Digestive System Flashcards
What are the six basic activities of the digestive system
- Ingestion of food and water
- Mechanical digestion of food
- Chemical digestion of food
- Movement of food along the alimentary canal
- Absorption of digested food and water in the blood and lymph
- Elimination of material that is not absorbed
The 2 types of digestion
Mechanical digestion
Chemical Digestion
What is mechanical digestion and what does it involve?
It is the physical breakdown of food particles.
This aim of mech digestion is to break down food into smaller pieces so that the total surface area increases, allowing more effective chemical digestion.
Involves:
- Teeth cutting, tearing and grinding the food.
- Churning action in the stomach to break down the food further.
- Gall bladder releases bile into the small intestine. Bile salts act as emulsifying agents, breaking fat down into smaller droplets.
What is Chemical digestion?
Use of chemical means to break down larger molecules into smaller molecules.
Enzymes are mainly used in this digestion as they are biological catalysts (chemicals that are able to increase the rate of a reaction without being consumed).
Enzymes throughout the digestive system:
- Saliva (mouth
- Stomach
- Small intestine
- Carbohydrates split into monosaccharides such as glucose, fructose and galactose.
- Proteins are split into peptides and amino acids.
- Lipids are split into fatty acids and glycerol.
- Nucleic acids are split into nucleotides.
Functions of the digestive system
- Ingest (receive) food
- Digest food - mechanical and chemical
- Moves the food along the gastrointestinal (GI) tract.
- Absorb food (molecules) into blood and lymph
- Egest (remove) material that are not absorbed
What is the alimentary canal?
It is a continuous tube that runs from the mouth to the anus.
The lining of this canal is the surface through which nutrients are absorbed.
What is mastication?
The process of food being chewed.
What is the chemical digestion in the mouth?
Contains mucus to lubricate the food and digestive enzyme (SALIVARY AMYLASE), this enzyme begins the chemical digestion of starch into the disaccharide maltose.
Buffers neutralise acids to prevent tooth decay.
Antibacterial chemicals kill bacteria that enter the mouth with food
What is the mechanical digestion in the mouth?
The teeth, of which there are four of.
- Four incisors - used for biting and cutting
- two canines - conical teeth used for tearing
- Four premolars
- Six molars - used for crushing and grinding food
What is a bolus?
A small rounded mass of a substance, in this case of chewed food at the moment of swallowing.
What is the Oesophagus
It is a tube that connects the pharynx to the stomach.
What muscles is the oesophagus made of?
It have a double layer of muscle consisting of:
- Circular muscle: muscle fibres arranged in a circle.
- Longitudinal Muscle: muscle fibres arranged along the length of the canal
What is an epiglottis?
It is a flap of cartilage that closes the trachea (windpipe) when swallowing.
How does the bolus move down the oesophagus?
The circular muscle contracts behind the food entering the pharynx & oesophagus.
With this contraction the constriction of the muscle move in a wave: Peristalsis.
With that movement, the food is pushed in front of it.
Throughout this adventure of the bolus, it is lubricated by the mucus in the inner lining.
What are the layers of the GI tract?
Inner layer (Mucosa)
Submucosal
Double layer of muscle ( Longitudinal and circular)
Serosa
What is the mechanical digestion of the stomach?
Waves of muscular contraction move along the stomach wall. Contracting in a variety of ways to churn the food and mix it with the stomach juices until the food converts into a thick, soupy liquid; known as chyme.
Digestion of lipids, proteins and carbohydrates
What layers does the stomach have?
1.serosa.
2.musclaris.
(An oblique muscle layer, circular and 3.longitudinal layer.)
4.submuscosa.
5.mucosa
(gastric glands, muscularis mucosa)
What is gastric juice and what is it responsible for?
It is a digestive juice that contains hydrochloric acid, mucus and digestive enzymes.
It is responsible for the chemical digestion (mainly protein digestion) in the stomach.
What is the pH of the stomach?
2-3
What is pepsin?
It is the converted enzyme from pepsinogen, becoming an active form of the enzyme.
It is able to break proteins down into shorter peptides; polypeptides. Breaks down nucleic acids DNA and RNA
Why is the internal surface of the stomach is cover by a thick layer of mucus?
This is so that nutrients are not able to be absorbed into the bloodstream, also so the stomach acids dont eat through the stomach lineing
What is the pyloric sphincter?
It’s a circular muscle constriction. This prevents contents from moving through unless being pushed by peristalsis.
- 2-8 hours, stomach contents are gradually pushed to the next area of the alimentary canal - the small intestine.
What are uclers?
Caused by bacterial infection of the stomach
- H.pylori bacteria (a bacteria that infect your stomach (wOw))
- Now cured with antibiotics
was once THOUGHT to be caused by stress
- Tried to control with antacids (corrects the acidity in the stomach)
What does the pancreas do?
It produces and secretes pancreatic juice into the small intestine, containing enzymes:
- Proteases: trypsin, chymotrypsin
- Amylase
- Lipase
Also produces buffers to neutralise the acid from the stomach.
