Chapter 15: Digestive System

Where does absorption begin? Where does MOST of the absorption take place?

Absorption begins in the stomach. Most of the absorption takes place in the small intestine.

What do biomolecules do pepsin, salivary amylase and pancreatic lipase digest? Where do they act? At what pH do they work best?

Biomolecules for pepsin digest polypeptides. Biomolecules for salivary amylase digest carbohydrates. Biomolecules for pancreatic lipase digests triglycerides. Where they act: pepsin -> stomach; salivary amylase -> mouth; lipase -> pancreas. Salivary amylase works best at pH 7. Pepsin works best at pH 1-3 (most acidic). Lipase works best at pH 2-3.

Where does chemical digestion begin? What other organs participate in chemical digestion? Where does MOST of the chemical digestion and absorption take place?

Chemical digestion begins between the mouth and the stomach. The small intestine and the liver also participate in chemical digestion. Most of the chemical digestion and absorption take place in the small intestine.

Where does mechanical digestion begin? Which organ completes the mechanical digestion of a meal?

Mechanical digestion begins in the mouth. The small intestine completes the mechanical digestion of a meal.

Trace the path that food takes as it travels from your mouth to the anus. (Be sure to name all 3 parts of the small intestine and 3 parts of the large intestine.)

Mouth -> pharynx -> stomach -> pyloric sphincter -> duodenum -> jejunum -> ilium -> ileosecal valve -> colon -> rectum

What is pepsin? What is amylase? What is lipase?

Pepsin is a protein-splitting enzyme that the gastric gland secretes. Amylase is an enzyme that helps digest carbohydrates. Lipase is an enzyme that the body uses to break down fats in food so they can be absorbed in the intestines.

What kind of tissue lines the mouth and pharynx? What type lines the small intestine?

Stratified squamous lines the mouth and the pharynx. Simple columnar lines the small intestine.

Why do the duodenum and the pancreas secrete bicarbonate?

The duodenum and the pancreas secrete bicarbonate because they neutralize the HCl.

What is the job of the esophagus? The stomach? Small intestine? Large intestine?

The esophagus pushes food to the stomach. The stomach receives food from the esophagus, mixes with gastric juice, initiates protein digestion, and moves food to the small intestine. The small intestine completes digestion of nutrients in chyme, absorbs the products of digestion and transports the residues to the large intestine. The large intestine absorbs water and electrolytes from chyme remaining in the alimentary canal, it forms and stores feces.

What is the pH of gastric juice (gastric fluid)? What does HCl do in the process of digestion?

The pH of gastric juice is basic. In the process of digestion, HCl converts iron in food to a form that the body can use, destroys ingested bacteria and pathogens, and activates all three enzymes.

Besides medication, what is the single BEST way to lower your blood cholesterol levels? What is pectin? How does it affect blood cholesterol levels?

The single BEST way to lower your blood cholesterol levels is to have pectin. Pectin is a water-soluble found in apples, beans, etc. Adding pectin to your diet will lower your cholesterol by 3%.

Name the sphincters between the esophagus and stomach, between the stomach and duodenum, between the ileum and the large intestine.

The sphincter between the esophagus and the stomach is called the lower esophagus sphincter. The sphincter between the stomach and the duodenum is called the pyloric sphincter. The sphincter between the ileum and the large intestine is called the ileosecal sphincter.

What are the two main jobs of the large intestine?

To absorb water from the remaining indigestible food matter and transmit the useless waste material from the body

Name at least 4 distinct functions of the digestive system. Compare and contrast ingestion, digestion, absorption, and excretion. Compare and contrast mechanical digestion and chemical digestion, giving examples of both.

4 distinct functions of the digestive system: ingestion, digestion, absorption, and excretion. Ingestion is the intake of food. Digestion is the break down of nutrients into absorbable molecules. Absorption is taking the building blocks of food into cells of the body. Excretion is the process of eliminating or expelling waste matter. Mechanical digestion is when teeth tear off pieces of food and grind it together with saliva. Chemical digestion is the acid and enzymes in the stomach.

What roles does the liver play in digestion? Why is bile added to the food we are digesting? What do bile salts do? what is the job of the gallbladder? Where is the bile added?

In digestion, the liver makes bile, receives nutrients from the small gallbladder. Bile is added to the food we are digesting because it is an important part of the absorption of the fat-soluble substances, such as the vitamins A, D, E, and K. The function of bile salts in the duodenum is to solubilize ingested fat-soluble vitamins, facilitating their digestion and absorption. The gallbladder stores and concentrates bile, a yellow-brown digestive enzyme produced by the liver. Bile is added on the liver.

What is the role of intestinal villi? What is the job of the intestinal muscularis layer? What type of epithelium lines the stomach and the small intestines? What is the job of the lacteals and capillaries in the villi?

Intestinal villi play a role in digestion and are essential for the absorption of digested nutrients. The muscularis externa is responsible for segmental contractions and peristaltic movement in the GI tract. A simple columnar epithelium lines the stomach and small intestines. A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the small intestine. Capillaries bring nutrients and oxygen to tissues and remove waste products.

What is the final end product of protein digestion? Carbohydrate digestion? Fat digestion? Which are absorbed into capillaries and which are absorbed into the lacteal?

The final end product of protein digestion is amino acids. For carbohydrate digestion, the end product is single sugars (or glucose). For fat digestion, the end products are fatty acids and glycerol. Water-soluble nutrients enter the capillary blood in the villi and travel to the liver via the hepatic portal vein. Dietary fats are absorbed by lacteal.

Name the 4 regions of the stomach. What is the name of the folds in the stomach and why are they there?

The four regions of the stomach are the cardia, fundus, body, and pylorus. The name of the folds in the stomach are called rugae and they are there because they mark the stomach's inner lining and submucosal layer.

What level of blood cholesterol is considered too high? What is LDL? What is HDL?

The level of blood cholesterol that is considered too high starts at 250 mg/dl. LDL takes cholesterol to cells for membrane repair or steroid synthesis. HDL travels through blood picking up cholesterol and delivers it to the liver for disposal.

Nutrition absorbed by the capillaries of the small intestine travels first to the liver. How does that happen?

The liver converts the nutrients in our diets into substances that the body can use, stores these substances, and supplies cells with them when needed. It also takes up toxic substances and converts them into harmless substances or makes sure they are released from the body.

What is the name of the first part of the small intestine? What 3 important things happen there?

The name of the first part of the small intestine is the duodenum. The important things that happen here: receives chyme from stomach and secretions from pancreas and liver, completes digestion, and transports the residues to the large intestine.