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Nutrition in humans - Coggle Diagram
Nutrition in humans
Nutrition and human digestive system
What is nutrition?
the process by which organisms obtain food and energy for growth, repair and maintenance
processes of nutrition
feeding or ingestion
Digestion
absorption
assimilation
Human digestive system
alimentary canal
9 metres
Mouth and buccal cavity
Parts of the mouth
teeth
salivary glands
tongue
pharynx
connects to the buccal cavity to the oesophagus and the larynx
leads to trachea
by slit like opening called the glottis
leads to the lungs
oesophagus / gullet
narrow muscular tube
passes through thorax and the diaphragm to join the stomach
has 2 layers of muscles
longitudinal muscles
outer side of the gut wall
circular muscles
inner side of gut wall
produce long and slow contractions to push food along the gut via peristalsis
A sheet of muscle that separates the thorax from the abdomen
plays a part in breathing
peristalsis
rhythmic, wave-like muscular contractions in the wall of the alimentary canal
enables food to be mixed with the digestive juices, and also pushes or propels the food along the gut
circular muscles constrict the lumen whereas the longitudinal muscles shorten and widen the lumen
circular and longitudinal muscles are antagonistic muscles
one set of muscles contracts while another relaxes
when the longitudinal muscles contract,
the circular muscles relax. The gut dilates, that is, it becomes wider and shorter. This widens the lumen for the food to enter.
when the circular muscles contract,
longitudinal muscles relaxes and thus the wall of the gut constricts, that is, the gut becomes narrower and longer.
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stomach
distensible (it can be stretched or expanded) muscular bag
thick and well developed muscular walls
when the stomach is fully distended,
it sends signal to the brain that it is full or sated.
stomach walls have numerous pits
this pits leads to gastric glands that secrete gastric juice into the stomach cavity
gastric juice plays an important part in digestion
stomach can store food for hours
ring of muscle called the pyloric sphincter
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located at the place where the stomach joins the small intestine
when this ring 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.
the small intestine
consists of the U shaped duodenum, the jejunum, and the much coiled ileum.
lining on the walls of the small intestine contains glands which secrete digestive enzymes
the wall is also adapted to absorb digested food products and water
6 metres long
large intestine
1.5 metres long but broader than the small intestine
consists of
colon
rectum
faeces are temporarily stored in the rectum
when the rectum contracts, the faeces are expelled through the anus
between the colon and small intestine
appendix
attached to the caecum
caecum
sac-like structure
main function
absorb water and mineral salts from the undigested food material
no digestion occurs here
organs associated with the gut
pancreas
is a gland connected to the duodenum by the pancreatic duct
bile duct joins the pancreatic duct just before the pancreatic duct opens into the duodenum
produces pancreatic juice
contains digestive juices
secretes the hormones insulin and glucagon
play an important role in controlling the concentration of glucose in the blood and carbohydrate metabolism
liver
dark red
5 lobes
3 on the right
2 on the left
attached to the lower surface,
3 blood vessels
secretes bile
bile is an alkaline greenish-yellow liquid containing bile salts and bile pigments
the bile pigments is what gives bile its colour
the pigments are waste products and are removed with the faeces or undigested matter
gall bladder