objective: you will be able to identify the structures of the digestive system. do now: read page...
TRANSCRIPT
Objective: You will be able to identify the structures of the digestive system.
Do Now:• Read page 978
• List the accessory organs
Figure 41.12 The four stages of food processing
Piecesof food
Smallmolecules
Mechanicaldigestion
Food
Chemical digestion(enzymatic hydrolysis)
Nutrient moleculesenter body cells
Undigested material
INGESTION1 DIGESTION2 ELIMINATION4ABSORPTION3
Figure 41.13 The human digestive system
Activity• For each digestive organ you need to:
– Locate in pig and cut out if possible– Draw organ and outline its digestive
functions FULLY– Write down any disorders that you can
think of that would be associated with each organ.
• Use laptop to find and describe a disorder for that organ. Be sure to include how the disorder is related to its function.
Oral Cavity
• Mechanical digestion breaks food into smaller pieces– Increases surface area for chemical digestion
• Chemical digestion of starch occurs here– Done by salivary amylase
Esophagus
• No digestion occurs here
• It moves food from oral cavity to stomach by using muscles– Called peristalsis
Esophagus
Tongue
Pharynx
GlottisLarynx
Trachea
Bolus of food
Epiglottisup
To lungs To stomach
Esophageal sphinctercontracted
Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)
Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2)
Esophagus
Epiglottis down
Tongue
Pharynx
GlottisLarynx
Trachea
Bolus of food
Epiglottisup
To lungs To stomach
Esophageal sphinctercontracted
Glottis upand closed
Esophageal sphincterrelaxed
Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3)
Esophagus
Epiglottis down
Tongue
Pharynx
GlottisLarynx
Trachea
Bolus of food
Epiglottisup
To lungs To stomach
Esophageal sphinctercontracted
Glottis upand closed
Esophageal sphincterrelaxed
Glottisdown and open
Esophageal sphinctercontracted
Epiglottisup
Relaxedmuscles
Contractedmuscles
Relaxedmuscles
Pepsin (active enzyme)
HCl
Parietal cellChief cell
Stomach
Folds of epithelial tissue
Esophagus
Pyloric sphincter
Epithelium
Pepsinogen
3
2
1
Interior surface of stomach.The interior surface of the
stomach wall is highly folded and dotted with pit leading into tubular gastric glands.
Gastric gland. The gastric glands have three types of cells
that secrete different components of the gastric juice: mucus cells,
chief cells, and parietal cells.
Mucus cells secrete mucus,which lubricates and protects
the cells lining the stomach.
Chief cells secrete pepsino-gen, an inactive form of the
digestive enzyme pepsin.
Parietal cells secretehydrochloric acid (HCl).
1 Pepsinogen and HCIare secreted into thelumen of the stomach.
2 HCl convertspepsinogen to pepsin.
3 Pepsin then activatesmore pepsinogen,starting a chainreaction. Pepsinbegins the chemicaldigestion of proteins.
5 µ
mSmall intestine
Cardiac orifice
Stomach
• Mechanical digestion occurs by the grinding of the stomach’s muscles
• Chemical digestion of proteins begins here– Gastric glands in stomach release a HCl and
protease – The HCl provides a highly acidic environment– The protease actually breaks down the
protein
Figure 41.19 The duodenumLiver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
Small Intestine• Lipid digestion starts here
• Most of the chemical digestion occurs here– Intestinal glands and the accessory organs
help to digest food• Liver, gall bladder and pancreas
• All of the absorption of food into the body occurs here
• No food is digested AFTER it leaves the small intestine
Figure 41.19 The duodenumLiver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
Accessory organs
• The liver makes the bile but it stores it in the gall bladder
• It’s the gall bladder that actually secretes bile into the small intestine– Bile emulsifies fats (breaks them down)
• The pancreas secretes amylase, protease and lipase
Figure 41.19 The duodenumLiver Bile
Acid chyme
Stomach
Pancreatic juice
Pancreas
Intestinaljuice
Duodenum of small intestine
Gall-bladder
Large Intestine
• This organs main function is to absorb water
• It does NOT absorb food nor does it digest food!!!!
End of the line
• Strong peristaltic action from the rectum pushes waste out of the anus
Activity• Create story about the digestive canal of
horrors where a group of teenage worm friends enter ride but are digested by enzymes
• Remember that only some of carbohydrate and protein digestion happens outside intestines
• Be sure to include each structure and describe in full detail what they do.
Figure 41.18 Ulcer-causing bacteria
1 µ
m
Bacteria
Mucuslayer of stomach
Disorders of the Digestive System
• Ulcers are erosions of the digestive tract
• Appendicitis is the infection and inflammation of the appendix
• Gallstones is the accumulation of hardened cholesterol deposits on the gall bladder
Disorders continued
• Constipation occurs when the large intestine absorbs too much water
• Diarrhea occurs when the large intestine does NOT absorb enough water