Week 2 - Axial Skeleton PDF

Axial Skeleton HS 1300/2300B – SYSTEMIC APPROACH TO FUNCTIONAL HUMAN GROSS ANATOMY Dr. Kelsey Adams Week 2 – January 13, 2025 1  2 Learning O...

Axial Skeleton HS 1300/2300B – SYSTEMIC APPROACH TO FUNCTIONAL HUMAN GROSS ANATOMY Dr. Kelsey Adams Week 2 – January 13, 2025 1  2 Learning Objectives Identify the major components of the skeletal system and their functions. Identify the structures of the axial skeleton. Compare functions of the cranial and facial bones. Identify the bones, cavities and major landmarks of the skull. Describe the structure and components of the vertebral column. Identify features of the ribs and sternum. Understand the structure and function of the vertebrae. Identify axial skeleton abnormalities. Explain changes in the axial skeleton during growth and aging.  3 Overview Bones & Markings Skull Face Vertebral Column Thoracic Cage Axial Skeleton Disorders Skeleton Throughout Life  4 Bones  5 Bone Tissues Bone connective tissue Nervous tissue, blood connective tissue and articular cartilage Functional unit of bone: osteon Function of Bones 6  7 Classification of Bones Long bones: longer than wide; a shaft with ends Short bones: cube- shaped Flat bones: thin, flattened, curved Irregular bones: various shapes Figure 6.4, Human Anatomy  8 Gross Anatomy of Bones Compact bone: dense outer layer Spongy (cancellous) bone: internal network with trabeculae Spaces between trabeculae filled with marrow  9 Long Bone Structure Diaphysis: bone shaft Epiphyses: bone ends Metaphysis: between epiphysis and diaphysis, contains growth plate Medullary cavity: hollow, contains yellow marrow Blood vessels  10 Long Bone Membranes Periosteum: outer membrane, attachment for tendons/ligaments Sharpey’s fibers: anchor periosteum to bone Endosteum: inner lining; aids growth/remodeling  11 Figure 6.4, Human Anatomy  12 Structure of Short, Irregular, and Flat Bones Contain bone marrow but no cavity Diploë: internal spongy bone of flat bones  13 Bone Design and Stress Bone anatomy reflects stresses Compression and tension greatest at external surfaces Figure 6.6, Human Anatomy  Bone Markings 14 1. Projections for muscle attachment 2. Surfaces forming joints 3. Depressions and openings  15 Table 6.1, Human Anatomy Table 6.1, Human Anatomy  17 The Axial Skeleton  18 Skeletal System Bones, cartilage, joints and ligaments 206 bones 1. Axial skeleton (80): skull, vertebral column, thoracic cage 2. Appendicular skeleton (126): upper and lower limbs (next lecture)  19 Figure 7.1, Human Anatomy  20 The Skull  21 Skull Most complex bony Cranial Bones structure 22 bones Cranial (8) Facial (14) Facial Bones  Cranial Bones 22 Cranium divided into cranial vault and base Protect the brain Provide attachment sites for head and neck  23 Facial Bones Form facial framework Cavities for sight, taste, and smell Openings for air and food passage Hold teeth, anchor facial muscles Figure 7.2, Human Anatomy  Skull Regions Skull has bony ridges dividing it into: anterior, middle, and posterior fossae Brain sits within fossae in the cranial cavity Figure 7.2, Human Anatomy  25 Figure 7.2, Human Anatomy  26 Skull Cavities Middle and inner ear cavities: lateral cranial base Nasal cavity: behind nose Orbits: house eyeballs Paranasal sinuses: in bones around nasal cavity  27 Skull Openings ~85 named openings: foramina, canals, and fissures Passage for spinal cord, blood vessels, cranial nerves Foramen Magnum Optic Canal Superior and Inferior Orbital Fissure  28 Cranial Bones (8) Paired bones: Temporal bones (2) Parietal bones (2) Unpaired bones: Frontal bone Occipital bone Sphenoid bone Ethmoid bone  29 Parietal Bones and Sutures Form superior and lateral skull 4 sutures Coronal: parietal and frontal bones Squamous: parietal and temporal bones Sagittal: between left and right parietal bones Lambdoid: parietal and occipital bones  30 Sutural Bones Small, irregular bones in sutures Vary in shape, size, and location Not present in all individuals  31 Figure 7.4, Human Anatomy  32 Figure 7.4, Human Anatomy  33 Frontal Bone Forms forehead and roof of orbit Supraorbital margin: top of orbits Supraorbital foramen: passage for nerve and artery Glabella: smooth area between superciliary arches Frontal sinuses contributes to anterior cranial fossa 34  35 Occipital Bone Forms posterior cranium and cranial base Articulates with temporal and parietal bones Forms posterior cranial fossa Foramen magnum at base  36 Features of the Occipital Bone Occipital condyles: connect skull to spine for head movement Hypoglossal foramen: passage for tongue movement nerves External occipital protuberance: muscle attachment bump Nuchal lines: ridges for muscle attachment  37 Figure 7.5, Human Anatomy  38 Temporal Bones Inferior to parietal bones Inferolateral portion of the skull House inner ear structures Muscle attachment for chewing and head movement  39 Parts of the Temporal Bone Squamous: flat section forming skull side Tympanic: surrounds ear canal, protects ear structures Petrous: dense area housing inner ear for hearing and balance Figure 7.8, Human Anatomy  40 Mastoid Process Bony prominence behind ear Site for neck muscle attachment Contains air sinuses  41 Petrous Part of Temporal Bone Projects medially, contributes to cranial base Houses middle and inner ear cavities Contributes to middle and posterior cranial fossae  42 Foramina of the Temporal Bone Jugular foramen: between occipital and temporal bone, passage for internal Carotid canal jugular vein and cranial nerves (IX, X, XI) Carotid canal: internal carotid artery passes through Internal acoustic meatus: passage for cranial nerves (VII, VIII)  43 Figure 7.7, Human Anatomy  44 Figure 7.8, Human Anatomy  45 Sphenoid Bone Spans cranial floor width, resembles a bat Body and 3 pairs of processes 5 openings “Keystone" of the cranium  46 Sphenoid Bone Landmarks Body: central part Sella turcica: saddle-shaped area for pituitary gland Sphenoidal sinuses: air-filled spaces, lighten skull Greater wings: large extensions forming skull sides Lesser wings: smaller extensions forming part of orbit Pterygoid processes: projections for jaw muscle attachment  47 Figure 7.10, Human Anatomy  48 Sphenoid Bone Openings Optic canal: passage for optic nerve Superior orbital fissure: opening for 4 nerves controlling eye movement, vessels Foramen rotundum: opening for trigeminal nerve (sensation) Foramen ovale: opening for trigeminal nerve (motor) Foramen spinosum: passage for vessels supplying skull  49 Figure 7.10, Human Anatomy  50 Ethmoid Bone Between nasal and sphenoid bones Forms most of medial bony region between nasal cavity and orbits Contribute to nasal septum  51 Ethmoid Bone Landmarks Cribriform plate: superior surface, contains foramina for olfactory nerves (CN I) Crista galli: attachment for falx cerebri Perpendicular plate: forms superior part of nasal septum  52 Figure 7.12, Human Anatomy  53 Openings in the Ethmoid Bone Ethmoidal labyrinth: contains air cells and ethmoid sinuses that help lighten skull Nasal conchae: superior and middle, extend medially  54 Figure 7.11, Human Anatomy  55 The Face  56 Facial Bones Unpaired bones: mandible, vomer Paired bones: Maxillae Zygomatic bones Nasal bones Lacrimal bones Palatine bones Inferior nasal conchae  57 Mandible Largest and strongest facial bone Only movable skull bone Horizontal body Two upright rami  58 Major Landmarks Mandibular fossa: depression, temporal bone Mandibular foramen: opening, inner ramus surface Alveolar process: ridge containing tooth sockets Mental foramen: opening, anterior surface Condylar process: articulates with mandibular fossa Ramus: connects body to condylar and coronoid processes  59 Figure 7.13, Human Anatomy  60 Maxillary Bones Articulate with all facial bones except mandible Contain maxillary sinuses Form part of inferior orbital fissure “Keystone” bones of the face  61 Figure 7.13, Human Anatomy  62 Facial Bones Zygomatic bones: lateral wall of orbits Nasal bones: bridge of nose  63 Facial Bones Lacrimal bones: medial orbital walls Palatine bones: posterior part of hard palate  64 Facial Bones Vomer: inferior nasal septum Inferior nasal conchae: thin, curved bones form lateral walls of nasal cavity  65 Figure 7.7, Human Anatomy  66 Special Parts of the Skull Nasal cavity Paranasal sinuses Orbits Hyoid bone  67 Nasal Cavity Function Respiration Olfaction Resonance Sinus Connection  68 Figure 7.14, Human Anatomy  69 Figure 7.14, Human Anatomy  70 Paranasal Sinuses Air-filled sinuses within: Frontal bone Ethmoid bone Sphenoid bone Maxillary bones Lined by mucous membrane Lighten the skull  71 Figure 7.15, Human Anatomy  72 Orbits Eye protection Houses muscles, nerves, and vessels Supports eye movement and vision  73 Figure 7.16, Human Anatomy  74 Hyoid Bone Below mandible Only bone with no direct articulation Movable base for tongue Figure 7.17, Human Anatomy  75 Figure 7.6, Human Anatomy  76 Figure 7.6, Human Anatomy  77 The Vertebral Column  78 Vertebral Column 26 bones (adult) Supports trunk wight Protects spinal cord Attachment sites for neck and back muscles  79 Vertebral Column Regions 7 cervical vertebrae 12 thoracic vertebrae 5 lumbar vertebrae Sacrum—5 fused bones Coccyx—4 fused bones  80 Figure 7.18, Human Anatomy  81 Normal Curvatures of the Spine Cervical and lumbar: concave posteriorly Thoracic and sacral: convex posteriorly Curvatures increase resilience  82 Primary and Secondary Curvatures Primary curvatures: thoracic and sacral, present at birth Secondary curvatures: cervical and lumbar, develop with walking  83 Ligaments of the Spine Anterior longitudinal ligament Attaches to vertebrae and intervertebral discs Prevents hyperextension Posterior longitudinal ligament Narrow, weak Attaches to intervertebral discs  84 Figure 7.19, Human Anatomy  85 Figure 7.19, Human Anatomy  86 Intervertebral Discs Cushion-like pads between vertebrae Contain nucleus pulposus and anulus fibrosus  87 Intervertebral Disc Components Nucleus pulposus: gelatinous core, absorbs compression Anulus fibrosus: outer ligament rings, inner fibrocartilage, encloses the nucleus pulposus  88 General Vertebral Structure 1. Body: supports weight 2. Arch: protects spinal cord 3. Foramen: opening for spinal cord 4. Spinous/Transverse processes: muscle/ligament attachment 5. Articular processes: connect vertebrae 6. Intervertebral foramina: nerve passageways  89 Figure 7.20, Human Anatomy  90 Spinal Functions Movement between vertebrae Flexion and extension Lateral flexion Rotation in the long axis  91 Cervical Vertebrae C1–C7 Smallest and lightest C3–C7: wider body, short and bifid spinous process (except C7, vertebra prominens)  92 Features of Cervical Vertebrae Large, triangular foramen Transverse processes contain transverse foramina Superoposteriorly facing articular facets Table 7.2, Human Anatomy  93 Atlas (C1) No body or spinous process Supports skull Superior articular facets receive the occipital condyles Allows flexion/extension Nodding “yes”  94 Figure 7.22, Human Anatomy  95 Figure 7.22, Human Anatomy  96 Axis Body and spinous process Dens projects superiorly Fusion of atlas body with axis Pivot for rotation (shake head “no”)  97 Figure 7.22, Human Anatomy  98 Figure 7.21, Human Anatomy  99 Thoracic Vertebrae (T1–T12) Articulate with ribs, heart-shaped bodies T1: full facet for first rib T10–T12: single facet for ribs  100 Features of Thoracic Vertebrae Long spinous processes, point inferiorly Circular vertebral foramen Transverse processes articulate with rib tubercles Articular facets at superior/inferior edges Allows rotation, limits flexion/extension Table 7.2, Human Anatomy  101 Lumbar Vertebrae (L1–L5) Thick bodies Thin transverse processes Short, flat, spinous processes Triangular vertebral foramina Medially facing articular facets Allows flexion/extension, prevents rotation Table 7.2, Human Anatomy  102 Figure 7.21, Human Anatomy  103 Sacrum (S1–S5) Forms posterior pelvic wall 5 fused vertebrae Superiorly articulates with L5 Inferiorly articulates with coccyx  104 Sacrum Landmarks Sacral promontory: bulge of first sacral vertebra into pelvic cavity Ala: fused rib elements Superior articular processes: projections on upper sacrum Apex: inferior end of sacrum  105 Sacrum Landmarks Transverse ridges: horizontal ridges Facet of superior articular process: smooth, rounded surfaces Median sacral crest: vertical ridge, posterior midline Lateral sacral crests: vertical ridges, sides of median crest Auricular surface: lateral, ear-shaped  106 Figure 7.23, Human Anatomy  107 Sacral Foramina Anterior sacral foramina: passage for ventral rami of sacral nerves Posterior sacral foramina: passage for dorsal rami of sacral nerves Sacral canal: center of sacrum, continuation of vertebral canal, contains nerves and tissue Sacral hiatus: opening at inferior sacrum, above coccyx  108 Figure 7.23, Human Anatomy  109 Coccyx Tailbone Base: broad, upper part Apex: pointed, lower end Coccygeal Cornua: small projections extend from apex Body: main part, 3-5 fused vertebrae  110 The Thoracic Cage  111 Thoracic Cage Forms chest framework Thoracic vertebrae (posterior) Ribs (lateral) Sternum and costal cartilage (anterior) Protects thoracic organs Supports shoulder girdle and upper limbs Muscle attachment sites  112 Figure 7.24, Human Anatomy  113 Sternum Manubrium: superior, articulates with clavicles Body: bulk, notched for costal cartilage of ribs 2–7 Xiphoid process: inferior, ossifies around age 40  114 Landmarks of the Sternum Jugular notch: central indentation, superior border of manubrium Sternal angle: ridge where manubrium joins body Clavicular notch: shallow depressions for clavicles, superior aspect of manubrium  115 Ribs Attach to vertebral column posteriorly True ribs: top 7 pairs, attach to sternum via costal cartilage False ribs: bottom 5 pairs, including floating ribs (11–12)  116 Landmarks of the Ribs Head: round end, articulates with vertebral bodies Neck: short segment after head Tubercle: bump near neck-body junction Body (shaft): long, curved portion Costal angle: rib curves Costal groove: shallow groove along inner surface Sternal end: anterior end, articulates with sternum  117 Figure 7.25, Human Anatomy  118 Figure 7.25, Human Anatomy  119 Figure 7.25, Human Anatomy  120 Disorders of the Axial Skeleton  121 Common Conditions Cleft palate: congenital disorder, failure of palate halves to fuse medially Stenosis of lumbar spine: narrowing of vertebral canal, compresses spinal nerve roots  122 Abnormal Spinal Curvatures Kyphosis: exaggerated thoracic curvature Lordosis: accentuated lumbar curvature; “swayback” Scoliosis: abnormal lateral curvature  123 The Axial Skeleton Throughout Life  124 Ossification Membrane bones ossify in second month of development Bone tissue grows outward from ossification centers Fontanelles: unossified membrane remnants Figure 7.28, Human Anatomy  125 The Skeleton Throughout Life Skeleton grows until 18–21 years Children/adolescents: bone formation exceeds reabsorption Young adults: formation and reabsorption balanced  126 Aging of the Axial Skeleton Reabsorption predominates, bone mass declines Intervertebral discs lose water content Height loss common by age 55 Thorax becomes more rigid  127 Summary Axial skeleton forms the central framework of the body Provides support and protection to vital organs Includes skull, vertebral column, and rib cage Aging leads to bone changes and loss of bone density