1. The Digestive System
Human Biology
Ms. Ghtaura

2. What’s happening? INGESTION:
the process of taking a (food) into the or
DIGESTION:
the and breaking down of ingested food into particles, then into small enough to move through cells and into the environment.
ABSORPTION:
the passage of digested nutrients from the gut lumen into the blood or lymph, which distributes them through the body.
ELIMINATION:
the of residues from the body.
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3. physical breakdown
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4. Tongue: has taste buds so we can enjoy our food
3 salivary glands in the mouth
Parotid glands
Sublingual glands
Submandibular glands
Mouth food
Tongue: has taste buds so we can enjoy our food
Teeth: for chewing or so food is convenient for .
After mastication, our food form into a mass called
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5. Pharynx – region the mouth and the esophagus made of a long tube
Epiglottis – flap of elastic cartilage tissue attached to the entrance of the
Glottis is the opening to the larynx
Esophagus – bolus is passed into this tube from the to stomach
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6. Swallowing and Peristalsis
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7. Stomach
Stomach – a thick walled, J-shaped organ which food until ready to enter the
Entrance of food from the esophagus to stomach is marked by sphincter
Sphincter – muscles that encircle tubes and act as valves (saloon doors)
Churning – muscular walls of the stomach , mixing the food with juice
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8. peristalsis happens throughout the gut
Chemical digestion is aiding in the overall digestion of food as discussed in the next section
As this is happening, food is being pushed along the digestive track (small and large intestine) rhythmic muscle movements
The bolus leaves the stomach in the form of ‘chyme’
Chyme is squeezed through the pyloric sphincter to the duodenum of the small intestine
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9. chemical breakdown
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10. Salvia
First chemical breakdown occurs in the mouth as food turns into bolus
3 salivary glands in the mouth
glands
Endocrine glands = secretes the products (hormones) directly into the blood rather than into a duct
Exocrine = secretes products into a duct that can directly lead to external environments
Salivary glands are exocrine glands that produce (neutral pH)
Saliva is made up of an enzyme called and water
Amylase breaks down polysaccharides into (disaccharide)
Salivary amylase
+ H20
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11. Stomach Pepsin Protein + H20 Peptides
The stomach contains millions of gastric glands which make gastric juices
Gastric juice is made up of pepsinogen, HCl and mucus.
A think layer of mucus protects the lining of the stomach from HCl
If the HCl penetrates this lining an ulcer can result
HCl in the stomach has two primary roles:
Activates pepsinogen into pepsin (a protease)
This happens since active pepsin may destroy proteins in the gastric cells, so its important that it remains in the form on pepsinogen until it is secreted out of the gastric cells
Keeps the environment of the stomach at pH 2 to kill bacteria present in most food
Pepsin breaks down proteins in the following manner:
Pepsin
Protein + H20 Peptides
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12. In the Duodenum
As the chyme is being pushed into the duodenum, pancreatic juices (pH 7.5 to 8.5), and bile are also being secreted into the
Hence, the duodenum is the site for many chemical breakdowns during digestion
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13. Liver bile salts Fat Fat Droplets Largest gland in the body
Produces (which contains bilirubin and bile salts)
Bile is stored in the
Bile fat into fat droplets in the duodenum
Fat droplets have a larger surface area available to be further
bile salts
Fat Fat Droplets
Takes a while for your body to adjust without your gall bladder, but it is possible to have it removed and still live a normal life.
Ms. Ghtaura

14. Pancreas Is an organ in the digestive system Is an and gland
Secretes the enzymes: , , and
These enzymes are produced in the pancreas and are released into the duodenum as pancreatic juice
Pancreatic juice is also known to contain basic sodium bicarbonate ( ) which functions in:
acidic chyme
Providing a basic pH for optimal pancreatic enzyme function
Endocrine: insulin
Exocrine: pancreatic juices
Ms. Ghtaura

15. Pancreas polysaccharide + H20 disaccharides
Pancreatic amylase breaks down polysaccharides into molecules
Since the salivary amylase may have not this breakdown in the mouth (depends on how long you chew your food) the pancreatic amylase makes up for this by completing the same digestion in the .
Endocrine: insulin
Exocrine: pancreatic juices
Pancreatic amylase
polysaccharide + H20 disaccharides
Ms. Ghtaura

16. Pancreas + H20 Pancreatic trypsin ( ) also breaks down proteins into
Since the pepsin may have not completed this breakdown in the the pancreatic trypsin makes up for this by completing the same digestion in the .
Trypsin exists in the pancreatic cells as trypsinogen. Upon being release into the duodenum, it is activated into trypsin so it can break down proteins
Endocrine: insulin
Exocrine: pancreatic juices
Pancreatic trypsin
+ H20
Ms. Ghtaura

17. Pancreas + H20 + Pancreatic lipase further breaks down fat
Bile helps break down fats into fat , which exposes more surface area for to act on
Each triglyceride molecule (neutral fat) in a fat droplet is then broken down into 3 fatty acids and a 1 glycerol molecule
These broken down triglycerides are small enough to be into the small intestine.
Endocrine: insulin
Exocrine: pancreatic juices
Pancreatic lipase
+ H
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18. Small Intestine Primary functions:
absorption of nutrients into the and systems.
Further chemical breakdown of proteins and carbohydrates
Named for its diameter (though it is longer in length than the large intestine)
The inside of the small intestine has like projections called which increase the surface area for of nutrients
Each villus is lined with epithelial cells, which have microvilli structures on their
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19. Small Intestine The small intestine is made up of the: Duodenum –
Jejunum –
Ileum –
Chemical break down continues in the duodenum while the rest of the small intestine is involved primarily in
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20. Small intestine + H20 acids
Light micrograph of small intestine
Peptidases are also a type of which complete the digestion of proteins to
Peptidases are found in the cell membrane of the epithelial cells lining the
As the cross into cells, the break them down into
Then, the amino acids enter the cells
peptidase
+ H acids
Ms. Ghtaura

21. Small intestine
Light micrograph of small intestine
Maltase is an enzyme which completes the digestion of maltose into to glucose molecules
Maltases are found in the cell membrane of the cells lining the
As the maltose molecules try to cross into , the maltase breaks them down into two glucose
Glucose then enters the cells
There are many enzymes that break down disaccharides into monosaccharides other than maltase. One example is lactase, which breaks down lactose into
maltase
+ H20 2
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22. Monosaccharides form disaccharides
There are many enzymes that break down disaccharides into monosaccharaides other than maltase. One example is , which breaks down lactose into galactose and glucose
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23. Absorption
Glucose and amino acids are directly absorbed into the blood capillaries and eventually the blood stream
acids and reforms into neutral fats upon entering the epithelial cells and then enter the
Lymphatic system rapidly dumps the fat into bloodstream so the lipids can be utilized all over the body (phospholipids, cholesterol)
Circulating blood carries amino acids and glucose away into the body
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24. Large Intestine
The large intestine is also known as the colon
The ascending colon is the junction point between the small and large intestine
The cecum, , rectum and anal canal are all a part of the intestine
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25. Large Intestine - Appendix
Some doctors argue that the appendix plays a role in human while others say its function has been lost over
It is attached to the .
The appendix is subject to (injury or obstruction of fecal matter)
During inflammation, if the fluid content increases enough, it can burst.
A deadly infection (peritonitis) can result after the appendix bursts causing hemorrhage of all organs
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26. Large Intestine The colon absorbs , salts, and some
Inside the large intestine, there are anaerobic bacteria which break down material
Anaerobic bacteria also produce and other molecules that can be absorbed and used by us.
The rectum stores non-digestible material until it is ready to be
The sigmoid colon enters the rectum
Rectum is the last of the large intestine
The rectum opens at the anus, where (expulsion of feces) occurs
E.Coli is a good bacteria and helps create vitamin K2
Can survive outside the body (not anaerobic) its important we wash our hands after going to the bathroom.
Ms. Ghtaura

27. Major functions of the Liver
Detoxifies blood by and poisonous
Stores and fat soluble A, D, E, and K
Makes plasma proteins such as and from amino acids
Removes (derived from the breakdown of hemoglobin molecules) and excretes it in bile – hence the yellowish-green colour
Helps regulate blood level, converting some cholesterol into salt
Stores glucose as after a meal and breaks down glycogen into glucose to help maintain the glucose concentration of blood between periods
If glycogen is not available, it converts amino acids and glycerol (from fats) into glucose. The liver produces urea after breaking down amino acids
Ms. Ghtaura

28. Blood glucose levels
The pancreas has an function, where it secretes insulin directly into the blood stream to control levels.
Insulin is a hormone which causes cells (ex: liver or muscle cells) to take up  from the blood.
In the liver, glucose is taken up and is stored as until needed by the body
Ms. Ghtaura

29. By the end of this section, you should be able to:
Identify and give a function for each of the following:
– mouth
– liver
– tongue
– gall bladder
– teeth
– pancreas
– salivary glands
– small intestine
– pharynx
– appendix
– epiglottis
– large intestine (colon)
– esophagus
– rectum
– cardiac sphincter
– anus
– stomach
– pyloric sphincter
– duodenum
Ms. Ghtaura

30. describe swallowing and peristalsis
identify the pancreas as the source gland for insulin, and describe the function of insulin in maintaining blood sugar levels
list at least six major functions of the liver
explain the role of bile in the emulsification of fats
describe how the small intestine is specialized for chemical and physical digestion and absorption
describe the structure of the villus, including microvilli, and explain the functions of the capillaries and lacteals within it
describe the functions of anaerobic bacteria in the colon
Ms. Ghtaura

31. describe the role of water as a component of digestive juices
relate the following digestive enzymes to their glandular sources and describe the digestive reactions they promote:
– salivary amylase
– pancreatic amylase
– proteases (pepsinogen, pepsin, trypsin)
– lipase
– peptidase
– maltase
describe the role of water as a component of digestive juices
describe the role of sodium bicarbonate in pancreatic juice
describe the role of hydrochloric acid (HCl) in gastric juice
describe the role of mucus in gastric juice
describe the importance of the pH level in various regions of the digestive tract
Ms. Ghtaura

32. Mandatory Vocabulary
absorption, anaerobic bacteria, anus, appendix, bile, capillary, cardiac sphincter, chemical digestion, digestive enzyme, digestive tract, duodenum, emulsification, epiglottis, esophagus, gall bladder, gastric juice, hydrochloric acid (HCl), insulin, intestinal juice, lacteals, large intestine (colon), lipase, liver, maltase, microvillus, nuclease, pancreas, pancreatic amylase, pancreatic juice, pepsin, pepsinogen, peptidase, peristalsis, pH, pharynx, physical digestion, protease, pyloric sphincter, rectum, salivary amylase, salivary gland, salivary juice/saliva, small intestine, sodium bicarbonate, stomach, swallowing, trypsin, villus
Ms. Ghtaura