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Summary Unit 8 - digestive system
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Unit 8 Physiology of Human Body Systems (A1692)
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P5) explain the role and location of organs involved in digestion1)'mouth': chewing is the first site where the digestive system takes place, using lips, tongue,
and teeth.
2) They produce saliva, which contains Amylase enzymes that help to break down starch and
soften foods.
3) The oesophagus is a muscular tube that, through a mechanism known as peristalsis,
forces food down towards the stomach. It also contains mucus membrane that permits food
to travel down the oesophagus smoothly.
4) The stomach is a muscular pouch in the upper abdomen that contains epithelial cells that
create gastric fluids that contain enzymes and acids that are required in chyme. Food
normally lasts 1-3 hours at this location.
5) The pancreas is located beneath the stomach and stores hydrochloric acid, which is
utilised to aid in the digestion of a range of foods.
6) Bile is stored in the gall bladder until it is needed.
7)The tiny intestine is divided into three sections, each with its own role and task:
Duodenum: is the intestine's initial portion. A coating of mucus protects it from acids for
around 20cm.
Jejunum: is a 2.5-meter-long section of the small intestine that absorbs most nutrients.
Ileum: The intestine's terminal portion, measuring 3.6 metres in length, is where the
remaining nutrients are absorbed.
8) The purpose of the large intestine is to absorb water and electrolytes. It also has a
Caecum, which is a sac in the initial section of the intestine that produces and absorbs
vitamins and helps push faces to the rectum. which arises from the appendix and contains
many lymphoid tissues as well as bacteria that aid in the recolonization of the gut microbiota
The colon is divided into four sections of the large intestine: ascending, transverse,
descending, and sigmoid.
9) The rectum is used to excrete in the direction of the anal canal.
10) The anus is the final phase in the digestive process, and it is the opening through which
stool or faces are discharged.
11) The liver is a big gland located in the abdomen and ventral to the stomach, which refers
to the stomach's front. Many different shapes, such as hexagon-shaped liver lobules.
Hepatocytes, or liver cells, can be found inside the lobules of the liver.
Mouth
,The mouth is the first step in the digestive system, and it is here that mechanical
digestion takes place through the chewing process. Food enters the mouth and is
broken into smaller, more soluble bits by the teeth. When you chew, your tongue
pushes the food around in your mouth to make sure it is properly chewed and
covered in saliva. Saliva contains three things: mucin, which helps bind all the food
together into ball-like clumps called boluses, salivary amylase, which breaks down
starch into maltose, and salivary amylase, which keeps the meal's ph. at 7.
Oesophagus
The oesophagus is a muscular tube that contains mucus membrane that helps food to pass
smoothly down to the stomach. Peristalsis is voluntary at the top of the oesophagus, but it
becomes more involuntary and automatic as it descends. Food usually travels through the
oesophagus in 5-10 seconds.
Stomach
The stomach is a muscular pouch in the upper abdomen that contains epithelial cells that
create gastric fluids that contain enzymes and acids that are required in chyme. Food
normally lasts 1-3 hours at this location. The ph. in the stomach ranges from 1 to 4, which is
the ideal ph. for enzymes before they denature in the stomach, and there is both mechanical
and chemical digestion going on. The stomach must be lined with smooth muscle fibres that
run in three separate directions. This allows for contraction and expansion, and chemical
digestion takes place concurrently with mechanical digestion. The triglyceride fats are
normally separated into fatty acids and glycerol by gastric lipase, and the protein is then
broken down into smaller amino acids by pepsin. The stomach does not normally digest all
the food; instead, it assists in breaking down more difficult-to-digest molecules into smaller
molecules that can then be digested by the small intestine. The mixture of food and stomach
liquid is referred to as chyme.
The liver and gall bladder
Bile is a mixture of water, bile salts, cholesterol, and a pigment called bilirubin that is formed
in the liver. Bile's job is to discharge any waste products from the liver into the duodenum
and to aid digestion by releasing bile in a controlled manner. Bile salts are the primary
component used by the body to aid in the breakdown and absorption of lipids. Bile is
expelled from the body through the faces, which is why the faces are dark brown in colour.
Hepatocytes are the cells that create bile, which is then transferred through the bile ducts
into the gall bladders, where it is stored. Bile is made up of the salts employed emulsify lipids
and increase surface area, making digestion easier. The low acidic ph. is neutralised using
hydrogen carbonate ions. Bilirubin and biliverdin, which are produced when red blood cells
and cholesterol are broken down, are examples of chyme products. When fatty food enters
the duodenum, hormone signals are released, and bile enters the duodenum to begin
emulsifying the fats.
Pancreas
The exocrine and endocrine glands are in the pancreases. The exocrine component of the
chyme will release pancreatic secretions, which contain a combination of water salts and
bicarbonate, as it is gently discharged into the duodenum. The pancreatic amylase breaks
down polysaccharides like glycogen and starch into tiny sugars like maltose, maltotrise, and
glucose, which are easily absorbed. Trypsin is a protein-breaking enzyme. Lipase is a
pancreatic enzyme that digests fats to produce fatty acids and glycerol.
Small intestine
Duodenum
, This is the first segment of the gut, which is 20cm long and protected from acids by a coating
of mucus. The duodenum is where the final stage of digestion takes place, and where fats
and pancreatic fluids are emulsified. Peristalsis is a mechanism used by the duodenum to
churn the chyme, bile, and pancreatic fluids mixture and keep it going down the intestine.
Jejunum
This 2.5-meter-long section of the small intestine is where most nutrients are absorbed.
When the meal enters the jejunum, it goes through a process known as segmentation, which
mixes it up. Because of its many folds, the jejunum has a large surface area, and epithelial
cells are also covered in many folds known as micro villi. The nutrients are absorbed through
a capillary that runs through the villi. The jejunum has a large surface area for nutrient
absorption in general.
Ileum
It is around 3.6 metres long, with walls that are thinner and more folded than jejunum and
millions of villi. Villi increase the surface area available for molecule absorption. Microvilli
are located on the surface of the villi, which enhance the surface area even further. Villi have
a plentiful supply of blood. As a result, the products of digestion are swiftly removed from
the bloodstream, increasing concentration gradients. Because the villi have a very thin
membrane, the diffusion path is short. The PH of the ileum is neutral to slightly alkaline,
ranging from 7 to 8. The mesentery is a membrane that supports the jejunum and ileum.
The large intestine
The large intestine is the final section of the digestive tract, measuring 6-7 cm in diameter
and 1.5 metres in length. The purpose of the large intestine is to absorb and recycle water,
transform chyme to faces, and absorb vitamins. The large intestine has the largest bacterial
concentration in the body. Their job is to excrete a variety of vitamins. Over a period of
several hours, the chyme is pushed slowly along the gut, using the peristalsis process once
more. While the chyme flows, bacteria use a process called fermentation to breakdown the
components that are not normally digestible. All-important vitamins are digested; however,
vitamin K is only produced by gut bacteria and is required for normal blood clotting. The
large intestine's ability to absorb water is a critical aspect in the solidification of faeces. The
colon is divided into four sections of the large intestine: ascending, transverse, descending,
and sigmoid. The colon mucosa has columnar epithelial cells with no valleys or folds and few
to no digestive enzyme secreting cells. In the epithelial cell, there are many goblet cells that
help make mucus that protects the wall from acids and gases created by bacteria that live
there.
Rectum
Faecal matter that has been dried and preserved in the rectum after being formed in the
large intestine. The rectum is a muscular tube with a diameter of 20 cm and a width of 6-7
cm. The mucus produced in the colon's goblet cells is lubricating and aids in the passage of
faeces to the rectum and anal canal. Gut bacteria in the large intestine are vital for human
well-being because they aid in the production of vitamin B and K, as well as certain appetite-
regulating hormones. Water is also absorbed in the colon from undigested meals. Faces
move into the rectum with undigested fibre bacteria, gut epithelium cells, and products like
bilirubin and biliverdin. More water is absorbed, and the faces are discharged through the
anal canal.
Anus
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