Mastering A&P: Integument

The epidermis consists of five layers of cells, each layer with a distinct role to play in the health, well-being, and functioning of the skin. Which of the following layers is responsible for cell division and replacement?

stratum basale

Which layer of the epidermis will be supplied with the highest levels of oxygen from the blood?

stratum basale

Pigment can be found in several layers of the epidermis. In which layer would you expect to find the cells that produce melanin?

stratum basale 10−25% of the cells in the stratum basale are melanin producing cells called melanocytes. Their branching processes extend among the surrounding cells, reaching well into the more superficial stratum spinosum layer.

Layers of the Epidermis

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

Which of the following is a metabolic function of skin?

synthesis of a vitamin D precursor Yes, this is a function of the skin carried out by chemical reactions in the skin. When sunlight bombards the skin, modified cholesterol molecules are converted to a vitamin D precursor, which is transported via the blood to the liver and kidneys, where it is converted into active vitamin D.

The reason the hypodermis acts as a shock absorber is that ________.

the major part of its makeup is adipose, which serves as an effective shock absorber

The dermis has two major layers. Which layer constitutes 80% of the dermis and is responsible for the tension lines in the skin?

the reticular layer

What feature of the prickle cells in layer C causes them to have pointy projections after tissue preparation?

their desmosome attachments Cells typically shrink during tissue preparation, and since these cells are attached by desmosomes, the membranes are pulled slightly outward at the points of cellular attachment.

Which of these is NOT a function of the layer at D?

to supply cells to replace those lost from the epidermis The hypodermis does not perform this function. Cells to replace those lost in the epidermis are provided by the basal cells of the epidermis itself.

The function of the root hair plexus is to ________. (A) bind the hair root to the dermis (B) cause apocrine gland secretion into the hair follicle (C) serve as a source for new epidermal cells for hair growth after the resting stage has passed (D) allow the hair to assist in touch sensation

allow the hair to assist in touch sensation

Layer B is composed primarily of __________.

areolar connective tissue The loose connective tissue within the papillary layer of the dermis is rich in blood vessels and cells that function in the body's defenses.

A splinter penetrated into the skin of the sole of the foot, almost to the papillary region of the dermis. Which layer of the epidermis would be the final layer injured?

basale

Layers B and C collectively form the __________. epidermis subcutaneous layer dermis hypodermis

dermis Although layers B and C can be distinguished based on their structural components, they form a continuous layer of the skin termed the dermis.

You are asked to classify an exocrine gland found in the skin based solely on the chemical analysis of its product, which turns out to be a hypotonic fluid consisting of about 99% water with a pH of 5. It contains NaCl, traces of urea and ammonia, and a peptide called dermcidin, but lacks fats and proteins. How would you classify this gland?

eccrine gland Eccrine gland secretion, commonly called sweat, is a hypotonic filtrate of the blood that passes through the secretory cells of the sweat glands and is released by exocytosis. It is 99% water, with some salts (mostly sodium chloride), traces of metabolic wastes (urea, uric acid, and ammonia), and a microbe-killing peptide called dermcidin. Normally, sweat is acidic with a pH between 4 and 6. Sebaceous glands, or oil glands, produce a fatty substance called sebum. There was no fat detected in the product analyzed.

The major regions of a hair shaft include all of the following EXCEPT ________.

external root sheath

Cells in the stratum corneum undergo mitosis to keep the layer thick and protective.

false

The eccrine sweat glands are not the primary gland involved in thermoregulation.

false

The reason that the nail bed appears pink is the presence of a large number of melanocytes in the underlying dermis.

false --> its collagen

Respiratory failure can lead to a change in the color of the skin, which is more evident in light-skinned individuals. Which pigmentation factor is affecting this change?

hemoglobin When hemoglobin is poorly oxygenated, the skin may take on a bluish-gray tint, especially in the mucous membranes and nail beds. Cyanosis, or blueness, can be a sign of respiratory or cardiovascular problems.

What is the most common cell type in the epidermis?

keratinocytes Keratinocytes are the primary cells that form the stratified layers of the epidermis.

Which skin-color-associated, pigment-producing cell is located in the labeled layer D?

melanocyte Melanocytes within the stratum basale produce the pigment melanin, which is deposited within the deeper layers of the epidermis.

A dendritic or Langerhans cell is a specialized ________.

phagocytic cell

Cells of the stratum spinosum have many interlocking desmosomes that will remain between the cells as they migrate to the stratum corneum. These cell junctions serve the body by ________.

preventing mechanical stress or trauma from damaging the epidermis

In general, skin cancer is least likely to develop in which of the following locations?

scalp The skin of scalp has hair, which gives it added protection from the damaging ultraviolet rays of the sun.

Which layer is composed primarily of dense irregular connective tissue?

C (the dermis) Layer C consists primarily of dense, interwoven fibers of collagen designed to resist tearing from any direction.

Earwax is made by __________.

Ceruminous glands are modified apocrine sweat glands found in the lining of the external ear canal. Their secretion mixes with sebum produced by nearby sebaceous glands to form a sticky, bitter substance called cerumen, or earwax, which is thought to deter insects and block entry of foreign material.

Thick skin has a more extensive dermal layer than thin skin.

False

Vitamin D precursors are produced in the skin in the presence of sunlight. These chemicals are important for the transport of sodium in our intestines.

False It is true that vitamin D precursors are produced in the skin as modified cholesterol is converted into cholecalciferol when the skin is exposed to UV light. However, vitamin D plays various roles in calcium, not sodium, metabolism. For example, calcium cannot be absorbed from the digestive tract without vitamin D.

New portions of a nail are produced at the cuticle.

False The nail matrix is the thickened proximal portion of the nail bed responsible for nail growth. The cuticle is the part of the proximal skin fold, or nail fold, that projects onto the nail body.

The dermis is a strong, flexible connective tissue layer. Which of the following cell types are likely to be found in the dermis?

Fibroblasts, macrophages, and mast cells

Which skin pigment is made in the skin as a natural defense against UV radiation?

Melanin is the only one of the three pigments (melanin, carotene, and hemoglobin) that contribute to skin color that is actually produced in the skin itself. Melanin protects the DNA of skin cells from UV radiation by absorbing the rays and dissipating the energy as heat.

Which of the following statements indicates the way in which the body's natural defenses protect the skin from the effects of UV damage?

Prolonged exposure to the sun induces melanin dispersion, which in turn acts as a natural sunscreen.

Which of the following is NOT a function of sebum?

Protection from UV radiation This is false; it is melanin (not sebum) that protects the skin from the damaging effects of UV radiation. Sebum serves as a lubricant, an antibacterial agent, and protects against water loss in low-humidity conditions.

Which glands secrete an oily product that softens the skin and hair?

Sebaceous glands secrete an oily substance called sebum. Sebum softens and lubricates the hair and skin, slows water loss from the skin when external humidity is low, and has bactericidal properties.

What is the role of the hair matrix?

The hair matrix produces hair. The hair matrix is the actively dividing area of the hair bulb that produces hair. As the matrix produces new hair cells, the older part of the hair is pushed upward, and its fused cells become increasingly keratinized and die. The hair follicle receptor, which is stimulated by bending of the hair, serves as a sensory (touch) receptor.

Which stratum of the epidermis contains the stem cells responsible for regenerating the more superficial layers?

The stratum basale is the deepest layer of the epidermis and consists of one layer of actively mitotic stem cells. The stem cells in this layer generate the cells that will migrate to the more superficial layers: spinosum, granulosum, and corneum.

The protein found in large amounts in the superficial layer of epidermal cells is keratin.

True

The glycolipids secreted by keratinocytes in the stratum granulosum help reduce water loss across the epidermis.

True Keratinocytes in the stratum granulosum accumulate two types of granules, keratohyaline granules and lamellar granules. The lamellar granules contain a water-resistant glycolipid that is secreted into the extracellular space. Together with tight junctions, the glycolipid plays a major part in slowing water loss across the epidermis.