What are the functions of each major biological system in the human body?

Each system is made up of distinct components and each serves a specific function.  

• Muscular system

1. 1. Components: Cardiac muscles and smooth muscles
   2. Function: Protects internal organs, and supports posture, locomotion, and pumping of blood to all parts of the body

• Skeletal system

1. 1. Components: Bones, joints, cartilage
   2. Function: Supports the body, enables movement

• Integumentary system

1. 1. Components: Skin, nails, and hair
   2. Function: Acts as a barrier protecting the body from physical, chemical, and biological external agents

• Nervous system 

1. 1. Components: Brain, spinal cord, and nerves
   2. Function: Initiates and regulates vital body functions, sensations, and movements, and controls all bodily systems

• Cardiovascular system

1. 1. Components: Heart, blood vessels
   2. Function: Transports oxygen, nutrients, and hormones throughout the body through the blood, and helps eliminate cellular metabolic waste 

• Endocrine system

1. 1. Components: Thyroid gland, pineal gland, adrenal gland, pituitary gland, thymus, ovary, testis, and pancreas
   2. Function: Secrete hormones that regulate most bodily functions and processes such as growth, metabolism, and reproduction

• Respiratory system

1. 1. Components: Nasal cavity, pharynx, larynx, trachea, bronchus, lungs
   2. Function: Supplies the body with oxygen for cellular respiration and eliminates carbon dioxide 

• Digestive system

1. 1. Components: Oral cavity, esophagus, liver, stomach, small intestine, large intestine, rectum, anus
   2. Function: Degrades food mechanically and chemically for more efficient absorption into the body  

• Lymphatic system

1. 1. Components: Bone marrow, thymus, lymphatic vessels, lymph nodes, thoracic nodes, spleen
   2. Function: Protects the body against infections and drains excess fluids and debris from tissues and cells

• Reproductive system

1. 1. Components: Prostate gland, penis, testis, scrotum, and ductus deferens in males and mammary glands, ovary, uterus, vagina, and fallopian tube in females
   2. Function: Contributes towards the reproduction process

• Urinary system

1. 1. Components: Kidney, ureter, urinary bladder, and urethra
   2. Function: Filters the blood and eliminates waste products from the body by producing and excreting urine