Unit 10 The Human BodyUnit 10 The Human Body

Ch. 38 Digestive & Excretory Systems

Food & EnergyFood & 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 & EnergyFood & Energy

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

NutrientsNutrients

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

NutrientsNutrients

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

NutrientsNutrients

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

NutrientsNutrients

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

NutrientsNutrients

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

NutrientsNutrients

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

VitaminsVitamins

NutrientsNutrients

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

Important MineralsImportant Minerals

Nutrition & a Balanced DietNutrition & 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 DigestionThe 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 SystemThe Digestive System

The MouthThe 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 MouthThe Mouth

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

The EsophagusThe 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 StomachThe Stomach

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

The Small IntestineThe 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 Accessory Structures of DigestionDigestion

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 Accessory Structures of DigestionDigestion

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 StructuresAccessory Structures

The Large IntestineThe Large Intestine

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

Digestive System DisordersDigestive 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 SystemThe 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 KidneysThe 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 StructureKidney Structure

Nephron – the functional units of the kidneyAs 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

FiltrationFiltration

Filtration – passing a liquid or gas through a filter

Glomerulus – where the filtration of blood takes place

ReabsorptionReabsorption

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, & waterUrine is stored in the urinary bladder until

released from the body through the urethra

Structure Of The KidneysStructure Of The Kidneys

Kidney StonesKidney Stones

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