integumentary System

Which layer of the epidermis is responsible for new cell production?

• Stratum corneum

• Stratum lucidum

• Stratum granulosum

• Stratum basale

Answer explanation

The stratum basale (also known as the basal layer) is the layer of the epidermis responsible for new cell production. It is the deepest layer of the epidermis and is in direct contact with the dermis. The stratum basale contains basal cells, which are stem cells that continually divide and produce new keratinocytes. These new cells gradually move upwards through the layers of the epidermis, undergoing a process of differentiation and keratinization, ultimately forming the protective outer layers of the skin. This constant renewal process is crucial for maintaining the integrity and function of the epidermis. Additionally, the stratum basale contains melanocytes, which produce the pigment melanin that contributes to skin color and provides protection against ultraviolet (UV) radiation.

What type of sweat gland is primarily involved in thermoregulation?

• Apocrine gland

• Eccrine gland

• Sebaceous gland

• Ceruminous gland

Answer explanation

The eccrine sweat gland is primarily involved in thermoregulation. These glands are widely distributed across the body, with a high concentration on the palms of the hands, soles of the feet, and forehead. Eccrine sweat glands secrete a watery sweat directly onto the skin surface through ducts and pores. When body temperature rises, the sweat produced by these glands evaporates from the skin surface, helping to cool the body and dissipate excess heat. This evaporative cooling mechanism is a critical process in maintaining homeostasis and regulating body temperature. Eccrine glands are active throughout life and are controlled by the autonomic nervous system, responding to heat and emotional stress to ensure effective thermoregulation.

The hypodermis is technically considered part of the skin.

• True

• False

Answer explanation

The statement "The hypodermis is technically considered part of the skin" is false because the hypodermis, also known as the subcutaneous layer or superficial fascia, is not considered a part of the skin itself. The skin is composed of two main layers: the epidermis and the dermis.

1. Epidermis: The outermost layer of the skin, composed of stratified squamous epithelium. It serves as the primary barrier against environmental damage, pathogens, and water loss.

2. Dermis: The layer beneath the epidermis, composed of dense irregular connective tissue. It contains blood vessels, nerves, hair follicles, and glands. The dermis provides structural strength and elasticity to the skin.

The hypodermis lies below these two layers and is primarily composed of loose areolar and adipose (fat) tissue. Its primary functions include:

• Anchoring: Connecting the skin to underlying structures such as muscles and bones.

• Insulation: Providing thermal insulation to conserve body heat.

• Cushioning: Acting as a shock absorber to protect underlying tissues from mechanical injury.

• Energy Storage: Serving as an energy reserve by storing fat.

While the hypodermis plays a crucial role in supporting the functions of the skin, it is anatomically distinct from the epidermis and dermis. Therefore, it is not technically considered part of the skin but rather an underlying supportive layer.

The primary pigment responsible for skin color is melanin, produced by cells called _________.

Answer explanation

The primary pigment responsible for skin color is melanin, produced by cells called melanocytes. Melanocytes are located in the stratum basale, the deepest layer of the epidermis. They synthesize melanin, which is then transferred to the surrounding keratinocytes. The amount and type of melanin produced by these melanocytes, along with its distribution in the skin, determine an individual's skin color. Melanin not only provides pigmentation but also offers protection against ultraviolet (UV) radiation by absorbing and dissipating harmful UV rays, thereby reducing the risk of DNA damage in skin cells.

Explain the difference between the papillary and reticular layers of the dermis and their respective functions.

Answer explanation

The dermis, the layer of skin beneath the epidermis, is divided into two distinct regions: the papillary layer and the reticular layer, each with unique structures and functions.

1. Papillary Layer:

   • Structure: The papillary layer is the superficial portion of the dermis, located just beneath the epidermis. It is composed of loose areolar connective tissue, which includes thin collagen and elastic fibers. This layer contains finger-like projections called dermal papillae that extend into the epidermis.

   • Functions:

     • Nutrient Exchange: The dermal papillae increase the surface area for exchange of gases, nutrients, and waste products between the epidermis and dermis. Capillary loops within the papillae supply oxygen and nutrients to the epidermal cells.

     • Sensory Reception: This layer contains Meissner's (tactile) corpuscles, which are sensory receptors sensitive to light touch.

     • Support and Flexibility: The loose connective tissue allows for flexibility and provides a supportive framework for the epidermis.

2. Reticular Layer:

   • Structure: The reticular layer is the deeper, thicker part of the dermis, making up about 80% of the dermal thickness. It is composed of dense irregular connective tissue, which includes thick bundles of collagen and elastic fibers arranged in various directions.

   • Functions:

     • Strength and Elasticity: The dense irregular connective tissue provides tensile strength, allowing the skin to withstand stretching and mechanical stresses. The elastic fibers contribute to the skin's elasticity and flexibility.

     • Housing of Structures: The reticular layer contains various structures such as hair follicles, sebaceous (oil) glands, sweat glands, blood vessels, and nerves. These structures are essential for the skin's protective and regulatory functions.

     • Deep Sensory Reception: This layer contains Pacinian (lamellated) corpuscles, which are sensory receptors that detect deep pressure and vibration.

In summary, the papillary layer primarily provides support, nutrient exchange, and sensory reception for light touch, while the reticular layer provides strength, elasticity, and houses the skin's accessory structures. Both layers work together to maintain the integrity and function of the skin.

Which layer of the epidermis is responsible for new cell production?

• Stratum basale

• Stratum corneum

• Stratum granulosum

• Stratum lucidum

What type of sweat gland is primarily involved in thermoregulation?

• Apocrine gland

• Eccrine gland

• Sebaceous gland

• Ceruminous gland

The hypodermis is technically considered part of the skin.

• True

• False

The primary pigment responsible for skin color is _________, produced by cells called _________.

Explain the difference between the papillary and reticular layers of the dermis and their respective functions.