2. Digestion
the breakdown of food into simpler
compounds and their absorption
2 Types of Digestion
1. Physical or Mechanical
- the breakdown of food from big
pieces into smaller pieces
2. Chemical
- the breakdown of food into their
simplest substance
3. mouth
salivary
glands
pharynx
esophagus
stomach
liver
small intestine
gall
bladder
pancreas large intestine
rectum
anus
7. Mouth
- begins the physical digestion (chewing)
of food
Parts of the Mouth
1. Cheeks
2. Lips
3. Tongue
- contains the taste buds
- connected to mouth by frenulum
4. Hard palate
8. 5. Soft palate
- a muscular partition that closes off
the nasal cavity when swallowing
6. Uvula
- the little hangy thing in back of
the mouth
7. Teeth
- 20 deciduous
- 32 permanent
12. Salivary Glands
- secretes saliva
- moistens food which makes taste possible
- cleans the mouth
Salivary Secretions
- there are 2 types of cells in salivary glands
1. Serous
- produces salivary amylase
2. Mucous
- produces mucus
14. Digestion in the Mouth
Mastication – chewing of food begins
physical digestion
- salivary glands release salivary amylase
which begins chemical digestion
of carbohydrates
15. Pharynx
- involved in the swallowing reflex
3 Parts of the Pharynx
1. Nasopharynx
2. Oropharynx
3. Laryngopharynx
- once food moves into the pharynx, the
reflex causes the epiglottis to cover the
trachea & push the food into the
esophagus
16. Esophagus
- 25 cm long, leads into the stomach
- begins the process of peristalsis
wave-like motion
of muscles to
move food
17. Stomach
Functions
- begins protein digestion
- stores food
- completes physical digestion of food
4 Parts of the Stomach
1. Cardiac Region
2. Fundic Region
3. Body
4. Pyloric Region
18.
19. Gastric Glands
4 Types of cells
a. mucous cells
- produce mucus
b. parietal cells
- produces HCl
- produces Intrinsic factor
- helps absorb Vit. B12
20. c. chief cells
- produce pepsinogen
d. G-cells
- produce gastrin
21. Digestion in the Stomach
1. Physical
- peristaltic waves pass over the stomach
every 15-25 seconds
- this wave action blends the food into a
soupy substance called chyme
2. Chemical
- pepsinogen changes into active pepsin
in the presence of HCl
- breaks proteins down into polypeptides
22. Gastric Absorption
- some water
- ions
- short fatty acids
- certain drugs (aspirin)
- alcohol
23. Regulation of Gastric Secretions
1. Cephalic Phase
- when you see, smell, think about, or
taste food, the brain tells the gastric
glands to produce gastric juices
2. Gastric Phase
- when food enters the stomach, it
expands, gastrin is released
- gastrin causes the release of
gastric juices from the gastric glands
24. 3. Intestinal Phase
- when chyme enters sm. int., 2 hormones
are produced by the intestinal glands,
secretin & CCK
- secretin decreases gastric secretions and
CCK keeps too much food from
entering the stomach
Gastric secretion movie
26. 2 Types of Cells
1. Islets of Langerhans
- produce insulin & glucagon
2. Pancreatic Cells
- secrete pancreatic juices
27. Pancreatic Juice
- is a basic solution to neutralize the chyme
- contains the following enzymes
- pancreatic amylase - carbs
- pancreatic lipase - lipids
}
- trypsin
- chymotrypsin
proteins
- carboxypeptidase
- pancreatic nuclease - nucleic acids
Regulation of Pancreas
- secretin & CCK causes the release of
pancreatic juices into the sm. int.
28. Liver
Functions
- carbohydrate metabolism
- lipid metabolism
- protein metabolism
- removes damaged RBC’s
- removes toxins
- makes bile
29. Structure of Liver
- 2 lobes
- lobes are divided into hepatic lobules
- 100,000 – 200,000
Hepatocyte
30. Bile
- made by hepatocytes
Function
- emulsifies fat
breaks big fat globules into small
fat globules
Regulation
- constantly made by liver cells
- nerve impulse can trigger bile
production
31. Gall Bladder
- stores excess bile from the liver
- releases bile when CCK is present
33. Structure of Sm. Intestine
- mucosa forms finger-like projections
called villi
- each villus contains absorptive cells
that have microvilli on them
- goblet cells produce mucus
- the lacteal is a lymph capillary that
involves fatty acid absorption
- intestinal glands secrete intestinal
juices
34.
35. Functions of the Small Intestine
1. Segmentation mixes chyme with digestive
juices, peristalsis moves food through
sm. int.
2. Completes chemical digestion of food
3. Absorbs 90% of all nutrients
36. Chemical Digestion in the Small Intestine
1. Carbohydrates
- pancreatic amylase breaks down
polysacccharides
- sucrase, lactase, & maltase made by
the intestinal glands breaks down
disaccharides into monosaccharides
37. 2. Proteins
- aminopeptidase and dipeptidase made
by the intestinal glands breaks down
polypeptides into amino acids
3. Lipids
- pancreatic lipase splits the fatty acids
from the glycerol
4. Nucleic Acids
- pancreatic nuclease and intestinal
nuclease breaks down RNA & DNA into
nucleotides
45. Funtions
- absorption of water and electrolytes
- contain bacteria that changes waste
into a semi-solid and produces
some Vit. K
- NO DIGESTION OCCURS IN THE
LARGE INTESTINE
46. FECES!
- 75% water
- bacteria
- mucus
- undigested food
- bile
- bile pigments
- cellulose (fiber)
47. Nutrients
carbohydrates
lipids
proteins
vitamins
minerals
trace elements
Adequate diet – provides sufficient energy
and nutrients to support optimal
growth and to maintain and repair
body tissue
