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

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

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

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

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

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

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

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

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

Vitamins

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

Important Minerals

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

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

The Digestive System

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

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

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

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

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

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

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

Accessory Structures

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

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

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

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

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

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

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

Structure Of The Kidneys

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