6.1 Nutrition and the Human Digestive System Flashcards
What is Nutrition
Nutrition is the process by which organisms obtain food and energy for growth, repair and
maintenance of the body.
In humans, nutrition consists of
- Feeding or Ingestion
- Digestion
- Absorption
- Assimilation
The process of Feeding or Ingestion
Food is taken into the body
The process of Digestion
- Large food molecules are broken down into smaller, soluble molecules that
can be absorbed into the body cells. - Physical digestion: Mechanical break up of food into smaller particles.
- Chemical digestion: Breakdown of large food molecules into smaller soluble
molecules catalysed by digestive enzymes through hydrolytic reactions.
The process of Absorption
Digested food substances are absorbed into the body cells.
The process of Assimilation
Some of the absorbed food substances are converted into new protoplasm
or used to provide energy.
The mouth contains ?
- Teeth
- Salivary glands
- Tongue
What do teeth do?
Chewing action of the teeth breaks down large pieces of food into smaller
pieces. This increases the surface area of the food so enzymes can act on it
more efficiently.
what do the Salivary glands do?
- Secretes saliva into the mouth. Saliva flows into the buccal cavity via tubes
called salivary ducts.
what does the tongue do?
- Helps to mix food with saliva. Taste buds on the tongue help to identify and
select suitable foods.
Pharynx
- The pharynx is the part of the gut which connects the buccal cavity to the oesophagus and
the larynx. The pharynx also leads to the trachea. - The larynx has a slit-like opening called the glottis.
Where and What is the Oesophagus
The oesophagus or gullet is a narrow, muscular tube. It passes through the thorax and the
diaphragm to join the stomach.
what is a diaphragm
a sheet of muscle which separates the thorax from the abdomen
The wall of the oesophagus contains two layers of muscles, where are these muscles present
These muscles are present along
the whole gut from the oesophagus to the rectum.
What are the 2 sets of muscles along the oesophagus?
The two layers of muscles are:
- Longitudinal muscles, on the outer side of the gut wall
- Circular muscles, on the inner side of the gut wall.
- Both sets of muscles produce long, slow contractions that move food along the gut by
peristalsis.
What is Peristalsis
Peristalsis is the rhythmic, wave-like muscular contractions in the wall of the alimentary
canal.
Peristalsis enables… ?
Peristalsis enables food to be mixed with the digestive juices, and also pushes or propels the
food along the gut.
The circular muscles ____ the lumen whereas the longitudinal muscles ____ and
____ the lumen.
The circular muscles constrict the lumen whereas the longitudinal muscles shorten and
widen the lumen.
The circular and longitudinal muscles are ____?
The circular and longitudinal muscles are antagonistic muscles.
When the circular muscles contract, what hppens
When the circular muscles contract, the longitudinal muscles relax. As a result, the
wall of the gut constricts, and the gut becomes narrower and longer. The food is
squeezed or pushed forwards.
When the longitudinal muscles contract, what happens
When the longitudinal muscles contract, the circular muscles relax. The gut dilates,
and it becomes wider and shorter. This widens the lumen for food to enter.
What is a stomach
The stomach is a distensible muscular bag, with thick and well-developed muscular walls.
When the stomach is fully distended, what does it tell the brain?
it sends signals to the brain that it is full.
The stomach wall has numerous pits that lead to _____ that secrete _____ into
the ____ cavity.
The stomach wall has numerous pits that lead to gastric glands that secrete gastric juice into
the stomach cavity.
Where is the pyloric sphincter located
The pyloric sphincter is located at the place where the stomach joins the small intestine.
What happens when the pyloric sphincter contracts or relaxes?
When the muscle contracts, the entrance to the small intestine closes. When the ring
relaxes, the entrance opens, allowing food to pass from the stomach into the small intestine.
Liver ( physical charcateristics and purpose)
- The liver is dark red and is made up of five lobes.
- The liver secretes bile, which is stored in the gall bladder
Gall bladder purpose
- Bile is stored temporarily in high concentration in the gall bladder
- Bile flows into the duodenum via the bile duct.
Small intestine consists of?
- The small intestine consists of the U-shaped duodenum, the jejunum, and the ileum.
The wall of the small intestine is adapted to absorb____?
The wall of the small intestine is adapted to absorb digested food products and water.
The lining of the walls of the small intestine contains ____ which secrete ___?
The lining of the walls of the small intestine contains glands which secrete digestive
enzymes.
Large intestine consist of?
- It consists of the colon and the rectum.
In humans, these have no specific functions, and where are they located
At the junction between the colon and small intestine are the caecum and the appendix.
What is The main function of the colon?
absorb water and mineral salts from the undigested
food material. No digestion occurs in the large intestine.
Where is Faecal matter temporarily stored
rectum
When the rectrum contracts what happens
faeces is
expelled through the anus
