ANA 301 Osteology & Scalp Flashcards
What is the cranium?
The cranium (skull) is the skeleton of the head
•The many bones of the head collectively form the skull
• Most of these bones are interconnected by sutures which are immovable fibrous joints
Parts of the cranium
the neurocranium /cranial vault
the viscerocranium/ facial skeleton
What is the neurocranium?
is the bony covering (case) of the brain and its membranous coverings, the cranial meninges
•It also contains proximal parts of the cranial nerves and the vasculature of the brain
What are the parts of the neurocranium?
A dome-like roof called the calvaria (skullcap)
and a floor or cranial base (basicranium)
What are the 4 singular bones of the neurocranium?
frontal
occipital
ethmoidal
sphenoidal
What are the 2 sets of paired bones of the neurocranium?
Temporal
Parietal
What is unique about the ethmoid bone?
The ethmoid bone is an irregular bone that makes a relatively minor midline contribution to the neurocranium but is primarily part of the viscerocranium
Briefly describe the viscerocranium (facial skeleton)
comprises the facial bones
•forms the anterior part of the cranium
• consists of the bones surrounding the mouth (upper and lower jaws), nose/nasal cavity, and most of the orbits (eye sockets or orbital cavities)
What are the bones that make up the viscerocranium?
consists of 15 irregular bones:
*3 are singular bones
*6 bones occur as bilateral pairs
●The three singuar bones are:
➢Mandible
➢Ethmoid
➢Vomer
●The 6 bilateral paired bones are:
➢Maxillae
➢inferior nasal conchae
➢zygomatic
➢palatine
➢nasal
➢lacrimal bones
Briefly describe the maxilla
contribute the greatest part of the upper facial skeleton,
•form the skeleton of the upper jaw
•It is fixed to the cranial base
Briefly describe the mandible and what makes it movable
*forms the skeleton of the lower jaw,
*It is movable because it articulates with the cranial base at the temporomandibular joints (TMJs)
is a U-shaped bone
Its alveolar process supports the mandibular teeth.
Features of the Anterior / Facial (Frontal) Aspect Of The Cranium
the frontal bone
zygomatic bones
orbits
nasal region
maxillae
mandible
What is the frontal bone?
• it is a squamous (flat) part
•forms the skeleton of the forehead
The frontal bone articulates inferiorly with__________
the nasal and zygomatic bones.
The supraorbital margin of the frontal bone has_______________
a supraorbital foramen (notch) for the passage of the supraorbital vessels and nerves
Just superior to the supraorbital margin is a ridge called the____________
superciliary arch
Between these arches is a smooth, slightly depressed area called the______________
GLABELLA
Describe the glabella and ophryon
The Glabella is the anterior-most projecting part of the forehead
Just above the glabella is a point on the midline of the forehead called the Ophyron
On the midline of the mandible is the the most anterior point on the mandible which is the most prominent part of the chin called the____________
pogonion
The intersection of the frontal and nasal bones is called the ___________
NASION, a depressed area (bridge of the nose)
The frontal bone also articulates with the___________
lacrimal, ethmoid, and sphenoids bones
Describe the nasal region
it’s made up of a pair of nasal bones which are joined together at midline by the nasal septum
Inferior to these nasal bones is a pear-shaped pyriform aperture
the bony nasal septum can be observed through this aperture dividing the nasal cavity into the right and left parts
On the lateral wall of each nasal cavity are curved bony plates called nasal conchae
The two maxillae are united at the___________
intermaxillary suture in the median plane
Describe the alveoli processes
their alveolar processes include the tooth sockets (alveoli) and house the maxillary teeth
The maxilla articulate with______the anteriorly and________laterally
frontal bone
zygomatic bones
On the body of the maxilla is the infraorbital foramen for passage of the
infraorbital nerve and vessels
Parts of the mandible
of a horizontal part (the body)
and a vertical part (the ramus )
Inferior to the second premolar teeth are the___________________
mental foramina for the passage of the mental nerves and vessels
Describe the base of the mandible
The base of the mandible has a midline swelling called the mental protuberance
Lateral to the mental protuberance on either side is a slightly more pronounced bumps called the mental tubercles
What is the zygomatic bone?
Also known as cheek bone, malar bones
On the lateral aspect of the zygomatic bone is a foramen called the______________
zygomaticofacial foramen
this foramen allows for the passage of the zygomaticofacial nerve
The zygomatic bone articulates with the_________
frontal, sphenoidal, maxillae and temporal bones
Describe an injury to the superciliary arches
The superciliary arches are relatively sharp bony ridges; consequently, a blow to them (e.g., during boxing) may lacerate the skin and cause bleeding. Bruising of the skin surrounding the orbit causes tissue fluid and blood to accumulate in the surrounding connective tissue, which gravitates into the superior (upper) eyelid and around the eye
Describe Malar Flush
The zygomatic bone was once called the malar bone.
Clinically the term malar flush refers to redness of the skin covering the zygomatic prominence (malar eminence), which is associated with a rise in temperature in various fevers occurring with certain diseases, such as tuberculosis
The Superior aspect of the skull is also called the___________
calvaria or skull cap
Bones that make up the calvaria include
Frontal bone (unpaired)
Paired parietal bones
Occipital bone (unpaired)
Landmarks of the outer surface of the skull include
The frontal bone articulates with the paired parietal bones at the coronal suture
The two parietal bones articulate with each other at the sagittal suture
The paired parietal bones articulate with the occipital bones at the lambdoid suture
The junction(intersection) between the coronal and sagittal sutures is called the bregma
The junction (intersection) between the sagittal suture and lambdoid sutures is called the lambda
The vertex is the most superior point of the skull near the midpoint of the sagittal suture
The parietal foramen on the parietal bone is variable, and it allows for the passage of emissary veins
Obelion: The region of the skull between the two parietal foramina where the closure of the sagittal suture usually begins
Describe linear calvarial fractures
the most frequent type
usually occur at the point of impact; but fracture lines often radiate away from it in two or more directions
Describe the depressed fractures of the calvaria
this can results from hard blows in thin areas of the calvaria in which a bone fragment is depressed inward, compressing and/or injuring the brain
Describe comminuted fractures
the bone is broken into several pieces
If the area of the calvaria is thick at the site of impact, the bone may bend inward without fracturing; however, a fracture may occur some distance from the site of direct trauma where the calvaria is thinner
Describe contrecoup (counterblow) fracture
no fracture occurs at the point of impact, but one occurs on the opposite side of the cranium
Describe the obliteration of the Cranial Sutures
The obliteration of sutures between the bones of the calvaria usually begins between the ages of 30 and 40 years on the internal surface and approximately 10 years later on the external surface
Obliteration of sutures usually begins at the bregma and continues sequentially in the sagittal, coronal, and lambdoid sutures
The halves of the frontal bone in the newborn are separated by the______________
frontal suture
the frontal and parietal bones in newborns are separated by the_____________
coronal suture
the maxillae in newborns are separated by the_______________
intermaxillary suture
a newborn’s mandible consists of two halves united in the median plane by the_______________
mandibular symphysis
the union of the mandible begins during_____________
the 1st year and the halves are fused by the end of the 2nd year
What parts of the skull are not present at birth in a newborn? When do they develop?
No mastoid process at birth
No styloid process
The mastoid processes form gradually during the 1st year
The bones of the calvaria of a neonate are separated by membranous intervals called___________
fontanelles
Fontanelles of a newborn include
anterior fontanelle
posterior fontanelle
paired sphenoidal fontanelle
Paired mastoid fontanelles
Describe the size shape, boundary, location and closure of the anterior fontanelle
intro: the largest fontanelle
shape: diamond or star-shaped
boundary: bounded by the halves of the frontal bone anteriorly and the parietal bones posteriorly.
Location: at the junction of the sagittal, coronal, and frontal sutures, the future site of the bregma
closure: By the 18 months of age, the surrounding bones have fused and the anterior fontanelle is no longer clinically palpable
Describe the future of the frontal bone of a newborn
Union of the halves of the frontal bone begins in the 2nd year
In most cases, the frontal suture is obliterated by the 8th year
in approximately 8% of people
a remnant of the frontal suture persists called the
metopic suture
Describe the shape, boundary, location and closure of the posterior fontanelle
Shape: is triangular
boundary: bounded by the parietal bones anteriorly and the occipital bone posteriorly
location: at the junction of the lambdoid and sagittal sutures, the future site of lambda
Closure: begins to close during the first few months after birth and by the end of the 1st year, it is small and no longer clinically palpable
Discuss the sphenoidal and mastoid fontanelles in newborns
Sphenoidal and mastoid fontanelles
overlain by the temporal muscle,
fuse during infancy and are less important clinically than the midline fontanelles
Briefly describe the closure of the maxilla and mandible
The halves of the mandible fuse early in the 2nd year
The two maxillae and nasal bones usually do not fuse
During the passage of the fetus through the birth canal what typically occurs to the calvaria of a newborn?
the halves of the frontal bone become flat, the occipital bone is drawn out, and one parietal bone slightly overrides the other
Describe the enlargement of the calvaria in the stages of human development
The fibrous sutures of the calvaria also permit the cranium to enlarge during infancy and childhood
The increase in the size of the calvaria is greatest during the first 2 years, the period of most rapid brain development
The calvaria normally increases in capacity for 15-16 years
After this, the calvaria usually increases slightly in size for 3-4 years as a result of bone thickening
Premature closure of the cranial sutures is called________________
craniosynostosis results in several cranial malformations
Describe the premature closure of the sagittal suture
the anterior fontanelle is small or absent, results in a long, narrow, wedge-shaped cranium, a condition called scaphocephaly
What is plagiocephaly?
When premature closure of the coronal or the lambdoid suture occurs on one side only,
What is oxycephaly or turricephaly>
Premature closure of the coronal suture results in a high, tower-like cranium
The lateral aspect of the skull includes
lateral part of the neurocranium
Lateral part of the viscerocranium (facial skeleton)
bones forming the lateral portion of the neurocranium include
the frontal, parietal, occipital, sphenoid, and temporal bones