HLI Flashcards
What are some functions of the skin (9)?
Physical protection Radiation protection Antimicrobial action Barrier function Thermoregulation Sensory activity Metabolic Nutrition Social
Skin appendages can be divided into two groups. What are these groups (give examples)?
- Glands (sebaceous, sweat, special)
2. Keratinised (hair, horn, hoof, claw, feather)
What are the layers of the epidermis from the top to the bottom?
- Stratum corneum
- Stratum lucidum (only present in some non-haired regions)
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Where are melanocytes situated (what layer)?
They produce the pigment melanin by oxidation of tyrosine using what enzyme?
Stratum basale
Tyrosinase
What are the differences between the two distinct layers of the dermis?
The supfl layer (papillary) is more regular than the deeper reticular layer. It also has epidermal derivatives and conforms to the contour of the stratum basale
Vaccinations and microchips are injected where?
Hypodermis (subcutis)
By which mode do sebaceous glands secrete sebum? Where are they often located? In which species are they poorly developed?
Holocrine mode
Located next to hair follicles and empty their secretions directly into them.
Poorly developed in pigs
What is the difference between apocrine and merocrine sweat glands?
Apocrine are over most of the skin. They’re simple, tubular glands with a duct that opens into hair follicles.
Merocrine sweat glands release sweat via exocytosis and their ducts open directly onto the epidermis. Only located in special areas (dog/cat foot pads, equine frog, nasolabial plate, pig carpal glands).
Sudoriferous glands are least active in which domestic species?
Goats and cats
What are the four main structures of a hair follicle?
- Internal epithelial root sheath
- External epithelial root sheath
- Dermal papilla
- Hair matrix
(A dermal root sheath also encloses the follicle)
What is the arrector pili muscle?
Fascicle of smooth muscle cells attached to dermal sheath
What is different about hair produced in a secondary hair follicle?
It lacks a medulla
A compound hair follicle has several follicles grouped together. Which of the following is true?
a. Each follicle has its own glands and roots
b. Each follicle has its own root but not necessarily its own gland
B (own root but not necessarily own gland)
What is a distinguishing feature of tactile hairs?
They have their own blood filled sinus between the dermal root sheath layers
What are the three fibre types comprising the primary trio in sheep?
Kemp Heterotype hair True wool (lacks a medulla like secondary hair follicle hairs)
What are the layers of the horn-producing epidermis?
Stratum basale
Stratum spinosum
Stratum corneum
Which layers are thickest in the walls of the claw plate?
Str. spinosum and corneum
What is hyperkeratosis? Distinguish between orthokeratotic and parakeratotic hyperkeratosis.
Increase in the thickness of the st. corneum
Orthokeratotic= anuclear Parakeratotic= nuclear
Name three diseases in which you might see hyperkeratosis.
Sarcoptic mange
Zinc deficiency
Vitamin A deficiency
Congenital icthyosis
What is acanthosis? How is this different to acantholysis?
Increased thickness of the st. spinosum
Acantholysis is the disruption of intercellular junctions (desmosomes) between keratinocytes of the epidermis. It typically occurs in immune mediated diseases.
Name 2 situations in which you might see hyperplasia of the skin as a primary lesion.
Callus
Sarcoptic mange
Actinic keratosis
What is the difference between spongiosis and ballooning degeneration?
Spongiosis refers to intercellular oedema of the epidermis
Ballooning degen is deformation of the cells and them becoming spherical
What may cause epidermal spongiosis? How about ballooning degen?
Spongiosis: staphylococcus spp.; malassezia infection
Balloon: poxvirus, herpesvirus, trauma
What is hyperpigmentation?
Increased melanin or increased melanocytes (chronic infl diseases or endocrine dermatoses)
In which diseases of the skin might you see crusting/ulceration?
Sarcoptic mange
Dermatophilosis
Greasy pig disease
Pemphigus foliaceus
What is luminal folliculitis?
Leukocytes from the follicular wall migrate into the lumen (due to stimulus in follicular lumen such as bacteria).
What are some common diseases with folliculitis?
Demodectic mange
Dermatophytosis (ringworm)
Bacterial infections
What diseases may result in dermal atrophy?
Hyperadrenocorticism
Hypothyroidism
Congenital collagen defects
What is congenital icthyosis?
Hereditary disorder
Lamellar hyperkeratosis
What might you expect histologically with actinic keratosis?
Hyperkeratosis Parakeratosis Epidermal hyperplasia Apoptotic sunburn cells Fibrosis of the dermis Degen of dermal collagen
Describe the pathogenesis of primary and secondary photosensitization.
Ingestion of plant with photoreactive substances—> deposit in the skin—> sunburn
Genetic inability to metabolise heme pigments—> build up of photoreactive haematoporphyrin pigments
What is contagious ecthyma?
Localised infection of young sheep and goats caused by parapoxvirus.
Causes vesicles, pustules, crusts and scars
What are the two most important factors in the initiation of dermatophylosis?
Prolonged moisture and mechanical damage
What is greasy pig disease?
Acute fatal dermatitis caused by staphylococcus hyicus.
What is deep pyoderma?
Deep bacterial folliculitis/ furunculosis
Feline leprosy is a granulomatous disease caused by what agent??
Where do nodules typically occur?
Mycobacterium lepraemurium. Nodules typically occur on the head, neck and distal limbs.
What is dermatophytosis?
Ringworm. Fungal infection of skin hair and claws
What is malassezia?
Infection caused by lipophilic yeast (rare in cats; common in dogs)
Opportunistic secondary pathogen
How does hyperadrenocorticism affect the skin?
Bilaterally symmetric alopecia
Atrophy
Telegen
Dystrophic calcification of the dermis
What does eosinophilic granuloma in cats often involve?
Indolent ulcer (on upper lip)
Eosinophilic plaque
Eosinophilic granuloma
What does SLE stand for and what does it involve?
Systemic lupus erythematosus= multi organ disease of dogs (rarely cats and horses also)
Failure of immune system to maintain immunological self-tolerance
What is pemphigus foliaceus?
Autoimmune disease in dogs, cats, horses and goats. Results in acantholysis and vesicles
What wound configuration involves partial thickness damage caused by shear forces? (I.e dermis is still intact)
Abrasion
What is the difference between clean-contaminated and contaminated wounds?
Clean-contaminated: created acutely with no evidence of contamination and can usually be primarily sutured with a low risk of infection/breakdown. May require antibiotics.
Contaminated: foreign material, bacteria or other. Requires debridement or healing before closure
An infected wound has a bacterial burden over…?
10^5
How can wounds be classified?
According to their
▪️configuration (abrasion, puncture, laceration, degloving),
▪️contamination level ( clean, clean-contaminated, contaminated, infected)
▪️chronicity (acute, recent, chronic)
What are the three stages of wound healing and what are the major cell types associated with each stage?
(0: blood clotting)
1: inflammation/ debridement (neutrophils and macrophages and then monocytes after 48hrs)
2: proliferation and repair (fibroblasts, myofibroblasts, endothelial cells and epithelial cells)
3: remodelling/maturation (fibroblasts)
What are some systemic factors that might influence wound healing (6)?
What are some local factors (7)?
Systemic: Poor perfusion Hyperadrenocorticism Hypoproteinaemia Diabetes mellitus Exogenous corticosteroids Immunocompromise
Local: Infection Tension Neoplasia Poor vascularity High motion/ shear stresses Moisture level Fluid accumulation
What are some tension relieving techniques that might be useful in wound management?
Undermining Mattress sutures Subcut suture layers Releasing incisions Reconstruction techniques
What is the difference between a papule, nodule and a pustule?
Papule= small solid elevation in skin less than 1cm diameter Nodule= small solid elevation in skin greater than 1cm diameter Pustule= small circumscribed elevation in skin filled with pus
What is an epidermal collarette?
How about a wheal?
Annular area of scale formed when a pustule ruptures
Wheal is a sharply circumscribed area of oedema
What is hypotrichosis?
What is leukotrichia?
Hair thinning
Loss of pigment in hair (leukoderma is loss of pigment from skin)
What is a comedone?
Dilated hair follicle
Briefly describe the severity scoring system for pruritus.
0: no itch
1: occasional
2: more frequent but stops when asleep or distracted
3: regular, stops when distracted
4: prolonged when awake. Occurs when sleeping/ distracted
5: almost always
What is the plasmalemma?
Cell membrane surrounding each myofibre
What is the most important component of the sarcolemma?
The basal lamina
Where are satellite cells located with regards to skeletal muscle? What is unique about these cells?
Between the basal lamina and the plasmalemma
They are the only muscle cells capable of mitotic division post-natally (each time they divide they contribute 1 myocyte nucleus to the myofibre and 1 daughter cell to the satellite cell pool)
What are the 4 major fibre types in mammalian skeletal muscle?
Type 1: slow twitch, red, oxidative
Type 2A: fast twitch, white, oxidative glycolytic
Type 2B: fast twitch, white, glycolytic
Type 2X: fast twitch, white, different myosin heavy chain
What are sensory muscle spindles and where are they found?
Lymph filled sacs with up to 20 small intrafusal fibres. They are especially numerous in muscles involved in fine precision movements and are anchored in the perimysium in association with a small sensory nerve branch
What are some congenital disorders of muscle? (We learnt about 8 specifically)
▪️Arthrogryposis ▪️Congenital flexures ▪️Myofibrillary hypoplasia ▪️Myotonic syndromes ▪️Spastic syndromes ▪️Periodic paralysis ▪️Myasthenia gravis ▪️Muscular dystrophy
What do most cases of arthrogryposis result from?
Defective innervation of muscles
What causes congenital myasthenia gravis and in which dog breeds is it typically seen?
Decreased density of Ach receptors in post synaptic muscle membranes.
JRT, Springer spaniels, smooth Fox terriers
What are some acquired muscle disorders?
Muscle atrophy
Muscle hypertrophy
Muscle pigmentation
Neoplasia
What are some causes of muscle atrophy?
Disuse
Denervation
Metabolic (cachexia, endocrinopathies)
Is denervation atrophy reversible? What muscle types does it typically involve?
Potentially (provided that the motor end-plate has survived, the nerve sheath has not been disrupted, and the original motor axons regenerate and contact the muscle fibres)
Type 1 and 2
What muscles are most severely affected in atrophy of cachexia?
Non-postural muscles
What are some causes of muscle hypertrophy?
Physiological (eg. Increased workload with training)
Compensatory
Congenital (double muscling)
If the sarcolemma tube is disrupted how does muscle repair occur?
Via budding or by fibrosis
What are some causes of muscle degeneration?
Genetic Circulatory Trauma Nutritional Exertional Toxic Inflammatory/ infectious
Duchenne type muscular dystrophy is what type of condition?
What dog breeds is it mostly seen in?
X-linked recessive
Golden retrievers and Irish terriers
(Affected animals may have defective or deficient dystrophin complex)
What is recurrent exertional rhabdomyolysis?
Autosomal dominant condition affecting 5-15% of TBs
Results in sudden hindlimb weakness, stiff gait, sweating, generalised muscle tremors
What is porcine stress syndrome?
Autosomal recessive condition affecting heavily muscled pigs.
Involves a defect in the ryanodine receptor gene which leads to increased calcium levels within sarcoplasmic and hypercontraction
What are some examples of circulatory muscle pathologies?
Compartment syndrome
Muscle crush syndrome (acute muscle trauma)
Downer syndrome
What are the sites in the body of leukopoiesis?
In the early embryo, the yolk sac
In the foetus, it’s the liver, spleen and bone marrow
In the neonate it’s the liver and bone marrow
In the adult it’s just the bone marrow in health (liver and spleen with disease)
Where does lymphopoiesis occur and how long do most lymphocytes live for?
It occurs in the thymus and bone marrow in the embryo and young animal. Then in secondary lymphoid tissues in the adult
Most live for about 2 weeks
Which leukocytes recirculate?
Monocytes and lymphocytes
What is myelopoiesis?
Production of granulocytes (including neutrophils, basophils and eosinophils) and monocytes
What regulates myelopoiesis?
Stem Cell Factor (SCF) Colony stimulating factor (CSF) Cytokines ▪️neutrophils: IL-6, complement C5a, TNF-alpha ▪️eosinophils: IL-5 ▪️basophils: IL-3 ▪️monocytes: IL-1, 3 and 6
In granulopoiesis, what cells make up the mitotic (proliferation) pool? What cells make up the maturation and storage pool?
Mitotic: myeloblasts, promyelocytes and myelocytes
Maturation and storage: metamyelocytes, bands and segmented
Approximately what percentage of cells comprises the mitotic pool in granulopoiesis? What is the transit time of the cells in this pool?
20%
2-3 days