Axial Skeleton Flashcards
How many bones are in the human body?
206
How many bones are in axial skeleton?
80
What is the axial skeleton?
It forms the longitude axis of the body. From the skull down to the coccyx. This excludes the arms. Some call core of the body.
What are the functions of the axial skeleton?
It supports and protects organs in the body cavity. It attaches to the muscles of the head, neck, trunk, and appendicular skeleton.
What are the main bones of the axial skeleton?
Skull and associated bones
Vertebral column
Thoracic cage
What are some specific bones in the axial skeleton?
Skull and Associated Bones:
The skull includes the cranium and facial bones.
The associated bones include the auditory bones and the hyoid bones.
Thoracic Cage:
Sternum
Ribs
Vertebral Column:
Vertebrae
Sacrum
Coccyx
What bones is the skull made of and how many are there?
The skull and 22 bones and 7 associated bones, totalling 29 bones. Of the skull bones there are 8 cranial bones that protect the brain and 14 facial bones that support the eyeballs and protect and support entrances to the digestive and respiratory tracts.
What are the skull sutures?
They are immovable joints in the skull that firmly tie bones together. They are made of dense CT. There are four in total; corona (crown at the front), sagittal (down the middle), lambdoid (at the back connecting the occipital bone), and squamous (along the side connecting the temporal bone).
What are the eight cranial bones?
Frontal bone
Occipital bone
Parietal bones (2)
Temporal bones (2)
Sphenoid
Ethmoid
What is the frontal bone and where is it located?
Anterior surface of the cranium and upper eye sockets.
Contains frontal sinuses.
Marks: supraorbital foramen notch- for blood vessels of eyebrows, eyelids, and frontal sinuses.
What is the occipital bone and where is it located?
Posterior and inferior surfaces of the cranium.
Articulations:
- parietal bones
- temporal bones
- sphenoid bone
- first cervical vertebrae (atlas)
What are the marks of the occipital bone?
External occipital protuberance
External occipital crest:attach ligaments
Superior and inferior nuchal lines: attach ligaments
Occipital condyles: articulate with vertebral column
Occipital foramina:
- foramen magnum: connects cranial and spinal cavities
- jugular foramina: for jugular veins
- hypoglossal canals: for hypoglossal nerves
What are the parietal bones and where are they located?
Part of the superior and lateral surfaces of the cranium.
Marks:
- superior and inferior temporal lines: temporal is muscle
- groves for cranial blood vessels (on the media, surface)
What are the temporal bones and where are they located?
Part of lateral surfaces of the cranium
2 portions:
- squamous part: borders the squamous suture
- petrous part: encloses structures of the inner ear
Functions:
- surround and protect inner ear
- attach muscles of jaws and head
Articulations: zygomatic, sphenoid, parietal, and occipital bones as well as mandible
What are the marks of the temporal bones?
Zygomatic process:
- inferior to the squamous part
- articulates with temporal process of zygoma
- forms zygomatic arch
Mastoid process:
- for muscle attachment
- contains air cells connected to middle ear
Styloid process:
- to attach tendons and ligaments of the hyoid bone, tongue, and pharynx
Mandibular fossa: articulates with the mandible
What are the foramina of the temporal bones?
External acoustic (auditory) canal:
- ends at tympanic membrane
Internal acoustic (auditory) canal:
- for blood vessels and nerves of the inner ear
- facial nerve (inlet)
Carotid canal:
- for internal carotid artery
Stylomastoid foramen:
- for facial nerve (exit)
What are the facial bones and how many?
There are nine superficial facial bones; 2 maxillae, 2 zygomatic bones, 2 lacrimal bones, 2 nasal bones, and 1 mandible. There are five deep facial bones; 2 palatine bones, 2 inferior nasal conchae, and 1 vomer. This is a total of 14 facial bones.
What is the function of the maxillae?
- form inferior orbital rim
- form lateral margins of external nares
- form upper jaw and hard palate
- support upper teeth
- contain maxillary sinuses (largest sinuses)
What is the articulations of the maxillae?
- all facial bones on the same side! EXCEPT the mandible
- other maxillary bone
- frontal bone
- ethmoid bone
What are the marks of the maxillary bones?
Alveolar processes
Palatine process:
- anterior part of the hard palate (roof of mouth)
Infraorbital foramen
Maxillary sinus
What are the palatine bones and what are the articulations?
Posterior portion of the hard palate
Contribute to the floors of the orbits
Articulations:
- other palatine bone
- maxilla
- sphenoid
- ethmoid
- inferior nasal concha
- vomer
What are the nasal bones and what are the articulations?
Support the bridge of the nose 1
Connect to cartilages of the distal part of the nose (external nares) 2
Articulations:
- other nasal bone
- ethmoid
- frontal bone
- maxilla
What are the vomer and what are the articulations?
Inferior part of the bony nasal septum
Articulations:
- sphenoid
- ethmoid
- palatine bone
- maxilla
- cartilaginous part of the nasal septum
What are the functions of the inferior nasal conchae and what are the articulations?
Functions:
- create air turbulence in the nasal cavity
- increase the epithelial surface area
- warm and humidify inhaled air
Articulations:
- ethmoid
- maxilla
- palatine bone
- lacrimal bone
What are the zygomatic bones and what are the marks on them?
They are also known as the cheekbones or malar bones.
They contribute to rum and lateral wall of the orbit.
Marks:
- temporal process: articulates with zygomatic process of temporal bone and forms zygomatic arch.
What are the lacrimal bones and what are the marks and articulations?
Smallest facial bones
Form part of medial wall of the orbit
Articulations:
- frontal bone
- maxillary bone
- ethmoid
Marks:
- lacrimal sulcus
What is the mandible and what are the functions, articulations, and what does it consist of?
Largest and strongest facial bone
Function:
- forms the lower jaw
- holds the lower teeth
Articulations:
- mandibular fossae of temporal bones
Consists of:
- body: horizontal portion
- ramus: ascending from the mandibular angle
What are the marks of the mandibular body?
Alveolar processes:
- support lower teeth
Mental protuberance:
- attaches facial muscles
What are the marks of the mandibular ramus?
Condylar process:
- articulates with temporal bone at temporomandibular joint (TMJ)
Coronoid process:
- insertion point for temporalis muscle (closes the jaws)
Mandibular notch:
- between condylar and coronoid processes
What is the foramina of the mandible?
Mental foramen:
- lateral
- for sensory nerves of lips and chin
Mandibular foramen:
- medial
- entrance to the mandibular canal
- for blood vessels and nerves of lower teeth
What is the orbital complex?
Forms the eye sockets (orbits).
Parts of seven cranial facial bones: frontal, maxilla, zygomatic, lacrimal, sphenoid, ethmoid, and palatine.
What are the bones of the orbital complex?
Roof: frontal bone
Floor: maxillary bone
Medial wall: maxillary, lacrimal, and ethmoid bones
Lateral wall: zygomatic bone
Posterior wall: sphenoid and palatine bones
What are the parts of the nasal complex?
Superior wall:
- frontal, sphenoid, and ethmoid bones
Lateral walls:
- maxillary, lacrimal, ethmoid, and inferior nasal conchae
Nasal bridge:
- maxillary and nasal bones
Nasal septum:
- Cartilaginous part: hyaline cartilage
- Bony part: ethmoid (superior part) and vomer (inferior part)
What are the paranasal sinuses?
Air filled cavities connected to the nasal cavities
Functions:
- decrease the weight of the skull
- mucus membrane lining protects entrances of the respiratory system
What are the parts of the paranasal sinuses?
Maxillary
Frontal
Sphenoidal
Ethmoidal
What is different about an infant skull?
Large compared to the body
Grows rapidly
Has many ossification centers
Fusion is not complete at birth
What are the fontanels?
Areas of fibrous connective tissue (soft spots)
Cover unfused sutures in the infant skull
Allow the skull to flex during birth
4 fontanelles (fontanels)
Anterior fontanel:
- Frontal (metopic), sagittal, and coronal sutures
Posterior (Occipital) fontanel:
- lambdoid and sagittal sutures
Sphenoidal fontanels:
- squamous and coronal sutures
Mastoid fontanels:
- squamous and lambdoid sutures
What are the bones associated with the skull?
There are seven total bones associated with the skull:
Auditory ossicles:
- malleus
- incus
- stapes
Hyoid bone:
- supports the larynx
- attaches muscles of the larynx, pharynx, and tongue
- medicolegal value
What is the vertebral column?
Protects the spinal cord
Supports the head and body
26 bones:
- 24 vertebrae
- sacrum
- coccyx
What are the regions of the vertebral column?
7 Cervical (C)
12 Thoracic (T)
5 Lumbar (L)
1 Sacral (S)
1 Coccygeal (Co)
Vertebrae are numbered:
- by region, from top to bottom
Articulation:
- articulate with each other
- C1 articulates with skull
- L5 with sacrum
- sacrum articulates with the coccyx
Vertebrae of each region:
- have characteristics determined by functions
What are the curvatures of the vertebral column?
Primary curves:
- thoracic and sacral curves: present during fetal development and accommodation curves (accommodate internal organs)
Secondary curves:
cervical and lumbar curves: develop after birth and compensation curves (shift body weight for upright posture)
What is the structure of a vertebra?
Vertebral body (centrum):
- transfers weight along the spine
Vertebral arch:
- posterior margin of vertebral foramen
- consists of: pedicles (walls), laminae (roof), spinous process, and transverse process
What are the articulations process of a vertebra?
Lateral projections between laminae and pedicles
Include:
- superior articular process
- inferior articular process
What are the foramina of the vertebrae?
Vertebral foramen:
- foramina form vertebral canal: encloses the spinal cord
Intervertebral foramina:
- gaps between pedicles of adjacent vertebrae
- for nerve connections to spinal cord
What are the intervertebral discs?
Pads of fibrocartilage
Separate vertebral bodies
Absorb shocks
What are the characteristics of cervical vertebrae?
Small body (support only head)
Large vertebral foramen (largest part of spinal cord)
Concave superior surface
Spinous process:
- short
- notched (bifid) tip
- C1 (atlas) has no spinous process
Transverse processes:
- are fused to costal processes
- create transverse foramina (protect arteries and veins)
What is the Atlas? (C1)
Articulates with occiptal condyles of skull
Has no body or spinous process
Has a large, round foramen within anterior and posterior arches
What is the axis? (C2)
Supports the atlas
Has heavy spinous process (to attach head and neck muscles)
Dens:
- tooth like process projects from the axis body
- articulates with the atlas atlantoaxial joint
What is the vertebra prominens? (C7)
Transition to thoracic vertebrae
Has a long spinous process with a broad tubercle
Has large transverse processes
Ligamentum nuchae (elastic ligament):
- extends from occipital protuberance to C7 spine
What are the characteristics of the sacrum?
Curved (more in males than in females)
Protects reproductive, urinary, and digestive (pelvic) organs
Articulates with hipbones, L5, and coccyx
Attaches broad muscles that move the thigh
Adult sacrum:
- consists of 5 fused sacral vertebrae
- fuses between puberty and ages 25–30
- leaving transverse lines
What are the marks of the sacrum?
Sacral canal: replaces the vertebral canal
Sacral hiatus: opening at the inferior end of the sacral canal formed by ridges of sacral cornua
Sacral tuberosity: attaches ligaments of the sacroiliac joint
Sacral promontory: at the center of the base
Median sacral crest: rudimentary spinous processes
Sacral foramina: 4 on each side and for sacral nerves & arteries
What is the coccyx?
Attaches ligaments and a constricting muscle of the anus.
Mature coccyx: consists of 3 to 5 fused coccygeal vertebrae
First 2 coccygeal vertebrae: have transverse processes and have unfused vertebral arches
Coccygeal cornua: formed by laminae of 1st coccygeal vertebra
What is the thoracic cage?
Protects the thoracic cavity
Consisting of 25 bones and 12 T vert.
Attaches muscles of: respiration, vertebral column, pectoral girdle, and upper limbs
Consists of:
24 ribs (costae)
sternum (breastbone)
thoracic vertebrae
What are the ribs?
12 pairs of flat and curved bones
Extend from the thoracic vertebrae
Flexible and mobile
What is the structure of the ribs?
Head (capitulum):
- at the vertebral end of the rib
- has superior1 and inferior2 articular facets
Neck:
- short area between the head and the tubercle
Tubercle (tuberculum):
- small dorsal elevation
- has an articular facet that contacts the facet of its thoracic vertebra (at T1–T10 only)
Shaft (body):
- attaches muscles of the pectoral girdle and trunk
- attaches to the intercostal muscles which move the ribs
What are the functions of the ribs?
Absorb shocks
Breathing: rib movements affect width and depth of thoracic cage and changing its volume during respiration
What are the types of ribs?
True ribs (ribs 1–7): vertebrosternal ribs and attach directly to sternum by costal cartilages
False ribs (ribs 8–12): do not attach directly to the sternum
2 types:
- vertebrochondral ribs (ribs 8–10): fuse together and merge with cartilage before reaching the sternum
- floating or vertebral ribs (ribs 11–12): connect only to the vertebrae and have no connection with the sternum
What is the sternum?
Flat bone
In the midline of the thoracic wall
3 parts:
manubrium
body
xiphoid process
What is the manubrium?
Superior portion of sternum
Broad, triangular shape
Articulates with: clavicles and cartilages of 1st rib pair
Has a jugular (suprasternal) notch between clavicular articulations
What is the strenal body?
Tongue-shaped
Articulates with: costal cartilages of ribs 2–7
Sternal angle: anterior angle at the junction of manubrium and body
What is the xiphoid process?
Smallest part of the sternum
Attaches to:diaphragm and rectus abdominis muscle
Last part of sternum to fuse
Can easily be broken
