Anatomy and Physiology Essentials

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CHAPTER 1

Introducing the Human Body

1.1 Anatomy and Physiology

Anatomy - Anatomy is the study of the structure of body parts. It is also the study of the relationship among these parts. The heart, for example, consists of chambers, valves, and associated blood vessels.

Physiology - Physiology is the study of the function of body parts. The parts of the heart, for example, work together to pump the blood throughout the body.

There is a close association between anatomy and physiology. Structure complements function. The four chambers of the heart have muscular walls that contract to pump the blood. The makeup of the valves prevents the backflow of blood.

1.2 Levels of Organization

The anatomy of the human body is composed of different levels of organization. These levels represent a series of steps. Each level is a building step for the next level.

These levels are:

Atom - All matter consists of elements. These simple substances exist as discrete, submicroscopic particles called atoms.

Molecule - Atoms bond into molecules. About 65% of human body weight consists of water molecules. Smaller molecules bond into larger molecules that have biological functions. Monosaccharides (i.e., glucose), for example, bond into polysaccharides (i.e., starch). These carbohydrates are an energy source.

Organelle - Molecules compose the parts of the cell called organelles. Each of these parts carries out a specific function. The ribosome, for example, is the site of protein synthesis.

Cell - The cell is the smallest unit displaying the properties of life. Cells tend to specialize. There are about 200 different kinds of specialized cells in the human body. Neurons (nerve cells) send signals. Leukocytes (white blood cells) fight infection.

Tissue - Similar cells function together in a tissue. Muscle cells work together in skeletal muscle tissue. These cells contract, producing body movement.

Organ - Two or more tissues work together in an organ. The heart consists of several tissue types.

Organ Systems - Organs with related functions are part of the same organ system. The heart and blood vessels are organs of the circulatory system. They function to circulate the blood throughout the body.

Organism - All organ systems make up the organism. The organ systems of the human body include the nervous, circulatory, respiratory, and digestive systems.

1.3 Anatomical Terms

Anatomical terms are used to describe the makeup of the body accurately and concisely. All of these terms are used with reference to anatomical position. In this position the subject studied is facing forward and standing erect. The arms are hanging at the sides. The palms and toes are pointed forward.

1.3.1 Directional Terms

Directional terms compare the relative position of one body part to another body part. These terms occur in pairs. The members of each pair have opposite meanings.

Superior/Inferior - Superior means closer to the head. Inferior means closer to the feet. The neck is superior when compared to the chest, which is inferior. When compared to the abdomen, the chest is superior and the abdomen is inferior.

Anterior/Posterior - Anterior (ventral) refers to a part that is closer to the front of the body. Posterior (dorsal) refers to a part that is closer to the back. The heart is anterior when compared to the vertebral column, which is posterior. When compared to the sternum (breastbone), the heart is posterior and the sternum is anterior.

Medial/Lateral - Medial refers to a part that is closer to an imaginary midline passing vertically through the body. Lateral refers to a part that is further from this midline. The nose is medial when compared to the eyes (lateral). When compared to the ears, the eyes are medial. The ears are lateral.

Proximal/Distal - Proximal refers to a part of a limb that is closer to the trunk (torso) of the body. Distal refers to a limb part that is further from the trunk. The forearm is proximal when compared to the wrist (distal). The wrist is proximal when compared to the fingers (distal).

Other directional terms include:

Superficial - closer to the surface of the body

Deep - further away from the surface of the body

Parietal - referring to the wall of a body cavity

Visceral - referring to an organ within the body cavity

1.3.2 Planes and Sections of the Body

Incisions can be made through the body to study the internal anatomy. These sections represent imaginary planes.

Sagittal Plane - A sagittal plane passes through the body longitudinally, dividing it into left and right regions. A midsagittal section passes through the midline of the body.

Coronal (Frontal) Plane - A coronal plane passes through the body longitudinally, dividing it into anterior and posterior regions.

Transverse Plane - A transverse plane passes through the body horizontally, dividing it into superior and inferior regions.

These sections can also pertain to organs of the body. Sagittal, coronal, and transverse planes also pass through the heart.

1.3.3 Body Cavities

There are two main cavities of the human body, the dorsal cavity and ventral cavity. Each cavity is divided into subcavities.

Dorsal Cavity - The dorsal cavity consists of the cranial cavity and spinal cavity. The cranial cavity is formed by the superior bones of the skull. It contains the brain. The spinal cavity is formed by a series of vertebrae. It contains the spinal cord.

Ventral Cavity - The ventral cavity consists of thoracic and abdominopelvic subcavities.

The thoracic cavity is superior to the diaphragm. It is subdivided into a left and right pleural cavity. The pleural cavities contain the lungs. The mediastinum is the space between the pleural cavities. It contains the trachea (windpipe), esophagus, thymus gland, and heart. The heart is contained within a separate cavity of the mediastinum, the pericardial cavity.

The abdominopelvic cavity is inferior to the diaphragm. The larger abdominal portion contains the liver, gallbladder, stomach, small intestine, and most of the large intestine. The smaller pelvic portion contains the large intestine, bladder, and reproductive organs.

1.4 Organ Systems

Organs with related functions are part of the same organ system. These systems are:

Integumentary System - The skin and accessory organs comprise the integumentary system. This system protects and regulates body temperature.

Skeletal System - The skeletal system consists of the bones and articulations (joints). This system provides protection and support. Skeletal muscles pull on bones to produce movements. The skeletal system also stores minerals and produces blood cells.

Muscular System - The skeletal muscles contract to produce body movements. The muscles also produce body heat.

Nervous System - The nervous system sends signals throughout the body. The central nervous system consists of the brain and spinal cord. The peripheral nervous system consists of the cranial and spinal nerves.

Endocrine System - The glands of the endocrine system secrete chemical messages called hormones. These messages regulate processes such as growth and mineral balance.

Circulatory System - The circulatory system transports substances to and from body cells. The lymphatic system is part of the circulatory system. One of its functions is to protect the body from disease.

Respiratory System - The respiratory system distributes and exchanges gases between the body and external environment.

Digestive System - The digestive system prepares food molecules for use by the cells of the body.

Urinary System - The urinary system controls the composition and volume of the blood. It eliminates wastes.

Reproductive System - The male reproductive system produces sex cells. It transfers these cells to the female reproductive system. The female reproductive system produces sex cells and receives the male sex cells. It also provides the internal environment for the development of the embryo and fetus.

1.5 Homeostasis

Homeostasis is the maintenance of relatively constant conditions of the internal environment of the body. The internal environment includes the tissue fluid that bathes the cells. This tissue fluid is formed from the blood. Characteristics that are controlled include:

Temperature - at 37° C

Blood Sugar - 100 mg per 100 ml of blood

pH of the Blood - at 7.4

These characteristics are controlled by negative feedback. Receptors sense changes in the internal environment. Through signals from the nervous and endocrine systems, responses reverse the trend of these changes. For example, if blood sugar increases, the pancreas secretes insulin. This hormone signals responses that decrease the level of glucose in the blood.

If body temperature decreases, responses increase body temperature. One response is the shivering of the skeletal muscles.

CHAPTER 2

Chemistry of Life

2.1 Elements and Atoms

Element - An element is a substance that cannot be broken down into simpler substances by normal chemical reactions. The four most common elements of the human body are carbon, hydrogen, oxygen, and nitrogen. Elements exist as discrete, submicroscopic particles called atoms.

Atom - Each element consists of one kind of atom. An atom is the smallest particle that displays the chemical properties of an element. The three main types of subatomic particles of an atom are the proton, neutron, and electron.

Atomic Weight - The atomic weight (mass) is the total number of protons and neutrons in the nucleus of an atom. For example, the atomic weight of carbon is usually 12. For oxygen it is usually 16.

Atomic Number - The atomic number is