Animal Nutrition

• All animals (humans included) are heterotrophic organisms that are dependent on other organisms for their organic nutrients.
• Five Main Processes In Nutrition:

  1. Ingestion: the food is taken in and entere the alimentary canal.
  2. Digestion: food is exposed to mechanical and chemical processes that change solid, insoluble food to simpler, soluble substances.
  3. Absorption: the end products of digestion are absorbed into the bloodstream.
  4. Assimilation: the cells absorb the nutrients from the blood and use it to build new cell structures and compounds.
  5. Egestion: the process through which undigested remains are removed from the body in the form of faeces.
• Necessity Of Food:

  • Provides energy
  • Growth and repair of damaged tissues
  • Regulation of body processes
• Animals are classified into three groups according to the food they eat, herbivores, carnivores and omnivores.
• Herbivores 


  Large volumes of food are ingested, as plant material has a very low energy value.

  Herbivores teeth are adapted in the following ways: incisors are sharp to cut off plant material, canines/fangs are often absent, premolars and molars are large and flat to grind plant material.
• Carnivores 


  Carnivores ingest less food than herbivores, as the proteins and fats in meat have a much higher energy value then plant material.

  Petite are adapted to hold and tear off pieces of meat in the following ways: incisors have sharp ends to bite off food, canines/fangs are long and strong to pierce, kill and tear prey apart, premolars and molars have protrusions with sharp edges to cut off the food.
• Omnivores 


  The amount of food omnivores consume depends on the energy value of the food they eat.

  Omnivores teeth are very similar to dose of carnivores, except that the molars do I have such prominent protrusions.

  Boss baboons and pigs poses weldeveloped k9/fans which are used mainly for self-defense and social display (baboons).
• The human digestive system consists of alimentary canal and accessory organs.
• The alimentary canal is a long, tubular structure the extends throughout the body. It consists of:

  • Mouth and mouth cavity
  • Pharynx
  • Oesophagus
  • Stomach
  • Small Intestine
  • Large Intestine and Anus
• Accessory Organs:

  • Tongue
  • Salivary glands
  • Pancreas
  • Liver
  • Gall Bladder
• Mouth and mouth cavity

  • Upper opening of alimentary canal.
  • Opening is surrounded y two fleshy lips.
  • Lined with a mucous membrane
  • Roof consists of hard rigid palate at the front and a soft palate at the back.
  • Soft palate ends in the uvula, which closest opening of the nasal cavity when swallowing.
  • Contains a tongue and teeth toward the front as well as the openings of the three pairs of salivary glands.
• Mouth and Mouth cavity Function 


  Receives food and begins the process of mechanical digestion by breaking down larger particles of food into smaller particles and mixing it with saliva.
• Pharynx

  • Get back of the mouth cavity opens the pharynx
  • Leads to two openings, the esophagus, the trachea (windpipe)
• Pharynx function 


  Is the common passage for food and air from the mouth to the oesophagus and the trachea.
• Oesophagus

  • Is a hollow, muscular tube that connects the pharynx to the stomach.
• Oesophagus Function

  The muscles in the wall of the oesophagus are responsible for peristalic movements, which push the food bolus forward.
• Stomach

  • Is a sickle shape, sack like organ that is located just below the diaphragm.
  • Wall is thick and muscular
  • At the top, the opening to the oesophagus is closed by the cardiac sphincter
  • The lower end, the opening to the small intestine is closed by the pyloric sphincter
• Stomach Functions 


  The muscular war causes churning movements the assist with physical digestion and also ensure that the food is mixed with the gastric juices.

  The gland in the stomach wall secret gastric juices for digestion.
• Small Intestine

  • Is a long, muscular tube of approximately 5 m to 6 m long.
  • Consists of three parts; duodenum, jejunum, ileum.
  • The wall consists of four layers; serous membrane, a muscle layer ( longitudinal muscles, circular muscles), submucosa, mucosa.
• Parts Of Small Intestine

  Duodenum:

  • First and shortest part
  • The common bile duck from the gall bladder and the pancreatic duct from the pancreas open as a joint tube in the duodenum.

  Jejunum:

  • The middle part

  Ileum:

  • The last and longest part
  • Joins the first part of the large intestine (caecum)
  • Opening between ileum and caecum is closed by a ring muscle ( ileo-caecal sphincter)
• Layers Of Small Intestine Wall

  Serous Membrane:

  • Outer connective tissue layer.

  Muscle layer:

  • Longitudinal muscles, outer layer
  • Circular muscles, inner layer

  Submucosa:

  • Layer of connective tissue with blood vessels, lymph vessels, nerves and glands

  Mucosa:

  • Inner most layer
  • Has transverse folds
  • Millions of finger-like projections (villi), on these folds.
• Structure Of Villus

  • Is surrounded by a single layer of columnar epithelial cells.
  • In the columnar epithelium there are goblet cells that secrete mucus
  • On the surface of columnar epithelium cells are microscopic projections called microvilli.
  • In the center is a capillary lymph vessel (lacteal)
  • An arterial brings blood to the villas and forms a capillary network that surrounds the lacteal.
  • At the base are small cavities known as crypts of Lieber Kuhn
  • Brunner glands occur in the submucosa of duodenum
• Small Intestine Functions 


  Layers of muscle in the wall causes paristaltic movements, which move chyme forward and ensures that it becomes thoroughly mixed with digestive juices

  Glance in duodenal wall (crypts of Lieber Kuhn and Brunner glands) secretendigestive juices, which you play a role in digestion.

  Has millions of villi o increase the surface area for absorption of digestive nutrients.
• Large intestine


  Has three parts:

  Caecum

  • Sac-like structure where it joins the small intestine
  • A small appendage is attached, the appendix

  Colon

  • Largest part
  • Consists of ascending, transverse and descending colon

  Rectum

  • Large muscular portion of large intestine
  • Ends with an opening on the outside, the anus.
• Large Intestine Functions 


  Secretes large amounts of mucus to aid egestion

  Water and useful substances (certain vitamins and bile salts) are absorbed from the semi-solid waste in the colon

  Undigested waste (faeces) is stored temporarily in the colon before it is egested via the anus.