,Human systems
Nutrition and digestive system
The digestive system:
1. Ingestion; the intake of food through the
mouth
2. Digestion; the break down of large, and
complex food particles to smaller and simpler
molecules that can be absorbed by cells. Esophageal
3. Absorption; the process where nutrients sphincter
(monomers) are absorbed into the bloodstream
and finally into cells
Pyloric sphincter
4. Elimination; waste is expelled
a) mechanical digestion - The physical breakdown of food
b) chemical digestion - The break down of food
with the help of enzymes
Mouth:
Mechanical: chewing with teeth increases surface
The entire length of the digestive tract is lined with area for enzymes to work
epithelial tissue
→ contains a lot of goblet cells which secrete mucus. Chemical: Break down of carbohydrates with the
help of saliva. Saliva is released from salivary
Mucus does two things glands it contains water mucus salt and the
1. Protects tract from digestive enzymes enzyme (amylase)
2. Moves materials along the tube
Bolus is what food is called now
Why we need the digestive system:
→ food and drinks consumed must be Esophagus: a long muscular tube that carries
broken down into smaller molecules so they bolus from the mouth to the stomach
can be absorbed into the body
→ the esophagus contracts and relaxes to produce
Digestive enzymes help break food into smaller wave-like contraction and relaxation that pushes
pieces so that it is easier to digest the bolus to the stomach
→ this process is known as peristalsis
3 classes of food
→ macro (giant) molecules
a) fats → fatty acids and glycerol
b) proteins → amino acids
c) carbs → glucose
→ monomers are the smaller particles
polysacharide
,Stomach:
The stomach has three methods of
Mechanical:
protection:
→ contraction and relaxation of the smooth
1. Thick mucus bicarbonate barrier
muscles of the stomach allow churning of food 2. Junctions between the epithelial cells
3. Rapid renewal of gastric cells
Chemical:
→ gastric juice is released by stomach cells
→ made of: HCL (strong acid), water, pepsin (enzyme), and mucus
→ pepsin is only activated in low ph ( highly acidic environment ), the HCL lowers the ph and
activates pepsin
→ pepsin will break down proteins into amino acids,
It is now called chyme
Small intestine:
1. Duodenum (both digestion and absorption)
→ bile poduced in the liver and stored in the gallbladder enter the duodenum
→ it contains water, salt, lipids
Bile will do two things :
1. Neutralise the acidie chyme
2. Emulsify the fats (needs to become soluble)
→ pancreas releases pancreatic juice into the duodenum.
Pancreatic juice contains 3 classes of enzymes : trypsin (protein),
Amylase (carbs), and lipase,(lipids, fats)
2. Jejunum (absorption)
Microvilli
Villi
→ villi and microvilli are folds and projections that increase the surface area for the absorbtion of
nutrients
→ they enter the bloodstream
→ the blood leaving the small intestine is rich in nutrients
3. Ileum (absorption)
, Large intestine: Rectum:
→ acts as a temporary storage facility
→ absorbs water and vitamins from remaining
for feces before it is excreted from the
food
body
→ also stores the remains of food that cant be
ansorbed
→ larger diameter than the small intestine
Accessory organs :
→ liver, produces bile which is stored in the gallnladder.
Pancreas:
1. Is involved in supplying enzymes required for digestion directly into the small intestine
2. Secretes hormone called insulin directly into the bloodstream
3. Insulin causes most of the body's cells to absorb glucose
If I have just eaten a slice of pizza the following process will take place:
Firstly, throuh ingestion and mechanical digestion, the pizza enters my mouth my teeth will chew
the food breaking it down into smaller pieced increasing surface area for enzymes to break it down.
Then through chemical digestion enzymes including amylase will break down the food further.
This comes from the salivary glands. Next the bolus will enter the esophagus where a series of
contracting and relaxing muscle movements called peristalsis will push the bolus into the stomach.
In the esophagus mucus performs two functions: first it protects the tracts and second it helps push
bolus down the esophagus. After this the esophageal sphyncter will open and allow bolus to enter the
stomach. In the stomach mechanical digestion takes place where movements of muscle are churning
the chyme. Through chemical digestion gastric juices including musus, pepsin, and HCL. The hcl
lowers the ph level allowing pepsin to activate and break down proteins imto aminoc acids. Next the
pyloric sphincter will open and allow food to enter the small intestine. The small intestine consists
of 3 parts duodenum, jejunum, and ileum. In the duodenum digestion and absorption take place.
Bile produces in the liver and stored in the gallbladder will enter the duodenum. Bile has two
functions; 1. Neutralize the acidic chyme 2. Emulsify and dissolve fats. The pancreas then releases
pancreatic juice which contains 3 classes of enzymes trypsin for proteins amylase for carbs and
lipase for lipids and fats. Next in the jejunum and the ileum, only absorption takes place. Here, thbe
villi and microvilli which are folds and projections increase the surface area for absorption. Then
they enter the blood stream. The blood leaving the small intwstine is rich in nutrients. Next the
large intestine absorbs the remaining water andnvitamins from the food and stores the food that
can not be absorbed. In the rectum waste is stored temporarily before it is excreted from the body.
Next are the accessory prgans. Although they dont have food passing through them directly they
play an important role in the digestive system. Tthe liver produces bile and it gets stored in the
gallbladder. Tje pancreas, supplies enzymes into the small intestine, secretes insulin into the blood
Nutrition and digestive system
The digestive system:
1. Ingestion; the intake of food through the
mouth
2. Digestion; the break down of large, and
complex food particles to smaller and simpler
molecules that can be absorbed by cells. Esophageal
3. Absorption; the process where nutrients sphincter
(monomers) are absorbed into the bloodstream
and finally into cells
Pyloric sphincter
4. Elimination; waste is expelled
a) mechanical digestion - The physical breakdown of food
b) chemical digestion - The break down of food
with the help of enzymes
Mouth:
Mechanical: chewing with teeth increases surface
The entire length of the digestive tract is lined with area for enzymes to work
epithelial tissue
→ contains a lot of goblet cells which secrete mucus. Chemical: Break down of carbohydrates with the
help of saliva. Saliva is released from salivary
Mucus does two things glands it contains water mucus salt and the
1. Protects tract from digestive enzymes enzyme (amylase)
2. Moves materials along the tube
Bolus is what food is called now
Why we need the digestive system:
→ food and drinks consumed must be Esophagus: a long muscular tube that carries
broken down into smaller molecules so they bolus from the mouth to the stomach
can be absorbed into the body
→ the esophagus contracts and relaxes to produce
Digestive enzymes help break food into smaller wave-like contraction and relaxation that pushes
pieces so that it is easier to digest the bolus to the stomach
→ this process is known as peristalsis
3 classes of food
→ macro (giant) molecules
a) fats → fatty acids and glycerol
b) proteins → amino acids
c) carbs → glucose
→ monomers are the smaller particles
polysacharide
,Stomach:
The stomach has three methods of
Mechanical:
protection:
→ contraction and relaxation of the smooth
1. Thick mucus bicarbonate barrier
muscles of the stomach allow churning of food 2. Junctions between the epithelial cells
3. Rapid renewal of gastric cells
Chemical:
→ gastric juice is released by stomach cells
→ made of: HCL (strong acid), water, pepsin (enzyme), and mucus
→ pepsin is only activated in low ph ( highly acidic environment ), the HCL lowers the ph and
activates pepsin
→ pepsin will break down proteins into amino acids,
It is now called chyme
Small intestine:
1. Duodenum (both digestion and absorption)
→ bile poduced in the liver and stored in the gallbladder enter the duodenum
→ it contains water, salt, lipids
Bile will do two things :
1. Neutralise the acidie chyme
2. Emulsify the fats (needs to become soluble)
→ pancreas releases pancreatic juice into the duodenum.
Pancreatic juice contains 3 classes of enzymes : trypsin (protein),
Amylase (carbs), and lipase,(lipids, fats)
2. Jejunum (absorption)
Microvilli
Villi
→ villi and microvilli are folds and projections that increase the surface area for the absorbtion of
nutrients
→ they enter the bloodstream
→ the blood leaving the small intestine is rich in nutrients
3. Ileum (absorption)
, Large intestine: Rectum:
→ acts as a temporary storage facility
→ absorbs water and vitamins from remaining
for feces before it is excreted from the
food
body
→ also stores the remains of food that cant be
ansorbed
→ larger diameter than the small intestine
Accessory organs :
→ liver, produces bile which is stored in the gallnladder.
Pancreas:
1. Is involved in supplying enzymes required for digestion directly into the small intestine
2. Secretes hormone called insulin directly into the bloodstream
3. Insulin causes most of the body's cells to absorb glucose
If I have just eaten a slice of pizza the following process will take place:
Firstly, throuh ingestion and mechanical digestion, the pizza enters my mouth my teeth will chew
the food breaking it down into smaller pieced increasing surface area for enzymes to break it down.
Then through chemical digestion enzymes including amylase will break down the food further.
This comes from the salivary glands. Next the bolus will enter the esophagus where a series of
contracting and relaxing muscle movements called peristalsis will push the bolus into the stomach.
In the esophagus mucus performs two functions: first it protects the tracts and second it helps push
bolus down the esophagus. After this the esophageal sphyncter will open and allow bolus to enter the
stomach. In the stomach mechanical digestion takes place where movements of muscle are churning
the chyme. Through chemical digestion gastric juices including musus, pepsin, and HCL. The hcl
lowers the ph level allowing pepsin to activate and break down proteins imto aminoc acids. Next the
pyloric sphincter will open and allow food to enter the small intestine. The small intestine consists
of 3 parts duodenum, jejunum, and ileum. In the duodenum digestion and absorption take place.
Bile produces in the liver and stored in the gallbladder will enter the duodenum. Bile has two
functions; 1. Neutralize the acidic chyme 2. Emulsify and dissolve fats. The pancreas then releases
pancreatic juice which contains 3 classes of enzymes trypsin for proteins amylase for carbs and
lipase for lipids and fats. Next in the jejunum and the ileum, only absorption takes place. Here, thbe
villi and microvilli which are folds and projections increase the surface area for absorption. Then
they enter the blood stream. The blood leaving the small intwstine is rich in nutrients. Next the
large intestine absorbs the remaining water andnvitamins from the food and stores the food that
can not be absorbed. In the rectum waste is stored temporarily before it is excreted from the body.
Next are the accessory prgans. Although they dont have food passing through them directly they
play an important role in the digestive system. Tthe liver produces bile and it gets stored in the
gallbladder. Tje pancreas, supplies enzymes into the small intestine, secretes insulin into the blood
