BIOLOGY
HUMAN NUTRITION
~INGESTION- Intake of food into the body
~DIGESTION- Two types :1) Physical digestion is breaking down of large
molecules into smaller molecules to increase surface area. 2) Chemical diges-
tion is conversion of large insoluble molecules to small soluble molecules in
order to pass through cell membrane.
~Food enters the mouth and goes into the buccal cavity. Food is broken
through the two types of front teeth- incisor and canine which are responsible
for biting and tearing food. The back teeth- premolar and molar are used for
grinding and chewing of the food. As soon as the food enters in the mouth,
salivary glands secrete salivary amylase which acts on starch to convert it into
maltose.
~Pharynx is a passage that leads to mouth to oesophagus while passing
through larynx(voice box) which has a slit like opening called glottis. To pre-
vent food entering trachea ( windpipe) ,as pharynx is a common passage of
both food and air , pharynx moves up and is covered by a slit like opening
called epiglottis which is located just behind the root of the tongue and has a
flap like cartilage.
~When the food enters oesophagus, it becomes a ball called bolus which
moves through 2 smooth muscles called longitudinal muscles and circular
muscles which work in an antagonistic manner. They both cause rhythmic
contractions and relaxations in order to help the bolus move forward in the
oesophagus. Just behind the bolus , circular muscles will contract and longi-
tudinal muscles will relax. As the bolus moves , the circular muscles will relax
and the longitudinal muscles will contract. The lumen becomes narrow and
the bolus of food moves forward.
~Stomach is a small distensible muscular bag which has a mucous coat with
gastric glands which secrete gastric juices. It contains the enzyme pepsin
which has a pH of 2. It also contains HCL which provides the best pH for
pepsin to work and kills harmful organisms.
HUMAN NUTRITION
~INGESTION- Intake of food into the body
~DIGESTION- Two types :1) Physical digestion is breaking down of large
molecules into smaller molecules to increase surface area. 2) Chemical diges-
tion is conversion of large insoluble molecules to small soluble molecules in
order to pass through cell membrane.
~Food enters the mouth and goes into the buccal cavity. Food is broken
through the two types of front teeth- incisor and canine which are responsible
for biting and tearing food. The back teeth- premolar and molar are used for
grinding and chewing of the food. As soon as the food enters in the mouth,
salivary glands secrete salivary amylase which acts on starch to convert it into
maltose.
~Pharynx is a passage that leads to mouth to oesophagus while passing
through larynx(voice box) which has a slit like opening called glottis. To pre-
vent food entering trachea ( windpipe) ,as pharynx is a common passage of
both food and air , pharynx moves up and is covered by a slit like opening
called epiglottis which is located just behind the root of the tongue and has a
flap like cartilage.
~When the food enters oesophagus, it becomes a ball called bolus which
moves through 2 smooth muscles called longitudinal muscles and circular
muscles which work in an antagonistic manner. They both cause rhythmic
contractions and relaxations in order to help the bolus move forward in the
oesophagus. Just behind the bolus , circular muscles will contract and longi-
tudinal muscles will relax. As the bolus moves , the circular muscles will relax
and the longitudinal muscles will contract. The lumen becomes narrow and
the bolus of food moves forward.
~Stomach is a small distensible muscular bag which has a mucous coat with
gastric glands which secrete gastric juices. It contains the enzyme pepsin
which has a pH of 2. It also contains HCL which provides the best pH for
pepsin to work and kills harmful organisms.
