Path 1- Integument 1

drraythe's version from 2015-05-02 16:35

Lecture 1

Question Answer
What are the layers of skin, from outside to in?(1) Stratum corneum
(2) Stratum granulosum
(3) Stratum spinosum
(4) Stratum basale
Describe the Stratum corneumComposed of corneocytes (keratinized cells) & forms the protective outer barrier
Describe the Stratum granulosumCells contain keratohyalin granules
Describe the Stratum spinosumPolyhedral-shaped cells w/ desmosomal attachments which are visible histologically as intercellular bridges
Describe the Stratum basaleIt is the germinal layer, single layer of cuboidal cells resting on the basement membrane & these basal cells are interspersed w/ specialized cells: melanocytes, Langerhans cells, merkel cells
What cell is the layers of the epidermis composed of?Keratinocytes
Where do keratinocytes originate from? How/where do they differentiate? What is their fate?Originate from germinal cells in stratum basale, they differentiate more & more as they move upwards towards the surface. They are eventually all shed from the stratum corneum
What is the typical transit time of a single keratinocyte?~1 mo
What 3 things is the basement membrane zone composed of?(1) Hemidesmosomes of the basal cells
(2) Lamina lucida composed of plasma membrane & anchoring filaments
(3) Lamina densa composed Type IV collagen
What do desmosomes do?Desmosomes provide intercellular adhesion between keratinocytes
What do Hemidesmosomes do?Provide attachment of the epidermis to the basement membrane
What is the dermis composed of?Composed of collagen & elastin fibers embedded in glycosaminoglycan ground substance
What is the purpose of the dermis?Provides support for epidermis, adnexa, vessels & nerves
What are the 2 types of nerves supplying the skin? Examples?(1) MOTOR (efferent, autonomic) neurons, for arrector pili mm, endocrine sweat glands & arteriolar sm mm
(2) Sensory (efferent) for free nerve endings (pain), Meissner’s corpuscles (light touch) & Pacinian corpuscles (deeper pressure)
What is/explain the subcutisAka hypodermis, aka panniculus. Attaches the dermis to underlying musculoskeletal system. Made of adipose & collagenous & elastic fibers
What is the "adnexa”?It’s the hair follicles & associated glands in the skin
How does hair grow? ExplainHair grows in CYCLES, there are 4 of them: Anagen - growth period, Catagen - transition period, Telogen - resting period, Exogen - shedding period (ACTE)
What is Anagen? Growth period of hair cycle
What is Catagen?Transition period of hair cycle
What is Telogen?Resting period of hair cycle
What is Exogen?Shedding period of hair cycle (overlaps with the return to Anagen phase)
What are 3 things hair growth is affected by?(1) Photoperiod
(2) Nutrition
(3) Health status
Explain how hairgrowth is affected by photoperiodThe hypothalamus, pituitary & pineal gland secrete the trophic hormones (growth stimulating hormones): melatonin, gonadal, thyroid, adrenal hormones
What are the 2 sweat glands?(1) Apocrine (duct opens into hair follicle “epitrichial glands” undergo apocrine secretion (by membrane budding) )
(2) Eccrine (duct opens directly onto skin surface, “atrichial glands” undergo merocrine secretion (by exocytosis) )
Explain a sebaceous glandDuct opens into deeper area of hair shaft, secretions condition & lubricate the hair shaft, undergo holocrine secretion (by membrane rupture)
What are 2 examples of pathogens which can penetrate skinHookworm larvae, Schistosoma
2 examples of Dermatophytes which colonize the stratum corneum & cornified structures such as hair & clawsMicrosporum canis, Trichophyton mentagrophytes
Example of a pathogen which infects skin via penetrating trauma such as puncture wounds?Clostridium tetani
Pathogens which penetrate through hair follicle openings/pores?Demodex, Staphylococcus
What is furunculosis (boil)? Why does this happen?Ruptured follicle or gland leading to a bacterial infxn
What could cause a bacterial embolism?Erysipelothrix rhusiopathiae
Which pathogen uses migration along nerves from infected ganglia as a portal entry into the skin?Herpesvirus
Which layer is the most important barrier against infxn & fluid loss?Stratum corneum
What do Keratinocytes do?Produce keratin filaments, desmosomes & hemidesmosomes that provide structural integrity
What are the 6 components of the innate immune system?Stratum corneum barrier, Macrophages & Dendritic cells, Phagocytes, Endothelial cells, Coagulation system & Compliment cascade
Explain how the Stratum corneum barrier affects the innate immunity of the skinPrevents pathogen adherence, normal flora prevents pathogen colonization, contains antimicrobial peptides & fatty acids
How do Macrophages & dendritic cells work as a part of the innate immunity of the skin?They have pathogen recognition receptors (PRRs) Initiates toll signaling pathway & Promotes expression of pro-inflammatory mediators (cytokines, chemokines, adhesion molecules)
How do endothelial cells contribute to the innate immunity of the skin?Express adhesion molecules & trigger kinin, coagulation & complement systems which facilitates influx of plasma proteins & migration of leukocytes to sites of injury & infxn
What kind of things does the Complement cascade do for the skin's innate immunity?Recruits inflammatory cells (C5a), causes mast cell degranulation (C3a, C5a), opsonizes pathogens (C3b, C4b) & kills some pathogens (MAC)
What are the 6 components of the adaptive immune system of the skin?Langerhans cells, CD8 T cells (cytotoxic T lymphocytes), CD4 TH1, CD4 TH2, Endothelial cells, Keratinocytes
How do Langerhans cells contribute to the adaptive immune system of the skin?They produce pro-inflammatory cytokines, they present antigen to naive T lymphocytes in lymph nodes & they present antigen to sensitized T lymphocytes at site of infxn/injury
What do CD8 T cells do in the adaptive immunity of the skin?(Cytotoxic lymphocytes) kill virus-infected cells & neoplastic cells
What do CD4 TH1 cells do in the adaptive immunity of the skin?Activate macrophages (IFN-γ) to eliminate intracellular bacteria
What do CD4 TH2 cells do in the adaptive immunity of the skin?Activate B cells, mast cells & eosinophils (IL-4, IL-5, IL-13) to produce immunoglobulins & eliminate extracellular pathogens
How do Endothelial cells play a role in the ADAPTIVE immune system of the skin?Express adhesion molecules & bind activated leukocytes for extravasation & migration to sites of injury & infxn
How do Keratinocytes play a role in the adaptive immune system of the skin?Produce cytokines & growth factors which modulate adaptive immune responses

Lecture 2 (orange is the yellow must-know stuff)

Know all the 1st & 2nd Intention healing crap
Question Answer
What is Acanthosis?Diffuse thickening (hyperplasia) of the stratum spinosum (Acantho = Spiney “having thorn-like projections”)
What is Acantholysis?Discohesion b/t keratinocytes leads to breaking apart of epidermis. It's due to a Loss of desmosomal fxn! Occurs w/ acantholytic dzs such as pemphigus (Acantho = spiney; Lysis = breaking apart)
What is Spongiosis?Intercellular edema leads to sponge-like appearance of epidermis
What is Ballooning degeneration?Intracellular edema leads to cytoplasmic swelling in the superficial layers of the the epidermis.... Occurs w/ injury & infxn (esp. viral)
What is Hydropic degeneration?Intracellular edema leads to cytoplasmic swelling. This term is used for basal layer only. Occurs w/ interface dz such as cutaneous lupus
Regeneration/repair → blood clotting. when does this start? explain what's going on0-12hrs post injury. Blood clot fills the space created by a wound (scab) (the scab provides a temporary protective barrier & provides a matrix for cell migration)
Regeneration/repair → inflammation. when does this start? What cells are involved?12-24 hrs post injury. Recruitment of inflammatory cells: phagocytes ((neutrophils & macrophages) →engulf pathogens & foreign debris) & Macrophages also secrete collagenases (facilitating tissue debridement & remodeling)
Regeneration/repair → Re-epithelialization. When does this start? Which cells do what?3-7 days post injury! Keratinocytes migrate & proliferate to cover the wound. Keratinocytes produce proteases in order to dissect between viable & nonviable tissue. All this Re-establishes basement membrane zone
Regeneration/repair → Fibroplasia. when does this start? What cells/things are helping etc.?3-7 days post injury. Cytokines & growth factors are released & then FIBROBLASTS begin to perform several tasks:
(1) Migrate & proliferate to repair wound
(2) Produce proteolytic enzymes to facilitate migration
(3) Produce extracellular matrix proteins to form connective tissue
Regeneration/repair → Angiogenesis. When does this start? What is going on?3-7 days post injury. Injured cells at the wound site release angiogenic factors & Endothelial Progenitor Cells (EPCs) migrate to site of injury & proliferate. Endothelial cells form new vessels to re-establish blood flow
Regeneration/repair → Wound contraction. When does this start? What is going on?7 days post injury. Fibroblasts produce collagen & contractile microfilaments that link to the dermal matrix. Collagen bundles bind at the wound margins to contract the wound. Inflammation, edema & vascularity gradually disappear
Regeneration/repair → Tissue remodeling. When does this start? what is going on?Weeks to months post injury. Collagenases & proteases facilitate tissue remodeling to reduce the amount of scar tissue over time.
What is the hallmark histological feature of healing?Granulation tissue
What is granulation tissue made of?Composed of fibroplasia & angiogenesis.
Describe the histological appearance of granulation tissueThe histologic appearance of granulation tissue has a latticework array of proliferative capillaries (angiogenesis) oriented perpendicular to proliferative fibroblasts (fibroplasia)
What is "proud flesh"?Exuberant granulation tissue (happens in horses most often)
What is Cornification?Transformation of squamous epithelial cells into the keratin layers of the stratum corneum, hair, nails
What are the 1° (GENETIC) cornification disorders?1° seborrhea of the cocker spaniel (genetic). Ichthyosis (genetic)
What are the 2° (ACQUIRED) cornification disorders usually caused by?Occurs as a response to chronic stimuli such as inflammation & trauma OR Nutritional disorders (vitamin A deficiency)
What is Hyperkeratosis? What might his result in?Increased thickness of stratum corneum causing flaky skin. Disruption of the stratum corneum can predispose to infxns (bacteria, yeast)
Epidermal hyperplasia is aka? What is the definition & what is it usually a result of?Acanthosis = epidermal hyperplasia = diffuse thickening of the epidermis w/ increased number of keratinocytes. It is a common response to chronic stimuli (inflammation, trauma)
What is Dyskeratosis? What are some causes of this?It is premature keratinization of epidermal cells. Happens in zinc-responsive dermatosis, actinic keratosis (solar damage) & also occurs w/ squamous cell carcinoma
Alterations in Epidermal/ Growth & Differentiation → Apoptosis. When does this usually occur? examples?Usually occurs w/ auto-immune disorders such as lupus erythematosus (basal keratinocytes affected) & erythema multiforme (multiple layers affected)
What is an Fissure? Erosion? Ulceration?Fissure = deep cleft. Erosion = necrosis of superficial epidermis. Ulceration = necrosis of full epidermis & partial dermis
What is dysplasia (broad def.) examples of when this would occur?Dysplasia = abnormal development Can occur w/ chronic ulceration & inflammation. It also may proceed malignant transformation such as non-invasive carcinoma (carcinoma in situ)
What is carcinoma in situ?A non-invasive carcinoma (pre malignancy)
What is atrophy of keratinocytes? Why/how does this happen? (examples)("Thin skin") decrease in the number & size of keratinocytes. This occurs as a consequence of sublethal cellular injury-- such as: hormone imbalances (e.g. hyperadrenocorticism), partial ischemia & severe malnutrition
What is edema?Fluid accumulation BETWEEN cells
What is spongiosis? When does spongiosis usually happen?Intercellular edema of the epidermis. Spongiosis is common w/ epidermal inflammation (epidermitis) caused by Staphylococcus or Malassezia
What are the 2 types of intracellular fluid accumulation?Hydropic degeneration & ballooning degeneration
What is hydropic degeneration? When does it usually occur?(Intracellular fluid accumulation) It is keratinocyte swelling limited to the basal keratinocyte layer; occurs w/: lupus erythematosus, dermatomyositis, drug eruptions
What is ballooning degeneration? What can cause this to occur?(Intracellular fluid accumulation) It is keratinocyte swelling w/in more superficial layers & is caused by epidermal damage & numerous viruses such as poxviruses & FMD virus
What is Acantholysis? What does it result in?Disruption of intercellular junctions (desmosomes) between keratinocytes of the epidermis. Results in dissociation of keratinocytes & the formation of epidermal vesicles & pustules
What is acanthosis caused by?Caused by immune-mediated injury (Type II cytotoxic hypersensitivity) → pemphigus (& some skin infxns)