Integument Flashcards
What is the name of the growth phase of hair?
Anagen
What is the name of the shedding phase of hair?
Telogen
What happens if the anagen phase of hair growth is shorter than the telogen phase?
Hair will be shedded faster than it grows, leading to hair loss
How does hypothyroidism affect hair growth?
Causes anagen phase to be shorter and telogen to be longer - hair loss/bilateral alopecia
Where does the synthesis of keratin filaments occur?
Stratum basale
How does hard keratin differ to soft keratin?
Soft - elastic (e.g. skin)
Hard - contains more sulphur, less elastic, more permanent (e.g. nails, horns)
What is the function of sebaceous glands?
- oil glands
- produce sebum
- empty into a hair follicle
- not associated with thermoregulation
What are the two main components of sebum?
- Dead epithelial cells
- Lipids
What are some of the functions of sebum?
- helps prevents water loss
- lubricates skin
- inhibits bacteria growth
- help spread sweat
- oils hairs
What regulates sebaceous glands?
Sex steroid hormones
Which sweat glands are involved in thermoregulation in the skin?
Apocrine
Ecrine
What cells do both apocrine and ecrine glands contain?
Myoepithelial cells
Which species rely most on sweat glands for thermoregulation?
- Horses and donkeys
- Cattle
- Humans
What are some other specialised skin glands found throughout different species?
- anal sacs of cats and dogs
- interdigital pouch of the sheep
- infraorbital pouch
- tail gland
Why is the production of melanin important?
- Camouflage
- Mimicry
- Social communication
- Protects against solar radiation
How is melanin secreted from melanocytes?
- Melanin is synthesised and packed into vesicles
- Vesicles are transferred into keratinocytes
- when keratinocytes reach the surface of the skin melanin is shed
Which hormone controls melanin synthesis?
MSH = melanocyte-stimulating hormone
What is the production of MSH stimulated by?
- UV light
- Disease states
- Other external signals e.g. camouflage
Vitamin D is important in the homeostasis of what?
Calcium
What is photosensitivity?
- abnormal reaction to sunlight due to accumulation of photosensitive compounds below the skin
What does an animals temperature depend on?
The balance between heat input and heat output
Which 3 anatomical structures make up the ‘core’?
Brain, thorax and abdomen
Where is temperature change detected?
Hypothalamus receives information from internal and external thermoreceptors
Where are warm and cold receptors located?
Warm = dermis Cold = epidermis
What can be stimulated at very cold or hot temperatures?
Nociceptors = pain receptors
What are some motor output adaptations to cold stress?
- behaviour
- reduced skin blood blow
- shivering
- activation of brown fat
- hormone secretion
Which nervous system regulates blood flow to the skin?
Sympathetic
Which change in nerve impulse frequency causes vasodilation?
Decreased frequency
How is panting different to respiration?
- rapid and shallow
- no respiratory gas exchange
- little energy expended
How does shivering increase heat production?
- Skeletal muscle produces heat when it contracts
What is a brown fat cell?
A skeletal muscle cell with no actin or myosin
What causes non shivering thermogenesis?
Increased activity of the sympathetic nervous system
What are pyrogens/their role?
Some systemic illnesses increase the hypothalamic set point to higher than normal value
List the mechanisms a pig will use to regulate its temperature on a hot day
- Drink more, eat less
- Wallow
- Open posture
- Seek shade
- Move less
- Vasodilation – they do not sweat
Why are surgical patients at risk of hypothermia?
- not moving
- increased SA
- losing heat through incision/prep
How does an adult animals LCT and TNZ compare to that of an neonate?
Lower LCT and wider TNZ
