Unit 8C - Nutrition and Health
Aim
Explore the physiology of the digestive system and the use of corrective treatments for dietary-related
diseases.
Introduction
Within the digestive system, it includes the digestive tract along with its necessary accessory organs, which in
turn process food into molecules that can be absorbed and is also utilized by the cells found in the body[1].
Food is then broken down into smaller portions, bit by bit until all of these molecules are minuscule enough to
be absorbed and any waste products to be eliminated from the body (going to the toilet). The digestive tract
itself is also called the alimentary canal or even the gastrointestinal tract; this canal consists of a very long and
continuous tube that extends from the mouth all the way to the anus. All of this includes the mouth, pharynx,
oesophagus, stomach, small intestine as well as the large intestine. Another accessory structure of the mouth
is both the tongue and teeth. The major accessory organs for the role of digestion are the salivary glands, liver,
gallbladder and pancreas (these organs are known to secrete fluids into the digestive tract). Food that goes
into the body will undergo three types of processes for digestion; digestion, absorption and elimination. Both
digestion and absorption occur in the digestive tract. Once the nutrients have been absorbed, they are now
available to all cells in the body which are then utilized by the body cells in metabolism[2].
The digestive system will prepare nutrients for utilization by body cells through six activities, or functions;
ingestion, mechanical digestion, chemical digestion, movements, absorption and elimination. The first activity
of the digestive system is to take found through the mouth, this has to take place before anything else
happens[3]. The second process is mechanical digestion, this is when large pieces of food have been ingested
must be broken down into smaller particles which can then be acted upon by the various amounts of enzymes
(this begins in the mouth with chewing and then continues into churning and mixing actions within the
stomach). The third action is chemical digestion; the complex molecules of carbohydrates, proteins and fats
are transformed by chemical digestion into smaller molecules that can be absorbed and utilized by the cells.
This process is called hydrolysis, which uses water and digestive enzymes that break down the multiplex
molecules. These digestive enzymes will help speed up the hydrolysis process, which is usually a very slow
process.
Movements are the fourth action that takes place; after ingestion and chewing, the food particles travel from
the mouth into the pharynx, which turns into the oesophagus (this movement is known as swallowing or even
deglutition). The mixing actions that occur in the stomach are a result of smooth muscle contraction. Due to the
repetitive movements they usually occur in smaller segments of the digestive tract and mix the food particles
with enzymes and other fluids[4]. The movements that propel the food particles through the digestive tract are
called peristalsis. These are rhythmic waves of contractions that move the food particles through the various
regions in which mechanical and chemical digestion takes place. The fifth movement is absorption which is the
simple molecules that come from chemical digestion that pass through the cell membranes, of the lining in the
small intestine into the blood or lymph capillaries. The final process is called elimination; once all the food has
been digested or absorbed it needs to be eliminated from inside the body of indigestible waste through one’s
anus, faeces (defecation).
Functions of the digestive system
The digestive system is a system in the human body that contain various organs that work to break down food
into smaller molecules which can then be absorbed through the small intestines into the bloodstream to
provide nutrients for the body’s cells. These digestive organs will work to mechanically break down food
making it much easier for the digestive enzymes to access all of the food molecules. Different enzymes that
are specific to particular substrates carry out the chemical digestion of food. The process of digestion has
different stages; the first stage starts in the mouth.
Mouth
In the human anatomy, the mouth consists of two different regions: the vestibule and the oral cavity proper[5].
The vestibule is the area located between the teeth, lips and cheek, whereas the oral cavity is bounded at the
,sides and in front by the alveolar process and right at the back beside the isthmus of the fauces. The roof of
the mouth is formed by the hard palate at the front, as well as the soft palate located towards the back. What is
known as the uvula, made of soft tissue, which hangs from the soft palate towards the back; this moves up
with the soft tissue during swallowing to close the nasopharynx preventing food or liquid that is being
swallowed from passing into the nasal cavity. The bottom is made up of mylohyoid muscles as well as being
occupied mainly by the tongue. Lines on the side; under the surface of the tongue to the gums and the lining of
the inner jaw is the oral mucosa (also known as the mucous membrane). This collects secretions from the
submandibular and sublingual salivary glands. On the tongue are taste buds are specialized epithelial cells
called gustatory cells and basal cells which allow one to be able to sense the taste of food. Digestion starts in
the mouth; the teeth break down food into small particles and the tongue helps mix the food with saliva to
make it easier to swallow. Saliva contains the enzyme salivary amylase which starts the chemical digestion of
starch.
When forming a line between the upper and lower lip as well as closing and opening the mouth, the lips are a
critical part of the mouth; facial expression is a big aspect of this anatomy, an up-open parabola is a smile and
a down-open parabola is a frown. A down-turned mouth means a mouth line forming a down-turned parabola,
and when permanent can be normal. Also, a down-turned mouth can be part of the presentation of Prader-Willi
syndrome[6]. Another aspect of the mouth is the teeth as well as the periodontium, which is the tissue that
supports the teeth, that are supplied by the maxillary and mandibular nerves. The upper maxillary teeth and
their associated periodontal ligament are supplied by the superior alveolar nerves, branches of the maxillary
division, named the posterior superior alveolar nerve, anterior superior alveolar nerve, and the variably present
middle superior alveolar nerve[7]. All of these nerves create the superior dental plexus which is above the
maxillary teeth. The lower mandibular teeth and their associated periodontal ligament are supplied by the
inferior alveolar nerve, a branch of the mandibular division. This nerve lines inside the mandible, inside of the
inferior alveolar canal below the mandibular teeth, giving off branches to all the lower teeth (inferior dental
plexus)[8]. The mouth plays a very vital role in the anatomy of eating, drink, speaking etc. Usually, the act of
breathing out of the mouth is known as mouth breathing, if there is an obstruction when it comes to breathing
through the nose (which is the designated breathing organ for the human body[9].
Pharynx
The pharynx is part of the digestive system as well as the conducting zone for the respiration system. The
conducting system includes the nostrils of the nose and the larynx, trachea, bronchioles and bronchi- they
filter, warm and moistens are, conducts into the lungs[10]. The human pharynx is divided into three different
sections, which are the nasopharynx, the oropharynx and the laryngopharynx (these regions are important for
vocalization). The pharynx is a 4-5-inch-long semi-circular fibromuscular tube which is the joining of the nose
and the mouth to the oesophagus. The larynx allows the passage of swallowed solids and liquids. There are
no enzymes in the pharynx. The upper sections of the pharynx, the nasopharynx stretches between the base
of the skull towards the upper surface of the soft palate[11]; this includes the space located between the internal
nares and soft palates that lie up onto the oral cavity. The adenoids (also known as the pharyngeal tonsils) are
a type of lymphoid tissue structure found in the posterior wall of the nasopharynx. What is known as
Waldeyer’s tonsillar ring is an annular arrangement of the lymphoid tissue in both the nasopharynx and in the
oropharynx, the nasopharynx is in line with the respiratory epithelium that is columnar and ciliated.
Mucus is something that can greatly obstruct the nasopharynx; it can congest due to the upper respiratory
infection. Connecting from the middle of the ear towards the pharynx is the auditory tube; it opens into the
nasopharynx as the pharyngeal opening of this tube. The opening and closing of these tubes serve as a way
to equalize the pressure that can be felt in the middle ear with that of ambient atmospheric pressure. The
anterior aspect of the nasopharynx communicates with and through the choanae with its nasal cavities. On the
opposite side of the wall is the pharyngeal opening of the auditory tube, which to some degree is triangular in
shape, held behind firm importance which is the torus tuberous, caused by the medial end of the locating
cartilage of the tube which elevates the mucous membrane. The pharynx moves food from the mouth to the
oesophagus, it can also move air from the nasal or oral cavity to the larynx. In human speech, the pharyngeal
consonants are articulated here.
, Oesophagus
The walls of the oesophagus from its lumen consists of things such as mucosa membrane, submucosa (which
is a type of connective tissues), the layer of muscle fibres as well as a layer of fibrous connective and outer
layer of tissues. The mucosa itself is a stratified squamous epithelium, consisting of three separate layers of
squamous cells, which aid in contracting the single layer of columnar cells of the human’s stomach. Most of
the muscle is smooth muscle although striated muscle predominates in its upper third. It has two muscular
rings on its wall, one towards the top and one towards the bottom. The lower ring helps to prevent reflux of
acidic stomach content. The oesophagus has a rich blood supply and venous drainage. Its smooth muscle is
innervated by involuntary nerves (sympathetic nerves via the sympathetic trunk and parasympathetic nerves
via the vagus nerve) and in addition, voluntary nerves (lower motor neurons) which are carried in the vagus
nerve to innervate its striated muscle.
The oesophagus is one of the upper sections of the digestive system, having a multitude of taste buds on its
upper section[12]. It begins at the back of the mouth, passing downwards through the rear part of the
mediastinum, through the diaphragm, and into the stomach. In humans, the oesophagus generally starts at the
level of the sixth cervical vertebra right behind the cricoid cartilage of the trachea, entering the diaphragm at
about the level of the tenth thoracic vertebra, and ends at the cardia of the stomach, at the level of the
eleventh thoracic vertebra[13]. The oesophagus is usually about 25 cm in length[14]. There are many blood
vessels that are used in the oesophagus along with blood supply varying along its path, the upper sections of
the oesophagus and the upper oesophageal sphincter receive all its blood supply from the inferior thyroid
artery[15]. The drainage also differs along the course of the oesophagus. All of this occurs in both the upper and
middle parts of the oesophagus that then drains into the azygos and veins, and blood from the lower part
drains into the left gastric vein. All these veins will then begin to drain into the superior vena cava, with the
exception of the left gastric vein, which is a branch of the portal vein. Lymphatically, the upper third of the
oesophagus drains into the deep cervical lymph nodes, the middle into the superior and posterior mediastinal
lymph nodes, and the lower oesophagus into the gastric and celiac lymph nodes. This is similar to the
lymphatic drainage of the abdominal structures that arise from the foregut, which all drain into the celiac
nodes[16].
Food is taken and ingested through the mouth which is then swallowed, passing first into the pharynx and then
into the oesophagus. The oesophagus is then one of the first components of the digestive system as well as
the gastrointestinal tract. After the food has been ingested, food passes through the oesophagus, it enters the
stomach[17]. When food is then being swallowed, the epiglottis ( leaf-shaped flap in the throat that prevents
food from entering the windpipe and the lungs) moves backwards to cover the larynx, preventing food from
entering the trachea. At the same time, the upper oesophagal sphincter relaxes, allowing a bolus of food to
enter. Peristaltic contractions of the oesophagal muscle push the food down the oesophagus. These rhythmic
contractions occur both as a reflex response to the food that is in the mouth and also as a response to the
sensation of food within the oesophagus itself. Along with peristalsis, the lower oesophagal sphincter
relaxes[18].
Stomach
In the human anatomy and many other animals (including several invertebrates), the stomach is a hollow
organ in the gastrointestinal tract. The stomach has many functions and developed structure as it is a vital role
in digestion, as it is an important digestive organ; In the digestive system, the stomach is involved in the
second phase of digestion, which is after chewing. It performs a chemical breakdown by the enzymes and
hydrochloric acid present. In the human digestive system, a bolus (a small ball of chewed up food) enters the
stomach through the oesophagus from the lower oesophagal sphincter. The stomach releases proteases,
which are a type of protein-digesting enzyme (pepsin) and as mentioned earlier hydrochloric acid. The role of
these enzymes is to kill any bacteria that may be present as well as the providing acidic pHs of 2 for any of the
proteases to work. Food is churned by the stomach through muscular contractions of the wall called
peristalsis; reducing the volume of the bolus, before looping around the fundus[19] and the body of the stomach
as the boluses are converted into partially digested food. This digested slowly passes through the pyloric
sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins. The gastric
Aim
Explore the physiology of the digestive system and the use of corrective treatments for dietary-related
diseases.
Introduction
Within the digestive system, it includes the digestive tract along with its necessary accessory organs, which in
turn process food into molecules that can be absorbed and is also utilized by the cells found in the body[1].
Food is then broken down into smaller portions, bit by bit until all of these molecules are minuscule enough to
be absorbed and any waste products to be eliminated from the body (going to the toilet). The digestive tract
itself is also called the alimentary canal or even the gastrointestinal tract; this canal consists of a very long and
continuous tube that extends from the mouth all the way to the anus. All of this includes the mouth, pharynx,
oesophagus, stomach, small intestine as well as the large intestine. Another accessory structure of the mouth
is both the tongue and teeth. The major accessory organs for the role of digestion are the salivary glands, liver,
gallbladder and pancreas (these organs are known to secrete fluids into the digestive tract). Food that goes
into the body will undergo three types of processes for digestion; digestion, absorption and elimination. Both
digestion and absorption occur in the digestive tract. Once the nutrients have been absorbed, they are now
available to all cells in the body which are then utilized by the body cells in metabolism[2].
The digestive system will prepare nutrients for utilization by body cells through six activities, or functions;
ingestion, mechanical digestion, chemical digestion, movements, absorption and elimination. The first activity
of the digestive system is to take found through the mouth, this has to take place before anything else
happens[3]. The second process is mechanical digestion, this is when large pieces of food have been ingested
must be broken down into smaller particles which can then be acted upon by the various amounts of enzymes
(this begins in the mouth with chewing and then continues into churning and mixing actions within the
stomach). The third action is chemical digestion; the complex molecules of carbohydrates, proteins and fats
are transformed by chemical digestion into smaller molecules that can be absorbed and utilized by the cells.
This process is called hydrolysis, which uses water and digestive enzymes that break down the multiplex
molecules. These digestive enzymes will help speed up the hydrolysis process, which is usually a very slow
process.
Movements are the fourth action that takes place; after ingestion and chewing, the food particles travel from
the mouth into the pharynx, which turns into the oesophagus (this movement is known as swallowing or even
deglutition). The mixing actions that occur in the stomach are a result of smooth muscle contraction. Due to the
repetitive movements they usually occur in smaller segments of the digestive tract and mix the food particles
with enzymes and other fluids[4]. The movements that propel the food particles through the digestive tract are
called peristalsis. These are rhythmic waves of contractions that move the food particles through the various
regions in which mechanical and chemical digestion takes place. The fifth movement is absorption which is the
simple molecules that come from chemical digestion that pass through the cell membranes, of the lining in the
small intestine into the blood or lymph capillaries. The final process is called elimination; once all the food has
been digested or absorbed it needs to be eliminated from inside the body of indigestible waste through one’s
anus, faeces (defecation).
Functions of the digestive system
The digestive system is a system in the human body that contain various organs that work to break down food
into smaller molecules which can then be absorbed through the small intestines into the bloodstream to
provide nutrients for the body’s cells. These digestive organs will work to mechanically break down food
making it much easier for the digestive enzymes to access all of the food molecules. Different enzymes that
are specific to particular substrates carry out the chemical digestion of food. The process of digestion has
different stages; the first stage starts in the mouth.
Mouth
In the human anatomy, the mouth consists of two different regions: the vestibule and the oral cavity proper[5].
The vestibule is the area located between the teeth, lips and cheek, whereas the oral cavity is bounded at the
,sides and in front by the alveolar process and right at the back beside the isthmus of the fauces. The roof of
the mouth is formed by the hard palate at the front, as well as the soft palate located towards the back. What is
known as the uvula, made of soft tissue, which hangs from the soft palate towards the back; this moves up
with the soft tissue during swallowing to close the nasopharynx preventing food or liquid that is being
swallowed from passing into the nasal cavity. The bottom is made up of mylohyoid muscles as well as being
occupied mainly by the tongue. Lines on the side; under the surface of the tongue to the gums and the lining of
the inner jaw is the oral mucosa (also known as the mucous membrane). This collects secretions from the
submandibular and sublingual salivary glands. On the tongue are taste buds are specialized epithelial cells
called gustatory cells and basal cells which allow one to be able to sense the taste of food. Digestion starts in
the mouth; the teeth break down food into small particles and the tongue helps mix the food with saliva to
make it easier to swallow. Saliva contains the enzyme salivary amylase which starts the chemical digestion of
starch.
When forming a line between the upper and lower lip as well as closing and opening the mouth, the lips are a
critical part of the mouth; facial expression is a big aspect of this anatomy, an up-open parabola is a smile and
a down-open parabola is a frown. A down-turned mouth means a mouth line forming a down-turned parabola,
and when permanent can be normal. Also, a down-turned mouth can be part of the presentation of Prader-Willi
syndrome[6]. Another aspect of the mouth is the teeth as well as the periodontium, which is the tissue that
supports the teeth, that are supplied by the maxillary and mandibular nerves. The upper maxillary teeth and
their associated periodontal ligament are supplied by the superior alveolar nerves, branches of the maxillary
division, named the posterior superior alveolar nerve, anterior superior alveolar nerve, and the variably present
middle superior alveolar nerve[7]. All of these nerves create the superior dental plexus which is above the
maxillary teeth. The lower mandibular teeth and their associated periodontal ligament are supplied by the
inferior alveolar nerve, a branch of the mandibular division. This nerve lines inside the mandible, inside of the
inferior alveolar canal below the mandibular teeth, giving off branches to all the lower teeth (inferior dental
plexus)[8]. The mouth plays a very vital role in the anatomy of eating, drink, speaking etc. Usually, the act of
breathing out of the mouth is known as mouth breathing, if there is an obstruction when it comes to breathing
through the nose (which is the designated breathing organ for the human body[9].
Pharynx
The pharynx is part of the digestive system as well as the conducting zone for the respiration system. The
conducting system includes the nostrils of the nose and the larynx, trachea, bronchioles and bronchi- they
filter, warm and moistens are, conducts into the lungs[10]. The human pharynx is divided into three different
sections, which are the nasopharynx, the oropharynx and the laryngopharynx (these regions are important for
vocalization). The pharynx is a 4-5-inch-long semi-circular fibromuscular tube which is the joining of the nose
and the mouth to the oesophagus. The larynx allows the passage of swallowed solids and liquids. There are
no enzymes in the pharynx. The upper sections of the pharynx, the nasopharynx stretches between the base
of the skull towards the upper surface of the soft palate[11]; this includes the space located between the internal
nares and soft palates that lie up onto the oral cavity. The adenoids (also known as the pharyngeal tonsils) are
a type of lymphoid tissue structure found in the posterior wall of the nasopharynx. What is known as
Waldeyer’s tonsillar ring is an annular arrangement of the lymphoid tissue in both the nasopharynx and in the
oropharynx, the nasopharynx is in line with the respiratory epithelium that is columnar and ciliated.
Mucus is something that can greatly obstruct the nasopharynx; it can congest due to the upper respiratory
infection. Connecting from the middle of the ear towards the pharynx is the auditory tube; it opens into the
nasopharynx as the pharyngeal opening of this tube. The opening and closing of these tubes serve as a way
to equalize the pressure that can be felt in the middle ear with that of ambient atmospheric pressure. The
anterior aspect of the nasopharynx communicates with and through the choanae with its nasal cavities. On the
opposite side of the wall is the pharyngeal opening of the auditory tube, which to some degree is triangular in
shape, held behind firm importance which is the torus tuberous, caused by the medial end of the locating
cartilage of the tube which elevates the mucous membrane. The pharynx moves food from the mouth to the
oesophagus, it can also move air from the nasal or oral cavity to the larynx. In human speech, the pharyngeal
consonants are articulated here.
, Oesophagus
The walls of the oesophagus from its lumen consists of things such as mucosa membrane, submucosa (which
is a type of connective tissues), the layer of muscle fibres as well as a layer of fibrous connective and outer
layer of tissues. The mucosa itself is a stratified squamous epithelium, consisting of three separate layers of
squamous cells, which aid in contracting the single layer of columnar cells of the human’s stomach. Most of
the muscle is smooth muscle although striated muscle predominates in its upper third. It has two muscular
rings on its wall, one towards the top and one towards the bottom. The lower ring helps to prevent reflux of
acidic stomach content. The oesophagus has a rich blood supply and venous drainage. Its smooth muscle is
innervated by involuntary nerves (sympathetic nerves via the sympathetic trunk and parasympathetic nerves
via the vagus nerve) and in addition, voluntary nerves (lower motor neurons) which are carried in the vagus
nerve to innervate its striated muscle.
The oesophagus is one of the upper sections of the digestive system, having a multitude of taste buds on its
upper section[12]. It begins at the back of the mouth, passing downwards through the rear part of the
mediastinum, through the diaphragm, and into the stomach. In humans, the oesophagus generally starts at the
level of the sixth cervical vertebra right behind the cricoid cartilage of the trachea, entering the diaphragm at
about the level of the tenth thoracic vertebra, and ends at the cardia of the stomach, at the level of the
eleventh thoracic vertebra[13]. The oesophagus is usually about 25 cm in length[14]. There are many blood
vessels that are used in the oesophagus along with blood supply varying along its path, the upper sections of
the oesophagus and the upper oesophageal sphincter receive all its blood supply from the inferior thyroid
artery[15]. The drainage also differs along the course of the oesophagus. All of this occurs in both the upper and
middle parts of the oesophagus that then drains into the azygos and veins, and blood from the lower part
drains into the left gastric vein. All these veins will then begin to drain into the superior vena cava, with the
exception of the left gastric vein, which is a branch of the portal vein. Lymphatically, the upper third of the
oesophagus drains into the deep cervical lymph nodes, the middle into the superior and posterior mediastinal
lymph nodes, and the lower oesophagus into the gastric and celiac lymph nodes. This is similar to the
lymphatic drainage of the abdominal structures that arise from the foregut, which all drain into the celiac
nodes[16].
Food is taken and ingested through the mouth which is then swallowed, passing first into the pharynx and then
into the oesophagus. The oesophagus is then one of the first components of the digestive system as well as
the gastrointestinal tract. After the food has been ingested, food passes through the oesophagus, it enters the
stomach[17]. When food is then being swallowed, the epiglottis ( leaf-shaped flap in the throat that prevents
food from entering the windpipe and the lungs) moves backwards to cover the larynx, preventing food from
entering the trachea. At the same time, the upper oesophagal sphincter relaxes, allowing a bolus of food to
enter. Peristaltic contractions of the oesophagal muscle push the food down the oesophagus. These rhythmic
contractions occur both as a reflex response to the food that is in the mouth and also as a response to the
sensation of food within the oesophagus itself. Along with peristalsis, the lower oesophagal sphincter
relaxes[18].
Stomach
In the human anatomy and many other animals (including several invertebrates), the stomach is a hollow
organ in the gastrointestinal tract. The stomach has many functions and developed structure as it is a vital role
in digestion, as it is an important digestive organ; In the digestive system, the stomach is involved in the
second phase of digestion, which is after chewing. It performs a chemical breakdown by the enzymes and
hydrochloric acid present. In the human digestive system, a bolus (a small ball of chewed up food) enters the
stomach through the oesophagus from the lower oesophagal sphincter. The stomach releases proteases,
which are a type of protein-digesting enzyme (pepsin) and as mentioned earlier hydrochloric acid. The role of
these enzymes is to kill any bacteria that may be present as well as the providing acidic pHs of 2 for any of the
proteases to work. Food is churned by the stomach through muscular contractions of the wall called
peristalsis; reducing the volume of the bolus, before looping around the fundus[19] and the body of the stomach
as the boluses are converted into partially digested food. This digested slowly passes through the pyloric
sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins. The gastric
