30.1 Organization of the Human Body

The levels of organization in the body include cells, tissues, organs, and organ systems.

Homeostasis describes the relatively constant internal physical and chemical conditions that organisms maintain despite changes in internal and external environments.

• epithelial tissue (863)

• muscle tissue (863)

• connective tissue (863)

• homeostasis (865)

• nervous tissue (863)

• feedback inhibition (865)

30.2 Food and Nutrition

Molecules in food contain chemical energy that cells use to produce ATP. Food also supplies raw materials your body needs to build and repair tissues.

The nutrients that the body needs include water, carbohydrates, fats, proteins, vitamins, and minerals.

A balanced diet provides nutrients in adequate amounts and enough energy for a person to maintain a healthful weight.

• Calorie (868)

• protein (870)

• carbohydrate (869)

• vitamin (871)

• fat (870)

• mineral (872)

30.3 The Digestive System

The digestive system converts food into small molecules that can be used by the cells of the body. Food is processed by the digestive system in four phases—ingestion, digestion, absorption, and elimination.

During digestion, food travels through the mouth, esophagus, stomach, and small intestine. Mechanical digestion and chemical digestion are the two processes by which food is reduced to molecules that can be absorbed.

Most nutrients from food are absorbed through the walls of the small intestine. The large intestine absorbs water and several vitamins and prepares waste for elimination from the body.

• mechanical digestion (875)

• pepsin (877)

• chemical digestion (875)

• chyme (877)

• amylase (876)

• small intestine (878)

• esophagus (877)

• villus (880)

• peristalsis (877)

• large intestine (881)

• stomach (877)

30.4 The Excretory System

The excretory system, which includes the skin, lungs, liver, and kidneys, excretes metabolic wastes from the body.

As waste-laden blood enters the kidney through the renal artery, the kidney removes urea, excess water and minerals, and other waste products.

The kidneys respond directly to the composition of the blood. They are also influenced by the endocrine system. Disruption of proper kidney function can lead to serious health problems.

• excretion (882)

• filtration (884)

• ureter (883)

• glomerulus (884)

• urinary bladder (883)

• Bowman's capsule (884)

• urethra (883)

• reabsorption (884)

• nephron (884)

• loop of Henle (884)

Visual Thinking Create a flowchart that shows the path of a glucose molecule through a healthy nephron.