Skin
Structure of skin
Structure of skin
Melanocytes in the
germinal matrix of a
hair bulb
Synthesize melanin
Functions of skin
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Protective functions
Sense organ
Storage
Vit D synthesis
Regulation of body temperature
Water and electrolyte balance
Excretory function
Absorptive function
Sweat glands
• Eccrine gland
• Apocrine gland
Sebaceous glands
• Sebum : FFA, TG, squalene, sterols, waxes.
• Functions
– Antibacterial
– Prevent dryness
– Prevent heat loss
Body temperature
• Homeothermic
• Poikilothermic
Body Temperature
Site
Temperature
Normal Body Temperature
(NBT)
98.60F(370C)
Range of NBT
970F(360C) to
99.50F(37.50C)
Rectal Temp (Core Temp)
(0.50F to 10F) above the
Oral
• Rectal Temp reflects the internal body Temp (Core
Body Temp)
• Core Body Temp remain almost constant
• Skin Temp (Shell Temp)-----Variable
Temperature Homeostasis
• Keep the body temp within a very narrow range
• Range of NBT
(970F to 990F)
• Temperatures above this:
denature enzymes and block metabolic
pathways
• Temperatures below this:
slow down metabolism and affect the brain.
Body temperature
SKIN
Body temperature
Heat Exchange in the Skin
Heat Exchange in the Skin
Heat Exchange in the Skin
Thermoregulation
• Temperature is regulated by nervous feedback mechanisms
• Thermoregulation maintains the core temperature at a
constant set point despite fluctuations in heat absorption,
production, and loss
• Thermoregulatory center located in the Hypothalamus
• Thermoregulatory regulatory responses include
Autonomic
Somatic
Endocrine
Behavioural changes
Feedback system
• 1) Receptor
– Sensor that responds to changes (stimuli)
• 2) Control Center
– Sets range of values
– Evaluates input and
– Sends output
• 3) Effector– Receives output from control centre
– Produces a response
Receptor
• Thermoreceptors
– Cutaneous thermoreceptors (mainly to
cold)
– Central thermoreceptors
• preoptic and anterior hypothalamic nuclei of the
Control Center
• Hypothalamus
• Posterior hypothalamus (approximately at the
level of the mammillary bodies.)
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Acts as a thermostat
Sets range of values
Evaluates input and
Sends output
Control Center
Temperature-Regulating Mechanisms:
RESPONSE
Fever
• As if the thermostat
had been reset" to a
new point above 37 °C
• Endogenous pyrogens
(EPs):IL-1α, IL-6, β-IFN,
gamma-IFN, and TNFα