1. Meeting the Body’s Basic Needs
Chapter 23

2. Meeting the Body’s Basic Needs
Imagine that your running a race.
The muscles in your legs spring into action when you hear the starting pistol.
Your feet hot the ground as you move ahead of the other runners.
You breathe deeply as air moves into and out of your lungs.
Your heart pounding.
You begin to sweat.
Different systems in your body work together to make all this possible.

3. How the Body Moves
Chapter 23: Section 1

4. The Skeletal System
The 206 bones of the human body make up the skeletal system.
Bones have several functions.
First, bones support the body.
They give the body shape.
Bones form a framework that supports the softer tissue of the body.
Second, bones protect organs.
The rib cage protects the heart and lungs.
Vertebrae protect the spinal cord.
Vertebrae are the 33 bones that make up the backbone.
The pelvis protects reproductive organs.
The skull protects the brain.

5. The Skeletal System A third function of bones is to allow movement.
Muscles attach to bones and move them.
The body has big bones, small bones, flat bones, wide bones, and unusually shaped bones.
The variety of bones helps a person move in different ways.
Fourth, bones are the place where blood cells are formed.
Bones contain spongy material called red marrow.
Red marrow has special cells that make blood cells.
Fifth, bones store minerals, such as calcium, phosphorus, and magnesium.

6. The Skeletal System

7. Cartilage to Bone Most bones start out as cartilage.
Cartilage is a thick, smooth tissue.
It is not as hard as bone.
Before birth, the entire skeleton is cartilage.
It is gradually replaced by bone.
A baby is born with more than 300 bones.
Over time, some of the bones join so that a person ends up with 206 bones.

8. However, some parts of the body continue to have cartilage.
Cartilage to Bone
However, some parts of the body continue to have cartilage.
The end of your nose is cartilage and will never become bone.
Your outer ear contains cartilage.
Inside your body, cartilage surrounds your trachea.

9. How Bones Change Bones are organs that are made of tissue.
They are always changing.
Bones are built up and broken down throughout life.
This is a normal process.
Example: Enzymes break down bone tissue when the body needs calcium.

10. How Bones Change Calcium is released in the bloodstream.
However, if calcium is not placed properly, a person can develop osteoporosis.
The bones of people with this disease become less solid and break more easily than before.
Osteoporosis most often affects older people.
Regular exercise and diet higher in calcium can help prevent osteoporosis.

11. Joints Bones come together at joints.
Cartilage covers bones at the joints.
This cartilage acts like a cushion.

12. Joints

13. The Knee Joint

14. The Muscular System

15. The Muscular System

16. The Muscular System

17. The Muscle System

18. Kinds of Muscle Tissue

19. Kinds of Muscle Tissue

20. Kinds of Muscle Tissue

21. How the Body Digests Food
Chapter 23: Section 2

22. Digestion

23. Digestion

24. Digestion Begins Inside your Mouth

25. The Esophagus

26. The Stomach

27. The Stomach

28. The Small Intestine

29. The Small Intestine

30. The Small Intestine

31. The Small Intestine

32. Villi

33. The Large Intestine

34. The Large Intestine

35. How Materials Move to and from Cells
Chapter 23: Section 3

36. How Materials Move to and from Cells

37. The Heart

38. Heart

39. The Heart

40. How Blood Circulates

41. How Blood Circulates

42. Blood Vessels

43. Blood Vessels

44. Blood Vessels

45. Blood Vessels

46. Blood Pressure

47. Blood and Its Parts

48. Blood and Its Parts

49. Blood and Its Parts

50. Blood and Its Parts

51. Blood and Its Parts

52. Blood and Its Parts

53. Blood Types

54. How we Breathe
Chapter 23: Section 4

55. The Respiratory System

56. How Air Moves to the Lungs

57. Respiration

58. Respiration

59. Respiration

60. Breathing

61. Breathing

62. The Respiratory System

63. How the Body gets Rid of Wastes
Chapter 23: Section 5

64. How the Body gets Rid of Wastes

65. Perspiration

66. Three Layers of Skin

67. The Excretory System

68. The Excretory System

69. The Excretory System