Chapter 41 Concept 41 1 An animal s diet must supply chemical energy organic molecules and essential nutrients Essential nutrient a substance that an organism cannot synthesize from any other material and therefore must absorb in preassembled form Essential amino acid an amino acid that an animal cannot synthesize itself and must be obtained from food in prefabricated form Essential fatty acid an unsaturated fatty acid that an animal needs but cannot make Vitamins an organic molecule required in the diet in very small amounts many vitamins serve as coenzymes or parts of coenzymes Mineral in nutrition a simple nutrient that is inorganic and therefore cannot be synthesized in the body Concept 42 2 The main stages of food processing are ingestion digestion absorption and elimination Ingestion the first stage of food processing in animals the act of eating Digestion the second stage of food processing in animals the breaking down of food into molecules small enough for the body to absorb Absorption the third stage of food processing in animals the uptake of small nutrient molecules by an organism s body Elimination the fourth and final stage of food processing in animals the passing of undigested material out of the body Gastrovascular cavity a central cavity with a single opening in the body of certain animals including cnidarians and flatworms that functions in both the digestion and distribution of nutrients Alimentary canal a complete digestive tract consisting of a tube running between a mouth and an anus Chapter 41 3 Organs specialized for sequential stages of food processing form the mammalian digestive system Peristalsis 1 alternating waves of contraction and relaxation in the smooth muscles lining the alimentary canal that push food along the canal 2 a type of movement on land produced by rhythmic waves of muscle contractions passing from front to back as in many annelids Stomach an organ of the digestive system that stores food and performs preliminary steps of digestion Protease an enzyme that digests proteins by hydrolysis Pepsin an enzyme present in gastric juice that begins the hydrolysis of proteins Pepsinogen the inactive form of pepsin secreted by chief cells located in gastric pits of the stomach Small intestine the longest section of the alimentary canal so named because of its small diameter compared with that of the large intestine the principal site of the enzymatic hydrolysis of food macromolecules and the absorption of nutrients Duodenum the first section of the small intestine where chyme from the stomach mixes with digestive juices from the pancreas liver and gallbladder as well as from gland cells of the intestinal wall Pancreas a gland with exocrine and endocrine tissues the exocrine portion functions in digestion secreting enzymes and an alkaline solution into the small intestine via a duct the ductless endocrine portion functions in homeostasis secreting the hormones insulin and glucagon into the blood Liver a large internal organ in vertebrates that performs diverse functions such as producing bile maintaining blood glucose level and detoxifying poisonous chemicals in the blood Gallbladder an organ that stores bile and releases it as needed into the small intestine Bile a mixture of substances that is produced in the liver and stored in the gallbladder enables formation of fat droplets in water as an aid in the digestion and absorption of fats Microvillus one of many fine finger like projections of the epithelial cells in the lumen of the small intestine that increase its surface area Chylomicron a lipid transport globule composed of fats mixed with cholesterol and coated with proteins Large intestine the portion of the vertebrate alimentary canal between the small intestine and the anus functions mainly in water absorption and the formation of feces Appendix a small finger like extension of the vertebrate cecum contains a mass of white blood cells that contribute to immunity Chapter 41 4 Evolutionary adaptations of vertebrate digestive systems correlate with diet Ruminants an animal such as a cow or a sheep with multiple stomach compartments specialized for an herbivorous diet Chapter 41 5 Feedback circuits regulate digestion energy storage and appetite Leptin a hormone produced by adipose fat cells that act as a satiety factor in regulating appetite Chapter 42 Chapter 42 1 Circulatory systems link exchange surfaces with cells throughout the body Heart a muscular pump that uses metabolic energy to elevate the hydrostatic pressure of the circulatory fluid blood or hemolymph the fluid then flows down a pressure gradient through the body and eventually returns to the heart Open circulatory system a circulatory system in which fluid called hemolymph bathes the tissues and organs directly and there is no distinction between the circulating fluid and the interstitial fluid Hemolymph in invertebrates with an open circulatory system the body fluid that bathes tissues Closed circulatory system a circulatory system in which blood is confined to vessels and is kept separate from the interstitial fluid Blood a connective tissue with a fluid matrix called plasma in which red blood cells white blood cells and cell fragments called platelets are suspended Interstitial fluid the fluid filling the spaces between cells in most animals Artery a vessel that carries blood away from the heart to organs throughout the body Vein in animals a vessel that carries blood toward the heart in plants a vascular bundle in a leaf Capillary a microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid Endothelium the simple squamous layer of cells lining the lumen of blood vessels Chapter 42 3 Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels Systolic pressure blood pressure in the arteries during contraction of the ventricles Diastolic pressure blood pressure in the arteries when the ventricles are relaxed Vasoconstriction a decrease in the diameter of blood vessels caused by contraction of smooth muscles in the vessel walls Vasodialation an increase in the diameter of blood vessels caused by relaxation of smooth muscles in the vessel walls Lymph the colorless fluid derived from interstitial fluid in the lymphatic system of vertebrates Lymphatic system a system of vessels and nodes separate from the circulatory system that returns fluid
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