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Questions and Answers
What condition is characterized by a small skull due to the early closure of fontanels?
What condition is characterized by a small skull due to the early closure of fontanels?
Which type of suture has a tooth-like appearance?
Which type of suture has a tooth-like appearance?
What condition leads to increased intracranial pressure due to excessive cerebrospinal fluid?
What condition leads to increased intracranial pressure due to excessive cerebrospinal fluid?
Which sutural classification is characterized by articulating surfaces that are smooth?
Which sutural classification is characterized by articulating surfaces that are smooth?
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What are Wormian or sutural bones?
What are Wormian or sutural bones?
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What is the primary function of the sphenoid bone?
What is the primary function of the sphenoid bone?
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Which bones articulate to form the sagittal suture?
Which bones articulate to form the sagittal suture?
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Which of the following bones does NOT form part of the facial cranium?
Which of the following bones does NOT form part of the facial cranium?
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What is the function of the ethmoid bone?
What is the function of the ethmoid bone?
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How many paired bones are there in the facial cranium?
How many paired bones are there in the facial cranium?
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Which bone is incorrectly paired with its description?
Which bone is incorrectly paired with its description?
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Which type of bone is the maxilla classified as?
Which type of bone is the maxilla classified as?
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What structure is formed by the articulation of the frontal bone with the nasal bones?
What structure is formed by the articulation of the frontal bone with the nasal bones?
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What shape is the skull observed to be?
What shape is the skull observed to be?
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What is the primary function of the foramina in the skull?
What is the primary function of the foramina in the skull?
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Which of the following describes the layers of the skull bones?
Which of the following describes the layers of the skull bones?
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What bone is commonly referred to as the cheek bone?
What bone is commonly referred to as the cheek bone?
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What does the term 'calvarium' refer to?
What does the term 'calvarium' refer to?
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How many unpaired bones are present in the cerebral or cranial bones of the skull?
How many unpaired bones are present in the cerebral or cranial bones of the skull?
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Which of the following best describes the function of the palatine bones?
Which of the following best describes the function of the palatine bones?
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What portions of the cranium are formed by the occipital bone?
What portions of the cranium are formed by the occipital bone?
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What role does the inferior nasal conchae serve?
What role does the inferior nasal conchae serve?
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Which structure does the mandible NOT form part of?
Which structure does the mandible NOT form part of?
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Which cavities are separated by the bony nasal septum?
Which cavities are separated by the bony nasal septum?
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What is the primary significance of fontanels in newborns?
What is the primary significance of fontanels in newborns?
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What type of skull joints are the bones united by?
What type of skull joints are the bones united by?
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When does the anterior fontanel typically close completely?
When does the anterior fontanel typically close completely?
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Which fontanel is located at the triangular gap between the occipital and parietal bones?
Which fontanel is located at the triangular gap between the occipital and parietal bones?
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What happens to the fontanels as a sign of bone ossification?
What happens to the fontanels as a sign of bone ossification?
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Study Notes
The Skull
- The skull encompasses the entire skeletal framework of the head and face, including the mandible.
- The cranium refers to the skull, excluding the mandible.
- The calvarium pertains to the skull after the facial bones have been removed.
- The skull comprises numerous irregular and flattened bones joined by immobile sutures, except for the mandible.
Skull Characteristics
- Viewed from the side, the skull appears slightly flattened.
- The skull's upper surface displays a smooth texture.
- From below, the skull's surface exhibits a very uneven appearance.
- Structurally, the skull is oval in shape, wider at the back than the front.
- It's composed of irregular, flat bones.
- The base of the skull is notable for its significant thickness and strength.
- The skull has numerous openings, called foramina. These allow the passage of the spinal cord, cranial nerves, and blood vessels.
- The skull is composed of two layers of compact bones:
- The outer layer (outer table) is thick and tough.
- The inner layer (inner table), is thinner and more brittle.
- A layer of spongy bone, called the diploë, is between these two layers.
Definitions of Terms
- Skull: The entire skeleton of the head and face, encompassing the mandible.
- Cranium: The skull, devoid of the mandible.
- Calvarium: The skull after the facial bones have been removed.
The Different Views of the Skull
- This section discusses variations in observing the skull anatomically, such as views from above (Norma Verticalis), from behind(Norma Occipitalis), and from the front (Norma Frontalis), from the side (Norma Lateralis) and from the base (Norma Basalis), both internally (Norma Basalis Interna) and externally (Norma Basalis Externa. ).
Cavities of the Skull
- The skull encloses several cavities:
- Cranial Cavity: Houses the brain.
- Orbital Cavities: Contain the eyeballs, lacrimal gland, muscles and nerves for eye movement and the blood supply for the eyes.
- Nasal Cavities: Separated by a bony nasal septum.
Divisions of the Skull Bones
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Cranial Bones (8): These constitute the braincase.
- Unpaired: Occipital, frontal, sphenoid, ethmoid.
- Paired: Parietal, temporal.
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Facial Bones (14): Form the midface and surrounding structures.
- Paired: Nasal, lacrimal, maxilla, zygomatic, palatine, inferior nasal conchae.
- Unpaired: Vomer, mandible.
Specific Bones and their Functions
- Occipital Bone: Forms the posterior and inferior portions of the cranium. Articular with the parietal bones to form the lambdoid suture.
- Frontal Bone: Forms the forehead and superior parts of the eye sockets.
- Sphenoid Bone: Forms part of the floor of the cranium and acts as a bridge between cranial and facial bones, supporting the sides of the skull.
- Ethmoid Bone: A constituent part of the cranial floor; it's important in composing the medial surface of the eye socket and also forms the roof and sides of the nasal cavity.
- Parietal Bones: Form the roof and upper walls of the cranium. They are situated posterior to the frontal bone and anterior to the occipital bone, articulating to form the sagittal suture.
- Temporal Bones: Located beneath the parietal bones, contributing to the cranium's sides and base. Involved in forming the squamosal suture with the parietal bone.
- Nasal Bones: Form the bridge of the nose and lie between the orbits. Articulate with frontal and maxillary bones.
- Lacrimal Bones: Located within the medial walls of the eye sockets (orbits). Articulate with frontal, ethmoid, and maxillary bones.
- Maxillary Bones: Contribute to the midface. They incorporate the maxillary sinuses and the upper teeth, articulate with almost all other facial bones except the mandible.
- Zygomatic Bones: Part of the facial structure, known as the cheek bones or malar bones. They articulate with the frontal and maxillary bones to form the lateral eye socket wall.
- Palatine Bones: On the posterior section of the hard palate; they communicate with the orbits and create the palate floor.
- Inferior Nasal Conchae: Project from the lateral nasal cavity walls.
- Vomer: A flat bone forming the lower part of the bony nasal septum.
- Mandible: The lower jawbone.
Fontanels
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Membrane-filled spaces between the bones of the fetal skull, crucial for brain growth and allowing the skull to compress during childbirth.
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Closing of fontanels signals complete bone ossification.
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Non-closure indicates incomplete bone development.
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Anterior Fontanel: Located between the frontal and parietal bones. The largest fontanel, it usually closes by age 2.
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Posterior Fontanel: Small, triangular-shaped, situated between the occipital and parietal bones. It typically closes within 2 months of birth.
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Sagittal Fontanel: Located on the sagittal suture. It's smaller than the others, and it may close before birth or by the early months of life.
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Anterolateral (Sphenoidal) Fontanel: Located between parietal, frontal, and sphenoid bones. It closes within 3 months of birth.
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Posterolateral (Mastoidal) Fontanel: Located at the junction of the parietal and occipital bones. It closes within the first year.
Sutures
- Joints between cranial bones.
- Coronal Suture: Unites the frontal and parietal bones.
- Sagittal Suture: Joins the two parietal bones.
- Lambdoid Suture: Connects the parietal and occipital bones.
Classification of Sutures
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TRUE (Vera): Smooth articulating surfaces. Ex: sagittal, coronal sutures. Subcategories:
- DENTATE: Tooth-like edges.
- SERRATE: Saw-toothed edges.
- SCHAMOID: Scale-like.
- FALSE (Notha): Rough articulating surfaces. Ex: Squamosal or harmonia.
Wormian Bones
- Small, extra bones found within the cranial sutures.
- Pneumatic bones contain air spaces.
Skull Anomalies
- Microcephaly: Small skull size due to early fontanel closure.
- Macrocephaly: Large skull size due to late fontanel closure.
- Hydrocephalus: Excessive cerebrospinal fluid causing increased intracranial pressure and potentially open fontanels
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Description
Test your knowledge on cranial anatomy with questions focusing on conditions related to skull development and sutural classifications. Explore topics such as fontanel closure, intracranial pressure, and special types of bones found within cranial sutures.
