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BTEC Applied Science biology Unit 8 learning aim C & D
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BTEC Applied Science biology Unit 8 learning aim C & D
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Unit 8: Physiology of Human Body SystemsC: Explore the physiology of the digestive system and the use of
corrective treatments for dietary-relateds diseases.
P5: Explain the role and location of organs involved in digestion.
For humans to survive they need to take nutrients from food. They achieve this by, digesting the
food both, mechanically- where food is broken physically into smaller parts- and chemically-where
food is broken into basic or microscopic units by enzymes and acids. But how does digestion
happen? Well, let’s answer that by taking a journey in the digestive system.
Our mouth
Most people think that the mouth is the beginning of our digestion, but actually digestion starts
even before we take any bite. The first thing that happens is that we smell the food, and this smell
triggers the salivary glands like the parotid gland in the mouth to produce saliva. That’s why our
mouth starts watering when we see the food we love. But when we actually start to chew our food
the amount of saliva increases. Once it's moisturised by the saliva, the teeth and tongue begin to
break down the food into smaller parts. Our saliva contains enzymes called salivary amylase that
breaks down starch. Once chewing is done the food becomes a small round blob that is also called
bolus. When we swallow our tongue passes our food into the throat and into oesophagus.
Pharynx (throat) and oesophagus
,The pharynx is a part of the digestive tract which receives our food from our tongue (mouth). The
throat delivers the food to our oesophagus that carries the food into our stomach. The oesophagus
is located near the trachea. There is an organ called epiglottis that folds over our trachea to avoid
chocking because food might get in to our trachea. Food is pushed through the oesophagus by a
sequence of smooth muscular contractions that are in the oesophagus called peristalsis.
Our stomach
Our stomach is a sac-like organ that holds food using its strong muscular walls, while the food is
being mixed with the enzymes in the stomach. The stomach receives food form oesophagus. The
enzymes that digest food are secreted by the stomach.
Small intestine
This is organ is made of jejunum ileum and duodenum. This organ is approximately 21 foot long
when spread out. With duodenum being the first portion of the organ, it is broadly responsible for
the ongoing break down process. Here the chime merges with bile from the liver, intestinal juice and
enzymes from the pancreas.
Duodenum is the first branch of our small intestine with ileum the last and longest part of the small
intestine and jejunum being in the centre of all these divisions.
, Large intestine
The large intestine is smaller than the small intestine, it is 1.5m long, but is thicker than the small
intestine in diameter. In the large intestine minerals and water are absorbed into our blood. It
ingests any products formed by the bacterial activity. The large intestine is divided into portions
The transverse colon: which crosses the abdomen
The ascending colon: which includes the cecum and the appendix and it travels up the right side of
the abdomen.
The descending colon: which travels down the left abdomen and has a heavy population of gut
bacteria and is used to hoard faeces.
The sigmoid colon- a short curving of the colon which has a muscular wall that helps in pushing
faeces into the rectum.
Liver
The liver is the biggest solid meaty organ and the biggest gland in the human body. It balances most
chemical levels in the blood and secretes a product called bile
Gall bladder: is a small bag looking organ which sits just below the liver. Bile produced by the liver is
stored in the gallbladder.
Appendix: the appendix is a thin tube which is about 4-inches long, it sits in the lower right part of
the abdomen attached to the large intestine. Its function is still unknown.
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