Hair & Scalp Properties

All of the following are living portions of hair that are below the skin surface EXCEPT __________.

• the hair bulb

• the arrector pili muscle

• the hair follicle

• the dermal papilla

Answer explanation

The arrector pili muscle is not a living portion of hair; it is a muscle that causes hair to stand up. The hair bulb, follicle, and dermal papilla are all living structures located below the skin surface.

What are the two parts of a strand of human hair?

• the root and the shaft

• the follicle and the bulb

• the dermal papilla and the arrector pili

• the cuticle and the cortex

Answer explanation

A strand of human hair consists of two main parts: the root, which is embedded in the scalp, and the shaft, which is the visible part of the hair. The other options refer to different components related to hair structure.

Which part of the living portion of the hair is defined as the structure in the skin or scalp that surrounds the hair root and anchors the hair in the skin?

• the dermal papilla

• the hair bulb

• the arrector pili muscle

• the hair follicle

Answer explanation

The hair follicle is the structure in the skin that surrounds the hair root and anchors it, making it the correct answer. The dermal papilla supports hair growth, the hair bulb is the base of the follicle, and the arrector pili muscle is responsible for hair movement.

Which portion of the hair root structure supplies nutrients so that the hair can grow?

• the hair bulb

• the dermal papilla

• the arrector pili

• the hair follicle

Answer explanation

The dermal papilla is the part of the hair root structure that supplies nutrients to the hair, promoting its growth. It is located at the base of the hair follicle and plays a crucial role in hair development.

Each of the following is a layer of the hair shaft structure EXCEPT ______.

• the cortex

• the hair fiber

• the hair cuticle

• the medulla

Answer explanation

The hair shaft structure consists of the cortex, cuticle, and medulla. The term 'hair fiber' refers to the entire hair strand, not a specific layer, making it the correct choice as it is not a layer of the hair shaft.

Which sentence best describes the medulla?

• The medulla is the hair’s outermost layer.

• The medulla is a cone-shaped elevation at the base of the hair bulb.

• The medulla is the hair’s pith or core.

• The medulla is the fibrous protein layer of the hair.

Answer explanation

The medulla refers to the innermost part of the hair, often described as the pith or core. This distinguishes it from other layers like the outermost cuticle and the fibrous cortex.

Which layer of the hair shaft provides strength, elasticity, and color?

• the hair cuticle

• the hair fiber

• the medulla

• the cortex

Answer explanation

The cortex is the layer of the hair shaft that provides strength, elasticity, and color. It contains fibrous proteins and melanin, which contribute to the hair's overall structure and pigmentation.

What are the major chemical elements that make up human hair?

• carbon, oxygen, hydrogen, nitrogen, and sulfur

• proteins, water, lipids, and traces of minerals

• amino acids and polypeptide chains

• hydrogen bonds, side bonds, and salt bonds

Answer explanation

Human hair is primarily composed of the elements carbon, oxygen, hydrogen, nitrogen, and sulfur. These elements are essential in forming the keratin proteins that make up the structure of hair.

Which of the following best describes how a disulfide bond in human hair is formed?

• Oppositely charged atoms in the hair are attracted to one another to form weak physical cross-link side bonds.

• Amino acids are chemically bonded to each other, end to end, to form a polypeptide chain.

• Oppositely charged atoms are attracted to each other to form cross-linked side bonds between adjacent polypeptide chains.

• Sulfur atoms on neighboring cysteine amino acids within polypeptide chains in the hair join.

Answer explanation

Disulfide bonds in human hair form when sulfur atoms from neighboring cysteine amino acids within polypeptide chains join together, creating strong covalent links that contribute to the hair's structure and strength.

Which of the following is a situation in which a cosmetologist would allow the hair to cool before styling?

• when salt side bonds are being formed by changes in pH during chemical servicing

• when hydrogen side bonds have been broken by the heat from a curling iron

• when peptide bonds between amino acids are broken by a heat lamp during color processing

• when disulfide bonds are converted to lanthionine bonds during servicing with a flat iron

Answer explanation

The correct choice is when hydrogen side bonds have been broken by the heat from a curling iron. Allowing the hair to cool helps these bonds reform, ensuring the style holds better.