Essay
Unit 8C: Physiology of the digestive system
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Part C of Unit 8. Essay about the parts and functions of the digestive system. (Distinction Level)
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Unit 8C - The digestive systemPass Criteria
The digestive system is responsible for breaking down food into nutrients and energy that
the body uses to grow and repair. For this reason, the healthy function of the digestive
system is important for the body’s maintenance. The human digestive system is composed
of the digestive tract. The digestive tract are organs linked by a tube from the mouth to the
anus and consists of the mouth, pharynx, oesophagus, stomach, small intestine and large
intestine, liver and gallbladder, pancreas, rectum and anus (both part of the large
intestine).
Mouth
Food enters the body for digestion through the mouth. The mouth contains parts that help
breakdown the food, these parts consist of tongue, teeth and salivary glands. There are
three sets of these glands that activate from stimuli like seeing or smelling pasta to release
saliva which softens and moistens the food. The saliva also helps lubricate the food as it
passes down the pharynx, through to the oesophagus. The teeth are made of a substance
called dentin and covered in a layer called the enamel (which is the hardest substance in the
body). In the teeth there is a soft area known as the pulp located under the dentin, this area
contains the blood vessels and nerves in teeth. There are 32 teeth in the mouth separated
into 2 sets, a top set and a bottom set. Their function is to grind (or chew) the food into
smaller pieces for the saliva to further soften down. The tongue is a small muscular organ,
covered in a bumpy layer. It is located at the bottom of the mouth, in the middle of both
sets of the teeth. These bumps that cover the tongue are made of papillae, that help the
tongue grip food, pushing it down at the rear of the mouth to swallow. Sitting on top of the
papillae are taste buds. The taste buds can detect flavour molecules in the food and send
signals to the brain, creating a taste sensation.
Pharynx
The pharynx or throat is a tube that extends from the nasal cavity down to the larynx and
oesophagus. It is where the softened, chewed food passes down to get to the oesophagus
and eventually to the stomach. As well as passing down food, air passes down the nose
through the pharynx then to the larynx, eventually reaching the lungs, making it a vital part
for both the digestive and respiratory system. Due to it having two functions, a flap of tissue
called the epiglottis directs the food to the oesophagus and the air to the larynx.
Oesophagus
The oesophagus is a hollow and muscular tube. Its main function is to carry food and liquid
from the mouth to the stomach to be digested. It goes through the mediastinum, which is
the centre of the thoracic (chest) cavity and has two sphincters, upper and lower
oesophageal sphincters (UES and LES) which can control opening and closing. The UES can
be controlled involuntary and voluntary. It prevents food and liquid from entering the
windpipe. It also be opened for burping, swallowing and vomiting. The LES cannot be
controlled voluntarily (consciously). It prevents stomach acids from travelling up the
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