Location and Basic Structure

Lecture 8: Introduction to Bones

Cartilage

· Location and basic structure

o Found throughout adult body

o Ear and epiglottis

o Articular cartilage and coastal cartilage

o Intervertebral discs and pubic symphysis

· Where do you find each type of cartilage?

o Is abundant in embryo

o Is surrounded by perichondrium

o Consists primarily of water

o Resilient tissue springs back to original shape.

Types

· Hyaline cartilage (glassy)

o Most abundant cartilage

o Provides support through flexibility

· Elastic cartilage

o Contains many elastic fibers

o Able to tolerate repeated bending

· Fibrocartilage

o Resists strong compression and strong tension

o An intermediate between hyaline and elastic cartilage.

Growth of Cartilage

· Appositional growth

o Chondroblasts in surrounding

o Perichondrium produce new cartilage

· Interstitial growth

o Chondrocytes within cartilage divide and secrete new matrix

Tissue in Bone

· Bones contain several types of tissues

· Dominated by bone connective tissue

· Contains nervous tissue and blood connective tissue

· Contain cartilage in articular cartilages

· Contains epithelial lining blood vessels

Functions of Bone

· Support – provides hard framework

· Movement – skeletal muscles use bones as levers

· Protections from underlying organs

· Mineral storage – reservoir for important minerals

· Blood-cell formation – bone contains red marrow.

Classification

· Long bones – longer than wide, a shaft plus ends

· Short bones – roughly cube-shaped

· Flat bones – thin and flattened, usually curved

· Irregular bones – various shapes, do not fit into other categories

· Give an example of each type of bones

Gross Anatomy of Bones

· Compact bone – dense outer layer of bone

· Spongy (cancellous) bone – internal network of bones

Structure Typical of Long Bones

· Diaphysis – “shaft” of bone

· Epiphysis – ends of a bone

· Blood vessels – well vascularized

· Medullary cavity – hollow cavity filled yellow marrow

· Membranes

o Periosteum, perforating fibers (Sharpery’s fiber), and endosteum

Structure Typical of Flat Bones

· Flat bones, short bones, and irregular bones

· Contain bone marrow but no marrow cavity

· Diploe

o Internal spongy bone of flat bones

Bone Design and Stress

· Anatomy of a bone reflects stresses

· Compression and tension greatest at external surfaces

Bone Markings

· Pg 132, study, study, study

Chemical Composition of Bones

· 35% organic components

o Composed of cells, fibers, and organic substance

o Collagen – abundant

· 65% inorganic mineral salts

o Primarily calcium phosphate

o Resists compression

Bone Development

· Ossification (osteogenesis) – bone tissue formation

o Membrane bones formed directly from mesenchyme

· Intramembraneous ossification

o Other bone – develop initially from hyaline

· Endochondral Ossification

Endochondral Ossification

· All bones except some bones of the skull and clavicles

· Bones are modeled in hyaline cartilage

· Begins forming late in the 2nd month of embryonic development

· Continues forming until early adult hood.

Anatomy of Epiphyseal Growth Areas

· Older chondrocytes signal surrounding matrix to calcify

· Older chondrocytes then die and disintegrate

o Leaves long trabeculae (spicules) of calcified cartilage on diaphysis side

o Trabeculae are partly eroded by osteoblasts.

· Osteoblasts then cover trabeculae with bone tissue

· Trabeculae finally eaten away from their tips by osteoblasts.

Lecture 9: Introduction to Bones (continued)

Anatomy of Epiphyseal Growth Areas

· In epiphyseal plates of growing bones

o Cartilage is organized for quick, efficient growth

o Cartilage cells form tall stacks

o Chondroblasts at the top of stacks divide quickly

· Pushes the epiphysis away from the diaphysis

· Lengthens the entire long bone

· Older chondrocytes signal surrounding matrix to calcify

· Older chondrocytes then die and disintegrate

o Trabeculae are partly eroded by osteoclasts.

o Osteoblasts then cover trabeculae with bone tissue

o Trabeculae finally eaten away from their tips by osteoclasts.

Postnatal Growth of Endochondral Bones

· During childhood and adolescence

o Bones lengthen entirely by growth of the epiphyseal plates.

o Cartilage is replaced with bone connective tissue as quickly as it grows.

o Epiphyseal plate maintains constant thickness

o Whole bone lengthens

Hormonal Regulation of Bone Growth

· Growth hormone – produced by the pituitary gland.

o Stimulates epiphyseal plates.

· Thyroid hormone – ensures that the skeleton retains proper proportions

· Sex hormones (estrogen and testosterone)

o Promotes bone growth

o Later induces closure of epiphyseal plates.

Postnatal Growth of Endochondral Bones

· As adolescence draws to an end

o Chondroblasts divide less often

o Epiphyseal plate becomes thinner

§ Cartilage stops growing

§ Replaced by bone tissue

o Long bones stop lengthening when diaphysis and epiphysis fuse.

Bone Remodeling

· Bone is dynamic living tissue

· 500mg of calcium may enter or leave the adult skeleton each day.

· Cancellous bone of the skeleton is replaced every 3-4 years.

· Compact bone is replaced every 10 years.

Postnatal Growth of Endochondral Bones

· Growing bones widen as they lengthen

· Osteoblasts – add bone tissue to the external surface of the diaphysis

· Osteoclasts – remove bone from the internal surface of the diaphysis.

· Appositional growth – growth of a bone by addition of bone tissue to it’s surface.

Bone Remodeling

· Bone deposit and removal

o Occurs at periosteal and endosteal surfaces.

§ Peri – around

§ Endo – in

· Bone Remodeling

o Bone deposition – accomplished by osteoblasts

o Reabsorption – accomplished by the osteoclasts.

Osteoblast

· Against cell with many nuclei

· Crawls along bone surfaces

· Breaks down bone tissue

o Secretes concentrated HCl

o Lysosomal enzymes are released.

Repair of Bone Fractures

· Simple and compound fractures

· Treatment by reduction

o Closed reduction – without use of surgery.

o Open reduction – includes surgery and they use traction.

Fracture Classifications

· Simple – still remain under the skin.

· Compound – protrudes skin

· Overcompression will break bones.

Healing

· Hematoma

· Fibrocartilginous

o Blood vessels come into heal bone hyaline cartilage reforms.

· Osteoblasts start to reform the bone and start forming

· Last part…

Types of Fractures

· Comminuted – old bones fractures into more than 2 parts.

· Compressed – under pressure which cracks open bones, especially with osteoporosis.

· Spiral – twist bone with a lot of force.

· Epiphyseal – epiphyseal plate no more fresh cells, dying.

· Depressed – flat bones goes deep and goes down into tissue.

o Hit head the skull would go in instead of out.

· Green stick – seen in children

Disorders of Bones

· Osteoporosis

o Characterized by low bone mass

o Bone reabsorption outpaces bone deposition

o Occurs most often in women after menopause.

o Common in women

§ Menopause – after bone tissue formation slows down and weakens

o Men less common

§ Less active males don’t use the bones so they get weak, lose fluid and then they don’t calcify as much, use them and then they get stronger.

· Osteomalacia

o Occurs in adults

o Bones are inadequately mineralized

· Rickets

o Occurs in children-analogous to osteomalacia

o Malformed bones

· Paget’s disease

o Characterized by excessive rate of bone deposition

· Osteosarcoma

o A form of bone cancer.

Lecture 10: The Skeleton

Skeleton consists of

· Bones, cartilage, joints, and ligaments

· Composed of 206 named bones grouped into two divisions

o Axial skeleton (80)

o Appendicular (126)

Axial Skeleton

· Formed from 80 named bones

· Consists of the skull, vertebral column, and bony thorax

Bone Markings

· Projections that provide attachment for muscles and ligaments

· Projections that help form joints

· Depression and openings for passage of nerves

Skull

· Formed by the cranial facial bones

Cranium

· Serves to

o Enclose the brain

o Provide attachment sites for some head and neck muscles.

The Face

· Facial bones serves to

o Form framework of the face

o Form cavities for the sense organs of sight, taste, and smell

o Provide openings for the passage of air and food

o Hold the teeth in place

o Anchor muscles of the face.

Skull Geography

· Facial bones form anterior aspect

· Cranium is divided into cranial vault and the base

· Internally, prominent bony ridges

Skull contains smaller cavities

· Middle and inner ear cavity – in lateral aspect of the cranial base

· Nasal cavity – lies in and posterior to the nose

· Orbits – house the eyeballs

· Air-filled sinuses – occur in several bones around the nasal cavity.

The Skull contains approximately 85 named openings

· Foramina, canals, fissures

· Provide openings for important structures

o Spinal cord

o Blood vessels serving brain

o 12 pairs of cranial nerves

Cranial Bones

· Paired bones include

o Temporal bases

o Parietal bases

· Unpaired bones

o Frontal, occipital, sphenoid, ethmoid

Frontal Bones

· Forms the forehead and roofs of the orbits

· Forms supercilliary arches

· Internally it contributes to the anterior cranial fossa

· Contains frontal sinuses

Parietal Bones

· Parietal bone form superior and lateral parts of the skull

· Four sutures of the cranium

o Coronal suture – runs in the coronal plane

§ Located where parietal bones meet the frontal bones

o Squamous suture – occurs where each parietal bone meets a temporal bone inferiorly

o Sagittal suture – occurs where right and left parietal bones meet superiorly

o Lambdoid suture – occurs when the parietal bones meet the occipital bone posteriorly

Sutural Bones

· Small bones that occur within sutures

· Irregular in shape, size, and location

· Not all people have sutural bones

Occipital Bones

· Forms the posterior portion of the cranium and cranial base

· Articulates with the temporal bones and parietal bones

· Forms the posterior cranial fossa.

· Foramen magnum located at its basale

· Features and Structures

o Occipital condyles

o Hypoglossal foramen

o External occipital protuberance

o Superior nuchal lines

o Inferior nuchal lines

Temporal Bones

· Lie inferior to the parietal bones

· Form the inferior and lateral portion of the skull

· Term “temporal”

o Comes from Latin word for time

· Specific regions of temporal bones

o Squamous

o Temporal

o Petrous

o Mastoid process

The Sphenoid Bone

· Spans the width of the cranial floor

· Resemble a butterfly or bat

· Consists of a body and three pairs of processes

· Contains 5 important openings

Ethmoid Bones

· Lies between nasal and sphenoid bones

· Forms most of the medial bony region between the nasal cavity and orbits

Facial Bones

· Unpaired Bones

o Mandible, vomer

· Paird bones

o Maxillae, zymphatic bones, nasal bones, lacrimal bones, palantine bones, inferior nasal conchae

Mandible

· The lower jawbone is the largest and strongest facial bone

· Composed of 2 main parts

o Horizontal body

o 2 upright rami

Maxillary Bones

· Articulate with all of the facial bones except the mandible

· Contains maxillary sinuses – largest paranasal sinuses

· Forms part of the inferior formal fissures

Other Bones

· Zymphatic bones – form lateral wall of orbits

· Nasal bones – form bridge of nose

· Lacrimal bones – complete the posterior part of the hand palate

· Vomer – forms the inferior part of the nasal septum

· Inferior nasal conchae – thin, curved bones that project medially from the lateral walls of the nasal cavity

Sinuses – to reduce weight.

Lecture 11: The Axial Skeleton (continued)

Paranasal Sinuses

· Air-filled sinuses are located within

o Frontal bone

o Ethmoid bones

o Sphenoid bones

o Maxillary bones

· Lined with mucous membranes

· Serve to lighten the skull

The Hyoid Bone

· Lies inferior to the mandible

· The only bone with no direct articulation with any other bone

· Acts as a movable base for the tongue

Vertebral Column

· Formed from 26 bones in the adult

· Transmits weight of trunk to the lower limbs

· Surrounds and protects the spinal cord

· Serves as attachment sites for muscles of the neck and back

· Held in place by ligaments

· Anterior and posterior longitudal ligaments

o Ligamentum flavum

Intervertebral Discs

· Cushion – like pads between vertebrae

· Acts as shock absorbers

· Compose about 25% of height of the vertebral column

o Composed of

· Nucleus pulpous and annulus fibrosis

· The gelatinous inner sphere of intervertebral discs

· Enables spine to absorb compressive stresses

Annulus Fibrosis

· An outer collar of ligaments and fibrocartilage

· Contains the nucleus pulpous

· Functions to bind vertebrae together to resist tension on the spine, and absorb compression forces.

Herniated Disc

· May be caused by trauma to the spine

· Aging is also a contributing factor

· Nucleus pulpous loses cushioning properties

· Annulus fibrosis weakens

Regions and Normal Curvatures

· Vertebral column is about 70cm (28 inches)

· Vertebral column is divided into 5 major regions

o Cervical vertebrae

§ 7 vertebrae of the neck region

o Thoracic vertebrae

§ 12 vertebrae of the thoracic region

o Lumbar vertebrae

§ 5 vertebrae of the lower back

o Sacrum

§ Inferior to the lumbar vertebrae

§ Articulates with coxal bones

o Coccyx

§ Most inferior region of the vertebral column

· 4 distinct curvatures give vertebral column an S-shape

o Cervical and lumbar curvature

§ Are concave posteriorly “(“

o Thoracic and sacral curvatures

§ Are convex posteriorly “)”

o Curvatures increase the resilience of the spine

Go to page 171 table 7.2 and the first 4 rows.

Specific Regions of the Spine perform specific functions