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Histology > Integument > Flashcards

Integument Flashcards

1
Q

Largest organ of body?

Total body mass?

A
  • skin

- 15-20% of the total body mass

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2
Q

Skin functions?

A

-protection (barrier function), sensation, thermoregulation (skin participates in homeostasis), and immune response

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3
Q

4 main components of the skin

A
  • epidermis
  • epidermal derivatives
  • dermis (cutis)
  • hypodermis (subcutis)
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4
Q

Epidermis composition?

A
  • composed of the keratinized stratified squamous epithelium that grows continuously and desquamates from the surface
  • derived from ectoderm
  • most superficial layer of the skin
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5
Q

What are the epidermal derivatives?

A
  • hair follicles and hair
  • sebaceous glands
  • eccrine and apocrine sweat glands
  • mammary glands
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6
Q

Dermis composition?

A
  • composed of connective tissue that provides support for the skin and hosts epidermal appendages, blood vessels, and nerves
  • derived from mesoderm
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7
Q

Hypodermis composition?

A
  • contains variable amount of adipose tissue
  • is equivalent to the subcutaneous fascia described in gross anatomy
  • function is insulation
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8
Q

Five layers of the keratinized stratified squamous epithelium from deepest to superficial?

A
  • stratum basale (germinativum)
  • stratum spinosum
  • stratum granulosum
  • stratum lucidum
  • stratum corneum
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9
Q

Principle cells of the epidermis?

Life cycle of these cells?

A

-keratinocytes

  • least differentiated cells are found in the basal layer
  • undergo maturation process as they move up within the epidermis
  • when reach apical surface, undergo apoptosis, and are sloughed off the surface
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10
Q

Stratum basale: location? Characteristics?

A
  • deepest layer (single cuboidal or columnar cells resting on the basement membrane), separated epidermis from the dermis
  • mitotically active cells that give rise to new keratinocytes that progress to apical layers
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11
Q

What links the keratinocytes to the basal lamina? What can go wrong?

A
  • hemidesmosomes link keratinocytes of the stratum basale to the basal lamina
  • autoimmune reactions to hemidesmosomes or basement membrane components result in blistering diseases (bullous pemphigoid)
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12
Q

Stratum spinosum characteristics?

A
  • several cells thick
  • larger than stratum basale and connected to each other by numerous desmosomes (look like “spines” in the fixed tissue in a light microscope, spinosum)
  • cells are more of less spherical in shape
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13
Q

Stratum granulosum characteristics?

A
  • contain keratohyalin granules (stain intensely)

- cells are flattened and squamous in appearance

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14
Q

Stratum lucidum location and characteristics?

A
  • only in thick skin
  • highly refractive layer that contains cells that have gone through apoptosis and their nucleus and organelles became disrupted
  • stains very lightly with H&E
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15
Q

Stratum corneum characteristics?

Spaces b/t cells?

A
  • most differentiated cells in the epidermis
  • lost their nucleus and cytoplasmic organelles and became filled entirely with keratin filaments
  • b/t cells are filled with lipid, which make this layer impermeable to water
  • this layer stains dark with H&E
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16
Q

Four major cell types in the epidermis?

A
  • keratinocyte
  • melanocyte
  • Langerhans’ cells
  • Merkel’s cells
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17
Q

Keratinocyte function?

A
  • principle cell type in epidermis

- production of keratin and formation of epidermal water barrier

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18
Q

Cell structure of keratinocyte?

A
  • cytoplasm contains numerous free ribosomes and intermediate (keratin) filaments
  • bound to each other by desmosomes
  • have keratohyalin granules and lamellar bodies
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19
Q

Keratohyalin granules location?

What two main proteins?

A
  • appear in the upper layers of the epidermis (stratum granulosum)
  • filaggrin and trichohyalin

-are aggregates of proteins and are not surrounded by a membrane (not secretory granules

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20
Q

Keratinization?

A

-as keratohyalin granules are released into the cytoplasm of keratinocytes they promote the aggregation of keratin filaments into fibrils

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21
Q

Lamellar bodies role?

Location?

A
  • membrane-bound vesicles that contain a mixture of lipids, which play a key role in making the epidermis a water-impermeable layer
  • secreted by exocytosis into the intercellular spaces
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22
Q

Extracellular hydrophobic barrier

A
  • lipids from lamellar bodies coat the keratinocytes and form an extracellular hydrophobic barrier which extend b/t the cells
  • disruption of the epidermal water barrier (in severe burns) can lead to life-threatening loss of body fluid
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23
Q

Tumors derived from keratinocytes?

A
  • squamous cell carcinoma-malignant tumor that is derived from the keratinocytes of the stratum spinosum
  • basal cell carcinoma-most common type of skin cancer and is derived from the keratinocytes within the stratum basale
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24
Q

Melanocytes derived from?

A

-derived from neural crest cells and are mostly found within the stratum basale (pituitary gland helps migrate)

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25
Q

Melanin

A
  • produced my melanocytes

- protects organism against the damaging effects of the ultraviolet irradiation

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26
Q

Cell structure of melanocytes?

A
  • have rounded cell body and numerous long processes that extend between the keratinocytes into the stratum spinosum
  • because of processes are called dendritic cells (NOT APCs)
  • tips of processes are phagocytosed by the neighboring keratinocytes, which incorporate melanin granules into their cytoplasm
  • NOT bound to other cells by desmosomes
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27
Q

Melanosomes? Location?

A

Granules containing melanin

-found neat the ends of the cellular processes of melanocytes

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28
Q

Malignant tumor of melanocytes?

A
  • called malignant melanoma
  • small melanomas are easily excised (radial growth phase)
  • larger tumors quickly penetrate into the dermis and metastasize via lymphatic vessels (vertical growth phase)
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29
Q

Lagerhans’ cells

A

Monocyte-derived dendritic-appearing cells of the immune system present in the epidermis
-part of the mononuclear phagocytic system

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30
Q

Function of Langerhans’ cells?

A
  • APCs of the epidermis
  • generate skin immune response when pathogens enter the skin
  • after accumulating antigens within the epidermis, migrate (via lymphatic vessels originating in the dermis) to lymph nodes where they present these antigens to lymphocytes
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31
Q

Langerhans’ cells description?

A
  • dendritic cells with long branching processes and a nucleus that is indented in multiple places
  • cytoplasm contains racquet-shaped endosomes called Birbeck granules
  • not bound to other cells by desmosomes
32
Q

Merkel’s cells

A

-epidermal cells responsible for cutaneous sensation

33
Q

Merkel’s cells function? Location on body?

A
  • mechanoreception
  • make synaptic contacts with sensory nerve fibers
  • most abundant in the areas of acute sensory perception (fingertips)
34
Q

Merkel’s cells location in the body?

Cytoplasm?

A
  • modified epidermal cells and are bound to adjacent keratinocytes by desmosomes
  • located in the stratum basale and form synaptic contacts with afferent nerve fibers
  • cytoplasm contains numerous dense-core granules that are released into the synaptic cleft and act as neurotransmitter to excite the afferent myelinated nervefibers
35
Q

Merkel’s cell carcinoma

A
  • arises from uncontrolled growth of Merkel cells

- rare skin cancer that proves fatal in ~1/3 of patients and should receive immediate treatment

36
Q

Dermis composed of?

A

-connective tissue and receives extensive vascular and nerve supply

37
Q

Describe the junction between the epidermis and dermis.

A

-attachment of the epidermis to the dermis is enhanced by the increased surface between the two tissues

38
Q

Rete ridges and dermal papillae

A

Rete ridges-numerous ridges in the epidermis

Dermal papillae- numerous projections of the dermis

*junction b/t the epidermis and dermis

39
Q

Cells of the dermis are?

A

-the same cells that are found in connective tissue proper

40
Q

Layers of the connective tissue of the dermis?

A

-two layers, the more superficial papillary layer and the deeper reticular layer

41
Q

Papillary layer (superficial) consists of?

A
  • loose connective tissue immediately beneath the epidermis
  • collagen fibers in this part of the dermis typically do not form large bundles and form a delicate network
  • relatively thin and includes substance of the dermal papillae
42
Q

Reticular layer (deep) consists of?

A
  • deep to papillary layer
  • thicker and less cellular than the papillary layer
  • dense irregular connective tissue characterized by numerous thick, irregular bundles of collagen type I
43
Q

Dermis vasculature

A
  • receives extensive blood supply important for thermoregulation
  • vascular plexuses and capillary loops
44
Q

What are Capillary loops?

A
  • extend into the dermal papillae and bring blood towards the surface of the skin
  • pink skin color results from the blood present in these capillary loops
45
Q

Superficial vascular plexus of blood vessels..

A
  • are found at the junction between papillary and reticular layers of the dermis
  • capillary loops are supplied by this plexus
46
Q

Deep vascular plexus is located?

A

-at the cutaneous/subcutaneous junction

47
Q

Lymphatics in dermis location?

A
  • lymphatic capillaries are usually found in the dermal papillae
  • they drain into lymphatic vessels deeper in the dermis (why tumors can metastasize from the skin quickly)
48
Q

Hypodermics characteristics

A
  • variable thickness throughout the body and is composed mostly of adipose tissue, loose connective tissue, smooth muscle, and sometimes striated muscle
  • layer is major energy storage site and provides insulation
49
Q

What are three epidermal appendages?

A

-pilosebaceous apparatus, eccrine and apocrine sweat glands

50
Q

Pilosebaceous apparatus includes..

A

-hair follicles and their product, hair and sebaceous glands

51
Q

Hair follicle location and function?

A
  • represents an invagination of the epidermis, in which hair is formed
  • responsible for production and growth of the hair
52
Q

What is hair composed of?

A

-composed of keratinized cells (keratinocytes) that develop from the hair follicles

53
Q

What are the parts of the hair?

A
  • hair part located in the follicles is called the root

- part that projects above the surface of the epidermis is called the shaft

54
Q

What are the layers of the hair?

A
  • innermost layer is the Medulla, contains large vacuolated cells
  • surrounding the medulla is the Cortex, which contains live cells accumulating keratin
  • outermost layer of the hair is formed of dead squamous cells and is called the cuticle
55
Q

What to sebaceous glands do?

A
  • secreate sebum and coat the hair and skin surface
  • sebum is produce via holocrine secretion (as the cell becomes filled with the lipids it produces, it goes through apoptosis and the cell contents are released into the hair follicle)
56
Q

Sebaceous gland development?

A
  • develop as outgrowths of the follicular wall
  • new cells are produced by mitosis of basal cells adjacent to the basal lamina
  • as cells mature they move up towards the lumen of the follicle
57
Q

Immature and mature cells of the sebaceous glands

A
  • proliferating immature cells are located adjacent to the basal lamina. As more cells are produced they are “pushed” out of this layer and begin to mature
  • maturing cells enlarge, have abundant SER and accumulate lipid droplets
  • mature cells are large, terminally differentiated cells, which are filled w/ large lipid droplets. these cells undergo apoptosis:nuclei becomes pyknotic and these cells break apart as they are released into the hair follicle
58
Q

Arrector pili muscle in the pilosebaceous apparatus

A
  • connects the deeper part of the follicle to the superficial dermis
  • composed of smooth muscle
  • contraction of these muscles causes the erection of hairs and produces “goose bumps” on the human skin
  • innervation of this smooth muscle is by the sympathetic nervous system
  • furred mammals- elevation of the hair is important in thermoregulation
59
Q

Eccrine sweat glands location and function

A
  • distributed over the entire body except the lips and parts of the genitalia
  • thermoregulation via the production of sweat
60
Q

Eccrine sweat gland shape and cells

A
  • are simple cooler tubular glands that are NOT associated with the hair follicle
  • each gland is a blind-ended tube that consists of a secretory portion and a duct
  • duct is lined with stratified cuboidal epithelium
61
Q

Secretory portion of eccrine sweat gland cells?

A
  • lined with stratified epithelium
    1. clear cells-produce the watery component of the sweat (light stain due to glycogen)
    2. dark cells- have abundant RER and glycoprotein granules. They secrete the proteinaceous component of the sweat via merocrine secretion
    3. Myoepithelial cells produce contractions that help discharge sweat into the duct (actin/myosin)
62
Q

Apocrine sweat glands shape

A
  • large-lumen tubular glands associated with hair follicles
  • structurally similar to eccrine sweat glands in having a coiled tubular secretory portion and duct lined with stratified epithelium –different in having more dilated secretory segments, due to the fact that they store the secretion within the lumen
  • ducts open into the hair follicles
63
Q

Apocrine sweat glands secretion and location

A
  • secretory part contains a single type of secretory cell
  • secrete a protein-rich secretion containing pheromones via merocrine secretion
  • only found near the lips, in the axilla, in the areola of the breast, and in the perineal regions
  • small and inactive until puberty, when the increase in size in response to steroid hormones
64
Q

Mammary glands are..

A

-modified apocrine sweat glands

65
Q

Mammary glands develop?

A
  • under the influence of sex hormones
  • like apocrine sweat glands, the mammary glands are small and inactive until puberty, when in females they enlarge in response to steroid hormones
66
Q

Prolactin

A
  • initiates secretion in mammary glands

- secreted by the adenohypophysis

67
Q

Oxytocin

A
  • ejection of milk from the breast
  • released from neurohypophysis and is due to the action of myoepithelial cells located between secretory cells and the basal lamina
68
Q

Structure of the mammary gland

A
  • composed of 15 to 20 irregular lobules
  • each lobule is branched tubuloalveolar gland embedded into loose connective tissue
  • spaces between lobules are filled with dense irregular connective tissue
69
Q

Lactiferous sinuses

A

-near the nipple the ducts of tubuloalveolar glands dilate to form lactiferous sinuses, lined with stratified cuboidal epithelium (where milk is stored)

70
Q

Lactiferous ducts

A
  • terminal parts of the ducts
  • open within the mammary papilla, or nipple
  • lactiferous ducts are lined with stratified squamous epithelium
71
Q

Innactive (non-lactating) mammary glands

A

-tubuloalveolar glands within the inactive mammary gland do not contain secretory end-pieces and contain large amounts of connective tissue

72
Q

Mammary glands and pregnancy

A

-undergo dramatic proliferation and development as they start actively secreting milk and become active or lactating mammary glands

73
Q

Progesterone

A
  • under influence of progesterone the compound tubuloalveolar glands quickly develop secretory end-pieces that proliferate at a significant rate
  • at the same time the CT regresses to allow for the glandular growth
  • both merocrine and apocrine secretion are involved in the production of milk
74
Q

Merocrine secretion of milk

A

-the proteinaceous component of milk is synthesized in the RER and packed within the Golgi apparatus

75
Q

Apocrine secretion of milk

A
  • fatty (lipid) component of milk is formed within the cytoplasm
  • larger droplets coalesce and migrate towards the apical portion of the cell, where they project into the lumen of the acinus
  • droplets are then invested into the envelope formed by the plasma membrane and released with apocrine secretion

Histology (5 decks)

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