2.1 Anatomic Reference Systems

anatomic reference systems

are used to describe the locations of the structural units of the body

anatomy

the study of the structures of the body

physiology

the study of the functions of the structures of the body

anatomic position

• describes the body standing in the standard position

• includes: standing up straight so that the body is erect and facing forward; holding the arms at the sides with the hands turned so that the palms face toward the front

body planes

• imaginary vertical and horizontal lines used to divide the body into sections for descriptive purposes

• these planes are aligned to a body standing in the anatomic position

vertical plane

an up-and-down plane that is at a right angle to the horizon

sagittal plane

a vertical plane that divides the body into unequal left and right portions

midsagittal plane

also known as the midline, is the sagittal plane that divides the body into equal left and right halves

frontal plane

• a vertical plane that divides the body into anterior (front) and posterior (back) portions

• also known as the coronal plane, it is located at right angles to the sagittal plane

horizontal plane

a flat, crosswise plane, such as the horizon

transverse plane

• a horizontal plane that divides the body into superior (upper) and inferior (lower) portions.

• can be at the waist or at any other level across the body

ventral

refers to the front, or belly side, of the organ or body

dorsal

refers to the back of the organ or body

anterior

• situated in the front

• also means on the front or forward part of an organ

• ex: the stomach is located anterior to (in front of) the pancreas

• also used in reference to the ventral surface of the body

posterior

• situated in the back. It also means on the back part of an organ

• ex: the pancreas is located posterior to (behind) the stomach

• is also used in reference to the dorsal surface of the body

superior

• uppermost, above, or toward the head

• ex: the lungs are located superior to (above) the diaphragm

inferior

• lowermost, below, or toward the feet

• ex: the stomach is located inferior to (below) the diaphragm

cephalic

toward the head

caudal

toward the lower part of the body

proximal

• situated nearest the midline or beginning of a body structure

• ex: the proximal end of the humerus (bone of the upper arm) forms part of the shoulder

distal

• situated farthest from the midline or beginning of a body structure

• ex: the distal end of the humerus forms part of the elbow

medial

• the direction toward, or nearer, the midline

• ex: the medial ligament of the knee is near the inner surface of the leg

lateral

• the direction toward, or nearer, the side of the body, away from the midline

• ex: the lateral ligament of the knee is near the side of the leg

body cavities

which are the dorsal (back) and the ventral (front) cavities, are spaces within the body that contain and protect internal organs

dorsal cavity

which is located along the back of the body and head, contains organs of the nervous system that coordinate body functions and is divided into two portions: cranial and spinal cavities

cranial cavity

which is located within the skull, surrounds and protects the brain

spinal cavity

which is located within the spinal column, surrounds and protects the spinal cord

ventral cavity

which is located along the front of the body, contains the body organs that sustain homeostasis

homeostasis

the processes through which the body maintains a constant internal environment

thoracic cavity

• also known as the chest cavity or thorax, surrounds and protects the heart and the lungs.

• the diaphragm is a muscle that separates the thoracic and abdominal cavities

abdominal cavity

• contains the major organs of digestion

• this cavity is frequently referred to simply as the abdomen

pelvic cavity

the space formed by the hip bones and contains the organs of the reproductive and excretory systems

abdominopelvic cavity

refers to these two cavities as a single unit

inguinal

• which means relating to the groin, refers to the entire lower area of the abdomen

• this includes the groin, which is the crease at the junction of the trunk with the upper end of the thigh

regions of the thorax and abdomen

comprise a descriptive system that divides the abdomen and lower portion of the thorax into nine parts

right and left hypochondriac regions

• are covered by the lower ribs

• the term hypochondriac means below the ribs

• this term also describes an individual with an abnormal concern about his or her health

epigastric region

located above the stomach

right and left lumbar regions

• located near the inward curve of the spine

• the term lumbar describes the part of the back between the ribs and the pelvis

umbilical region

• which is commonly known as the belly button or navel

• this pit in the center of the abdominal wall marks the point where the umbilical cord was attached before birth

right and left iliac regions

located near the hip bones

hypogastric region

located below the stomach

peritoneum

a multilayered membrane that protects and holds the organs in place within the abdominal cavity

parietal peritoneum

the outer layer of the peritoneum that lines the interior of the abdominal wall

mesentery

a fused double layer of the parietal peritoneum that attaches parts of the intestine to the interior abdominal wall

visceral peritoneum

the inner layer of the peritoneum that surrounds the organs of the abdominal cavity

retroperitoneal

• located behind the peritoneum

• ex: the location of the kidneys is retroperitoneal with one on each side of the spinal column

peritonitis

inflammation of the peritoneum