A biological system is a group of organs working together to perform a common function. For example, the muscular system is involved with movement, the skeletal system provides protection and support, and the circulatory system delivers nutrients and waste to and from the cells of the body. The Bible says:
"For you created my inmost being; you knit me together in my mother's womb." - Psalm 139:13
Each system of the body is indeed knit together. They are integrated into and reliant upon other systems, and none can function independently. The interdependence of biological systems offers strong evidence for intelligent design due to their irreducible complexity. They function synergistically in such a way that the sum of their actions is greater than the addition of the separate, individual actions.
- 1 Circulatory system
- 2 Digestive system
- 3 Endocrine system
- 4 Urinary system
- 5 Integumentary system
- 6 Immune system
- 7 Lymphatic system
- 8 Muscular system
- 9 Nervous system
- 10 Reproductive system
- 11 Respiratory system
- 12 Skeletal system
- 13 Sensory system
- 14 Table of systems
- 15 References
- Main Article: Circulatory system
The Circulatory system helps maintain homeostasis. It delivers gases, helps with the regulation of temperature, and the transport of nutrition and waste. It consists of heart, blood, and blood vessels. There are two different types: open circulatory system and closed circulatory system. Most of vertebrates have a closed circulatory system whereas most of the invertebrate have an open circulatory system.
- Main Article: Digestive system
Digestion is the process by which food and drink are broken down. While some forms of digestion is rather simplistic, vertebrates accomplish the process through a complicated series of orchestrated events involving numerous independent organs. Both systems have a similar order of events in that they they intake food through the mouth or oral cavity and both excrete waste through the anus. Digestive hormones are used to help accomplish digestion.
- Main Article: Endocrine system
The endocrine system is network of glands that secretes hormones (chemical signals) into the circulatory system. It is involved in keeping homeostasis (regulating the bodies internal environment) as well as carrying out many applications controlled by the sympathetic sympathetic and parasympathetic nervous system.
- Main Article: Urinary system
The urinary system is a bodily system responsible for producing, storing, and secreting urine (waste). It includes the kidneys, urinary bladder, urethra, and ureters. It also serves several important roles other than filtering out wastes; including maintain the water levels in the body, and control blood pressure and pH levels. After taking nutrients and vitamins from digested food and converting it to energy for the body to use, certain waste materials are left behind that need to be excreted from the body. Waste materials, both solid and liquid, are left in the bowel and in the blood. This is where the urinary system comes into play. Urea, which is the primary waste removed by the kidney, is the result of the breakdown of foods and vegetables that have protein. The urea is carried by the bloodstream to the kidneys where the filtration process begins.
- Main Article: Integumentary system
The integumentary system is a biological system composed primarily of the skin, but also accessories that grow out of the skin (i.e. hair, scales, and nails). The skin is a vital organ that covers the entire outside of the body, forming a protective barrier against pathogens and injuries from the environment. The skin is the body's largest organ; covering the entire outside of the body, it is about 2 mm thick and weighs approximately six pounds. It shields the body against heat, light, injury, and infection. The skin also helps regulate body temperature, gathers sensory information from the environment, stores water, fat, and vitamin D, and plays a role in the immune system protecting us from disease.
- Main Article: Immune system
The immune system is a bodywide network of cells, tissues, and organs that was designed to defend the body against "foreign" invasions. The proper targets of the immune system are infectious organisms--bacteria such as streptococci; fungi; parasites, including the worm-like microbes that cause malaria; and viruses such as the SARS virus.
- Main Article: Lymphatic system
The lymphatic system produces and transports lymph fluid from tissues to the circulatory system and is a major part of the immune system. The major components of the lymphatic system are lymphatic vessels, lymph, lymph nodes, and some other lymphatic organs. Along lymph vessels are small bean-shaped glandular nodules called lymph nodes.
- Main Article: Muscular system
The muscular system produces body movement and it is also primarily responsible for the movement of blood throughout the body. In vertebrates the muscular system is controlled primarily by the nervous system. There are some muscles that work autonomously from the nervous system which allow the body to run more smoothly. The muscles of the body allow for every movement in your body, and are also used in things not normally noticed. The movement of blood through your veins, the moving of the eyes is all controlled by your muscular system. 
- Main Article: Nervous system
The nervous system regulates the body's responses to internal and external stimuli by carrying information to and from all parts of the body through a vast network of nerve cells. It has two basic parts: the central nervous system (CNS) and the peripheral nervous system. The CNS includes the brain and spinal cord, and the peripheral nervous system includes the nerves outside the CNS (i.e. motor and sensory system functions).
- Main Article: Reproductive system
The Reproductive system is the biological system through which the process of producing children is accomplished. After the egg is fertilized it is the organs of the female body to take over complete responsibility to grow the offspring. Both the male and female bodies have very intricate systems to make the fertilization possible. This also depends on the hormones and the nervous system. Of course now days there are complete new ways to reproduce which includes having a baby without having a mate. Females can get sperm injections as well. 
- Main Article: Respiratory system
The respiratory system is a biological system that is responsible for gas exchange. It involves an interconnected group of organs and tissues that help you breathe. The main parts of this system are the airways, the lungs and linked blood vessels, and the muscles that enable breathing. God has created the respiratory system with an extremely efficient design. It includes the structures that are vital to completing its role in delivering life giving oxygen and removing poisonous carbon dioxide, all working in unison to complete their tasks.
- Main Article: Skeletal system
The skeletal system provides support and protection for animals. There are two main types of skeletal systems. The endoskeleton is an internal support system of the type possessed by humans and other vertebrates, which is made of bone. The exoskeleton is an external system that was designed for many invertebrates such as the crustaceans and insects. The composition of exoskeletons vary widely, but known constituents include calcium salts, protein, carbohydrates (chitin) and silicate.
- Main Article: Sensory system
Sensory systems are designed to detect signals from the environment, such as sound waves, odors, and tastes. Sensory organs like eyes, ears, nose, and the tongue have specialized cells equipped for sensing specific types of stimulus. For example, you can hear the phone ring because sound waves vibrate hairlike projections (called stereocilia) that extend from cells in your inner ear. The message is then communicated through the nervous system. Similarly, to see and smell the world around you and taste its variety of flavors, your body must convey molecular signals from the environment into your sensory cells.
- Main Article: Olfactory system
The olfactory system is a biological sensory system designed to detect odors. Like other sensory organs, the nose has specialized cells equipped for detecting signals from the environment. The message is then communicated through the nervous system..
- Main Article: Auditory system
The auditory system is the sensory system that allows for hearing. There are three portions of the ear: outer ear, middle ear, and inner ear. The outer ear is the portion you can see and the middle ear is between the inner and outer ear. The auditory system helps us recognize dangers that we can't see and communicate with each other more easily.
- Main Article: Visual system
The Visual system is one of the most fascinating and complex biological systems possessed by living organisms. It allows God's creations the ability to perceive the world around them by sight through an intricate process called visual perception. The eye is the most obvious, but not the only component of the visual system. The eye is connected to the brain, and therefore an extension of the brain.
Table of systems
- Body by Design by Alan Gillen. Masterbooks. 2001. p 12
- Circulatory system by Wikipedia
- Purves, William. Life the Science of Biology. 2005. Couriers Company Inc. p 941.
- Anatomy of the Urinary System The Ohio State Medical Center, 2007.
- Anatomy of the Skin by the U.S. Cancer Institute
- Understanding Cancer Series: The Immune System by the the National Cancer Institute
- Lymphatic System by the National Cancer Institute.
- Muscle by Wikipedia
- Reproductive System Information A.D.A.M., adam, 2001.
- Respiratory System by the National Heart Lung and Blood Institute.
- Inside the Cell. Chapter 3 On the Job: Cellular Specialties By Alison Davis. by the National Institute of General Medical Sciences.