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Overview of the Skeleton & The Axial Skeleton

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1 Overview of the Skeleton & The Axial Skeleton
Ex. 9 & 10 Overview of the Skeleton & The Axial Skeleton

2 Important figures & quiz knowledge
All figures (except 10.9) and tables are important to know & understand Review sheet ex. problems are important to next week’s quiz Probably will use a diagram from the review sheet ex. problems (either Ex. 9 or 10) on the quiz Need to know sheets


4 Bone markings Know primary bone marking names & descriptions
Be able to use bone markings to ID disarticulated bones Be able to use bone markings to understand articulation morphology Table 9.1, pg. 113

5 Classification of bones
Two basic kinds of osseous tissue (differ in their texture): Compact bone – smooth and homogeneous. Spongy bone/cancellous bone – composed of small trabeculae (bars) of bone and lots of open space. Further classification (based on gross anatomy): Long bones – Bones are much longer then they are wide.  In general consists of a shaft with heads at either end.  Composed predominantly of compact bone. Ex.:  Femur and bones of the fingers – phalanges.  Short bones – cube shaped.  Contain more spongy bone than compact bone.  Ex.: Tarsals and carpals. Flat bones – thin, with two layers of compact bone with a layer of spongy bone in between them.  Many are curved. Ex.: bones of the skull. Irregular bones – bones that do not fall into one of the preceding categories. Ex.: vertebrae. Sesamoid bones – special types of short bones formed in tendons.  Ex.:  Patellas – kneecaps. Wormian/ Sutural bones – tiny bones between cranial bones. Except for patellas, the Sesamiod bones and Wormian bones are not included in the 206 bone count because they vary in number and location in different individuals.


7 Bone markings Bone Markings Two categories:
Reveal where bones form joints with another bones, where muscles, tendons, and ligaments were attached, and where blood vessels and nerves passed Two categories: Projections/ processes that grow out from the bone and serve as sites of muscle attachment or help form joints Depressions /cavities are indentations or openings in bones that serve as conduits for nerves and blood vessels Table 9.1; page 113 Projections that are sites of muscle and ligament attachment: Tuberosity – Large rounded projection that may be roughened Crest – Narrow, usually prominent, ridge of bone Trochanter – Very large, blunt, irregularly shaped process Line – Narrow ridge of bone that is less prominent than a crest Tubercle – Small rounded process Epicondyle – Raised area on or above a condyle Spine – Sharp, slender, often pointed projection Process – Prominence or projection Processes that help to form joints: Head – Bony expansion carried on a narrow neck Facet – Smooth, nearly flat articular surface Condyle – Rounded articular projection Ramus – Armlike bar of a bone Cavities:             Antrum – Chamber within a bone             Sinus – Space/cavity within a bone, filled with air and lined with mucous membrane Depressions and openings that allow blood vessels and nerves to pass: Meatus – Canal-like passageway Fossa – Shallow, basinlike depression in a bone, often serving as an articular surface Groove – Furrow Fissure – Narrow, slitlike opening Foramen – Round or oval opening through a bone

8 Gross anatomy of long bone
Major features, figure 9.3, page 115 Diaphysis – shaft Periosteum – fibrous membrane covering.  Blood vessels and nerves travel through to invade the bone Perforating (Sharpey’s) fibers – fibers of the periosteum the penetrate into the bone Perforating (Volkmann's) canals – run into compact bone and marrow cavity from the periosteum, at the right angles of the shaft.  Complete the communication pathway between the bone interior and its external surface. Cells: Osteoblasts – bone – forming cells Osteoclasts – bone – destroying cells Shaft: Medullary cavity – central cavity of the shaft Yellow marrow - adipose tissue Red marrow – forms blood cells Found in Marrow cavities in infant In adult occupies spaces b/n trabeculae of spongy bone, to the interior of the epiphyses Endosteum – lines inside of the shaft, trabeculae of spongy bone, and canals of compact bone Contains osteoblasts and osteoclasts Epiphysis – the end of long bone.  Thin layer of compact bone with a layer of spongy bone in between. Articular cartilage – covers epiphyseal surface in place of the periosteum Glassy hyaline cartilage provides a smooth surface to prevent friction at joint surfaces Epiphyseal plate – thin area of hyaline cartilage that provides for longitudinal growth of the bone during youth Epiphyseal lines – remnants of epipyseal plate, ones the bone has stopped growing




12 Histology Osteon /Haversian system – central canal and all the concentric lamellae surrounding it Central (Haversian) canal – runs parallel to the long axis of the bone and carries blood vessels nerves, and lymph vessels through the body matrix Osteocytes – mature bone cells in lacunae (chambers), arranged in concentric circles (circumferential lamellae) around the central canal Lamellae – one of the tubular layers of bone surrounding the central canal in an osteon Interstitial lamellae – remnants of circumferential lamellae that have been broken down due to bone remodeling Canaliculi – tiny canals radiating outward from a central canal to the lacunae of the 1st Lamella and then form lamella to lamella Form dense transportation network through the hard bone matrix, connecting all living cells of the osteon to the nutrient supply Allow each cell to make what it needs for nourishment and to pass along the excess to the next osteocyte


14 Cartilages of skeleton
Perichondrium – dense connective tissue, surrounding cartilage Chondrocytes and chondroblasts are responsible for the cartilage growth and repair Acts like a girdle to resists distortion, when cartilage is subjected to pressure Location and Basic Structure Articular cartilages – cover the bone ends at movable joints Costal cartilges – connect ribs to the sternum (breast bone) Laryngeal cartilages – constructs larynx (voice box) Tracheal and bronchial cartilages – reinforce other passageways of the respiratory system Nasal cartilages – support external nose Intervertebral discs – separate and cushion bones of the spine (vertebrae) External ear cartilage – cartilage that support external ear Classification of cartilage (Chapter 6, page 78-9) Matrix – non-living material secreted by chondrocytes, containing jelly like ground substance and fibers Hyaline cartilage – most of the skeletal cartilages Only collagen fibers are present in the matrix Provides sturdy support with some resilience Elastic cartilage – More elastic fibers More flexible Cartilages of external ear and epiglottis Fibrocartilage – two rows of chondrocytes alternating with rows of thick collagen fibers Found where hyaline cartilage joins tendon or ligament Has a great tensile strength and can withstand heavy compression Constructs inervertebral discs and the cartilage within the knee joint



17 Divisions of the skeleton & skull
Subdivisions of skeleton Axial skeleton – bones that lie around the body's center of gravity Appendicular skeleton – bones of the limbs/ appendages 28 skull bones (8 cranial, 14 facial, and 6 ear bones) Cranium – encloses and protects brain tissue Facial bones – present eye in an anterior portion and form the base for the facial muscles All facial bones except for mandible (lower jawbone) join the maxilla (upper jaw bone) Sutures – interlocking joint, joins most skull bones (except TMJ) Notes from Chapter 12: At birth the human body has about 375 bones By adulthood, some of the bones have fused together to give us a total of 206 bones in our body Fontanels – fibrous membranes Indentations between the bones of the fetal skull These will ossify as fetus ages (20-22 month).  Allow the fetal skull to be compressed slightly during birth, and allow brain growth during late fetal life.

18 Skull: cranium The Cranium: Eight large, flat (mostly) bones. All single except for Parietals and Temporals, which come in pairs. Frontal Bone – anterior portion of the cranium.  Forms forehead, superior part of the orbit, and a floor of anterior cranial fossa Supraorbital foramen (notch) – opening above each orbit allowing blood vessels and nerves to pass  Parietal Bone (2) – Posterior to the frontal bone, forming sides of the cranium Sagittal suture – midline articulation point of the two parietal bones Coronal suture – point of interaction of parietals with frontal bones Temporal Bone (2) – Inferior to parietal bone on lateral skull Four major parts: Squamous region – adjacent to the parietals Zygomatic process – bridgelike projection joining the zygomatic bone (cheekbone) anteriorly, forming zygomatic arch Mandibular fossa – rounded depression on the inferior surface of the zygomatic process, point where mandibular condyle of the mandible (lower jaw) joins the cranium Tympanic region – surrounds the external ear opening. External auditory meatus – canal leading to eardrum and middle ear Styloid process – needlelike projection inferior to external auditory meatus; attachment point for muscles and ligaments of the neck Mastoid region – area posterior to the ear Mastoid process – rough projection inferior and posterior to external auditory meatus;  attachment site for muscles Petrous region – forms the lateral portion of the skull base Occipital Bone – most posterior bone of the cranium, forms floor and back wall Foramen magnum – large opening in base of occipital, which allows the spinal cord to join with the brain Occipital condyles – rounded projections lateral to the foramen magnum that articulate with the facets of the 1st cervical vertebrae – atlas Sphenoid Bone – bat-shaped bone forming the anterior plateau of the middle cranial fossa across the width of the skull Ethmoid Bone – irregularly-shaped bone anterior to the sphenoid; forms roof of nasal cavity, upper nasal septum & part of medial orbit walls

19 Skull: facial bones Fourteen facial bones; all paired except for Mandible and Vomer Mandible – lower jaw bone, articulates with the temporal bones in the freely movable joints of the skull Mandibular ramus – vertical extension of the body in either side Mandibular condyle – articulation point of the mandible with the mandibular fossa of the temporal bone Coronoid process – protruding anterior portion of the ramus, site of muscle attachment Mental foramen – prominent opening on the body (lateral to midline) that transmits the mental blood vessels and nerve to the lower jaw Maxillae – two bones fused in a median suture, form upper jaw-bone and part of the orbits Infraorbital  foramen – large bilateral opening located posterior to the central incisor tooth of the maxilla and piercing the hard palate; transmits the nasopalatine arteries and blood vessels Lacrimal – fingernail-sized pair of bones forming part of medial orbit walls Palatine – paired bones forming posterior hard palate & part of orbit Zygomatic – lateral to the maxilla, forms cheekbone, and part of the lateral orbit Nasal – small rectangular bones forming the bridge of the nose Vomer – blade-shaped bone forming posterior & inferior nasal septum Inferior Nasal Conchae (turbinates) – thin, curving bones protuding from lateral nasal cavity walls







26 Located in the throat above the larynx, where it serves as a point of attachment of many tongue and neck muscles

27 Bony thorax Sternum (breast bone): 3 fused bones
Manubrium Body Xiphoid process Ribs: walls of thoracic cage Articulate posteriorly with the vertebral column via their heads and tubercles Curve downward and toward anterior body surface. 12 pairs 7 pairs of true (vertebrosternal) ribs: attach directly to the sternum by their own costal cartilage 5 pairs of false ribs: attach indirectly or lack sternal attachment 3 vertebrochondral: indirectly attach to sternum via costal cartilage of rib 7 2 floating (vertebral) ribs: no sternal attachment

28 7, 12, 5: “Come in at 7, lunch at 12, leave at 5.”

29 Vertebral column 26 vertebrae
7 cervical or neck 12 thoracic 5 lumbar or loins Sacrum: 5 fused vertebrae Coccyx: vestigial tail; 4 fused vertebrae Expends from the skull to the pelvis, forms the body’s major axial support Surrounds and protects spinal cord while allowing the spinal nerves to issue from the cods via openings between adjacent vertebrae Intervertebral discs – fibrocartilage pads with fluid components, separate and cushion the vertebrae and absorb shocks S-shape Increases strength of the back Helps vertebral column absorb the shock of walking upright Helps to maintain balance Structure of a Typical Vertebra Centrum – rounded central portion, which faces anteriorly in the human vertebral column Vertebral arch – composed of pedicles, laminae, and spinous process, it represents he junction of all posterior extensions from the vertebral body Vertebral (spinal) foramen – opening enclosed by the body and vertebral arch; a channel for the spinal cord Transverse processes – two lateral projections from the vertebral arch Spinous process – single medial and posterior projection from the vertebral arch Superior and inferior articular processes – paired projections lateral to the vertebral foramen that allows contact with adjacent vertebrae Intervertebral foramina – right and left pedicles have notches on their inferior and superior surfaces that create openings , for spinal nerves to leave the spinal cord between adjacent vertebrae

30 Rule of Thumb: Body gets thicker as proceeding down spine to support weight – so do the vertebrae

31 Ways to distinguish Note on atlas and axis Size # of foramina (1 or 3)
Size & direction of processes Note on atlas and axis “Atlas holds up the world” No spinous process “Atlas spins on the axis” Funny shape to spinous process Dens is the pivot that atlas sits on







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