1
Q
What is the largest organ of the body?
A
Integument
2
Q
What are the multiple different tissue types found in the integument?
A
- Epithelium
- Connective
- Muscle
- Nervous
3
Q
What are the three layers of the integument?
A
- Epidermis
- Dermis
- Hypodermis
4
Q
Functions of Integument:
A
- Thermoregulation
- Protection from the environment
- Dehydration prevention
- Excretion of wastes/salts
- Absorption
- Sensation
- Beginning of Vitamin D synthesis
- Mate selection (phermones)
5
Q
What is the most superficial layer of the integument?
A
Epidermis
6
Q
What is the Epidermis made of?
A
Keratinized stratified squamous epithelium
7
Q
Epidermis lacks ___ and ____
A
- Innvervation
- Vascularization
8
Q
Layer that supports the Epidermis via diffusion:
A
Deeper dermis layer
9
Q
What are the 5 layers of thick skin (superficial -> deep)?
A
“Can Louie Get Sun Burned?”
(1) stratum Corneum
(2) stratum Lucidum
(3) stratum Granulosum
(4) straum Spinosum
(5) stratum Basale
10
Q
What layer is not found in thin skin but is found in thick skin?
A
Stratum Lucidum
11
Q
Stratum Basale
A
- Deepest layer of the epidermis (next to dermis)
- One cell layer thick
- Composed of mitotically active keratinocytes (helps replace lost/dead cells of layers above), and melanocytes and tactile cells (nervous innervation)
- Microscope: cuboidal to columnar-shaped cells
12
Q
What type of junction connects the basal layer of cells to the basement membrane at the dermal/epidermal junction?
A
Hemidesmosomes
13
Q
What type of junction connects the basal layer of cells to each other?
A
Desmosomes
14
Q
Stratum Spinosum
A
- Present between the stratum granulosum (superficially) and the stratum basale (deep)
- Keratinocytes move up from stratum basal (daughter cells) and begin producing keratin (tonofilaments) here
- Microscope: spiny or polygonal appearance (due to keratin)
- Cells superficial to this layer are no longer mitotically active
15
Q
What is the name used to describe the stratum spinosum and stratum basale together?
A
Stratum Germinativum
(b/c mitotically active cells present)
16
Q
What cells are associated with the Stratum Spinosum?
A
Dendritic Cells (immunity)
17
Q
Stratum Granulosum
A
- Present between the stratum lucidum (thick) or corneum (thin) and stratum spinosum
- Composed of 3-5 layers of flattened cells
- Microscope: cells appear very dark
- Cells undergo keratinization process here and fill with keratin (keratohyalin granules)
- Cells also produce lipids (lamellar granules – released via exocytosis into the ISF) to create dehydration and physical barrier
- Cells begin dying as they are pushed more superficially and their cytoplasm is filled with keratins, and organelles begin degrading
- Cell life also limited by diffusion from the dermis
18
Q
Stratum Lucidum
A
- Present between the stratum corneum and granulosum in THICK SKIN ONLY
- Composed of 2-3 cell layers attached via desmosomes (cells have lost their nuclei and organelles)
- Microscope: clear (due to the intermediate product of keratin maturation, eleidin)
19
Q
Stratum Corneum
A
- Most superficial layer of epidermis so is exposed to the external environment (cells in this layer do not have nuclei or organelles)
- Can have 20-30 layers of dead keratinocyte sheets that are pushed up from the layers below (eventually will be sloughed off)
- Cells at this level are called Squames and have their cell junctions break apart which allows them to come off independently or in chunks
- Layers often break apart during slide processing thus creating an unnatural separation of the layer
20
Q
What cells are most abundant within the epidermal layer of the integument?
A
Keratinocytes
21
Q
Keratinocytes
A
- Produce the protein Keratin and lamellar granules (both help with integument protection)
- Stores melanin (melanin surrounds the superficial surface of the nucleus to provide UV protection)
22
Q
What is the role of Keratin?
A
Provides strength to tissue
23
Q
What is the role of Lamellar Granules?
A
Prevents dehydration by forming a lipid barrier
24
Q
Melanocytes
A
- Produces and secretes the pigment melanin (DOES NOT STORE)
- Contains long branching processes called melanosomes that transfer melanin to other cells
- Microscope: cells have a round nucleus and clear cytoplasm
- Present in the bottom layers of the epidermis (stratum basale into stratum spinosum)
25
What is the function of melanin?
- Provides the integument with color
- Provides UV protection
26
Langerhans Cell (Dendritic Cell)
- Associated with the immune system
- Mostly found in the stratum spinosum of the epidermis
- Finds invaders and presents antigens to T cells
- Microscope: appears paler in comparison to the surrounding keratinocytes, has long extensions, appearance is similar to melanocytes but is found more superficially within the tissue
27
Tactile Cell (Merkel Cell)
- Located in the stratum basale
- Associated with a deeper nerve ending to send its information signals
- Shares the same origin as keratinocytes
- Detects light touch and pressure, and can provide information on an object's texture
- Microscope: appears slightly larger than surrounding cells, looks similar to melanocyte but their nuclei are shifted superiorly
- Superiorly shifted nuclei gives space for neurotransmitters to accumulate along the basal surface and interact with the deeper nerve endings
28
Thick Skin
- Found in areas of high friction or pressure (i.e palms, soles of feet)
- Contains an extra layer in the epidermis, statrum lucidum, and a thicker stratum corneum
- Contains sweat glands but not hair (and associated muscle) or oil (sebaceous) glands
- Associated with visible ridges due to deep integration between dermis and epidermis, forms fingerprints
- Microscope: stratum corneum appears like thick waves due to ridges
29
Thin Skin
- Found throughout most of the body
- More flexible than thick skin
- Epidermis has 4 main layers and contains hair, sebaceous glands, and sweat glands
- Microscope: stratum corneum is thinner and usually flakey in appearance
30
Where is hair not present in the body?
- Thick skin
- Lips
- Nipples
- Some parts of genitalia
- Fingers
- Toes
31
What is hair made up of?
Dead keratinocytes
32
Hair
- Composed of dead keratinocytes that GROW IN PHASES -- start as part of the epidermis that travels deep into the dermis
- Color is based on melanin pigments
- Different types of hair depend on age and location (vellus vs terminal hair)
- Microscope: hair looks clear but has visible pigment granules inside
33
Hair Shaft
- Visible portion of hair that comes out past the surface of the epidermis
34
Hair Root
- Part that is not visible
- Present within the layers of the integument from the epidermis through to the reticular layer of the dermis
35
Hair Bulb
- Active part of hair
- Includes matrix that is made out of dividing keratinocytes that produce new cells
- Cells are pushed superficially to allow growth
- Cells present here: Keratinocytes (produce different amount of keratin compared to skin which gives hair a unique structure), Melanocytes (produce melanin for pigmentation)
- Microscope: appears as an oval structure deep in the dermis
36
Hair Papilla
- Found at the base of the hair bulb
- Contains blood vessels and nerve endings from the dermis that supply the hair with nutrients
- Microscope: stains lighter and has less dense cellular composition compared to the bulb
37
Hair Follicle
- Created by an invagination of the epidermis into the dermis -- located in dermal layer
- Supports the hair
- Surrounded by/attached to Peritrichial Nerve Endings and Arrector Pili Muscle
38
Peritrichial Nerve Ending (Root Hair Plexus)
- Nerve fibers that wrap around the base of the hair follicle
- Present in the reticular layer of the dermis
- Stimulated by hair movement
- Provides information to the nervous system about the environment
39
Arrector Pili Muscle
- Smooth muscle
- Attaches to the hair follicle
- Originates near the papillary layer of the dermis
- Moves the hair to help with homeostasis
- Microscope: appear like streaks running towards the hair follicle
40
What are the nails made of?
Modified stratified corneum (dead keratinocytes)
41
Nails
- Found at distal end of the phalanges
- Made up of modified stratified corneum (dead keratinocytes)
- New nail is made at the nail matrix with stratum basale cells
- Growth is continuous
42
Nail Matrix
- Location where the keratinocytes divide and produce new cells for nail growth
- Creates the nail plate (fingernail or toenail)
43
Nail Root
- Most proximal aspect of the fingernail or toenail
- As it moves further distally it transitions into the nail plate as the keratin matures and hardens
44
Cuticle (Eponychium)
- Component of nail root
- Extension of skin (stratum corneum) covering the nail root
45
Nail Plate
- What is known as the nail
- Formed by the mature, hardened keratinocytes
- Anchored in place by the nail bed
- Transparent in color
46
Nail Bed
- Anchors nail plate to the appendage
- Made out of the stratum basal and stratum spinosum of the epidermis
- Thin
- Able to see the blood flow of the dermis through the nail bed and plate which gives the nail a pink to purple color
47
Sebaceous Gland
- Present in the dermis
- Branched acinar glands that release sebum (lipid mixture) via the holocrine process
- Located near hair (with the duct opening into the follicle), especially on the face and scalp, but can also open directly onto the integument's surface
- Stimulated by hormones
- Help with lubrication, softening and waterproofing
48
Sudoriferous Glands (Sweat Gland)
- Exocrine glands found in the integument
- Created by evaginations of the epidermis into the dermis
- Two types: Eccrine gland, Apocrine gland
49
Eccrine Gland (Merocrine Gland)
- The most numerous glands found in the integument
- Coiled
- Release excess water (and wastes) through exocytosis to help in homeostasis (cooling via evaporation)
- Gland parenchyma is within the reticular layer of the dermis
- Ducts (stratified cuboidal) are open onto the surface of the skin
- Follows a merocrine (exocytosis) release
- present in both thick and thin skin
- Histology: gland looks like a collection of circular structures each with a central lumen
50
Apocrine Gland
- Located in the axillary, pubic and anal regions
- Larger than eccrine glands and have larger ducts
- Located near hair follicles with the ducts (stratified cuboidal) opening into the follicle itself
- Secretions include protein and lipids
- Associated with emotional sweating and body odor (bacteria feed off of the secretion)
- Do not become fully functional until puberty and hormone stimulation
- Follow a merocrine and some apocrine release
51
What is the deepest layer of the integument?
Dermis
52
Dermis
- Lies between the epidermis and hypodermis
- Made up of two layers of connective tissue, thickness of this layer varies based on location within the body
- Vascularized and innervated
- Supports the epidermis by providing it nutrients and collecting waste
53
Papillary Layer
- Thin, superficial layer of the dermis closest to the epidermis (dermal-epidermal junction)
- Made of areolar connective tissue
- Contains fibers, fibroblasts, fibrocytes, mast cells, dendritic cells, and leukocytes
- Microscope: wave-like appearance with dermal papilla interdigitating with the epidermal ridges (functions in increasing the integration between the dermis and epidermis, increases the surface area for the transfer of nutrients and wastes)
- Cell layers kept together via hemidesmosomes
54
Subpapillary Plexus
- Component of papillary layer in dermis
- Vascular network located between the papillary and reticular layers -- extends networks of capillaries into the dermal papilla to help supply the epidermis
55
Reticular Layer
- Deeper, thicker layer of the dermis lying between the papillary layer and the hypodermis
- Made up of dense irregular connective tissue with collagen and elastic fibers
- Collagen (type 1) forms regular lines of tension (lines of cleavage/Langer's lines) that are clinically important for incisions and scarring
- Extensions of the epidermis are present in this layer as hair follicles, sebaceous glands and sweat glands
- Contains arteriovenous anastomoses for thermoregulation between the subpapillary and deep plexuses
56
Deep Plexus
- Component of reticular layer
- Lies near the dermis-hypodermis interface
- Contains larger blood vessels and lymphatics
57
Free Nerve Endings
- Neurons located in the papillary layer of the dermis and can extend into the lower epidermal layers
- Help detect high and low temperatures, itching, pain and tactile information
58
Tactile Corpuscle (Meissner Corpuscle)
- Located in the papillary region of the dermis (dermal papilla)
- Encapsulatd nervous tissue
- Provides information on light touch and low frequency vibration to the CNS (aka functions as a mechanoreceptor)
- Microscope: looks like an oval stack of pancakes
- Prominent in lips, fingertips, plantar feet, and genitals
- Phasic responses -- they respond quickly to a change in stimulus
59
Lamellated Corpuscle (Pacinian Corpuscle)
- Located in the reticular layer of the dermis and hypodermis
- Encapsulated nervous structure that provides information on deep pressure and high-frequency vibrations
- Microscope: looks like a hemisection of an onion
60
Ruffini End Organ
- Located in the reticular layer of the dermis, but not as widely distributed as other nerves -- mostly found in the joint capsules
- Encapsulated nervous structure that responds to stretching or torsion of the skin
61
Hypodermis (Subcutaneous Tissue, Superficial Fascia)
- Lies deep to the integument and helps connect the integument to deeper structures
- Composed of adipose (differing distribution btwn sexes) and areolar connective tissue
- Tissues contain fibroblasts, fibrocytes, adipocytes, and macrophages
- Provides insulation for the body and energy storage
62
What component of the Epidermis provides sealant between adjacent cells?
Glycolipids and Lipids
63
Cell that is derived from precursors originating in the bone marrow and functions as antigen-producing cells:
Langerhans Cells
(form a network through the epidermis, intercepting and sampling microbial invaders before moving to lymph nodes in adaptive immune response)
64
Structure that typifies the reticular layer of the dermis but not the papillary layer:
Dense Irregular Connective Tissue
(Dermis has two major layers: a superficial papillary layer made of loose connective tissue with a microvascular plexus, and a thicker dense irregular reticular layer containing larger blood vessels)
65
Characteristic of sebaceous glands:
It releases it contents via Holorcine secretion
66
Patient presents with severe blistering over her arms, Immunohistochemical techniques stain material located at the basement membrane of the epidermis in a biopsy of their skin. The underlying biological mechanism of the skin disorder involves an abnormality in what structure?
Hemidesmosomes
(stratum basale is one layer of mitotically active cuboidal cells attached by hemidesmosomes and integrins to the basement membrane and to each other by desmosomes)
67
Patient is dx with merkel cell carcinoma. If the UV radiation affected the merkel cells, what other cell type sharing the same specific epidermal layer might also be affected?
Keratinocytes of the Stratum Basale
(Merkel cells, keratinocytes, and melanocytes are all found in the stratum basale)
68
All skin cells of the epidermis are keratinocytes except for ___ cells
Germ
69
What structures/cells are in the Stratum Corneum?
- Keratinocytes
- Squames
70
What structures/cells are in the Stratum Granulosum?
- Keratinocytes (Keratohyalin Granules)
- Lamellar Granules
71
What structures/cells are in the Stratum Spinosum?
- Keratinocytes (Tonofilaments)
- Melanocytes
- Langerhans Cells
- Dendritic Cells
72
What structures/cells are in the Stratum Basale?
- Keratinocytes
- Melanocytes
- Merkel Cells/TActile Cells
73
What structures/cells are in the Papillary Layer of the Dermis?
*Areolar Connective Tissue
- Fibers
-Fibroblasts
- Fibrocytes
- Mast Cells
- Dendritic Cells
- Leukocytes
- Arrector Pili Muscle
- Free Nerve Endings
- Tactile Corpuscle (Meissner Corpuscle)
- Subpapillary/Microvascular Plexus
74
What structures/cells are in the Reticular Layer of the Dermis?
*Dense Irregular Connective Tissue
- Hair Follicles
- Sebaceous Glands
- Sweat Glands
- Deep Plexus
- Pertrichial Nerve Endings (Root Hair Plexus)
- Lamellated Corpuscle (Pacinian Corpuscle)\
- Ruffini End Organs (mostly in joints)
MSK Exam 2
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