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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

blood is unique it is the only flueid tissue in the body
yeh
Ayoub
this is fascinating
mery
for real
Musa
what is blood
sujon Reply
lol. the red substance in your body. that circulates food nutrients and oxygen
Nii
Blood is composed of plasma and formed elements. The plasma is about 55% of blood and is about 80-90% water usually. The other 20-10% accounts for solutes such as ions, nutrients, gases, and hormones.
Carmelo
Blood is a fluid type of connective tissue and it's formed elements (cells) include RBC, WBC, and plalets.
Carmelo
what is sasamoid bone?
hafeez Reply
how many types of bone on the base of shape
hafeez
5
Husna
i want join the conversation
juwar Reply
Alright
Haya
feel free to do so
Vida
where are you from ?
Haya
hi what's up
Mar
well hello
emad
Im from kashmir,but I'm studying in punjab
Aabid
Hello
Aabid
I'm studying pharmacy at JUST University in jordan
emad
so am i emad 😅
shereen
afg
Ayoub
I am Javed Ali
Javedali
hello i am hafeez from gilgit
hafeez
explain the mechanism(release and control) of hormonal interplay for fluid and electrolyte.
Cassie Reply
There are three main ways in which hormones may be released. Humoral stimulus - occurs when their is an inbalance in electrolytes in the body. Neural stimulus - occurs when autonomic nerve fibers stimulate glands to release hormones.
Carmelo
Hormonal stimulus - occurs when a hormone causes another hormone to be released from another gland.
Carmelo
what are the main pumps found in the cell membrane
pauline Reply
calcium
Schmidt
sodium potassium pump
Husna
Differences between ligaments and catilage
joy Reply
differences between catilage and ligaments
joy
Both are different types of connective tissues. Second difference is that cartilage contains chondroblasts rather than fibroblasts. Their is also slight differences on their extracrullar matrix. For ex, cartilages tend to contain more collagen than tendons and ligaments.
Carmelo
Both types of connective tissue also function differently. Ligaments connect bone to bone, while cartilage have a variety of function like cushioning bones and giving structural support like on the nose and ears.
Carmelo
explain the causes of the refractory period of a nerve fiber
Sophia Reply
Refractory period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation. Brief pause in stimulus or excitation.
Nii
To add on, the brief pause is produced because of the event of establishing a resting membrane potential that needs to be produced before depolarization (another action potential) can occur again.
Carmelo
The refractory period also gives a chance for neurotransmitters to be replenished on the axon terminal.
Carmelo
what is hypoxia
Akas Reply
I guess it's low supply the oxygen to the tissues
famuyiwa
yup
Natalie
A condition in which tissues (especially the blood) are deprived of an adequate supply of oxygen
Panthera
hanifa pia uko hapa
Panthera
Hypoxia is the lack of oxygen concentration in the blood. Therefore, tissues will receive a low concentration of oxygen. Usually our bodies respond to Hypoxia by stimulating erythropoiesis in red bone marrow.
Carmelo
hypoxia is the lack of oxygen in blood absolutely.
hafeez
hypoxia: is a condition in wich the concentration of oxygen goes down in tissue or all over the body but the low concentration of oxygen in blood is called hypoxiemia.
Ayoub
where is present Glenoid Cavity ?
A- Reply
what is the muscular tissue
Md Reply
muscular tissue is a type of tissue that provide to help in cotraction to aur body.
A-
What's the difference in epithelial, connective, muscular and muscle tissue
Gifty
and it's similarities
Gifty
what is limb bone
Akshu Reply
this are bone attaching or joining to the axial bone.axial bone including skull,vertebrate and ribcage
Eliasi
how many bones make up the skull?
Matthew
22 bones
Husna
22bones
Bhanu
where is present Glenoid cavity ?
A-
how many bone in skull
Md
almost there are 8 bones in skull
hafeez
Explain the stages of mitosis and cell division
Bella Reply
Bella, this is a very long process to detail by text. However, to keep it brief, mitosis has four phases in order: prophase, metaphase, anaphase, and telophase which sometimes followed by cytokinesis. Note that some cells do not always do the cytokinesis phase.
Carmelo
As a result, some of the cells in the body are multinuclear (osteoclasts for ex).
Carmelo
explain further
Nana
difference between mitosis and meosis
Nana
In mitosis, two genetically exact daughter cells (somatic cells) are produced and they are diploid. In meiosis, four genetically unique cells (gametes) are produced and they are haploid.
Carmelo
Meiosis only occurs in reproductive organs. Mitosis is a type of asexual reproduction and is involved in tissue growth and regeneration(repair).
Carmelo
mitosis > Diploid to Diploid meiosis > Diploid to Haploid
Carmelo
systems of human body
Udezue Reply
define lymphatic system And give the composition of lymphatic fluid
sakshi Reply
the network of vessels through which lymphatic drains From the tissue into blood.lymph contain variety of substance like salts, glucose, proteins and fatsand water, white blood cells
Bhanu
yeah
Hassan

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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