Term
What signalling molecule is important in mediating the transition from telogen to anagen? |
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Definition
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Term
What are the cell layers of the hair follicle?
Outer to inner... |
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Definition
Outer root sheath
Inner root sheath (Henley's later: Huxley's layer: Cuticle)
Hair shaft cuticle
Cortex
Medulla |
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Term
| What is the basic anatomy of a sebaceous gland? |
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Definition
Holocrine glands that are uni- or multi-lobular and associated with every hair follicle. Acini are connected to a common excretory duct. This duct usually exits into a pilary canal in the infundibulum of a hair follicle.
Sebaceous glands have stratified squamous epithelium. The squamous epithelium that lines sebaceous duct is continuous with the ORS of its associated hair follicle.
The basement membrane is formed by a single layer of basal cells called reserve cells. |
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Term
| How are the glandular secretions excreted from a sebaceous gland? |
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Definition
| As cells progress towards the lumen they differentiate, begin to produce lipid and accumulate lipid droplets. Fully differentiated see the sights are distended with leopard. Eventually the entire sebocyte disintegrates to release lipid into the duct to form sebum. |
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Term
| What is the unit of a hair follicle and a sebaceous gland together called? |
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Definition
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Term
| Where a sebaceous glands normally most numerous? |
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Definition
| Mucocutaneous junctions, interdigital spaces, the dorsal neck and rump, the chin (submental unit), the dosal tail (supracaudal/tail gland, uropygial/preen gland) |
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Term
| Where are sebaceous glands not naturally found? |
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Definition
| Foot pads and the nasal planum. |
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Term
| What two transcription factors may be involved in the embryogenesis of sebocytes? |
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Definition
Shh (sonic hedgehog) appears to be increased
Wnt appears to be decreased |
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Term
| What are the major components of sebum in animals? |
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Definition
Triglycerides and wax esters. Unlike in humans, there is very little squalene present.
Fatty, linoleic, myristic, oleic and palmitic acids are also present in small amounts. In the hair follicle, sebum becomes contaminated with lipase producing bacteria (propionibacterium spp. and staph spp.) which results in production a free fatty acids (those above) that are both anti-microbial and antibacterial.
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Term
| Where are sebaceous glands most numerous in the horse? |
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Definition
| You cook cutaneous junctions, the upper eyelids, the mane, the submandibular region, the udder and near the coronet |
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Term
| What are some of the major functions of sebum? |
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Definition
Keeps the skin soft and pliable, forms a surface emulsion over the SC which helps to retain moisture, conditions hair, provides anti-microbial and anti-fungal activity (contains IgA), may have pheromone properties, may provide a mechanism by which vitamin E can get to the upper layers of the skin. |
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Term
| How does androgen and estrogen affect sebaceous glands? |
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Definition
Androgens cause hypertrophy and hyperplasia.
Estrogens cause involution.
Glucocorticoids cause involution. |
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Term
| What is the general structure and distribution of epitrichial (apocrine) sweat glands in small animals? |
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Definition
These glands are generally coiled and saccular or tubular. They are distributed throughout all haired skin and not present in foot pads or nasal planum. They are generally located below the sebaceous glands.
They are largest and most numerous near mucocutaneous junctions, in interdigital spaces and over the dorsal neck and rump. |
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Term
| What are some of the potential functions of epitrichial a (apocrine) sweat glands? |
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Definition
| May have pheromonal functions and likely has anti-microbial properties as there is IgE content as well as alkaline phosphatase and acid phosphatase. |
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Term
| What makes apocrine sweat glands in horses different than small animals? |
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Definition
Apocrine sweat glands in horses are similar to small animals in structure but they are innervated (express β2-adrenergic receptors).
sweat secretion can be initiated under a number of circumstances but the central drive is in response to a thermal stimulus. In horses sweating is an essential and primary mechanism for heat dissipation during exercise or exposure to hot ambient conditions. |
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Term
| Where are atrichial (eccrine) sweat gland found and what is their basic structure? |
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Definition
Eccrine Sweat glands are found only in the foot pads of carnivores.
Merocrine glands, small and tightly coiled and located in the deep dermis and subcutis.
The excretory duct opens directly to the foot pad surface.
Richly supplied with cholinesterase positive nerves. |
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Term
| Which large animal species has the largest sebaceous glands? The smallest? |
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Definition
| Horses has the largest sebaceous glands and pigs have the smallest. |
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