Download guided notes digestive system

Digestion
Mechanical and Chemical Breakdown of Ingested Food
Why Digestion?
 Most food is solid and in the form of large complex molecules which are insoluble and chemically inert
(not readily usable)
 As food was synthesized by other organisms, it contains materials not suitable for human tissue - these
need to be separated and removed
 Large molecules need to be broken down into smaller molecules that can be readily absorbed across
membranes and into cells
 Small molecules can be reassembled into new products (e.g. amino acids can be reassembled to make
new proteins)
3 Stages in Digestion
1. Digestion - _____________________________________________
______________________________________________________
– 2 types of digestion
• __________________ (Mastication)
• ___________________ (Enzymes)
2. ______________________________ into the blood stream
3. Elimination of __________________________________________
Organs and Glands of the Digestive System
Alimentary canal
Definition:
Accessory Organs
Definition:
Organs:
Organs:
Enzymes of the Digestive System
 Enzymes are biological catalysts which _____________________________ (e.g. digestion) by lowering
the ______________________________
 Enzymes allow digestive processes to occur at________________________ and at sufficient speed to
meet the organism's survival requirements
 Enzymes are _________________________________ and so can allow digestion of certain molecules
to occur independently of others
The Mouth
• Mechanical breakdown of nutrients begins in the mouth by chewing
(_____________________________).
– The purpose of chewing is to ______________________________ ___________________.
(speeds up digestion)
• Chemical breakdown of starch also __________________________. Starch is converted into glucose
by salivary amylase (secreted by the salivary glands)
• This mixture of food and saliva is made into a ___________________________
___________________________ and then pushed into the pharynx by the tongue which triggers
involuntary swallowing.
• The esophagus is a muscular tube whose muscular contractions (peristalsis) propel food to the stomach.
– Peristalsis _________________________________________________
__________________________________________________________
Swallowing
 Oral Phase: ________________________________
◦ Food is prepared into a food _________________(pellet of food)
 Pharyngeal Phase: _____________________________________
◦ Food is pushed further into the pharynx and esophagus. Involuntary closure of larynx prevents
food from going “down the wrong pipe”
 Esophageal Phase
◦ Food is passed through ________________________________________
◦ upper _________________________ prevents food from being regurgitated; lower sphincter
prevents ______________________________________ from traveling backwards
The Stomach ( Churn, Churn, Churn)
 Functions:
◦ ____________________________, holding a meal in the upper portion and releasing it a little at
a time into the lower portion for processing
 _____________________________- valve that controls flow of partially digested food
into the small intestine
◦ ____________________________, the strong muscles contract and mash the food into a sticky
◦ ____________________________; a sterilizing system, where there cells in the stomach
produce an acid which kills germs
◦ ____________________________, the stomach produces digestive fluid which splits and cracks
the chemicals (mainly proteins) in food to be distributed as fuel for the body
 Acids __________________________________________________ that denatures
proteins, while proteases like pepsin hydrolyze large proteins
 The stomach also releases a hormone (_____________________) that regulates stomach secretions
 The stomach turns food into a creamy paste called ____________________
Specialized Mucosa of the Stomach
 Simple columnar epithelium
 Mucous neck cells – produce a sticky alkaline mucus
 Gastric glands – ______________________________
 Chief cells – produce protein-digesting enzymes (pepsinogens)
 Parietal cells – produce hydrochloric acid
 Endocrine cells – produce ___________________________
Structure of the Stomach Mucosa
 Gastric pits formed by folded mucosa
 Glands and specialized cells are in the gastric gland region
The Small Intestine
 The small intestine is where usable food substances (e.g. nutrients) are ___________________________
 The ____________________ and __________________________ (via the bile duct) both secrete
substances into the small intestine to aid in digestion
 The small intestine is lined with _________________________________ to allow for the mixing and
moving of digested food products (via segmentation and peristalsis)
 It also contains small pits (crypts of lieberkuhn) that secrete intestinal juices
 The small intestine contain infoldings called villi, ___________________________________________
_______________________________
Subdivisions of the Small Intestine
“Dogs Just Itch!”
 ______________________________
 Attached to the stomach
 Curves around the head of the pancreas
 ______________________________
 Attaches anteriorly to the duodenum
 ______________________________
 Extends from jejunum to large intestine
Villi and MircoVilli
• The ______________
_______________ is lined
with vill and microvilli
• The purpose of villi and
microvilli are to
________________________
in the small intestines.
Increase the speed at which
________________________
– The small intestines a
6 meter long tube has
a surface area of 300
square meters or the
surface area of a 500600m long tube.
• Each villus has a
________________________
supplied by a small arteriole.
Absorbed nutrients pass
through the ______________
_______________________
(blood stream), usually by passive transport.
The Large Intestine
• The large intestine is made up by the cecum, appendix, colon, and rectum.
• Digested food is pushed from the small intestines into the large intestine.
• No ____________________________________________________________
• ________________, and ___________ are absorbed, the remaining contents form feces (mostly
cellulose, bacteria, bilirubin).
• __________________ in the large intestine, such as E. coli, ________________ __________________
(including vitamin K) that are absorbed.
• The large intestine absorbs water and dissolved minerals from the indigestible food residues, and by
doing so converts what remains from a fluid state into a semi-solid feces
• The feces is stored in the rectum and eliminated out the anus
There are 3 parts to the Colon
1.
2.
3.
Accessory Digestive Organs
Salivary Glands
 ___________________________________
 Parotid glands – located anterior to ears
 Submandibular glands
 Sublingual glands
Saliva
 Mixture of mucus and serous fluids
 Helps to form a _____________________
 Contains salivary __________________ to begin
_________________________________
 Dissolves chemicals so they can be tasted
Teeth
 The role is to ___________________ (chew) food
 Humans have two sets of teeth
 Deciduous (baby or milk) teeth
 20 teeth are fully formed by age two
 Permanent teeth
 Replace deciduous teeth beginning between
the ages of 6 to 12
 A full set is ________________, but some
people do not have wisdom teeth
The Pancreas
 Produces a wide spectrum of digestive enzymes that break down _______________________________
 Enzymes are secreted into the duodenum
 Alkaline fluid introduced with enzymes neutralizes acidic chyme
 Endocrine products of pancreas
 ________________________________
 ________________________________
•
•
When the acidic chyme is pushed out of the stomach into the small intestines. IT simulates the pancreas
to send ________________________, which neutralizes the ________________, begins digestions of
Carbohydrates, Lipids and continues digestion of protein.
Pancreatic juice also contains ____________ which digests _________________
_____________________.
The Liver
 _____________________________________ in the body
 Located on the right side of the body under the diaphragm
 Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament
 Connected to the gall bladder via the common hepatic duct
Role of the Liver in Metabolism
 Several roles in digestion
 ________________________________________
 ________________________________________
 ________________________________________
 Plays a central role in metabolism
The Gall Bladder
 Sac found in hollow fossa of liver
 Stores
___________________________________ by
way of the cystic duct
 Bile is introduced into the
__________________________ (small intestine)
in the presence of fatty food
 _______________________ can cause blockages
The Liver and Gall Bladder
• The Liver makes _____________ and stores it in the ______________________.
• The Gall bladder _______________________________________________ when the acidic chyme
from the stomach. Bile contains bile salts, which ____________ fats, making them susceptible to
enzymatic breakdown.
• The liver also stores excess __________________ in the form of ______________________.
Processes of the Digestive System
1. Digestion
• There are three major parts to digestion:
• Digestion Part 1
• _______________________: process of using smooth and skeletal muscles in the
mouth, tongue, and pharynx _____________________________, through the
pharynx, and into the __________________________.
• Digestion Part 2
• _______________________: a ______________________ that travels the length
of the GI tract, _________________________________ a short distance down
the tract. It takes many waves of peristalsis for food to travel from the esophagus,
through the stomach and intestines, and reach the end of the GI tract.
•
Digestion Part 3
• _______________________: occurs only in the small intestine as ____________
___________________________ like hands squeezing a toothpaste tube.
Segmentation helps ___________________________________ by mixing food
and increasing its _____________________________________.
_____________________________ digestion
• Mixing of food in the mouth by the tongue
• __________________________________
• Segmentation in the small intestine
• __________________________________ breaks
fats into smaller globules
______________________________digestion
• Begins in ________________ (saliva), continues in
________________ (enzymes and acids), most
occurs in ______________________ (pancreatic
juices secreted into S.I. by pancreas)
• _______________________ break down food
molecules into their building blocks
• Each major food group uses different enzymes
• Carbohydrates are broken to ____________
______________
• Proteins are broken to _________________
• Fats are broken to ___________________
and alcohols
• Water is degraded into hydrogen and oxygen
2. Absorption
 ___________________________________________
__________________________________________
 Begins in __________________________, ends in
__________________________
 Stomach: __________ and alcohol
 Small intestine: ________________________
____________________________________
 Large intestine: ____________________ and vitamins B and K
3. Defecation/Excretion
 ____________________________________________________________________________
 Controlled _____________________________but must be accomplished on a regular basis
 The following compounds are not absorbed, but rather defecated
 B________________________ (bilirubin)
 E________________________ of the intestinal lining
 L________________________ (found in root vegetables, wheat, and berry seeds)
 C________________________ (found in bran, legumes, nuts, peas, roots, cabbage and apple
skins)
 H________________________ / bacteria
Control of Digestive Activity
 Relationship between Digestive System and Nervous system:
 Mostly controlled by reflexes via the _____________________________ division
 __________________ and ____________________ receptors are located in organ walls that
trigger reflexes