Digestion and Metabolism

• Animal nutrition involves obtaining and using food to support biological functions.
• Nutrients such as carbohydrates, proteins, fats, vitamins, and minerals are essential for maintaining health.

Importance of Nutrients

• Nutrients, especially carbohydrates and fats, are broken down to release energy through cellular respiration.
• Energy is essential for maintaining bodily functions like movement and temperature regulation.
• Without enough energy, animals cannot survive.
• Proper nutrition provides building blocks for tissue growth and cell development.
• Proteins, amino acids, and minerals like calcium are essential for muscle and bone growth.
• Poor nutrition can lead to stunted growth.
• Nutrition supports hormone production, gamete formation, and embryo development, which are key to reproductive success.
• A balanced diet ensures animals have the energy and nutrients needed for reproduction.
• Adequate nutrition, including vitamins, minerals, and antioxidants, supports the immune system.
• Vitamin C and zinc are crucial for immune function
• Malnourished animals are more vulnerable to infections.
• Proper nutrition is key for healthy animal populations for survival, growth, and reproduction.
• Well-nourished animals maintain balanced populations, contributing to ecosystem stability.
• Poor nutrition due to habitat destruction affects animal populations and food webs, threatening ecosystem sustainability.

Essential Nutrients (Vitamins) in Humans

• Carbohydrates are the body's primary energy source, producing fuel through glucose metabolism and neurotransmitter synthesis.
• Excess carbohydrates are stored as glycogen in the liver and muscles.
• Dietary fiber, a complex carbohydrate, promotes digestion and gut health.
• Fats provide long-term energy storage, offering more energy per gram than carbohydrates.
• Fats insulate the body and protect organs and aid in the absorption of fat-soluble vitamins (A, D, E, and K).
• Fats support brain health by supplying essential fatty acids like omega-3 and omega-6, crucial for cognitive function.
• Proteins are essential for building muscles, skin, hair, and connective tissues.
• Proteins facilitate metabolic reactions as enzymes, support the immune system by forming antibodies, and regulate bodily functions through hormones.
• Proteins can serve as an energy source when carbohydrates and fats are lacking.

Essential Vitamins

• Vitamin A (Retinol): Fat-soluble; essential for vision, immune function, skin health, and cellular growth; needed for the formation of retinal.
• Vitamin D (Calciferol): Fat-soluble; helps in calcium and phosphorus absorption, promoting bone and teeth health; aids in immune system regulation and cell growth.
• Vitamin E (Tocopherol): Fat-soluble; acts as an antioxidant, protecting cells from oxidative damage; supports immune function and red blood cell formation.
• Vitamin K (Phylloquinone): Fat-soluble; essential for blood clotting and regulates calcium for bone health.
• Vitamin C: Water-soluble; vital for collagen synthesis, supports skin, blood vessels, and bones; enhances immune function and acts as an antioxidant.
• Vitamin B1 (Thiamine): Water-soluble; necessary for energy metabolism and supports nerve and muscle function.
• Vitamin B2 (Riboflavin): Water-soluble; important for energy production and supports skin and eye health.
• Vitamin B3 (Niacin): Water-soluble; plays a key role in energy metabolism and supports skin health and the nervous system.
• Vitamin B5 (Pantothenic acid): Water-soluble; involved in the synthesis of coenzyme A, essential for fatty acid metabolism, energy production, and hormone synthesis.
• Vitamin B6 (Pyridoxine): Water-soluble; essential for amino acid metabolism, neurotransmitter synthesis, and red blood cell production; supports immune function.
• Vitamin B7 (Biotin): Water-soluble; important for the metabolism of fatty acids, amino acids, and glucose; it plays a role in maintaining healthy hair, skin, and nails.
• Vitamin B9 (Folate): Water-soluble; crucial for DNA synthesis and cell division, vital for growth, reproduction, and tissue repair; helps in red blood cell production.
• Vitamin B12 (Cobalamin): Water-soluble; key for red blood cell production, nervous system function, and DNA synthesis; essential for energy metabolism.

Metabolism and the Digestive System

• Metabolism refers to the sum of all chemical reactions in the body to provide energy.
• The digestive system breaks down food into nutrients for energy via anabolism and catabolism.
• Anabolism synthesizes complex molecules from simpler compounds requiring energy.
• Anabolism builds and repairs cellular structures and tissues.
• Catabolism breaks down complex molecules into simpler compounds, releasing energy for physiological processes.
• Catabolism occurs during digestion when carbohydrates, proteins, and fats are broken down.

Phases of Digestion

• Digestion has four phases: ingestion, digestion, absorption, and elimination.
• Ingestion: Taking in food through the mouth; food is broken down mechanically and chemically.
• Digestion: Breaking down food into small particles or molecules for absorption; it is both mechanical and chemical.
• Mechanical digestion involves chewing, smashing, and grinding food in the mouth increasing of surface area.
• Chemical digestion involves enzymes breaking down larger molecules into smaller ones, starting in the mouth with salivary amylase.
• Absorption: Smaller molecules are absorbed into the bloodstream, predominantly in the small intestine.
• Elimination: Undigested food or waste is eliminated through the anus.

The Human Digestive System

• The digestive system is a network of organs that break down food, absorb nutrients, and eliminate waste.

Anatomy of the Digestive System

• The digestive system is a continuous tube from the mouth to the anus.
• Mouth: The mouth is responsible for ingestion and mechanical/chemical digestion.
• The tongue aids in taste perception and mixing food; teeth mechanically break down food.
• Saliva from salivary glands contains enzymes for carbohydrate digestion.
• Esophagus: A tube connecting the mouth to the stomach.
• It secretes mucus to ease movement and uses peristalsis to transport food.
• No digestion occurs here.
• Stomach: A muscular, bag-like structure for food storage and mixing with digestive juices to form chyme.
• The stomach lining secretes gastric acid and enzymes for chemical digestion.
• Small Intestine: It is a long, muscular tube where most digestion and absorption occur via the duodenum, jejunum, and ileum.
• The duodenum receives digestive secretions from the liver and pancreas.
• The liver produces bile, stored in the gallbladder, which aids in fat digestion through emulsification.
• Pancreatic juices contain enzymes (lipase, amylase, proteases) and bicarbonate.
• Enzymes break down fats, carbohydrates, and proteins, while bicarbonate neutralizes acidic chyme.
• The jejunum and ileum absorb essential nutrients like amino acids, fatty acids, and simple sugars into the bloodstream.
• Large Intestine: Composed of the cecum, colon, and rectum and removes water/electrolytes to form feces.
• It houses beneficial bacteria for digestion.
• Accessory Organs: The liver, gallbladder, and pancreas are accessory organs to digestion.
• The Liver produces bile to break down fats into fatty acids.
• The Gallbladder stores and releases bile into the small intestine.
• The Pancreas produces enzymes to digest food, especially proteins.