Digestive Systems in Animals

Digestive Systems

• Different types of digestive systems found in animals:
  • Monogastric: one-chambered stomach (e.g. humans, dogs, cats)
  • Polygastric: multi-chambered stomach (e.g. cows, sheep, goats)
  • Avian: specialized digestive system with crop and gizzard (e.g. birds)
• Functions of the digestive system:
  • Ingestion: taking in food
  • Digestion: breaking down food into smaller molecules
  • Absorption: absorbing nutrients into the bloodstream
  • Elimination: removing waste products

Digestion in Cows

• Ruminant digestive system: cows have a four-chambered stomach
  • Rumen: first chamber, where food first enters and is broken down by microbes
  • Reticulum: second chamber, where food is further broken down
  • Omasum: third chamber, where water and nutrients are absorbed
  • Abomasum: fourth chamber, similar to the human stomach
• Digestive process in cows:
  • Food enters the rumen, where microbes break down cellulose in plant cell walls
  • Volatile fatty acids (VFAs) are produced as a byproduct of microbial fermentation
  • VFAs are absorbed and used as energy by the cow
  • microbes in the rumen also synthesize amino acids and vitamins
  • Food then passes through the remaining chambers, where further digestion and absorption occur

Digestive Systems

• Digestive systems in animals vary, with three main types:
  • Monogastric: one-chambered stomach, found in humans, dogs, and cats
  • Polygastric: multi-chambered stomach, found in cows, sheep, and goats
  • Avian: specialized digestive system with crop and gizzard, found in birds
• Key functions of the digestive system include:
  • Ingestion: taking in food through the mouth
  • Digestion: breaking down food into smaller molecules through mechanical and chemical means
  • Absorption: absorbing nutrients into the bloodstream for use by the body
  • Elimination: removing waste products from the body

Ruminant Digestive System in Cows

• Cows have a four-chambered stomach, known as the ruminant digestive system:
  • Rumen: first chamber, where food first enters and is broken down by microbes
  • Reticulum: second chamber, where food is further broken down
  • Omasum: third chamber, where water and nutrients are absorbed
  • Abomasum: fourth chamber, similar to the human stomach
• The digestive process in cows involves:
  • Microbial fermentation in the rumen, where microbes break down cellulose in plant cell walls
  • Production of volatile fatty acids (VFAs) as a byproduct of microbial fermentation
  • Absorption of VFAs, which are used as energy by the cow
  • Synthesis of amino acids and vitamins by microbes in the rumen
  • Further digestion and absorption in the remaining chambers

Nutrient Absorption

• Nutrient absorption occurs in the small intestine through diffusion, active transport, and facilitated diffusion.
• Diffusion involves the movement of nutrients from an area of high concentration to an area of low concentration.
• Active transport involves the movement of nutrients against their concentration gradient using energy.
• Facilitated diffusion involves the movement of nutrients through transport proteins in the cell membrane.

Digestive Systems

• There are three types of digestive systems: monogastric, polygastric, and avian.
• Monogastric digestive systems have a one-chambered stomach and are found in humans, pigs, and horses.
• Polygastric digestive systems have a multi-chambered stomach and are found in ruminants such as cows and sheep.
• Avian digestive systems are specialized and found in birds.
• The digestive system performs three main functions: mechanical breakdown, chemical breakdown, and absorption of nutrients.

Digestion in Humans

• The digestive process in humans involves five stages: ingestion, swallowing, gastric digestion, small intestine, and large intestine.
• Ingestion involves food entering the mouth where it is chewed and mixed with saliva.
• Swallowing involves food being swallowed and passing through the esophagus into the stomach.
• Gastric digestion involves food being mixed with stomach acid and digestive enzymes in the stomach.
• The small intestine is where nutrients are absorbed into the bloodstream.
• The large intestine is where water and electrolytes are absorbed, and waste is eliminated.

Acids Used in Small Intestine

• Bile acids are produced in the liver and stored in the gallbladder.
• Bile acids are released into the small intestine to emulsify fats and facilitate fat absorption.
• The main bile acids are cholic acid, chenodeoxycholic acid, and deoxycholic acid.
• Pancreatic juice is produced in the pancreas and released into the small intestine.
• Pancreatic juice contains digestive enzymes such as amylase, lipase, and trypsin.
• The pH of pancreatic juice is alkaline, helping to neutralize acidic chyme from the stomach.

Stomach

• The stomach performs three main functions: mechanical breakdown, chemical breakdown, and secretion of mucus.
• Mechanical breakdown involves the muscular contractions of the stomach.
• Chemical breakdown involves the release of gastric enzymes that break down proteins.
• The stomach secretes mucus to protect the stomach lining from acid and enzymes.
• Gastric acid is produced by parietal cells in the stomach lining.
• The pH of gastric acid is acidic, ranging from 1.5 to 3.5.
• Gastric acid helps to denature proteins and activate digestive enzymes.