The Skeletal System

Anatomy and Physiology

Mark Neil V. Dancel, RN

THE SKELETAL SYSTEM  Skeleton  comes from the Greek word meaning

“dried up body”  Contains a total of 206 bones  Subdivided into 2:  Axial Skeleton  Appendicular Skeleton

BONES: AN OVERVIEW  FUNCTIONS OF THE

BONES  Support  Forms the internal framework of the body and anchors all soft organs (internal organs)

BONES: AN OVERVIEW  FUNCTIONS OF THE

BONES  Protection  Protect soft body organs

BONES: AN OVERVIEW  FUNCTIONS OF THE

BONES  Movement  Acts like levers to move the body and its parts

BONES: AN OVERVIEW  FUNCTIONS OF

THE BONES  Storage  Fats is stored in the internal cavities of bones  A storehouse for minerals (calcium)

BONES: AN OVERVIEW  FUNCTIONS OF

THE BONES  Blood Cell

Formation  Hematopoiesis occurs within the marrow cavities of certain bones

CLASSIFICATION OF BONES  Two Basic Types

of Bone Tissue:

 Compact Bone  Dense, smooth and homogenous  Spongy Bone

(Cancellous)

 Small needlelike pieces of bone (trabeculae) and open spaces

CLASSIFICATION OF BONES  ACCORDING TO SHAPE  Long Bones  typically longer than they are wide  They have shafts and heads at both ends  Short Bones  Generally cube-shaped  Contain mostly spongy bone  Flat Bones  Thin, flattened, and usually curved  Have 2 thin layers of compact bones and a layer of spongy bone in between  Irregular Bones  Bones that do not fit the preceding categories

SHAPE

CLASSIFICATION OF  ACCORDING TO BONES

STRUCTURE OF A LONG BONE  Gross Anatomy  Diaphysis or shaft

 Makes up most of the bone’s length  Composed of compact bone  Storage area (Medullary cavity) for fats (in adults) or blood cells (in infants)  METAPHYSIS

 The site of ossification, between the diaphysis and epiphysis  Periosteum

 A fibrous tissue membrane covering and protecting the diaphysis  Sharpey’s Fibers

 Secure the periosteum to the underlying bone  Epiphyses

 Ends of a long bone  Articular Cartilage

 Covers the external surface of the

STRUCTURE OF A LONG BONE  Microscopic Anatomy  Osteocytes  Mature bone cells found in tiny cavities within a matrix called LACUNAE  Lacunae are arranged in concentric circles called LAMELLAE around central (Haversian) canals  Haversian System or Osteon  A complex consisting of central canal and

BONE CELL TYPES



A) OSTEOPROGENITOR CELLS: The Stem-Cells of bone.  DISTRIBUTION:  Found on the inner lining of the periosteum and endosteum.  Found lining vascular canals.



B) OSTEOBLASTS: They are secretory cells.  SECRETE:  They secrete the bone matrix.  ALKALINE PHOSPHATASE which calcifies the matrix.

 They have polarity and resemble other secretory cells.



C) OSTEOCYTES: They are osteoblasts that have become trapped in their own matrix.  They are found in lacunae, between layers of lamellae, in the matrix of cortical bone.  The lacunae are potential spaces, filled with extracellular fluid in real life.

 CANALICULI: Fine cytoplasmic extensions of the osteocytes running perpendicular to the haversian canals.



D) OSTEOCLASTS: Large, multinucleate cells derived from monocytes.  They have acid hydrolases which have a Mannose-6Phosphate Receptor that targets them to lysosomes within

BONE FORMATION, GROWTH, AND REMODELLING  OSSIFICATION  Two Major Types:  Intramembranous Ossification Involving direct mineralization of richly vascular dense connective tissue membrane The membrane itself becomes the periosteum Immediately within are the compact bones with an inner core of cancellous bone

BONE FORMATION, GROWTH, AND REMODELLING

 Endochondral Ossification

 Replacement of a “scale model” of

hyaline cartilage by bone.  Bone is formed on a cartilage model.  The formation of the bone itself is identical to intramembranous type.

ENDOCHONDRAL OSSIFICATION

ENDOCHONDRAL OSSIFICATION

 GENERAL PROCESS  Cartilage matrix is laid down.  Perichondrium then becomes periosteum, when a vascular bud invades the perichondrial space.  The Vascular Bud contains blood cells, bone marrow cells, macrophages, endothelial cells.

 GROWTH IN LENGTH:  Occurs by proliferation of chondrocytes at the epiphyseal plates and at the primary ossification front.

 GROWTH IN DIAMETER:  Occurs by deposition of new bone under the periosteal collar along with simultaneous osteoclastic resorption, in order to maintain bone shape.  The osteoclastic resorption is necessary to

ENDOCHONDRAL OSSIFICATION

 PRIMARY OSSIFICATION CENTER  Occurs in the center of the diaphysis, and extends toward both epiphyses.  Thus there are two fronts of primary ossification.  Primary Ossification Centers close around the time of birth. Thereafter, long-bone growth occurs from the secondary ossification centers.  SECONDARY OSSIFICATION CENTER  Forms at the epiphyseal plate.  The orderly columns of chondrocytes are not seen here.  Growth occurs from the epiphysis downward, toward the epiphyseal plate.  EPIPHYSEAL CLOSURE  The end of longitudinal growth in long bone, when the primary ossification center overtakes (i.e. calcifies) the secondary ossification center, and hence long-bone growth ceases.

BONE MARKINGS NAME OF BONE MARKING Projections (Muscle

DESCRIPTION

and Ligament Attachment) Tuberosity

Large, rounded projection; May be roughened

Crest

Narrow ridge of bone Usually prominent

Trochanter

Very large, blunt, irregularly shaped process

Line

Narrow ridge of bone, less prominent than a crest

Tubercle Small, rounded projection or process

BONE MARKINGS NAME OF BONE MARKING Epicondyle

DESCRIPTION

Spine

Sharp, slender, often pointed projection

Process

A bony prominence

Raised Area on or above a condyle

Projection (form joints) Head

Bony expansion carried on a narrow neck

Facet

Smooth, nearly flat articular surface

Condyle

Rounded articular projection

Ramus

Armlike bar of bone

BONE MARKINGS NAKE OF BONE MARKING Depression and

DESCRIPTION

Openings Canal-like passageway Meatus Sinus

Cavity within a bone, filled with air and lined with mucus membrane

Fossa

Shallow, basin-like depression in a bone, often serving as an articular surface Furrow

Groove Narrow, slit-like opening Fissure Round or oval opening through a bone Foramen

LIST OF BONES  Axial Skeleton  Skull  22 bones  Throat  1 bone  Middle Ears  6 bones  Thorax  25 Bones  Vertebral Column  26 bones

 Sub-total :

bones

80

LIST OF BONES  Appendicular

Skeleton

 Upper Extremities  60 bones  Shoulder Girdle  4 bones  Pelvis  2 bones  Lower Extremities  60 bones

 Sub-total: 126

bones

LIST OF BONES  Axial Skeleton  80 bones

 Appendicular Skeleton  126 bones

 Summing it up: 80 + 126  Total = 206 Bones

AXIAL SKELETON

 Forms the longitudinal axis of the body 

Composed of :  The Skull

 Cranium  Facial Bones  The Hyoid Bone  The Ossicles

 The Ossicles of the Inner Ear  Incus (Anvil)  Malleus (Hammer)  Stapes (Stirrup)

 The Hyoid Bone  The Vertabral Column (Spine)  Cervical  Thoracic  Lumbar  Sacrum  Coccyx

 The Bony Thorax  Sternum  Ribs

APPENDICULAR SKELETON  Refers to the limbs or the appendages of

the body.

 The Shoulder Girdle  Scapulae  Clavicle  Bones of the Upper Limbs  Arm  Forearm  Hands  Bones of the Pelvic Girdle  Coxal Bones  Bones of the Lower Limbs  Thigh  Leg  Feet

THE AXIAL SKELETON 

Forms the longitudinal axis of the body 

Composed of : The Skull

 Cranium  Facial Bones

The Ossicles of the Inner Ear  Incus (Anvil)  Malleus (Hammer)  Stapes (Stirrup)

The Hyoid Bone The Vertabral Column (Spine)     

Cervical Thoracic Lumbar Sacrum Coccyx

The Bony Thorax  Sternum  Rib

  

The purpose of the axial skeleton (among other things) is to protect the body's most vital organs.

THE AXIAL SKELETON  The Skull  Formed by two sets of

bones

 Cranium – encloses and protects brain tissues  Facial Bones – hold the eyes in an anterior position and allow the facial muscles to show our feelings  Normally made up of 22

bones in an adult

 8 bones from the neurocranium (brain case)  14 bones from the splanchnocranium (facial

 Skull 

THE AXIAL SKELETON

CRANIUM  Frontal Bone

 Forms the forehead, the bony projections of the eyebrow and the superior part of each eye’s orbit

 Parietal Bones (2)

 Forms most of the superior and lateral walls of the cranium Sagittal suture – separates the parietal bones Coronal suture – separates the parietal and frontal bones

 Temporal Bones (2)

 Lie inferior to the parietal bones  Separated by the squamous sutures

 Occipital Bone

 Most posterior bone of the cranium  Forms the floor and back wall of the skull  Joins the parietal bones at the lamdoid suture

 Sphenoid Bone

 Butterfly-shaped bone that spans the width of the skull and forms part of the floor of the cranial cavity

 Ethmoid Bone

 Irregularly shaped bone lying anterior to the sphenoid

SKULL  Temporal Bone  Significant bone markings:  External acoustic meatus

 A canal that leads to the eardrum and middle ear

 Styloid Process

 Sharp, needlelike projection  Inferior to the external acoustic meatus  Attachment point for many neck muscles

 Zygomatic Process

 Thin bridge of bone that joins with the cheek bone

 Mastoid Process

 Rough projection posterior and inferior to the EAM  Attachment site for some muscles of the neck

 Jugular Foramen

 Junction of the occipital and temporal bones  Allows passage of the jugular vein Drains the brain

 Internal acoustic meatus

 Transmits cranial nerves VII and VIII

 Carotid canal

 Internal carotid artery runs Supplying blood to the brain

SKULL  Occipital Bone  Significant Bone Markings:  Foramen Magnum  “large hole”  Surrounds the lower part of the brain  Allows spinal chord to connect with the brain

 Occipital condyles  Rest on the first vertebra of the spinal column

SKULL  Sphenoid Bone  Significant Bony Markings  Sella Turcica – “Turk’s saddle”  Small depression in the midline of the sphenoid  Holds the Pituitary gland in place

 Foramen Ovale  Large oval opening in line with the posterior end of the sella turcica  Allows fibers of CN V to pass to the chewing muscles of the lower jaw

 Optic Canal  Allows optic nerve to pass to the eye

 Superior Orbital Fissure  Allows passage of cranial nerves controlling eye movements

SKULL  Ethmoid Bone  Significant Bony Landmarks  Crista Galli – “cock’s comb”  Attachment of the outermost covering of the brain

 Cribriform plates  Allow nerve fibers carrying impulses from the olfactory receptors of the nose reach the brain

 Superior and middle nasal conchae  Form part of the lateral walls of the nasal cavity  Increase the turbulence of air flowing through the nasal passages

SKULL (LATERAL VIEW)

SKULL (CROSS SECTION SUPERIOR VIEW)

SKULL

SKULL  FACIAL BONES  Palatine Bones  Lie posterior to the palatine process of the maxillae  Form the posterior part of the hard palate  Failure to fuse results in cleft palate  Zygomatic Bones  Cheek bones  Form a portion of the laterl wall of the orbits  Lacrimal Bones  Fingernail-sized bones forming part of the medial part of the orbit  Its groove serves as a passageway for tears

SKULL  FACIAL BONES  Nasal bones  Small rectangular bones forming the bridge of the nose  Vomer Bone – “plow”  Single bone in the median line of the nasal cavity  Forms most of the nasal septum  Inferior Nasal Conchae  Thin curved bones projecting from the lateral walls of the nasal cavity  Mandible  Lower jaw  Largest and strongest bone of the face  The horizontal part forms the chin  The 2 upright bars of bones (rami) extend to connect with the temporal bone  Also has alveolar margin where the lower teeth lie

SKULL (ANTERIOR VIEW)

SKULL (INFERIOR VIEW)

THE HYOID BONE  Only bone in the



  

body that does not articulate with any other bone Suspended in the midneck region about 2cm above the larynx Serves as movable base for the tongue Attachment point for neck muscles that raise Lower the larynx when we swallow or

THE HYOID BONE

FETAL SKULL

VERTEBRAL COLUMN (SPINE)  Serves as the axial support of the body  Extends from the skull to the pelvis  Surrounds and protects the spinal cord in

its central cavity  Prevents shock to the head when we walk or run  consists of 26 irregular bones (vertebrae)     

7 cervical vertebrae 12 thoracic vertebrae 5 lumbar vertebrae 1 (5 fused) sacrum 1 (4 fused) coccyx

 Separated by intervertebral discs

VERTEBRAL COLUMN (SPINE)

THE VERTEBRAE  STRUCTURAL PATTERN  Common Features:  Body or centrum

 Disc-like weight bearing part

 Vertebral arch

 Arch formed from the joining of all posterior extensions, the LAMINAE and PEDICLES

 Vertebral foramen

 Canal through which the spinal cord passes

 Transverse process

 Two lateral projections from the vertebral arch

 Spinous process

 Single projection arising from the posterior aspect of the vertebral arch  The fused lamina

 Superior and inferior articular processes

 Paired projections lateral to the vertebral foramen  Allows a vertebra to form joints with adjacent vertebrae

THE VERTEBRAE

THE VERTEBRAE  Cervical Vertebrae   

Composed of 7 vertebrae Identified as C1 to C7 The first 2 vertebrae are different  They perform functions not shared by other cervical vertebrae



C1 – ATLAS  No body  Allows you to nod “yes”



C2 – AXIS  Acts as pivot for the rotation of the atlas above

 Odontoid process/dens – acts as pivot point  Allows you to rotate your head from side to side to indicate “no”



C3 – C7 (typical vertebrae  Smallest, lightest vertebrae  Dual branched spinous process  The transverse process contain openings

 Vertebral arteries pass here on their way to the brain

CERVICAL VERTEBRAE

CERVICAL VERTEBRAE (ATLAS)

CERVICAL VERTEBRAE (AXIS)

CERVICAL VERTEBRAE (TYPICAL)

THORACIC VERTEBRAE  Composed of 12 vertebrae  Identified as T1 to T12  All typical  Has 2 costal facets on each side  Long spinous process and hooks

sharply downward

THORACIC VERTEBRAE

THORACIC VERTEBRAE

LUMBAR VERTEBRAE  Consists of 5 typical vertebrae  Identified as L1 to L5  Massive blocklike bodies  Short, hatchet-shaped spinous

process  Sturdiest of the vertebrae

LUMBAR VERTEBRAE

SACRUM  Formed by the fusion of 5 vertebrae  Articulates to L5 superiorly  Connects to coccyx inferiorly  Wing-like ALAE articulate laterally to

the hip bones, forming the sacroiliac joints  Forms posterior wall of the pelvis

SACRUM

COCCYX  Formed from the fusion of 3 to 5

irregularly shaped vertebrae  The human “tailbone”  A remnant of the tail that other vertebrate animals have

COCCYX

BONY THORAX  Composed of the

sternum, ribs, and thoracic vertebrae  Often called “thoracic cage”  Forms a protective, coneshaped cage

BONY THORAX  STERNUM  Breastbone  Typical flat bone  A result of fusion of

3 bones:  Manubrium  Body  Xyphoid process  Attached to the first

7 pairs of ribs

STERNUM  Significant bony landmarks  Jugular notch  Concave upper border of the manubrium  Sternal angle

 The manubrium and body meet  Xiphisternal joint  The point where the body and xiphoid process fuse

BONY THORAX  RIBS  12 Pairs of these form the wall of the bony

thorax  All ribs articulate with the vertebral column posteriorly  Curved downward and toward the anterior body  True Ribs  First 7 pairs attach directly to the sternum by costal cartilages  False Ribs  The next 5 pairs  Attached indirectly to the sternum  Are not attached at all  The last 2 pairs are called FLOATING RIBS  Do not have sternal attachments at all

RIB CAGE

RIBS

RIBS

APPENDICULAR SKELETON Composed of the 126

bones Limbs (appendages)

Upper  Lower 

Pectoral and pelvic

girdle 

Attaches the limbs to the axial skeleton

APPENDICULAR SKELETON Bones of the

Shoulder (Pectoral) Girdle Scapula (2) Clavicle (2)

Bones of the Shoulder Girdle Clavicle  Collarbone  Long, slender, doubly curved bone  Attaches to the manubrium medially  Attaches to the scapula laterally  Helps form the shoulder joint  Acts as a brace to hold arm away from the top of the thorax  Helps prevent shoulder dislocation

Bones of the Shoulder Girdle  Scapulae  Shoulder blades  Large, flat, triangular  often called “wings”  Located at the dorsal portion of the thorax  Covers the area from the 2nd to the 7th rib  Has 3 borders   

Superior Lateral Medial

 Has 3 angles  Superior  Lateral  Inferior

Scapulae Significant Bony Markings Coracoid process 

Origin for some muscles that move the arm

Acromion 

Point of the shoulder articulating with the lateral end of the clavicle

Glenoid Cavity 

Articulates with the head of the humerus

Scapulae

Bones of the Upper Limbs

Form foundations of the Arm 

Humerus

Forearm

Radius  Ulna 

Hand

Carpals (8)  Metacarpals (5)  Phalanges (14) 

Consists of 30 separate

bones

Arm  Humerus  Typical long bone  Significant Markings:  







Head  Fits into the Glenoid Cavity Greater and Lesser Tubercles  Sites of muscle attachments Deltoid tuberosity  Attachment for the deltoid muscle Radial Groove  Marks the course of the radial nerve Trochlea and Capitulum  Distal ends that articulates with the bones of the forearm

Forearm Consists of 2 bones Radius and Ulna Joins at the radioulnar joints  Connected along their entire length by interosseous membrane 

Hand  Carpals (8)  Proximal    

Navicular/Scaphoid  Most frequently fractured Lunate  Frequently dislocated Triquetrium Pisiform  Pea bone  Smallest carpal

 Distal  Greater Multangular/Trapezium  Lesser Multangular/Trapezoid  Capitate  Hamate

 Metacarpals (5)  Phalanges (14)  Proximal phalanx  Middle phalanx  Distal phalanx  Except Thumb with 2 phalanges  Proximal and distal  Pollex

Bones of the Pelvic Girdle Pelvic Girdle  Formed by two coxal bones  Commonly called hip bones  Bony pelvis   

Hip bones Sacrum Coccyx

 Large and heavy  Securely attached to the

axial skeleton  Most important function: 

Bearing weight

 Protects organs such as

the urinary bladder,

Bones of the Pelvic Girdle

Pelvic Girdle

Pelvic Grirdle

Pelvic Girdle

Bones of the Lower Limb Carry our total

body weight Bones are much thicker and stronger than the bones of the upper limbs

Bones of the Lower Limb Thigh Femur

Thigh bone  Heaviest  Strongest 

Bones of the Lower Limb Leg Tibia

Shin bone  Larger  More medial 

Fibula 

Most slender bone

Bones of the Lower Limb Foot  Tarsals (7)    



Talus Calacaneus Navicular Cuneiform  Medial  Intermediate  Lateral Cuboid

 Metatarsals (5)  Phalanges (14)