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Questions and Answers
What is the total number of bones in an adult human's axial skeleton?
Which bone does not articulate with any other bone?
Which of the following bones is NOT part of the axial skeleton?
Which mnemonic represents the cranial bones?
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What function do sinuses provide to the skull?
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What feature characterizes the sella turcica?
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Which type of joint allows for spinal movement and is characterized as a symphysis joint?
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What is the purpose of the fontanelles present in an infant's skull?
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Which of the following muscles is involved in mastication?
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What is the primary anatomical role of the appendicular musculature?
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Which nerve is responsible for the innervation of the muscles of mastication?
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What condition is characterized by paralysis or weakness of the muscles on one side of the face?
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Which muscle is primarily responsible for moving the larynx up during swallowing?
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What is the anatomical term for the chewing process?
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Which of the following muscles depresses the larynx?
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What is the origin of the sternocleidomastoid muscle?
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Study Notes
Introduction to Axial Skeleton
- The axial skeleton is the central axis of the body which protects and stabilizes internal organs
- An adult has 206 bones total, 80 of which are part of the axial skeleton
- The axial skeleton consists of:
- skull bones
- auditory ossicles (ear)
- hyoid
- vertebral column
- thoracic cage (ribs)
The Skull Bones
- The facial bones are:
- Mandible
- Maxilla
- Palatine
- Nasal
- Lacrimal
- Zygomatic
- Inferior Nasal Conchae
- Vomer
- The cranial bones are:
- Parietal
- Ethmoid
- Sphenoid
- Temporal
- Occipital
- Frontal
Bones of the Medial Wall of the Orbit
- The bones of the orbital wall are:
- Maxilla
- Lacrimal
- Ethmoid
- Sphenoid
Bones of the Nasal Septum
- The bones of the nasal septum are:
- Maxilla
- Vomer
- Frontal
- Nasal
- Sphenoid
- Palatine
Sphenoid Bone
- The sphenoid bone is located at the base of the cranium and acts as a bridge between the cranial and facial bones
- It supports the frontal lobe of the brain
- The sphenoid bone houses the pituitary gland within a depression called the sella turcica
Ethmoid Bone
- The ethmoid bone is part of the orbital wall, the floor of the cranium and the roof of the nasal cavity.
- The crista galli projects superiorly and serves as an attachment point for the falx cerebri which is a fold in the meningeal membranes separating the cerebral hemispheres.
Sinuses
- Sinuses are cavities within the skull that lighten the skull bones, produce mucus, and resonate during sound production
Hyoid Bone
- The hyoid bone is unique because it does not articulate with any other bone and sits inferior to the skull.
Infant Skull
- An infant skull has 4 fontanelles (fibrous regions) which allow for cranial distortion during childbirth without harming the head
- Fontanelles also enable rapid brain growth and become fused suture joints at about age 5
Joints of the Axial Skeleton
- Suture joints are synarthrosis (immovable) joints which are found in the skull.
- Temporomandibular joints are synovial, hinge joints that permit gliding motion.
- Intervertebral joints are diarthrosis (synovial) joints.
- Sternocostal & Costochondral joints are diarthrosis (synovial) joints.
- Vertebrocostal joints are diarthrosis (synovial) joints.
- Sacroiliac and Sacrococcygeal joints are diarthrosis (synovial) joints.
Intervertebral Discs
- Intervertebral discs are composed of fibrous cartilage and are symphysis joints located between vertebral bodies.
- They allow for some spinal movement (angular and linear).
- Intervertebral discs act as shock absorbers/cushions and transmit load.
- A "disc bulge" is a slight protrusion of the disc, while a "herniation" is a more significant protrusion that can cause pain or nerve damage.
Axial Musculature
- Position the head and vertebral column
- Move the rib cage for breathing
Appendicular Musculature
- Stabilize or move the arms and legs
Muscles of the Head & Neck
- These muscles can be grouped as:
- Muscles of facial expression
- Muscles of mastication
- Muscles of the anterior neck
Bell's Palsy
- Bell's palsy is paralysis or weakness of the muscles on one side of the face caused by damage to the facial nerve
- It causes the affected side of the face to droop.
Mastication
- Mastication is the anatomical term for chewing.
- It involves the elevation, depression, protraction, retraction, and lateral movements of the mandible
- Movement during mastication occurs at the temporomandibular joint.
Muscles of Mastication
- The muscles of mastication are:
- Masseter
- Temporalis
- Medial and lateral Pterygoids
- Muscles of mastication are innervated by the mandibular branch of the Trigeminal Nerve (CN V).
Role of Anterior Neck Muscles
- Help with speech production: Extrinsic muscles position the larynx and affect the tone of speech.
- Help with swallowing: Raising the hyoid bone and larynx depresses the epiglottis. Depressing the hyoid and larynx re-opens the airway and pushes food into the esophagus.
Anterior Neck Muscles
- Muscles elevating larynx:
- Geniohyoid
- Mylohyoid
- Digastric
- Stylohyoid
- Muscles depressing the larynx:
- Omohyoid
- Sternohyoid
- Sternothyroid
- Muscles positioning the head
- Sternocleidomastoid
Innervation of Anterior Neck Muscles
- Digastric: Trigeminal nerve, mandibular branch.
- Geniohyoid: Cervical nerve C1.
- Mylohyoid: Trigeminal nerve, mandibular branch.
- Omohyoid: Cervical spinal nerves.
- Sternohyoid: Cervical spinal nerves.
- Sternocleidomastoid: Accessory nerve and cervical spinal nerves.
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Description
This quiz covers the key components of the axial skeleton, which serves as the central axis of the human body. You'll explore the various bones that make up the axial skeleton, including the skull, vertebrae, and thoracic cage, as well as their specific functions. Test your knowledge on the structure and classifications of these crucial bones.
