Anatomy and physiology are the opposite sides of the same biological coin. Anatomy is the study of the body’s internal and external structures while physiology studies the function of those structures, both singularly and in conjunction with one another.
Anatomy, which is sometimes called morphology, provides a map of how a body is put together, human or otherwise. Physiology is akin to an instruction manual. Form and function must both be considered to fully understand the human body.
Today, digital scanners, magnetic resonance imaging (MRI), and other high-tech tools allow researchers to discover even more about human anatomy and physiology noninvasively. In this lesson, the organization of anatomy and its physiology will be outlined and defined.
Physiology is the study of living things, but what exactly does it mean to be alive? It is difficult to isolate a single characteristic that separates all living entities from non-living ones. For example, some might say that the ability to reproduce is a necessary trait to indicate life. But mules, which are definitely living offspring of a horse and donkey, cannot reproduce. So physiologists consider a number of traits that all living things have in common and thus identify life based on the following characteristics:
Everything that is alive, from cells to elephants, relies on homeostasis, which is the way the physiological systems work together in living organisms to maintain a stable internal environment, despite changing external or environmental conditions. In humans, that means regulating things like temperature, pH, hydration, and blood oxygen levels.
All living things also require some sort of metabolism, which is commonly understood to mean breaking food down and turning it into energy. But in physiological terms, it refers to the entire range of an organism’s biochemical processes. These metabolic pathways involve enzymes that transform one substance into another substance, by either breaking one down (catabolism) or creating a new one (anabolism).
Anatomists organize the human body into different levels, each level increasing in complexity.
Spatial Organization of the Human Body
To accurately reference the structures that they study, anatomists use positional and directional terms. To have a common standard for describing those positions of body parts, it is assumed that the person is in what is called an anatomical position: the body standing upright, feet together, palms facing forward. From this starting point, all the directional terms are relative to the anatomical position.
There are three main body planes: the sagittal, which divides the body into left and right halves; the frontal which divides the body into front and back halves (ventral and dorsal, or anterior and posterior); and the transverse which divides the body into upper (toward the head) and lower (toward the feet) halves (superior and inferior).
Additionally, the outer body is divided into two regions: the axial, which includes the head, neck, and trunk, and the appendicular which consists of the limbs.
The same terms are used when describing the skeleton. The skull, ribs, and spinal vertebrae belong to the axial skeleton. These bones protect the major organs such as the brain, heart, and lungs. Also included in the axial skeleton are the three inner ear bones, malleus, incus, and stapes, known collectively as the ossicles, and the hyoid in the throat. There are 80 bones in the axial skeleton.
The appendicular skeleton consists of the 126 bones of our extremities, legs, arms, hands, and feet, which facilitate movement.
The most general definition of a body cavity is any fluid filled space, including the digestive tract. Cavities can also have subcavities, much like the way smaller measuring spoons of a set fit into the tablespoon. The organs contained within a body cavity are called viscera.
The axial region of the body has two primary cavities: the dorsal and ventral. The dorsal cavity contains the cranial cavity (brain) and the vertebral column (spinal cord), both of which are on the dorsal or posterior side of the body.
The ventral cavity consists of the thoracic and abdominopelvic cavities. These two areas are separated by the diaphragm.
The thoracic cavity is your chest region and holds the lungs, heart, thymus gland, lymph nodes, and nerves. Within the thoracic cavity are pleural cavities surrounding each lung. Within the pleural cavity is the pericardial cavity that surrounds the heart.
The mediastinum is the region located between the lungs that separates the thoracic cavity into right and left compartments. It holds the heart, thymus gland, and portions of the esophagus and trachea. Anatomists divide the mediastinum into the anterior, middle, posterior, and superior regions.
The abdominopelvic cavity holds the abdominal and pelvic cavities. The abdominal cavity’s viscera are the stomach, liver, gallbladder, pancreas, spleen, kidneys, small and large intestines, and female ovaries.
The pelvic cavity contains the colon, rectum, bladder, and female uterus.
Other body cavities include the oral, nasal, orbital, and middle ear
The peritoneum, the pleura, and the pericardium cavities are lined with a serosa, or serous membrane, which is comprised of a thin layer of cells that secrete serous fluid, a watery liquid that is rich in proteins and has a light yellow color. Serous fluids also act as a lubricant to minimize friction from muscle movement.
Organ systems are sets of two or more interrelated organs working together to perform a specific function. Below is a chart naming the system, its components, and its main function. All mammals share these same systems.
|Circulatory||Heart, blood, blood vessels, capillaries, bone marrow||Carries oxygen and nutrients to cells; removes wastes|
|Lymphatic (sub system)||Lymph nodes, thymus, spleen||Fights infection|
|Digestive||Mouth, salivary glands, pharynx, esophagus, stomach, small and large intestine, liver, pancreas, gall bladder||Breaks down food so nutrients can be absorbed; provides energy; gets rid of unusable material through excretion|
|Endocrine||Hypothalamus, pituitary, adrenal, pancreas, ovaries, pineal, thyroid, testes||Regulates body chemistry; maintains homeostasis|
|Integumentary||Skin, hair, nails, sebaceous glands||Helps regulate body temperature, provides protection, synthesizes Vitamin D|
|Muscular||Skeletal muscles, smooth muscles, cardiac muscles||Movement|
|Nervous||Brain, spinal cord, nerves, eyes, nose, ears, tongue||The body’s control system; regulates involuntary actions; carries nerve impulses|
|Reproductive||Male: testes, vas deferens, prostate, urethra, penis, scrotum
Female: ovaries, fallopian tubes, uterus, cervix, vagina
|Reproduction; secondary sex characteristics|
|Respiratory||Nose, oral and nasal cavities, pharynx, larynx, trachea, bronchi, lungs||Keeps the blood oxygenated; releases CO2
|Skeletal||Bones, tendons, ligaments, cartilage||Protects internal organs; supports body; works with muscles for motion; forms blood cells;|
|Urinary||Kidneys, ureters, urinary bladder, urethra||Eliminates metabolic wastes; helps regulate blood chemistry|
The body is a complex organism of cells, tissues, organs, and organ systems. While anatomy describes the structure of how it is physically put together, physiology explains how all the components of the human organism work, individually and together, to maintain life.