1. Science 8th Grade Mrs. Roberts
Human Body Systems
Science 8th Grade
Mrs. Roberts

2. Body Organization Cell  Tissue  Organ  System
Cell—basic building block of living things; smallest unit of organization in a living thing
Types of Tissue
Nervous—carries messages back and forth between brain and the rest of the body (Ex. optic nerve)
Muscle—helps move body parts such as arms and legs (Ex. Bicep)
Epithelial—covers and protects body surfaces (inside and outside) (Ex. Skin or the lining of the stomach)
Connective—supports the body and hold it together (ex. Bone)

3. Homeostasis
Homeostasis—the process by which an organism’s internal environment is kept stable in spite of changes in the external environment.
To maintain homeostasis, the Nervous System delivers message between the brain and various body systems (ex. hunger, thirst, sweating).

4. Skeletal System Shape & Support – skull,backbone (spine)
Functions
Shape & Support – skull,backbone (spine)
Movement – fingers, legs, arms
Protects organs – skull, ribs
Produces red blood cells
Storage – minerals & other
Major Organ(s): Bones (newborns 275, adults 206)
Compact bone
Spongy bone
Joints
Immovable – skull, ribs
Moveable – arms, legs
Ligaments – connect bones
Cartilage

5. The Human Skeleton

6. Muscular System Major Organ(s): Muscles Three Types of Muscles
Skeletal-attached to bones; allows movement; voluntary;
Smooth-inside organs (stomach, intestines); involuntary-can’t control
Cardiac-only in heart; involuntary; never get tired
Functions
Enables movement of the body and internal organs
Skeletal muscles work in pairs to move bones; one muscle contracts as the other muscle relaxes.
Example: triceps & biceps (in the arms)
Tendons attach muscles to bones
Voluntary Muscles – Under conscious control – You make them move
Involuntary Muscles – Not under conscious control – work automatically.

7. The Human Muscles

8. Digestive System Major Organs: stomach and intestines
Three Main Functions
Digestion – breaking down food into nutrient molecules
Absorption – Nutrients are absorbed into blood
Elimination – getting rid of undigested food
Digestive Tract/Path of food: mouth→ esophagus→ stomach→ small intestine→ large intestine→ rectum
Villi – Line the small intestine; increases surface area so more nutrients can be absorbed from food.
Intestines are named based on their diameter (how big around) not their length.
Other/Helper Organs (that produce or secrete digestive enzymes)
Liver –Gallbladder –Pancreas

9. The Digestive System

10. Circulatory (Cardiovascular) System
Functions
Delivers needed substances to cells through blood
Removes waste products from cells, carries it to lungs, kidneys, intestines to be removed from the body
Fights disease – white blood cells & T cells
Major Organ: Heart
Blood – carries needed materials (oxygen and glucose) to body cells and carries wastes away from body cells.
Arteries – (aorta) – carry blood away from heart
Veins – (vena cava & jugular) – carry blood to heart
Capillaries – connect arteries & veins – where needed substances are dropped off to cells and waste products are picked up.

11. Circulatory System

12. Respiratory System Major Organ: Lungs Functions
Takes in oxygen through the lungs
Removes carbon dioxide and water from the body through the lungs
Diaphragm-large, dome-shaped muscle involved in breathing
Diaphragm moves up – exhale
Diaphragm moves downward – inhale
Alveoli – Grapelike structures in the lungs where oxygen is taken out of the air and put in the blood and carbon dioxide is taken out of the blood and put into the air.
Breathing Passageway aka Path of Air
Nose →pharynx (throat) →trachea (windpipe lined with cilia and mucus) →bronchi →lungs into alveoli (where gas exchange takes place)

13. Respiratory System

14. Excretory System
Function—Collects wastes (water, urea, other) produced by cells and removes the wastes from the body
Major Organ(s): Kidneys (2) – remove urea & wastes from blood (urine-watery fluid which contains urea)
Excretion & Homeostasis—keeps internal environment stable and free of harmful chemicals
Other Organs involved in getting rid of wastes
Lungs – removes carbon dioxide & some water
Skin – removes water & urea
Liver – filters blood & breaks down chemicals and blood cells into usable substances (recycling facility)

15. Excretory System

16. Nervous System Major Organ(s): Brain & Spinal Cord
Central Nervous System—the control center of the body
Brain-cerebrum, cerebellum, brain stem
Spinal Cord-link from brain to other nerves
Peripheral Nervous System—network of nerves
Voluntary-move muscles
Involuntary -reflexes
Functions
Receives information from inside and outside the body—carries messages back and forth between the brain and other parts of the body
Directs body responses/Responds to information
Helps maintain homeostasis—makes you feel hungry, thirsty, or sweat when needed to maintain stable internal conditions
Reflex – an automatic response that occurs rapidly and without conscious control (ex. blinking)

17. The Nervous System

18. Immune System
Function: reacts to pathogens with a defense to fight disease
Lympohocytes (white blood cells)
T cells – recognize antigens
Destroy viruses
Activate B cells
B cells – produce antibodies
Three Lines of Defense against Pathogens
Barrier – skin, nose, throat, mouth stomach
Inflammation – phagocytes (white blood cells), inflammation, fever
Immune Response
Lymphocytes – T cells and B cells