Digestion

1
Digestion

• Digestive system and Organs involved
• Digestive Enzymes
• Accessory Organs for Digestion
• Nutrition

2
Digestive system

• Consists of Gastrointestinal (GI) tract or
  alimentary canal and attached accessory organs
• about 25 feet long mostly in abdominal cavity

3
(No Transcript)
4
Mouth

• Site of ingestion the entrance
• Mixing and propulsion (tongue)
• Mastication (teeth)-reduce size of food and
  increase surface area
• Digestion begins (saliva from salivary glands)

5
Tongue
Filiform papillae
1. Chemoreceptors taste food 2. Skeletal
muscles Mastication 3. Secretions Amylase for
CHO digestion and Antibiotics for Cleaning
6
Teeth

• Dental Formula
• Primary Milk teeth 212
• 2 Incisors 1 Canine 2 Premolars
• Permanent teeth 2123
• 2 Incisors 1 Canine 2 Premolars 3 Molars

7
Mouth

• Tongue and Teeth mix up food to a gooey mass
  called BOLUS
• easier to pass through the alimentary canal
• First site of carbohydrate digestion
• 3 pairs of Salivary glands secrete enzyme
  Salivary Amylase
• Starch Maltose

Salivary amylase
8
Pharynx

• Common passageway for both food and air
• Either breathe or eat !!!

9
Epiglottis
Windpipe
Esophagus
10
Peristalsis

• Involuntary muscular contractions that mix and
  move food through gastrointestinal (GI) tract

11
Esophagus

• Connects pharynx and stomach
• propels food by peristaltic waves to stomach
• Plays no role in chemical digestion

12
Stomach

• Gastric glands producing Gastric juice
• Gastric juice Pepsin (enzyme) HCl (acid)
• pH 2 Inhibits microbial growth
• First site of Protein digestion
• Protein Polypeptides

Pepsin
Amino Acids
13
Helicobacter pylori (bacteria) responsible for
95 of ulcers
14
Stomach

• Capacity of holding 1-3 liters (about 3 quarts)
  of food
• Food material is mixed and churned 2-6 hrs
• Produces semi-liquid called CHYME

15
Stomach
Expandable membrane fold
16
(No Transcript)
17
Gastrointestinal (GI) tract

• Interior called lumen
• Wall has 4 layers
• Mucosa-inner lining absorbs, secretes, protects
• Submucosa-connective tissue contains blood
  vessels, lymph vessels, nerves
• Muscularis-contains smooth muscle (long and circ
  layers) mix and move food
• Serosa-outer layer connective tissue mesenteries

18
Stomach sphincters(smooth muscle)

• Esophageal or Cardiac sphincter
• junction of esophagus and stomach
• regulates entry of food into stomach
• Stomach contents move up the esophagus
• Oops!!! I have a heart burn.
• I feel sick to my stomach, whoa!!!!!! Im
  throwing up!!!!!!

19
Stomach sphincters(smooth muscle)

• Pyloric sphincter
• Regulate the flow of chyme into the small
  intestine.

20
Small intestine

• 18 feet
• Duodenum Jejunum - ileum
• Duodenum
• Secretions from the liver
• Bile emulsifies fat- causes fat droplets to
  disperse in water (not an enzyme)
• From the pancreas
• Sodium bicarbonate neutralizes chyme

21
Small intestine
Villi
Lumen
x45
22
(No Transcript)
23
(No Transcript)
24
Villus

• Nutrients are absorbed in the villus
• sugar and aminoacid molecules directly diffuse
  across
• Fats Fatty Acid Glycerol
• (Fatty Acid Glycerol Protein) Lipoprotein
• It contains a lacteal

Enters
25
Small Intestine

• Gastrin
• Secreted from the stomach
• control of gastric acid secretion.
• Cholecystokinin
• small intestinal hormone
• stimulates secretion of pancreatic enzymes and
  bile
• Secretin
• secreted from small intestinal epithelial cells
• stimulates secretion of a bicarbonate-rich fluids
  from the pancreas and liver.

26
Jejunum microvilli
x61,765
27
Jejunum blood circulation
x180
28
Digestion Absorption
Intestinal lunen
Materials remain in the small intestine for a
period of 5-6 hours
Epithelial cell
Blood capillary
29
Large Intestine

• No chemical digestion
• Digestion and absorption near complete by time
  chyme reaches large intestine
• formation of feces and conservation of water
• about 90 of water in chyme is absorbed
• resident bacteria give off valuable by-products
  we could not produce alone
• (ex.) vitamin K (blood clotting)

30
Large Intestine

• Absorption of water formation and storage of
  feces (5 foot long)
• Remains in the LI for 12-24 hours
• 4 parts
• Cecum-
• short pouch that receives chyme from SI
• movement controlled by one-way valve
• appendix-function unknown

31

• Colon
• resident bacteria digest material in chyme that
  was not digested by SI
• Vitamin K and some B complex vitamins are
  produced by bacteria
• Rectum
• stores feces
• Anus
• feces expelled through anal canal and out anus

32
FYITotal volume of food and water 2 liters

• Body adds 7 liters of its own fluids
• 1.5 liters salivary enzymes
• 2.0 liters of gastric secretions
• 1.5 liters of pancreatic secretions
• 0.5 liters of bile
• 1.5 liters of intestinal secretions

33
Nearly all fluids and solids are absorbed

• 8.5 liters reabsorbed into small intestine
• 350 millimeters reabsorbed in the large intestine
• Only 50 grams of solids and 100 milliliters of
  liquid leave as feces.
• Fluid absorption efficiency 99