Dermis and Subcutaneous Tissue

Question 1

what is dermis? function?

Answer 1

middle layer of the skin and is derived embryologically from the mesoderm. It provides the skin with structure and flexibility. Additional functions of the dermis include vascular support for the skin, immunologic protection, and nerve sensation.

Question 2

dermis contains?

Answer 2

adnexal structures such as hair follicles, eccrine (sweat) glands, sebaceous (oil) glands.

Question 3

2 layers of dermis called?

Answer 3

superficial layer is called the papillary dermis and the lower layer is called the reticular dermis.

Question 4

papillary dermis qualities?

Answer 4

interdigitates with the rete ridges (also called rete pegs) of the epidermis. It is more cellular and has fine, loosely woven collagen

Question 5

reticular dermis qualities?

Answer 5

has fewer cells and contains coarse, tightly packed collagen.

Question 6

ECM fxns?

Answer 6

ECM is important as a scaffold that gives the dermis its structure and strength. In addition, the ECM can regulate cell functions

Question 7

cell functions regulated by ECM?

Answer 7

adhesion and migration, division, and apoptosis. These functions play an important role in development, wound healing, tumorigenesis, and inflammation

Question 8

main components of ECM?

Answer 8

collagen, elastic fibers, and the extrafibrillar matrix

Question 9

collagen makes up?

Answer 9

20% of the skin’s volume and 75% of the dry weight of the skin

Question 10

Most dermal collagen is produced by?

Answer 10

fibroblasts and provides structural integrity to the skin

Question 11

types of collagen? in skin?

Answer 11

28 types of collagen, with 12 types present in the skin. Collagen I is the most abundant collagen of the skin, followed by collagen III

Question 12

During embryogenesis and wound healing, the relative proportion of which increases?

Answer 12

type III

Question 13

which found in basement membrane zone?

Answer 13

Collagen IV, VII, and XVII (also known as BP180)

Question 14

elastic fibers fxn?

Answer 14

responsible for skin elasticity, the ability to be stretched and still return to the original form

Question 15

elastic fibers composed of?

Answer 15

microfibrils, primarily made up of fibrillin, and amorphous elastin.

Question 16

ground substance (extrafibrillar matrix) of the skin?

Answer 16

non-collagen, non-elastin component of the dermis. It is composed of water, electrolytes, plasma proteins, and proteoglycans

Question 17

proteoglycan composition?

Answer 17

composed of a protein core and long-chain polysaccharides called glycosaminoglycans (GAGs)

Question 18

fxn of GAGs? most common GAG?

Answer 18

bind water. hyaluronic acid, which is unique for not being covalently linked to a protein

Question 20

predominant cells of the dermis?

Answer 20

fibroblasts, derived from mesoderm

Question 21

main role of the fibroblast?

Answer 21

production and secretion of the components of the extracellular matrix.

Question 22

resident immune cells?

Answer 22

Macrophages and mast cells

Question 23

composition of papillary dermis and reticular dermis?

Answer 23

arterioles and venules. lymphatics also present in dermis

Question 24

BV of dermis do what?

Answer 24

circulation, temperature regulation, leukocyte trafficking, and wound healing

Question 25

function of autonomic motor nerves in dermis?

Answer 25

innervate the endothelial cells to control vascular tone, smooth muscles of the hair follicle to control the pilomotor response, and eccrine glands to mediate sweating

Question 26

nerves of somatic sensory system provide?

Answer 26

sensations of light touch, discriminative touch, pressure, temperature, pain, itch, vibration and proprioception

Question 27

sensory receptors in skin?

Answer 27

pacinian, meissner’s

Question 28

pacinian corpuscles?

Answer 28

Pacinian corpuscles are present in weight-bearing surfaces, as well as the lips, nipples, penis, and clitoris. They are located in the deep dermis and subcutaneous tissue and detect pressure.

Question 29

meissner’s

Answer 29

located just below the epidermis in the dermal papillae. They are sensitive to light touch and are concentrated on palms and soles.

Question 30

basic collagen structure?

Answer 30

triple helix, composed of 3 α-chains. Each α-chain contains 3 nucleotide repeats where very third amino acid is a glycine (abbreviated Gly-X-Y). Proline and hydroxyproline residues are commonly in the X and Y positions

Question 31

steps of collagen synthesis?

Answer 31

1. Translation of the collagen polypeptide on the rough endoplasmic reticulum 2. Post-translation modification in the endoplasmic reticulum and Golgi complex o Cleavage of signal peptides o Hydroxylation (addition of –OH group) o Glycosylation (addition of glycosyl) 3. Association of α-chains and folding into procollagen triple helix 4. Protease cleavage of N- and C- terminals 5. Assembly and cross-linking with other collagens to form collagen suprastructure

Question 32

marfan syndrome caused by?

Answer 32

Mutations in fibrillin cause an inherited connective tissue disorder called Marfan syndrome.

Question 33

marfan stx?

Answer 33

autosomal dominant condition. Musculoskeletal:Tall and thin body type; Long limbs and fingers; Scoliosis; Flexible joints Eye: Nearsightedness (myopia); Ectopia lentis (dislocation of the lens of the eye) Skin: Striae (stretch marks) Cardiovascular: Aortic dilation or aneurysm; Mitral valve prolapse

Question 34

EDS?

Answer 34

a group of inherited disorders caused by a variety of mutations that interfere with the structure, production, processing, or assembly of collagen

Question 35

EDS clinical features?

Answer 35

highly variable depending on the mutation and subtype. Features may include fragile skin that is very elastic and prone to scarring. Extremely flexible joints may also be a feature, leading to joint dislocations and early arthritis. Severe scoliosis may result in such curvature of the spine that breathing is affected. Collagen within blood vessels and internal organs may also be affected in some subtypes, resulting in rupture of blood vessels, intestines, and the uterus.

Question 36

morphea

Answer 36

acquired autoimmune disease characterized by sclerosis, or thickening of collagen.

Question 37

morphea stx

Answer 37

children and adults may be affected, and it is more common in females. Morphea appears as erythematous and indurated plaques that slowly expand. Even with treatment, morphea can leave behind fibrotic or atrophic scars. Morphea can cause some joint and neurologic complications, but in general, does not cause the degree of internal organ involvement as systemic sclerosis.

Question 38

systemic sclerosis?

Answer 38

acquired autoimmune disease also characterized by sclerosis. most common in young to middle-aged women

Question 39

2 forms of systemic sclerosis?

Answer 39

imited systemic sclerosis (formerly called CREST syndrome) and diffuse systemic sclerosis

Question 40

features of limited systemic sclerosis?

Answer 40

calcinosis cutis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly (thickening and tightening of the skin of the fingers), and telangiectasia of the face

Question 41

features of diffuse systemic sclerosis?

Answer 41

widespread sclerosis of the skin, along with pulmonary fibrosis, renal failure, gastrointestinal disease, and cardiac disease

Question 42

wound healing stages?

Answer 42

Hemostasis Inflammation Proliferation Maturation

Question 43

factors contributing to vasoconstriction?

Answer 43

endothelium of damaged vessels produces vasoconstrictor endothelin. also circulating catecholamines (epinephrine, norepinephrine) and prostaglandins from injured cells.

Question 44

other contributors to vasoconstriction?

Answer 44

Coagulation and platelet activation. thru bradykinin, serotonin, and thromboxane A2.

Question 45

when does vasoconstriction happen?

Answer 45

result of damage signals. Reflexive vasoconstriction occurs before activation of platelets and coagulation

Question 46

physical signs of inflammation?

Answer 46

Physical signs of inflammation are erythema, heat, edema and pain

Question 47

what does inflammation represent on a cellular level?

Answer 47

inflammation represents vessel dilatation, increased vascular permeability, and leukocyte (neutrophils, macrophages) recruitment to the site of injury

Question 48

vasodilation mediators?

Answer 48

mediated by kinins, histamine, prostaglandins and leukotrienes

Question 49

Increased permeability leads to?

Answer 49

transport of intravascular fluid, proteins and cells into the extravascular space resulting in wound edema

Question 50

Leukocyte-endothelial cell contacts are initiated by?

Answer 50

selectin-dependent tethering and rolling, followed by chemokine-mediated activation, integrin-dependent adhesion and extravasation into the underlying tissue.

Question 51

Fibroblasts, smooth muscle cells, and endothelial cells infiltrate wound and reestablish tissue continuity how?

Answer 51

through matrix deposition, angiogenesis and epithelialization within 4-12 days post injury

Question 52

how do fibroblasts enter a wound?

Answer 52

the last cell population to enter a wound; they are attracted by platelet derived products (PDGF, IGF-1, TGF- β)

Question 53

what do they do in the wound?

Answer 53

proliferate, and synthesize collagen and matrix metalloproteinases.

Question 54

what does epithelialization do?

Answer 54

reestablishes the external barrier that minimizes fluid loss and bacterial invasion

Question 55

process of epithelialization?

Answer 55

1. starts with epidermal thickening along the wound edges. 2. Attachments between hemidesmosomes and the basement membrane are broken down, allowing cells to migrate. –The movement of basal cells parallels the direction of collagen orientation (contact guidance). 3. Contact inhibition signals the cells to stop migration. 4. Subsequent cellular proliferation leads to a multilayer epidermis.

Question 56

what is the last event?

Answer 56

collagen maturation.

Question 57

scarring?

Answer 57

collagen matrix undergoes reabsorption and deposition to remodel and strengthen the wound. can’t always return to normal.

Question 58

main fxn of subcutis?

Answer 58

derived from mesoderm. storage of energy in the form of fats. In addition, this layer provides insulation for the body and shock absorption

Question 59

main cells of subcutaneous fat?

Answer 59

adipocytes (also called lipocytes or adipose cells). These cells synthesize and store lipids within their cytoplasm

Question 60

adipocyte histology

Answer 60

aggregate in lobules, and fibrous bands called septae or trabeculae separate the lobules. Within the septae are blood vessels and nerves.

Question 61

Inflammation of the subcutaneous fat called?

Answer 61

panniculitis. many types, most common being erythema nodosum

Question 62

Erythema nodosum (EN) ?

Answer 62

acquired disorder that is most common in young women, though it can affect people of any age, sex, or race. EN is a reactive process that can be triggered by a variety of factors.

Question 63

causes of EN?

Answer 63

idiopathic, OR if known, infectious causes are most common, especially upper respiratory streptococcal infection. Medications (most commonly oral contraceptives), sarcoidosis, inflammatory bowel disease, and malignancy are other triggers.

Question 64

classic EN presentation?

Answer 64

tender, red nodules that arise on the shins. They may arise in crops, then slowly involute over the course of a few days or weeks