D313 Anatomy and Physiology II - Set 1 - Part 1

Correct Answer: Absorption

Option c is correct because absorption is the stage where monomers produced by chemical digestion cross the epithelial lining of the intestine and enter the blood or lymphatic system. Option a is incorrect because ingestion refers only to the act of taking food into the mouth, which is the very first step and does not involve nutrient transfer. Option b is incorrect because defecation is the final elimination of indigestible material through the anus and has nothing to do with nutrient transport into the bloodstream. Option d is incorrect because chemical digestion is the enzymatic breakdown of molecular bonds that produces monomers, but it does not describe the transfer of those monomers into blood.

Correct Answer: Mechanical digestion

Option a is correct because mechanical digestion physically reduces food particle size through actions like chewing and churning without altering the chemical structure or breaking molecular bonds. Option b is incorrect because chemical digestion specifically involves enzymes breaking covalent bonds within food molecules, which is a molecular change rather than a physical size reduction. Option c is incorrect because absorption occurs when broken-down nutrient monomers pass through the intestinal epithelium into the bloodstream, which happens well after food is chewed. Option d is incorrect because propulsion refers to the movement of food through the alimentary canal via peristalsis, not the physical breakdown of food into smaller pieces.

Correct Answer: Peristalsis

Option d is correct because peristalsis is the rhythmic wave-like contraction and relaxation of smooth muscle that propels food forward through the alimentary canal from esophagus onward. Option a is incorrect because segmentation involves localized contractions that mix and churn food within a segment of the intestine rather than pushing it forward along the tract. Option b is incorrect because mechanical digestion is a broad term that includes chewing and churning to reduce particle size, but it does not specifically describe forward propulsion. Option c is incorrect because absorption is the process of nutrient monomers crossing the intestinal lining into the blood or lymph, which is unrelated to the muscular movement of food.

Correct Answer: Mouth to anus

Option b is correct because the alimentary canal is defined as the continuous hollow tube extending from the mouth to the anus, including all organs along that path. Option a is incorrect because the pharynx is already partway along the alimentary canal and does not represent its true starting point, which begins at the mouth. Option c is incorrect because the esophagus skips the mouth, pharynx, and oral cavity at the start, and the large intestine does not include the rectum or anus. Option d is incorrect because the stomach excludes several upstream structures including the mouth, pharynx, and esophagus, so it cannot be the starting landmark of the canal.

Correct Answer: Liver, gallbladder, and pancreas

Option a is correct because the liver, gallbladder, and pancreas are classified as accessory digestive organs that support digestion through bile and enzyme secretion without forming the canal. Option b is incorrect because the stomach, duodenum, and jejunum are all segments of the alimentary canal itself and food passes directly through each of these structures. Option c is incorrect because the esophagus, stomach, and ileum are all hollow tube segments of the alimentary canal through which food physically travels during digestion. Option d is incorrect because the cecum, colon, and rectum are all divisions of the large intestine, which is a major section of the alimentary canal and not accessory.

Correct Answer: Mucosa

Option d is correct because the mucosa is the innermost layer of the alimentary canal wall, directly lining the lumen, and it is responsible for both secretion and absorption. Option a is incorrect because the submucosa lies just outside the mucosa and is composed of loose areolar connective tissue with blood vessels, not the layer that contacts food. Option b is incorrect because the muscularis externa is the smooth muscle layer responsible for peristalsis and segmentation, positioned further outward from the lumen than the mucosa. Option c is incorrect because the serosa is the outermost layer of the alimentary canal wall that prevents friction between organs, located farthest from the lumen and food.

Correct Answer: It drives powerful churning movements

Option b is correct because the muscularis externa is thicker in the stomach to generate the strong churning contractions needed for heavy mechanical digestion and mixing food with gastric juices. Option a is incorrect because hydrochloric acid is secreted by parietal cells located in the gastric glands of the mucosa layer, not by smooth muscle cells in the muscularis. Option c is incorrect because nutrient absorption is a function of the mucosa, primarily in the small intestine, and is not a role performed by the smooth muscle layer. Option d is incorrect because protective mucus is produced by mucous cells in the mucosal lining of the stomach, which is a completely separate layer from the muscularis externa.

Correct Answer: Serosa

Option c is correct because the serosa, also called the visceral peritoneum, is the smooth outermost membrane covering the stomach and intestines that prevents friction between abdominal organs. Option a is incorrect because the mucosa is the innermost layer that lines the lumen and is involved in secretion and absorption, not in reducing friction between organs. Option b is incorrect because the muscularis externa is the smooth muscle layer responsible for peristaltic contractions and is located between the submucosa and the serosa layers. Option d is incorrect because the submucosa is the connective tissue layer containing blood vessels that sits between the mucosa and muscularis, not on the outer organ surface.

Correct Answer: Submucosa

Option a is correct because the submucosa is composed of loose areolar connective tissue containing an extensive blood vessel network that transports nutrients absorbed through the mucosa to systemic circulation. Option b is incorrect because the serosa is the outermost protective membrane that reduces friction between organs and does not contain the primary nutrient transport blood vessel network. Option c is incorrect because the muscularis externa is the smooth muscle layer generating peristalsis and segmentation, and its primary role is motility rather than nutrient transport. Option d is incorrect because while the mucosa is where absorption occurs across the epithelium, the extensive blood vessel network for transporting those nutrients resides in the submucosa layer.

Correct Answer: Squamous cells resist abrasion better

Option d is correct because stratified squamous epithelium is found at the mouth, pharynx, and anus where physical abrasion from food entry and waste exit requires durable protection. Option a is incorrect because while columnar cells do secrete mucus, the primary reason for tissue variation across regions is the mechanical stress each area faces, not mucus output. Option b is incorrect because stratified squamous epithelium is not designed for nutrient absorption at all, and absorption primarily occurs through simple columnar epithelium in the small intestine. Option c is incorrect because acid resistance in the stomach is provided by the thick mucus barrier secreted by mucous cells, not by the columnar cell type itself being acid resistant.

Correct Answer: Soft palate

Option b is correct because the soft palate is a moveable fold of tissue at the posterior roof of the mouth that reflexively rises to close off the nasopharynx during swallowing. Option a is incorrect because the hard palate is the rigid, bone-backed anterior portion of the mouth roof that provides a firm surface for the tongue to push food against. Option c is incorrect because the tongue is a muscular organ that moves food during chewing and pushes the bolus toward the pharynx, but it does not seal the nasal passages. Option d is incorrect because the epiglottis is a cartilage flap in the larynx that covers the tracheal opening during swallowing, protecting the airway rather than the nasal passages.

Correct Answer: Pons and medulla oblongata

Option c is correct because the salivary nuclei responsible for controlling salivation are located in the pons and medulla oblongata of the brainstem, responding to both sensory and conditioned stimuli. Option a is incorrect because while the cerebral cortex can influence salivation through conditioned reflexes like thinking about food, the actual salivary control nuclei reside in the brainstem. Option b is incorrect because the hypothalamus plays roles in hunger and thirst regulation but does not house the salivary nuclei that directly control the activation of salivary glands. Option d is incorrect because the cerebellum coordinates motor movements and balance while the midbrain handles visual and auditory reflexes, neither of which contains salivary control centers.

Correct Answer: Parotid gland

Option a is correct because the parotid gland is the largest of the three paired salivary glands and is located within the cheeks, producing a significant portion of daily saliva. Option b is incorrect because the sublingual gland is the smallest of the three major salivary glands and is located beneath the tongue on the floor of the mouth, not within the cheeks. Option c is incorrect because the submandibular gland is located beneath the lower jaw, not within the cheek tissue, and it is the second largest rather than the largest salivary gland. Option d is incorrect because buccal gland is not one of the three major paired salivary glands studied in this context, and the term refers to minor glands in the cheek lining.

Correct Answer: Incisors

Option d is correct because incisors are the most anterior and medially positioned teeth in the dental arch, and their flat edge shape is specifically adapted for cutting and biting food. Option a is incorrect because canines are located just lateral to the incisors and are characterized by their sharp, pointed shape designed primarily for tearing food rather than cutting. Option b is incorrect because premolars are positioned posterior to the canines and serve as smaller grinding teeth, not as the anterior cutting teeth described in the question. Option c is incorrect because molars are the large grinding teeth found at the most posterior positions in the dental arch and are designed for crushing food, not for cutting.

Correct Answer: Salivary amylase

Option c is correct because salivary amylase is the enzyme present in saliva that begins chemical digestion of starches in the oral cavity, breaking polysaccharides down into simpler sugar monomers. Option a is incorrect because pepsin is a protein-digesting enzyme that is activated in the acidic environment of the stomach and does not function in the oral cavity at all. Option b is incorrect because trypsin is a protease secreted by the pancreas into the small intestine for protein digestion and is not present in saliva or the mouth. Option d is incorrect because pancreatic lipase is a fat-digesting enzyme released by the pancreas into the duodenum and plays no role in starch digestion within the oral cavity.

Correct Answer: Fundus

Option a is correct because the fundus is the dome-shaped upper portion of the stomach that sits above the level of the cardiac region where the esophagus connects to the stomach. Option b is incorrect because the pyloric region is the inferior portion of the stomach containing the pyloric sphincter that controls the release of chyme into the duodenum below. Option c is incorrect because the body is the main central region of the stomach located between the fundus above and the pyloric region below, not the dome-shaped upper area. Option d is incorrect because the cardiac region is the area immediately surrounding the entrance from the esophagus where the food bolus first enters, not the dome-shaped superior portion.

Correct Answer: Chief cells

Option d is correct because chief cells secrete pepsinogen, the inactive enzyme precursor that is converted into pepsin by hydrochloric acid in the stomach to begin protein digestion. Option a is incorrect because parietal cells secrete hydrochloric acid and intrinsic factor, and while the acid activates pepsinogen, the parietal cells themselves do not produce the enzyme precursor. Option b is incorrect because G-cells are endocrine cells that secrete the hormone gastrin, which stimulates acid production and motility, but they do not release any enzyme precursors. Option c is incorrect because mucous neck cells produce the protective mucus layer that coats the stomach lining to prevent self-digestion, not the inactive enzyme precursor pepsinogen.

Correct Answer: Gastrin

Option b is correct because gastrin is the hormone released by G-cells when food enters the stomach, and it stimulates parietal cells to produce hydrochloric acid and chief cells for enzymes. Option a is incorrect because secretin is released by the duodenum in response to acidic chyme and stimulates the pancreas to release bicarbonate, which is an intestinal rather than gastric response. Option c is incorrect because cholecystokinin is released by the duodenum in response to fats and proteins and triggers gallbladder contraction and pancreatic enzyme secretion, not initial gastric activity. Option d is incorrect because pepsinogen is an inactive enzyme precursor secreted by chief cells, not a hormone, and it does not trigger the gastric secretion cascade upon food arrival.

Correct Answer: Pyloric sphincter

Option c is correct because the pyloric sphincter is the ring of smooth muscle at the inferior end of the stomach that regulates the controlled release of chyme into the duodenum. Option a is incorrect because the lower esophageal sphincter controls the passage of food from the esophagus into the stomach at the superior end, not the release of chyme into the intestine. Option b is incorrect because the ileocecal valve is located at the junction between the ileum and the cecum, which is the transition from the small intestine into the large intestine. Option d is incorrect because the upper esophageal sphincter controls the passage of the food bolus from the pharynx into the esophagus during the swallowing process, far upstream from the stomach exit.

Correct Answer: Rugae

Option a is correct because rugae are the visible folds on the interior stomach surface that flatten out as the stomach fills, allowing significant expansion and increasing secretory surface area. Option b is incorrect because villi are the tiny finger-like projections found in the small intestine mucosa that increase surface area for nutrient absorption, not the expandable stomach folds. Option c is incorrect because circular folds, also called plicae circulares, are permanent ridges found in the small intestine wall and are not the expandable folds characteristic of the stomach. Option d is incorrect because microvilli are microscopic hair-like extensions on individual epithelial cells of the small intestine forming the brush border, far too small to be visible stomach folds.