Lecture 20 - Skin

Question 1

Skin is a barrier… what barriers does it include?

Answer 1

Chemical barriers- skin secretions low in pH, or inhibit bacterial growth, and melanin that protects skin from UV damage

Physical or mechanical barriers- provided by continuity of the skin and hardness of the keratinized cells.

Biological barriers- the dendritic cells and macrophages of dermis.

Question 2

Why is skin important for temp. regulation and sensation?

Answer 2

manufactures sweat to cool body and causes constriction of dermal capillaries to prevent heat loss.

Cutaneous sensation happens through cutaneous sensory receptors (part of the nervous system) in the layers of the skin

Question 3

Skin and metabolism

Answer 3

The skin provides metabolic function of making a vitamin D precursor, cholecalciferol, when exposed to sunlight. Cholecalciferol is activated into vitamin D (calciferol) in the liver and kidneys, goes to the intestines and stimulates the absorption of calcium ions.

skin may act as blood reservoir by holding up to 5% of the body’s blood supply, may be diverted to other areas of body if needed.

Question 4

Core temp. vs. shell

Answer 4

core includes organs within the skull, thoracic, and abdominal cavities, have the highest body temperature

the shell (mostly the skin) has the lowest temperature.

Core temperature is closely regulated: blood is an agent of exchange between core and shell, allowing heat to be lost through increased flow to skin, or retained by bypassing vessels in the skin.

Question 5

Mechanisms of heat exchange

Answer 5

Heat exchange between our skin and external environment occurs through

radiant flow of heat

conductive flow of warmth from warmer to cooler objects

convective movement of warm air away from the body

And heat loss due to evaporation of fluids from the lungs, oral mucosa, and the skin.

Question 6

Insensible heat loss

Answer 6

accompanies insensible water loss from lungs, oral mucosa, and skin and accounts for about 10% of basal heat production.

SO SETTLE YOU CAN NOT SENSE IT

Question 7

Sensible heat loss

Answer 7

occurs when the body temperature rises and sweating increases water vaporization.

HEAT LOSS YOU CAN FEEL

Question 8

Heat promoting mechanisms

Answer 8

maintain or increase body core temperature and include constriction of cutaneous blood vessels, shivering, increase in metabolic rate, and increased release of thyroxine (only in infants).

Question 9

Heat loss mechanisms

Answer 9

protect the body from excessively high temperatures and include dilation of cutaneous blood vessels, sweating and behaviors that promote heat loss or reduce heat gain.

Question 10

Hypothalamus

Answer 10

Regulates body temp.

Question 11

Frostbite

Answer 11

occurs when blood flow to skin is restricted due to extreme cold, causing skin cells to be deprived of oxygen and nutrients. Skin cells begin to die, leading to tissue damage.

Question 12

Hypothermia

Answer 12

is a low core body temperature from cold exposure, leading to a decrease in vital signs. Shivering stops at core temperature of 30– 32°C.

Question 13

Hyperthermia

Answer 13

is an elevated body temperature that overwhelms the body’s ability to cool down.

Question 14

Heat exhaustion

Answer 14

heat-associated collapse after vigorous exercise due to dehydration and low blood pressure. The heat-loss mechanisms are still functional but it can progress to heat stroke.

Question 15

Heat stroke

Answer 15

positive-feedback loop begins at 41°C core temperature. Elevated temperatures increase metabolic rates, which further increase body temperatures and can be fatal.

Question 16

Fever

Answer 16

Fever is a controlled increase in body temperature that results when macrophages and other cells release cytokines that act as pyrogens, causing the hypothalamus to reset to a higher than normal temperature.

Once the disease has passed, cryogens (example: vasopressin) reset the thermostat to lower (normal) level, activating heat-loss mechanisms, so temperature falls.

Question 17

Cancer

Answer 17

occurs when the DNA of a cell is damaged or mutated and the cell begins to grow uncontrollably. The cell divides through mitosis, spreading exponentially through the body.

Question 18

Carcinoma

Answer 18

cancer that develops from epithelial tissue.

Adenocarcinoma is a cancer specifically from glandular epithelium.

Question 19

Sarcoma

Answer 19

cancer of connective tissues other than blood.

Leukemia and lymphoma are
cancers from blood-forming cells.

Question 20

Benign tumour

Answer 20

mass of cells that is not classified as cancerous or malignant, they lack ability to invade neighbouring tissues or metastasize (spread throughout the body).

Most skin tumours are benign but some can become malignant, called tumour progression.

Risk factors include overexposure to UV radiation and frequent irritation of the skin.

Question 21

Basal cell carcinoma

Answer 21

Least malignant and the most common skin cancer.

Stratum basale cells proliferate and slowly invade dermis and hypodermis.

It is cured by surgical excision in 99% of cases.

Question 22

Squamous cell carcinoma

Answer 22

Squamous cell carcinoma are second-most common type of skin cancer and can metastasize.

derive from the keratinocytes of the stratum spinosum.

usually present as a scaly reddened papule on scalp, ears, lower lip, or hands.

tends to grow rapidly and metastasize if not removed. Good prognosis if treated by radiation therapy or removed surgically.

Question 23

Melanoma

Answer 23

cancer of melanocytes

It is the most dangerous type of skin cancer, highly metastatic and resistant to chemotherapy.

Treated by wide surgical excision accompanied by immunotherapy.

Question 24

Signs of melanoma

Answer 24

Asymmetry: the two sides of the pigmented area do not match.

Border irregularity: the edges are not smooth.

Colour: contains several colours (black, brown, tan,
sometimes red or blue)

Diameter: larger than 6 mm (size of pencil eraser).

Evolution: does it grow and change over time?

Question 25

Burns

Answer 25

Tissue damage resulting from intense heat, electricity, radiation, or certain chemicals, all of which denature cell proteins and cause cell death.

Risks to burn patient include dehydration and electrolyte imbalance due to fluid loss, as well as infection of burned areas.

Question 26

Calculating burns

Answer 26

To evaluate burns, the Rule of nines is used.

The body is broken into 11 sections, with each section representing 9% of body surface (except genitals, which account for 1%).

This is used to estimate volume of fluid loss.

Question 27

First degree burn

Answer 27

involve epidermal damage only. There is localized redness, edema (swelling), and pain.

Partial-thickness burn

Question 28

Second degree burn

Answer 28

involve damage to the epidermis and upper dermis. Blisters will appear.

Partial-thickness burn

Question 29

Third degree burn

Answer 29

involve the entire thickness of the skin and can be referred to as full-thickness burns. Skin colour turns gray-white, cherry red, or blackened.

The burn itself is typically not painful because the nerve endings are destroyed but the area around the burn can be intensely painful.

Question 30

Critical burns

Answer 30

25% of body has second-degree burns.

> 10% of body has third-degree burns.

Face, hands, or feet have third-degree burns.