In which organ of the human body is urea produced as a result of the breakdown of amino acids?

Answer Explanation

d) The laryngopharynx is composed partially of cartilage.

- True: The statement that the laryngopharynx is composed partially of cartilage is true. The pharynx, commonly known as the throat, is a muscular tube that extends from the base of the skull to the level of the sixth cervical vertebra. It serves as a passageway for both air and food. The pharynx is divided into three regions: the nasopharynx, oropharynx, and laryngopharynx.

a) It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.

- False: The pharynx extends from the nasal and oral cavities superiorly to the esophagus and larynx inferiorly, not anteriorly.

b) The oropharynx is continuous superiorly with the nasopharynx.

- False: The oropharynx is continuous inferiorly with the oral cavity, not superiorly with the nasopharynx. The nasopharynx is continuous superiorly with the nasal cavity.

c) The nasopharynx is involved in digestion.

- False: The nasopharynx is primarily involved in respiration and the passage of air. It contains the openings of the auditory tubes and tonsils but is not directly involved in digestion.

Answer Explanation

A. plicae circulares

- Correct: The small intestine possesses permanent folds along its length known as plicae circulares, also called circular folds or valvulae conniventes. These folds are permanent transverse ridges of the mucosa and submucosa that project into the lumen of the small intestine. They increase the surface area for absorption and digestion by slowing the passage of chyme and increasing contact between chyme and the intestinal lining, facilitating nutrient absorption.

B. haustra

- Incorrect: Haustra are pouches or sacculations formed by the muscularis externa of the colon (large intestine), not the folds of the small intestine.

C. villi

- Incorrect: Villi are finger-like projections of the mucosa of the small intestine that extend into the lumen. While villi increase the surface area for absorption, they are not permanent folds along the length of the small intestine.

D. intestinal crypts

- Incorrect: Intestinal crypts, also known as crypts of Lieberkühn, are invaginations of the epithelium located between villi in the mucosa of the small intestine. They contain stem cells that continuously divide and give rise to new epithelial cells, helping to replenish the epithelial lining of the intestine. Crypts are not permanent folds along the length of the small intestine.

Answer Explanation

d. all of the above

- Correct: All of the statements are true regarding the stomach:

a. muscles churn and mix the food with acids and enzymes: The stomach has muscular walls that contract and relax to mechanically churn and mix food with gastric juices, including hydrochloric acid and various enzymes (such as pepsin) that aid in the digestion of proteins.

b. glands make 3 quarts of digestive juices each day: The gastric glands in the lining of the stomach produce gastric juice, which contains hydrochloric acid, enzymes (such as pepsinogen), mucus, and intrinsic factor. These glands collectively secrete about 2 to 3 liters (quarts) of gastric juice per day.

c. food leaves as a thick liquid called chyme: After mixing with gastric juices and undergoing partial digestion in the stomach, food is transformed into a semi-liquid mixture called chyme. Chyme is then gradually released from the stomach into the small intestine for further digestion and absorption.

Therefore, all of the statements accurately describe processes that occur in the stomach.