Ma - Skin

Front 1

Homeostatic Functions of Skin (6) and additional functions (2)

Back 1

1 Regulation of body temperature
2 Regulation of body fluid volume
3 Protection from U.V. radiation
4 Protection from minor traumas
5 Protection against disease organisms
6 Excretion of water, fats

Additional functions:
Sensory reception
Vitamin D synthesis

Front 2

Epidermis consists of 5 layers containing 4 cell types

Back 2

Layers:
1)stratum basale
2)stratum spinosum
3)stratum granulosum
4)stratum lucidum
5)stratum corneum

Cell types:
1) Keratinocytes
2) Melanocytes
3) Langerhans Cells
4) Merkel Cells

Front 3

Keratinocytes

Back 3

-predominant epithelial cell type
-deeper part of epidermis consists of proliferating cells which are continually being pushed toward the surface. as they get farther from their source of nutrients, they become filled with keratin, which is family of fibrous, insoluble proteins;
Soft (skin)
Hard (hair & nails)

Front 4

Stratum Basale

Back 4

a single layer; cells
contact basement membrane via hemidesmosomes and attach to their neighbors by desmosomes
contains mitotically active stem cells
polyribosomes in these cells synthesize tonofilaments in the first stage of keratin formation

Front 5

Stratum Spinosum

Back 5

Tonofilaments aggregate to form bundles (tonofibrils)

Front 6

Stratum granulosum - contains 2 types of granules

Back 6

-Keratohyaline granules contain filaggrin which promotes formation of tonofibrils
-Lamellar granules contain stacks of lipid bilayers. discharge their glycolipid contents (ceramides) into what becomes known as the lipid envelope, which contributes to the Epidermal Water Barrier

Front 7

Stratum Lucidum

Back 7

-most visible in thick skin
-is subdivision of stratum corneum
-dying squamous cells that lack nuclei
-filaggrin has combined with the tonofibrils to form a dense matrix

Front 8

stratum cornuem

Back 8

-Dead cells (squames)
-cells contain mostly keratin
-Tonofibrils surrounded
by keratohyalin matrix
-the keratins, filaggrin, and a protein called Loricrin contribute to the formation of a Cell Envelope just beneath the plasma membrane that also contributes to the EPIDERMAL WATER BARRIER

Front 9

Differences between thick and thin skin

Back 9

Thick skin has all 5 layers, is hairless, and found only on the palms of hand and soles of feet
Thin skin has no stratum lucidum visible by LM and on most parts of body has hairs

Front 10

melanocytes - taken up in which layers, desmosomal and hemidesmosomal attachments

Back 10

-involved in process of pigmentation
-taken up by cells of s. basale, s. spinosum
-melanin accumulates in these cells in these 2 layers to protect their nuclei from ultraviolet rays
-melanin granules formed in specialized vesicular organelles (melanosomes)
-No desmosomal attachment to neighbors, but has hemidesmosomes at basal lamina

Front 11

what rxn allow easy viewing of melanocytes

Back 11

DOPA reaction, which exploits the process of melanin formation so that you can see the cells

Front 12

how does melanin function, relation to skin color and suntans and albinism and Vitiligo

Back 12

scatters UV rays to prevent injury to the deeper epidermal layers.
in upper layers, melanin fuses with lysosomes and is degraded
-skin color is due to the rate of melanin degradation, not to differing number of melanocytes
-in lighter skinned ppl, it is degraded quicker and is more concentrated in the deep layers of the epidermis
-suntans result from increased melanin production as well as darkening of previously formed melanin granules
-Albinism results when there is no tyrosinase activity or its defective (tyrosine forms melanin)
-Vitiligo – loss of
melanocytes

Front 13

langerhans cells - found where, initiates what kinds of rxns, derived from and express what glycoprotein, part of what system

Back 13

-in upper stratum spinosum
-initiate cutaneous hypersensitivity reactions (allergic contact dermatitis)
-sensitizes you to specific antigens b/c they are antigen presenting cells that stimulate T lymphocytes.
-Derived from the bone marrow and exress the CD1 antigen binding surface glycoprotein

Belong to Mononuclear Phagocyte System

Front 14

Merkel Cells - found where, enable what reception and have what types of granules

Back 14

-on basement membrane in the stratum basale
-contain neurosecretory granules
-enable touch and pressure reception
-sensory nerves connected to them

Front 15

Dermis consists of 2 layers

Back 15

Papillary layer and reticular layer

Front 16

Papillary Layer - what type of CT, where is it, contains what (2), fingerprints? what does papillae do and how is it formed

Back 16

-loose, vascular, connective tissue
-just below epidermis
-contains many blood vessels and sweat glands
-extends up into epidermis and forms Papillae — increases surfaces area to increase number of hemidesmosomes connecting dermis to epidermis
-dermal ridges give rise to fingerprints

Front 17

Reticular Layer - what type of CT, what 2 types of collagen present, what are langer's lines, surgery precautions

Back 17

-dense, irregular, avascular connective tissue
-Type I and Type III collagen bundles form a network that contains glands and hair follicles
-Langer’s lines—lines of tension within the skin
-in surgery, want to cut parallel to Langer’s lines of cleavage to leave the smallest scar possible; if don’t cut parallel to lines, skin ‘puckers’ and forms a large scar

Front 18

Functions of Dermis (4)

Back 18

1) Functions of Dermis
a) Supports epidermis and binds it to hypodermis
b) Capillary networks of dermis nourish epidermis and regulate body temp
c) Common site of inflammatory and immune responses d) Contains sensory receptors (3 types) and nerves that supply the skin

Front 19

sensory receptors of dermis (3)

Back 19

1) Mechanoreceptors—stimulated by pressure/vibration
i) Free nerve endings - pain, temp, light touch
ii) Merkel endings - touch
iii) Pacinian corpuscles- afferent axon in center, vibration, deep pressure
iv) Krause endbulbls
v) Meissner’s corpuscles-light touch
vi) Ruffini corpuscles - stretch

2)Thermoreceptors are stimulated by heat or cold
3)Nociceptors convey pain

Front 20

Hypodermis - lies where, consists of what, contains what

Back 20

-lies below the dermis
-loose connective tissue, possible with fat cells
-it is the superficial fascia of gross anatomy
-contains largest vessels that supply the skin

Front 21

Sweat glands consist of two portions

Back 21

a secretory portion and a duct protion

Front 22

2 types of sweat glands found on body

Back 22

1) Eccrine glands
2) Apocrine Glands

Front 23

Eccrine Glands - produce what, epithelium, 2 types of cells found here and their secretions, main secretion, glands' association with hair follicles

Back 23

-light cells produce watery fluid while dark cells contain granules and produce glycoproteins
-duct portion has stratified cuboidal structure
-main secretion is hypotonic sweat is released by Merocrine Secretion (exocytosis) (thus regulate body temp and also deal with excretory organs)
-these simple coiled glands are not associated with hair follicles

Front 24

Apocrine Glands - duct opens up into what, present where, lumen size, epithelia of secretory and duct portion, mechanism

Back 24

-duct opens up into hair follicle
-probably contain pheromones
-present in the axillary and circumanal regions, labia majora and areolae of breasts.
-secretory portion has large lumen
-secretory portion has pseudostratified structure
-duct portion has stratified cuboidal portion
-mechanism is MEROCRINE, not apocrine

Front 25

Pilosebaceous apparatus - consists of

Back 25

hair follicle, its associated sebaceous gland, and arrector pili muscle

Front 26

Sebaceous Glands - production, mitosis, sebum (function)

Back 26

-produce lipid
-the mitotically active cells at the base divide and the daughter cells are pushed up through the layers, eventually die and the cells burst and the lipid content is secreted (holocrine secretion)
-Sebum acts as moisturizer, preventing chapping of skin, and is released into hair follicle

Front 27

Arrector pili muscle - consists of, function

Back 27

-Consists of band of smooth muscle arising from the papillary layer and attaching at angle to hair follicle
-pulls up on bottom of hair follicle and down on epidermis -->goose bumps (mechanism to conserve heat-traps air in hair)
-sebum released as well

Front 28

Hair Follicles - two sheaths found here, growth of hair, 3 concentric layers formed during growth of hair

Back 28

-External and Internal Root Sheath
-External root sheath surround a Germinal Matrix, whose cells proliferate and keratinize to form a hair:
-Growth of hair occurs as a matrix of cells proliferate and push older cells towar the surface. As they ascend, they become keratinized and form 3 concentric layers:
a) Central Medulla - soft keratin
b) Coretx of hard keratin - melanin pigment
c) Cuticle - outermost layer consisting of scale-like cells (hard keratin)

Front 29

Internal root sheath

Back 29

-formed by the matrix and is a form of soft keratin
- disappears at level of sebaceous gland ducts
- deep to the internal root sheath is the cortex of the hair follicle
- a central medulla is composed of soft keratin

Front 30

Hair Growth is not continuous, but occurs in 3 cycles

Back 30

-Anagen: growth phase (80-90% of hairs are in this stage at all times)
-Catagen: rest, growth stops
-Telogen: quiescent, follicle atrophy, hair loss

*in scalp, 80-90% of hairs are in the anagen phase at any one time

Front 31

Hair Color

Back 31

results when the cells of the matrix and cortex take up pigment released by melanocytes. Gray hair results from decrease in tyrosinase activity in the melanocytes

Front 32

4 parts of the nail

Back 32

1) nail plate: visible, analogous to stratum corneum
- growth occurs from the nail matrix to produce hard keratin which develops into the nail plate

2) Nail matrix - site of hard keratin formation and nail growth

3)Cuticle (eponychium): protective growth that slides over the proximal portion of the nail

4) Lunula: thick layer of partially keratinized cells
- is white area distal to the cuticle

Front 33

After a surgical Incision or Accidental Cut, within 24-48 hours epidermal continuity is re-established if the cut surfaces are brought in close proximity to each other through these 4 steps:

Back 33

1) Epidermis Thickens due to cellular proliferation at its cut edge.
2) Epithelial cell clusters migrate and grow along the cut margins of the wound until they meet to become continuous again.
3) As proliferation continues, fibroblasts produce collagen
4) Collagen is laid down and a scar forms by 2nd week. Full epidermal thickness is reached in 5 days. Scar formation.

*skin appendages (hair, glands) that have been lost will not reappear.

Front 34

Burns - 1st Degree Burn

Back 34

-causes the capillaries and venules of the papillary layer to dilate, making the skin red, ex: mild sunburn

Front 35

Burns - 2nd Degree Burn

Back 35

-characterized by blistering b/c of plasma leakage.
-accumulating plasma causes epidermis to peel off
- skin breaks to expose a raw area
- epidermis can be renewed and burn is healed because follicles and glands remain in tact

Front 36

Burns - 3rd Degree Burn

Back 36

-occurs when both the skin and subcutaneous tissues are damaged. Damage to subcutaneous tissues
with destruction of hair follicles and glands; epidermal renewal only at edges b/c hair follicules and glands are destroyed
– grafts needed b.c its a slow process and burn may never heal will unless a graft is applied (graft - healthy tissue or organ removed from one site and transplanted to another)

Front 37

Free Split Grafts

Back 37

-a thin layer of skin consisting of epidermis and upper part of dermis is shaved off in one area of the body and placed on the damaged surface.
-graft is nourished by the tissue fluid until a new blood supply is established.

Front 38

Free Full Thickness Grafts

Back 38

-give better cosmetic effects.
-epidermis and the entire dermis are removed from the donor site, which then must be covered wit ha split graft

Front 39

Artificial Skin

Back 39

-newest technology
-after removal of damaged skin from 3rd degree burn, remaining tissue is covered with a mixture of collagen and other ECM molecules to encourage dermal renewal.
-This layer is covered w/ a thin layer of silicon
-Once dermal layer has begin to regenerate, the silicon layer is removed and ulta-thin skin grafts from the patient are placed on the area.
-If patient does not have much healthy skin left, EPIDERMAL CELLS FROM THE PATIENT CAN BE CULTURED and seeded on the artificial skin; culturing provides a continuous source of the patient's own skin