Week 5 - Axial Skeleton (Chapter 7)
Number of bones in the axial skeleton
80
Bones that lie around the axis of the human body: skull, ear bones, hyoid bone, ribs, sternum, bones of vertebral column
Axial Skeleton
4 Shapes of Bones:
Long, flat, irregular, sesamoid
Bones that are thin & composed of two parallel plates of compact bone with spongy bone in between; provide protection and extensive areas for muscle attachment
Flat
Examples of flat bones:
Cranial bones, sternum, ribs
Bones with complex shapes that don't fit into other categories; vary in spongy & compact bone content
Irregular
Examples of irregular bones:
Vertebrae, hip bones, certain facial bones, calcaneous
Bones with a seasame seeds shape; develop in tendons under friction & strain
- Vary in number along individuals, typically a few millimeters
- Protect tendons from wear & tear
Sesamoid
Examples of sesamoid bones:
Patellae, quadriceps femoris tendon
Bones are small, flat bones located in sutures (joints) between cranial bones
-Number varies
Sutural bones
One of the major types of surface markings: _________,_______/_______ that either form joints or serve as attachment points for connective tissue (ligaments & tendons)
- In response to tension on a bone surface from ligaments, aponeuroses, & fasciae, new bone is deposited resulting in raised areas
Processes, or projections/outgrowths
Bony framework of the head consisting of twenty- two bones (excluding middle ear bones). Rests on the superior end of the vertebral column. Includes cranial base.
Skull
The 8 bones of the cranium:
-frontal bones
-two parietal bones
-two temporal bones
-occipital bone
-sphenoid bone
-ethmoid bone
Bones that form the anterior part of the skull surrounding the mouth, nose, & orbits
Facial bones
The 14 Facial Bones:
-two nasal bones
-two maxillae
-two zygomatic bones
-mandible
-two lacrimal bones
-two palatine bones
-two inferior nasal concha bones
-vomer
- Protects the brain & stabilizes its positions alongside blood vessels & nerves via meninges
- Provides attachment points for muscles that more the head and create facial expressions
- Protects special sense organs for vision, taste, smell, etc. & digestive and respiratory entrances, supports head
Skull Functions - PASS
This bone forms the forehead, roofs of eyes (sockets), and most of the anterior cranial base
- Initially divided into the left & right sides, united by the metopic suture
Frontal bone
Key Features of Frontal Bone:
Frontal Squama: The flat part that makes up your forehead. It slopes down and then stands straight up above your eyes.
Supraorbital Margin: The thick edge at the top of your eye sockets.
Supraorbital Foramen/Notch: a small hole or gap in the thick edge above your eyes. Sometimes it’s not fully formed.
Sinuses: These are air-filled spaces behind your forehead that are lined with a slimy layer called mucus.
These two bones: These bones make up most of the sides and top of the skull.
Inside the bones: The inner surfaces of these bones have bumps and dips that hold blood vessels. These blood vessels supply the dura mater, which is the outer layer protecting the brain
Parietal bones
These paired ______ bones make up the lower sides of the skull and part of the bottom of the skull.
Temporal Bones
Temporal Bones Features
Temporal squama- thin, flat part of the temporal bone
-Forms the anterior & superior part of the temple (around the ear)
The _______ process sticks out from the bottom part of the temporal bone. It connects with the part of the cheekbone.
Zygomatic process
Located at the bottom of the skull, between the sphenoid and occipital bones, this area contains parts that help with hearing and balance (the internal and middle ear).
Petrous portion of temporal bone
Opening for facial & vestibulicochlear nerves
Internal acoustic meatus
This is a rounded bump where muscles attach, and it's found close to the ear canal.
Mastoid process
These is located on the bottom back surface of the zygomatic process of the temporal bone. It works with the jawbone to form the temporomandibular joint. It’s found behind and below the ear canal and has air-filled spaces called mastoid air cells that connect to the middle ear.
Mastoid Process
The petrous portion of the temporal bone has a _______ canal that lets the carotid artery pass through. It’s found behind this canal and in front of the occipital bone. This area also has a passage for the jugular vein and three nerves that go to the brain.
Carotid Canal
A slender, pointed projection that serves as an attachment point for muscles and ligaments of the neck and tongue.
Styled process
Passage for the facial nerve & stylomastoid blood vessels, located between the styloid & mastoid processes
Stylomastoid foremen
The facial bones are:
The nasal bones, maxillae, zygomatic bones, lacrimal bones, palatine bones, inferior nasal concha bones, mandible, and
occipital bone
This bone forms the posterior part of the cranial cavity and most of the cranial base
Occipital
Occipital bone features:
Foramen magnum
Hypoglossal Canal
Ligamentum Nuchae
Nuchal Lines
Is a large opening at the base of the skull. It’s where the spinal cord connects to the brain.
- Allows passage of vertebral & spinal arteries
- The oval processes on either side of the foramen magnum are called the occipital condyles. They help connect the skull to the spine.
Foramen magnum
Is located above each occipital condyle. It allows the hypoglossal nerve, which controls tongue movements, to pass through.
Hypoglossal Canal
Prominent projection above the foramen magnum, often felt as a bump on the back of the head
External Occipital Protuberance
It runs from the external occipital protuberance at the back of the skull down to the seventh cervical vertebra, helping support the head.
Ligamentum Nuchae/Nuchal Ligament
The superior nuchal lines and inferior ______ are two pairs of ridges that extend out from the external occipital protuberance. They serve as attachment points for muscles in the neck and back.
Nuchal Lines
This bone is positioned in the middle part of the cranial base.
- Known as the "keystone" of the cranial base because it connects with all other cranial cavity bones.
- Resembles a butterfly shape
- Forms base of skull.
Sphenoid Bone
These stick out to the sides from the main part of the sphenoid bone, helping to form the front sides of the skull base and the walls of the eye sockets, located just in front of the temporal bone.
Greater Wings of the Sphenoid
Smaller, wing-like structures of the sphenoid bone that form a ridge above and in front of the greater wings. They are part of the base of the skull and contribute to the back of the eye socket.
Lesser Wings of the Sphenoid
It’s located between the body of the sphenoid bone and the lesser wing, just in front of the sella turcica. The _____ canal allows the optic nerve and blood vessels to pass into the eye socket.
Optic Canal
It’s a triangular opening located between the greater and lesser wings of the sphenoid bone, allowing blood vessels and cranial nerves to pass into the eye socket.
Superior Orbital Fissure
It is a delicate, spongy bone that helps form part of the front base of the skull, the inner walls of the eye sockets, the upper part of the nasal septum, and the sides of the nasal cavity.
Ethmoid Bone
Key Features of Ethnoid Bone:
Cribriform plate is a flat, horizontal section that makes up the roof of the nasal cavity.
The crista galli is a triangular projection that sticks up from this plate. It serves as an anchor point for the falx cerebri, which helps separate the two halves of the brain.
This plate forms the superior portion of the nasal septum
Perpendicular Plate
They are separate bones that help filter air, improve the sense of smell, and cleanse the air we breathe before it goes into the respiratory system. They are scroll-like in shape and located below the middle nasal conchae of the ethmoid bone, forming part of the lower side walls of the nasal cavity.
Inferior Nasal Conchae
Thin, curled bony structures that increase surface area in the nasal cavity for warming and humidifying inhaled air. Help trap inhaled particles in mucus.
Superior and Middle Nasal Conchae
Paired, small, flattened, rectangular bones forming the bridge of the nose. Protect the upper entry to the nasal cavity and provide attachment for facial expression muscles.
Nasal Bones
Small, paired bones that look like fingernails and are the smallest bones in the face. They are located behind and to the side of the nasal bones, forming part of the inner wall of each eye socket. The lacrimal bones have a small fossa (depression) that holds the lacrimal sac, which collects tears and drains them into the nasal cavity.
Lacrimal Bones
2 L-shaped bones that make up the back part of the hard palate (the roof of the mouth) and help form the floor and walls of the nasal cavity, as well as a small section of the bottom of the eye sockets. They provide support for the hard palate and play a role in shaping the nasal cavity and orbits.
Palatine Bones
A triangular bone that makes up the lower part of the nasal septum, which separates the left and right sides of the nasal cavity. It connects above with the perpendicular plate of the ethmoid bone and the sphenoid bone, and below, it joins the maxillae and palatine bones along the middle line.
Vomer
They are paired bones that form the upper jaw and connect with nearly every facial bone except for the mandible (lower jaw). The maxillae help make up parts of the floors of the eye sockets, the sides and bottom of the nasal cavity, and most of the hard palate, which separates the nasal cavity from the mouth.
Maxillae
Maxillae Features:
Contain sinuses that drain into nasal cavity
- Have dental alveoli
- Fusion of the maxillae occurs before birth; failure to fuse results in cleft palate
Refers to the small openings or canals in the maxilla (upper jaw) that allow for the passage of nerves and blood vessels.
- One of the main ones is the maxillary sinus opening
Maxillary openings
Commonly called cheekbones.
- Form the prominence of the cheeks.
- Contribute to the lateral wall and floor of each orbit.
- Connect with the frontal, maxilla, sphenoid, and temporal bones.
Zygomatic Bones
This arch is the bony structure on the side of the face: formed by the zygomatic bone & part of the temporal bone
Zygomatic Arch
Lower jawbone: is the largest and strongest facial bone.
- It is the only movable skull bone, aside from the auditory ossicles
- Has 2 perpendicular branches extending from the body.
Has 4 prominent projections
Mandible
Refers to a projection or outgrowth from a bone or other structure. These projections often serve as attachment points for muscles, ligaments, or tendons, or they can form joints with other bones.
"Process"
One of the mandible processes:
It projects backward and connects with the mandibular fossa and articular tubercle of the temporal bone to form the temporomandibular joint (TMJ).
Condylar Process
Means to form a joint or connection between two bones. When two bones articulate, they come together at a joint, allowing for movement or stability.
"Articulate" or "Articulates"
One of the mandible processes: It sticks up in front and serves as an attachment point for the temporalis muscle, which helps with chewing.
Coronoid Process
One of the mandible processes: It is the indentation located between the coronoid process and the condylar process of the mandible.
Mandibular Notch
One of the mandible processes: It is the bony ridge that holds the sockets for the lower teeth.
Alveolar Process
The ___________ fossa is a shallow depression in the temporal bone where the lower jaw (mandible) fits in.
Mandibular
The _____ tubercle is a bump on the temporal bone that helps form the joint with the mandible. Together, they allow the jaw to move up and down and side to side.
Articular
The __________ work with the first cervical vertebra (atlas) to create the atlanto-occipital joint, allowing you to nod your head up and down.
Occipital condyles
A small opening below the eye socket that lets nerves and blood vessels pass to the face.
Infraorbital Foramen
An opening in the hard palate behind the front teeth for nerves and blood vessels to enter the mouth.
Incisive Foramen
A gap in the eye socket that allows nerves and blood vessels to enter from the maxilla and sphenoid bone.
Inferior Orbital Fissure
A vertical partition that divides the nasal cavity into right and left sides. It consists of bone and cartilage, specifically the vomer.
Nasal Septum
Hyaline cartilage forming the anterior portion of the septum, articulating with the vomer
Septal Nasal Cartilage
Completes the remainder of the nasal septum by articulating with the superior border of the vomer.
Perpendicular Plate of the Ethmoid Bone
The bones of the orbit (Eye socket) are:
Frontal, sphenoid, ethmoid, palatine, zygomatic, lacrimal, and maxilla.
Optic Canal: Where the top meets the inner side.
Superior Orbital Fissure: At the top outer corner.
Inferior Orbital Fissure: At the bottom outer corner.
Supraorbital Foramen: On the upper inner edge of the frontal bone.
Lacrimal Fossa: Found in the lacrimal bone.
Openings of the Eye Socket
Each eye socket is shaped like a _____
Pyramid
Each side of the eye socket:
Top: Frontal & sphenoid bones
Outer side: Made by zygomatic & sphenoid bones
Bottom: Made by maxilla, zygomatic & palatine bones
Inner side: Made by maxilla, lacrimal, ethnoid, sphenoid bones
_______ are openings for blood vessels, nerves, or ligaments.
Foramina
______ are immovable fibrous joints that hold most skull bones together, often movable in infants to allow for growth.
The names of _____ typically reflect the bones they connect
Sutures
Key Sutures
Coronal suture - connects the frontal bone to both parietal bones.
Sagittal suture - the joint that connects the two parietal bones along the top center of the skull.
Lambdoid suture - joins the parietal bones to the occipital bone
Squamous sutures - unite the parietal and temporal bones on the side of the skull.
These sinuses are small cavities in certain skull bones near the nasal cavity.
- They are lined with mucus and drain into the nasal cavity. - Help the skull grow without adding weight, produce mucus, moisten inhaled air, and improve voice quality
Paranasal sinuses
Are mesenchyme-filled spaces between cranial cavity bones that are present at birth. "Soft spots"
Fontanels
The 6 Main Fontanels:
Anterior Fontanel: The largest, diamond-shaped, between the parietal and frontal bones; closes by 18-24 months.
Posterior Fontanel: Smaller, between the parietal and occipital bones; closes about 2 months after birth.
Anterolateral Fontanels: Paired, between the frontal, parietal, temporal, and sphenoid bones; close around 3 months after birth.
Posterolateral Fontanels: Paired, between the parietal, occipital, and temporal bones; start closing 1-2 months after birth and finish by about 12 months.
The _____ bone is a U-shaped bone in the neck that doesn't connect to any other bones.
- It hangs from the temporal bones and is between the jaw and voice box. I
- t supports the tongue and has parts called lesser and greater horns for muscle attachment.
Hyoid
The ____, or backbone, is about two-fifths of a person's height and is made up of bones called vertebrae. It works with the sternum and ribs to form the trunk's skeleton and protects the spinal cord.
Spine
T or F: The spine is flexible, supports the head, and connects to the ribs, pelvis, and back muscles. It starts with 33 vertebrae in early development but usually has 26 in adults due to fusion in the lower regions.
True
There are ____ number of cervical vertebrae (cervic- = neck) located in the neck region
7
There are ____ number of thoracic vertebrae (thorax = chest) positioned posterior to the thoracic cavity
12
There are _____ number of lumbar vertebrae (lumb- = loin) that support the lower back.
5
There is ____ number of sacrum (SACrum = sacred bone) composed of five fused sacral vertebrae.
1
There is ____ number of coccyx typically consisting of four fused coccygeal vertebrae.
1
The adult spine looks straight from the front and back but has ____ curves when viewed from the side.
4
Primary Curves of the spine:
Thoracic and sacral (bend inward).
Secondary Curves of the spine:
Cervical and lumbar (bulge outward)
Function of spine curves:
Make the spine stronger, help with balance, absorb shocks, and protect against injuries.
All curves are fully developed by age ten, but some may change with age. _______ curves like kyphosis, lordosis, and scoliosis can cause issues with the spine.
Abnormal
_________ (ear) ossicles – Malleus, incus and stapes. Situated in the middle ear. Stapes is the smallest bone in the body. Total – 6; 3 in each ear.
Auditory
A set of bones forms the spinal column.
There are 7 cervical vertebrae (neck), 12 thoracic vertebrae
(trunk), 5 lumbar vertebrae, (abdomen & pelvic region), 1
sacrum (pelvic region) & 1 coccyx (pelvic region.
Total – 26
bones
Vertebral column
__________ – Sternum and ribs (25 total)
Thorax (thoracic cage or bony thorax)
_______ arch - 2 short, thick processes (pedicles) project posteriorly & unite to form lamina to form vertebral arch. This foramen allows spinal nerves from spinal cord to exit to supply to effector structures (organs, muscles etc).
Vertebral arch
Vertebral regions:
Cervical, thoracic, lumbar, sacral & coccygeal
The ribs:
True ribs (7 pair)
False ribs (3 pair)
Floating (4)