Ch.23 The digestive system Openstax / Westcott Physiology

Which of these statements about bile is true? About 500 mL is secreted daily. Its main function is the denaturation of proteins. It is synthesized in the gallbladder. Bile salts are recycled.

Bile salts are recycled bile is a very important component of an intestinal digestive mixture of juices. Synthesized in the liver and secreted into the duodenum it functions to emulsify fats. The bile salts are reabsorbed in the ileum and transported to the liver for recycling.

Which part of the large intestine attaches to the appendix? cecum ascending colon transverse colon descending colon

Cecum The large intestine starts at the cecum. The appendix is a tube like structure that attaches to the cecum. It contains lymphoid tissues giving it some immunological function.

you can watch a short video of what happens to the food you eat as it passes from your mouth to your intestine. Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food?

Change in consistency of food from largely sized bites to chewed semi solid paste (Bolus) and then to a fluid like (chyme) consistency helps in both the movement of food down the alimentary canal and finally the absorption of their nutrients in the intestines

Which of these ingredients in saliva is responsible for activating salivary amylase? mucus phosphate ions chloride ions urea

Chloride ions The binding of chloride ions as the allosteric binding sites on the salivary amylase activates this enzyme. The binding of these ions triggers a conformational change in enzyme structure converting it from an inactive to active state.

Which structure is located where the esophagus penetrates the diaphragm? esophageal hiatus cardiac orifice upper esophageal sphincter lower esophageal sphincter

Esophageal Hiatus

Which phase of deglutition involves contraction of the longitudinal muscle layer of the muscularis? voluntary phase buccal phase pharyngeal phase esophageal phase

Esophageal phase deglutition- the action or process of swallowing the esophageal phase of deglutition involves both the circular and longitudinal muscles of the muscularis layer to contract and push bolus forward by peristalsis

Which of the following organs is supported by a layer of adventitia rather than serosa? esophagus stomach small intestine large intestine

Esophagus The digestive organs near the ventral surface of the vertebral column are lined with a layer of adventitious tissue rather than serosa. Adventitious tissue made of collagen fibers help in supporting these structures and holding them erect in place. serosa lines the organs of the digestive system that are located deep within the abdominal cavity and are bound by loose connective tissue.

Chewing is the enzymatic breakdown of food T/F?

False

In the colon, there is a lot of digestion that occurs T/F?

False

chyme is a more digested bolus that then moves into the esophagus T/F?

False

Which of these statements about reflexes in the GI tract is false? Short reflexes are provoked by nerves near the GI tract. Short reflexes are mediated by the enteric nervous system. Food that distends the stomach initiates long reflexes. Long reflexes can be provoked by stimuli originating outside the GI tract.

Food that distends the stomach initiates long reflex The distention in the stomach caused by food initiates short reflexes to enhance secretions of digestive enzymes.

Where does the majority of chemical digestion in the stomach occur? fundus and body cardia and fundus body and pylorus body

Fundus and body - they are the central regions of the stomach where gastric juices comprising the acid and enzymes are secreted. Once the acid mixes with the bolus rigorous churning and chemical digestion convert it to a fluid-like consistency called chyme. this is acted upon by the gastric enzymes to digest it.

Parietal cells secrete ________. gastrin hydrochloric acid pepsin pepsinogen

Hydrochloric acid - parietal cells are specialized to secrete hydrochloric acid and intrinsic factor

Which of these nutrients is absorbed mainly in the duodenum? glucose iron sodium water

Iron The small intestine absorbs iron. The major part of iron absorption occurs in the duodenum and the jejunum. Once absorbed in the blood stream, it is transported in the body conjugated to transferrin molecules.

Which of these is most associated with villi? haustra lacteals bacterial flora intestinal glands

Lacteals Lacteals are lymphatic vessels that are associated with the villi in the small intestines. They absorb the fatty acids and glycerides generated from the digestion of fats. the circulatory folded ridges of the epithelia of the small intestines are adorned with hair like projections called the villi. the villi increase the surface area of absorption. they are lined by muscosal epithelium with specialized absorptive cells. Richly supplied with blood vessels the villi make absorption of digested food easier. each villus also has a lacteal associated with it for the absorption of end products of fat digestion.

Which of these organs is not considered an accessory digestive structure? mouth salivary glands pancreas liver

Mouth The accessory digestive structures include teeth, tongue, salivary glands, liver, pancreas, and gallbladder. Accessory digestive organs are structures that help in the process of digestion in some or the other manner but are not directly part of the alimentary canal. The mouth marks the beginning of the digestive system where we ingest food and cannot be considered an accessory organ.

Where does the chemical digestion of starch begin? mouth esophagus stomach small intestine

Mouth The chemical and mechanical digestion of food begins in the mouth and continues till the proximal end of the small intestine. In the distal end of the small intestine and the large intestine absorption of digested food and water occurs.

Of the three major food classes (carbohydrates, fats, and proteins), which is digested in the mouth, the stomach, and the small intestine?

Mouth: Carbohydrate digestion takes place in the mouth. starch in food is acted upon by the salivary amylase to break it down to maltose / The lingual lipase acts on triglycerides and fat digestion has begun Stomach: Proteins are partially digested by the pepsin in the stomach. gastric lipase breaks down some fats. small intestine: all 3 are digested - carbs are digested by enzymes like amylase, lactase, maltase

Where are most fat-digesting enzymes produced? small intestine gallbladder liver pancreas

Pancreas Pancreatic juice contains pancreatic lipase, an enzyme that digests fats. The action of bile on chyme emulsifies the fats and lipids in it to triglycerides.

Pancreatic juice ________. deactivates bile. is secreted by pancreatic islet cells. buffers chyme. is released into the cystic duct.

Pancreatic juice buffers chyme. Pancreatic juice is rich in bicarbonate ions. This renders it alkaline PH in the range of 7.1 to 8.2. The chyme that enters the small intestine is acidic due to the hydrochloric acid it mixes with in the stomach. The bicarbonate ions in the pancreatic juice neutralise the chyme, inactivate the pepsin from the stomach and provide an alkaline environment for the intestinal enzymes to function

What is the role of the small intestine's MALT? secreting mucus buffering acidic chyme activating pepsin preventing bacteria from entering the bloodstream

Preventing bacteria from entering the bloodstream MALT (mucosa-associated lymphoid tissue) is embedded in the lamina propria. It containts many lymphocytes that attack the pathogens that come along with the food. In addition, there are lymph nodules that too provide immune defense.

Which of these processes occurs throughout most of the alimentary canal? ingestion propulsion segmentation absorption

Propulsion The peristaltic motion of food begins in the esophagus and continues all the way down to the large intestines. The speed of the peristaltic motion , however , varies from region to region. This peristaltic motion causes propulsion of food down the alimentary canal. Ingestion only occurs in the mouth segmentation only occurs in the small intestine absorption of nutrients occur mainly in the small intestine

In which part of the alimentary canal does most digestion occur? stomach proximal small intestine distal small intestine ascending colon

Proximal small intestine - it has accessory glans associated with the liver, pancreas, and gall bladder. digestive enzyme secreted from the duodenum mix with pancreatic juice and bile. partially digested carbohydrates and proteins from the stomach are completely digested here. undigested lipid and fat are acted upon by pancreatic lipase and blue to form fatty acids and glycerol.

During gastric emptying, chyme is released into the duodenum through the ________. esophageal hiatus pyloric antrum pyloric canal pyloric sphincter

Pyloric sphincter The distal end of the stomach opens to the duodenum, the initial region of the small intestines. The opening of the stomach into the duodenum is guarded by a smooth circular muscle called the pyloric sphincter.

Watch this animation that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?

Rugae are ridges or folds in the internal walls of the stomach that give it its corrugated appearance. two functions: - help in stretching the stomach for the accommodation of large amounts of food - help in holding the food during digestion and assist in the churning movement of the stomach

In the small intestine, the products of food digestion are absorbed by different structures in the villi. Which structure absorbs and transports fats?

The fats are digested and absorbed in the small intestine. The lymphatic capillaries called the lacteal absorbs the transport fats the intestinal walls are thrown into the folds called the villi. each villus is associated with a set of capillaries- arteriole and venules- along with the lacteal. The lacteals are lymphatic capillaries that absorb end products of fat digestion. These lacteals join to form lymph vessels that transport the fatty acids to the different cells of the body

At rest, about 1500 mL of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?

The hepatic portal systems carries blood rich in nutrients from the gastrointestinal tract to the liver. The hepatic portal system supplies 75% of the blood flowing through the liver. * Hepatic portal vein carries oxygen rich blood to the liver and meets almost 50% of the livers oxygen demand. The remaining is taken care of by the hepatic artery

Which of these statements about the pharynx is true? It extends from the nasal and oral cavities superiorly to the esophagus anteriorly. The oropharynx is continuous superiorly with the nasopharynx. The nasopharynx is involved in digestion. The laryngopharynx is composed partially of cartilage.

The oropharynx is continuous superiorly with the nasopharynx

The first place your food will go is the oral cavity. T/F?

True

Which of these is involved in the chemical digestion of protein? pancreatic amylase trypsin sucrase pancreatic nuclease

Trypsin The group of enzymes that chemically digest proteins is referred to as proteinases. This group includes enzymes like pepsin, trypsin, chymotrypsin, carboxypeptidase, and others

Which of the following membranes covers the stomach? falciform ligament mesocolon parietal peritoneum visceral peritoneum

Visceral peritoneum - it covers all organs present in the abdominal cavity ( stomach, liver, pancreas, spleen, gallbladder and others) The membrane that lines the abdominal cavity is the parietal peritoneum

Which of these processes occurs in the mouth? ingestion mechanical digestion chemical digestion all of the above

all of the above

Which of the following stimuli activates sensors in the walls of digestive organs? breakdown products of digestion distension pH of chyme all of the above

all of the above The stimuli received by various receptors present in the digestive system help in smoothly carrying out the process of digestion

Which of these cells secrete hormones? parietal cells mucous neck cells enteroendocrine cells chief cells

enteroendocrine cells - secrete hormones like gastrin, somatostatin, motilin, cholecystokinin, enteroglucagon, and others. They are present throughout the walls of the GI tract reason for wrong answers: Parietal cells produce hydrochloric acid in the stomach no hormones mucus neck cells secrete mucus which lubricates chyme Chief cells produce pesinogen in the stomach

for an overview of digestion of food in different regions of the digestive tract. Note the route of non-fat nutrients from the small intestine to their release as nutrients to the body.

non-fatty nutrients after absorption in the small intestine enter the bloodstream to reach out to the various cells of the body. The table summarizes the route of non-fat nutrients from the small intestine to their release in the cells of the body

During which stage of swallowing is there a risk of food entering respiratory pathways and how is this risk blocked?

swallowing has 3 phases- oral, pharyngeal and esophageal. Pharyngeal is the phase that hold the risk of possibility of food entering the respiratory pathways because this is wear swallowing occurs The epiglottis is a vital structure to block the entry of food into the respiratory passage during the act of swallowing. if this flap defaults and food enters into the trachea and bronchi coughing occurs to expel the food from there

A bolus is a sphere of digested food. T/F

true