Anatomical Directional Terms and Body Planes

Directional Terms

• Directional terms come in pairs of opposites and are based on the standard anatomical position
• Superior means above
• Inferior means below
• Anterior means toward the front (chest side) of the body
• Posterior means toward the back
• Medial means toward the midline of the body
• Lateral means away from the midline
• Ipsilateral means on the same side
• Proximal means closest to the point of origin or trunk of the body
• Distal means farthest away.
• Superficial means toward the body surface
• Deep means farthest from the body surface
• Intermediate means between
• Caudal means at or near the tail or posterior end of the body
• Visceral can mean deep
• Palmar describes the palm side of the hand
• Plantar describes the bottom of the foot
• Dorsal describes the back side of the hand

Body Reference Planes

• A plane is a two-dimensional surface with dimensions of length and width
• Body reference planes are used to locate or describe the location of structures in the body
• Three basic planes intersect at right angles to each other
• These can describe various relationships within the body when intersecting in the body's center
• The sagittal plane divides the body into left and right sides
• A plane that divides the body down the middle into equal left and right sides is the median sagittal plane
• The coronal plane divides the body into front (anterior or ventral) and back (posterior or dorsal)
• The transverse plane is parallel to the ground and divides the body into up (toward the head) and down (toward the feet)
• The oblique plane is slanted and lies between the horizontal and vertical planes

Body Cavities

• Body cavities are areas containing internal organs
• Dorsal and ventral cavities are the two main cavities
• Dorsal cavities are on the posterior (back side) and contain the cranial and spinal cavities
• Dorsal, caudal, and posterior mean the same thing
• Ventral cavities are on the front (anterior) of the body and are divided into the thoracic (chest) and abdominopelvic cavities
• The dorsal cavity is divided into cranial and vertebral cavities
• The cranial cavity (calvaria) surrounds and holds the brain
• The vertebral cavity includes the vertebrae (spinal column) and spinal cord
• The diaphragm (the main muscle of breathing) divides the ventral cavity into thoracic and abdominal cavities
• The thoracic cavity is surrounded by ribs and chest muscles, superior to the diaphragm and abdominopelvic cavity
• The thoracic cavity is divided into pleural cavities, containing the lungs and mediastinum containing the heart, pericardial membranes, large vessels, trachea, upper esophagus, thymus gland, lymph nodes, and other blood vessels and nerves
• Abdominopelvic cavities are divided into the abdominal and pelvic cavities
• The abdominal cavity is between the diaphragm and the pelvis, lined with a membrane, and contains the stomach, lower part of the esophagus, small and large intestines, spleen, liver, gallbladder, pancreas, adrenal glands, kidneys, and ureters
• The pelvic cavity contains the bladder, some reproductive organs, and the rectum
• The thoracic cavity is open at the top, and the abdominal cavity is open at the bottom
• Both cavities are bound on the back by the spine, and their shape can change
• Breathing is the primary way the shape of these two cavities changes

How Cavities Change Shape

• The abdominal cavity changes shape like a water-filled balloon
• Compressing the abdominal cavity bulges it into a different shape while breathing
• The abdominal cavity can change shape based on food and drink intake
• An increase in volume of the abdominal cavity decreases the volume in the thoracic cavity
• The thoracic cavity changes both shape and volume when you breathe and its quality affects the health of abdominal organs
• The health of organs affects the quality of breathing
• The oral cavity is the space in the mouth inside the teeth and gums, filled with the tongue when relaxed
• The nasal cavity is in the nose
• The orbital cavities hold the eyes

Body Regions

• Body regions describe areas with a special function or are supplied by specific blood vessels or nerves
• Nine abdominal regions exist
• Right and left hypochondriac regions are on either side of the epigastric region and contain the diaphragm, some of the kidneys, the right side of the liver, the spleen, and part of the pancreas
• The epigastric region is superior to the umbilical region and contains most of the pancreas, part of the stomach, liver, inferior vena cava, abdominal aorta, and duodenum
• Right and left lumbar (lateral) regions are on either side of the umbilical region and contain portions of the large and small intestines and kidneys
• The umbilical region is the area around the umbilicus (belly button) and includes sections of the large and small intestines, inferior vena cava, and abdominal aorta
• Right and left iliac (inguinal) regions are on either side of the hypogastric region and include portions of the large and small intestines
• The hypogastric (pubic) region is inferior to the umbilical region and contains parts of the sigmoid colon, the urinary bladder and ureters, the uterus and ovaries (women), and portions of the small intestines

Body Quadrants

• Quadrants divide the body for diagnostic and descriptive purposes, including, right upper, right lower, left upper, and left lower
• Quadrants are defined by drawing imaginary lines vertically and horizontally through the umbilicus (belly button)
• The right upper quadrant (RUQ) contains the right lobe of the liver, gallbladder, part of the transverse colon, part of the pylorus, hepatic flexure, right kidney, and duodenum
• The right lower quadrant (RLQ) contains the cecum, ascending colon, small intestine, appendix, bladder (if distended), right ureter, right spermatic duct (men), right ovary and right tube, and uterus (if enlarged)
• The left upper quadrant (LUQ) contains the left lobe of the liver, stomach, small intestine, transverse colon, splenic flexure, pancreas, left kidney, and spleen
• The left lower quadrant (LLQ) contains the small intestine, left ureter, sigmoid flexure, descending colon, bladder (if distended), left spermatic duct (men) left ovary, and the left tube/uterus (if enlarged)

Microscopy

• Microscopes obtain a magnified image of minute objects or details; understanding their parts and functions is key
• An eyepiece is used to view objects; it is located at the microscope's tip
• The eyepiece holder, known as the eyepiece tube, mounts the eyepiece directly over the objective lens
• Objective lenses are the primary lenses for viewing specimens, having magnifications of 40x–100x
• A nose piece (revolving turret) retains objective lenses
• Adjustment knobs are used to focus the microscope, including coarse and fine adjustment knobs
• A stage displays the specimen, held by stage clips; a mechanical stage enables controlling the slides by movement

Microscope Components

• The aperture is a hole in the microscope stage through which transmitted light from the source enters
• The microscopic illuminator provides the light source and collects light from an outside source using a low voltage
• Condensers gather and concentrate light from the illuminator into the sample and are essential for clear images at high magnifications
• The diaphragm regulates how much light gets to the specimen
• Condenser focus knobs control the light's focus on the specimen by raising or lowering the condenser
• The Abbe condenser facilitates high magnification (over 400X)

The Cell

• A cell is the basic unit of life and the smallest structure capable of basic processes like nutrient intake, waste expulsion, and reproduction
• Microscopic organisms (bacteria and protozoa) are unicellular, while plants, animals, and fungi are multicellular
• Cells carry out thousands of biochemical reactions each minute and reproduce new cells
• Cells vary in size; the smallest, a mycoplasma, measures 0.0001 mm in diameter
• Some nerve cells can exceed 3 m in length
• Human cells range from .00076 mm to ten times larger
• Cells present an array of shapes; some resemble rods, others are slipper-shaped or change shape as they move around, and plant cells resemble boxes or cubes
• Shape is typically tailored to the cell's job
• Molecules are nonliving structures and components of cells
• Proteins, nucleic acids, carbohydrates, and lipids are four molecules that underlie cell structure and functions
• Proteins speed up chemical reactions, and DNA contains hereditary information
• RNA works with DNA to build thousands of proteins the cell needs

Cell Division

• Somatic or body cells divide at the end of a process called the cell cycle
• During the cell cycle replicated chromosomes divide (karyokinesis) with division of cytoplasm (cytokinesis), creating a copy and distributing identical chromosomes to two daughter cells
• During interphase each chromosome replicates or doubles, an exact copy
• During mitosis chromosomes undergo four distinct phases, including prophase, metaphase, anaphase, and telophase
• Interphase involves replication/doubling of chromosomes, and a spherical nucleus is visible
• During prophase, chromosomes become condensed and visible, and spindle fibers appear as the nucleus, nucleolus, and nuclear membrane disappear
• During metaphase, chromosomes line up in the center, with centromeres attached to spindle fibers
• During anaphase the chromatids separate at the centromere and move to the poles or ends of the cell
• Telophase has chromatids at the poles that uncoil and spindle fibers disappear as the nucleus reappears, and involves divisions of cell cytoplasm which forms a cell wall in plants and furrows outer edges to cleave animal cells

Learn about directional terms in anatomy, including superior, inferior, anterior, and posterior. Understand body reference planes and their use in locating anatomical structures. Covers medial, lateral, ipsilateral, proximal, and distal.