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The Axial Skeleton (contd.) & The Appendicular Skeleton Human Anatomy Sonya Schuh-Huerta, Ph.D. The Vertebral Column • Formed from 26 bones in the adult • Transmits weight of trunk to lower limbs • Surrounds & protects spinal cord The Vertebral Column • Serves as attachment sites for muscles of the neck and back • Held in place by ligaments – Anterior & posterior longitudinal ligaments – Ligamentum flavum The Vertebral Column C1 2 3 4 5 6 7 T1 2 3 4 Cervical curvature (concave) 7 vertebrae, C1 – C7 Spinous process Transverse processes Thoracic curvature (convex) 12 vertebrae, T1 – T12 5 6 7 8 9 10 11 12 L1 2 3 4 5 Anterior view Intervertebral discs Intervertebral foramen Lumbar curvature (concave) 5 vertebrae, L1 – L5 Sacral curvature (convex) 5 fused vertebrae sacrum Coccyx 4 fused vertebrae Right lateral view Regions & Normal Curvatures • The Vertebral column has 5 major regions – 7 cervical vertebrae of the neck region – 12 thoracic vertebrae – 5 lumbar vertebrae – Sacrum five fused bones • Inferior to lumbar vertebrae – Coccyx inferior to sacrum Regions & Normal Curvatures • Curvatures of the spine – Cervical & lumbar curvatures • Concave posteriorly – Thoracic & sacral curvatures • Convex posteriorly Regions & Normal Curvatures • Curvatures increase resilience of spine • Thoracic & sacral curvatures – Primary curvatures • Present at birth • Lumbar curvature – Develops when baby begins to walk (~1 year) Ligaments of the Spine • Major supporting ligaments – Anterior longitudinal ligament • Attaches to bony vertebrae & intervertebral discs • Prevents hyperextension – Posterior longitudinal ligament • Narrow & relatively weak • Attaches to intervertebral discs Ligaments of the Spine Supraspinous ligament Transverse process Sectioned spinous process Intervertebral disc Anterior longitudinal ligament Ligamentum flavum Intervertebral foramen Posterior longitudinal ligament Interspinous ligament Anulus fibrosus Nucleus pulposus Inferior articular process (a) Sectioned body of vertebra Median section of three vertebrae, illustrating the composition of the discs and the ligaments Posterior longitudinal ligament Anterior longitudinal ligament Body of a vertebra Intervertebral disc (b) Anterior view of part of the spinal column Intervertebral Discs • Are cushion-like pads between vertebrae – Composed of: • Nucleus pulposus • Anulus fibrosus Intervertebral Discs • Nucleus pulposus • derived from notocord – Gelatinous inner sphere – Absorbs compressive stresses • Annulus fibrosus – Outer rings formed of ligament – Inner rings formed of fibrocartilage – Surround the nucleus pulposus Intervertebral Disc Vertebral spinous process (posterior aspect of vertebra) Spinal cord Spinal nerve root Nucleus pulposus of intact disc Transverse process Herniated portion of disc Anulus fibrosus of disc Nucleus pulposus of disc Herniated nucleus pulposus (c) Superior view of a herniated intervertebral disc (d) MRI of lumbar region of vertebral column in sagittal section showing normal & herniated discs General Structure of Vertebrae Posterior Lamina Spinous process Transverse process Vertebral arch Superior articular process and facet Pedicle Vertebral foramen Body (centrum) Anterior General Structure of Vertebrae • Common structures to all regions – Body – Vertebral arch – Vertebral foramen – Spinous process – Transverse process – Superior & inferior articular processes – Intervertebral foramina Movement of the Vertebrae • Specific regions of the spine perform specific functions • Types of movement that occur between vertebrae – Flexion & extension – Lateral flexion – Rotation in the long axis Cervical Vertebrae • 7 cervical vertebrae (C1–C7) smallest & lightest vertebrae • C3–C7 are typical cervical vertebrae – Body is wider laterally – Spinous processes are short & bifid (except C7) – Vertebral foramen are large & triangular – Transverse processes contain transverse foramina – Superior articular facets face superoposteriorly Cervical Vertebrae Cervical Vertebrae Dens of axis Transverse ligament of atlas C1 (atlas) C2 (axis) C3 Inferior articular process Bifid spinous process Transverse processes C7 (vertebra prominens) (a) Cervical vertebrae The Atlas • C1 is termed atlas • Lacks a body & spinous process • Supports the skull – Superior articular facets receive the occipital condyles • Allows flexion & extension of neck – Nodding the head “yes” The Atlas C1 Posterior Posterior tubercle Posterior arch Lateral masses Anterior arch Transverse foramen Superior articular facet Anterior tubercle (a) Superior view of atlas (C1) The Atlas C1 Posterior arch Transverse process Posterior Posterior tubercle Lateral masses Transverse foramen Facet for dens (b) Inferior view of atlas (C1) Inferior articular facet Anterior arch Anterior tubercle The Axis • Has a body & spinous process • Dens (odontoid process) projects superiorly – Formed from fusion of the body of the atlas with the axis – Acts as a pivot for rotation of the atlas & skull – Participates in rotating the head from side to side (‘nodding no’) The Axis C2 Posterior Inferior articular process Transverse process Dens (c) Superior view of axis (C2) Spinous process Lamina Pedicle Superior articular facet Body Thoracic Vertebrae (T1—T12) • All articulate with ribs • Have heart-shaped bodies from the superior view • Each side of the body of T1–T10 bears demifacts for articulation with ribs – T1 has a full facet for the first rib – T10–T12 only have a single facet Thoracic Vertebrae Thoracic Vertebrae • Spinous processes are long & point inferiorly • Vertebral foramen are circular • Transverse processes articulate with tubercles of ribs • Superior articular facets point posteriorly • Inferior articular processes point anteriorly – Allows rotation & prevents flexion and extension Lumbar Vertebrae (L1—L5) • Bodies are thick & robust • Transverse processes are thin & tapered • Spinous processes are thick, blunt, & point posteriorly • Vertebral foramina are triangular • Superior & inferior articular facets directly medially • Allows flexion & extension rotation prevented Lumbar Vertebrae Lumbar Vertebrae Superior articular process Transverse process Body Intervertebral disc Inferior articular process Spinous process (c) Lumbar vertebrae Sacrum (S1—S5) • • • • • Shapes the posterior wall of pelvis Formed from 5 fused vertebrae Superior surface articulates with L5 Inferiorly articulates with coccyx Sacral promontory – Where the first sacral vertebrae bulges into pelvic cavity • Center of gravity is 1 cm posterior to sacral promontory • Ala develops from fused rib elements Sacrum • Sacral foramina – Ventral foramina • Passage for ventral rami of sacral spinal nerves – Dorsal foramina • Passage for dorsal rami of sacral spinal nerves Sacrum Body Sacral promontory Ala Sacral canal Body of first sacral vertebra Facet of superior articular process Auricular surface Transverse ridges (sites of vertebral fusion) Apex Median sacral crest Anterior Posterior sacral sacral foramina foramina Coccyx (a) Anterior view Coccyx (b) Posterior view Lateral sacral crest Sacral hiatus Coccyx • • • • Is the “tailbone” Formed from 3–5 fused vertebrae Offers only slight support to pelvic organs Easily injured The Thoracic Cage • Forms the framework of the chest • Components – Thoracic vertebrae – posteriorly – Ribs – laterally – Sternum and costal cartilage – anteriorly • Protects thoracic organs • Supports shoulder girdle and upper limbs • Provides attachment sites for muscles The Thoracic Cage Jugular notch Clavicular notch Manubrium Sternal angle Body Xiphisternal joint Xiphoid process True ribs (1–7 False ribs (8–12) Intercostal spaces L1 Vertebra Floating ribs (11, 12) (a) Skeleton of the thoracic cage, anterior view Costal cartilage Costal margin Sternum The Thoracic Cage T2 Jugular notch T3 T4 Sternal angle Heart T9 Xiphisternal joint (b) Midsagittal section through the thorax, showing the relationship of surface anatomical landmarks of the thorax to the vertebral column Sternum • Formed from three sections – Manubrium—superior section • Articulates with medial end of clavicles – Body—bulk of sternum • Sides are notched at articulations for costal cartilage of ribs 2–7 – Xiphoid process—inferior end of sternum • Ossifies around age 40 Sternum • Anatomical landmarks – Jugular notch • Central indentation at superior border of the manubrium – Sternal angle • A horizontal ridge where the manubrium joins the body – Xiphisternal joint • Where sternal body and xiphoid process fuse • Lies at the level of the 9th thoracic vertebra Ribs • All ribs attach to vertebral column posteriorly – True ribs - superior seven pairs of ribs • Attach to sternum by costal cartilage – False ribs—inferior five pairs of ribs – Ribs 11–12 are known as floating ribs Ribs Shaft Facets for articulation with vertebrae Junction with costal cartilage Head Costal groove Neck Articular facet on tubercle Costal angle (a) A typical rib (rib 6, right), posterior view Angle of rib Transverse costal facet (for tubercle of rib) Superior costal facet (for head of rib) Body of vertebra Head of rib Intervertebral disc Neck of rib Tubercle of rib Shaft Crosssection of rib Costal groove Sternum Costal cartilage (b) Vertebral and sternal articulations of a typical true rib Ribs Articular facet on tubercle of rib Spinous process Shaft Ligaments Neck of rib Head of rib Superior costal facet (for head of rib) Transverse costal facet (for tubercle of rib) Body of thoracic vertebra (c) Superior view of the articulation between a rib and a thoracic vertebra Disorders of the Axial Skeleton • Cleft palate – A common congenital disorder – Right & left halves of palate fail to fuse medially – Can involve entire palate & lip – minor to severe • Stenosis of the lumbar spine – Narrowing of the vertebral canal – Can compress roots of spinal nerves Disorders of the Axial Skeleton • Abnormal spinal curvatures – Scoliosis—an abnormal lateral curvature – Kyphosis—an exaggerated thoracic curvature – Lordosis—an accentuated lumbar curvature; “swayback” The Axial Skeleton Throughout Life • Membrane bones begin to ossify in second month of development • Bone tissue grows outward from ossification centers • Fontanels – Unossified remnants of membranes Fontanelles Frontal suture Frontal bone Ossification center Posterior fontanelle (a) Superior view Anterior fontanelle Parietal bone Occipital bone Fontanelles Parietal bone Frontal bone Ossification center Sphenoidal fontanelle Temporal bone (squamous portion) Posterior fontanelle Mastoid fontanelle Occipital bone (b) Lateral view The Axial Skeleton Throughout Life • Many bones of the face & skull form by intramembranous ossification • Endochondral bones of the skull are: – Occipital bone – Sphenoid – Ethmoid bones – Parts of the temporal bone The Axial Skeleton Throughout Life • Aging of the axial skeleton: – Water content of the intervertebral discs decreases – By age 55, loss of a few centimeters in height is common! – Thorax becomes more rigid – Bones lose mass with age The Appendicular Skeleton, Ch 8 (also to be used as Lab Guide) The Appendicular Skeleton • Pectoral girdle – Attaches the upper limbs to the trunk • Pelvic girdle – Attaches the lower limbs to the trunk • Upper & lower limbs differ in function – Share the same structural plan The Pectoral Girdle • Consists of the clavicle & scapula • Pectoral girdles do not quite encircle the body completely – Medial end of each clavicle articulates with the manubrium and first rib – Laterally the ends of the clavicles join the scapulae – Scapulae do not join each other or the axial skeleton The Pectoral Girdle • Provides attachment for many muscles that move the upper limb • Girdle is very light & upper limbs are mobile – Only clavicle articulates with the axial skeleton – Socket of the shoulder joint (glenoid cavity) is shallow • Good for flexibility, bad for stability Articulated Pectoral Girdle Acromioclavicular joint Clavicle Scapula (a) Articulated pectoral girdle Clavicles • Extend horizontally across the superior thorax • Sternal end articulates with the manubrium • Acromial end articulates with scapula Clavicles Sternal (medial) end Posterior Anterior Acromial (lateral) end (b) Right clavicle, superior view Acromial end Anterior Trapezoid line Posterior Sternal end Tuberosity for costoclavicular ligament (c) Right clavicle, inferior view Conoid tubercle Clavicles • Provide attachment for muscles • Hold the scapulae & arms laterally • Transmit compression forces from the upper limbs to the axial skeleton Scapulae • Lie on the dorsal surface of the rib cage • Located between ribs 2–7 • Have 3 borders – Superior – Medial (vertebral) – Lateral (axillary) • Have 3 angles – Lateral, superior, & inferior Structures of the Scapula Acromion Suprascapular notch Coracoid process Superior border Superior angle Glenoid cavity Lateral border Subscapular fossa Medial border (a) Right scapula, anterior aspect Inferior angle Structures of the Scapula Suprascapular notch Coracoid process Acromion Superior angle Supraspinous fossa Spine Glenoid cavity at lateral angle Infraspinous fossa Medial border (b) Right scapula, posterior aspect Lateral border The Upper Limb • 30 bones form each upper limb • Grouped into bones of the: – Arm – Forearm – Hand Arm • Region of the upper limb between the shoulder & elbow • Humerus – The only bone of the arm – Longest & strongest bone of the upper limb – Articulates with the scapula at the shoulder – Articulates with the radius & ulna at the elbow Arm • Humerus – Many structures of the humerus provide sites for muscle attachment – Other structures of the humerus provide articulation sites for other bones Structures of the Humerus of the Right Arm Greater tubercle Lesser tubercle Head of humerus Head of humerus Anatomical neck Anatomical neck Greater tubercle Surgical neck Intertubercular sulcus Radial groove Deltoid tuberosity Deltoid tuberosity Medial supracondylar ridge Lateral supracondylar ridge Radial fossa Capitulum Coronoid fossa Olecranon fossa Medial epicondyle Medial epicondyle Trochlea Trochlea (a) Anterior view Lateral epicondyle (b) Posterior view Structures of the Humerus of the Right Arm Humerus Coronoid fossa Capitulum Medial epicondyle Head of radius Radial tuberosity Radius (c) Anterior view at the elbow region Trochlea Coronoid process of ulna Radial notch Ulna Humerus Olecranon fossa Olecranon process Medial epicondyle Lateral epicondyle Head Neck Ulna (d) Posterior view of extended elbow Radius Forearm • Formed from the radius & ulna • Proximal ends articulate with the humerus • Distal ends articulate with carpals Forearm • Radius & ulna articulate with each other – At the proximal & distal radioulnar joints • The interosseous membrane – Interconnects radius & ulna • In anatomical position; the radius is lateral and the ulna is medial Ulna • Main bone responsible for forming the elbow joint with the humerus • Hinge joint allows forearm to bend on arm • Distal end is separated from carpals by fibrocartilage • Plays little to no role in hand movement The Radius & Ulna Radial notch of the ulna Head Neck Radial tuberosity Olecranon process Head of radius Trochlear notch Neck of radius Coronoid process Proximal radioulnar joint Interosseous membrane Ulna Radius Styloid process of radius (a) Anterior view Olecranon process Ulnar notch of the radius Head of ulna Distal radioulnar joint Styloid process of ulna Interosseous membrane Ulna Ulnar notch of the radius Radius Head of ulna Styloid process of ulna (b) Posterior view Styloid process of radius Radius & Ulna Olecranon process Trochlear notch View Coronoid process Radial notch (c) Proximal portion of ulna, lateral view Ulnar notch of radius Articulation for lunate Articulation for scaphoid Styloid process View Head of ulna Styloid process (d) Distal ends of the radius & ulna at the wrist Radius • Superior surface of the head of the radius articulates with the capitulum • Medially – the head of the radius articulates with the radial notch of the ulna • Contributes heavily to the wrist joint – Distal radius articulates with carpal bones – When radius moves, the hand moves with it Hand • Includes the following bones: – Carpus (carpals) wrist – Metacarpals palm – Phalanges fingers Carpus • Forms the true wrist the proximal region of the hand • Gliding movements occur between carpals • Composed of 8 marble-sized bones Carpus • Carpal bones – Are arranged in 2 irregular rows – Proximal row from lateral to medial: • Scaphoid, lunate, triquetral, & pisiform – Distal row from lateral to medial: • Trapezium, trapezoid, capitate, & hamate – A mnemonic to help remember carpals: • Sally Left The Party To Take Carmen Home! Bones of the Hand Phalanges Distal Middle Proximal Carpals Hamate Capitate Pisiform Triquetrum Lunate Ulna 5 4 3 2 Metacarpals Head Shaft Base Sesamoid bones 1 Carpals Trapezium Trapezoid Scaphoid Radius (a) Anterior view of right hand 1 2 3 4 5 Carpals Hamate Capitate Triquetrum Lunate Ulna (b) Posterior view of right hand Metacarpus • 5 metacarpals radiate distally from the wrist • Metacarpals form the palm – Numbered 1–5, beginning with the pollex (thumb) – Articulate proximally with the distal row of carpals – Articulate distally with the proximal phalanges Phalanges • Numbered 1–5, beginning with the pollex (thumb) • Except for the thumb, each finger has 3 phalanges – Proximal, middle, & distal Pelvic Girdle • Attaches lower limbs to the spine • Supports visceral organs • Attaches to the axial skeleton by strong ligaments • Acetabulum is a deep cup that holds the head of the femur – Lower limbs have less freedom of movement • Are more stable than the arm Bones of the Pelvic Girdle • Consists of paired hip bones (coxal bones) • Hip bones unite anteriorly with each other • Articulates posteriorly with the sacrum • Pelvic girdle a deep, basin-like structure • Formed by: – Coxal bones, sacrum, & coccyx Bones of the Pelvic Girdle Base of sacrum Iliac crest Iliac fossa llium Coxal bone (os coxae or hip bone) Pubis Sacroiliac joint Anterior superior iliac spine Sacral promontory Anterior inferior iliac spine Sacrum Coccyx Ischium Pelvic brim Acetabulum Pubic tubercle Pubic crest Pubic arch Pubic symphysis The Pelvic Girdle • Consists of 3 separate bones in childhood – Ilium, ischium, & pubis • Bones fuse, retain separate names to regions of the coxal bones • Acetabulum – A deep hemispherical socket on lateral pelvic surface Ilium • Large, flaring bone • Forms the superior region of the coxal bone • Site of attachment for many muscles • Articulation with the sacrum forms sacroiliac joint Ischium • Forms posteroinferior region of the coxal bone • Anteriorly – joins the pubis • Ischial tuberosities – Are the strongest part of the hip bone Pubis • Forms the anterior region of the coxal bone • Lies horizontally in anatomical position • Pubic symphysis – The two pubic bones are joined by fibrocartilage at the midline • Pubic arch inferior to the pubic symphysis – Angle helps distinguish male from female pelves Bones of the pelvic girdle Tubercle of the iliac crest Anterior gluteal line Ilium Ala Iliac crest Posterior gluteal line Posterior superior iIiac spine Anterior superior iliac spine Inferior gluteal line Anterior inferior iliac spine Posterior inferior iliac spine Greater sciatic notch Acetabulum Ischial body Ischial spine Lesser sciatic notch Pubic body Pubis Ischium Ilium Ischial tuberosity Ischium Ischial ramus Pubis (b) Lateral view, right hip bone Inferior ramus of pubis True & False Pelves • Bony pelvis is divided into 2 regions – False (greater) pelvis bounded by alae of the iliac bones – True (lesser) pelvis inferior to pelvic brim • Forms a bowl containing the pelvic organs Pelvic Structures & Childbearing • Major differences between male & female pelves: – Female pelvis is adapted for childbearing • Pelvis is lighter, wider, & shallower than the male’s • Provides more room in the true pelvis The Lower Limb • Carries the entire weight of the erect body • Bones of lower limb are thicker & stronger than those of upper limb • Divided into 3 segments – Thigh, leg, & foot Thigh • The region of the lower limb between the hip and the knee • Femur the single bone of the thigh – Longest & strongest bone of the body – Ball-shaped head articulates with the acetabulum Structures of the Femur Fovea capitis Neck Greater trochanter Head Lesser trochanter Intertrochanteric line Intertrochanteric crest Gluteal tuberosity Linea aspera Medial and lateral supracondylar lines Intercondylar fossa Lateral condyle Lateral epicondyle Medial condyle Lateral epicondyle Adductor tubercle Medial epicondyle Patellar surface Anterior view Posterior view Patella • Triangular sesamoid bone • Imbedded in the tendon that secures the quadriceps muscles • Protects the knee anteriorly • Improves leverage of the thigh muscles across the knee Leg • Refers to the region of the lower limb between the knee & the ankle • Composed of the tibia & fibula – Tibia more massive medial bone of the leg • Receives weight of the body from the femur – Fibula stick-like lateral bone of the leg • Interosseous membrane – Connects the tibia & fibula Leg • Tibia articulates with femur at superior end – Forms the knee joint • Tibia articulates with talus at the inferior end – Forms the ankle joint • Fibula does not contribute to the knee joint – It stabilizes the ankle joint Structures of the Tibia & Fibula The Foot • Foot is composed of – Tarsus, metatarsus, & the phalanges • Important functions – Supports body weight – Acts as a lever to propel body forward when walking – Segmentation makes foot pliable & adapted to uneven ground Bones of the Foot Phalanges Distal Middle Proximal 1 Medial cuneiform 2 3 4 Metatarsals 5 Intermediate cuneiform Lateral cuneiform Navicular Cuboid Tarsals Talus Trochlea of talus Calcaneus (a) Superior view Tarsus • • • • Makes up the posterior half of the foot Contains 7 bones called tarsals Body weight is primarily borne by the talus & calcaneus Trochlea of the talus – Site of articulation with the tibia • Other tarsals are: – Navicular The (Talus) Caring (Calcaneus) – Cuboid Nurse (Navicular) Covers (Cuboid) – Medial Cuneiform Me (Medial Cuneiform) – Intermediate Cuneiform In (Intermed. Cuneiform) Love (Lateral Cuneiform) – Lateral Cuneiform Metatarsus • Consists of 5 small long bones called metatarsals • Numbered 1–5 beginning with the hallux (=big toe) • First metatarsal supports body weight Phalanges of the Toes • 14 phalanges of the toes – Smaller & less nimble than those of the fingers – Structure & arrangement are similar to phalanges of fingers – Except for the big toe, each toe has 3 phalanges • Proximal, middle, & distal Bones of the Foot Facet for lateral malleolus Navicular Intermediate cuneiform Lateral cuneiform Talus Calcaneus (c) Lateral view Cuboid Fifth metatarsal Lower Limb & Pelvis Disorders of the Appendicular Skeleton • Bone fractures • Hip dysplasia – Head of the femur slips out of acetabulum • Clubfoot – Soles of the feet turn medially The Appendicular Skeleton Throughout Life • Growth of the appendicular skeleton – Increases height – Changes body proportions • Upper/lower body ratio changes with age – At birth, head & trunk are 1.5 times as long as lower limbs – Lower limbs grow faster than the trunk – Upper/lower body ratio of 1 to 1 by age 10 The Appendicular Skeleton Throughout Life • Few changes occur in adult skeleton until middle age, when – Skeleton loses mass – Osteoporosis & limb fractures become more common Questions…? What’s Next? Lab: Appendicular Skeleton Mon Lecture: Append Skeleton contd. & Joints/Joint Movements Mon Lab: Finish Skeleton; Joints/Joint Movements