Study Guide for Systems of the Human Body

Body Systems Study Guide

I. The Skeletal and Muscular systems work together to help you move.

Skeletal System:

4 main jobs:

• To support your body and give it shape
• To protect your internal organs
• To provide a scaffold for your muscles, allowing you to move
• To store minerals and make blood cells

Joints are parts of the body where two bones meet. Ligaments are bands of tissue that hold the bones of joints together (BLB).

Muscular System:

3 types of muscle:

• Skeletal Muscle contracts to allow bones to move. Tendons connect muscles to bones. These muscles are voluntary (you control them). Nerves control skeletal muscles). These muscles usually work in pairs (for example, one works to extend your leg, another one works to bend your leg back).
• Smooth Muscle is found in the walls of many organs (for example, your stomach’s rumbling is caused by smooth muscle). These muscles are involuntary (not under your conscious control).
• Cardiac Muscle is found only in the heart. It works continuously. It is also involuntary.

II. The Digestive and Excretory systems work together to bring in nutrients and get rid of wastes.

Digestive System: breaks down food into materials that the body can use. Mechanical digestion breaks food down into smaller pieces. Chemical digestion uses chemicals called enzymes to break large food molecules into smaller molecules that the body can use.

Nine major parts:

• Mouth: teeth grind food into smaller pieces and saliva begins to break starches into sugars.
• Esophagus: carries food to the stomach.
• Liver: produces a liquid called bile that helps break down fats. The gall bladder stores the bile until it is needed.
• Pancreas: makes enzymes that break down carbohydrates and protein in the small intestine.
• Stomach: stomach muscles grind food into smaller pieces. Acids made here help break down protein.
• Small intestine: liquid food moves here from the stomach. Most chemical digestion happens here. Once digestion is complete, nutrients are absorbed into the blood stream for delivery to the body cells.
• Large intestine (colon): materials that cannot be digested move to the large intestine. Remaining water is absorbed into the blood stream and wastes are prepared for removal.
• Rectum: wastes exit the body here.

Excretory System: removes wastes produced by cells. Many of these wastes are removed as liquid urine.

• Urine is cellular waste that is filtered from your bloodstream as blood passes through your kidneys.
• Nephrons are the filters in your kidneys that capture the wastes.
• Wastes flow from kidneys through tubes called ureters into the bladder and is released from the body through the urethra.

Your skin is part of the excretory system because it provides a way to release water and salts through perspiration.

III. The Respiratory and Circulatory Systems work together to take in oxygen and deliver it to the body cells.

Respiratory system: brings oxygen into the body and releases carbon dioxide waste produced by cells during cellular respiration.

• Air enters your body through the nose and mouth.
• Next it moves through the trachea (wind pipe) into the bronchial tubes and into the lungs.
• Lungs are made of about 700 million air sacs called alveoli. Each alveolus is surrounded by tiny blood vessels. Oxygen from the air moves across a thin membrane into the blood stream and is carried to all body cells. At the same time, carbon dioxide carried in the blood moves across the thin membrane into the alveoli. This CO₂ moves back through the respiratory system and is exhaled from your body.
• Your diaphragm muscle below your lungs helps the lungs to inflate with air when you breathe.

Circulatory System: transports needed material throughout your body and carries away wastes.

It has three parts:

• Blood: a tissue made of cells and cell parts carried in liquid called plasma.

Blood contains:

• Red blood cells specialized to carry oxygen and CO_2.
• White blood cells that help you fight disease.
• Platelets which help your blood clot when you are injured.
• Heart: fist sized organ that pumps blood throughout your body.
• Vessels: tubes that carry blood around your body.

Arteries carry blood away from the heart. They divide to form smaller vessels.

Capillaries are tiny vessels. Valuable nutrients in blood are exchanged between the capillaries and your cells. Unneeded wastes leave the cells and enter the bloodstream here as well.

Veins take blood carrying wastes back to the heart.

Human circulatory system has two loops:

• Heart à lungs à heart (to release CO₂ and to pick up oxygen)

• Heart à body à heart ( to deliver oxygen, pick up CO₂ )

IV. Nervous System: controls body activities and helps you sense and respond to changes in your environment.

It is made up of:

• Brain

• Spinal cord (nerve bundle extending down your back; protected by your backbone [vertebrae]).

• Nerves send info back and forth between brain and body.

Your five senses provide info to your brain through the nervous system.

V. Immune System: protects body against microscopic invaders called pathogens (bacteria, viruses and fungi).

• White blood cells either engulf pathogens and destroy them or produce antibodies which stick to the pathogen to destroy it.