The Skeletal System

transcript

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

CLASSIFICATION OF

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

epiphysis

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 matrix rings

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-6-Phosphate

Receptor that targets them to lysosomes within the osteoclasts. Osteoclasts have many lysosomes and are eosinophilic.

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

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 enlarge the medullary cavity.

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 MARKINGSNAME OF BONE MARKING

DESCRIPTION

Projections (Muscle and Ligament Attachment)

Tuberosity

Trochanter

Tubercle

Large, rounded projection;May be roughened

Narrow ridge of boneUsually prominent

Very large, blunt, irregularly shaped process

Narrow ridge of bone, less prominent than a crest

Small, rounded projection or process

BONE MARKINGSNAME OF BONE MARKING

DESCRIPTION

Epicondyle

Process

Projection (form joints)

Condyle

Raised Area on or above a condyle

Sharp, slender, often pointed projection

A bony prominence

Bony expansion carried on a narrow neck

Smooth, nearly flat articular surface

Rounded articular projection

Armlike bar of bone

BONE MARKINGSNAKE OF BONE MARKING

DESCRIPTION

Depression and Openings

Meatus

Groove

Fissure

Foramen

Canal-like passageway

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

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

Furrow

Narrow, slit-like opening

Round or oval opening through a bone

LIST OF BONES

Axial Skeleton Skull

22 bones Throat

1 bone Middle Ears

6 bones Thorax

25 Bones Vertebral Column

26 bones Sub-total : 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 bones)

THE AXIAL SKELETON Skull

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 Forms the roof of the nasal cavity and part of

the medial wall of the orbits

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

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)

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

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 speak

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

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

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, cone-shaped 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

APPENDICULAR SKELETONComposed of the 126

bonesLimbs (appendages)

Upper Lower

Pectoral and pelvic girdle Attaches the limbs to

the axial skeleton

APPENDICULAR SKELETONBones of the

Shoulder (Pectoral) GirdleScapula (2)Clavicle (2)

Bones of the Shoulder GirdleClavicle

CollarboneLong, slender, doubly

curved boneAttaches to the

manubrium mediallyAttaches to the scapula

laterallyHelps form the shoulder

jointActs as a brace to hold

arm away from the top of the thorax

Helps prevent shoulder dislocation

Bones of the Shoulder GirdleScapulae

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

ScapulaeSignificant Bony Markings

Coracoid process Origin for some muscles that move the arm

Acromion Point of the shoulder articulating with the lateral

end of the clavicleGlenoid Cavity

Articulates with the head of the humerus

Scapulae

Bones of the Upper LimbsForm foundations of the

Arm Humerus

Forearm Radius Ulna

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

Consists of 30 separate bones

ArmHumerus

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

ForearmConsists 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 GirdlePelvic Girdle

Formed by two coxal bones

Commonly called hip bones

Bony pelvis Hip bones Sacrum Coccyx

Large and heavySecurely attached to the

axial skeletonMost important function:

Bearing weightProtects organs such as

the urinary bladder, reproductive organs

Bones of the Pelvic Girdle

Pelvic Girdle

Pelvic Grirdle

Pelvic Girdle

Bones of the Lower LimbCarry our total

body weightBones are much

thicker and stronger than the bones of the upper limbs

Bones of the Lower LimbThigh

Femur Thigh bone Heaviest Strongest

Bones of the Lower LimbLeg

Tibia Shin bone Larger More medial

Fibula Most slender bone

Bones of the Lower LimbFoot

Tarsals (7) Talus Calacaneus Navicular Cuneiform

Medial Intermediate Lateral

CuboidMetatarsals (5)Phalanges (14)

The Skeletal System

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