Digestion and Excretion Chapter 15

Lesson 1: Nutrition

Food provides your body with energy and nutrients it needs to survive Every activity you do requires energy, even sleeping Digestive system processes food and releases energy that is used for cellular processes and all activities you do Why do you eat?

eNERGY The amount of energy in food is measured calories A Calorie (Cal) is the amount of energy it takes to raise the temperature of 1kg of water by 1°C Each food contains a different amount of energy For example: Grape = 2 Cal Slice of cheese pizza = 220 Cal The amount of energy a person requires depends on the person (weight, gender, activity level) eNERGY

Nutrients Food is made of nutrients Nutrients are substances that provide energy and materials for cell development, growth, and repair Groups of Nutrients: Proteins – Build and repair tissue Carbohydrates – Major source of energy Fats – Stored energy Vitamins – regulation of body functions Minerals – help body regulate many chemical reactions Nutrients

Lesson 2

Types of digestion Mechanical digestion: Chemical digestion: Food is physically broken down into smaller pieces (chewing, mashing and grinding food) Chemical digestion: Chemical reactions break down pieces of food into smaller molecules Chemical digestion cannot occur without the help of enzymes Types of digestion

Enzymes: Proteins that help break down larger molecules into smaller molecules. Enzymes speed up, or catalyze the rate of chemical reactions Without enzymes, some chemical reactions would be too slow or would occur at all enzymes

Many molecules are too big for your body to use, they must be broken down. The digestive system produces enzymes that are specialized to help break down each type of food molecule The enzyme doesn’t break apart just the food particle. The enzyme is ready for use immediately The role of enzymes

Organs of the digestive system In order for your body to use nutrients in the food you eat, nutrients must pass through digestive system Digestive system has 2 parts: Digestive tract Other organs that help the body break down and absorb food Other organs include the tongue, salivary glands, liver, gallbladder, and pancreas Organs of the digestive system

Mouth Digestion begins in your mouth Teeth and tongue mechanically digest food by chewing Salivary glands produce saliva Saliva contains an enzyme that helps break down carbohydrates Mouth

Esophagus After swallowing, food enters your esophagus Esophagus is a muscular tube that connects the mouth to the stomach. Food moves through the esophagus by waves of contractions called peristalsis Partially digested food is pushed down the esophagus into the stomach Esophagus

stomach

Stomach The stomach is a large hollow organ 2 functions of the stomach: Temporarily store food – can expand like a balloon Chemical digestion: Walls of the stomach are folded The cells in these folds produce chemicals that help break down proteins Contains “Gastric Juice” which makes stomach acid and contains pepsin, an enzyme that helps break down proteins into amino acids. As food mixes with gastric juice in the stomach, it forms a thin, watery liquid called Chyme Stomach

Small intestine

Small intestine Most chemical digestion occurs in the small intestine The small intestine is a long tube connected to the stomach This is where chemical digestion and nutrient absorption occur Like the stomach, the walls of the small intestine are folded The folds of the small intestine are covered with fingerlike projections called villi Each Villus contains small blood vessels Nutrients in the small intestine diffuse into the blood through these blood vessels. Small intestine

Parts of food that are not absorbed in the small intestine move by peristalsis into the large intestine, also called the colon Large intestine bigger in diameter than small intestine but much shorter Water absorbed in the large intestine Materials that pass through large intestine are waste products of digestion Waste products become more solid as excess water is absorbed Peristalsis continues to force the remaining semisolid waste material into the last section of the large intestine, called the rectum. Muscles in the rectum and anus control the release of this semisolid waste, called feces Large intestine

Large intestine

Bacteria and digestion Not all bacteria are harmful Some bacteria have an important role in the digestive system Some digest food and produce important vitamins and amino acids Bacteria in the intestines are essential for proper digestion Bacteria and digestion

Digestive system and Homeostasis Nutrients from food are absorbed in the small intestine Digestive system must function properly for absorption to occur These nutrients are necessary for other body systems to maintain homeostasis Example: The blood in the circulatory system absorbs the products of digestion Blood carries the nutrients to all other body systems, providing them with energy Digestive system and Homeostasis

Lesson 3: The Excretory system

Function of the excretory system Collects and eliminates wastes from the body Regulates the level of fluids in the body Function of the excretory system

Collection and elimination Your body collects wastes: The digestive system collects waste products in the intestines The circulatory system collects waste products from the blood If waste is not removed or eliminated from your body it could become toxic and damage your organs. Collection and elimination

Regulation of liquids Water is an essential nutrient for your body Some water is lost when waste is eliminated Excretory system controls how much water leaves the body This ensures that neither too little nor too much water is lost Regulation of liquids

Digestive system collects and removes undigested solids from foods you eat Urinary system processes, transports, collects, and removes liquid waste from the body The respiratory system removes carbon dioxide and water vapor from the body The integumentary system, secretes salt and water through the sweat glands Types of excretion

Organs of Urinary system Kidneys Bean shaped organ that filters, or removes, wastes from blood Contain blood vessels and Nephrons Nephrons are networks of capillaries and small tubes where filtration of blood occurs. When blood is filtered, a fluid called urine is produced Organs of Urinary system

Nephrons Kidney is made up of about 1 million nephrons Nephrons filter the blood twice Your entire blood supply is filtered by the kidneys about 60 times each day Nephrons

Ureters, bladder and urethra Urine cannot stay in the kidney It leaves each kidney through a tube called a ureter Both ureters drain into the bladder Bladder holds urine until it is excreted Urine leaves the bladder after it is full through a tube called the urethra Ureters, bladder and urethra

Excretory system and homeostasis Excretory system filters wastes from the blood If wastes were able to build up they would become toxic Also, removal of wastes from the digestive system maintains homeostasis Excretory system and homeostasis