Animal Nutrition & Digestion

• All living organisms need food for energy and nutrients that are essential for life maintenance.
• The energy stored in food powers vital activities like movement, growth, tissue repair, reproduction, and synthesis of new cell protoplasm.

Metabolism

• Encompasses all the chemical reactions occurring within an organism's body.

Nutrition

• Concerns the intake of food from various sources and the processes converting food substances into living matter.

Animal Nutrition

• Autotrophs produce their own food by converting inorganic components into organic molecules.
• Heterotrophs obtain nutrition by consuming organic molecules from other organisms.
• Herbivores consume plants.
• Carnivores consume meat.
• Omnivores consume both plants and meat.
• Detritivores consume dead organic matter.

Types of Digestive Systems in Animals

Intracellular Digestion

• It is common in single-celled organisms.
• Food is processed inside the cell, specifically within food vacuoles.

Extracellular Digestion

• Digestion occurs outside of cells, inside a digestive cavity found in multicellular organisms.
• Nutrients are absorbed into the bloodstream following the breakdown within digestive cavity.
• Amoebas and paramecium digest in this manner.

Extracellular Digestion

• Food is broken down outside the cells.
• The forms are:
• Incomplete Digestive System
• Complete Digestive System

Incomplete Digestion

• Animals with simple body plans contain a digestive compartment with a single opening.
• The gastrovascular cavity serves in both digestion and distribution of nutrients throughout the body.

Complete Digestion

• More specialized animals developed complex alimentary canals containing one-way tubes with distinct openings for the mouth and anus.

Foregut Fermentation

• It is one method of digestion.

Hindgut Fermentation

• It is another method of digestion.

Feeding Mechanisms in Animals

Suspension Feeding

• Organisms use body parts to move water toward feeding structures to sift the suspended food.
• Filter feeding captures or traps suspended food particles from the surrounding water.

Substrate Feeding

• Animals live in or on their food source.
• Maggots burrow into animal carcasses.

Fluid Feeding

• Fluid feeders consume nutrient-rich fluid from a living host.
• Aphids tap into phloem sap of plants.
• Some fluid feeders benefit their hosts.

Bulk Feeding

• Most animals eat relatively large pieces of food.
• Adaptations such as tentacles, pincers, venomous fangs, jaws, and teeth are included in this mechanism.

Human Digestive System

• Is made up of organs with specific and coordinated functions

Digestion

• Food breaks down into small absorbable molecules that nourish the body's cells.
• The process has two phases:
• Mechanical
• Chemical

Mechanical Phase

• Food is broken down by chewing, is lubricated, and is softened through digestive juices like saliva and gastric juice.

Chemical Phase

• Enzymes in the digestive juices act on food, breaking it into simpler compounds that cells can use.

Organs of Digestion

• Alimentary
• Accessory

Alimentary

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Rectum
• Anus

Accessory

• Salivary Glands
• Liver
• Gall Bladder
• Pancreas

Alimentary Canal

Mouth

The Mouth

• Digestion begins in the mouth.
• The mouth contains teeth, tongue, palate, and salivary glands.
• Teeth break down food into smaller pieces.
• The Tongue mixes food with silva aiding in swallowing.
• Palate forms the roof of the mouth.
• Salivary glands secrete saliva that lubricates the food
• Mouth is located between the oral cavity and the lips.

Pharynx (Throat)

• It is located at the back of the mouth.
• It serves a common passageway for digestion and respiration

Epiglottis

• It is a muscular flap that keeps food from entering the trachea.
• Food is lubricated and chewed until it becomes a ball-shaped mass known as a bolus.

Esophagus

• A muscular tube from which food passes from the pharynx to the stomach.
• During swallowing, the bolus travels via the esophagus into the stomach using wave-like contractions termed peristalsis.

Stomach

• The expanded organ between the esophagus and small intestine.
• The stomach both stores swallowed food and mixes food with digestive juices.
• Stomach conveys its contents gradually into the small intestine.
• Folds called rugae reside on the interior.
• Stomach contents mix with gastric juices and become chyme.

Small Intestine

• Complete digestion and absorption of nutrients occur here.
• It is composed of the
• Duodenum
• Jejunum
• Ileum

Large Intestine

• Also known as the Colon
• Stores fecal materials
• Absorbs vitamins produced by symbiotic bacteria.
• Reabsorbs water from undigested residue.

Rectum

• It acts as a short-term warehouse for undigested residue or feces.

Anus

• Functions as the passageway for the exit of fecal matter.

Accessory Organs

Salivary glands

• The parotid, submandibular and sublingual glands create siliva.

Liver

Gallbladder and Pancreas

Nutritional Requirements of Animals

Mammals

• They share common nutritional needs for health and normal physiological processes.
• The consumption of water, carbohydrates, proteins, lipids, minerals, and vitamins are needed for studies in the field.

Mineral and Vitamin Intake

• Minerals are inorganic for maintaining homeostasis, trace amounts of minerals are also useful
• Vitamins are complex organic compounds not produced by the body.

Nutrient Over or Underexposure

• The body can suffer from vitamin and mineral deficiencies and excesses.

Common Conditions

• Kwashiorkor is a deficiency disease.
• Marasmus is a form of severe malnutrition.

Nutritional Disorders

• Scurvy involves degeneration of skin and dental health, as well as delayed wound healing.
• Rickets causes bone deformation in children and bone softening in adults.
• Pica is the persistent consumption of nonnutritive substances.
• Heartburn involves a relaxed esophageal sphincter.
• Peptic ulcers are sores that develop in the lining of the stomach.
• Diabetes mellitus is a disease where the pancreas doesn't produce enough insulin.
• Bulimia Nervosa is an emotional disorder involving self induced vomiting.
• Anorexia Nervosa is an emotional disorder involving an obsessive desire to lose weight by refusing to eat.