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Cell Bio Exam 3 > 23 - Integument > Flashcards

23 - Integument Flashcards

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1
Q

Where do humans have extra skin folds? Why?

A

We have extra skin folds over certain joints to prevent skin from breaking upon flexion

  • Elbow
  • Knuckles
  • Knee joint
  • Achilles tendon
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2
Q

What does the integument include?

A

Integument

  • Skin
  • Its appendages
    • Sweat glands
    • Sebaceous glands
    • Hair
    • Nails
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3
Q

What are the functions of the skin?

A

Functions:

  • Protection
  • Regulation of body temperature
  • Reception
  • Absorption
  • Excretion
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4
Q

How does the skin protect?

A

Protection

  • The skin covers almost the entire body
  • The only exception is the nails
  • The skin protects from invasion from microorganisms and dehydration
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5
Q

How does the skin regulate body temperature?

A

Regulation

  • Sweat glands relsease sweat
  • This cools down the body when the sweat is evaporated
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6
Q

How does the skin function in reception?

A

Reception

  • Neuroreceptors may relay pain, touch, pressure and/or position to the central nervous system (CNS)
  • Thermoreceptors on our skin sense temperature
  • The skin allows us to form an image of the environment around us
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7
Q

How does the skin fucntion in absorption?

A

Absorption

  • Absorbs ultraviolet radiation for vitamin D production
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8
Q

How does the skin function in excretion?

A

Excretion

  • Eliminates waste products through sweat
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9
Q

What is the largest organ of the body?

A

The skin!

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10
Q

How do we classify skin?

A

There are two classifications:

  1. Thin skin
  2. Thick skin
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11
Q

Thin skin

A
  • Covers most of the body’s surfaces
  • Contains hair follicles, sebaceous glands, sweat glands, erector pilae muscles
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12
Q

Thick skin

A

Thick skin…

  • Covers the palms and soles of the feet
  • No hair follicles are found on these surfaces
  • No sebaceous glands
    • Sebaceous glands are oil-producing glands that are found in hair follicles
  • No erector pilae muscles
    • Erector pilae muscles are smooth muscles that anchor the root of the hair follicle
    • This erects hair when contracted in order to keep the body warmer
  • Sweat glands ARE present
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13
Q

What are the layers of the skin?

A

Two layers:

  1. Epidermis
  2. Dermis
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14
Q

Epidermis

A

Epidermis

  • Contains stratified squamous keratinaized epithelium
  • Divided into sub-layers called “strata”
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15
Q

Dermis

A

Dermis…

  • Composed of two layers of connective tissue that is found under the epidermis
    • Loose connective tissue that is more superficial
    • Dense irregular collagenous connective tissue that is deeper
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16
Q

What types of cells ar found in the epidermis?

A

Keratinocytes

  • Cells that accumulate keratin
  • This is the most common cell type found in the epidermis

Non-keratinocytes are also found in the epidermis

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17
Q

Ridges and papilla

A

Ridges (epidermis) and papilla (dermis)

  • The epidermis has folds that extend down into the dermis, known as epidermal ridges
  • The dermis sends projections into the epidermis known as dermal papilla
  • The two structure interdigitate
  • Function
    • Increase the surface area of the dermis and epidermis
    • Ensure the two layers stay together and don’t slip apart
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18
Q

Basal cells

A

Basal cells

  • Basal cells are a layer of epidermal cells that are found where the epidermis meets the dermis
  • Also called stratum basale
  • This is an area of intense mitotic activity
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19
Q

Basal cell migration

A

Migration

  • Cell from the stratum basale (basal cells) migrate to the surface of the skin
  • As they migrate, they acquire more keratin, become keratinized, then die and “slough off”
  • It takes 20-30 days for the cells to migrate from the strata basale to the superficial layer of the skin
  • This migration takes place mostly at night, so a good night sleep DOES make your skin look better (think beauty rest)
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20
Q

Non-keratinocytes

A

Non-keratinocytes are also found in the epidermis, but not as commonly as keratinocytes are

  • There are three types of non-kerantinocyes
    • Langerhans cells - defense cells, protect against invading antigens
    • Merkel cells - mechanoreceptors
    • Melanocytes - act as umbrellas to provide UV protection
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21
Q

Langerhan cells

A

Langerhan cells (dendritic cells, antigen-presenting cells)

  • Langerhan cells are derived from precurors in bone marrow
  • These precurosr cells enter the blood stream and travel to the epidermis
    • Once in the epidermis, they differentiate into Langerhan cells, which are
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22
Q

Cytoplasmic processes of Langerhans cells

A

Cytoplasmic processes

  • Extensions of the Langerhan cells into the extracellular space of neighboring cells are known as cytoplasmic processes
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23
Q

Function of Langerhans cells

A

Function

  • Foreign bodies which invade the skin are phagocytosed by the Langerhans cells
  • The LCs move a piece of what they ate (an antigen) to their cell surface
  • Then they travel to a nearby lymph node, and present that antigen to immune cells (lymphocytes)
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24
Q

Membrane-bound birbeck granules of Langerhans cells

A

Birbeck granules

  • Have a unique, tennis racket structure
  • Composed of a rod which is attached to a vesicle
  • The function of birbeck granules is not well understood, but it is thought that they are a part of the defense mechanism for the skin (protection from antigens)
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25
Q

Merkel cells

A

Merkel cells are found in the base of hair follicles and fingertips

  • Merkel cells are mechanoreceptors (tactile receptors)
    • Responsible for fine/discriminating touch
    • Allow our fingertips to feel detailed textures
  • Merkel cells attach to keratinocytes by desmosomes
  • Neurite complexes form from merkel cells, which contain unmyelinated nerve terminals
  • Merkel cells are found in the stratum basale
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26
Q

Melanocytes

A

Melanocytes arise from the neural crest

  • Melanocytes synthesize the pigment, melanin
  • Melanocytes are located in the stratum basale and the superficial dermis
  • Note that the spots and stripes on animals (leopard/zebra) are not only on the fur, but on the skin as well and are produced by concentrations of melanocytes
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27
Q

How do melanocytes convert tyrosine into melanin?

A

Melanocytes synthesize tyrosinase

  • Tyrosinase is an enzyme that turns tyrosine into malanin
  • Tyrosinase is synthesized at the rER then processed/packaged in the Golgi
  • The Golgi relseases tyrosinase in membrane vesicles called melanosomes
    • Melanosomes take up tyrosine from the cytoplasm
    • Tyrosinase inside the melanosomes turns the tyrosine into melanin
    • The melanosome because dark (now known as a melanin granules)
    • The melanin granules make their way into the cytoplasmic processes of melanocytes
28
Q

Release of melanin granules

A

Melanin granules can be found in the cell processes of melanocytes

  • Melanocytes lie in the stratum basale (bottom layer of the epidermis)
  • The cytoplasmic processes extend up into the stratum spinosum (some even enter nearby cells)
  • Melanocytes release their melanin granules into nearby cells via vesicles
  • The granules will surround the nucleus of neighboring cells - this covers and protects the DNA from UV radiation
29
Q

Number of melanocytes

A

This number varies in different areas of the skin

  • Dependent on the amound of sunlight the skin is exposed to
  • For example, there are fewer melanocytes in the axillary fossa than on the front of the arm
  • The TOTAL number of melanocytes in the body is about the same in all races
  • The pigmentation of skin is not due to the number of melanocytes present
30
Q

Pigmentation of the skin (differences between races)

A

Pigmentation is dependent upon…

  • Tyrosinase activity
    • Darker skin has increased activity
  • Number of melanin granules
  • Size of melanin granules
    • Darker skin has larger
  • Distribution of melanin granules
    • Lighter skin are located more in the nucleus
    • Darker skin is more scattered around the cell
  • Rate of breakdown
    • Dark skin break down slower
31
Q

Vitiligo

A

Vitiligo is an autoimmune disease

  • The body self-destructs melanocytes
  • The patchy skin pigmentation is due to a decrease or a complete loss of melanocytes in certain areas
  • All races and all ages can be affected
32
Q

Albinism

A

In albinos…

  • Melanocytes are present
  • However, melanocytes do not synthesize melanin due to a defect or absence of tyrosinase
33
Q

Malignant melanoma

A

Remember the ABCDEs…

  • A = Appearance (general appearance, is it itchy?)
  • B = Border (irregular, contour, notches, dimples)
  • C = Color (irregular, red/black/brown, pigmentation)
  • D = Diameter (larger than a pencil eraser needs removal)
  • E = Evolution (any recent changes)

Risk factors include heriditary, light skin, excessive sun exposure

34
Q

Strata of the epidermis

A

Strata = layers

  • The epidermis is the epithelial (most superficial) layer of the skin
  • The epidermis is avascular
    • No blood vessesls
    • The epidermis get nutrients from the capillaries from the underlying layer (the dermis)
35
Q

5 strata of thick skin

A

Strata of thick skin, from the bottom (innermost) layer out

  • Stratum basale
    • Bottommost layer, a lot of mitosis going on here
    • As the cells migrate upward, they aquire different morphological characteristics and accumulate more keratin
  • Stratum spinosum
    • Thickest layer
  • Stratum granulosum
  • Stratum lucidum
    • Actually a sub-layer of the stratum corneum
  • Stratum coreum
    • Most superficial layer
36
Q

Stratum Basale (Germinativum)

A

Stratum basale

  • Single layer of columnar cells
  • Basement membrane is found underneath them between the basal cells and the dermis
  • Anchors the dermis to the epidermis
37
Q

How are individual cells attached to each other and to the basement membrane within the stratum basale?

A

Attachments

  • Attached to each other, and more superficial epidermal cells, via desmosomes
  • Attached at the basal aspect to the basement membrane via hemidesmosomes
38
Q

What are the functions of the stratum basale?

A

Functions

  • Cell renewal (regermination of the epidermis)
  • Anchoring the epidermis to the underlying dermis
39
Q

Basal cell carcinoma

A

Caused by chronic sun exposure

  • Develops on the top of the head and in places where the skin is exposed to sunlight all the time

Pearly papule

  • Arises from cells found in the stratum basale
  • Slow growing and rarely metastasis
  • Can be excised without issue

Subepidermal blood vessels

  • These lesions contain their own blood vessels
40
Q

Stratum spinosum function

A

Function

  • Has numerous cell adhesions to give the skin its strength
  • Allows the skin to resist abrasions
  • This provides protection from outside microorganisms
41
Q

Stratum spinosum appearance

A

Appearance

  • Called “spinosum” because the cells appear to have spines sticking out from their cytoplasm
  • Look like “railroad tracks”
  • They are actually intercellular bridges between neighboring cells
42
Q

Desmosomal junctions between interdigitating processes of two adjacent keratinocytes

A

Adjacent cells

  • Two adjacent cells will project cytoplasmic processes towards each other
  • Attach via desmosomes (macula adherens)
  • If there were no desmosomal attachments…
    • Fissures in the skin would form due to injury
    • This would cause the body to be vulnerable to microorganisms (bacteria, viruses)
43
Q

Stratum granulosum

A

Stratum granulosum

  • In thick skin, granulosum contains 3 or 4 layers
  • Cells here have nuclei but they are fragmented
    • DNA is breaking down
    • Cells appear apoptotic
  • Cells have many granules
    • Keratohyalin granules (protein, contain keratohalin)
    • Membrane coating granules (lipid)
44
Q

Membrane-coating granules of the stratum granulosum

A

Membrane-coating granules

  • Relsease lipid into the extracellular space
  • Lipid forms sheet of waterproof material
    • Good for sheilding the body from water gain/loss
    • But the lipids also impede diffusion of nutrients and oxygen, causing cell death beyond this layer
45
Q

Stratum lucidum

A

Stratum lucidum

  • Allows light to pass through - it is the light staining layer
  • Not very visible in micrographs of thin skin
  • It is a sublayer of the stratum coreum
  • Contains ONLY dead cellular material
  • There are NO cytoplasms or organelles present
46
Q

Stratum Corneum

A

Stratum corneum

  • Very thick in the thick skin
    • Recall that the thickest skin is found in the soles of our feet and also to a lesser extend in the palms of our hands
  • This is a lyer of DEAD cellular material
  • Lots of keratin is found here (protective material)
47
Q

Strata of thin skin

A

Thin skin contains…

  • Stratum corneum (thin)
    • There is an absence of a definitive stratum lucidum, however individual cells are present
    • There is also an absense of a definitive stratum granulosum, hoever individual cells are present
  • Stratum spinosum
  • Stratum basale
48
Q

Ichthyosis

A
49
Q

Dermis

A

Dermis

  • Connective tissue layer of the skin
  • Contains two layers
    • Papillary layer
    • Reticular layer
50
Q

Papillary layer of the dermis

A

Papillary layer

  • Most superficial layer of the dermis that extends into dermal papilla
  • Composed of loose connective tissue
    • Has fibroblasts, macrophages, mast cells, plasma cells
  • Functions to protect the body from invasion by microorganisms
51
Q

Papillary layer of the dermis in THICK skin

A

Thick skin

  • In areas subject to “mechanical stress” (palms and soles), you will see…
    • Prominant epidermal ridges (dermal papilla)
    • True dermal ridges
52
Q

Reticular layer of the dermis

A

Reticular layer

  • Provides tensile strength
  • Thickest layer of the dermsi
  • Contains collagen bundles
    • Many bundles will run in different directions (look like pink ribbons)
    • Prevent the skin from breaking apart
  • Also contains some elastic fibers
53
Q

What do the dome-shaped ridges of thick skin form?

A

Finger prints!

54
Q

Dermis vs. Hypodermis

A

The hypodermis is NOT part of the skin

  • Dermis contains…
    • Ducts of sweat glands
    • Portions of hair follicles
    • Sebaceous glands
  • Hypodermis: the layer underneath the dermis
    • Also known as the superficial fascia
    • Contains some adipose tissue
    • Again, NOT part of the skin
55
Q

Four types of receptors found in the skin

A

There are four types:

  1. Free nerve endings
    • Pain and temperature receptors
  2. Pacinian corpuscle
    • Detects pressure and vibrations
  3. Meissner’s corpuscle
    • Mechanoreceptors for discriminatory, fine touch
    • Found in dermal papilla
  4. Krause end bulbs
    • Function is unclear
56
Q

What are the two types of sweat glands in our body?

A
  1. Eccrine
  2. Apocrine
57
Q

Which of the two sweat glands is the “ordinary” sweat gland found throughout the body?

A

Eccrine sweat glands

  • Found in most of the skin
  • Activated in heat and exercise
  • They squirt out their products onto the skin
  • Also function in the excretion or expulsion of waste product
58
Q

What kind of cells help with expuslion in eccrine sweat glands?

A
  • These glands have myoepithelial cells which assist in the “expulsion” of the secretory product (sweat) from the secretory unit
59
Q

What type of secretory method is used in eccrine sweat glands?

A
  • Sweat glands utilize the merocrine secretory method (they only secrete the product)
60
Q

What is the innervation of eccrine sweat glands?

A

Innervation

  • Postganglionic - sympathetic fibers
61
Q

What type of duct does the eccrine sweat gland have?

A

Simple coiled tubular gland

  • You will see the secretory portions lined with simple/stratified, columnar/cuboidal epithelium
  • Some ducts will be made up of two layers of cuboidal epithelium
  • You will see a long coiled tube
62
Q

What type of sweat gland is specialized to have a huge lumen and is found in areas producing large amounts of sweat?

A

Apocrine sweat glands

  • Found in the axilla, areola of the nipple, anal region
  • Merocrine secretion (secretory product only)
  • Innervated by the sympathetic NS
  • Produce large amounts of sweat
    • Sweat itself is odorless
    • Bacteria on our skin breakdown products of sweat - this produces the odor
63
Q

What do sebaceous glands produce?

A

Sebaceous glands are the oil producing glands of the body

  • Sebaceous glands are induced by hormones and holocrine secretions
  • The secretory product is know as sebum
    • Empties into the hair follicle
    • Cells themselves are part of the sebum
  • Mature cells of the sebum become part of the secretion
64
Q

What are the parts of a hair follicle?

A

Hair follicle

  • Hair bulb (at base of hair) - encloses the dermal papilla
  • Medulla - moderate keritinization
  • Cortex - keritiniaed
  • Cuticle - keritinized
  • Internal root sheath - some keritinization
  • External root sheat - not part of the hair (cells outside of the internal root sheath)
  • Glassy membrane (like a bsement membrane)
  • Connective tissue
65
Q

Arrector pili muscle

A

Smooth muscle

  • Attaches to the hair follicle midway and obliquely
  • Functions to rais the hair
  • “Cradles” the sebaceous gland
66
Q

Nail plate

A

Nail plate

  • The nail plate is a dense keratinized plate
  • Rests on the nail bed (stratified squamous epithelium)
67
Q

Nail matrix

A

Nail matrix

  • Epithelium under nail root
  • Growth occurs here

Cell Bio Exam 3 (8 decks)

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