<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Discuss six fundamental activities of the digestive system, giving an example of each
  • Compare and contrast the neural and hormonal controls involved in digestion

The digestive system uses mechanical and chemical activities to break food down into absorbable substances during its journey through the digestive system. [link] provides an overview of the basic functions of the digestive organs.

Visit this site for an overview of digestion of food in different regions of the digestive tract. Note the route of non-fat nutrients from the small intestine to their release as nutrients to the body.

Functions of the Digestive Organs
Organ Major functions Other functions
Mouth
  • Ingests food
  • Chews and mixes food
  • Begins chemical breakdown of carbohydrates
  • Moves food into the pharynx
  • Begins breakdown of lipids via lingual lipase
  • Moistens and dissolves food, allowing you to taste it
  • Cleans and lubricates the teeth and oral cavity
  • Has some antimicrobial activity
Pharynx
  • Propels food from the oral cavity to the esophagus
  • Lubricates food and passageways
Esophagus
  • Propels food to the stomach
  • Lubricates food and passageways
Stomach
  • Mixes and churns food with gastric juices to form chyme
  • Begins chemical breakdown of proteins
  • Releases food into the duodenum as chyme
  • Absorbs some fat-soluble substances (for example, alcohol, aspirin)
  • Possesses antimicrobial functions
  • Stimulates protein-digesting enzymes
  • Secretes intrinsic factor required for vitamin B 12 absorption in small intestine
Small intestine
  • Mixes chyme with digestive juices
  • Propels food at a rate slow enough for digestion and absorption
  • Absorbs breakdown products of carbohydrates, proteins, lipids, and nucleic acids, along with vitamins, minerals, and water
  • Performs physical digestion via segmentation
  • Provides optimal medium for enzymatic activity
Accessory organs
  • Liver: produces bile salts, which emulsify lipids, aiding their digestion and absorption
  • Gallbladder: stores, concentrates, and releases bile
  • Pancreas: produces digestive enzymes and bicarbonate
  • Bicarbonate-rich pancreatic juices help neutralize acidic chyme and provide optimal environment for enzymatic activity
Large intestine
  • Further breaks down food residues
  • Absorbs most residual water, electrolytes, and vitamins produced by enteric bacteria
  • Propels feces toward rectum
  • Eliminates feces
  • Food residue is concentrated and temporarily stored prior to defecation
  • Mucus eases passage of feces through colon

Digestive processes

The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.

The first of these processes, ingestion    , refers to the entry of food into the alimentary canal through the mouth. There, the food is chewed and mixed with saliva, which contains enzymes that begin breaking down the carbohydrates in the food plus some lipid digestion via lingual lipase. Chewing increases the surface area of the food and allows an appropriately sized bolus to be produced.

Food leaves the mouth when the tongue and pharyngeal muscles propel it into the esophagus. This act of swallowing, the last voluntary act until defecation, is an example of propulsion    , which refers to the movement of food through the digestive tract. It includes both the voluntary process of swallowing and the involuntary process of peristalsis. Peristalsis consists of sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along ( [link] ). These waves also play a role in mixing food with digestive juices. Peristalsis is so powerful that foods and liquids you swallow enter your stomach even if you are standing on your head.

Questions & Answers

what is endocrin?
Asim Reply
why should there be an inhibition to the process of gastric production in the intestinal phase
Gloria
endocrine is a system through which the secretions of cell directly poured into blood.
Tanveer
why should there be an inhibition to the process of gastric production in the intestinal
Gloria Reply
what is a stimuli
Emily Reply
environment factor that cause a cell to respond
Quran
name the two types of melanin
Laila Reply
deference between RNA and DNA
Ali
.DNA stands for Deoxyribonucleic Acid. The sugar portion of DNA is 2-Deoxyribose.RNA stands for Ribonucleic Acid.  The sugar portion of RNA is Ribose.2.The helix geometry of DNA is of B-Form (A or Z also present).The helix geometry of RNA is of A-Form.3.DNA is a double-stranded molecule consisting o
ryaisha
DNA consists of nucleotide but RNA consists of nucleoside DNA is double standard but RNA is single standard.In DNA at the nitrogen bases adinine,guanine,cytocin and thymine is present but in case of RNA instead of thymine uracil is present.
Tanveer
what are rdna
Budumari
what is a heart
walker Reply
A heart is an organ in the circulatory system that pumps blood throughout the systemic regions
bernard
what is anatomy
Aisha
Anatomy is the study of internal and external structures and the relationship among body parts. (the study of structure).
Tomi
what is the physiology of the heart
nadine
guys help me with a pathophysiology of asthma
Luyando
asthma is a lungs related disorder in which there is difficulty in breathing due to some allergic factors, their is inflamation of alveoli of respiratory part of lungs.also decreases the surface area.
Tanveer
what is meaning of brain strock and its types?
Tanveer
the pathophysiology of asthma is complex and involves airway inflammation and bronchial hyperresponsiveness pathogenesis of asthma
Omkar
skin infection please explain
Hamza Reply
what is malignant melanoma
Akon Reply
cancerous cells 🙄
Sohan
yes benign is non-cancerous malignant is cancerous.
Joseph
that's a simple way of explaining it however you're different processes like mitosis etc a person can be at risk for developing cancer etc
Joseph
you can tell by an unusual growth of a mole, or change in size coloration with melanoma. which is abnormal growth of your squamous cells.
Joseph
Types of wandering connective tissues
Hassan Reply
what are the meaning of skin
PASHALINA Reply
study of external structure of human body is known as anatomy
VINAY Reply
what is Tau?
Vicki Reply
what is sliva
Saqlain Reply
what is gross
Kiran Reply
Describe the characteristics of tissue lining the respiratory passage way
arach Reply
please are they two types of antigens? one is foreign material and the other is a protein.... Please enlighten me cos i don't get it
shakainah Reply

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask