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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
What are the functions of melanocytes?
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
Where does melanin migrate to after being made?
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
How do we get differences in skin pigmentation?
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
In darker skin tone, melanosomes are ______
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
In lighter skin, melanosomes are ______
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
What are Merkel cells?
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
What is the Merkel cell + nerve ending?
Merkel corpuscle Both parts are the mechanoreceptor
32
What are Langerhans cells and their function?
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
What is the function and characteristics of the dermis?
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
What are the characteristics of the papillary layer?
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
What are Meissner corpuscles?
Encapsulated mechanoreceptors local in dermal papillae Detect light touch on skin surface
36
What is the function of the papillary layer of the dermis?
It is well vascularized so it helps with thermoregulation and supplies oxygen and nutrition to papillary layer and epidermis
37
What are the characteristics of the reticular layer?
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
What is the function of the collagen I fibers and elastic fibers and ECM in the reticular layer of the dermis?
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
What are the functions of the sensory receptors in the reticular layer?
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
What are the characteristics and function of the hypodermis?
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
What are the skin glands?
Sweat (sudoriferous) glands which include eccrine sweat glands (thin and thick skin) and apocrine sweat glands (thin skin) Sebaceous glands - thin skin
42
What are the characteristics of eccrine sweat glands?
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
What is the function of eccrine sweat glands?
Secrete regular sweat in order to regulate body temperature
44
What are the characteristics of apocrine sweat glands?
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
What are the functions of apocrine sweat glands?
Secrete protein rich secretions that contain pheromes
46
What are the characteristics and function of sebaceous glands?
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
What are the parts of hair?
Hair follicles Hair bulbs Hair root
48
What is the function of hair follicles and their characteristics?
Produce and grow (lengthen) hair Contain epidermal stem cells and melanocyte stem cells
49
What is the hair bulb?
Base of hair follicle Hair bulb = hair toot + 1 dermal papilla
50
What is the hair roots and its function?
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
What are the 3 layers of the hair shaft?
Medulla (inner) Cortex (middle) Cuticle (outer) Keratinocytes in all 3 layers and synthesize a more compact form of keratin called hard keratin
52
What does hair color depend on?
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
What structures are associated with the hair below the skin
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
What are the parts of the nails?
Nails (nail plates) Lunula Nail bed Nail root Hyponychium
55
What are the nail plates made of?
Dead, fully keratinized keratinocytes containing hard keratin Translucent but red because of capillaries beneath Do not desquamate
56
What is the lunula of the nails made of?
White, crescent shaped area at base of nail Derives white color from partially keratinized cells in this region
57
What is the nail bed?
Contains softer tissues - dermis, stratum basale, and stratum spinosum Nail and lunula rest on it
58
What is the nail root?
Most proximal part of the nail hidden under a fold of stratum corneum called the eponchium (cuticle)
59
What is the function of the cuticle?
Prevents pathogens, dirt, and debris from getting into deeper tissues under the nail
60
What is the hyponychium and its function?
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
How do nails grow?
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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