The Skull

Summary

Highlights

• Dr. Morton breaks down the skull bone names, many of which come from Latin origins! 📚
• Discover the sutures of the skull that act like stitches binding different parts together! 🧵
• Learn about the cranial fossae, the amazing stair-like depressions of our skull! 🛠️
• Unveil the pathways of cranial nerves and their roles in our senses and movements! 👃👂
• Get insights into dangerous hotspots like the pterion, where an injury can cause critical bleeding! ⚠️
• Explore the intricate journey of cranial nerves through canals and foramina! 🚧
• Enjoy a concise and engaging anatomy lesson from the Noted Anatomist! 🎓

Key Takeaways

• The skull consists of several bones named after their Latin roots, such as frontal for forehead and parietal for wall, reflecting their function or location. 🇱🇦
• Sutures in the skull connect bones together like stitches and include the coronal, squamous, lambdoid, and sagittal sutures. 🧶
• Cranial fossae are the three stair-like depressions that hold the brain's parts, with the anterior, middle, and posterior fossae separated by key structures like the sphenoid bone and petrous part of the temporal bone. 🏰
• The skull structures have openings like the foramen and canals that allow for passage of nerves and blood vessels, crucial for brain and sensory functions. 🚪
• Areas like the pterion and foramen magnum have critical clinical significance due to their vital contents and exposure to injury. 🚑

Overview

Chapters

• 00:00 - 00:30: Introduction to the Skull Anatomy In this chapter, Dr. Morton provides an overview of skull anatomy, highlighting the primary bones and sutures. The discussion begins with the frontal bone, known in Latin as 'frontal' due to its location at the forehead. It proceeds to describe the zygomatic bone, which forms the cheek, and the maxilla. The chapter aims to explore the cranial fossae and elucidate the openings for cranial nerves and vessels.
• 00:30 - 01:00: Frontal, Zygomatic, Maxilla, Parietal, and Temporal Bones The chapter discusses various bones of the skull, specifically the frontal, zygomatic, maxilla, parietal, and temporal bones. The maxilla, or upper jaw, is highlighted, noting its Latin origin related to the jaw. The parietal bone is described with reference to its function as a 'wall,' indicated by its Latin root seen in terms like parietal pleura and other related terms. The temporal bone is explained in terms of its association with the passage of time, as it is located near the ear where gray hair, a sign of aging, tends to appear.
• 01:00 - 01:30: Petrous Part of Temporal Bone and External Acoustic Meatus The chapter discusses the petrous part of the temporal bone, which is located on the lateral side and is often hidden within the bone itself. The term 'Petrous' means rock, indicating its density, and it appears as a bright or white area in lateral x-rays. Identifying the petrous part helps in locating other structures. Additionally, the temporal bone also includes the external acoustic meatus.
• 01:30 - 02:00: Mandible and Occipital Bone The chapter titled 'Mandible and Occipital Bone' explains various bones of the skull. It starts with the external acoustic meatus, an opening that leads to the eardrum. Following this, the sphenoid bone is mentioned, which is wedge-shaped, present at the side of the skull, with a promise to elaborate more later. The chapter emphasizes the mandible, known for allowing jaw movement and chewing, derived from the Latin word for chew. It concludes with the occipital bone, highlighted in purple, which comes from the Latin term for the back of the skull.
• 02:00 - 03:00: Sutures of the Skull The chapter discusses sutures of the skull, explaining the term's Latin origin 'to bind, sew, or seam', likening it to a stitch. The focus is then on the coronal suture, which connects the parietal and frontal bones, and is situated in the coronal plane.
• 03:00 - 04:00: Cranial Fossae The chapter 'Cranial Fossae' describes the connections between different bones in the human skull. It details the parietal and temporal bones, connected by the squamous or squamosal suture. The lambdoid suture, named after the Greek alphabet symbol 'lambda' which it resembles, connects the parietal and occipital bones. Additionally, the sagittal suture is highlighted for its role in connecting the parietal bones from a superior view. The chapter provides both lateral and superior perspectives to explain the anatomical positioning and connections of these sutures.
• 04:00 - 05:00: Anterior Cranial Fossa The chapter discusses the anatomy of the anterior cranial fossa, focusing particularly on the bones and sutures that form this part of the skull. It highlights the sagittal suture, located in the sagittal plane, and the tairy on, a small suture connecting multiple bones: parietal, frontal, sphenoid, and temporal. An interesting note is provided on the etymology of the tairy on, linked to Hermes from Greek mythology, where wings were placed on his head and ankles. The discussion then moves on to explaining cranial fossae, which are three large depressions in the skull that house different parts of the brain.
• 05:00 - 06:00: Middle Cranial Fossa The middle cranial fossa is described in relation to the cranial cavity, starting with an overview of the structure from a sagittal section of the skull viewed laterally. The cranial cavity is divided into different regions, starting with the anterior cranial fossa, followed by a step down to the middle cranial fossa, and subsequently a step down to the posterior cranial fossa. The anterior and middle cranial fossae are separated by the lesser wing of the sphenoid bone, while the middle and posterior cranial fossa are divided by the back of the petrous part of the temporal bone. Upon removing the calvarium, the cranial fossae become apparent.
• 06:00 - 07:00: Posterior Cranial Fossa The chapter discusses the three cranial fossae: anterior, middle, and posterior. It highlights how the lesser wing of the sphenoid bone separates the anterior and middle fossae, while the petrous part of the temporal bone separates the middle and posterior fossae. The Ethmoid bone, located in the anterior cranial fossa, is compared to a sieve or colander due to its appearance.
• 07:00 - 08:00: Base of the Skull and Foramina This chapter explores the base of the skull and its foramina, focusing on the various critical structures within it. A key highlight is the cribriform bone and the cribriform foramina, which contain holes that facilitate the olfactory nerves' travel from the nasal cavity to the olfactory bulb via the ethmoid bone, allowing the brain to receive olfactory (smell) sensations. Additionally, the chapter touches upon the lesser wing of the sphenoid bone.
• 08:00 - 09:00: Conclusion The chapter 'Conclusion' delves into the structures within the middle cranial fossa, specifically focusing on the optic canal and superior orbital fissure. The description includes the direction in which these canals lead towards the orbit. However, due to visibility constraints, the chapter shifts perspective to an anterior view of the orbit, particularly illustrating the optic canal and superior orbital fissure from the right orbit view.

The Skull Transcription

• 00:00 - 00:30 okay I'm gonna do an overview of the skull and answer the questions what are the primary bones and sutures of the skull what are the cranial fossae and what openings do cranial nerves and vessels traverse hello everyone my name is dr. Morton and I'm the noted anatomist so I'm gonna cover the bones of the skull the sutures in the cranial fossa and I'm gonna start with the bones of the skull so here's the frontal bone and it gets its name because it's frontal lat and frontal is Latin for forehead and it's the bone of your forehead then the zygomatic bone here is your cheek bone and then your maxilla
• 00:30 - 01:00 bone is here and it's called maxilla because Maxell is Latin for jaw it's your upper jaw the parietal bone here in the lateral view of the skull is this one here in lime green in parietal is Latin for a wall whenever you see that word pride alike prattle pleura prattle pericardium prattle peritoneum or bridle bone it's forming the wall of something the temporal bone is this bone here in salmon color and temporal is Latin for time because if you were to add the ear that is the area where gray hair is brought in gray hair comes with time and
• 01:00 - 01:30 that's where you usually start getting gray hair okay so the petrous part of the temporal bone here on the lateral side is all right there now I show that with an arrow but you really don't see it because it's inside the temporal bone and because the word Petrus means rock it's best to see that in a lateral x-ray and it's the most dense bright or white area of an x-ray it's a happy face for me if I find that it helps me to find other structures now the temporal bones also the external acoustic meatus which
• 01:30 - 02:00 is right here external for outside acoustic for hearing and meatus and a canal it goes into your eardrum it's that opening right there the sphenoid bone is this here it's forming as wedge-shaped on the side of the skull I'm going to talk more about that later the mandible is here and the mandible gets its name because it's Latin to chew because it's the bone that allows you to move your jaw and chew or masticate the occipital bone is here in this purple color and occipital is Latin for the back of the skull or back of the skull
• 02:00 - 02:30 now let's go from bones to sutures now sutures is Latin to bind to sew or a seam it's like a stitch because here when you take a look that's what it looks like is a stitch or a suture and so early an animus said you know it also looks like a stitch that so they called it that they use the word suture the first suture we're going to cover is a coronal suture it connects bridle and frontal bone so here are the parietal and the frontal bones and there is the coronal suture and it courses in the coronal plane the squamous suture
• 02:30 - 03:00 connects parietal and temporal bone so this lateral view there's the prattle and temporal bones and there is the squamous or squamosal suture the lambdoid suture connects parietal and occipital bones so there are the parietal bones and there's the occipital bone and that is the lambdoid suture gets its name because lambda is a Greek alphabet symbol that looks like that and that's what the suture looks like now the sagittal suture connects our parietal bone so here's a superior view
• 03:00 - 03:30 of the skull there are two prattle bones and that is the sagittal suture which runs right in the sagittal plane the tirion is a small suture it's connecting our parietal frontal sphenoid and temporal bones right there and it gets its name because this is where Hermes that God used to put wings as well as on his ankles is right there and so that's why the tairy on is called is Latin for a wing now let's go to cranial fossae and a cranial fossae are three large
• 03:30 - 04:00 stare like depressions in the floor of the cranial cavity so here's a sagittal section of the skull from a lateral view and there's the anterior cranial fossa step down is the middle cranial fossa and a step down is the posterior cranial fossa and what separates the anterior middle cranial fossae is the lesser wing of the sphenoid bone and the middle and posterior cranial fossa are separated by the back of the petrous part of the temporal bone so let's take the calvarium off remove it and that's where we're gonna see our cranial fossa is
• 04:00 - 04:30 inside there and so let's do that again our anterior middle and posterior cranial fossae and the lesser wing separates our anterior and middle and the petrous part of the temporal bone separates our middle and posterior cranial fossa so let's talk about the anterior cranial fossa first and inside that is the ethmoid bone there in green and ethmoid is Latin or Greek part of me for a sieve or screen or something like that because doesn't the bone kind of look like that like you Bua colander with spaghetti through that
• 04:30 - 05:00 or not spaghetti but the water going through that and so the cribriform bone has all of these holes called the cribriform foramina the cribriform foramen of those openings because inside the nasal cavity or olfactory nerve ascends up to the bottom of the olfactory to the ethmoid bone and then those cribriform foramina allowed for the traversing of the olfactory nerves to the olfactory bulb which brings sensation of smell to the brain all right there's the lesser wing the sphenoid bone in yellow and it's what's
• 05:00 - 05:30 separating our anterior and middle cranial fossae all right now let's go to the middle cranial fossa and two of the structures begin or the optic canal and superior orbital fissure there's the optic canal and going into the orbit that way and the superior orbital fissure going into the orbit that way but because we don't see a very good view of those two structures I'm instead gonna take a look at the orbit from an anterior view here's the right orbit and there's the optic canal the superior orbital fissure and the
• 05:30 - 06:00 inferior orbital fissure I'll just throw in four extra so let's do that again except we're gonna take and superimpose the schematic and blow it up to make it easier to see say optic canal superior orbital fissure inferior orbital fissure now in the optic canal are two structures we have cranial nerve 2 also known as the optic nerve that's what allows you to see that's what goes to the retina and right alongside that snug as a bug in a rug is the ophthalmic artery which is a branch off the internal carotid artery and it supplies
• 06:00 - 06:30 the orbit as well as the retina now in the superior orbital fissure we have a few things as well there in blue is the superior ophthalmic vein that drains to the cavernous sinus and also to the facial thing and also the following cranial nerves cranial of three four five and six now to be truthful these four of five structures are not in this order they're in different orders but it makes it easier for me to remember them and since it's such a small space it works cranial nerve three for v1 the
• 06:30 - 07:00 ophthalmic branch of the trigeminal nerve and six and then we have our inferior orbital fissure and there's our inferior ophthalmic vein that go to the cavernous sinus as well and the pterygoid plexus of veins as well as the facial thing goes two ways and then we have the cranial nerve v2 the infraorbital nerve it's the continuation of the v2 branch from the framing rotunda and then our inferior orbital artery and vein okay there's all those
• 07:00 - 07:30 structures so now let's go back to the middle cranial fossa we see the optic canal and super orbital fissure let's go to the next one here and this is showing our sella turcica which houses the pituitary gland so here's a sagittal section and there is a sella turcica gets its name because it means a Turkish saddle I don't really see a Turkish saddle very often but I guess that's what it looks like and the pituitary gland goes xi and sits right inside that sella turcica next is the carotid canal that's located right there now the
• 07:30 - 08:00 carotid canal is a canal it goes one from the bottom of the skull and then into the middle cranial fossa so let's zoom in on this one and go there's our internal carotid artery and let's focus on there and the bottom of the skull is there's the beginning of the carotid canal and then what we're looking at here in the middle cranial fossa is the other part of the carotid canal and the internal carotid artery traverses that and this is where we're seeing right now is inside the middle cranial fossa where the carotid canal exits the framin rotunda framing for opening and rotunda
• 08:00 - 08:30 for round and the framing rotunda ms what allows for a branch of the trigeminal nerve cranial nerve 5 and it's specifically the v2 maxillary branch that goes through the frame and rotunda so when we look in here there's v2 and there's the frame in rotunda and then that nerve goes through the infra in 4 orbital fissure and out the inferior orbital foramen and also goes to your Maxell and palate now the frame in O Valley gets its name for opening that is oval and the v3 branch of the
• 08:30 - 09:00 trigeminal nerve traverses that going through the foramen ovale and goes and enters into the infra temporal fossa into the oral cavity so v2 goes to the maxilla v3 goes to the mandible the frame and spinosum is this very small opening and it goes traverses traversed by the middle meningeal artery at branch off or maxillary artery and it's applies the dura mater and that is the Terry on where the middle and meningeal
• 09:00 - 09:30 artery course is deep to it so if you crack the Terry on a very thin portion of the bone where that suture is then you could rupture the middle meningeal artery and bleed but separating the dura from the skull that's a an epidural hematoma now let's go to the posterior cranial fossa and inside the posterior cranial fossa we have the internal acoustic meatus that goes into the petrous part of the temporal bone and so there is our internal acoustic meatus which is traversed by cranial nerve seven facial nerve and eight
• 09:30 - 10:00 vestibulocochlear nerve and they all go into the internal ear where the semicircular canals and cochlea are and those very delicate important structures are housed in the hardest bone in the skull the petrous part of the temporal bone all right so now we also have the jugular foramen that's right there and it gets its name because jugular is Latin for neck or throat now why is it called that well there's the jugular foramen and it's traversed by the internal jugular vein which courses down into the neck now the jugular foramen
• 10:00 - 10:30 also has a few other things that go through it this is a coronal section looking for the back of the skull you have cranial nerves nine ten and eleven glossopharyngeal Vegas and spinal accessory that also traverse this jugular foramen it's a big one it's an important one so the jugular foramen is traversed by our internal jugular vein and cranial nerve nine and ten and eleven I love it when nature put those nerves in order it's very nice now the hypoglossal canal is found at the front of the frame and
• 10:30 - 11:00 magnum right there and it's called hypoglossal because hypo is greek for under and glossa for tongue because the nerve cranial nerve 12 the hypoglossal nerve traverses this opening and goes to all the muscles under the tongue and what moves your tongue okay base of the skull the cranial fossa now we're looking at the inferior view of the skull okay and the styloid process of the temporal bone is right there styloid is Greek for pillar-like because in that red the circle shows it has this pillar
• 11:00 - 11:30 like structure for a muscle and ligament attachment then we have the mastoid process of the temporal gets its name because its breast shape and it's the on the back of the ear like that it's where the sternocleidomastoid muscle attaches now there's an opening here it's important clinical opening and so Natomas said what do we call this opening this between the styloid and mastoid processes I know we'll call it the stylo mastoid foramen the style of mastoid foramen is what traverses is
• 11:30 - 12:00 traversed by the facial nerve proper so there's our facial nerve there's a facial nerve proper there's the facial canal and there we've got that facial nerve proper that traverses the stylo mastoid foramen and then the facial nerve proper goes through the product land and innervates all the muscles of facial expression there at the base of the skull is a style of mastoid framin for facial nerve proper now the frame in Magnum frame and for opening a magnum for huge there it is and it's important
• 12:00 - 12:30 because the frame in Magnum is traversed by the vertebral arteries that supply the posterior part of the brain spinal accessory nerve that innervates your traps and sternocleidomastoid it goes through the frame in Magnum and then back down through the jugular frame and it's kind of a cool course and then the most important thing that spinal cord is what traverses the frame in Magnum and that my friends is an overview of the skull in a nutshell [Music]
• 12:30 - 13:00 [Music] [Music]