RT CT BASICS Flashcards
How is the body divided for imaging purposes?
the axial, coronal, oblique or orthogonal, sagittal and transverse planes.
What is the Axial Plane?
An axial plane divides the body into cranial, or superior, and caudal, or inferior, portions. The axial plane often is referred to as the transverse plane,
What is the Coronal Plane?
A coronal plane separates the body into anterior and posterior portions, also termed ventral and dorsal. The midcoronal plane divides the body into equal anterior and posterior halves.
What is the Sagittal Plane?
The sagittal plane divides the body into right and left halves. Midsagittal refers to the plane that divides the body into equal right and left halves.
What is the Oblique Planes?
Oblique planes, also referred to as orthogonal planes, run at a slant through the body.
The Directional Terminology terms used most frequently are:
Anterior – toward the front of the body.
Posterior – toward the back of the body.
Caudal – toward the inferior part of the body (away from the head).
Cranial – toward the upper part of the body (toward the head).
Proximal – toward or above.
Distal – away from or beneath.
Dorsal – the back portion of the body (posterior surface).
Ventral – toward the anterior surface of the body.
Superior – above or on top of.
Inferior – below or underneath.
Lateral – away from the body or sagittal plane.
Medial – toward the body or sagittal plane.
Prone – lying face down on the ventral surface.
Supine – lying face up on the dorsal surface.
Directional Terminology - Anterior
toward the front of the body.
Directional Terminology - Posterior
toward the back of the body.
Directional Terminology - Caudal
toward the inferior part of the body (away from the head).
Directional Terminology - Cranial
toward the upper part of the body (toward the head).
Directional Terminology - Proximal
toward or above.
Directional Terminology - Distal
away from or beneath.
Directional Terminology -Dorsal
he back portion of the body (posterior surface).
Directional Terminology -Ventral
oward the anterior surface of the body.
Directional Terminology -Superior
above or on top of.
Directional Terminology - Inferior
below or underneath.
Directional Terminology - Lateral
away from the body or sagittal plane.
Directional Terminology - Medial
toward the body or sagittal plane.
Directional Terminology - Prone
lying face down on the ventral surface.
Directional Terminology - Supine
lying face up on the dorsal surface.
formation of a blastocyst
which is implanted in the endometrial layer of the uterine wall about seven days after ovulation or around the 21st day of the menstrual cycle.
HCG
secretion that comes from the blastocyst to avoid being aborted by the uterus. Pregnancy tests are based on the presence of HCG in a woman’s blood or urine
formation of primary germ layers
During implantation, changes occur to the inner cell mass of the blastocyst, resulting in the formation of primary germ layers.
amnionic cavity
develops in the inner cell mass as does a two-layered, flattened embryonic disk. The primary germ layers are the ectoderm, endoderm and mesoderm.
All human tissue and organs
Embryonic human development begins at this point. The embryonic stage lasts six weeks, from the beginning of week three through week eight.
Human structures that develop from the ectoderm include the:
1) Epidermis of the skin.
2) Hair, nails and skin glands.
3) Lenses of the eyes.
4) Enamel of the teeth.
5) Adrenal medulla.
6) Receptor cells of the organs of sense.
7) Lining of the oral and nasal cavities, vagina and anus.
Central Nervous System
about 18 to 20 days after conception, the human central nervous system develops from a thickened area of the ectoderm called the neural plate.
The neural plate
develops into a neural crest and a neural tube
The neural tube
forms the human brain and spinal cord
neural crest
forms the majority of the structures of the peripheral nervous system
The neural tube initially is open at both the caudal and cranial ends.
The cranial end closes around 24 days after conception, and the caudal end closes about two days after that. Differentiation and growth of the neural tube is greatest at its cranial end.
three primary vesicles of the cranial end of the neural tube
the prosencephalon or forebrain, the mesencephalon or midbrain, and the rhombencephalon or hindbrain.
prosencephalon
forebrain
mesencephalon
midbrain
rhombencephalon
hindbrain
bout a week after differentiation, two of the three primary vesicles, which are they?
the prosencephalon and rhombencephalon, divide.
what develops from the prosencephalon
The telencephalon and the diencephalon
what develops from the rhombencephalon
develops into the metencephalon and the myelencephalon.
the three primary vesicles become what?
five secondary vesicles.
what does the telencephalon develop into?
the cerebral hemispheres and basal ganglia
what does the diencephalon develop into?
the thalamus, hypothalamus, pineal gland, third ventricle and optic tract.
what does the mesencephalon develop into?
ectum, corpora quadrigemina, cerebral peduncles and cerebral aqueduct.
what does the metencephalon develop into?
the pons and part of the medulla oblongata, cerebellum and part of the fourth ventricle
what does the myelencephalon develop into?
the remaining parts of medulla oblongata and fourth ventricle
Endoderm
Structures that develop from the endoderm include the epithelium of the digestive tract, liver, pancreas, urinary bladder, urethra and respiratory tract. The thyroid, parathyroid and thymus glands also are formed by the endoderm.
Mesoderm
The mesoderm forms the dermis of the skin; cardiac, skeletal and smooth muscles; connective tissue, including cartilage and bone; the epithelium of the blood vessels, joint cavities and serous membranes; the kidneys, ureters and adrenal cortex; and the epithelium of the female and male reproductive systems.
What is The major bony structure of the head
the cranium, also called the cranial vault.
the cranium, also called the cranial vault.
This structure encases and protects the brain and pituitary gland. The brain and pituitary gland are vital to the integration of the body’s activities and functions.
Scalp
The skull, or cranium, is covered by the scalp. Ironically, the letters making up the word “scalp” actually stand for the layers that compose it.
S C A L P
S – skin. C – connective tissue. A – aponeurosis. L – loose connective tissue. P – periosteum.
Where does the scalp receives its blood supply
from the external carotid artery, which is the reason it can bleed profusely when lacerated.
Skull
The term “skull” refers not only to the bones of the cranium, but also to the bones of the facial skeleton. The skull is said to be the most complex bony structure in the body, consisting of 22 bones that are connected by sutures, which are immovable joints.
The eight actual cranial bones
include one frontal bone, two parietal bones, two temporal bones, one ethmoid, one sphenoid and one occipital.
What is the cavity floor divided into?
anterior, middle and posterior regions called fossae.
Frontal Bone
The frontal bone forms the forehead and superior portions of the orbits. Housed within the frontal bone near its midline are the frontal paranasal sinuses. These sinuses connect to the nasal cavity between the middle and inferior nasal conchae, via the middle nasal meatus. The frontal sinuses usually are visible radiographically by the age of 7.
Parietal Bones
The paired parietal bones form most of the superior portion and some of the lateral aspects of the cranium. They are located superior to the temporal bone and the posterior aspects of the sphenoid bone.
Temporal Bones
The two temporal bones are inferior to the parietal bones and form part of the lateral portions of the cranium, as well as its floor or base. Both temporal bones also have a squamous portion that forms the inferolateral aspects of the cranium. A mastoid process is located on the posterior aspect of each temporal bone. Extending medially from the temporal bone is its petrous portion.
Temporal Bones – Petrous Portion
The wedge-shaped petrous portion of the temporal bone forms part of the base of the cranium and houses the organs of hearing. The petrous portion has three chambers: external, middle and inner. The external structures consist of the auricle and the external auditory meatus (EAM) or canal.
Auditory Ossicles
The EAM conducts sound to the tympanic membrane, also known as the eardrum, which is located in the air-filled middle ear. The middle ear, or tympanic cavity, also houses three auditory ossicles: the incus, malleus and stapes.
The tympanic membrane amplifies and transmits sound vibrations to the auditory ossicles. The auditory ossicles then convey the sound to the oval window of the inner ear. The inner ear, which is filled with fluid, contains the vestibule, semicircular canals and the cochlea.
Vestibule
The vestibule and semicircular canals control balance and equilibrium, while the cochlea is responsible for hearing. The vestibule is located between the semicircular canals and the cochlea. The semicircular canals are easily identified on CT images because they have three separate passages located at right angles to each other. The round window of the inner ear is located at the basal turn of the cochlea. The round window allows the fluid in the inner ear to shift slightly so that sound waves can be propagated.
This page shows the hearing organs in the coronal plane and the proper orientation of the petrous portion of the temporal bone and its enclosed structures. The petrous portion is said to be the densest and one of the most intricate bones in the body. Because the petrous portion of the temporal bone houses the hearing organs, CT has become the major tool to diagnose pathological conditions involving these structures.
Ethmoid
The ethmoid bone is situated between the orbits and forms most of their medial walls. A thin piece of bone called the perpendicular plate extends from the inferior portion of the ethmoid and forms a part of the nasal septum. The middle and superior nasal conchae are considered part of the ethmoid bone.
The ethmoid also contains the ethmoid paranasal sinuses, which are composed of numerous air sacs. Although newborn babies have ethmoidal air sacs, these sacs generally do not appear radiographically until around age 3. The ethmoid sinuses connect with the nasal cavity by way of the superior and middle meatuses.
Sphenoid
The sphenoid bone lies at the base of the skull, anterior to the temporal bones. Many imaging professionals describe this bone as appearing “bat-like.” In keeping with that description, the sphenoid bone has two parts referred to as the greater and lesser wings. These wings form the anterolateral parts of the cranium and the lateral walls of the orbits. Embedded within the central portion of the sphenoid bone is the sella turcica, which houses the pituitary gland.
Sphenoid Sinus
The sphenoid sinuses are also located within the sphenoid bone. These sinuses are situated immediately posterior to the ethmoid sinuses and nasal cavity and communicate with that cavity by way of the sphenoethmoidal recess, which is situated superior to the superior nasal conchae.
The sphenoid is separated from the optic nerves, optic chiasm and pituitary gland by a sliver of bone. Although small sphenoid sinuses may present in newborns, they are most radiographically distinguishable after age 2. This page shows the sphenoid sinuses on a transverse CT image of the head.
Occipital Bone
The occipital bone is the most posterior of the cranial bones. It forms the posterior part of the cranium and part of the base of the skull. The occipital bone contains a large foramen called the foramen magnum. In addition, on either side of the inferior portion of the occipital bone, there are condyloid processes called the occipital condyles. The occipital condyles articulate with the lateral masses of the first cervical vertebra.