Human Body Systems

Science 8th GradeMrs. 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 SystemFunctions1. Shape & Support – skull,backbone (spine)2. Movement – fingers, legs, arms3. Protects organs – skull, ribs4. Produces red blood cells5. Storage – minerals & otherMajor Organ(s): Bones (newborns 275, adults 206)

Compact bone Spongy bone

Joints Immovable – skull, ribs Moveable – arms, legs

Ligaments – connect bonesCartilage

The Human Skeleton

Muscular System Major Organ(s): Muscles Three Types of Muscles

1. Skeletal-attached to bones; allows movement; voluntary; 2. Smooth-inside organs (stomach, intestines); involuntary-can’t control3. Cardiac-only in heart; involuntary; never get tired

Functions1. Enables movement of the body and internal organs2. 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

1. Digestion – breaking down food into nutrient molecules2. Absorption – Nutrients are absorbed into blood3. 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

1. Delivers needed substances to cells through blood2. Removes waste products from cells, carries it to

lungs, kidneys, intestines to be removed from the body

3. 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