian corpuscles

41
Q

What are the skin glands?

A

Sweat (sudoriferous) glands which include eccrine sweat glands (thin and thick skin) and apocrine sweat glands (thin skin)

Sebaceous glands - thin skin

42
Q

What are the characteristics of eccrine sweat glands?

A

Thin and thick skin

Serous glands that use merocrine secretion

Secretions are hypotonic, water, and low in protein. Contain sodium chloride, urea, uric acid, and ammonia

Glands are tubular glands that do not branch - both secretory units and ducts are tubular and coiled

Located deep in dermis of skin of entire body, except lips and parts of external genitals

43
Q

What is the function of eccrine sweat glands?

A

Secrete regular sweat in order to regulate body temperature

44
Q

What are the characteristics of apocrine sweat glands?

A

Thin skin only

Serous glands that use merocrine secretion

Only in the axilla, areola, nipple, anal region, skin near external genitals

Secretions vary in color, content, and viscosity depending on region - typically a mix of proteins, carb, ammonia, and lipids

Coiled tubular glands that sometimes branch - much larger lumens than eccrine glands and ducts usually empty hair follicles

45
Q

What are the functions of apocrine sweat glands?

A

Secrete protein rich secretions that contain pheromes

46
Q

What are the characteristics and function of sebaceous glands?

A

Thin skin only

Sebaceous glands use holocrine secretion

Always associated with hair follicles

Acinar glands with short ducts that open directly into the hair follicle

Secrete an oily/waxy substance called sebum which coats the surfaces of hairs and skin surface

47
Q

What are the parts of hair?

A

Hair follicles

Hair bulbs

Hair root

48
Q

What is the function of hair follicles and their characteristics?

A

Produce and grow (lengthen) hair

Contain epidermal stem cells and melanocyte stem cells

49
Q

What is the hair bulb?

A

Base of hair follicle

Hair bulb = hair toot + 1 dermal papilla

50
Q

What is the hair roots and its function?

A

Contains hair matrix cells that migrate to the bottom of the hair and differentiate into keratinocytes that form 3 layers of the hair shaft

51
Q

What are the 3 layers of the hair shaft?

A

Medulla (inner)

Cortex (middle)

Cuticle (outer)

Keratinocytes in all 3 layers and synthesize a more compact form of keratin called hard keratin

52
Q

What does hair color depend on?

A

Depends on specific type/color of melanin contained in the hair

Melanocytes in the hair roots transfer melanosomes to keratinocytes in the cortex and in the medulla of the hair shaft

53
Q

What structures are associated with the hair below the skin

A

Each hair shaft surrounded by internal and external roots sheaths

Each hair follicle has 1 or more sebaceous glands who ducts open into the follicle

Arrector pilli muscles - smooth muscle that attaches obliquely to hair follicle. When muscle contract, pulls hair follicle and raises hair. Also around sebaceous glands so contraction forces sebum into lumen of hair follicle

54
Q

What are the parts of the nails?

A

Nails (nail plates)

Lunula

Nail bed

Nail root

Hyponychium

55
Q

What are the nail plates made of?

A

Dead, fully keratinized keratinocytes containing hard keratin

Translucent but red because of capillaries beneath

Do not desquamate

56
Q

What is the lunula of the nails made of?

A

White, crescent shaped area at base of nail

Derives white color from partially keratinized cells in this region

57
Q

What is the nail bed?

A

Contains softer tissues - dermis, stratum basale, and stratum spinosum

Nail and lunula rest on it

58
Q

What is the nail root?

A

Most proximal part of the nail hidden under a fold of stratum corneum called the eponchium (cuticle)

59
Q

What is the function of the cuticle?

A

Prevents pathogens, dirt, and debris from getting into deeper tissues under the nail

60
Q

What is the hyponychium and its function?

A

Anchors the underside of the nail to the skin of the fingertip

Part of nail distal to the hyponychium is the free edge of the nail

Prevents pathogens, dirt, and debris from getting into deeper tissues under the nail

61
Q

How do nails grow?

A

Nail root overlies the nail matrix which contains the epidermal stem cells

Stem cells in the nail matrix divide, migrate to nail root, and differentiate into keratinocytes that make hard keratin and become keratinized

Nails grow by constantly adding keratinocytes to the proximal end of the nail root

Adding new cells to the proximal end pushes older keratinocytes distally across nail bed

FoundSci Unit 7 (14 decks)

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