Integument Flashcards
What are skin associated glands?
- Sebaceous glands
2. Sweat glands: encrine and apocrins
What are sebaceous glands?
- oil glands
- nothing to do with thermoregulation
- Alwasy empty itnto hair follicle
- secrete sebum: lipds
What is the function of sebum
- escapes when pilorector muscles alongside hairs contract
- oils hair
- forms oily film on the skin: lubricates skin, stops water loss, inhibits growth of certain bacteria, spread sweat, territorial marker
How are sebaceous glands regulated?
- regulated by sex steroid hormones
- more active after puberty
- larger adn more productive in the breeding season
- androgens (male) increases activity
What are sebaceous glands?
- oil glands
- nothing to do with thermoregulation
- Alwasy empty into hair follicle
- secrete sebum: lipds
Few facts about sebaceous glands comparing with species
- no sebaceous glands with feathers
What are important about sweat glands?
- involved in thermoregulation
Apocrine sweat glands
- common in domestic species, sparce in primates
- important in evaporative heat loss in some animals (horses and cattle)
- autonomically regulated by sympathetic nervous system: noradrenaline
- oily, opaque secretion, initially odourless but becomes smelly with bacterial breakdown
Ecrine sweatglands
- Common in primates, sparce in domestic animals
- important evaoprative heat loss
- Ach releases, sympathetic
- watery NaCl solution that can be modified by aldosterone
What do both apocrine and ecrine sweat glands need and what for?
- Myoepithelial cells
2. single cells needed to get secretion out
Name some glands in our domestic species
- anal glands in dogs and cats (territorial marking)
- Interdigital pouch at front of claw in sheep
- infraorbital pouch in sheep (eye) = territorial marking
- tail glands in dog adn cat (territorial marking)
- preputial gland at opening of foreskin in boars - sexual attraction, scent
What produced melanin?
Where are they locates and structure
- Melanocytes
- These cell bodies interspersed with other cells in basal layer epidermis
- Cell extensions are squeezed between cells
- Melanin is shed when keratinocytes reach the surface of the skin
What is melanin and what are the types?
- melanin is a broad term for a group of natural pigments
- there are 2 pigments
a) Eumelanins (black and brown colouration)
b) Pheomelanins (yellow and red colouration)
How is melanin synthesised?
- Controlled by MSH binding to its specific MSH receptor
2. more MSH = more pigment produced
What regulated how much of the MSH hormone is produced
- UV light
2. Disease states e.g. crushings
Outline how vitamin D is formed in the skin. what is it inhibited by?
- DHC in ther dermin + UV –> vit D3
2. inhibited by heavy pigmentation, dense fur coat
What is vit D important for and where found?
- important in calcium homeostasis
2. found in fat, liver, blood, synthesised in skin
What is photosensitivty?
- abnormal reaction to sunlight due to accumulation of photosensitive compounds below the skin. due to the presence of a photodynamic agent.
- NOT SUNBURN!
With endotherms what is included in core temperature?
What is important to remember with core
CORE = brain, thorax and abdomen
2. Core should stay the same, skin temp and extremities etc changes
When would you expect to see a normal change in core temperature
DROPS
1. before partuition
2. Sleep, therefore first thing in morning
INC
3. metabollic rate inc - growing, lactating or pregnant
How does core body temp fluctuate?
- between 0.5- 1 degree over 24 hrs
Core body temp of species
- Cattle = 38.5
- Dogs = 38.5
- Cats = 38.5
- Horse = 37.5
- Pig = 39
- Sheep = 39.5
Thermoregulation overview
- Temperature receptors detect changes in temp
- Hypothalamus receives info about both internal and external temp
- Motor output = Signals for heat or cold stress
Where are the cold and warm receptors located?
- cold = mediated by cold receptors in epidermis
2. warm = mediated by warm receptors in dermis
Why can skin temp change greatly?
What nervous system?
How does it affect blood flow?
- Blood flow to the skin can vary widely depending on the need to dissipate heat
- ONLY sympathetic nervous system regulates blood to skin and controls the erector pili muscle
- Reduced frequency of nerve impulses = vasoconstriction. Increased frequency of nerve impulses = vasoconstriction
How are blood vessels arranged in skin?
- parallel arterioles and veins in dermis and subcutaneous adipose tissue
Panting
Why does a dog not develop alkalosis?
- rapid, shallow breathing
- Most water coming from nasal turbinantes and not mouth
- not develop alkalosis as (breathing deep and heavily would) as not changing alveolar gas exchange
What is thermogenesis and how do domestic species increase it?
Thermogenesis is the production of heat in the animal body
- shivering: Primary involuntary measn of increasing heat production. Antagonistic muscles contract simultaneously
- Non shivering thermogenesis = inc basal metabollic rate
At rest where does most heat come from?
- rest = heart, liver, kidney and brain produce 60-70% body heat
Non shivering thermogenesis
- partly driven by the amount of thyroid hormone produced which will inc general metabollic heat
- also due to action of sympathetic nervous system which controls blood supply and oxidation of fatty acids in brown adipose tissue
What is the thermoneutral zone?
- range at whihc don’t need to expend energy to maintain core temperature
What do pyrogens do?
- change the hypothalamic set point to a higher value than normal
- This means that animal will feel cold = generates heat
- because core body temp is 37 but if set point inc to 39 you will feel cold!
- therefore when have flu you feel cold
Recumbent cow with hypocalcawmia. Would you expect core temperature to be higher or lower than normal? Explain
- Lower
- Inactive
- Low calcium = less smooth muscle working
Why are sedated animals more at risk of hypothermia?
- inc SA
- not moving
3 Losing heat through incision/ prep (surgical spray)
How does an adult animals LCT and TNZ compare to that of a neonate?
- Lower LCT and Wider TNZ as bigger and less likely to lose heat
- If had to draw a somatic reflex arc what would you include?
- Sensory receptor
- Sensory neurone into dorsal end
- interneuron
- Motor out of ventral and
- Directly to effector
How does a smatic reflex arc differ from autonomic reflex arc?
- somatic = one neuron to effector
2. autonomic = motor effector has 2 neurons pre and post ganglionic
What are the skin funcitons?
- Thermoregulation
- Sensory info
- Synthesis of vit D
- Storage of fat and water
- Protection: mechanical and chemical injury, invasion by microorganisms, underlying tissue from the sun, from dehydration
