Animal Nutrition

1
Animal Nutrition

• With a side bar on the animal kingdom!

2
Animal Phylogeny

• P.640 32.8

3
Why Digest?

• Makes food available to cells
• May be intracellular-within each individual cell
• May be extracellular-enzymes are released and
  food is prepared for all cells.

4
Intracellular is primitive

• Porifera Picture

Phylum Porifera
5
Extracellular with one body opening and
gastrovascular cavity

• Cnidaria cross section

• Planaria cross section

Phylum Platyhelminthes
Phylum Cnidaria
6
Extracellular with one way digestive tract (have
mouth and anus)

• Nematode Pix

• Annelids

• Annelid cross section

Phylum Nematoda
Phylum Annelida
7
Animals are group based on food source

• Carnivores- eat meat-shorter intestine, pointed
  teeth.
• Omnivores- eat meat and plants, teeth like
  carnivore in front and herbivore in back.
• Herbivores- eat plants, longer intestine, large
  flat teeth to break up plant tissue. Long very
  specialized digestive tract.

• Bear Pix

8
Herbivore modifications

• 41.22

9
Specialized Actions

• Mechanical-teeth, grinding(pebbles in bird and
  earthworm gizzards), churning.
• Chemical-hydrolysis by enzymes
• ExSalivary amylase
• Source-salivary gland
• Substrate-starch-a polysaccaride
• Product-maltose- a disaccaride

10
Human Digestive System
Food moves by peristalsis

• Digestive System Pix

11
Accessory Organs
Liver-produces bile Gallbladder-stores and
concentrates bile Pancreas-produces pancreatic
juice (both enzymes and bicarbonate)

• 41.16

12
Stomach-Site of Protein Digestion

• Convoluted
• Secretes Gastric Juice-acidic secretions of
  gastric glands of mucosa
• Two cell types-
• Parietal-HCl
• Chief-pepsinogen-activated in low pH-to form
  pepsin

• 41.15

• Low pH denatures proteins
• Protein digestion finished in small intestine
• Output from stomach-chyme

13
Protein Digestion
Pepsin Source-chief cells as pepsinogen Substra
te-protein Product-polypeptides Optimum
pH-2 Trypsin Source-pancreas as
trypsinogen Substrate- polypeptide Product-am
ino acids Optimum pH-neutral

• 41.18

14
Small Intestine-

• Carbohydrate, lipid, protein digestion finished.
• Everything absorbed (exceptions-aspirin, alcohol,
  water -absorbed in stomach)
• First 25 cm-duodenum-receives secretions from
  pancreas, gall bladder.
• Then jejunum
• Then ileum

• 41.21

15
Structure of the GI Tract
Inner mucosa-epithelium Submucosa-connective Muscu
laris-double layer of smooth muscle Serosa-more
connective tissue

• 41.19

16
SI Absorption

• 41.19

Brush Border-where a.as and monosacs are
transported into the epithelial cells, across
membranes and into blood capillaries within the
villi. From here carried to the
liver Fat-hydrolyzed, absorbed, reassembled into
triglycerides. Triglycerides combine with protein
to form chylomicrons-absorbed into lymphatic
system-empties into veins near the neck.
17
Large Intestine

• Large in diameter
• Joins SI near two vestigial organs
• Appendix and cecum
• Vitamin K made by microorganism here and
  absorbed.
• Bacteria ferment here- produce gas
• Low fiber diets-food moves slowly-associated with
  high colon cancer rates

18
Pancreas

• Secretes Pancreatic juice-enters duodenum through
  the pancreatic duct. Contains
• Trypsin-protein
• Chymotrypsin-protein
• Pancreatic amylase-starch
• Lipase-fat
• Bicarbonate-neutralizes HCl makes alkaline
• Secreted as zymogens-inactive enzymes
• Activated by brush border enzymes
• Digestion is completed by brush border enzymes

19
Liver

• Largest internal organ
• Secretes bile
• Bile pigment-from RBCs-no digestive role-too
  much jaundice
• Bile salts-work like detergent to emulsify
• Stored in gall bladder-fatty food triggers
  release
• Regulatory
• Metabolizes drugs, alcohol
• Removes steroid hormones
• Produces most blood proteins
• Regulates blood glucose-stored in liver as
  glycogen, used up-does gluconeogenesis

20
Regulation of digestion

• Coordinated by nervous/endocrine
• Sight/smell-nervous
• Food in stomach-release of gastrin-causes release
  of gastric juices
• Hormones control passage of food into
  duodenum-high fat slows passage
• Duodenum secretes CCK in response to fat-causes
  bile release
• Secretin-causes pancreas to release bicarbonate