Contents
- Brief introduction about Skin
- Layers, glands and appendages of skin
- Regulation of body temperature
- Hypothalamus
- Heat loss center
- Heat gain center
- Applied aspects
- Hyperthermia
- Hypothermia
Skin
- Is the soft outer covering of the body
- It insulates body against changes in environment
- Is made of multiple layers
- Is the largest organ of the body - surface area 1.2 to 2.2 sqm
- Weights 4-5 kg
- Thickness 1 to 5 mm
Layers of Skin
- Epidermis
- Is made up of stratified squamous epithelium
- It doesn't contain blood vessels
- Four Layers
- Stratum corneum
- Stratum granulosum
- Stratum spinosum
- Stratum germinativum
- Dermis
- Two Layers
- Superficial papillary layer
- Deep reticular layer
Glands of the Skin
- Sweat glands
- Apocrine glands
- Present in axilla, pubic region, areola – become active only after puberty
- Eccrine glands
- Present all over the body
- They secrete clear watery fluid – sweat
- Sebaceous glands
- Present in epidermis
- They develop from hair follicle
- Produce Sebum
- During puberty, due to action of sex hormones cause acne
Appendages of the Skin
- Hairs and hair follicles
- Nails
- Sweat glands
- Sebaceous glands
Functions of Hairs and Hair follicles:
- They help in perception of sensations
- They help in thermoregulation
- They protect the scalp against injury
- They act as filter in the nose to prevent the entry of particulate matter
Functions of the Skin
1) Protective function
- Protection from
- Bacteria and toxic substances
- Mechanical blow
- Ultraviolet rays
2) Sensory function
- Receptors are stimulated by sensations of touch, pain, pressure or temperature sensation
3) Storage function
- Stores fat, water, chloride, sugar and blood
4) Synthesis function
- Vitamin D3
5) Regulation of body temperature
- Excess heat is lost from the body through skin by radiation, conduction, convection and evaporation
- Sweat glands help in heat loss by secreting sweat
- Lipid content of sebum prevents loss of heat from the body in cold
6) Regulation of water and electrolyte balance
- Regulates water and electrolyte balance by excreting water and salts through sweat
7) Excretory function
- Excretes small quantities of waste materials like urea, salts and fatty substance
8) Absorptive function
- Absorbs fat-soluble substances and some ointments
9) Secretory function
- Skin secretes sweat through sweat glands and sebum through sebaceous glands
Measurement of Body Temperature
- Body temperature can be measured by placing the clinical thermometer in different parts of the body such as:
- Mouth (oral temperature)
- Axilla (axillary temperature)
- Rectum (rectal temperature)
- Over the skin (surface temperature)
- Normal body temperature in human is 37°C (98.6°F)
- Range - 35.8°C to 37.3°C (96.4°F to 99.1°F).
- Rectal temperature is 0.50 to 10F above the Oral temperature
Core body temperature
↓
Internal body temperature (constant )
Shell temperature
↓
Skin temperature
(variable )
Variations of body temperature
- Physiological
- Age
- Sex
- Diurnal variation
- After meals – specific dynamic action of food
- Exercise
- Sleep
- Emotion
- Menstrual cycle
- Pathological
- Hyperthermia – Fever
- Hypothermia
Heat balance (Heat gain = Heat loss)
- Heat gain or heat production in the body (Thermogenesis)
- Metabolic Activities
- Muscular Activity
- Role of Hormones - Thyroxine and adrenaline
- Radiation of Heat from the Environment
- Shivering
- Brown Fat Tissue
- Heat loss from the body (Thermolysis)
- Conduction
- Radiation
- Convection
- Evaporation – Insensible perspiration
- Panting
Heat exchange in the skin
Regulation of body temperature
- Regulated by hypothalamus which sets the normal range of body temperature
- Under normal physiological condition temperature maintained at 37°c
Heat loss centre
- Situated in preoptic nucleus of anterior hypothalamus
- Neurons in preoptic nucleus are heat sensitive nerve cells, called as thermoreceptors
- Stimulation of preoptic nucleus results in cutaneous vasodilatation and sweating
- Removal or lesion of this nucleus increases the body temperature
Heat gain centre / Heat production centre
- Situated in posterior hypothalamic nucleus
- Stimulation of posterior hypothalamic nucleus causes shivering
- Removal or lesion of this nucleus leads to fall in body temperature
Mechanism of temperature regulation
Decrease in body temperature
▼
Stimulation of heat gain centre
▼
Increase in heat production and decrease in heat loss
▼
Normal body temperature
Increase in body temperature
▼
Stimulation of heat loss center
▼
Increase in heat loss and decrease in heat production
▼
Normal body temperature
Applied Physiology
- Hyperthermia – Fever / Pyrexia
- Elevation of body temperature above the set point
- Classification of Fever
- Low-grade fever: 38°C to 39°C, (100.4°F to 102.2°F)
- Moderate-grade fever: 39°C to 40°C (102.2°F to 104°F)
- High-grade fever: 40°C to 42°C (104°F to 107.6°F)
- Hyperpyrexia
- Rise in body temperature beyond 42°C (107.6°f)
- Results in damage of body tissues
- Life threatening
Causes of Fever
- Infection
- Hyperthyroidism
- Brain lesions
- Diabetes insipidus
Signs and symptoms depend upon the cause of fever:
- Headache
- Sweating
- Shivering
- Muscle pain
- Dehydration
- Loss of appetite
- General weakness
Hyperpyrexia may result in
- Confusion
- Hallucinations
- Irritability
- Convulsions
Hypothermia
- Decrease in body temperature below 35°C (95°F)
- Impairment of metabolic activities of the body
- < 31°C (87.8°F) it becomes fatal
- Elderly persons are more susceptible
Classification of Hypothermia
- Mild hypothermia: 35°C to 33°C (95°F to 91.4°F)
- Moderate hypothermia: 33°C to 31°C (91.4°F to 87.8°F)
- Severe hypothermia: < 31° C (87.8°F)
Causes of Hypothermia
- Exposure to cold temperatures
- Immersion in cold water
- Drug abuse
- Hypothyroidism
- Hypopituitarism
- Lesion in hypothalamus
- Hemorrhage in certain parts of the brainstem, particularly pons
Signs & Symptoms of Hypothermia
- Mild hypothermia
- Uncontrolled intense shivering
- Movements become less coordinated
- Chillness causes pain and discomfort
- Moderate hypothermia
- Shivering slows down or stops but muscles become stiff
- Mental confusion and apathy (lack of feeling or emotions)
- Respiration becomes shallow, followed by drowsiness
- Pulse becomes weak
- Blood pressure drops
- Severe hypothermia
- Person feels very weak and exhausted with incoordination and physical disability
- Skin becomes chill and its colour changes to bluish gray
- Eyes are dilated
- Loses consciousness gradually
- Breathing slows down, followed by stiffness of arms and legs
- Pulse becomes very weak
- Blood pressure decreases very much, resulting in unconsciousness
- Further drop in body temperature leads to death