6 The Axial Skeleton Power Point Lecture Slide

6 The Axial Skeleton Power. Point® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY EIGHTH EDITION ELAINE N. MARIEB Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Axial Skeleton § Forms the longitudinal part of the body § Divided into three parts § Skull § Vertebral column § Bony thorax Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Axial Skeleton Figure 5. 6 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Skull § Two sets of bones § Cranium – encloses & protects brain. § Facial bones – holds eyes in anterior position & allows the facial muscles to show emotions. § All but 1 of the bones are joined by sutures (interlocking, immovable joints) § Only the mandible is attached by a freely movable joint Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Frontal – forms forehead, brow bone, superior eye orbit § Parietal (2) – form most of the superior & lateral walls of the cranium § Meet in midline = sagittal suture § Meet frontal = coronal suture Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Temporal (2) – inferior to parietals & join to them at the squamous sutures § Important bone markings found here § External acoustic (auditory) meatus – canal leading to eardrum § Styloid process – sharp needle-like projection inferior to external auditory meatus (attachment point for many neck muscles and the hyoid bone) § Zygomatic process – thin bridge of bone that joins w/ the zygomatic (cheek) bone Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Important bone markings found in temporal bone § Mastoid process – rough projection posterior & inferior to the external auditory meatus § Full of air cavities (sinuses) § Attachment for some neck muscles § Close to middle ear & leads to ear infections § Jugular foramen – junction of occipital & temporal § Allows for passage of jugular vein § Largest vein of the head – drains the brain Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Important bone markings found in temporal bone § Internal auditory meatus – anterior to jugular foramen § Transmits cranial nerves 7 & 8 (facial & vestibulocochlear) § Carotid canal - anterior to jugular foramen § Carotid artery runs through it to brain Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Occipital – most posterior bone of cranium forming back wall & floor of the skull § Joins parietals anteriorly at lambdoid suture § Foramen magnum = large opening in base of the occipitals (spinal cord connects with the brain) § Lateral to the foramen magnum are rockerlike occipital condyles which rest on the 1 st vertebra Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Sphenoid – butterfly-shaped – spans the width of the skull and forms part of cranial cavity floor § Sella turcica “Turk’s saddle” = small depression on the midline of the sphenoid, holds the pituitary gland § Foramen ovale = large oval opening in line w/ the posterior end of the sella turcica (allows cranial nerve 5 (trigeminal) to pass to chewing muscles of mandible § Parts of the sphenoid form part of the eye orbits § § 2 important openings: 1. Optic canal (optic nerve) 2. Superior orbital fissure (cranial nerves 3, 4 & 6 – eye movements) Central part of the sphenoid riddled w/ air cavities = sphenoid sinuses Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Cranium § Ethmoid – irregularly shaped, anterior to sphenoid – forms roof of nasal cavity and medial walls of the orbits. § Crista galli “cock’s comb” = superior ethmoid surface projection – outermost brain covering attaches § Cribriform plates – holey areas on sides of crista galli= nerve fibers for smell pass through from nose § Superior & middle nasal conchae – extensions of the ethmoid – form part of lateral walls of nasal cavity & increase turbulence of air flowing Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Facial Bones § 14 bones § 12 paired, only the mandible and vomer are single Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Facial Bones § Maxillae (2) / maxillary bones – fused to form upper jaw § Upper teeth carried in the alveolar margin § Palatine processes- extensions that form the anterior part of the hard palate § Paranasal Sinuses – drain the nasal passages, lighten the skull bones, amplify sounds as we speak Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Facial Bones § Paranasal Sinuses § Hollow portions of bones surrounding the nasal cavity § Sinusitis (infection of sinuses) – can result in headache or upper jaw pain Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Facial Bones § Palatine(2) – posterior to palatine processes of maxillae – form posterior part of hard palate § cleft palate= failure of these to fuse § Zygomatic (2) – cheek bones – form portion of lateral walls of orbits § Lacrimal (2) – fingernail sized bones forming part of medial walls of orbits § Groove serves as passageway for tears Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Facial Bones § Nasal (2)– small rectangular bones – form bridge of nose – lower part of nose made of cartilage § Vomer “plow”(1) – median line of nasal cavity – forms most of the nasal septum § Inferior nasal conchae (2) – thin, curve bones projecting from lateral walls of the nasal cavity Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Facial Bones § Mandible (lower jaw) – largest, strongest bone of the face – joins temporal bones on each side of face, forming the only freely movable joints in the skull (find them!) § Horizontal part (body) forms the chin § 2 upright bars of bone (rami) extend from the body to connect the mandible with the temporal bone. § Lower teeth lie in alveolar margin Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Hyoid Bone § Not really part of the skull § Horseshoe shaped w/ a body and 2 pair of horns (cornua) § Closely related to mandible and temporal bones § Unique b/c it’s the only bone that does not articulate w/ any other bone Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Hyoid Bone § Suspended in mid–neck region 2 cm above the larynx, anchored by ligaments to the styloid processes of the temporal bones § Serves as a movable base for the tongue & attachment point for neck muscles (lower and raise larynx when we swallow & speak) Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Fetal Skull § Face small compared to size of cranium (skull is large compared to body length) § Adult skull is 1/8 total body length; newborn is 1/4 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Fetal Skull § Fontanels – fibrous membranes connecting the cranial bones § Baby’s pulse can be felt in these soft spots (explains their name “little fountain”) § Allow fetal skull to be compressed in birth process § Allow infants brain to grow § Largest fontanels are diamond shaped anterior shaped fontanel and smaller triangular shaped posterior § Convert to bone within 24 months after birth Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Skull Figure 5. 7 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Bones of the Skull Figure 5. 11 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Human Skull, Superior View Figure 5. 8 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Human Skull, Inferior View Figure 5. 9 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Vertebral Column § Serves as axial support of the body § Extends from the skull, which it supports, to the pelvis, where it transmits the weight of the body to the legs. § 26 irregular bones connected & reinforced by ligaments creating a flexible, curved structure. Figure 5. 14 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Vertebral Column § Spinal cord runs through central cavity, protected by vertebrae § Before birth = 33 separate vertebrae but 9 later fuse to form 2 composite bones – the sacrum (5 fused) & the coccyx (4 fused). Figure 5. 14 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Vertebral Column § Each vertebrae is given a name according to its location § 24 single vertebrae § 7 cervical vertebrae § 12 thoracic vertebrae § 5 lumbar vertebrae Figure 5. 14 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Vertebral Column § Vertebrae separated by pads of flexible fibrocartilage – intervertebral discs –cushion & absorb shocks while allowing flexibility. § Young person – discs = 90% water content – spongy & compressible. § As you age – water content decreases – harder & less compressible. § Can lead to herniated (“slipped”) discs. § Can also occur from exceptional twisting forces. § If disc presses on spinal cord or nerves = numbness & excruciating pain. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Vertebral Column § Disks & S-shaped curvature of spine prevent shock to head when we walk or run. § Primary curvatures § Thoracic & sacral regions § Present at birth § Secondary curvatures § Cervical curvature appears when baby begins to raise its head. § Lumbar curvature when baby begins to walk. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Vertebral Column § Abnormal spinal curvatures § Scoliosis - abnormal lateral curvature of the spine. § Kyphosis - Abnormal rearward curvature of the spine, resulting in hunchback. § Lordosis - Abnormal forward curvature of the spine in the lumbar region. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Vertebrae § All vertebrae have a similar structural pattern. § Body: disclike, weight bearing part facing anteriorly. § Vertebral arch: formed from the joining of all posterior extensions, the laminae & pedicles. § Vertebral foramen: canal through which the spinal cord passes. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Vertebrae § Transverse processes: 2 lateral projections from the vertebral arch. § Spinous process: single projection arising from the posterior aspect of the vertebral arch (fused laminae). § Superior & inferior articular processes: paired projections lateral to the vertebral foramen allowing a vertebra to form joints w/ adjacent vertebrae. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Structure of a Typical Vertebrae Figure 5. 16 Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Vertebrae Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Cervical Vertebrae § 7 (C 1 to C 7) – form the neck region. § First 2 – atlas & axis – are different because they perform functions not shared by any other cervical vertebrae. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Cervical Vertebrae § Atlas (C 1) has no body; the superior surfaces of its transverse processes contain large depressions that receive the occipital condyles of the skull; allows you to nod “yes. ” § Axis (C 2) has a large upright process (dens or odontoid process), which acts as a pivot point; allows you to indicate “no. ” Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Cervical Vertebrae § C 3 through C 7 are the smallest, lightest vertebrae § All transverse processes of cervical vertebrae only contain foramina through which vertebral arteries pass to the brain. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Thoracic Vertebrae § 12 with body somewhat heart shaped w/ 2 costal facets on each side, which receive the heads of the ribs. § Spinous process is long & hooks sharply downward (from the side looks like a giraffe’s head). Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Lumbar Vertebrae § 5 w/ massive blocklike bodies & short hatchet -shaped spinous processes (looks like moose head from side). § Sturdiest vertebrae – most stress here. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Sacrum § Formed by the fusion of 5 vertebrae. § Winglike alae articulaterally w/ the hipbones forming the sacroiliac joints. § Forms the posterior wall of the pelvis. § Median sacral crest roughens the posterior midline & are flanked by sacral foramina. § Vertebral canal continues inside the sacrum as the sacral canal – terminates in large inferior opening called the sacral hiatus. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Coccyx § Formed by fusion of 3 to 5 tiny, irregularly shaped vertebrae § This is the human “tailbone” – a remnant of the tail other vertebrate animals have. Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Regional Characteristics of Vertebrae Figure 5. 17 a–b Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Regional Characteristics of Vertebrae Figure 5. 17 c–d Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

The Bony Thorax § Made-up of three parts § Sternum § Ribs § Thoracic vertebrae Figure 5. 19 a Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Bony Thorax § Often called the “thoracic cage” b/c it forms a cone-shaped cage of slender bones around the organs of the thoracic cavity. § Sternum – “breastbone” § Flat bone that is a result of the fusion of 3 bones – the manubrium, body and xiphoid process § Attached to the first 7 pairs of ribs Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Sternum § Three important bony landmarks: 1. jugular notch (concave upper border of the manubrium) – can be felt easily – generally at level of T 3 2. sternal angle - where manubrium & body meet - formed at level of 2 nd ribs (reference to locate 2 nd intercostal space for listening to heart valves) 3. xiphisternal joint – body and xiphoid process fuse (level of T 9) § Sternal puncture used to get bone marrow tissue to diagnose certain blood diseases Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Bony Thorax § Ribs – 12 pair – form walls of bony thorax § Articulate w/ vertebral column posteriorly & curve downward toward anterior body surface. § True ribs = first 7 pair – attach directly to sternum by costal cartilage § False ribs = next 5 pair – attach indirectly to sternum or not at all (last 2 pair are called “floating ribs” b/c they are the ones not attached at all) Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings

Bony Thorax § Contrary to popular myth – men & women have the same number of ribs!! Copyright © 2006 Pearson Education, Inc. , publishing as Benjamin Cummings