Digestion Process in the Oral Cavity

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Questions and Answers

What is the primary function of pepsin in the stomach?

To kill bacteria

To neutralize stomach acid

To break down carbohydrates

To cleave proteins into smaller peptides (correct)

What is the pH of gastric juice?

Around 2 (correct)

Around 10

Around 12

Around 7

What is the function of mucus in the stomach?

To digest proteins

To produce stomach acid

To protect the stomach lining from gastric juice (correct)

To absorb nutrients

What is the site of enzymatic hydrolysis of ingested food in humans?

Mouth Signup and view all the answers

What is the role of chief cells in the stomach?

To secrete inactive pepsinogen Signup and view all the answers

What is the function of parietal cells in the stomach?

To secrete hydrogen and chloride ions Signup and view all the answers

What is the result of coordinated contraction and relaxation of stomach muscle?

Churning of stomach contents Signup and view all the answers

What prevents chyme from entering the esophagus and regulates its entry into the small intestine?

Sphincters Signup and view all the answers

What is the function of pepsinogen in the stomach?

Activates into pepsin to split polypeptides into amino acids Signup and view all the answers

What is the primary function of the duodenum?

Mixing of chyme with digestive juices from the pancreas, liver, and gallbladder Signup and view all the answers

What is the function of bile in digestion?

Aids in digestion and absorption of fats Signup and view all the answers

What is the function of the epithelial lining of the duodenum?

Produces several digestive enzymes Signup and view all the answers

What is the role of villi epithelial cells in the small intestine?

Absorbs fatty acids and monoglycerides and recombines them into triglycerides Signup and view all the answers

What is the function of chylomicrons in the small intestine?

Aids in digestion and absorption of fats Signup and view all the answers

What is the role of the pancreas in digestion?

Produces digestive enzymes that aid in protein digestion Signup and view all the answers

What is the function of the jejunum and ileum in the small intestine?

Absorption of nutrients and water Signup and view all the answers

What is the primary function of the gallbladder in the digestive system?

Storage of bile produced by the liver Signup and view all the answers

Which of the following statements is true about protein digestion?

Protein digestion occurs primarily in the stomach with the action of pepsin Signup and view all the answers

What is the primary function of bile in the digestive system?

Emulsification of fats to facilitate digestion Signup and view all the answers

Which of the following organs is responsible for regulating stomach acid pH?

Stomach Signup and view all the answers

What is the primary site of nutrient absorption in the digestive system?

Small intestine Signup and view all the answers

What is the primary function of gastric juices in the stomach?

Breaking down proteins into smaller peptides Signup and view all the answers

Which of the following statements is true about extracellular digestion?

It occurs outside of cells in compartments continuous with the outside of the animal's body Signup and view all the answers

What is the term for the muscular tube that extends from the mouth to the anus and is responsible for digestion and absorption?

Alimentary canal Signup and view all the answers

What is a characteristic of particle feeding?

Requires minimal effort to obtain nutrition Signup and view all the answers

What is an advantage of bulk feeding?

Provides more energy Signup and view all the answers

What is an example of modifying food supply?

Leafcutter ants growing fungus on leaves Signup and view all the answers

What is mutualism?

A relationship where both organisms benefit equally Signup and view all the answers

What is an example of traps and deception?

Angler fish using a lure to attract prey Signup and view all the answers

What is the advantage of group hunting?

Increases food capture efficiency Signup and view all the answers

What is an example of using tools and hunting?

Chimpanzees using sticks to extract termites Signup and view all the answers

What is an advantage of particle feeding for animals that need to conserve energy?

Is a more efficient way of feeding Signup and view all the answers

What is the primary difference between digestion in sponges and digestion in cnidarians and ctenophores?

Location of digestion Signup and view all the answers

Which animal group is characterized by a complete digestive system with a mouth and anus?

Bilaterian animals Signup and view all the answers

What is the primary function of the gizzard in earthworms and birds?

Mechanical digestion Signup and view all the answers

In which animal group is digestion primarily extracellular?

Cnidarians and ctenophores Signup and view all the answers

What is the primary function of coanocytes in sponges?

Capture food particles through phagocytosis Signup and view all the answers

Which of the following is a characteristic of bilaterian animals?

Bilateral symmetry Signup and view all the answers

What is the primary function of amoeboid cells in sponges?

Absorb and distribute nutrients Signup and view all the answers

Which of the following is a characteristic of cnidarians and ctenophores?

Presence of tissues and organs Signup and view all the answers

What is the result of the process of emulsification in fat absorption?

Breakdown of triglycerides into fatty acids and monoglycerides Signup and view all the answers

Where do chylomicrons travel to after being released from the lacteal?

The heart for distribution Signup and view all the answers

What is the purpose of phospholipids, cholesterol, and proteins surrounding chylomicrons?

To facilitate the transport of chylomicrons through the lacteal Signup and view all the answers

What is the primary site of fat absorption?

The small intestine Signup and view all the answers

What are fatty acids and monoglycerides recombined into after being absorbed by epithelial cells?

Triglycerides Signup and view all the answers

What is the role of hydrogen ions in the stomach?

To activate pepsinogen, converting it to pepsin Signup and view all the answers

What is the primary function of the duodenum?

To mix food with digestive materials from the pancreas, liver, and gallbladder Signup and view all the answers

What is the role of epithelial cells lining the small intestine?

To produce digestive enzymes, such as amylase and carboxy peptidase Signup and view all the answers

Which cells produce mucous in the stomach?

Mucous cells Signup and view all the answers

What is the function of the gallbladder in the digestive system?

To store bile, essential for fat digestion and absorption Signup and view all the answers

What is the primary site of protein digestion in the digestive system?

Small intestine Signup and view all the answers

What is the role of parietal cells in the stomach?

To secrete hydrochloric acid, activating pepsinogen Signup and view all the answers

What is the primary function of the stomach in the digestive system?

To break down protein molecules into smaller polypeptides Signup and view all the answers

What is the primary function of emulsification in fat absorption?

To break down triglycerides into fatty acids and monoglycerides Signup and view all the answers

What is the purpose of recombining fatty acids and monoglycerides into triglycerides in the epithelial cells?

To package fats for transport in chylomicrons Signup and view all the answers

What is the function of phospholipids, cholesterol, and proteins surrounding chylomicrons?

To protect chylomicrons from enzymatic degradation Signup and view all the answers

Where do chylomicrons eventually travel to after being released from the lacteal?

The heart for distribution to the body Signup and view all the answers

What is the primary site of fat absorption in the digestive system?

The small intestine, specifically the jejunum and ileum Signup and view all the answers

What is the primary function of the stomach's gastric pits?

To allow for the contribution of different cells to the digestion process Signup and view all the answers

Which of the following enzymes is NOT produced by the pancreas?

Pepsin Signup and view all the answers

What is the primary function of the gallbladder in the digestive system?

To store bile Signup and view all the answers

What is the pH of the stomach?

Approximately 2 Signup and view all the answers

What is the primary function of the small intestine's epithelial cells?

To produce digestive enzymes Signup and view all the answers

What is the primary function of salivary glands in the mouth?

To produce saliva containing amylase Signup and view all the answers

What is the primary function of the duodenum in the small intestine?

To mix food with digestive materials from the pancreas, liver, and gallbladder Signup and view all the answers

What is the result of the stomach's coordinated contractions?

The mixing of food with pepsin Signup and view all the answers

What is the main difference between particle feeding and bulk feeding?

Particle feeding involves collecting small particles of food, requiring little effort, but providing limited nutrition, while bulk feeding involves consuming larger food items, requiring more effort, but providing more energy. Signup and view all the answers

What is the main advantage of particle feeding?

It is more efficient for animals that need to conserve energy. Signup and view all the answers

What is an example of modifying food supply?

Leafcutter ants modifying food supply by cutting leaves and growing fungus on them. Signup and view all the answers

What is mutualism?

A type of symbiosis where both organisms benefit equally. Signup and view all the answers

What is an example of traps and deception?

All of the above. Signup and view all the answers

What is an advantage of group hunting?

All of the above. Signup and view all the answers

What is an example of using tools and hunting?

All of the above. Signup and view all the answers

What is a disadvantage of bulk feeding?

It requires investment in development of specialized body parts, such as teeth and digestive systems. Signup and view all the answers

Study Notes

The First Stage of Digestion

The first stage of digestion is mechanical and takes place in the oral cavity.
Salivary glands deliver saliva to lubricate food.
Teeth chew food into smaller particles, exposing them to salivary amylase, which initiates the breakdown of glucose polymers.
Saliva also contains mucus, a viscous mixture of water, salts, cells, and glycoproteins.
The tongue shapes food into a bolus and provides help with swallowing.
The throat, or pharynx, is the junction that opens to both the esophagus and the trachea.
The esophagus conducts food from the pharynx down to the stomach by peristalsis.
Swallowing causes the epiglottis to block entry to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract.

Digestion in the Stomach

Gastric juice has a low pH of about 2, which kills bacteria and denatures proteins.
Gastric juice is made up of hydrochloric acid (HCl) and pepsin.
Pepsin is a protease, or protein-digesting enzyme, that cleaves proteins into smaller peptides.
Parietal cells secrete hydrogen and chloride ions separately into the lumen of the stomach.
Chief cells secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in the stomach.
Mucus protects the stomach lining from gastric juice.
Coordinated contraction and relaxation of stomach muscle churn the stomach's contents.
Sphincters prevent chyme from entering the esophagus and regulate its entry into the small intestine.

Digestion in the Small Intestine

The small intestine is the longest section of the alimentary canal and is the major organ of digestion and absorption.
The first portion of the small intestine is the duodenum, where chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself.
The pancreas produces proteases trypsin and chymotrypsin that are activated in the lumen of the duodenum.
The pancreas' solution is alkaline and neutralizes the acidic chyme.
Bile aids in digestion and absorption of fats in the small intestine.
Bile is made in the liver and stored in the gallbladder.
Bile also destroys nonfunctional red blood cells.
The epithelial lining of the duodenum produces several digestive enzymes.
Enzymatic digestion is completed as peristalsis moves the chyme and digestive juices along the small intestine.
Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients and water.
Villi epithelial cells absorb fatty acids and monoglycerides and recombine them into triglycerides.
These fats are coated with phospholipids, cholesterol, and proteins to form water-soluble chylomicrons.
Chylomicrons are transported into a lacteal, a lymphatic vessel in each villus.
Lymphatic vessels deliver chylomicron-containing lymph to large veins that return blood to the heart.

Digestion Forms

There are four stages of feeding: ingestion, digestion, absorption, and elimination.
Intracellular digestion occurs when food particles are engulfed by phagocytosis, and then food vacuoles fuse with lysosomes containing hydrolytic enzymes.
Extracellular digestion occurs in compartments that are continuous with the outside of the animal's body.
Animals with simple body plans have a gastrovascular cavity that functions in both digestion and distribution of nutrients.
More complex animals have a digestive tube with two openings, a mouth and an anus, which is called a complete digestive tract or an alimentary canal.
This digestive tube can have specialized regions that carry out digestion and absorption in a stepwise fashion.

Mammalian Digestive System

The mammalian digestive system consists of an alimentary canal and accessory glands that secrete digestive juices through ducts.
Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder.

Feeding Strategies

Particle feeding: collecting small particles of food, requiring minimal effort, but providing limited nutrition.
Bulk feeding: consuming larger food items, requiring more effort, but providing more energy.

Benefits of Particle Feeding

Minimizes energy expenditure for feeding.
Efficient for animals that need to conserve energy.

Disadvantages of Bulk Feeding

Requires greater effort to find and capture larger prey.
Involves investment in specialized body parts, such as teeth and digestive systems.

Examples of Modifying Food Supply

Leafcutter ants: grow fungus on cut leaves for protein-rich food.
Aphids and ants: aphids secrete honeydew, a sweet, energy-rich substance, in exchange for protection.

Symbiosis and Mutualism

Symbiosis: a relationship where one organism benefits from another.
Mutualism: a type of symbiosis where both organisms benefit equally.

Traps and Deception

Spiders: use webs to trap prey and deception to attract prey.
Limpets: use sticky mucus trails to trap small particles.
Ant lions: create funnel traps to capture prey and suck out their juices.
Angler fish: use a lure on their dorsal fin to attract prey.

Tools and Hunting

Chimpanzees: use sticks to extract termites from their mounds.
Egyptian vultures: use rocks to crack open ostrich eggs.
Group hunting: animals hunt in groups to increase food capture efficiency.

Advantages of Group Hunting

Increases food capture efficiency.
Reduces search area for prey.
Lowers risk of predation.
Enables the "ricochet effect" for successful hunting.

Comparison of Hunting Effectiveness

Lions: 50% effective in hunting.
Hyenas: 70% effective in hunting.
Wild dogs: 90% effective in hunting.

Hunting Strategies

Lions: stalk and surprise prey.
Hyenas: chase and exhaust prey.
Wild dogs: chase and exhaust prey over long distances.

Digestive Strategies in Animals

The four stages of feeding are: ingestion, digestion, absorption, and excretion.

Sponges

Have a simple body structure, lacking tissues, organs, and organ systems.
Are filter feeders, benefiting from small particles of food already in the process of decomposition.
Use incurrent canals to bring in water with particles, and radial canals to capture food particles through phagocytosis.
Conduct intracellular digestion using enzymes, and absorb nutrients through amoeboid cells.
Eliminate wastes through exocytosis.

Cnidarians and Ctenophores

Have tissues and organs, and conduct extracellular digestion.
Ingest food through a permanent or temporary mouth.
Use enzymes released through exocytosis to digest food in the gastrovascular cavity.
Absorb nutrients through cells lining the gastrovascular cavity.
Eliminate wastes through the mouth.

Bilaterian Animals

Have bilateral symmetry and a complete digestive system with a mouth and anus.
Ingest food through the mouth, followed by digestion in a specialized compartment.
Absorb nutrients in the intestine.
Eliminate wastes through the anus.

Examples of Bilaterian Animals

Earthworms: have a complete digestive system with a mouth and anus, and use mechanical digestion in the gizzard.
Arthropods (e.g., insects): have a crop for storing food, and use enzymes for digestion.
Birds: have a crop for storing food, a gizzard for mechanical digestion, and a specialized intestine for absorption.

Mammalian Digestive System

Ingest food through the mouth, where teeth aid in mechanical digestion.
Food passes through the esophagus to the stomach, where chemical digestion with enzymes occurs.
Absorb nutrients in the small intestine.
The large intestine is involved in water absorption and waste elimination.
Eliminate wastes through the anus.

Mammalian Digestive System

Mammalian digestive system has fewer compartments compared to other vertebrates, with no crop or gizzard.
The system consists of a mouth, esophagus, stomach, and intestines for digestion, absorption, and excretion.

Mouth

Mechanical and enzymatic breakdown of food occurs in the mouth.
Salivary glands produce saliva containing amylase, which breaks down polysaccharides into smaller polysaccharides and disaccharides like maltose.
Saliva also contains mucous, water, salts, and glycoproteins, helping food glide through the esophagus and into the stomach.

Stomach

The stomach has a pH of approximately 2, due to the presence of hydrochloric acid.
Gastric pits in the stomach lining allow for the contribution of different cells to the digestion process.
Parietal cells secrete hydrogen ions and chloride ions, which combine to form hydrochloric acid.
Hydrochloric acid activates pepsinogen, converting it to pepsin, a protease that breaks down protein molecules into smaller polypeptides.
Mucous cells produce mucus, which forms a protective layer preventing digestive juices from damaging the stomach lining.
The stomach undergoes coordinated contractions, known as churning, to mix food with pepsin.

Small Intestine

The small intestine is divided into three sections: duodenum, jejunum, and ileum.
The duodenum mixes food with digestive materials from the pancreas, liver, and gallbladder.
Pancreas produces a variety of enzymes, including proteases like trypsin and chymotrypsin, which are activated in the lumen of the duodenum.
Liver produces bile, which is stored in the gallbladder and essential for fat digestion and absorption.
Epithelial cells lining the small intestine produce digestive enzymes, such as amylase and carboxy peptidase.
Jejunum and ileum are responsible for the absorption of nutrients, including fats, which are broken down into fatty acids and monoglycerides.

Fat Absorption

Fats are absorbed in the small intestine through the process of emulsification, where triglycerides are broken down into fatty acids and monoglycerides.
Fatty acids and monoglycerides are absorbed by the epithelial cells, recombined into triglycerides, and packaged into chylomicrons.
Chylomicrons are surrounded by phospholipids, cholesterol, and proteins, and migrate to the opposite end of the epithelial cells, where they are released into a lacteal, a lymphatic vessel.
The lacteal allows chylomicrons to travel to the blood, and eventually to the heart, where they are distributed to the body for use or storage in adipose tissues.

Mammalian Digestive System

Mammalian digestive system has fewer compartments compared to other vertebrates, with no crop or gizzard.
The system consists of a mouth, esophagus, stomach, and intestines for digestion, absorption, and excretion.

Mouth

Mechanical and enzymatic breakdown of food occurs in the mouth.
Salivary glands produce saliva containing amylase, which breaks down polysaccharides into smaller polysaccharides and disaccharides like maltose.
Saliva also contains mucous, water, salts, and glycoproteins, helping food glide through the esophagus and into the stomach.

Stomach

The stomach has a pH of approximately 2, due to the presence of hydrochloric acid.
Gastric pits in the stomach lining allow for the contribution of different cells to the digestion process.
Parietal cells secrete hydrogen ions and chloride ions, which combine to form hydrochloric acid.
Hydrochloric acid activates pepsinogen, converting it to pepsin, a protease that breaks down protein molecules into smaller polypeptides.
Mucous cells produce mucus, which forms a protective layer preventing digestive juices from damaging the stomach lining.
The stomach undergoes coordinated contractions, known as churning, to mix food with pepsin.

Small Intestine

The small intestine is divided into three sections: duodenum, jejunum, and ileum.
The duodenum mixes food with digestive materials from the pancreas, liver, and gallbladder.
Pancreas produces a variety of enzymes, including proteases like trypsin and chymotrypsin, which are activated in the lumen of the duodenum.
Liver produces bile, which is stored in the gallbladder and essential for fat digestion and absorption.
Epithelial cells lining the small intestine produce digestive enzymes, such as amylase and carboxy peptidase.
Jejunum and ileum are responsible for the absorption of nutrients, including fats, which are broken down into fatty acids and monoglycerides.

Fat Absorption

Fats are absorbed in the small intestine through the process of emulsification, where triglycerides are broken down into fatty acids and monoglycerides.
Fatty acids and monoglycerides are absorbed by the epithelial cells, recombined into triglycerides, and packaged into chylomicrons.
Chylomicrons are surrounded by phospholipids, cholesterol, and proteins, and migrate to the opposite end of the epithelial cells, where they are released into a lacteal, a lymphatic vessel.
The lacteal allows chylomicrons to travel to the blood, and eventually to the heart, where they are distributed to the body for use or storage in adipose tissues.

Feeding Strategies

Particle feeding: collecting small particles of food, requiring minimal effort, but providing limited nutrition.
Bulk feeding: consuming larger food items, requiring more effort, but providing more energy.

Benefits of Particle Feeding

Minimizes energy expenditure for feeding.
Efficient for animals that need to conserve energy.

Disadvantages of Bulk Feeding

Requires greater effort to find and capture larger prey.
Involves investment in specialized body parts, such as teeth and digestive systems.

Examples of Modifying Food Supply

Leafcutter ants: grow fungus on cut leaves for protein-rich food.
Aphids and ants: aphids secrete honeydew, a sweet, energy-rich substance, in exchange for protection.