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Lecture 5

BIOB33 - Lecture 5.doc

5 Pages

Biological Sciences
Course Code
Connie Soros

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BIOB33 – Lecture 5 Prof’s Speech - Purple Textbook Material - Orange The Skeletal System: Axial &Appendicular Divisions (based on chapters 6, 7 and 8) Skeletal System: Introduction • The skeleton is divided into 2 portions: the axial skeleton and the appendicular skeleton o It is a rigid framework of 206 bones , muscles and organs are attached by tendons and ligaments  300+ bones in in child skeleton, but bones fuse together o Bones act as levers (with joints acting as pivots) when muscles contract and move body The Axial Skeleton: - composed of bones along the central axis of the body – 80 bones • Divided into three regions: o Skull – brain case, protects the brain o Vertebral column  Pelvic bones protect the urinary tract and reproductive organs o Thoracic cage - Ribs protect the lungs and heart • Functions of the axial skeleton: o Framework that supports and protects organs in the dorsal and ventral body cavities o Protects special sense organs for taste, smell, hearing, balance, and vision o Attachment sites for muscles that: o Adjust the posture of the head, neck, and trunk o Move the thoracic cage for respiration o Stabilize the appendicular skeleton The Skull andAssociated Bones • Cranial and Facial Subdivisions of the Skull • The skull consists of o Face: 14 individual bones o Cranium: 8 individual bones o Associated bones: 7 individual bones (auditory ossicles – 3 per ear and hyoid bone) • Cranial bones – form cranium, encase and protect brain (8 bones) o Frontal bone – (1) forehead, roof of orbits o Parietal bones – (2) either side of the top of head o Temporal bones - (2) temples on either side of the head, protect sense organs of ear, extensive area for attachment of muscles that close the jaw and move the head  Protects tiny ear bones  Many muscles attach here  Mandibular joint is associated – top of jaw does not move, bottom jaw to stop moving when touches top jaw o Occipital bone – (1) back of head, foramen (opening) magnum connects cranial cavity with spinal cavity  Spinal cord passes through foramen magnum o Sphenoid bone – (1) butterfly shaped, keystone of skull, unites cranial and facial bones and base of cranium  Anterior to occipital bone o Ethmoid bone – (1) between obits/walls, floor of cranium, part of nasal cavity and nasal septum, part of nasal conchae involved with movement of air through sinouses  Separates the nasal cavity  3 nasal conchae create turbulence, which slows the air on its path to the trachea • Facial bones – form bone framework of oral cavity and jaw (14 bones), protect sensory organs o Nasal bones - (2) base of nose, cartilage forms the flexible portion  Cartilage provides much more elasticity and movement o Lacrimal bones – (2) (lacrima =tear), encloses tear duct and drains tears into nasal cavity  Tears go into the nose, nose runs when crying o Vomer - (1) means plowshare (looks like part of a plow from the front), inferior part of nasal septum  Looks like vertical line from front view o Maxilla – (2) the largest of the facial bones, together form the upper jaw, articulate with all other facial bones except mandible, oral margins form the alveolar processes that contain the upper teeth, left and right maxilla  Teeth attach to alveolar processes o Mandible – (1) forms the entire lower jaw, teeth are supported by the mandibular body, articulates with the temporal bone (tempomandibular joint) for jaw movements when talking or eating, high mobility but makes it easy to dislocate the jaw o Zygomatic bones – (2) cheek bones o Inferior Nasal Conchae – (2) one on each side of nasal septum, along with the nasal conchae of the ethmoid bone, they create turbulence in inhaled air (slows air movement and provides additional time for warming, humidification and dust removal before air reaches more delicate portions of the respiratory tract)  Superior and middle nasal concha are part of the ethmoid bone, inferior nasal conchae is a separate bone o Palatine bones – (2) form inferior portions of the hard palate, part of nasal cavity and eye orbit, extends back into the throat area • Associated Bones o Auditory ossicles – 6 bones in middle ear (ear bones), smallest bones in the body, transmit sound impulses; 2 malleus, 2 incus, 2 stapes (1 of each per ear) o Hyoid Bone – only bone that does not articulate with any other bone, above the larynx (voice box) below mandible (jawbone) supports the tongue, aids in swallowing The Vertebral Column • The adult vertebral column is made up of 26 bones: o 24 vertebrae o 7 cervical vertebrae – cervical curve o 12 thoracic vertebrae – thoracic curve o 5 lumbar vertebrae – lumbar curve o 1 sacrum (5 fused vertebrae) – sacral curve o 1 coccyx (3-5 fused vertebrae) – tailbone o These curves, along with muscle attachment to the various vertebral processes, help to maintain balance - Fusion of different bones happens at different ages • Functions of the vertebral column o Encloses and protects the spinal cord o Supports the skull o Supports the weight of the head, neck, and trunk o Transfers weight
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