DIGESTIVE SYSTEM

1
DIGESTIVE SYSTEM PROCESSES and PHYSIOLOGY
Swallowing Peristalsis Absorption Key Organs Gut
Feedback
2
Fig. 12.1
3
SWALLOWING
4
PERISTALSIS
5
SMALL INTESTINE
Duodenum ? Jejenum ? Ileum
6
Fig. 12.6
Small Intestine
7
Its all about surface area
1.Plicae 2. Villi 3. Microvilli
8
VILLI
Microvilli
9
Its All About Active Transport
Products of Carbohydrate and Protein Digestion
are actively transported from small intestine
into the villus. These simple sugars and amino
acids are taken into the capillary bed in the
villus and transported to the Liver.
Products of Fat digestion are absorbed into the
central lymphatic vessel called a LACTEAL
10
DUODENUM Functions
The Duodenum is only about 45 cm (18 inches long)
but it plays a couple of very important roles
1. Receives incoming Stomach Chyme, Pancreatic
Juices and Bile from Liver and Gall bladder.
2. Secretes digestive juces/enzymes from duodenal
glands
11
Large Intestine Functions
1. Receives undigested waste and helps absorb
fluid (water) from those wastes back into the
bloodstream, to help keep us from dehydrating.
2. Helps compact and form feces.
3. Harbours helpful bacteria which can further
break down wastes to free up minerals and some
bacteria will help produce and free up some
vitamins, such as Vitamin K
12
Stomach Functions
1. Storage of a meal most expanded structure
along the alimentary canal
13
2. Mechanical Digestion of food Stomach is very
muscular and it squeezes to churn and mix food to
physically break it down
14
3. Chemical Digestion of food Adds PEPSIN
enzyme to start chemically breaking proteins into
small peptide chains
15
4. Protection against Germs HCl helps activate
enzymes but it also helps kill many of the
bacteria that we ingest.
16
Fig. 12.5
The STOMACH
17
GASTRIC GLANDS
Some gastric glands are classified as being
EXOCRINE. ????
They are responsible for producing gastric juice
which consists of mucous, HCl, Pepsinogen and
water. In the presence of HCl the Pepsinogen
converts to active Pepsin. This Pepsin is a
PROTEASE enzyme, breaking proteins into smaller
peptide chains
18
Stomach control
When the stomach receives a meal, it gets turned
on!
The stomachs exocrine glands are turned on by a
Hormone called GASTRIN. Gastrin is produced and
released from the stomachs ENDOCRINE glands????
19
PANCREAS Function
The pancreas is a glandular organ that acts both
as an Exocrine Gland and also as an Endocrine
Gland. We mostly focus on its exocrine role. It
produces a variety of hydrolytic digestive
enzymes that help chemically finish off the
digestion of Carbohydrates, Fats and Proteins.
20
Pancreatic Exocrine Function
When acidic chyme from the stomach enters the
duodenum, the pancreas is stimulated to secrete
pancreatic juice
21
Pancreatic Juice

• INGREDIENTS
• Sodium Bicarbonate NaHCO3?
• LIPASES?
• PANCREATIC AMYLASE?
• TRYPSIN same function as PEPSIN
• NUCLEASES (work on Nucleic Acids)?

22
Pancreatic Endocrine Function
When blood sugar is getting too high. The
pancreas produces and secretes INSULIN into the
bloodstream
23
Pancreatic Endocrine Function
When blood glucose levels start getting too low,
the Pancreas will produce and secrete the hormone
GLUCAGON. Glucagon will travel through the
bloodstream to tell muscle and liver cells to
break down their stored Glycogen back into
glucose and send it back into the blood, to raise
blood sugar levels
24
Liver Functions
25
You Cant Live without your LIVER!

1. Produces Bile?
2. Converts Carbohydrates to control blood sugar
   levels.
3. Detoxifies the blood?
4. Makes lots of vital Plasma Proteins?
5. Stores Iron and Fat Soluble Vitamins ADEK.
6. Helps break down nitrogenous metabolic wastes.
   Example Ammonia ? Urea
7. Produces Cholesterol and regulates blood
   cholesterol levels.

26
Fig. 12.11
27
Fig. 12.7
Controlling The Gut
28
Fig. 12.12
29
Tap. 237