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

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)

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).

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

The Human Skeleton

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.

The Human Muscles

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

The Digestive System

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.

Circulatory System

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)

Respiratory System

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)

Excretory System

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)

The Nervous System

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