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The Skeletal System. Function of Bones. Support – form the framework that supports the body and cradles soft organs Protection – provide a protective case for the brain, spinal cord, and vital organs Movement – provide levers for muscles

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function of bones
Function of Bones
  • Support – form the framework that supports the body and cradles soft organs
  • Protection – provide a protective case for the brain, spinal cord, and vital organs
  • Movement – provide levers for muscles
  • Mineral storage – reservoir for minerals, especially calcium and phosphorus
  • Blood cell formation – hematopoiesis occurs within the marrow cavities of bones
bone markings
Bone Markings
  • Bulges, depressions, and holes that serve as:
    • Sites of attachment for muscles, ligaments, and tendons
    • Joint surfaces
    • Conduits for blood vessels and nerves
bone markings projections sites of muscle and ligament attachment
Bone Markings: Projections – Sites of Muscle and Ligament Attachment
  • Tuberosity – rounded projection
  • Crest – narrow, prominent ridge of bone
  • Trochanter – large, blunt, irregular surface
  • Line – narrow ridge of bone
bone markings projections sites of muscle and ligament attachment5
Bone Markings: Projections – Sites of Muscle and Ligament Attachment
  • Tubercle – small rounded projection
  • Epicondyle – raised area above a condyle
  • Spine – sharp, slender projection
  • Process – any bony prominence
bone markings projections projections that help to form joints
Bone Markings: Projections – Projections That Help to 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 depressions and openings
Bone Markings: Depressions and Openings
  • Meatus – canal-like passageway
  • Sinus – cavity within a bone
  • Fossa – shallow, basinlike depression
  • Groove – furrow
  • Fissure – narrow, slitlike opening
  • Foramen – round or oval opening through a bone
the skull
The Skull
  • The skull, the body’s most complex bony structure, is formed by the cranium and facial bones
  • Cranium – protects the brain and is the site of attachment for head and neck muscles
  • Facial bones
    • Supply the framework of the face, the sense organs, and the teeth
    • Provide openings for the passage of air and food
    • Anchor the facial muscles of expression
anatomy of the cranium
Eight cranial bones – two parietal, two temporal, frontal, occipital, sphenoid, and ethmoid

Cranial bones are thin and remarkably strong for their weight

Anatomy of the Cranium
Parietal Bones and Major Associated SuturesForm most of the superior and lateral aspects of the skull
1.Parietal Bone

2. Coronal Suture

3. Frontal Bone

4. Nasal Bone


6. Lacrimal Bone

7. Orbital Part of Ethmoid

8. Zygomatic Bone

9. Maxilla

10. Body of Mandible

11. Ramus of Mandible

12.Coronoid Process

13.Mandibular Condyle

14.Mental Foramen

15.Styloid Process

16. External Acoustic Meatus

17. Mastoid Process

18. Zygomatic Process

19.Temporal Bone

20. Greater Wing of Sphenoid

21.Inferior Temporal Line

22. Superior Temporal Line

23.Squamosal Suture

24.Lambdoidal Suture

25.Occipital Bone

The bone at the top is the Frontal Bone. The tongue shaped bone below the Frontal Bone is the Ethmoid Bone. Below that is the Sphenoid Bone. To the left and the right in below the Sphenoid Bone are the Left and Right Temporal Bones. In the Occiput at the bottom of the picture you will notice a large opening, called the Foramen Magnum, through which the spinal cord passes.  (Photo by Paula Kliewer Photography)
1.Anterior Palatine Foramen

2. Palatine Process of Maxilla

3. Palatine

4. Greater Palatine Foramen

5.Lesser Palatine Foramen

6. Pterygoid Processes of Sphenoid

7.Zygomatic Process

8. Squamous Part of Temporal Bone

9. Mandibular Fossa

10. Styloid Process

11.Stylomastoid Foramen

12. Mastoid Process

13.Mastoid Foramen

14. Superior Nuchal Line

15. External Occipital Protruberance

16.Median Nuchal Line

17. Inferior Nuchal Line1

8.Foramen Magnum

19. Condyloid Canal

20.Occipital Condyle

21.Hypoglossal Canal

22.Jugular Foramen

23.Carotid Canal 24.Foramen Spinosum

25.Foramen Ovale

26.Foramen Lacerum


28.Transverse Palatine Suture

29.Median Palatine Suture

  •  1. Greater horns
  •  2.Lesser horns
  •  3.  Body
wormian bones
Wormian Bones
  • Tiny irregularly shaped bones that appear within sutures
vertebral column42
Formed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure results

Cervical vertebrae – 7 bones of the neck

Thoracic vertebrae – 12 bones of the torso

Lumbar vertebrae – 5 bones of the lower back

Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones

Vertebral Column
vertebral column curvatures
Vertebral Column: Curvatures
  • Posteriorly concave curvatures – cervical and lumbar
  • Posteriorly convex curvatures – thoracic and sacral
  • Abnormal spine curvatures include scoliosis (abnormal lateral curve), kyphosis (hunchback), and lordosis (swayback)
vertebral column ligaments
Anterior and posterior longitudinal ligaments – continuous bands down the front and back of the spine from the neck to the sacrum

Short ligaments connect adjoining vertebrae together

Vertebral Column: Ligaments
vertebral column intervertebral discs
Cushionlike pad composed of two parts

Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility

Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage

Vertebral Column: Intervertebral Discs
general structure of vertebrae
General Structure of Vertebrae
  • Body or centrum – disc-shaped, weight-bearing region
  • Vertebral arch – composed of pedicles and laminae that, along with the centrum, enclose the vertebral foramen
  • Vertebral foramina – make up the vertebral canal through which the spinal cord passes
general structure of vertebrae47
Spinous processes project posteriorly, and transverse processes project laterally

Superior and inferior articular processes – protrude superiorly and inferiorly from the pedicle-lamina junctions

Intervertebral foramina – lateral openings formed from notched areas on the superior and inferior borders of adjacent pedicles

General Structure of Vertebrae
cervical vertebrae
Seven vertebrae (C1-C7) are the smallest, lightest vertebrae

C3-C7 are distinguished with an oval body, short spinous processes, and large, triangular vertebral foramina

Each transverse process contains a transverse foramen

Cervical Vertebrae
cervical vertebrae the atlas c 1
The atlas has no body and no spinous process

It consists of anterior and posterior arches, and two lateral masses

The superior surfaces of lateral masses articulate with the occipital condyles

Cervical Vertebrae: The Atlas (C1)
cervical vertebrae the axis c 2
The axis has a body, spine, and vertebral arches as do other cervical vertebrae

Unique to the axis is the dens, or odontoid process, which projects superiorly from the body and is cradled in the anterior arch of the atlas

The dens is a pivot for the rotation of the atlas

Cervical Vertebrae: The Axis (C2)
thoracic vertebrae
There are twelve vertebrae (T1-T12) all of which articulate with ribs

Major markings include two facets and two demifacets on the heart-shaped body, the circular vertebral foramen, transverse processes, and a long spinous process

The location of the articulate facets prevents flexion and extension, but allows rotation of this area of the spine

Thoracic Vertebrae
lumbar vertebrae
The five lumbar vertebrae (L1-L5) are located in the small of the back and have an enhanced weight-bearing function

They have short, thick pedicles and laminae, flat hatchet-shaped spinous processes, and a triangular-shaped vertebral foramen

Orientation of articular facets locks the lumbar vertebrae together to provide stability

Lumbar Vertebrae
  • Sacrum
    • Consists of five fused vertebrae (S1-S5), which shape the posterior wall of the pelvis
    • It articulates with L5 superiorly, and with the auricular surfaces of the hip bones
    • Major markings include the sacral promontory, transverse lines, alae, dorsal sacral foramina, sacral canal, and sacral hiatus
Coccyx (Tailbone)

The coccyx is made up of four (in some cases three to five) fused vertebrae that articulate superiorly with the sacrum

bony thorax thoracic cage
The thoracic cage is composed of the thoracic vertebrae dorsally, the ribs laterally, and the sternum and costal cartilages anteriorly


Forms a protective cage around the heart, lungs, and great blood vessels

Supports the shoulder girdles and upper limbs

Provides attachment for many neck, back, chest, and shoulder muscles

Uses intercostal muscles to lift and depress the thorax during breathing

Bony Thorax (Thoracic Cage)
sternum breastbone
Sternum (Breastbone)
  • A dagger-shaped, flat bone that lies in the anterior midline of the thorax
  • Results from the fusion of three bones – the superior manubrium, the body, and the inferior xiphoid process
  • Anatomical landmarks include the jugular (suprasternal) notch, the sternal angle, and the xiphisternal joint
There are twelve pair of ribs forming the flaring sides of the thoracic cage

All ribs attach posteriorly to the thoracic vertebrae

The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages

Ribs 8-10 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage

Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment

appendicular skeleton
Appendicular Skeleton
  • The appendicular skeleton is made up of the bones of the limbs and their girdles
  • Pectoral girdles attach the upper limbs to the body trunk
  • Pelvic girdle secures the lower limbs
pectoral girdles shoulder girdles
The pectoral girdles consist of the anterior clavicles and the posterior scapulae

They attach the upper limbs to the axial skeleton in a manner that allows for maximum movement

They provide attachment points for muscles that move the upper limbs

Pectoral Girdles (Shoulder Girdles)
clavicles collarbones
The clavicles are slender, doubly curved long bones lying across the superior thorax

The acromial (lateral) end articulates with the scapula, and the sternal (medial) end articulates with the sternum

They provide attachment points for numerous muscles, and act as braces to hold the scapulae and arms out laterally away from the body

Clavicles (Collarbones)
scapulae shoulder blades
The scapulae are triangular, flat bones lying on the dorsal surface of the rib cage, between the second and seventh ribs

Scapulae have three borders and three angles

Major markings include the suprascapular notch, the supraspinous and infraspinous fossae, the spine, the acromion, and the coracoid process

Scapulae (Shoulder Blades)
the upper limb
The Upper Limb
  • The upper limb consists of the arm (brachium), forearm (antebrachium), and hand (manus)
  • Thirty-seven bones form the skeletal framework of each upper limb
The humerus is the sole bone of the arm

It articulates with the scapula at the shoulder, and the radius and ulna at the elbow

The bones of the forearm are the radius and ulna

They articulate proximally with the humerus and distally with the wrist bones

They also articulate with each other proximally and distally at small radioulnar joints

Interosseous membrane connects the two bones along their entire length

Skeleton of the hand contains wrist bones (carpals), bones of the palm (metacarpals), and bones of the fingers (phalanges)Hand
Carpus (Wrist)

Consists of eight bones

Scaphoid, lunate, triquetral, and pisiform proximally

Trapezium, trapezoid, capitate, and hamate distally

metacarpus palm
Metacarpus (Palm)
  • Five numbered (1-5) metacarpal bones radiate from the wrist to form the palm
    • Their bases articulate with the carpals proximally, and with each other medially and laterally
    • Heads articulate with the phalanges
phalanges fingers
Each hand contains 14 miniature long bones called phalanges

Fingers (digits) are numbered 1-5, beginning with the thumb (pollex)

Each finger (except the thumb) has three phalanges – distal, middle, and proximal

The thumb has no middle phalanx

Phalanges (Fingers)
pelvic girdle hip
The hip is formed by a pair of hip bones (os coxae, or coxal)

Together with the sacrum and the coccyx, these bones form the bony pelvis

The pelvis

Attaches the lower limbs to the axial skeleton with the strongest ligaments of the body

Transmits weight of the upper body to the lower limbs

Supports the visceral organs of the pelvis

Pelvic Girdle (Hip)
The ilium is a large flaring bone that forms the superior region of the coxal bone

It consists of a body and a superior winglike portion called the ala

The broad posterolateral surface is called the gluteal surface

The auricular surface articulates with the sacrum (sacroiliac joint)

Major markings include the iliac crests, four spines, greater sciatic notch, iliac fossa, arcuate line, and the pelvic brim

The ischium forms the posteroinferior part of the hip bone

The thick body articulates with the ilium, and the thinner ramus articulates with the pubis

Major markings include the ischial spine, lesser sciatic notch, and the ischial tuberosity

The pubic bone forms the anterior portion of the hip bone

It articulates with the ischium and the ilium

Major markings include superior and inferior rami, the pubic crest, pubic tubercle, pubic arch, pubic symphysis, and obturator foramen (along with ilium and ischium)

the lower limb
The Lower Limb
  • The three segments of the lower limb are the thigh, leg, and foot
  • They carry the weight of the erect body, and are subjected to exceptional forces when one jumps or runs
The sole bone of the thigh is the femur, the largest and strongest bone in the body

It articulates proximally with the hip and distally with the tibia and fibula

Major markings include the head, fovea capitis, greater and lesser trochanters, gluteal tuberosity, lateral and medial condyles and epicondyles, linea aspera, patellar surface, and the intercondylar notch

  • The tibia and fibula form the skeleton of the leg
  • They are connected to each other by the interosseous membrane
  • They articulate with the femur proximally and with the ankle bones distally
  • They also articulate with each other via the immovable tibiofibular joints
Receives the weight of the body from the femur and transmits it to the foot

Major markings include medial and lateral condyles, intercondylar eminence, the tibial tuberosity, anterior crest, medial malleolus, and fibular notch

  • Sticklike bone with slightly expanded ends located laterally to the tibia
  • Major markings include the head and lateral malleolus
The skeleton of the foot includes the tarsus, metatarsus, and the phalanges (toes)

The foot supports body weight and acts as a lever to propel the body forward in walking and running

Composed of seven bones that form the posterior half of the foot

Body weight is carried primarily on the talus and calcaneus

Talus articulates with the tibia and fibula superiorly, and the calcaneus inferiorly

Other tarsus bones include the cuboid and navicular, and the medial, intermediate, and lateral cuneiforms

  • Forms the heel of the foot
  • Carries the talus on its superior surface
  • Point of attachment for the calcaneal (Achilles) tendon of the calf muscles
metatarsus and phalanges
Metatarsus and Phalanges


Five (1-5) long bones that articulate with the proximal phalanges

The enlarged head of metatarsal 1 forms the “ball of the foot”


The 14 bones of the toes

Each digit has three phalanges except the hallux, which has no middle phalanx

Metatarsus and Phalanges
arches of the foot
The foot has three arches maintained by interlocking foot bones and strong ligaments

Arches allow the foot to hold up weight

The arches are:

Lateral longitudinal – cuboid is keystone of this arch

Medial longitudinal – talus is keystone of this arch

Transverse – runs obliquely from one side of the foot to the other

Arches of the Foot
developmental aspects fetal skull
Infant skull has more bones than the adult skull

At birth, fetal skull bones are incomplete and connected by fontanels


Unossified remnants of fibrous membranes between fetal skull bones

The four fontanels are anterior, posterior, mastoid, and sphenoid

Developmental Aspects: Fetal Skull
B. The appendicular skeleton includes the bones of the arms and legs and structures associated with them (shoulder, hip, wrist, ankle, fingers, toes).
classification of bones by shape
Classification of Bones: By Shape
  • Long bones – longer than they are wide (e.g., humerus)
classification of bones by shape96
Classification of Bones: By Shape
  • Short bones
    • Cube-shaped bones of the wrist and ankle
    • Bones that form within tendons (e.g., patella)
classification of bones by shape97
Classification of Bones: By Shape
  • Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)
classification of bones by shape98
Classification of Bones: By Shape
  • Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)
joints chapter 8
Joints Chapter 8
  • C. Joints are where two or more bones meet.
joints articulations
Joints (Articulations)
  • Weakest parts of the skeleton
  • Articulation – site where two or more bones meet
  • Functions of joints
    • Give the skeleton mobility
    • Hold the skeleton together
classification of joints structural
Classification of Joints: Structural
  • Structural classification focuses on the material binding bones together and whether or not a joint cavity is present
  • The three structural classifications are:
    • Fibrous
    • Cartilaginous
    • Synovial
classification of joints functional
Classification of Joints: Functional
  • Functional classification is based on the amount of movement allowed by the joint
  • The three functional classes of joints are:
    • Synarthroses – immovable
    • Amphiarthroses – slightly movable
    • Diarthroses – freely movable
fibrous structural joints
Fibrous Structural Joints
  • The bones are joined by fibrous tissues
  • There is no joint cavity
  • Most are immovable
  • There are three types – sutures, syndesmoses, and gomphoses
fibrous structural joints sutures
Fibrous Structural Joints: Sutures
  • Occur between the bones of the skull
  • Comprised of interlocking junctions completely filled with connective tissue fibers
  • Bind bones tightly together, but allow for growth during youth
  • In middle age, skull bones fuse and are called synostoses
fibrous structural joints syndesmoses
Bones are connected by a fibrous tissue ligament

Movement varies from immovable to slightly variable

Examples include the connection between the tibia and fibula, and the radius and ulna

Fibrous Structural Joints: Syndesmoses
fibrous structural joints gomphoses
Fibrous Structural Joints: Gomphoses
  • The peg-in-socket fibrous joint between a tooth and its alveolar socket
  • The fibrous connection is the periodontal ligament
cartilaginous joints
Cartilaginous Joints
  • Articulating bones are united by cartilage
  • Lack a joint cavity
  • Two types – synchondroses and symphyses
cartilaginous joints synchondroses
A bar or plate of hyaline cartilage unites the bones

All synchondroses are synarthrotic

Examples include:

Epiphyseal plates of children

Joint between the costal cartilage of the first rib and the sternum

Cartilaginous Joints: Synchondroses
cartilaginous joints symphyses
Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage

Amphiarthrotic joints designed for strength and flexibility

Examples include intervertebral joints and the pubic symphysis of the pelvis

Cartilaginous Joints: Symphyses
synovial joints
Synovial Joints
  • Those joints in which the articulating bones are separated by a fluid-containing joint cavity
  • All are freely movable diarthroses
  • Examples – all limb joints, and most joints of the body
synovial joints general structure
Synovial joints all have the following

Articular cartilage

Joint (synovial) cavity

Articular capsule

Synovial fluid

Reinforcing ligaments

Synovial Joints: General Structure
synovial joints friction reducing structures
Bursae – flattened, fibrous sacs lined with synovial membranes and containing synovial fluid

Common where ligaments, muscles, skin, tendons, or bones rub together

Tendon sheath – elongated bursa that wraps completely around a tendon

Synovial Joints: Friction-Reducing Structures
synovial joints movement
Synovial Joints: Movement
  • The two muscle attachments across a joint are:
    • Origin – attachment to the immovable bone
    • Insertion – attachment to the movable bone
  • Described as movement along transverse, frontal, or sagittal planes
synovial joints range of motion
Synovial Joints: Range of Motion
  • Nonaxial – slipping movements only
  • Uniaxial – movement in one plane
  • Biaxial – movement in two planes
  • Multiaxial – movement in or around all three planes
gliding movements
Gliding Movements
  • One flat bone surface glides or slips over another similar surface
  • Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae
angular movement
Angular Movement
  • Flexion — bending movement that decreases the angle of the joint
  • Extension — reverse of flexion; joint angle is increased
  • Dorsiflexion and plantar flexion — up and down movement of the foot
  • Abduction — movement away from the midline
  • Adduction — movement toward the midline
  • Circumduction — movement describes a cone in space
dorsiflexion plantar flexion abduction adduction circumduction
Dorsiflexion/Plantar flexionAbduction/Adduction/Circumduction

The turning of a bone around its own long axis


Between first two vertebrae

Hip and shoulder joints

special movements
Special Movements
  • Supination and pronation
  • Inversion and eversion
  • Protraction and retraction
  • Elevation and depression
  • Opposition
hinge joint
Hinge joints

Cylindrical projections of one bone fits into a trough-shaped surface on another

Motion is along a single plane

Uniaxial joints permit flexion and extension only

Examples: elbow and interphalangeal joints

Hinge Joint:
condyloid or ellipsoidal joints
Oval articular surface of one bone fits into a complementary depression in another

Both articular surfaces are oval

Biaxial joints permit all angular motions

Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints

Condyloid, or Ellipsoidal, Joints
saddle joint
Condyloid, or Ellipsoidal, Joints

Oval articular surface of one bone fits into a complementary depression in another

Both articular surfaces are oval

Biaxial joints permit all angular motions

Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints

Saddle Joint
ball and socket joint
A spherical or hemispherical head of one bone articulates with a cuplike socket of another

Multiaxial joints permit the most freely moving synovial joints

Examples: shoulder and hip joints

Ball and Socket Joint
pivot joint
Pivot Joint
  • Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another
  • Only uniaxial movement allowed
  • Examples: joint between the axis and the dens, and the proximal radioulnar joint
synovial joints knee
Largest and most complex joint of the body

Allows flexion, extension, and some rotation

Three joints in one surrounded by a single joint cavity


Lateral and medial tibiofemoral joints

Synovial Joints: Knee
synovial joints knee other supporting structures
Anterior cruciate ligament

Posterior cruciate ligament

Medial meniscus (semilunar cartilage)

Lateral meniscus

Synovial Joints: Knee – Other Supporting Structures
synovial joints knee posterior superficial view
Adductor magnus tendon

Articular capsule

Oblique popliteal ligament

Arcuate popliteal ligament

Semimembranosus tendon

Synovial Joints: Knee – Posterior Superficial View
  • D. Ligaments are tough bands of connective tissue that attaches one bone to another.
  • E. Bands of cartilage that binds muscle to bone.
  • E. Bursae act to decrease friction and keep bones and tendons from rubbing against each other.
F. Anatomy of a bone:
    • 1. Compact bone
      • a. Found in the middle of long bones
structure of long bone
Structure of Long Bone
  • Long bones consist of a diaphysis and an epiphysis
  • Diaphysis
    • Tubular shaft that forms the axis of long bones
    • Composed of compact bone that surrounds the medullary cavity
    • Yellow bone marrow (fat) is contained in the medullary cavity
structure of long bone151
Structure of Long Bone
  • Epiphyses
    • Expanded ends of long bones
    • Exterior is compact bone, and the interior is spongy bone
    • Joint surface is covered with articular (hyaline) cartilage
    • Epiphyseal line separates the diaphysis from the epiphyses
bone membranes
Bone Membranes
  • Periosteum – double-layered protective membrane
    • Outer fibrous layer is dense regular connective tissue
    • Inner osteogenic layer is composed of osteoblasts and osteoclasts
    • Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina
    • Secured to underlying bone by Sharpey’s fibers
  • Endosteum – delicate membrane covering internal surfaces of bone
structure of short irregular and flat bones
Structure of Short, Irregular, and Flat Bones
  • Thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone (diploë) on the inside
  • Have no diaphysis or epiphyses
  • Contain bone marrow between the trabeculae
location of hematopoietic tissue red marrow
Location of Hematopoietic Tissue (Red Marrow)
  • In infants
    • Found in the medullary cavity and all areas of spongy bone
  • In adults
    • Found in the diploë of flat bones, and the head of the femur and humerus
microscopic structure of bone compact bone
Microscopic Structure of Bone: Compact Bone
  • Haversian system, or osteon – the structural unit of compact bone
    • Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen
    • Haversian, or central canal – central channel containing blood vessels and nerves
    • Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
microscopic structure of bone compact bone159
Microscopic Structure of Bone: Compact Bone
  • Osteocytes – mature bone cells
  • Lacunae – small cavities in bone that contain osteocytes
  • Canaliculi – hairlike canals that connect lacunae to each other and the central canal
2. Spongy bone
    • a. Found at the ends of long bone
chemical composition of bone organic
Chemical Composition of Bone: Organic
  • Osteoblasts – bone-forming cells
  • Osteocytes – mature bone cells
  • Osteoclasts – large cells that resorb or break down bone matrix
  • Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen
chemical composition of bone inorganic
Chemical Composition of Bone: Inorganic
  • Hydroxyapatites, or mineral salts
    • Sixty-five percent of bone by mass
    • Mainly calcium phosphates
    • Responsible for bone hardness and its resistance to compression
4. Your bones grow in length and diameter.
    • a. Growth occurs are growth plate
bone development
Bone Development
  • Osteogenesis and ossification – the process of bone tissue formation, which leads to:
    • The formation of the bony skeleton in embryos
    • Bone growth until early adulthood
    • Bone thickness, remodeling, and repair
formation of the bony skeleton
Formation of the Bony Skeleton
  • Begins at week 8 of embryo development
  • Intramembranous ossification – bone develops from a fibrous membrane
  • Endochondral ossification – bone forms by replacing hyaline cartilage
intramembranous ossification
Intramembranous Ossification
  • Formation of most of the flat bones of the skull and the clavicles
  • Fibrous connective tissue membranes are formed by mesenchymal cells
stages of intramembranous ossification
Stages of Intramembranous Ossification
  • An ossification center appears in the fibrous connective tissue membrane
  • Bone matrix is secreted within the fibrous membrane
  • Woven bone and periosteum form
  • Bone collar of compact bone forms, and red marrow appears
endochondral ossification
Endochondral Ossification
  • Begins in the second month of development
  • Uses hyaline cartilage “bones” as models for bone construction
  • Requires breakdown of hyaline cartilage prior to ossification
importance of ionic calcium in the body
Importance of Ionic Calcium in the Body
  • Calcium is necessary for:
    • Transmission of nerve impulses
    • Muscle contraction
    • Blood coagulation
    • Secretion by glands and nerve cells
    • Cell division
hormonal mechanism
Hormonal Mechanism
  • Rising blood Ca2+ levels trigger the thyroid to release calcitonin
  • Calcitonin stimulates calcium salt deposit in bone
  • Falling blood Ca2+ levels signal the parathyroid glands to release PTH
  • PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood
importance of ionic calcium in the body182
Importance of Ionic Calcium in the Body
  • Calcium is necessary for:
    • Transmission of nerve impulses
    • Muscle contraction
    • Blood coagulation
    • Secretion by glands and nerve cells
    • Cell division
response to mechanical stress
Response to Mechanical Stress
  • Wolff’s law – a bone grows or remodels in response to the forces or demands placed upon it
  • Observations supporting Wolff’s law include
    • Long bones are thickest midway along the shaft (where bending stress is greatest)
    • Curved bones are thickest where they are most likely to buckle
bone fractures breaks
Bone Fractures (Breaks)
  • Bone fractures are classified by:
    • The position of the bone ends after fracture
    • The completeness of the break
    • The orientation of the bone to the long axis
    • Whether or not the bones ends penetrate the skin
types of bone fractures
Types of Bone Fractures
  • Nondisplaced – bone ends retain their normal position
  • Displaced – bone ends are out of normal alignment
  • Complete – bone is broken all the way through
  • Incomplete – bone is not broken all the way through
  • Linear – the fracture is parallel to the long axis of the bone
types of bone fractures186
Types of Bone Fractures
  • Transverse – the fracture is perpendicular to the long axis of the bone
  • Compound (open) – bone ends penetrate the skin
  • Simple (closed) – bone ends do not penetrate the skin
common types of fractures
Common Types of Fractures
  • Comminuted – bone fragments into three or more pieces; common in the elderly
  • Spiral – ragged break when bone is excessively twisted; common sports injury
  • Depressed – broken bone portion pressed inward; typical skull fracture
  • Compression – bone is crushed; common in porous bones
common types of fractures188
Common Types of Fractures
  • Epiphyseal – epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying
  • Greenstick – incomplete fracture where one side of the bone breaks and the other side bends; common in children
stages in the healing of a bone fracture
Stages in the Healing of a Bone Fracture
  • Hematoma formation
    • Torn blood vessels hemorrhage
    • A mass of clotted blood (hematoma) forms at the fracture site
    • Site becomes swollen, painful, and inflamed
stages in the healing of a bone fracture193
Stages in the Healing of a Bone Fracture

Fibrocartilaginous callus forms

Granulation tissue (soft callus) forms a few days after the fracture

Capillaries grow into the tissue and phagocytic cells begin cleaning debris

Bones produce blood cells in the red marrow.
  • a. Found in
    • 1. humerus
    • 2. femur
    • 3. sternum
    • 4. ribs
    • 5. vertebrae
    • 6. pelvis
stages in the healing of a bone fracture the fibrocartilaginous callus forms when
Stages in the Healing of a Bone FractureThe fibrocartilaginous callus forms when:
  • Osteoblasts and fibroblasts migrate to the fracture and begin reconstructing the bone
  • Fibroblasts secrete collagen fibers that connect broken bone ends
  • Osteoblasts begin forming spongy bone
  • Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies
stages in the healing of a bone fracture196
Stages in the Healing of a Bone Fracture
  • Bony callus formation
    • New bone trabeculae appear in the fibrocartilaginous callus
    • Fibrocartilaginous callus converts into a bony (hard) callus
    • Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later
stages in the healing of a bone fracture197
Stages in the Healing of a Bone Fracture
  • Stages in the Healing of a Bone Fracture
  • Bone remodeling
    • Excess material on the bone shaft exterior and in the medullary canal is removed
    • Compact bone is laid down to reconstruct shaft walls
homeostatic imbalances
Homeostatic Imbalances
  • Osteomalacia
    • Bones are inadequately mineralized causing softened, weakened bones
    • Main symptom is pain when weight is put on the affected bone
    • Caused by insufficient calcium in the diet, or by vitamin D deficiency
homeostatic imbalances199
Homeostatic Imbalances
  • Rickets
    • Bones of children are inadequately mineralized causing softened, weakened bones
    • Bowed legs and deformities of the pelvis, skull, and rib cage are common
    • Caused by insufficient calcium in the diet, or by vitamin D deficiency
homeostatic imbalances200
Homeostatic Imbalances
  • Osteoporosis
    • Group of diseases in which bone reabsorption outpaces bone deposit
    • Spongy bone of the spine is most vulnerable
    • Occurs most often in postmenopausal women
    • Bones become so fragile that sneezing or stepping off a curb can cause fractures
osteoporosis treatment
Osteoporosis: Treatment
  • Calcium and vitamin D supplements
  • Increased weight-bearing exercise
  • Hormone (estrogen) replacement therapy (HRT) slows bone loss
  • Natural progesterone cream prompts new bone growth
  • Statins increase bone mineral density
paget s disease
Paget’s Disease
  • Characterized by excessive bone formation and breakdown
  • Pagetic bone with an excessively high ratio of woven to compact bone is formed
  • Pagetic bone, along with reduced mineralization, causes spotty weakening of bone
  • Osteoclast activity wanes, but osteoblast activity continues to work
paget s disease203
Paget’s Disease
  • Usually localized in the spine, pelvis, femur, and skull
  • Unknown cause (possibly viral)
  • Treatment includes the drugs Didronate and Fosamax
developmental aspects of bones
Developmental Aspects of Bones
  • Mesoderm gives rise to embryonic mesenchymal cells, which produce membranes and cartilages that form the embryonic skeleton
  • The embryonic skeleton ossifies in a predictable timetable that allows fetal age to be easily determined from sonograms
  • At birth, most long bones are well ossified (except for their epiphyses)
developmental aspects of bones205
Developmental Aspects of Bones
  • By age 25, nearly all bones are completely ossified
  • In old age, bone reabsorption predominates
  • A single gene that codes for vitamin D docking determines both the tendency to accumulate bone mass early in life, and the risk for osteoporosis later in life
7. Bones store minerals.
    • a. Calcium and phosphate needed to form strong bones.
      • 1. Found in:
        • Milk
        • Yogurt
        • Cheese
        • Lettuce
        • Spinach
        • Leafy vegetables
8. Bones can become more brittle with age: osteoporosis. Caused by loss of bone volume and content.