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Summary BTEC Applied Science Unit 8 Assignment C
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UNIT 8 ASSIGNMENT CThe Digestive System
Introduction
The digestive system is a group of organs and glands that work together to break down food into smaller
molecules that can be absorbed and used by the body. The major organs of the digestive system include
the mouth, oesophagus, stomach, small intestine, large intestine, rectum, and anus. The process of
digestion begins in the mouth, where food is broken down by chewing and mixed with saliva, which
contains enzymes that help to break down carbohydrates. From there, the food travels down the
oesophagus to the stomach, where it is mixed with stomach acid and digestive enzymes that help to break
down proteins. The partially digested food then moves into the small intestine, where it is further broken
down by enzymes secreted by the pancreas and the liver. Nutrients from the food are absorbed into the
bloodstream through the lining of the small intestine and transported to the liver for processing. The
remaining waste products then pass into the large intestine, where water and electrolytes are absorbed,
and the waste products are formed into solid faeces. The faeces are stored in the rectum until they are
eliminated from the body through the anus. The digestive system plays a vital role in maintaining the
health and wellbeing of the body by providing the nutrients necessary for growth, repair, and energy
production. It is also responsible for eliminating waste products from the body. A healthy diet, regular
exercise, and proper hydration are essential for maintaining a healthy digestive system. [1]
Functions of the digestive system:
Mouth
The mouth plays a crucial role in the process of digestion by mechanically and chemically breaking down
food into smaller pieces that can be easily digested and absorbed by the body. Mechanical digestion
begins in the mouth, where the teeth and tongue work together to chew and grind food into smaller
pieces. This increases the surface area of the food, making it easier for digestive enzymes to break it
down. The tongue also helps to move food around the mouth, mixing it with saliva and forming it into a
ball-shaped mass called a bolus. Chemical digestion also begins in the mouth, as saliva contains enzymes
that start to break down carbohydrates and fats in the food. Saliva also contains mucus, which helps to
moisten and lubricate the food, making it easier to swallow. Once the food has been sufficiently chewed
and mixed with saliva, it is swallowed and moves down the oesophagus into the stomach. From there, it
undergoes further digestion and absorption in the small and large intestine. [1,2]
The Oesophagus
The oesophagus is a muscular tube that connects the mouth to the stomach and plays an important role in
the process of digestion. Its primary function is to transport food and liquids from the mouth to the
stomach, using rhythmic muscular contractions called peristalsis. When food is swallowed, it is pushed
down the oesophagus by the coordinated contractions of the muscle layers in the oesophageal wall. The
oesophagus also has a muscular valve at its lower end called the lower oesophageal sphincter (LES),
which helps to prevent the backflow of stomach contents into the oesophagus. In addition to its
mechanical function of moving food down to the stomach, the oesophagus also secretes mucus to help
lubricate and protect its lining from the acidic contents of the stomach that may flow back into it. This
function is particularly important in preventing the development of conditions like gastroesophageal
reflux disease (GERD), where stomach acid flows back into the oesophagus, causing irritation and
inflammation. [1,2]
The Pharynx
, UNIT 8 ASSIGNMENT C
The pharynx is a muscular tube-like structure that connects the mouth to the oesophagus and the nasal
cavity to the larynx. It plays an important role in both the digestive and respiratory systems. In terms of
digestion, the pharynx serves as a passageway for food and liquids that have been swallowed, guiding
them from the mouth into the oesophagus. The pharynx is lined with muscle tissue that helps to push the
food and liquid down into the oesophagus through a series of coordinated muscular contractions called
peristalsis. The pharynx also plays a protective role in the digestive system, preventing food or liquid
from entering the nasal cavity or the lungs. When we swallow, a flap of tissue called the epiglottis closes
over the trachea, or windpipe, to prevent food or liquid from entering the lungs. [1,2]
The Stomach
The stomach is a muscular sac-like organ located between the oesophagus and the small intestine, and it
plays a vital role in the process of digestion. Its primary function is to break down the food that has been
swallowed into a liquid mixture called chyme, using a combination of mechanical and chemical digestion.
Mechanical digestion in the stomach occurs through muscular contractions that mix and churn the food
with gastric juice, which is secreted by specialized cells lining the stomach wall. These contractions help
to break down the food into smaller particles, increasing the surface area for chemical digestion to occur.
Chemical digestion in the stomach occurs through the action of enzymes and acids in the gastric juice.
The most important enzyme in the stomach is pepsin, which breaks down proteins into smaller peptides.
The stomach also secretes hydrochloric acid, which helps to activate pepsin and to create an acidic
environment that kills harmful bacteria and other microorganisms in the food. The stomach also has an
important role in regulating the rate at which the food enters the small intestine, which helps to ensure
that the digestive process is carried out efficiently. The stomach empties its contents into the small
intestine in small amounts, allowing for a steady and controlled release of chyme. The stomach plays a
crucial role in breaking down the food into smaller particles, mixing it with gastric juice, and regulating
the rate at which it enters the small intestine. This prepares the food for further digestion and absorption
in the small intestine. [1,2]
The Liver
The liver plays a crucial role in the process of digestion by producing bile, a greenish-yellow fluid that
helps to digest fats and absorb fat-soluble vitamins in the small intestine. Bile is produced in the liver and
stored in the gallbladder until it is needed to digest fat. When fat enters the small intestine, a hormone
called cholecystokinin (CCK) is released, which signals the gallbladder to contract and release bile into
the small intestine. Bile helps to break down large fat droplets into smaller droplets, making it easier for
the pancreatic lipase enzyme to break them down further into fatty acids and glycerol, which can be
absorbed by the small intestine. In addition to producing bile, the liver also has other important functions
in digestion. It stores glycogen, a form of glucose that is used to regulate blood sugar levels. When blood
sugar levels drop, the liver releases glycogen into the bloodstream, providing a source of glucose for the
body. The liver also helps to detoxify harmful substances in the body, including drugs, alcohol, and other
toxins. It does this by converting these substances into less harmful forms that can be excreted from the
body. [1,2]
The Gallbladder
The gallbladder is a small, pear-shaped organ located beneath the liver, and it plays an important role in
the process of digestion by storing and releasing bile. The gallbladder stores and concentrates bile by
absorbing water and electrolytes from it, which increases its potency and effectiveness in breaking down
fats. When the gallbladder is triggered to release bile by the hormone CCK (cholecystokinin), it contracts
and pushes the concentrated bile through the bile ducts into the small intestine. If the gallbladder is
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