Skull Anatomy Notes #1, Lab Exam #2 2022 Update PDF

# The Skull ## The Maxillae - Two bones fused together to form the upper jawbone - Joined at the maxillae, all facial bones, but the mandible - **Alveolar margin** contains the inferior sockets for teeth - **Palatine processes** form the anterior hard palate - **Infraorbital foramen** is an opening...

# The Skull ## The Maxillae - Two bones fused together to form the upper jawbone - Joined at the maxillae, all facial bones, but the mandible - **Alveolar margin** contains the inferior sockets for teeth - **Palatine processes** form the anterior hard palate - **Infraorbital foramen** is an opening for infraorbital nerves and blood vessels of the nasal region - **Incisive fossa** transmits the nasopalatine arteries and blood vessels ## The Lacrimal bones - Form part of the medial lateral wall of the eye socket - Between the maxillae and the ethmoid - Pierced by lacrimal fossa, which are the passageways for tears ## The Palatine bones - Form the posterior hard palate and part of the orbit ## The Zygomatic bones - Lateral to the maxillae - Part of the cheekbones and the lateral orbit ## The Nasal bones - Small rectangular bones that form the bridge of the nose ## The Vomer - Blade-shaped bone in the medial plane which forms the posterior and inferior nasal septum ## The Hyoid bone - Located in the throat above the larynx - Point of attachment for neck and tongue muscles - Not articulated to any other bone ## Paranasal sinuses - The maxillary, sphenoid, ethmoid, and frontal bones contain sinuses - **Maxillary sinus** is the largest - May be used for resonance chambers and also lighten the facial bones ## Sinusitis - Inflammation of the sinuses resulting from an allergy or a bacterial infection - Causes a blockage of passageways with mucus - Symptoms are a sinus headache # The Vertebral Column - Runs from the skull to the pelvis, and forms the major axial support - Protects the spinal cord and allows nerves to issue from the cord via openings between the vertebras - Consists of 24 bones, the vertebrae, and the Sacrum and the Coccyx ## The Cervical vertebrae - 7 bones of the neck ## The Thoracic vertebrae - 12 bones of the upper back ## The Lumbar vetebrae - 5 bones of the lower back ## Intervertebral discs - Cushion and absorb shock - Two parts: an inner nucleus pulposus, which is a central gelatinous mass, surrounded by an outer ring of collagen fibers, the annulus fibrosus ## Ruptured discs - Occur when the nucleus pulposus herniates through the annulus fibrosus compressing spinal nerves ## The s-shape of the spine - Prevents shock and allows for flexibilty - **Primary Curvature** (Thoracic and Sacral) of the spine is present at birth - **Secondary Curvature** (Cervical and Lumbar) is seen ## Abnormalities of spinal curvature - **Scoliosis:** abnormal/ excessive lateral curvature of the spine - **Kyphosis:** abnormal/ excessive dorsal curvature of the spine - **Lordosis:** abnormal/ excessive anterior curvature of the spine ## Structure of the Vertebrae - **Body or Centrum:** the rounded central portion that faces anteriorly - **Vertebral arch:** consists of the Pedicles (connects the body to the laminae), Laminae (connects the spinous and transverse processes) and a Spinous process. - **Vertebral foramen:** an opening between the arch and the body, the space that allows the spinal cord to pass. - **Transverse process:** the lateral projection of the arch. - **Spinous process:** the medial/ posterior projection of the arch. - **Superior and Inferior articular processes:** paired projections lateral to the vertebral foramen, that articulates between vertebrae. The superior process faces towards the spinous process and the inferior away. - **Intervetebral Foramina:** spaces in the pedicels that allow for spinal nerves to leave between the vertebra. ## Cervical Vertebae - **C1 and C2** have special functions and names. - **The Atlas, C1**, has no body, and the lateral processes have large depressions that receive the occipital condyles of the skull. - **The Axis, C2**, acts as a pivot for rotation of the atlas. The odontoid process/dens forms the pivot. ## The Vertebral prominence - **C7** which is visible through the skin. ## Costal demifacets - Found in the body of thoracic vertebrae and articulate with the ribs. ## Positioning of the superior and inferior articulating processes - Reduces mobility. ## The spinal cord - Ends at L2, but the outer coverings (meninges) continue and are filled with spinal fluid. ## Lumbar puncture/spinal tap - Done between L3-L4 and L4-L5, as well as Saddle Block (anesthesia for child birth) to avoid damaging the spinal cord. # Sacrum - Five fused vertebrae, it articulates with L5. - Inferior to the sacrum is the coccyx. - **Medial Sacral crest:** made up of fused spinous processes. - **Alae (wings):** fused transverse processes which articulate with the pelvic girdle. - **Sacral foramina:** allow blood vessels and nerves to pass at ridges of fusion. - **Sacral canal:** holds the rest of the spinal coverings which enter the coccyx at the Sacral Hiatus. - **Sacral promontory:** the anti-border of S1, is a landmark for obstetricians. # The Coccyx - Fusion of 3 to 5 small vertebrae, vestige of a tail. # The Bony Thorax - Consists of the Ribs, the Sternum, and the thoracic Vertebrae. - Also known as the thoracic cage. ## Sternum or breastbone - Flatbone, which is a fusion of three bones - **Manubrium:** triangular bone that articulates with the clavicles. - **Body:** bulk of the sternum. - **Xiphoid process:** most inferior bone, which if projected dorsally when struck can cause trama to the heart or liver. ## Four landmarks that can be seen are: - **Jugular notch:** the concave upper border of the manubrium. - **The Sternal angle:** where the manubrium and the body meet. - **Xiphisternal joint:** where the body and the xiphoid process meet. - **Clavicular Notches:** which are sites of articulation with Clavicles. ## Ribs - Twelve pair of ribs that form the walls of the thoracic cage. - **The first seven pairs (1-7):** attached directly to the sternum and the vertebral column and are called Vertebrosternal. - **Pairs 8-10:** called Vertebrochondral or False ribs and are attached indirectly to the sternum by hyaline cartilage. - **Pairs 11 and 12:** not attached to the sternum and are called Floating or Vertebral ribs. # The Fetal Skeleton - **Fontanels:** indentations between bones of the fetal skull are called fontanels, which are fibrous membranes. These ossify by the 20-22 months after birth. They allow for compression during birth, and allow for growth of the brain. - **There are four fontanels;:** the Anterior, the Posterior, the Sphenoid, and the Mastoid. ## Skull depressions and projections summary # Frontal Bone - **Supraorbital foramens (notch):** openings above each orbit which allow blood vessels and nerves to pass. - **Coronal Suture:** the point of articulation of the Frontal and Parietal Bones. # Parietal Bones - **Sagittal Suture:** point of articulation of Parietal bones # Temporal Bone - **Squamous Suture:** the point of articulation of the temporal and parietal bones. - **Zygomatic process:** forms the cheekbone - **Stylomastoid Foramen:** passage of CN VII (7) - **Jugular Foramen:** passage of Internal Jugular Vein and CN IX, X, XI (9, 10, 11) - **Carotid Canal:** passage of internal carotid Artery - **Mandibular fossa:** a rounded depression that is the site of articulation with the mandible - **The Styloid process:** an attachment site for muscles and ligaments of the neck. - **The Mastoid process:** an attachment site for muscles. - **External Acoustic Canal:** passage for sounds to middle ear - **Internal Acoustic Canal:** passage of CN VII and VIII (7, 8) - **Formen Lacerum:** passage of Internal Carotid Artery # Occipital Bone - **Lambdoid Suture:** point of articulation of Occipital and Parietal Bones - **Foramen Magnum:** passage of Spinal Cord - **Hypoglossal Canal:** passage of CN XII (12) - **Occipital Condyles:** point of articulation of Occipital bone and C1, the Atlas # Sphenoid (Cranial Keystone) - **Greater Wings:** part of eye orbit/socket - **Superior Orbital Fissure:** passage of CN III, IV, V, VI (3, 4, 5, 6) - **Inferior Orbital Fissure:** passage of Infraorbital blood vessels and CNV (5) - **Hypophyseal Fossa:** holds Pituitary Gland - **Optic Canal:** passage of CN II (2), Optic Nerve - **Foramen Rotundum and Ovale:** passage of CN V (5) - **Foramen Spinosum:** passage of Middle Meningeal Artery # Ethmoid - **Lateral Masses:** of part of eye orbit/ socket - **Crista Gali:** attachment of Dura mater to Skull - **Cribriform Plates:** hold Olfactory Foramina which are passage for CN I (1), Olfactory Nerve - **Horizontal plate:** the Crista Gali and the two Cribriform plates - **Perpendicular Plate:** forms the superior nasal septum - **Superior and Inferior Nasal Conchae:** are turbinates # Mandible - **Mandibular Body:** forms the chin - **Mandibular Condyle:** articulates with the mandibular fossa - **Conoid Process:** site of muscle attachment - **Mental Foramen:** passage of Mental blood vessels - **Alveolar Margin:** site of inferior teeth sockets - **Mandibular Symphysis:** site of mandibular fusion - **Mandibular Foramen:** passage of CN V (5) # Maxillae (Facial keystone) - **Alveolar Margin:** site of superior teeth sockets - **Palatine Processes:** anterior portion of hard palate - **Infraorbital Foramen:** passage of Infraorbital blood vessels - **Incisive Fossa:** passage of Nasopalatine Artery and blood vessel # Lacrimal Bone - **Lacrimal Fossa:** passage for tears, also part of eye orbit/ socket # Palatine Bone - Forms posterior portion of hard palate # Zygomatic Bone - Forms cheeks and part of eye orbit/ socket # Nasal Bone - Forms bridge of nose and part of eye orbit/ socket # Hyoid - Attachment site of neck and tongue muscles