Transcript Digestive (2)_student - tran-bio3u

Digestion - a mechanism
Recall
Pica
http://edition.cnn.com/2004/
HEALTH/02/18/coin.eater.ap
/index.html
Parts of the Digestive System
The MOUTH
Incisors:
slicing and gripping
The sharp teeth at the front of
the mouth (four on the top and
four on the bottom) that are
specialized for cutting
Canines:
ripping and tearing
Total of four
Premolars
(bicuspids):
Biting and tearing
A tooth having two cusps or points;
located between the incisors and
the molars
Molars:
grind food
Including the wisdom teeth,
adults have twelve molars —
six on the top and six on the
bottom.
Tongue:
a large muscle that mixes food
with saliva and pushes food back
to top of the throat
Salivary Glands
- release enzymes that initiate the
chemical digestion of starch into
smaller polysaccharides.
- secrete saliva made of two
secretions from two types of glands:
1) Parotids --> Amylase
2) Buccal glands
(Sublingual and submandibular) -(glycoprotein mucin)
Cells that line the esophagus also
secrete mucus
The Pharynx
▪ Located at the back of the throat
▪ Guides the food from the oral
cavity into the esophagus (food
tube) Food --> esophagus
▪ Guides the air from the nasal
cavity to the trachea (air tube)
▪ Air --> trachae
Act of Swallowing
1. The tongue rolls up the food into a bolus
2. Pushes the bolus towards the back of the throat and the soft
palate/uvula combination closes over the nasal cavity
The Esophagus
Peristalsis
http://www.coolschool.ca/content/showcase.php?type=science
X-ray of the Esophagus undergoing peristalsis
Cardiac sphincter
http://www.biocourse.com/mhhe/bcc/domains/quad/topic.xsp?id=000270
The Stomach
Stomach: 4 basic functions
 Short-term storage reservoir (adult capacity 1500mL)
 Protein synthesis (HCL converts pepsinogen to pepsin and
this breaks down protein)
 Liquefaction of food --> chyme
 Slowly released into the small intestine
The stomach absorbs very few substances, although
small amounts of certain lipid-soluble compounds can
be taken up, including aspirin, other non-steroidal
anti-infammatory drugs, and ethanol
http://www.coolschool.ca/content/showcase.php?type=science
Structure of the Stomach Mucosa
Mucous cells: Alkaline mucus protects the skin against
shear stress and acid
Parietal cells: Secretes hydrochloric acid
Chief cells: Secretes pepsinogen (which will be converted
to pepsin)
Gastric cells: Secretes gastrin (stimulates digestive action)
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html
Cephalic Phase
Wake up call
Gastric Phase
“full steam ahead”
Intestinal phase
"step on the brakes"
Home work:
What it is and why …
Nausea -
Retching -
Vomition GastroLab images
http://www.gastrolab.net/welcomee.htm