Skull and Cranial Structures Overview

In a fetal skull, the fibrous membranes connecting cranial bones, allowing for growth and molding during birth.

The middle cranial fossa is superior to the middle ear, the jugular bulb is inferior, the internal carotid artery and Eustachian tube are anterior, the mastoid air cells are posterior, the tympanic membrane is lateral, and the oval and round windows are medial.

The roof is formed by the frontal bone, the floor by the maxilla and zygomatic bone, the medial wall by the ethmoid and lacrimal bone, and the lateral wall by the zygomatic bone and greater wing of the sphenoid.

The vagus nerve innervates the palatoglossus, levator veli palatini, pharyngeal constrictors, intrinsic laryngeal muscles (except cricothyroid), and palatopharyngeus.

The cricothyroid muscle tenses the vocal cords, increasing their pitch.

Cortical interneurons modulate the excitatory and inhibitory signals within the cerebral cortex, influencing the strength and timing of neuronal activity.

It is a ligament located between the epiglottis and arytenoid cartilage. Its upper boundary forms the aryepiglottic fold, which acts like a valve for the larynx, and its lower boundary forms the vestibular fold.

The external jugular vein is superficial (outer layer) to the sternocleidomastoid muscle.

The alar space is a potential space located between the prevertebral fascia and alar fascia. It extends cranially from the skull base to the T2 vertebrae.

The external branch of the superior laryngeal nerve lies near the superior thyroid artery.

The anterior part of the nasal septum where the Kiesselbach's plexus is located.

The parotid gland drains via Stensen's duct, which opens near the upper second molar. The submandibular gland drains through Wharton's duct into the sublingual papilla, and the sublingual gland drains through the ducts of Rivinus in the floor of the mouth.

The masseter, medial pterygoid, and temporalis muscles are all involved in closing the mouth.

The posterior belly of the digastric muscle is innervated by the facial nerve (CN VII).

The ciliary muscle contracts, relaxing the zonular fibers, causing the lens to thicken for near vision.

Damage to the optic nerve results in complete blindness in the affected eye. This is due to the optic nerve being the sole pathway for visual information from the eye to the brain.

The temporal bone has four parts: squamous, tympanic, mastoid, and petrous. It houses important structures of the middle and inner ear.

Foramina are openings in the skull that allow for passage of nerves, blood vessels, and other structures. For example, the foramen ovale in the sphenoid bone allows the trigeminal nerve (CN V) to pass through.

The thyroid gland is covered by pretracheal fascia, which is a layer of connective tissue in the neck.

The infraorbital nerve (CN Vb) provides sensation to the lower eyelid.

The chorda tympani nerve carries taste from the anterior 2/3 of the tongue and parasympathetic fibers to the submandibular and sublingual salivary glands.

The fetal skull has soft spots called fontanelles, its sutures are not yet fused, and its face is smaller compared to the cranium.

The middle ear is surrounded by key structures: superiorly by the middle cranial fossa, inferiorly by the jugular bulb, anteriorly by the internal carotid artery and Eustachian tube, posteriorly by the mastoid air cells, laterally by the tympanic membrane, and medially by the oval and round windows.

The orbit's roof is formed by the frontal bone, its floor by the maxilla and zygomatic bone, its medial wall by the ethmoid and lacrimal bone, and its lateral wall by the zygomatic bone and the greater wing of the sphenoid bone.

The vagus nerve controls several important muscles: the palatoglossus, levator veli palatini, pharyngeal constrictors, intrinsic laryngeal muscles (except the cricothyroid), and the palatopharyngeus.

The cricothyroid muscle tenses the vocal cords, increasing their pitch.

Cortical interneurons act like mediators, balancing the excitatory and inhibitory signals within the cerebral cortex.

The quadrangular ligament connects the epiglottis and arytenoid cartilage. Its upper boundary forms the aryepiglottic fold, acting like a valve for the larynx, and its lower boundary forms the vestibular fold.

The external jugular vein runs superficially to the sternocleidomastoid muscle, making it visible on the surface of the neck.

The alar space is a potential space between the prevertebral fascia and alar fascia, extending from the skull base to the T2 vertebrae. It's a potential space, meaning it's not always a space that is filled.

The external branch of the superior laryngeal nerve runs close to the superior thyroid artery within the neck.

Located in the anterior portion of the nasal septum, it is a convergence point for several blood vessels and a common site for nosebleeds.

The parotid gland's duct opens near the upper second molar, while the submandibular gland's duct opens near the tongue's base. The sublingual gland has multiple smaller ducts opening onto the floor of the mouth.

The masseter, medial pterygoid, and temporalis muscles work together to close the jaw, creating the chewing force.

The facial nerve controls the movement of the posterior belly of the digastric muscle, which helps depress the mandible.

Contraction of the ciliary muscle relaxes the zonular fibers, allowing the lens to thicken for near vision. This process helps focus objects close to the eye.

Damage to the optic nerve completely disrupts the flow of visual information from the eye to the brain, causing complete blindness in that eye.

The temporal bone has four parts: squamous, tympanic, mastoid, and petrous. It houses structures like the middle and inner ear, which are essential for hearing and balance.

Foramina are openings in the skull, like windows for nerves and blood vessels. For example, the foramen ovale allows the trigeminal nerve, important for facial sensation, to pass through.

The thyroid gland is enclosed by pretracheal fascia, a layer of connective tissue that helps support and organize the neck's structures.

The infraorbital nerve, a branch of the trigeminal nerve, carries sensory information from the lower eyelid, cheek, and upper lip.