HUBS192 progress 1

Which of the following statements about melanocytes and skin pigmentation is TRUE?

A

Melanocytes are located primarily in the hypodermis and secrete melanin into sweat glands.

B

Skin pigmentation depends solely on the number of melanocytes, not melanin production.

C

Melanocytes produce melanin that is transferred to keratinocytes, influencing skin color.

D

Melanin protects the skin by absorbing UV radiation primarily in the dermis.

Explanation

Melanocytes synthesize melanin and transfer it to keratinocytes, contributing to skin pigmentation and UV protection in the epidermis.

Question 2 of 24

Which heat transfer mechanism plays the smallest role in thermoregulation for humans under normal resting conditions?

A

Evaporation is insignificant when sweating is minimal.

B

Radiation is the primary heat loss method when environmental temperature is lower than skin.

C

Conduction plays a minimal role unless in direct contact with a cooler surface.

D

Convection rarely contributes to heat loss in humans at rest indoors.

Explanation

Under resting, indoor conditions convection is minimal, while radiation and conduction are more significant, and evaporation depends on sweating.

Question 3 of 24

Which of the following correctly identifies the layers of the skin from superficial to deep?

A

Stratum basale, dermis, hypodermis.

B

Epidermis, dermis, hypodermis.

C

Dermis, epidermis, hypodermis.

D

Hypodermis, epidermis, dermis.

Explanation

The skin layers from surface inward are epidermis, then dermis, followed by the hypodermis (subcutaneous tissue).

Question 4 of 24

Which sensory receptor in the skin is primarily responsible for detecting light touch and texture?

A

Pacinian corpuscles detect light touch and texture.

B

Merkel cells detect light touch and texture.

C

Free nerve endings detect light touch and texture.

D

Ruffini endings detect light touch and texture.

Explanation

Merkel cells function as mechanoreceptors detecting fine touch and texture at the epidermal-dermal junction.

Question 5 of 24

Which heart valve ensures unidirectional blood flow from the right atrium to the right ventricle?

A

Aortic valve regulates flow from right atrium to right ventricle.

B

Tricuspid valve prevents backflow from right ventricle into right atrium.

C

Mitral valve prevents backflow from right ventricle into right atrium.

D

Pulmonary valve prevents backflow into right atrium.

Explanation

The tricuspid valve controls flow from the right atrium to the right ventricle and prevents backflow.

Question 6 of 24

Which statement about the sinoatrial (SA) node is CORRECT?

A

The SA node is the heart's primary pacemaker initiating electrical impulses.

B

The SA node generates impulses that directly cause ventricular contraction without atrial contraction.

C

The SA node is located near the atrioventricular valve in the left atrium.

D

The SA node delays electrical conduction before ventricular contraction.

Explanation

The SA node initiates impulses that start atrial contraction and set heart rhythm; the AV node delays conduction.

Question 7 of 24

Which of the following vascular characteristics correctly describes vessel compliance?

A

Compliance is the ability of a vessel to stretch in response to pressure changes.