Biology (ICSE IX) - Skin: The Jack of All Trades

Define skin.

Define skin.

largest organ of the body; almost impermeable barrier

What is another name for the skin?

integument

List the seven functions of the skin.

protection, sensory perception, temperature regulation, food storage, excretion, synthesis of vitamin D, grip

The skin proper is composed of the outer layer, the __________, and the inner layer, the __________.

epidermis; dermis

Define epidermis. What type of tissue is it comprised of? Name its three sublayers in sequence descending with depth.

outer thinner layer of skin; stratified epithelium; cornified, granular, malphigian

What constitutes the cornified layer? What three dangers does it offer resistance to?

flattened dead cells made of keratin which are continually shed and replaced; resistant to mechanical damage, bacterial infection, water loss by evaporation

What is the main function of the granular layer?

it contains flattened cells which gradually replace the cornified layer

What is the main function of the malpighian layer?

cells divide and reproduce, pushing outward to replace the cornified layer

Melanin acts like an ___________ to protect the body from harmful UV rays.

umbrella

Describe leukoderma/vitiligo.

melanin is lost in patches at different regions of the body; cause unknown

Define albinism.

complete loss of melanin including hair, brows, lashes, irides; skin appears pinkish; caused due to inheritance (recessive trait)

Define pappilae.

outer region of dermis; contains blood capillaries, nerve endings, and sense receptors

What are the five parts of a hair?

shaft root, bulb (containing pappila), follicle

What is the function of the hair bulb and follicle?

hair growth

Why does hair turn white or gray with age?

minute air spaces form in the hair in place of lost melanin

What is the technical name for "goosebumps"? What is its causative and where is it located?

piloerection; erector muscle; between hair follicle and outer part of dermis

What is the nail composed of? What are the three parts of the nail?

hard keratin plates; plate, bed, matrix

What are the two main functions of sebum?

keeps skin supple and prevents loss of water by evaporation

What are blackheads? What makes them black?

enlarged sebaceous glands; oxidation of melanin and sebum

What are sweat pores/ducts? Why are they more numerous on the palms?

the excretory part of sweat glands; surface tension for grip

List the constituents of sweat and their respective percentages of presence.

water (99%), salt/NaCl (0.2%), urea (0.8%)

What are mammary glands?

modified sweat glands

What are meibomian glands? What is its function?

modified sebaceous glands; lubricates eyes and prevents overflow of tears

What are ceruminous glands and what doe they produce?

modified sebaceous glands; cerumen/earwax

hibernate : winter sleep :: __________ : summer sleep

aestivate

Mention two synonyms for cold-blooded and warm-blooded organisms.

ectothermal, poikilothermal; endothermal, homeothermal

What is the average human body temperature?

37 degrees C in the mouth, 38 at rectum, 36 in armpits

What is the optimum temperature for the human body?

35-40 degrees C

The speed of the functioning of __________ is inversely proportional to body temperature.

enzymes

Give three sources of body heat production.

cellular chemical reactions, muscle activity, ingestion of hot food and beverages

Give four sources of body heat loss.

sweat, exhalation, urination/defecation, ingestion of cold food and beverages

Heat regulation is conducted in the __________, hence earning it the title of the body's "__________".

hypothalamus; thermostat

Define vasoconstriction. What is its function?

narrowing of blood vessels due to low external temperatures; body heat conservation

Define vasodilation.

dilation of blood vessels due to high external temperatures; loss of body heat