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MSK I > Lecture 1 + 2 > Flashcards

Lecture 1 + 2 Flashcards

1
Q

Describe the epidermis?

A

keratinized stratified squamous epithelium

derived from the ectoderm

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2
Q

Describe the dermis?

A

dense connective tissue

derived from the mesoderm

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3
Q

Describe the hypodermis?

A

deep compared to the dermis

can also be called the subcutaneous fascia

contains variable amounts of adipose tissue arranged in lobules and separated by connective tissue

can find hair follicles, glands, and mechanoreceptors

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4
Q

What are the associated appendages of the skin?

A
  1. hair follicles and hair
  2. sweat glands
  3. sebaceous glands
  4. nails
  5. mammary glands
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5
Q

Functions of the skin?

A
  1. barrier
  2. immunological role
  3. homeostasis
  4. sensory info
  5. endocrine function
  6. excretion
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6
Q

What are the functions of keratinocytes?

A
  1. produce keratin- mainly in the stratum basale
  2. produce keratohyalin granules - spinosum and granulosum layers
  3. contributes to the formation of the epidermal water barrier
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7
Q

What do keratinocytes look like under a microscope?

A 
Has a basophilic appearance
has organelles (lots of free ribosomes)  
keratin filaments (cytoskeletal)
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8
Q

melanocytes under a microscope?

A

found in the basal layer

appear clear with large elongated nuclei

cytoplasmic processes extend between keratinocytes

no desmosomal connections but are attached to the basal lamina via hemidesmosome like structures

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9
Q

Functions of the melanocytes?

A

produce melanin that is transferred to surrounding keratinocytes for UV protection

skin color is the amount and ratio of melanin types present

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10
Q

How is melanin produced?

A

oxidation of tyrosine to DOPA to melanin

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11
Q

What are the two forms of melanin?

A
  1. Eumelanin - brownish

2. pheomelanin - reddish

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12
Q

Describe the function of eumelanin?

A

protects against UVR damage

degrades faster in light-skinned individuals

scatter and absorb UV rays and eliminate free-radicals

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13
Q

Describe the function of pheomelanin

A

allows more light to pass, thus increasing Vit. D production

found more common in atypical nevi and melanomas

increased oxidative damage

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14
Q

Function of langerhan’s cells?

A

Encounters, processes and expresses antigens (APC)

migrates to lymph node to present antigen to T-cell

involved in hypersensitivity reactions

expresses both MCH I and MCH II and receptors for IgG

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15
Q

langerhan’s cell structure?

A

the nucleus is indented making the nuclear profile uneven

have tennis racquet shaped granules- function is unclear

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16
Q

Merkel’s cell structure?

A

Have desmosomes and contain keratin filaments

nucleus is lobed

cytoplasm contains neurosecretory granules

possess antigenic markers of both epidermal and neural

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17
Q

What is the function of the Merkel cell?

A

Detect touch sensation

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18
Q

What is thick skin?

A

Found only in the soles and palms

usually hairless and has a much thicker epidermis

carries a stratum lucidum

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19
Q

What is thin skin?

A

found most places

thinner epidermis compared to thick skin

hair follicles are widespread

20
Q

What are the 5 layers of the epidermis?

A
  1. stratum basale - differentiating cells
  2. stratum spinosum - maturing and slowly dying cells
  3. stratum granulosum - cells that are about to die
  4. stratum lucidum - only found in thick skin
  5. stratum corneum- dead keratinized cells
21
Q

describe the stratum basale?

A

single layer of cuboidal or columnar cells (mitotically active)

has merkel cells, melanocytes, and keratinocyte stem cells

rests on the basal lamina (attached by hemidesmosomes)

extensive cell junctions (desmosomes)

22
Q

Describe the stratum spinosum?

A

several cell layers thick

keratinocytes are larger than those seen in the basale

make cytokeratins/ keratin filaments

exhibit many cytoplasmic processes or spines

gradually change appearance as they move closer to the surface

cells connected to each other by desmosomes

langerhan’s cells are found in this layer

23
Q

Describe the stratum granulosum?

A

most superficial of the nonkeratinized cells

one to three layers thick

contains conspicuous granules which give the cells a granulated look

keratinization begins (soft keratin): loss of organelles, thickened cell membrane, and decreased pH

lamellar bodies: epidermal water barrier

24
Q

Describe the stratum lucidum?

A

only well seen in thick skin

in a microscopic view, it appears as a light highly refractile eosinophilic band

keratinization process is well advanced

25
Q

Describe the stratum corneum?

A

several layers of dead keratinocytes

keratinocytes are filled with keratin aggregated into tonofibrils

abrupt transition from granulosum

26
Q

What forms the epithelial water barrier?

A

the cell envelope and the lipid envelope

27
Q

how does keratinization occur?

A
  1. keratin is accumulated in the cell cytoplasm
  2. cells lose organelles, cytoplasm, and nuclei
  3. more tonofilaments are formed; fibrils are arranged by filaggrin
  4. well cells reach the upper layers the desmosomes are broken apart
  5. cells are sloughed off (takes about 47 days)
28
Q

What are characteristics of the dermis?

A
  1. gives strength and elasticity to the skin
  2. contains many appendances such as nerve corpuscles and glands
  3. contain smooth muscle that movie hair
29
Q

What are the two layers of the dermis?

A

the papillary layer and the reticular layer

30
Q

Explain the papillary layer of the dermis?

A

It is the superficial layer and is composed of mainly loose connective tissue (more cells)

contains blood vessels
mainly type I and III collagen fibers
the elastic fibers are thin and irregular
contains Meissner corpuscles

31
Q

Explain the reticular layer of the dermis?

A

thicker and deeper than the papillary layer

dense irregular connective tissue (less cells)

has thick irregular bundles of type I collagen and thicker elastic fibers

32
Q

What three parts of the dermis are responsible for fingerprints and allow for more mechanical stress?

A

epidermal ridge, dermal ridge, and dermal papillae

33
Q

What are the functions of nails? what are they?

A

help with grip and gives protection

they are hard plates of epidermal keratinized cells

34
Q

What are the three parts of the hair follicle?

A
  1. Infundibulum
  2. isthmus
  3. inferior segment
35
Q

What makes up the pilosebaceous organ?

A

the hair follicle, sebaceous gland, and smooth muscle

36
Q

What are the three phases of hair growth?

A
  1. long phase of active growth (anagen)
  2. short phase of involution (catagen)
  3. short inactive phase (telogen)
37
Q

Characterize the sabaceous glands?

A

simple branched acinar gland

the secretory portion is located deeper in the dermis
opens into hair follicle
the secretion is holocrine
product is sebum

these glands prevent hair from becoming dry and brittle

38
Q

Explain eccrine sweat glands?

A

they are present in both thick and thin skin

simple coiled tubular glands

the merocrine secretion contains clear cells, dark cells, and myoepithelial cells

39
Q

What part of the PNS innervates the eccrine sweat glands?

A

sympathetic via cholinergic neurotransmitters

40
Q

What kind of epithelium is the eccrine sweat gland ducts.

A

stratified cuboidal epithelium

41
Q

explain the apocrine glands?

A

found only in the armpit and perineum

coiled tubular glands

secretes pheromones by merocrine pathway

42
Q

what type of epithelium lines the apocrine gland ducts?

A

stratified cuboidal

opens into hair follicle

43
Q

What part of the PNS innervates the apocrine gland?

A

sympathetic via catecholamine neurotransmitters

44
Q

characteristics of the pacinian corpuscle?

A

Large ovoid

deep dermis/hypodermis

senses deep pressure and vibration

45
Q

What is a meissner corpuscle function?

A

light touch

46
Q

What is the function of ruffini’s corpuscle

A

stretch and torque

MSK I (23 decks)

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