2.3 Digestive System Process

The act of your tongue and pharyngeal muscles propelling the bolus into the esophagus is known as __________ (__________).

Deglutination (swallowing).

Propulsion includes both the voluntary process of __________ and the involuntary process of __________.

Deglutination (swallowing); peristalsis.

What is the last voluntary act until defecation?

Deglutination.

The process of digestion includes six activities:

(1) Ingestion, (2) Propulsion, (3) Mechanical or physical digestion, (4) Chemical digestions, (5) Absorption, and (6) Defecation.

What is mechanical digestion?

A purely physical process (it does not change the chemical nature of the food) involving mastication, tongue movements and the mixing with saliva in the oral cavity, churning in the stomach, and segmentation in the small intestine to break food down increasing the mobility of the bolus and exposing more of its surface area to digestive juices.

What is chyme?

An acidic "soup" that results from the mixing with digestive juices of the mechanically churned food in the stomach.

What is chewing your food so important?

Chewing increases the surface area of the food and allows an appropriately-sized bolus to be produced.

What is mastication?

Chewing.

The final step of digestion is what?

Defecation.

The first of these processes, __________ refers to what?

Ingestion; refers to the entry of food into the alimentary canal through the mouth therein food is chewed and mixed with saliva containing enzymes that begin breaking down the carbohydrates in the food.

What are the functions of the large intestine?

Major functions: (1) Further breaks down food residues, (2) Absorbs most residual water, electrolytes, and vitamins produced by enteric bacteria, (3) Propels feces toward rectum, (4) Eliminates feces Other functions: (1) Food residue is concentrated and temporarily stored prior to defecation, (2) Mucus eases passage of feces through colon

What are the functions of the mouth?

Major functions: (1) Ingests food, (2) Chews and mixes food, (3) Begins chemical breakdown of carbohydrates, (4) Moves food into the pharynx, (5) Begins breakdown of lipids via lingual lipase Other functions: (1) Moistens and dissolves food allowing you to taste it, (2) Cleans and lubricates the teeth and oral cavity, (3) Has some antimicrobial activity

What are the functions of the accessory organs?

Major functions: (1) Liver - produces bile salts, which emulsify lipids, aiding their digestion and absorption; (2) Gallbladder - stores, concentrates, and releases bile; (3) Pancreas - produces digestive enzymes and bicarbonate Other functions: (1) Bicarbonate-rich pancreatic juices help neutralize acidic chyme and provide optimal environment for enzymatic activity

What are the functions of the stomach?

Major functions: (1) Mixes and churns food with gastric juices to form chyme, (2) Begins chemical breakdown of proteins, (3) Releases food into the duodenum as chyme, (4) Absorbs some fat-soluble substances (for example, alcohol, aspirin), (5) Possesses antimicrobial functions Other functions: (1) Stimulates protein-digesting enzymes, (2) Secretes intrinsic factor required for vitamin B12 absorption in the small intestine

What are the functions of the small intestine?

Major functions: (1) Mixes chyme with digestive juices, (2) Propels food at a rate slow enough for digestion and absorption, (3) Absorbs breakdown products of carbohydrates, proteins, lipids, and nucleic acids, along with vitamins, minerals and water, (4) Performs physical digestion via segmentation Other functions: (1) Provides optimal medium for enzymatic activity

What are the functions of the pharynx?

Major functions: (1) Propels food from the oral cabity to the esophagus Other functions: (1) Lubricates food and passageways

What are the functions of the esophagus?

Major functions: (1) Propels food to the stomach Other functions: (1) Lubricates food and passageways

Digestion includes both __________ and __________ processes.

Mechanical; chemical.

Chemical digestion begins in the __________ and is usually completed in the __________.

Mouth; Small intestine.

Describe the process of nutrients being absorbed into the bloodstream.

Nutrients are absorbed from the lumen of the alimentary canal into the bloodstream through the epithelial cells that make up the mucosa.

What is segmentation and where does it mainly occur?

Occurring mainly in the small intestine, it consists of localized contractions of circular muscle of the muscularis layer of the alimentary canal isolating small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents thereby mixing the food with digestive juices to facilitate absorption.

Where does absorption occur?

Primarily within the small intestine.

What is propulsion? Provide an example.

Refers to the movement of food through the digestive tract; deglutination.

What is peristalsis?

Sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles to propel food along your digestive tract.

What does defecation entail?

Undigested materials are removed from the body as feces.

Where does chemical digestion begin and what does it involve?

Starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks (for example, proteins into separate amino acids).

What does deglutination mean?

Swallowing; propelling bolus via the tongue and pharyngeal muscles into the esophagus.

After mastication and mixing the food with saliva, the food leaves the oral cavity and is propelled into the esophagus and stomach wherein what happens?

The mechanical churning of food to further break it apart and expose more of its surface area to digestive juices, creating an acidic "soup" called chyme.

What is absorption?

The process of nutrients (from the broken down foods) entering into the bloodstream.

What are the digestive secretions, used to break down food molecules, composed of?

The secretions vary, but typically contain water, various enzymes, acids, and salts.

Peristalsis also plays a role in what?

The waves of peristalsis also play a role in mixing food with digestive juices.

Food leaves the mouth when the __________ and __________ muscles propel it into the __________.

Tongue and pharyngeal; esophagus

The digestive system uses mechanical and chemical activities to break food down into __________ substances during its journey through the digestive system.

absorbable