BIOL1410 Lecture #8 - Axial Skeleton PDF

Lecture #8 The Axial Skeleton  Defining Some Terms Lateral: to the side Anterior (ventral): to the front Posterior (dorsal): to the back Superior: to the top Inferior: to the bottom Articulate: attach to Proximal: near to Distal: far from Medial: to the middle...

Lecture #8 The Axial Skeleton  Defining Some Terms Lateral: to the side Anterior (ventral): to the front Posterior (dorsal): to the back Superior: to the top Inferior: to the bottom Articulate: attach to Proximal: near to Distal: far from Medial: to the middle  The Skeleton The skeletal system is divided into two components: 1. Axial skeleton 2. Appendicular skeleton 1. Axial skeleton: This is the skeletal system that can be found down the midline of the body Composed of 80 bones including: a. The skull b. The hyoid bone c. The vertebral column d. The thoracic cage: composed of the sternum and the ribs  The Axial Skeleton: Skull 1. Axial skeleton: a. The skull: Consists of: i. The cranium Encages the brain Consists of 8 bones that function to protect the brain 1 frontal bone 2 parietal bones 2 temporal bones 1 occipital bone 1 sphenoid bone 1 ethmoid bone: superior and middle nasal conchae  The Axial Skeleton: Skull 1. Axial skeleton: a. The skull: Consists of: ii. Facial bones: 14 bones in total 2 nasal bones 2 maxillae: form the upper jaw 2 zygomatic bones: form the eye socket and the cheekbone 2 lacrimal bones: form the sides of the nose and the remaining portion of the eye socket 2 palatine bones: in the pallet 2 inferior nasal conchae 1 vomer: found behind the pallet 1 mandible: forms the lower jaw  The Axial Skeleton: Skull 1. Axial skeleton: a. The skull: Consists of: iii. Auditory Ossicles: Found in the middle ear The smallest bones found in the body Consists of: 2 malleus 2 incus 2 stapes  The Axial Skeleton: Hyoid Bone 1. Axial skeleton: b. The hyoid bone: This bone forms no articulations with bone Functions to attach muscles of the tongue, neck and pharynx  The Axial Skeleton: The Vertebral Column 1. Axial skeleton: c. The vertebral column: Also called the spinal column Each vertebra of the spinal column consists of: i. Body: thick and located on the anterior end ii. Lamina iii. Pedicle iv. Vertebral arch v. Vertebral foramen: line up for each individual vertebra forming a canal through which the spinal cord passes vi. Spinous process Serve as attachment sites for vii. Two transverse processes muscles and ligaments viii. Superior and inferior articular processes: contain smooth surfaces formed from hyaline cartilageà called facets Serve as attachment sites for vertebra above and vertebra below  The Axial Skeleton: The Vertebral Column There are five regions of the vertebral column: 1. Cervical 2. Thoracic 3. Lumbar 4. Sacral 5. Coccyx  The Vertebral Column: Cervical Region There are 7 vertebrae found within the cervical region: C1-C7 These are the smallest and the lightest weight vertebrae C1 is the atlas Has no body Has no spinous process The absence of these joints allow you to move your head up and down in a yes motion Articulates superiorly with the occipital condyle  The Vertebral Column: Cervical Region C2 is the axis Contains all of the typical vertebral components (body/spinous process) Not as specialized as the atlas Contains a knoblike process called the dens (odontoid process) that projects superiorly from the body of the vertebrae Acts as a pivot for atlas rotation allowing you to move your head in a ‘no’ motion C3 to C7 Distinguishing feature found on all of these vertebrae is the transverse foramina Opening found in the transverse process where the vertebral arteries pass in order to service the brain  The Vertebral Column: Thoracic Region The thoracic region contains 12 vertebrae labelled T1-T12 These articulate posteriorly with the ribs The thoracic vertebrae increase in size from the first to the last The distinguishing feature it the articular facet Used for rib articulation  The Vertebral Column: Lumbar Region This region has 5 vertebrae: L1-L5 These vertebrae function to support the body’s weight Commonly referred to as the ‘small of the back’ Contain a large, very thick body Processes are very heavy and rectangular The Vertebral Column: The Sacrum The sacrum consists of five fused vertebrae Articulates with the ilium, a part of the appendicular skeleton, specifically the pelvis Also articulates with the 5th lumbar vertebra superiorly Contain intervertebral foramina Exit sites for the spinal nerves The Vertebral Column: The Coccyx The coccyx consists of 3-5, but usually 4 fused vertebrae Known as the tailbone Generally useless  Spinal Curvature Normal curvature of the vertebral column: The cervical and the lumbar sections are curved concave posteriorly The thoracic and the sacral sections are curved convex posteriorly Abnormal curvature of the vertebral column: 1. Scoliosis: The spinal column curve laterally As though you continually carried a heavy bag on the same shoulder 2. Kyphosis: Hunchback Caused by an exaggerated thoracic curve which can be caused by osteoporosis 3. Lordosis: Swayback Caused by an exaggerated lumbar curve which can be caused by pregnancy or pot bellies  The Axial Skeleton: The Thoracic Cage 1. The axial skeleton: d. The thoracic cage Consists of the sternum and the ribs i. The sternum: The breast bone The manubrium is superior The body is the middle portion The xiphoid process is inferior  The Axial Skeleton: The Thoracic Cage 1. The axial skeleton: d. The thoracic cage ii. The ribs There are 12 pair of ribs They articulate posteriorly with thoracic vertebrae There are true ribs and false ribs a. True ribs: attach directly to the sternum via costal cartilage (hyaline cartilage)à there are 7 pair of true ribs b. False ribs: attach either indirectly to the sternum or not at all Pairs 8-10 attach indirectly to the sternum via costal cartilage Pairs 11 and 12 are not attached and are embedded in muscleà called floating ribs