Skull and Axial Skeleton

Transcription

1 Published on Second Faculty of Medicine, Charles University ( ) Skull and Axial Skeleton Description of the test The examination of the skull skeleton is in oral format. It consists of five parts; details of each part are listed below. Students will be examined on the skull. The individual bones of the skull will not be examined (apart from the mandible). Students are not required to draw any required schemes during the examination, although they may draw schemes of the more complex topographical regions to aid their discussions on these topics (e.g. tympanic cavity). It is necessary for each student to know the Latin and English name for each of the cranial nerves, their number and how each nerve or its branches pass through the skull. Additionally, students are required to know the course of the facial nerve through the Fallopian canal. When a branch of a cranial nerve passes through a cranial foramen it is required to know which cranial nerve it is a branch of. Students are not required to know the nuclei, parts and functions of cranial nerves, nor branches of cranial nerves that do not pass through the skull. Part 1 Topographical spaces of the skull Each student will be presented with one of the following topographical spaces listed below. They will have to correctly locate the space on the skull and describe its borders and contents (e.g. the orbit contains the eye bulb, the optic nerve, extra-ocular muscles, vessels and nerves, and the lacrimal gland ). The student is required to mention whether a cranial nerve or important vessel passes through their given topographical region. List of topographical regions: 1. Orbita 2. Cavitas nasi

2 3. Cavitas tympani 4. Fossa infratemporalis 5. Fossa pterygopalatina 6. Fossae cranii Part 2 Passages and foramina of the skull Each student will be required to find the passage of several structures through the skull (refer to the table Passages through the skull and their content in the textbook Memorix Anatomy pages to find the complete list of structures that can be tested). Questions may be asked in the following format: What is this structure? and Show me how the maxillary nerve passes through the skull. Correct answers to these questions are: This is foramen rotundum. The maxillary nerve passes through this foramen from the middle cranial fossa to the reach the pterygopalatine fossa and it passes through foramen rotundum, which is here (student shows the foramen on the skull), to reach the pterygopalatine fossa from the middle cranial fossa, respectively. Part 3 Joints and other structures of the skull Each student is required to answer several miscellaneous questions chosen by the examiner. Questions may have a similar format as Part 2 (e.g. Question: What is this structure? Answer: Sulcus of the middle meningeal artery. Question: Show me the sulcus of the middle meningeal artery. Answer: It is here (student shows the structure on the skull). The student may also be required to recognise or show and describe several structures concerning joints of the skull, anthropometric points and the sex differences of the skull. The student is not required to know the insertions and origins of the mimetic muscles or the deep neck and back muscles. However, students are required to know the muscles attaching to the mastoid process, styloid process and mandible, etc. Part4 Clinical notes and other interesting notes The examiner may ask several clinical questions or questions concerning other

3 interesting points especially from the list below. Part 5 Radiological images The student may be asked questions on radiolographs of the bone and joints of the axial skeleton. Clinical notes The pterion is a craniometric point at the point where the greater wing of the sphenoid bone, the parietal bone and the frontal bone meet. It is the weakest point of the skull. The middle meningeal artery is located underneath it on the internal surface of the skull. Trauma to this region may result in bleeding of the middle meningeal artery, which results in an epidural hematoma. The pituitary gland can be accessed via the sphenoidal sinus. This is known as the transnasal transsphenoidal approach and can be used to remove pituitary tumours. The anterior fontanelle can be used to help orientate the position of the foetus's head during delivery. The anterior fontanelle can be used to assess the state of hydration and intracranial pressure of new-borns. Increased pressure within the skull (intracranial hypertension) can lead to bulging of the anterior fontanelle. Intracranial hypertension in new-borns can result from hydrocephalus. Venepuncture can be performed through the anterior fontanelle to get a sample of dural venous blood. Ultrasound imaging can be performed through the anterior fontanelle to visualize the brain, otherwise impossible as the bones of the skull do not allow the sound waves to pass through into the parenchyma of the brain. When the paranasal sinuses are inflamed (a conditions known as sinusitis),

4 percussion over the sinus becomes painful. The inflammation may erode the thin bone and enter the cranial cavity or the orbit. An X-ray may show opacity of the sinus. Inflammation of the frontal sinus (frontal sinusitis) causes palpation over the area innervated by the ophthalmic nerve (N. V1) to become painful. Inflammation of the maxillary sinus (maxillary sinusitis) causes palpation over the area innervated by the maxillary nerve (N. V2) to become painful. Inflammation of the ethmoidal air cells causes palpation over the nasal root to become painful. The maxillary sinus is closely related to the roots of the upper teeth, especially the canine, which has the longest root. Infection may spread directly from the middle ear cavity, nasal cavity or paranasal sinuses to the neurocranium causing meningitis. Alternatively, infection may reach the neurocranium from a distal source via the blood or may be directly implanted in the neurocranium following head trauma. Blow-out fractures are fractures of the walls of the orbit caused by direct hits to the eyeball and are typically caused by a ball or a fist. The medial and inferior walls are the weakest parts of the orbit and are most commonly fractured by such an injury. The extraocular muscles may become trapped by the fracture fragments causing diplopia (double vision) and impaired eye movements. A pathological communication may be formed between the orbit and the adjacent paranasal sinuses. This can lead to orbital emphysema (air in the orbit). The margin of the orbit is not affected, disguising the severity of the condition. Leakage of cerebrospinal fluid from the nose is called nasal liquorrhoea. A fracture of the roof of the nasal cavity can cause cerebrospinal fluid to leak into and out of the nose, which the patient may recognise as a runny nose. This condition is associated with a high risk of central nervous system infections. Kiseelbach's plexus is located on the nasal septum. It is containing a high

5 density of capillaries and is the most common source of epistaxis (nasal bleeding). The maxillary artery can be ligated in the pterygopalatine fossa and can be accessed through the maxillary sinus. This method is known as transantral maxillary artery ligation and is indicated in intractable epistaxis (nasal bleeding). An inferior alveolar nerve block is performed by injecting a local anaesthetic near the mandibular foramen in the pterygomandibular space. Otitis media / mesotitis is the most common disease of the middle ear. It is a septic inflammation that occurs most commonly in infants and toddlers. It presents with a painful ear, headache, and even a perforated eardrum. Other interesting points The bones of the skull develop from mesenchymal tissue surrounding the developing brain. According to their developmental origin and type of ossification, the bones of the skull are divided into three main groups: the chondrocranium, desmocranium and viscerocranium. The chondrocranium includes the bones of the skull that develop by endochondral ossification. These bone are phylogenetically the oldest part of the skull. The desmocranium includes the bones of the cranial vault that develop by intramembranous ossification. The viscerocranium includes the bones that make up the facial skeleton. It is phylogenetically the youngest part of the skull. The facial bones develop from mesenchyme of the pharyngeal arches by intramembranous ossification. The exceptions are the auditory ossicles and the hyoid bone, which develop by endochondral ossification. The pyramid (pyramis) is an obsolete term for the petrous part of the temporal

6 bone. Lamina papyracea ossis ethmoidalis is an obsolete term for the orbital plate of the ethmoid bone. As the name implies, this part of the ethmoid bone is very thin and liable to fracture. Small and independent centres of ossification may occur in certain fontanelles. This leads to formation of some small accessory skull bones. Such bones include the bregmatic bone (os bregmaticum) in the anterior fontanelle and the epipteric bone (os epiptericum) in the posterior fontanelle. The semilunar hiatus is the opening of the maxillary sinus, frontal sinus and anterior and middle ethmoidal air cells into the middle nasal meatus. The middle ear cavity consists of tympanic cavity, mastoid antrum, mastoid cells, tympanic cells and the auditory tube. All information required for the oral examination of the skull and axial skeleton, including clinical notes and other interesting points can be found in the textbook Memorix Anatomy in the chapters Bones, Joints and Topography. Some structures and spaces are described in the chapters Digestive System (e.g. insertion of the pharynx on the base of the skull), Respiratory System (e.g. the nasal cavity and paranasal sinuses), Peripheral nervous system (e.g. branching patterns and pathways of the cranial nerves) and Skin and Sense Organs (e.g. middle ear cavity). Published: / Last update: / Responsible person: MUDr. Radovan Hudák Source URL (retrieved on :38):