Anatomy is the study of the structures of the body. Physiology is the study of body functions.
Anatomy & Physiology Basics
As human beings, we are one of the most complex organisms on the planet. We are made up of trillions of microscopic components, each with its own identity, working together in highly organized and specialized ways for the benefit of entire being. Even at this microscopic level, the make up of the body has definite structure and functioning.
Cells
Cells are the simplest form of living matter that maintain life and reproduce. The human body, made up of about 10 trillion cells, begins as a newly fertilized single cell that begins to divide, differentiate, and specialize. Eventually, a baby develops and is born.
Tissues and Organs
Tissues are a collection of specialized cells that carry out a specific function. Tissues can be as solid as muscle or bone tissue or as fluid as blood. Multiple tissues come together to form more complex structures called organs. An organ is a discrete body part that provides very important body functions. Some organs are considered vital, like the heart, brain, lungs, kidneys, liver, etc.
Body Systems
Two or more organs working together in the execution of a specific function form a body system, also called a biological system or organ system. The functions of body systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus. For this reason, the two systems are combined and studied as the neuroendocrine system. The same is true for the musculoskeletal system because of the relationship between the muscular and skeletal systems.
List of Body Systems
As human beings, we have a variety of body systems.
| Body System | Organs and Structure | Functions |
| Cardiovascular system | Heart; blood vessels (arteries, veins, and capillaries); blood; spleen; and bone marrow | The heart pumps blood throughout the body via blood vessels. The blood transfers oxygen, nutrients, immune cells, hormones, and waste products from one body part to another. The bone marrow in the heads of long bones create red bone cells, and the spleen filters out old blood cells. |
| Digestive system | Mouth; tongue; teeth; esophagus; stomach; gut (gastrointestinal tract, small and large intestines, and rectum); liver; pancreas; gallbladder; and salivary glands | The digestive system converts food into nutritional, nontoxic molecules for distribution by the cardiovascular system to all tissues of the body and then excretes any unused residue. |
| Endocrine system | Adrenal glands, ovaries (female), pancreas, pituitary gland, testes (male), and thyroid gland | The endocrine system secretes hormones that regulate body processes. |
| Integumentary system | Skin, hair, nails, sweat glands, and sebaceous glands | The skin provides containment, structure, and protection for other organs, and it also serves as a major sensory interface with the outside world. |
| Lympathic system | Lymph nodes, lymphatic vessels, spleen, and thymus | The lymphatic system returns excess interstitial fluid to the blood, absorbs fats and fat-soluble vitamins, and defends the body against invading microorganisms by carrying white blood cells into the bloodstream and by filtering the lymph to remove microorganisms and other foreign particles. |
| Muscular system | Skeletal muscles and tendons | Muscles, attached to bones or internal organs and blood vessels, are responsible for movement. Nearly all movement in the body is the result of muscle contraction. Exceptions to this are the action of cilia, the flagellumon sperm cells, and amoeboid movement of some white blood cells.
The integrated action of joints, bones, and skeletal muscles produces obvious movements, such as walking and running. Skeletal muscles also produce more subtle movements that result in various facial expressions, eye movements, and respiration. In addition to movement, muscle contraction also fulfills some other important functions in the body, such as posture, joint stability, and heat production. |
| Nervous system | Central nervous system (brain and spinal cord) and peripheral nervous system (nerves and ganglia outside the CNS) | The brain is the organ of thought, emotion, memory, and sensory processing. The brain and nervous system controls various body systems and functions. The eyes, ears, nose, and tongue use special senses to gather information about the body’s environment. |
| Reproductive system | Gonads and internal and external sex organs (epididymis and testes for males; mammary glands, ovaries, and the uterus for females) | The reproductive system produces gametes in each sex (egg and sperm cells), mechanisms for combining the gametes, and a nurturing/birthing process. |
| Respiratory system | Nose, nasopharynx, trachea, and lungs | The respiratory system brings oxygen from the air into the body and excretes carbon dioxide and water back into the air. |
| Skeletal system | Bones, cartilage, joints, and ligaments | Bones provide a rigid framework for the body (the skeleton) that support and protect the soft organs of the body. Bones, joints, and connective tissue work with muscles and tendons to enable body movement |
| Urinary system | Bladder, kidneys, ureters, and urethra | The urinary system removes water from the blood to produce urine, which carries a variety of waste products, ions, and water out of the body. |
The operation of these organ systems is not independent of other body systems. When one system fails, others are affected and may also fail.
Detailed Structures of the Human Body
