PLTW HBS Digestive System

Four functions of the digestive system

Absorption/secretion

Elimination of waste

Digestion (chemical and mechanical)

Ingestion (bringing food into the body)

What is the difference between pyloric sphincter vs the lower esophageal sphincter?

Pyloric sphincter: goes from the stomach to the duodenum, lets chyme into the duodenum

Lower esophageal sphincter: lets bolus into the stomach

What happens if the lower esophageal sphincter doesn't worK?

Heartburn! Chyme goes back up the esophagus, the barrier is broken and food goes down the wrong track.

Where do enzymes come from? What do they break down?

Salivary amylase comes from the salivary glands and it breaks down food in the mouth with saliva.

Pancreatic amylase comes from the pancreas, and it breaks down carbohydrates into glucose, a monosaccharide, to be digested.

How are proteins digested?

Oral cavity: mechanical (to increase surface area)

Stomach: mechanical (3 muscle layers), chemical (HCl activates pepsin to break protein into peptide bonds)

Duodenum: protease from the pancreas and peptidases turn protein into amino acids

How are carbs digested?

Oral cavity: mechanical (to increase surface area) chemical (salivary amylase)

Stomach: mechanical (3 muscle layers), no chemical

Duodenum: amylase released from the pancreas turns maltose (disaccharide) into maltose which is two units of glucose. Maltase is embedded in the villi of the small intestine, and glucose is absorbed through the blood stream.

How does a high fiber diet help the body?

Prevents colon cancer, lowers cholesterol, and regulates blood sugar

How is fiber digested?

Oral cavity: mechanical (to increase surface area), no chemical

Stomach: mechanical (3 muscle layers)

Duodenum: none

Large intestine: bacteria breaks down fiber with specific enzymes, produces biotin and vitamin k

How is fat digested?

Oral cavity: mechanical (to increase surface area)

Stomach: mechanical (3 muscle layers), no chemical

Duodenum: bile emulsifies (dissolves into one solution) the fat to be broken down by lipase, fat is then absorbed via the lymphatic system in the smooth e.r.

What is the oral cavity and what does it contain?

3 parts- naso (nose), oro (mouth), larango (throat)

Includes lips, tongue, uvula, hard and soft palate, salivary glands (not technically but function and secrete into oral cavity)

What is the function of the salivary glands? What is the function of this?

Releases saliva! Saliva moistens food, contains amylase to break down food, is a natural painkiller, contains lysosomes to kills bacteria

What is the function of the tongue?

It is used for mechanical digestion and pushes food to keep it flowing in the right direction

What is a bolus?

It is what food becomes after being broken down. It is basically a glob of food and saliva.

Where are the hard and soft palates? Functions?

Hard palate: located in the beginning of the roof of the mouth, blocks food from nasal cavity, supported by bone

Soft palate: back of the roof of the mouth, blocks food from going into the nasal cavity, supported not by bone

What mechanical and chemical digestion occurs in the oral cavity?

Mechanical- teeth, physical breakdown of food, chomping/smashing

Chemical- amylase, saliva mixes with food, chemical breakdown of food

What mechanisms are in place to make sure food does not go down the wrong pipe and into the windpipe?

Epiglottis is a little flap that prevents food from going to the trachea, prevents from choking

What is peristaltic movement and how does it function in the esophagus?

A muscle function that pushes food down esophagus and in the right direction. Reverse peristaltic is throwing up.

Does any digestion of food occur in the esophagus?

NO! Most is in the stomach

What are the primary functions of the stomach?

Mechanical digestion- 3 layers of muscle

Chemical digestion- only with proteins!

What is chyme and how does the stomach mix this material?

Chyme is a mix of food, saliva, and gastric juices (alkaline mucus, HCl to neutralize, pepsin)

What role does the stomach play in decontaminating the incoming food matter?

It releases enzymes that kill bacteria and balance pH

What cells in the stomach function to form enzymes and acids?

Chief cells (HCl activates the pepside bonds to break into amino acids within the protein digestion), alkaline mucus cells, and parietal cells.

Why doesn't gastric juice digest the inside of the stomach?

Because the stomach is protected by mucus neck cells.

What are sphincters and how are they related to the stomach?

Sphincters are smooth muscles located at the beginning and end of your stomach. These help push food in the right direction from the esophagus to the stomach and from the stomach to the small intestine.

What mechanical and chemical digestion occurs in the stomach?

Mechanical: stomach contracts to break down

Chemical: stomach acid

What are the three sections of the small intestine and what role does each section play in digestion or absorption?

What is the pH within the small intestine and how is this pH maintained?

The pH is 3, so very acidic. Bicarbonate, a base, is released from the pancreas to raise the pH of the acidic chyme

Where do bile and pancreatic enzymes enter the small intestine?

Through the duodenum

How does food move through the intestines?

Peristaltic movement contracts and restricts to allow food to flow through the intestines.

What enzymes act inside the small intestine and what are the functions of these enzymes?

Lipase-lipids

Protease-proteins

Amylase-carbohydrates

Nucleases-nucleic acids

What is the function of the large intestine in relation to digestion?

Absorbs water, electrolytes, and minerals through bacteria (no enzymes)

What are the three sections of the large intestine and what roles does each play in digestion or absorption?

Ascending colon-

Transverse colon-

Descending colon-

How does the large intestine help maintain a water balance in the body?

Mucus helps with secretion and absorption.

What is the size of the pancreas and where is it located?

It is about 6 inches long and is behind the stomach

What are the different functions of the pancreas, and how is it directly related to digestion?

Works through chemical digestion since it houses enzymes and bicarbonate ions to neutralize the chyme.

How does the pancreas connect to the rest of the digestive system?

Ducts to the duodenum (leads and secretes)

What enzymes are produced by the pancreas and what are their functions?

Lipase-lipids

Protease-proteins

Amylase-carbohydrates

Nucleases-nucleic acids

How is insulin related to the digestive system?

Insulin is released from the pancreas to lower glucose levels and glucagon is released to raise glucose levels.

What is the size of the liver and where is it located?

It is about the size of a football and located in the upper right portion of the abdomen

How does the liver function in relation to digestion?

It secretes bile

What are other functions of the liver in the body?

Detoxifies, energize, and metabolize

What is the relationship between the liver and the gallbladder?

The liver makes it and the gallbladder stores it

What is the function of bile and where does it enter the digestive tract?

Bile emulsifies fat so it can be dissolved into on single solution to be dissolved, made from cholesterol