the stratum corneum the outermost layer of the epidermis is primarily composed of

ATI TEAS 7

TEAS 7 science practice

1. What is the primary composition of the stratum corneum, the outermost layer of the epidermis?

A. Keratinized dead cells
B. Melanocytes
C. Langerhans cells
D. Merkel cells

Correct answer: A

Rationale: The stratum corneum, the outermost layer of the epidermis, is primarily composed of keratinized dead cells. These cells are flattened, fully keratinized, and lack nuclei, serving a protective function for the skin. Melanocytes are responsible for producing melanin, providing skin pigmentation. Langerhans cells are involved in the immune response within the skin. Merkel cells are associated with sensory functions in the skin, particularly in touch sensations. Therefore, the correct answer is A as it accurately reflects the main constituent of the stratum corneum, which acts as a barrier against external factors.

2. Immunoglobulin G (IgG) is the most abundant antibody type, responsible for:

A. Immediate allergic reactions
B. Neutralizing toxins and viruses
C. Activating other immune cells
D. Protecting newborns from infections

Correct answer: B

Rationale: Immunoglobulin G (IgG) is indeed the most prevalent antibody type in the blood and tissue fluids. Its primary functions include neutralizing toxins and viruses, promoting phagocytosis, and activating the complement system. IgG plays a crucial role in long-term immunity and provides passive immunity to newborns by crossing the placenta, safeguarding them from infections. Immediate allergic reactions are mainly mediated by IgE, not IgG. While IgM is known for activating other immune cells, IgG focuses on other key functions within the immune response, such as neutralizing pathogens and enhancing phagocytosis. Therefore, the correct answer is B, as IgG is primarily involved in neutralizing toxins and viruses, rather than the other options presented.

3. How many chromosomes must a normal human sperm cell contain?

A. An X chromosome.
B. A Y chromosome.
C. 23 chromosomes.
D. Both an X and Y chromosome.

Correct answer: C

Rationale: A normal human sperm cell contains a total of 23 chromosomes, half the number found in a typical human cell which has 46 chromosomes. This includes 22 autosomes and one sex chromosome, which can be either an X or a Y chromosome. Therefore, the correct answer is that a normal human sperm cell must contain 23 chromosomes. Choices A and B are incorrect because a single sex chromosome alone does not represent the total number of chromosomes in a sperm cell. Choice D is incorrect because a sperm cell carries only one sex chromosome, either X or Y, not both.

4. What is the difference between a real image and a virtual image formed by a lens?

A. Real images can be projected onto a screen, while virtual images cannot.
B. Real images are always upright, while virtual images can be inverted.
C. Real images are formed by converging lenses, while virtual images are formed by diverging lenses.
D. All of the above are true.

Correct answer: A

Rationale: The correct answer is A. Real images can be projected onto a screen because they are formed by the actual convergence of light rays, while virtual images cannot be projected onto a screen as they appear to diverge from a point behind the lens. Real and virtual images do not have a consistent orientation (upright or inverted), so option B is incorrect. Real images are formed by both converging and diverging lenses depending on the specific scenario, so option C is not a definitive distinction. Option D is incorrect as not all the statements are true. Therefore, the only accurate general distinction between real and virtual images is that real images can be projected onto a screen, while virtual images cannot.

5. Which of the following statements regarding heart valves is correct?

A. The atrioventricular valves lie between the atria and the ventricles.
B. The pulmonary semilunar valve lies between the right ventricle and the pulmonary trunk.
C. The atrioventricular valves prevent backflow into the atria when the ventricles contract.
D. All of the above

Correct answer: D

Rationale: All of the statements are correct regarding heart valves. Choice A is accurate as the atrioventricular valves indeed lie between the atria and the ventricles. Choice B correctly identifies the location of the pulmonary semilunar valve. Choice C is true as the atrioventricular valves do prevent backflow into the atria during ventricular contraction. Therefore, selecting 'All of the above' as the correct answer is appropriate as all statements are accurate.