Structure and Function of Human Systems Flashcards
Integumentary System
The integument—the skin—is the outermost covering
of the body. It consists of the epidermis (the thinner
outermost layer) and the dermis (the thicker innermost
layer). It also includes the hair and nails. Beneath
the skin is the subcutaneous tissue.
The integumentary system has the following
functions:
■ Protecting the body from injury, dehydration,
and invasion by harmful agents such as bacteria
■ Providing sensitivity to pain, temperature, and
pressure
■ Regulating body temperature
Skeletal System
The skeleton provides the structure of the body. Comprised of 206 bones, along with cartilage and ligament, the skeletal system is rigid yet flexible. Joints are points where bones meet and may or may not move
against each other. The cartilage is the flexible but
strong substance found in joints, nose, and ears. The
ligaments, made of softer, flexible tissue, attach bones
to each other.
The skeletal system has the following functions:
■ Providing mechanical support
■ Protecting body organs
■ Making body movement possible (along with the
muscles)
■ Storing calcium in the bones, which contain marrow
for production of red and white blood cells and platelets
Muscular System
Muscles are made of sheets or bundles of cells.Muscles
can do work only by contracting; expansion is passive.
Therefore, skeletal muscles are usually attached to a
bone in opposing pairs—one to contract while the
other expands. There are three major types of muscles:
■ Voluntary (or striated) muscles can be controlled
by conscious thought.
■ Involuntary (or smooth) muscles cannot be controlled
by the will.
■ Cardiac (or heart) muscles exist only in the heart.
They contract spontaneously without needing nervous stimulation.
Circulatory System
The circulatory system consists of the cardiovascular
and lymphatic systems, including:
■ the heart
■ blood components such as red blood cells and
platelets
■ blood vessels, including arteries, veins, and
capillaries
■ lymphatic vessels and nodes
■ lymph
The circulatory system circulates blood throughout
the body, making the body’s other functions possible
by bringing oxygen and other materials to the cells and carrying away waste products and other secretions.
Immune System
The immune system is the body’s protective mechanism.
It consists of the lymphatic system; the white cells of the blood and bone marrow; antibodies; the thymus gland; and the skin. The basic characteristics of the immune system include the concepts of:
■ Specificity: the capacity to recognize and get rid
of antigens by producing lymphocytes and antibodies.
An antigen (literally meaning “antibodygenerating”)
can include anything “foreign” to the body, such as viruses, bacteria, pollen, and, unfortunately, tissue that has been transplanted.
■ Diversity: the capacity to respond to millions of kinds of invaders.
■ Self/nonself recognition: the ability to distinguish
the body’s own molecules (“self ”) from antigens (“nonself ”).
■ Memory: the capacity to “remember” previously
encountered antigens and react more quickly when exposed again. This process is called acquired immunity.
The immune system’s basic function is to protect
the body from disease and injury.
Respiratory System
The respiratory system is responsible for taking oxygen
into the body and eliminating carbon dioxide. It
includes the lungs, nose, pharynx, larynx, trachea,
bronchi, and diaphragm.
Digestive (or Gastrointestinal) System (GI)
The digestive system includes the gastrointestinal (GI)
tract (also called the alimentary canal). This is basically
a tube with two openings—the mouth and anus—for
intake of food and elimination of waste. The parts of
the GI tract are the mouth, the esophagus, the stomach,
the small intestine, and the large intestine. Also
included in this system are structures such as teeth,
tongue, liver, pancreas, and gallbladder. The digestive system breaks down food for energy, reabsorbs water and nutrients, and eliminates waste.
Urinary or Excretory System
The urinary system consists of:
■ Kidneys: two compact, bean-shaped organs through which blood is cycled for removal of waste
■ Nephrons: excretory tubes in the kidneys
■ Blood vessels that serve the kidneys
■ Urinary structures that carry waste out of the body—the ureters, bladder, and urethra. The kidneys remove waste or toxic byproducts from the blood and maintain homeostasis of blood and body fluids.
Nervous System
The nervous system is made up of the nerves, brain,
spinal cord, and sense organs for sight, sound, smell,
and taste. The brain is the nervous system’s main control
center and consists of three parts:
■ The cerebral hemispheres are responsible for the
higher functions, such as speech and hearing.
■ The cerebellum is responsible for subconscious
activities and some balance functions.
■ The brain stem is responsible for basic functions
such as breathing and circulation
The nervous system controls the flow of information
between the sensory and motor cells and organs.
Endocrine System
The endocrine system controls communication
between systems in the body. It consists of:
■ Hormones are substances that regulate the
growth or function of a specific tissue or organ.
Hormones include insulin, sex hormones,
adrenaline, and serotonin.
Glands that secrete hormones include the pituitary,
adrenal gland, thyroid, ovary, testis, and part
of the pancreas. Together with the nervous system, the endocrine system regulates and balances bodily fluids and chemicals. Hormones affect the body’s growth, the
development and functioning of reproductive organs
and sexual characteristics, the development of higher
nervous functions such as personality, and the ability
of the body to handle stress and resist disease.
Reproductive System
Reproduction in humans involves two sets of organs,
the internal reproductive organs and the external genitalia. In reproduction, the female ovum and the male
spermatozoon fuse to form a zygote, which eventually
develops into a fetus. The reproductive system functions to create new individuals from existing ones and propagate the species.
