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SkeletalSystem-Axial.pptxAnatomy
Skeletal System
Skeletal System
Skeletal pertains to the bones of the body
Consists mainly of two tissues
Bone
Contains functional cells called osteocytes
Ossification is the process of bone formation
Bone is a dynamic organ; continually maintains and repairs throughout life
Cartilage
In embryos the skeletal system is mainly cartilage
Smooth, elastic connective tissue
Protects the ends of long bones
Found in several areas of the body: nose, ears, trachea, articulating area of bones
Structure of bone
Outer layer
Very dense
Referred to as compact bone
Contains
Intricate structural arrangements of rings of tissue containing bone cells
Haversian systems or osteons
Hardened intracellular substances (calcium, inorganic salts)
Structure of bone
Inner layer
Contains marrow
A highly vascularized, gelatinous tissue that contains hematopoietic and mesenchymal stem cells. These stems cells generate progenitor cells that differentiate into a variety of cell types, including osteocytes (bone cells), adipocytes (fat cells), myocytes (muscle cells), erythrocytes (red blood cells), and white blood cells
Structure of bone
Inner layer consists of cancellous bone
Porous or spongy tissue
Contains spaces occupied by red bone marrow
generate red blood cells (coloring this marrow red), white blood cells, and platelets
Structure of bone
Other structures
Periosteum: tough membrane that covers bone
Articular cartilage: covers and cushions bone ends where they form a joint
Parts of a Bone
Diaphysis: the shaft of a long bone
Epiphyses: ends of a bone
Medullary canal: contains yellow bone marrow
predominately located in the axial skeleton, specifically in the diaphysis of long bones. In contrast to red marrow, adipocytes are the primary cell type in yellow marrow
function as a fuel tank for the storage of lipids and triglycerides
Functions of bone
Support
Provides support and rigidity to soft tissue, maintaining normal erect posture
Protection
Help protect the more delicate vital organs
Movement
Serve as points of attachment for muscles which pull on bone, resulting in movement
Functions of bone
Storage
Stores minerals such as calcium
Hematopoiesis
Production of blood cells takes place in bone marrow
Bony landmarks
Antrum or sinus: Air cavity within a bone
Canal or meatus: tunnel-like passage or opening in a bone
Bony landmarks
Condyle: smooth, curved articular surface on a bone
Epicondyle: prominence just above a condyle
Bony Landmarks
Crest: prominent ridge on a bone
Fissure: narrow slit or groove between bones for passage of blood vessels or nerves
Bony Landmarks
Fontanel: temporarily unossified area between the cranial bones of an infant
Foramen: hole in a bone
Bony Landmarks
Fossa: depression in a bone
Head: ball-like articular projection on a bone
Bony Landmarks
Process: any prominent projection or outgrowth of bone
Septum: wall or partition which divides a body cavity
Tubercle or Tuberosity: bump or elevation on a bone
Divisions of the skeleton
206 classified bones
Does not include sesamoid bones
Bone embedded in a tendon
Does not include sutural bones
Bone chips sometimes found embedded between cranial bones (suture)
Divisions of the skeleton
Divided into two main subdivisions
Axial: All bones of the skull, thorax, and spine
80 total
Appendicular: bones of the upper extremities, pectoral girdle, lower extremities, and pelvic girdle
126 total
80 bones
Skull: 22 bones plus 6 ear ossicles
Small bones
May be subdivided into three categories
Cranium
Face
Ears
Axial skeleton
Cranium (8)
Frontal bone: forms the forehead area, the front, top of the cranium, and the upper part of the eye sockets
Cranium
Frontal Bone
Important landmarks of the frontal bone
Supraorbital margins: upper rim of the eye sockets
Superciliary arches: elevations at and above the medial ends of the eyebrows
Glabella: prominence just above the nasal bones, between the medial ends of the eyebrows
Frontal eminences: Gently rounded prominences at the upper border of the forehead
Frontal sinuses are also included in the frontal bone
Parietal bones (2)
Form the majority of the upper sides and top of the cranium
Parietal Bones
Temporal Bones
Temporal bones (2)
Form lower sides of the cranium
Area surrounding the ears
Squama
Upper flat portion, adjacent to the parietal bone
Temporal Bones
Petrous portion
Inferior portion includes the hearing canal and houses the ear ossicles (6)
Temporal Bone
Malleus (hammer): (2) articulates with the incus and is attached to the tympanic membrane (eardrum), from which vibrational sound pressure motion is passed
Incus (anvil): (2) middle ossicle that connects the malleus and stapes
Stapes (stirrup): (2) articulates with the incus and is attached to the membrane of the fenestra ovalis, or opening between the middle ear and the vestibule of the inner ear
It is the smallest bone in the body
Temporal Bone
Zygomatic process
Projection on the temporal bone which extends forward, anterior to the hearing canal, to unite with the cheek bone
Mastoid process
Prominent projection on the inferior part of the temporal bone, just behind the ear
External auditory meatus
Tunnel in the temporal bone which extends medially from the external ear to the middle ear
Temporal Bone
Mandibular fossa
Depression on the temporal bone, anterior to the external auditory meatus, which articulates with the condyles of the lower jaw
Carotid canal
Passageway in the temporal bone through which the internal carotid artery passes in taking blood to the brain
Occipital Bone
Occipital bone (1)
Makes up lower back part of the cranium
Foramen magnum
Large opening in inferior portion through which the spinal cord passes to connect to the brain
Occipital Bone
Occipital condyles
Located on either side of the foramen magnum
Points of articulation with the top vertebrae of the spinal column
External occipital protuberance
Prominent tubercle on the posterior surface of the occipital bone
Sphenoid Bone
Sphenoid bone (1)
Bat shaped bone which helps make up the floor of the cranial cavity, back of the eye sockets, and part of the temple area
Sella turcica
Depression in the center of the superior portion of the sphenoid
Holds the pituitary gland
Sphenoid Bone
Ethmoid bone (1)
Irregular shaped bone which helps make up the floor of the cranial cavity, part of the eye socket, and the upper part of the nasal cavity
Ethmoid Bone
Ethmoid Bone
Cribriform plate
Flat superior surface of the ethmoid; involved in making up the floor of the cranial cavity
Contains several small holes to allow for passage of nerves into the nasal cavity
Contains a noticeable vertical projection on its superior portion called the crista galli (rooster’s comb)
Vertical or perpendicular plate is a thin, flat plate of bone which extends down into the nasal cavity to help make up the nasal septum
Ethmoid Bone
Paranasal sinuses within the Ethmoid bone
Group of four paired air-filled spaces that surround the nasal cavity
Maxillary sinuses are located under the eyes
Frontal sinuses are above the eyes
Ethmoidal sinuses are between the eyes
Sphenoidal sinuses are behind the eyes
Sinuses are named for the facial bones in which they are located
Transitional Features
Transitional features
Calvaria: top, domelike skullcap
Orbit: cavity or socket of the skull in which the eye and its appendages are situated
Orbit
Comprised of a portion of seven bones
Frontal bone
Lacrimal bone
Ethmoid bone
Zygomatic bone
Maxillary bone
Palatine bone
Sphenoid bone
Facial Bones
Face (14)
Nasal bones (2)
Small bones making up the bridge of the nose
Lacrimal bones (2)
Located in the anterior, medial portion of the eye sockets.
From the Latin for “tears”
Facial Bones
Vomer bone (1)
Located on the midline in the base of the nasal cavity
Helps form the nasal septum with the perpendicular plate of the ethmoid bone
Zygomatic bones (2)
Cheek bones
Also known as malar bones
Help form eye socket
Facial Bones
Maxillary bones (2)
Upper jaw bones, commonly referred to as maxilla
Help form eye socket and walls of the nasal cavity
Palatine process: horizontal portion of maxilla which forms the anterior portion of the roof of the mouth
Alveolar process: part of the maxilla into which the roots of the teeth are embedded
Maxillary sinuses (2): located below the cheeks, above the teeth and on the sides of the nose
Facial Bones
Palatine bones (2)
Smalls bones which help form the posterior part of the roof of the mouth
Origin of “palate”
Facial Bones
Inferior nasal conchae (2)
Described as bony ledge located on lateral wall of nasal cavity
Facial Bones
Mandible (1)
Lower jaw bone
Main horizontal and anterior portion known as the body
Mental eminence: inferior, anterior “tip of the chin”
Alveolar process: portion of mandible in which teeth are embedded
Facial Bones
Point at which the inferior line of the body turns upward is referred to as the angle
Vertical, posterior portion known as the ramus
Mandibular condyle fits into a depression in the temporal bone called the mandibular fossa to form the lower jaw joint
Hyoid Bone
Hyoid bone (1)
Horseshoe shaped bone located in the cervical region, just above the larynx
Does not directly articulate with any other bone
Serves as point of attachment for several muscles involved with movements in the tongue, mouth, and throat area
Vertebral Column
Vertebral column (26)
Bones of the spinal column are known as vertebrae
Function to provide strength, protection of the spinal cord, flexibility, and movement
Vertebral Column
Provide the main support structure of the body; the spine
Divided into 5 sections
Cervical
Thoracic
Lumbar
Sacrum
Coccyx
Vertebral Column
Cervical vertebrae
7 uppermost vertebrae
Located in the neck area
Referred to as C1-C7
Vertebral Column
C1 is the most superior vertebrae, also known as the atlas
Articulates with the occipital bone
Skull rests upon C1
C2 is the vertebrae below C1 and is known as the axis
Forms a special articulation with C1 that allows for a pivoting action
Allows the head to be turned from side to side
Vertebral Column
Thoracic vertebrae (12)
Inferior to the cervical vertebrae
Can be described as the upper back
Designated as T1-T12
Each thoracic vertebrae articulates with a pair of ribs
Vertebral Column
Lumbar vertebrae (5)
Inferior to the thoracic vertebrae
Designated L1-L5
Vertebral Column
Sacrum
Immediately inferior to L5
Results from the fusion of five separate vertebrae in a developing child
Articulates with the hip bones to form the pelvis
Vertebral Column
Coccyx
Most inferior vertebra
Often referred to as the “tail bone”
Results from the fusion of separate smaller vertebrae in a developing child
Sternum
Breastbone
Considered a single bone though originally 3 segments during development
Manubrium: superior segment
The suprasternal notch (jugular notch) is located in the middle at the upper broadest part of the manubrium
Joins with the body of the sternum, the clavicles and the cartilages of the first pair of ribs
Body: middle segment
Xiphoid process: inferior segment
Cartilaginous process (extension) of the inferior part of the sternum, which is usually ossified in the adult human
Ribs (12 pairs)
Series of slender curved bones articulated in pairs to the spine, protecting the thoracic cavity and its organs
Pairs are numbered 1-12, with pair 1 beginning just inferior to the clavicles
Posteriorly, each pair articulates with a spinal vertebrae
Divided into two categories
Ribs
True ribs: upper seven pairs. Called true ribs due to their articulation with sternum
False ribs: bottom five pairs. Called false ribs because they do not attach directly to the sternum
8-10 attach to the rib above via cartilage
11-12 have no anterior cartilage and are known as floating ribs
