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Ch. 38 Digestive & Excretory Systems

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1 Ch. 38 Digestive & Excretory Systems
Unit 10 The Human Body Ch. 38 Digestive & Excretory Systems

2 Food & Energy The energy available in food can be measured by burning the food When food is burned, the energy content of the food is converted to heat, which is measured in calories

3 Food & Energy The average energy needed for a teenager is 2200 Calories per day

4 Nutrients The nutrients that the body needs are water, carbohydrates, fats, proteins, vitamins, & minerals Every cell in the body needs water because many body processes, including chemical reactions, take place in water

5 Nutrients Carbohydrates – main source of energy for the body
Sugars & starches are main source of carbs Starches are broken down by digestive system into simple sugars & carried to cells through blood

6 Nutrients Sugars not immediately used for energy are converted into complex carbs & stored in the liver & in skeletal muscles

7 Nutrients Fats – lipids – important to the body to produce cell membranes, myelin sheaths, & certain hormones

8 Nutrients Proteins – supply raw materials for growth & repair of structures like skin & muscle Also have regulatory & transport functions

9 Nutrients Vitamins – organic molecules that help regulate body processes, often working with enzymes

10 Vitamins

11 Nutrients Minerals – inorganic nutrients the body needs
Includes: calcium, iron, & magnesium

12 Important Minerals

13 Nutrition & a Balanced Diet
The Food Guide Pyramid classifies foods into 6 groups & indicates how many servings from each group should be eaten every day

14 The Process of Digestion
The digestive system includes: the mouth, pharynx, esophagus, stomach, small intestine, & large intestine Several major accessory structures, including the salivary glands, the pancreas, & the liver, add secretions to the digestive system

15 The Digestive System

16 The Mouth The function of the digestive system is to help convert foods into simpler molecules that can be absorbed & used by the cells of the body Teeth cut & grind the food, while the salivary glands secrete saliva, which helps to moisten the food & make it easier to chew

17 The Mouth Amylase – enzyme found in saliva, that breaks the chemical bonds in starches & releases sugars

18 The Esophagus Esophagus – food tube, connects to the stomach
Food travels through esophagus by process of peristalsis – contractions of the smooth muscle tissue in the esophagus

19 The Stomach Stomach – large muscular sac, continues the mechanical & chemical digestion of food

20 The Small Intestine Small intestine – where almost all of the digestive enzymes enter the intestine Most chemical digestion & absorption of food occurs in the small intestine

21 Accessory Structures of Digestion
Pancreas – gland that serves 3 important functions: 1. Produce hormones that regulate blood sugar levels 2. Produces enzymes that break down carbs, proteins, lipids, & nucleic acids 3. Produces sodium bicarbonate, a base that neutralizes stomach acid so enzymes can be effective

22 Accessory Structures of Digestion
Liver – large organ just above & to the right of the stomach Produce bile, a fluid loaded with lipids & salts It acts like detergent, dissolving & dispersing the droplets of fat found in fatty foods Bile is stored in the gallbladder

23 Accessory Structures

24 The Large Intestine Large intestine – primary function is to remove water from undigested material that is left

25 Digestive System Disorders
Peptic ulcer – when powerful acids released into the stomach damage the organ’s own lining, producing a hole in the wall Diarrhea occurs when not enough water is absorbed Constipation occurs when too much water is absorbed

26 The Excretory System The kidneys play an important role in maintaining homeostasis They remove waste products from the blood; maintain blood pH; & regulate the water content of the blood &, therefore, blood volume

27 The Kidneys Kidneys – located on either side of the spinal column near the lower back Ureter – tube that leaves each kidney, carrying urine to the urinary bladder Urinary bladder – saclike organ where urine is stored before being excreted

28 Kidney Structure Nephron – the functional units of the kidney
As blood enters a nephron through the arteriole, impurities are filtered out & emptied into the collecting duct The purified blood exits the nephron through the venule

29 Filtration Filtration – passing a liquid or gas through a filter
Glomerulus – where the filtration of blood takes place

30 Reabsorption Reabsorption – process where liquid is taken back into a vessel Material that remains, called urine, is emptied into a collecting duct Urine contains urea, excess salts, & water Urine is stored in the urinary bladder until released from the body through the urethra

31 Structure Of The Kidneys

32 Kidney Stones Sometimes, calcium, magnesium, or uric acid salts in the urine, crystallize & form kidney stones

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