Digestive Anatomy - AP Biology

The villi are helpful in increasing the surface area of the small intestine. This greatly increases the absorptive capabilities of the small intestine. The stomach has no villi, and does not contribute to absorption of macromolecules.

The duodenum, in the small intestine, is a site of protein, carbohydrate, and fat digestion.

The jejunum is a site of protein and fat absorption. The ileum is a site of salt, vitamin, and excess molecule absorbtion. The colon is a segment of the large intestine for water and ion absortion. Each of these work to absorb different molecules, but do not significantly contribute to their digestion.

The role of the gall bladder is to store bile salts, but it does not produce them. Rather, bile salts are produced by the liver and transported to the gall bladder for storage.

The hepatic portal system involves the capillaries of the small intestine and capillaries of the liver. A portal system refers to two different capillary beds, connected by arterioles, that both receive blood before it returns to the heart for reoxygenation. The prefix "hepa-" refers to the liver.

The pancreatic duct transfers digestive enzymes from the pancreas into the lumen of the small intestine. Lacteal vessels receive fats from the small intestine and carry them into the lymphatic system. The pulmonary circuit refers to the region of the circulatory system that carries blood from the right ventricle to the lungs, and back to the left atrium.

When digested food exits the stomach, it passes through the pyloric sphincter and enters the duodenum, the first region of the small intestine. The duodenum is the introduction point for the pancreatic digestive enzymes, as well as the neutralization of stomach acid. The majority of chemical digestion occurs in the duodenum. The middle region of the small intestine is the jejunum, and the final region is the ileum. These regions are primarily responsible for nutrient absorption and have the largest concentration of microvilli. After passing through the ileum, the digested matter enters the large intestine.

Food is converted into a bolus upon swallowing, then into chyme in the stomach. The chyme travels from the stomach into the first part of the small intestine, the duodenum. The chyme then moves through the jejunum, then through the ileum before entering the large intestine. Villi are finger-like projections of the small intestine that increase the surface area of the epithelium to maximize nutrient absorption. The ilium is a part of the hip bone.

Pepsin is a protein degrading enzyme that is released by the stomach. All the other choices are released by the pancreas into the duodenum.

Microvilli are found at the microscopic level within the digestive tract to help increase surface area. The increased surface area aids in the absorption of nutrients as they pass through the small intestine. Microvilli allow for folds in the digestive tract, which in turn, increase the amount of area available for nutrient absorption.

The esophagus is responsible for transporting food from the mouth to the stomach via peristalsis, which consists of smooth muscle contractions, but does not help digest the food content in the process. The mouth, stomach, and small intestine, however, all help in the process of food digestion. The mouth introduces enzymes in the saliva, the stomach introduces pepsin, and the small intestine introduces a number of other enzymes for digestion of macromolecules.

Cholecystokinin (CCK) is a hormone released by the duodenum to signal and stimulate accessory organs for digestive enzymes. Salivary amylase digests starch in the mouth, while pepsin is used to digest proteins in the stomach.

Methane is produced in the cecum as a result of blind outpocketing, during which E. coli organisms release the gas as a biproduct of digestion. Detoxing chemicals from the blood, forming urea, and producing bile are just three of the functions of the liver.

Food travels in this order through the digestive tract: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus.

The larynx is commonly confused with the pharynx due to their similar names, but it is actually involved in speaking or making sounds. The pharynx splits into the trachea and esophagus. Food and liquids travel down the esophagus, while air travels down the trachea; the larynx is located at the top of the trachea.

After entering the mouth, food is transferred to the pharynx before entering the esophagus. The pharynx is located immediately above the epiglottis, meaning that both food and air can enter the pharynx. The epiglottis covers the trachea to prevent food from entering, and forces food to travel down the esophagus instead. After food travels through the esophagus it enters the stomach. The pyloric sphincter then separates the stomach from the small intestine.

The epiglottis is a structure that folds forward to cover the trachea when swallowing. It helps to direct food to the esophagus instead of the trachea, preventing liquids and solids from entering the lungs.

Chyme is formed during the initial breakdown of food. Food is turned into chyme in the stomach due to the combination of smooth muscle contractions and the chemical action of hydrochloric acid. These processes serve to digest the food both mechanically and chemically.

The liver produces bile, which is then stored in the gall bladder. It also stores vitamins and iron, and produces glycogen. The liver is also responsible for detoxification of several metabolites, but it does not produce insulin. Insulin secreted by the pancreas. Other functions of the liver include: synthesis of blood proteins, breakdown of lipids, recycling red blood cells, and glycogen breakdown.

The contraction and relaxation of a layer of smooth muscle at the junction of the esophagus (-esophageal) and the stomach (gastro-) allows for the bolus to pass into the stomach upon relaxation, and by contraction keeps the bolus, acid, and other stomach contents from regurgitating into the esophagus from the stomach. This sphincter is under vagus nerve control, thus, the parasympathetic nervous system.

The correct order that the food will pass as is first the duodenum, then the jejunum and finally the ileum. These are all sections or portions of the small intestine, the organ responsible for the vast majority of absorption of nutrients from food before it is passed on to the large intestine, where water, vitamins, minerals, and any other remaining nutrients are absorbed into the body.

In the stomach, both hydrochloric acid and pepsinogen are secreted by gastric pits. Parietal cells in these pits secrete hydrochloric acid while chief cells in these pits secrete pepsinogen. Note that pepsinogen is inactive, and gets activated into pepsin via hydrochloric acid.

The gallbladder is found underneath the liver. The gallbladder is the storage place of bile, which helps to emulsify fats. Bile is necessary for the digestive system to break down fat. Removal of the gallbladder can result in fat malabsorption, which can present as loose stool.