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Integumentary System

The term "integumentary system" comes from a Latin word which means "covering". The skin is only part of the integumentary system. Module four examines the skin and the related structures of the hair, glands and nails. As an extension of the skin, "the breast" will be discussed. The breast will also be referred to in modules five and fourteen.

The skin consists of a structure that has three distinct layers:
The epidermis:
  • Consists of epithelial cells that also line the body cavities and the organs
  • Has cells called melanocytes in the skin that give it color. The reason for the color is the presence of a pigment called melanin. The more melanin you have the darker your skin will be.
  • Has a protein called keratin that makes the skin tough, waterproof and resistant to infection.
  • Has no blood vessels or nerves in this layer. It relies on the layers below it for nourishment.
  • Is the outermost layer of the skin
Dermis
  • Is the layer of skin directly below the epidermis
  • Is composed of blood and lymph vessels, nerve fibers, and the accessory organs of the skin
  • Has blood vessels in this layer which bring the nutrients to the skin
  • Contains blood vessels that also help control the body temperature by dilating and allowing heat to escape when the body is hot and by constricting and preventing loss of heat when it is cold
  • Contains cells that allow it to be strong (fibroblasts), destroy bacteria (macrophages) and act against foreign bodies (mast cells and plasma cells)
Subcutaneous Tissue

The subcutaneous tissue:

  • Is a layer of connective tissue that is not really part of the skin
  • Connects the dermis layer to the muscles and organs that are below
  • Contains fat that insulates the body parts below

Breast Classification

The breast is part of both the integumentary system and, in females, the reproductive system. Both men and women have breast tissue, which is an extension of the skin itself. Skin stretches to accommodate the developing breast tissue under it. The development of breasts is normal in females. It is abnormal for men to develop breasts and is usually the result of a hormone imbalance.
Breast development begins before birth. At that stage the breasts are unrecognizable and consist of thickened tissue. As development progresses, in utero, groups of cells begin to develop into ducts and milk producing glands. Other tissue develops into the nipple (the protruding point of the breast) and the areola (darkened tissue surrounding the nipple).

Individual lobules group together into larger units called lobes. On average, there are 15-20 lobes in each breast. They are arranged in a pattern similar to the spokes of a wheel, moving out from the nipple/areolar area.
The breasts of younger women are primarily composed of glandular tissue with only a small percentage of fat. As women age, and estrogen decreases, the lobes lose muscle tone and are replaced by fat, resulting in the breast becoming softer with less support.

Anatomy and Physiology of Bone and Muscle

Bone

Each of the 206 bones of the body is a complex, living organ. The shape, height and weight of the body is determined by the length and thickness of the bones. In addition to providing structure, bones:

Bone is a form of connective tissue and is one of the hardest tissues in the human body. The only part of the body that is harder is the enamel of the teeth. Throughout a lifetime, bone goes through a process of building up and tearing down. Bone is also capable of healing and repairing itself. Oste/o, oss/e, osse/o and oss/i are the roots for bone.

Mature bone cells are referred to as osteocytes. Because of osteoclasts (cells that break down and reabsorb bone) the life span of an osteocyte is limited. The cells that create the new bone cells to replace those that are destroyed are referred to as osteoblasts (immature bone). This process of making new bone is referred to as ossification or osteogenesis. This continuous turnover of bone ensures that the bones of the body remain strong.

Bone is made up of four different tissues:

Axial and Appendicular Skeleton

The skeleton is composed of 206 bones. To simplify discussions, it is divided into 2 skeletons:

Bone Fractures

The most common problem that arises with bone is a break or fracture. There are several types of fractures. The most common types are:

Joints

  • Ligament: Band of tissue that connects one bone to another (Ligament/o)
  • Bursa: Fibrous sac that acts as a cushion for easy movement (Burs/o)

    • Muscles

    There are over 600 muscles in the body. There are three types of muscle tissue:

    The study of the activity of muscle is called kinesiology (kih-nee-see-ol-oh-jee). The root for movement is kinesi/o and the suffix is -kinesis. The muscles of the body are arranged in pairs. One muscle of the pair causes movement in one direction and the other produces movement in the opposite direction. When one muscle contracts the other relaxes. When a muscle contracts it tightens up and becomes shorter and thicker. When the muscle relaxes it returns to its original form or shape. It is because of this relaxing and contracting that we are able to move about.

    Range of Motion

    The term range of motion refers to the movements that are possible by a joint. One aspect of diagnosing problems of the muscle is to test the range of motion of joints. A variety of muscle movements can be assessed including:

    • Abduction: Movement away from the midline of the body (ab-)
    • Adduction: Movement toward the midline of the body (ad-)
    • Flexion: Decreasing the angle between two bones, or bending a joint (flex-), e.g. bending the arm at the elbow
    • Extension: Increasing the angle between two bones, or straightening out a limb (ex-), e.g. straightening the arm out at the elbow
    • Rotation: Movement in a circular motion
    • Pronation: Rotating a body part so it is facing down.
    • Supination: Rotating a body part so it is facing up.

    The naming of a muscle is generally based on one of the following:

    • How they act (i.e., flexor carpi radialis muscle)
    • Where they are located (i.e., rectus abdominus)
    • The direction their fibers run (i.e., external abdominal oblique)
    • The number of times they divide (i.e., quadriceps femoris)
    • Their size (i.e., gluteus maximus)
    • Their shape (i.e., deltoid muscle)

    Pathology of Muscular Diseases and Common Diagnostic Procedures

    Health problems that affect the way muscles work in our body include:

      Degeneration of the muscle (e.g. Multiple Sclerosis, Parkinson's Disease)
      Paralysis of muscle (e.g. paraplegic)
      Problems with muscle tone (e.g. weakness, loss of tone, increased tone)
      Problems with muscle activity (e.g. impaired movements like tics, spasms, slow movements, rapid movements)

    The most common procedures done to diagnose problems with the muscles involve graphic records of how a specific muscle is reacting to some form of stimulus.

    The Nervous System

    The nervous system allows the body to adjust to the requirements of both the inside and outside of the body. A detected change in either environment is reported to the brain, which selects an apporpriate response and then brings about that change. This is a very complex process.

    The nervous system is made up of nervous tissue that consists of bundles of fibers that carry impulses throughout the body. The root word for nerve is neur/i or neur/o.

    Two different types of nerve cells are found in the nervous system:
    • Neurons carry nerve impulses back and forth through the body
    • Neuroglia are found between the neurons and act as a protection for the nueron.

    Neurons are made up of three main parts, each with a very distinct role:
    • The Cell Body contains all the structures that maintain the cell.
    • Dendritesare root-like structures that receive impulses and conduct them toward the cell body. The root for dendrites is dendr/o
    • The Axonextends away from the cell body and conducts the impulse away from the nerve body. Some axons are protected by a white fatty substance called myelin. The root for axon is axo/
    The 3 Major Structures of the Nervous System
    Central Nervous System:

    Consists of the brain and spinal cord which is protected by fluid and a series of membranes. Protection from trauma in the environment is obtained by the skull and the bones of the vertebrae. The brain is the information processing area and the spinal cord is the body's information super-highway.


    Peripheral Nervous System:

    Consist of cranial nerves which extend from the brain, and spinal nerves which come from the spinal cord.


    Autonomic Nervous System

    Consists of ganglia on either side of the spinal cord. Nerves of the autonomic nervous system control involuntary actions of the body which we are not able to control (e.g. heart rate, breathing)


    In order for the nervous system to carry on its many functions there must be transmission of messages back and forth from one part of the body to another. The nerves allow for this, and the process occurs smoothly with the help of neurotransmitters.


    Neurotransmitters are chemical substances that make it possible for the impulse to jump from one nerve cell to another. There are at least 40 neurotransmitters in the body, each with a very specific function. The space between the nerve cells is referred to as the synapse. An impulse will travel down a neuron to a synapse and then a neurotransmitter is released that allows the impulse to jump to the next neuron.

    Central Nervous Sytem
    The Central Nervous System is made up of the brain and spinal cord. The root for brain is either encephal/o or cerebr/o. The root for spine is spin/o and for spinal cord is myel/o. The brain, which is encased in the skull, is made up of several parts:

    • Cerebrum: The largest part of the brain which receives impulses from all areas of the body. The cerebrum holds our intellectual ability. It is divided into two hemispheres by a gap that extends down the middle of the tissue. These two areas are connected by bundles of nerves that allow the two hemispheres to function together. If the hemispheres become split for any reason, each can function independently but the normal integration of functiosn will not occur.
      The outer layer of the cerebrum is a thin gray layer called the cerebral cortex. The cerebrum is involved in sensory and motor function as well as thought, judgement and our perception.
    • Each brain hemisphere is divided into lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe.
    • Thalamus: Acts as a relay station for impulses coming into the brain. This area is responsible for detection of touch, temperature and pain. The root for thalamus is thalam/o
    • Hypothalamus: Located below the thalamus, it helps regulate the functions of the autonomic nervous system - appetite, temperature, sleep cycles and the amount of water retained by the body.
    • Brain Stem: Sometimes referred to as the "animal brain" because it is the site of the basic life functions of breathing, heart beat, blood pressure, ability to see and ability to hear. It is also responsible for the responses of coughing, sneezing and swallowing.
    • Cerebellum: Located just below the occipital lobe of the cerebrum, it is responsible for balance, coordination and equilibrium. Root for cerebellum is cerebell/o
    The Human Brain

    The human brain weighs only 3 pounds and looks like a gray, unshelled walnut, yet it is the body's most vital organ. It encases 100 billion or more nerve cells, and sends signals to thousands of other cells at speeds of more than 200 miles an hour. It defines who we are, yet it is influenced by what we do.

    Protection for the Brain
    • Skull: The bones that make up our skull protect the brain tissue from external trauma. The root for skull is crani/o.
    • Meninges: A series of three membranes that cover the brain tissue. The root for meninges is mening/o and meningi/o. The three membranes are the dura mater, archnoid mater and pia mater. In the space below the arachnoid mater and above the pia mater (subarachnoid) there is a fluid called cerebrospinal fluid that acts as a cushion to absorb trauma during a head injury. This fluid absorbs a great deal of the impact so the brain tissue doesn't become bruised.
    Blood-Brain Barrier
    A mechanism that prevents dangerous or toxic substances from leaving the blood stream and moving into brain tissue. It does allow necessary substances like oxygen and nutrition to pass through, into the brain.

    Spinal Cord

    The spinal cord extends from the base of the brain down the back in a canal referred to as the spinal canal. The cord consists of nerves that are encased in 31 vertebrae for protection. The spinal cord branches into 31 pairs of spinal nerves that extend from the cord to the limbs and lower parts of the body. The root for spinal cord is myel/o. Like the brain, it is protected by the three layers of meninges and the cerebrospinal fluid.



    Peripheral Nervous System

    The peripheral nervous system consists of the cranial nerves which extends from the brain and the spinal nerves which extend from the spinal cord. We have 12 pairs of cranial nerves and they are named for the area they affect or the function they are responsible for, such as the eyes, face, throat, mouth, tongue, thorax.


    THere are 31 pairs for spinal nerves, which are generally named for the artery they accompany or the body part they affect (e.g. the femoral nerve affects the muscles along the femur).



    Autonomic Nervous System

    This aspect of the nervous system is divided into 2 parts: the paraympathetic and sympathetic. Each division acts as a balancer of the activities of the other, allowing a state of homeostasis to exist in the body.


    The sympathetic system is concerned with preparing the body for emergency/stressful situations. To prepare a quick reaction in such situations, breathing rate, heart rate and blood circulation to the muscles is greatly increased, while rate of your digestion is decreased, since it is not a necessity in an emergency situation.


    The parasympathetic system returns your body to a state of calm after a stressful situation hass passed. It also maintains normal body functions during ordinary daily circumstances.



    Diagnostic Procedures


    The most common procedures used to diagnose problems of the nervous system involve the use of sound and dyes to create graphic pictures. Magnetic Resonance Imaging (MRI) uses a combination of radio waves and a strong magnetic field to create images in any part of the body. This procedure is used in diagnosing brain problems, as well as other problems in the body.


    Computerized Axial Tomography (CAT Scan) uses an X-Ray beam which rotates around the patient and details the structure to be examined at various depths. The information is then computerized and converted to a picture of that part of the body.



    Diseases of the Nervous System
    Injuries to the nervous system may be the result of one or a combination of the following:
    • Inflammation
    • Trauma
    • Decrease in blood circulation to the tissue resulting in death of tissue
    • Congenital injuries