Chapter 15 - Integumentary System Flashcards
What does the integumentary system consist of?
Skin and its derivatives (hair follicles, sweat glands, sebaceous glands, nails, mammary glands)
What are the two main layers of the skin?
- Epidermis
- Dermis
(hypodermis)
What type of tissue makes up the epidermis layer of the skin?
Stratified squamous keratinized epithelium
What type of tissue is the dermis layer of the skin composed of?
Loose Connective Tissue, Dense Irregular CT
What tissue type is the hypodermis made out of?
Adipose tissue: subcutaneous facia
What are the two subclasses of skin?
- Thick
- Thin
What is the difference between thick and thin skin?
Thin: the epidermis is less than the dermis
Thick: epidermis is thicker than the dermis
What does thick skin lack that thin skin has?
Thick skin lacks hair follicles
What are the six functions of the integumentary system?
- Barrier
- Immunological Info
- Maintains Homeostasis
- Sensory Information
- Endocrine Function
- Excretion
What characteristics of the skin provide a barrier against physical, chemical, and biological insults?
Codification = accumulation of keratin and formation of lipid layer
What two ways does the skin maintain homeostasis?
- Regulate body temp
- Prevent water loss
What type of sensory information does the skin provide? (4)
- Pain
- Temp
- Vibrations
- Pressure
What endocrine functions does the skin perform? (3)
Secreting growth factors, cytokines, processing vitamin D
What three things does the skin excrete?
Sweat
Oil
Apocrine
What are the four major layers of the epidermis? What is the fifth layer observed in thick skin?
Superficial: stratum corneum
stratum lucidum *thick skin only
stratum granulosum
stratum spinosum
stratum basale
Which layer makes up the bulk of the epidermis?
Stratum corneum
Codified layer
What type of cells are in the epidermis?
Keratinocytes
As cells move upwards they transition from the stratum granulosum to corneum where they undergo apoptosis
What happens to keratinocytes in the stratum corneum?
desquamation on the outer layer - shedding off of the cells
Where is the stratum basale located? What type of cells does it have? What shape do the cells have - what does this indicate?
Single layer resting on basal lamina
Contains stems cells –> keratinocytes (basal cells)
Cuboidal; decreased cytoplasm, increased nucleus = increased mitotic activity
What type of cells are in the stratum spinosum?
Prickle cells with spinous processes
What is the function of the spinous processes of prickle cells?
Cytoplasmic extensions that connect adjacent cells via bridges and desmosomes
What happens as prickle cells move upwards?
Prickle cells make more and more keratin/tanofillaments and keratohyalin granules
Where is the stratum granulosum? What do the cells look like in this layer?
Outermost non-keratinized layer
Keratinocytes contain keratohyalin grunules
What are keratohyalin granules important for?
They are important for forming tanofibril bundles which form around basophilic granules
How many layers of cells thick in the granulosoma? Is it in thick or thin skin?
In thick skin
3-5 cell layers thick
What is the last living stage for cells in the epidermis?
Stratum granulosum
What is the progression of cells through the epidermis?
Stem > Prickle > llamelar bodies????
What is the significance of the lamellar bodies in keratinocytes?
They are important for the water barrier
In what type of skin do we find stratum lucidum? What are the characteristics of cells in this layer?
Thick Skin
Advanced keratinization = no nucli
Stains poorly
What type of cells are found in the stratum corneum? What are they filled with?
Anucleate squamous cells
Filled with keratin filaments (85%)
How many layers thick is the corneum?
5 cell layers thick
What are the four cell types found in the epidermis?
- Keratinocytes
- Melanocytes
- Langerhans’ Cells
- Merkel’s Cells
Where are keratinocytes found?
From the stratum basale to the stratum corneum
What are the two major functions of Keratinocytes?
- Keratin Production
- Water barrier
Where do you find Melanocytes?
Only in stratum basale
Where do you find Merkel’s cells?
Stratum basale
Keratin assembles into _______ which organize into ______
Tonofilaments
Tonofibrils
Talk me through keratinocyte maturation through the layers of the epidermis
Stratum Basale > make keratin > Stratum Spinosum > Tonofillaments > Upper Stratum Spinosum > Fillagrgrin and Trichohyalin > Tanofibrils > Stratum Granulosum > Increase Tonofibrils > Create Cell Envelope > Stratum Corneum > Apoptosis
What are two things (proteins?) required for the aggregation of tonofibrils? What is this process of aggregation called?
- Filaggrin
- Trichohyalin (keratohyalin granules)
Keratinization
What is desquamation?
Apoptosis and subsequent shedding of keratinocytes (squams) off the stratum corneum
What is the process of desquamation?
Squams are bound to each other by desmosomes which are held in place by LETKI
As squams move upwards, pH decreases (more acidic) LETKI disengages from KLK > KLK cleaves desmosomes > upper squams can be sloughed off
What is LETKI?
pH-sensitive inhibitor
Inhibits KLK
Why does pH decrease as you get closer to the surface of the epidermis?
It is more acidic because of the sebum that is excreted
Sebum = fatty acids
What two envelopes make up the water barrier?
- Cell Envelope
- Lipid Envelope
What is the cell envelope?
Insoluble proteins on the inner surface of the plasma membrane
What proteins are found in the cell envelope? (4)
Small proline-rich (SPR) protiens
Tanofibrils linked to the plasma membrane through elafin and involucrin
What are elafin and involucrin? Where are they found? What do they do?
Proteins
In the cell envelope
Link tanofibrils to the plasma membrane
What is the lipid envelope?
The lipid layer attached to the outer membrane
What is found in the lipid envelope?
Lamellar bodies
What causes granules to form?
Filligrin?
Talk to me about the development of lamellar bodies?
Begin synthesis in stratum spinosum
Increase in size (?) in the stratum granulosum
What three things do lamellar bodies hold?
- Ceramides
- Free Fatty Acids
- Cholesterol
Where are melanocytes located?
Rest on stratum basale with processes extending into stratum spinosum
What is the function of the epidermal-melanin unit? What is its ratio to keratinocytes?
Produces and secretes melanin
1:4 - 1:10 ratio epidermal-melanin unit:keratinocytes
What are the 4 major steps of pigment donation?
- Premelanosome formation
- Synthesis of melanin in early melanosome
- Mature melanosomes traffic to cytoplasmic end
- Keratinocytes phagocytose melanosomes
Talk me through pigment donation
Lysosomes filled with tyrosine and enzymes produced in the Golgi move towards cytoplasmic extensions > synthesize melanin on the way > move to cytoplasmic end > Keratinocytes phagocytose portion of plasmic extension and the melanosomes within > melanosomes enter into keratinocytes > melanin encases nucleus to protect it from UV damage
What are the 3 (4) factors in skin color variation?
- Degradation rate
- Pigment Type
- UV exposure
- Age
How does degradation rate affect skin color?
Light skin - melanin degrades faster; melanin is predominantly in basal keratinocytes
Dark skin - melanin degrades slower; melanin is distributed throughout the epidermis
How does pigment type affect skin color?
- Eumelanin (brown-black)
- Pheomelanin (red-yellow)
How does UV exposure affect skin color?
UV exposure causes the proliferation of melanocytes
Increase UV > Increase melanin production
How does age affect skin color?
Increase age > decrease melanocytes
What is Albinism? What causes it? What are the symptoms?
Can’t synthesize melanin in early melanosome
Lack tyrosinase > lack DOPA which is a required intermediate step
Symptoms: more susceptible to UV damage and skin cancer
What are Langerhan’s Cells? What is their function?
Antigen-presenting dendritic cells
Traffic to lymph nodes to present skin antigens to T-cells
Where are Langerhans’ cells located?
They move freely through the epidermis (and then through vasculature to lymph nodes)
What are Merkel’s cells? What is their function?
Associated with afferent nerve endings and function in cutaneous sensation (warmth, cold, contact, pain)
What is the structure of Merkel’s cell + neuron called?
Merkel’s Corpuscle
Are Merkel’s cell abundant or rare in the skin?
Abundant
Characteristics of neuron in Merkel’s corpuscle?
Loses myelination when it pushes through the basal lamina
Has plate-like ending at Merkel’s cell
What is UV radiation necessary for? What does too much UV radiation lead to?
Necessary for Vitamin D production
Too much > accumulations of DNA mutations > cancer
What is Basal Cell Carcinoma? Will it migrate? Where are they most likely to be found?
Large mass of basal cells
Typically won’t migrate
Found in body regions with exposure to the sun
What is Malignant Melanoma? Does it travel?
Melanocytes that migrate from the stratum basale
Yes It migrates
What are the ABCDE of malignant melanomas?
Asymmetric shape
Border is irregular
Color is black, red, blue
Diameter - advanced stages are larger than a pencil eraser
Enlarged/Evolved - change in shape, size, color
What are the two types of Malignant melanoma?
- Radial - just in the dermis
- Vertical - moved down into dermis and accessed blood vessels
What is Psoriasis? What causes it? What are the symptoms?
Autoimmune in ideology
T-cells cause basal cells to rapidly proliferate faster than desclamation which causes cambosis = thickening of the skin > infiltration of immune cells
Redness, inflammation
What is the most common form of Psoriasis?
Plaque Psoriasis
What is Vitiligo? What causes it? Symptoms?
Melanocytes are destroyed (by trauma or autoimmune disorder) > lack of pigmentation
White patches on skin or in hair
What are the two layers of the dermis?
- Papillary
- Reticular
What is the dermal papillae?
CT protrusions that project into the undersurface of epidermis which leads to interdigitate with epidermal ridges
What is the papillary layer composed of?
Loose Connective Tissue protrusions that project into the undersurface of the epidermis
What is the reticular layer composed of? Is it greater in thick or thin skin?
Irregular DCT
Interdigates with epidermal ridges
Greater in thick skin
What are langer lines? Why do doctors cut along them during surgery?
Regular lines of tension formed by the dense irregular connective tissue
Skin separates into consistent lines running parallel with underlying muscle
Surgeons cut along these lines to decrease scar tissue on muscle
What are epidermal ridges? What do they provide?
Unique pattern of ridges caused by the dermal papilla pushing up the epidermis
Increase grip and sensitivity
What is dermatoglyphics?
Analysis of finger prints
What are the 4 types of sensory receptors discussed in class?
- Pacinian Corpuscle
- Krause’s end blub
- Meissner’s Corpuscle
- Ruffini’s Corpuscle
Where is the Pacinian corpuscle located? What does it sense? Characteristics?
In the deep dermis and hypodermis
Pressure and Vibrations
Onion shape, concentric lamellae filled with fluid
Where is Krause’s end bulb located? What does it detect?
Deep dermis
Detects cold
Where is Miessner’s corpuscle? what does it detect? Where do you find them on your body?
Derminal papilli
Light touch
Find it on your fingers and lips
Where is Ruffini’s corpuscle? What does it detect?
Deep dermis
Skin stretch and torque
What surrounds Meisner’s corpuscles?
Surrounded by a capsule with Schwan-like cells around the fiber
What are 4 epidermal skin appendages?
- Hair Follicles
- Sebaceous glands
- Eccrine sweat glands
- Apocrine sweat glands
What is the hiar follicle responsible for?
Production and growth of hair
The coloration of hair is due primarily to content and type of what?
Melanin
Whare are the three segments of the hair follicle?
- Infundibulum
- Isthmus
- Bulb
What regions of the hair follicle does the infundibulum cover?
Surface to sebaceous gland
What region of the hair follicle does the isthmus region cover?
Infundibulum to erector pilli muscle
What region of the hair follicle does the bulb region cover?
Lower region
What is the function of the erector philli? Where is it located?
Attaches to bulge area of hair follicle and underside of the epidermis
Smooth muscle whose contractions lead to the release of sebum
Responsible for goosebumps
What are the two things the bulb region of the hair follicle consist of?
Dermal papilla
Matrix
What is the dermal papilla? What type of tissue is it? What function does it serve?
Invagination of the dermis into the matrix
LCT with capillaries and Nerves that serve as communication between papilla and cells in the matrix
Determines length and thickness of hair shaft
What is the matrix of the bulb of the hair follicle?
The germinative layer of the follicle
Gives rise to layers of hair follicle
Destruction of the dermal papilla in the bulb region would lead to what?
Destruction of the hair follicle
laser hair removal
What is the path cells take from bulb region to hair shaft?
Bulb > down external root shealth > matrix > hair shaft and external root shealth?
What are the three parts to the hair shaft?
Medulla
Cortex
Cuticle
Matrix cells have 6 differnent pathways: 1-3; ______, 4-6: ______
Hair Shaft
Internal root shealth
What is the medulla of the hair shaft? What tissue type is it made out of?
The central portion, scalp
Made of spongey, soft keratin
What s the cortex of the hair shaft? What tissue type is it made out of?
Makes up 80% of hair mass
Hard Keratin
What is the cuticle of the hair shaft? What tissue type is it made out of? How many cell layers thick is it?
6-8 layers of cells
Outermost layer
hard keratin
What are the characteristics of internal root health? When does it develop? When does it disintegrate? What is the significance of the disintegration?
Ridgid, cylindrical tube
Develops before hair and dictates how the hair lays
Desinegrates at the level of the sebaceous gland - creates lumen/opening for sebaceous content to be released
What are the three stages of hair growth?
- Anagen
- Catagen
- Telogen
Is hair growth cyclical or linear?
Cyclical
What happens in the anagen growth phase? Where on your body has 80% of the hair in this phase?
Period of growth in which new hair develops
More than 80% of hair present on the scalp is in this phase
What happens in the catagen growth stage?
A brief period in which growth stops
Bulb region pulls away from dermal papilla
What happens in the telogen growth phase? How long is this phase?
Long rest period in which follicle atrophies
Several Months
What are the two hair growth types?
- Terminal
- Vellus
What growth phase is terminal hair in? Where do you find terminal hair?
Anagen Phase
Scalp and Beard
What is vellus hair? Where do you find it?
Microscopic hair
Found on palms of hands, balls of feet, lips
When baldness occurs there is a change in the ratio of hair characteristics. There is more _____ and less ______ which is caused by an increase in _____
More vellus hair
Less terminal hair
Increase in DHT
How does an increase in dihydrotestosterone (DHT) cause in hair?
Increase DHT > miniaturization of hair follicle > terminal hair transitions to vellus hair
What is Propecia? What does it do?
Drug taken by people to stop balding
Blocks formation of DHT and thus the ability of follicle to miniaturize
What is the difference in the keratinization in skin vs hair? (3)
Skin: soft outer layer, Hair: hard, compact layer
Skin: continuous, over entire surface, Hair: intermittent
Skin: mature cells are similar, Hair: differentiate into various cell types
How do sebaceous glands develop? Where do they discharge sebum?
Develop as outgrowths of external root sheath
Discharge sebum into the infundibulum
How do the cells of the sebaceous glands vary based on location?
Cells closer to the edge have nuclei and are filling with sebum
As you move inwards you lose nuclei because the cell is overwhelmed with sebum and dies
What is pyknosis?
When the nuclei condense
occurs in sebaceous glands as cells become overwhelmed with sebum
What is sebum made out of? (2)
Lipids
Triglycerides
What are the two functions of sebum?
- Inhibit Bacterial growth
- Lubricate and protect hair and skin
What is a holocrine gland? What is an example?
When the release of sebum ruptures the membrane
So you’re not just releasing the contents of the cell but the cell itself
Sebaceous Gland
What is a branched acinar gland? What is an example?
A gland that has multiple pouches
Sebaceous Gland
What is a whitehead?
the opening to the sebaceous gland is closed by skin
What is a blackhead?
Opening of sebaceous gland is blocked by debris and oil but not blocked by skin
Where are eccrine sweat glands located?
Distributed over entire body surface except for lips and part of external genitalia
What kind of glands do eccrine sweat glands have>
Simple coiled glands
What is the function of eccrine sweat glands? How do they do this?
Thermoregulation
Cool the body by releasing contents (98% water and then salt, urea, ammonia, uric acid)
What is the histological difference between the secretory and duct part of the eccrine sweat glands?
Secretory: simple cuboidal epithelium, surrounded by mesothelium (contract and release)
Duct: stratified cuboidal epithelium, stains darker
Where are apocrine sweat glands located?
Distributed in axilla, areola of mammary gland, anus, external genitalia
What type of glands do apocrine glands have? where are these located specifically?
Tubular glands associated with hair follicles
In deep dermis and hypodermis
What is the function of apocrine sweat glands? When do they start secretion?
??
Starts at puberty
Nutrient for bacteria > bad odor
What are nails? Where are they located?
cornified structures on the distal phalanx of each finger/toe
What is the nail plate?
Dead, highly packed cells filled with hard keratin
What does the nail plate lie on? What is it made of?
Plate lies on nail bed
Epidermis, but instead of having a stratum corneum you have cortified nail plate
What attached the nail to the bone?
CT of the dermis
The nail is bounded by the ______ and the _______. What is their functions?
Cuticle (eponychium)
Quick (hyponychium)
Protect epidermal nail bed
