Lecture 22: Nutrition التغذية Nutrition is a process of intake of nutrients المواد الغذائية (like carbohydrates, fats, proteins,vitamins, minerals and water) by the organism.

Nutrients: المواد الغذائية There are seven major classes of nutrients: carbohydrates, fats, fiber, minerals, protein, vitamin, and water. They are classified into two categories: I)- Macronutrients مغذيات كبيرة: needed in relatively large amounts, such as carbohydrates, fats, fibers, proteins, and water. II)- Micronutrients مغذيات صغيرة: needed in smaller quantities, such as minerals الأملاح المعدنية and vitamins .

The macronutrients (but not fibers and water) provide structural material مواد بنائية for example, lipids from which cell membrane is built. Some of the structural materials can be used to generate energy internally لتوليد الطاقة داخليا, and measured in kilocalories كيلو كالوري (often called "Calories"). I- Carbohydrates and proteins provide 4 kcal of energy per gram. II- while fats provide 9 kcal per gram. Vitamins, minerals, and water do not provide energy. Fibers (i.e., non-digestible materials such as cellulose), seems to be required, for both mechanical and biochemical reasons.

Digestive systems: 1- Beaks: birds eat primarily seeds, nuts, and fruit, using their beaks to open even the toughest seed البذور الجافة. 2- Tongue: is a skeletal muscle on the floor of the mouth that manipulates food for chewing (المضغ) and swallowing (البلع). The underside of the tongue is covered with a smooth mucous membrane غشاء مخاطي . 3- Teeth: (singular, tooth) are small whitish structures found in the jaws (الفكوك) of many vertebrates that are used to chew foodمضغ الطعام . - Teeth of carnivores are shaped to kill and tear meatتمزق اللحم . - Teeth of herbivores are made for grinding طحن plant parts.

4- Crop: is a thin-walled expanded portion جزء واسع رفيع الجدارof the alimentary canal used for the storage of food prior to digestion تخزين الطعام قبل الهضم. 5- Gizzard: is a specialized stomach with thickسميك , muscular walls used for grinding up foodطحن الطعام .