The Skeletal and Muscular Systems

• The human body is like a complex machine made up of different parts working together
• These parts are called organs, and they perform specific jobs to keep us alive and healthy

The Skeletal System

• The skeletal system is the framework of our body
• It is made up of bones that give us shape, support, and protection
• Bones protect our organs; the skull protects the brain, and the ribs protect the heart and lungs
• Bones store minerals like calcium, strengthening them
• Joints, where two or more bones meet, allow movement
• Cartilage is a smooth, rubbery tissue that cushions the joints
• Marrow, inside some bones, makes blood cells
• There are 206 bones in the adult human body

The Muscular System

• The muscular system enables movement
• Muscles are tissues that contract and relax to produce movement
• Skeletal, smooth and cardiac are the three types of muscles
• Skeletal muscles attached to bones allow voluntary movement
• Tendons connect skeletal muscles to bones
• Involuntary smooth muscles line the walls of internal organs like the stomach and intestines
• Cardiac muscle, found only in the heart, pumps blood

The Digestive System

• The digestive system breaks down food into nutrients for energy, growth, and repair
• Digestion begins in the mouth, where saliva starts breaking down food
• The esophagus carries food from the mouth to the stomach
• The stomach mixes food with digestive juices (acids and enzymes) to further break it down
• The small intestine absorbs nutrients from the digested food into the bloodstream
• The large intestine absorbs water from the remaining waste
• Waste is eliminated from the body through the rectum and anus
• The liver produces bile, which helps digest fats
• The pancreas produces enzymes that help digest carbohydrates, proteins, and fats

The Respiratory System

• The respiratory system takes in oxygen and gets rid of carbon dioxide
• Breathing is respiration
• Air enters the body through the nose and mouth
• The trachea (windpipe) carries air to the lungs
• The trachea divides into two bronchi, one for each lung
• Inside the lungs, the bronchi branch into smaller tubes called bronchioles
• At the end of the bronchioles are tiny air sacs called alveoli
• Oxygen from the air passes into the bloodstream through the alveoli
• Carbon dioxide from the blood passes into the alveoli to be exhaled
• The diaphragm is a muscle that helps with breathing

The Circulatory System

• The circulatory system transports blood, oxygen, nutrients, and hormones throughout the body
• The heart is a muscular organ that pumps blood
• Blood vessels are tubes that carry blood
• Arteries carry blood away from the heart
• Veins carry blood back to the heart
• Capillaries are tiny blood vessels that connect arteries and veins, where oxygen and nutrients are exchanged with the body's tissues
• Blood comprises red blood cells, white blood cells, platelets, and plasma
• Red blood cells carry oxygen
• White blood cells fight infection
• Platelets help with blood clotting
• Plasma is the liquid part of blood

The Nervous System

• The nervous system controls and coordinates all body activities
• The brain is the control center of the body
• The spinal cord connects the brain to the rest of the body
• Nerves are pathways that carry messages between the brain and the body
• Neurons are nerve cells that transmit electrical and chemical signals
• The nervous system has two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS)
• The CNS includes the brain and spinal cord
• The PNS includes all the nerves outside the brain and spinal cord
• The five senses (sight, hearing, taste, smell, and touch) gather information about the environment and send it to the brain

The Excretory System

• The excretory system removes waste products from the body
• The kidneys filter waste from the blood and produce urine
• Urine is stored in the bladder and eliminated through the urethra
• The skin eliminates waste through sweat
• The lungs eliminate carbon dioxide when we exhale
• The liver filters toxins from the blood

The Endocrine System

• The endocrine system produces hormones that regulate various body functions
• Hormones are chemical messengers that travel through the bloodstream
• The pituitary gland is a master gland that controls other endocrine glands
• The thyroid gland regulates metabolism
• The adrenal glands produce hormones that help the body respond to stress
• The pancreas produces insulin, which regulates blood sugar levels
• The ovaries in females and testes in males produce sex hormones

The Immune System

• The immune system protects the body from disease-causing organisms
• White blood cells are a key part of the immune system
• Antibodies are proteins that recognize and attack foreign substances
• The skin and mucous membranes act as barriers preventing pathogens from entering the body
• The lymphatic system helps to filter and remove waste and toxins from the body
• Vaccination builds immunity to specific diseases

Taking Care of Your Body

• Eating a balanced diet provides the body with the nutrients it needs to function properly
• Regular exercise helps to keep the body strong and healthy
• Getting enough sleep is essential for growth and repair
• Good hygiene, such as washing hands regularly, helps to prevent the spread of germs
• Regular check-ups with a doctor can help to detect and prevent health problems

The skeletal system gives shape, support, and protection. The muscular system enables movement; skeletal muscles attach to bones, smooth muscles control involuntary actions, and cardiac muscle forms the heart.