Dr. Bruce Forciea

This presentation will examine the skeletal system. We will start by classifying bones.

Bones can be classified according to shape:

Long Bones

Short Bones

Irregular Bones

Sesamoid bones

Let’s look at the parts of a long bone.

Here is an example of a long bone (femur). The proximal and distal ends are known as epiphyses and the middle or shaft portion is the diaphysis. There are also processes protruding from the bone where muscles and ligaments attach.

epiphysis

epiphysis

diaphysis

epiphysis

diaphysis

epiphysis

process

Long bones have a long longitudinal axis and are tubular. At the ends of the bones are the epiphyses.

The epiphysis is covered with hyaline cartilage and forms a joint with another bone. It also contains the growth area known as the epiphyseal plate. If the plate is fractured it can hinder growth of the bone.

The epiphysis contains cancellous or spongy bone. This makes the epiphysis strong yet light in weight.

The diaphysis is hollow and contains the marrow. It also contains a type of bone known as compact bone which is very dense.

The hollow portion is called the medullary cavity.

Bones are covered by a fibrous vascular membrane called a periosteum. Blunt trauma to this area can cause a periosteal contusion or bone bruise that takes a long time to heal.

Spongy trabeculated bone

Compact bone

Forms medullary cavity (covered with endosteum and filled with marrow)

Compact bone is well organized. The structural units are called Haversian systems or osteons.

Here is an example of a Haversian system. There is a central canal containing blood vessels and nerve fibers. Bone deposits around the central canal in concentric rings called lamellae.

Central canal

Lamellae

The osteocytes wall themselves off in spaces called lacunae.

Osteocyte in lacunae

There is a communicating canal called a Volksmann’s canal between the central canal and other osteons.

Volksmann’s canal

The osteocytes are connected to the bony matrix via small canaliculi.

canaliculi

Haversian systems are oriented longitudinally in the long bones along the lines of force.

Spongy bone is organized a different way. Spongy bone is often called trabeculated bone. Osteocytes are located in trabeculae and get nutrients via diffusion.

Next we’ll look at how bone is formed. There are 2 basic processes. One for flat bones called intramembraneous bones and one for tubular bones called endochondral bones.

We’ll first look at intramembranous bone formation called:

Intramembraneous ossification.

Intramembraneous bones develop from sheet-like layers of connective tissue. The process is relatively simple in that bone forming cells called osteoblasts form bone in all directions. The ossification centers then connect to form the flat bone.

Once the osteoblast is finished it walls itself off in a lacuna. It is then called a mature osteocyte.

osteoblast

osteoblast

New bone formation in all directions

osteoblast

New bone formation in all directions

osteoblast

New bone formation in all directions

osteoblast

New bone formation in all directions

When osteoblast fully surrounded by matrix then it is called an osteocyte.

Endochondral bone formation is different from intramembraneous ossification.

In endochondral ossification bone grows from a cartilage model or template.

Hyaline cartilage model

Hyaline cartilage model

Periosteum develops

Hyaline cartilage model

Periosteum develops

Primary ossification center

Blood vessel

Hyaline cartilage model

Periosteum develops

Primary ossification center

Secondary ossification center

Medullary cavity

The epiphyseal plate is located between the epiphysis and diaphysis.

Contains 4 layers.◦ Resting layer (inactive)◦ Active cartilage forming layer◦ Older cell layer from second layer◦ Dead cell layer

Bone lengthens as long as cartilagenous cells of epiphyseal layer are active.

Bone growth stops when epiphyseal and diaphyseal ossification centers meet.

Nearly all bone growth stops at ages 23-25 years.

Bone growth requires a supply of nutrients. The following slides will examine some factors that affect bone growth.

Vit D deficiency◦ Rickets – children◦ Osteomalacia – adults◦ Vit D found in milk (fortified)◦ Vit D produced from UV rays from sun activating

dehydrocholesterol.

Vit A needed for the cells◦ Osteoblastic activity◦ Osteoclastic activity

Vit C◦ Collagen synthesis

Growth hormone◦ Stimulates division of cartilage cells in epiphyseal

plate.

Male and female sex hormones◦ Stimulate ossification of epiphyseal plates and

stop bone lengthening. Physical stress also affects bone growth as

bone grows along the lines of force to dissipate stress.

The following slide will present some information regarding the function of bones.

Support and Protection Body movement Formation of blood cells

◦ Red marrow Red and white blood cells and platelets

◦ Yellow marrow Contains fat (inactive in blood cell formation)

Storage of inorganic salts◦ Hydroxyapatite cyrstals (calcium phosphate)

Osteoclasts break down bone to release calcium salts into bloodstream.

Bone can become injured. A common kind of injury to bone is a fracture.

There are several general categories of fractures.

Fractures heal by forming a blood clot called a hematoma.

The hematoma develops special granulated tissue that contains fibrin (an insoluble protein), inflammatory cells, fibroblasts and cartilage and bone-forming cells.

Osteoblasts (bone-forming cells) produce a bony callus that unites the damaged ends of the bone.

Blood forms hematoma Spongy bone forms in area of blood vessels

and fibrocartilage forms in distal to blood vessels.

Bony callus replaces cartilage Osteoclasts remove excess bony tissue and

restore structure.

Now that we have looked at bone formation and repair it is time to learn some of the bones and bony structures.

We will be learning the names of a number of bones as well as the names of some of the processes.

Bones contain a number of bumps, holes and grooves so that ligaments and tendons can attach and vessels and nerves can enter and exit a bone.

It is important to stick with learning the structures in your lab structure list.

We will come across a number of bony landmarks, but before we do here are some definitions:

Tubercle---a small, knoblike process Tuberosity—a knoblike process larger than a

tubercle Trochanter—a large process Styloid process—a pointed process Suture—an interlocking union between 2 bones Foramen—an opening in a bone (usually a

passageway for vessels) Sinus—a cavity within bone Condyle—a rounded process (usually articulates

with another bone)

The skeletal system is divided into the axial and appendicular skeletons. The axial skeleton consists of the skull, spinal column, ribs, sternum and sacrum. The appendicular skeleton consists of the upper and lower extremities.

Important features◦ Occipital bone

Foramen magnum (opening through which spinal cord passes).

◦ Temporal bones Contain external auditory meatus (ear passage). Mastoid process

Sphenoid◦ Sella turcica (pituitary gland)◦ Contains sphenoidal sinuses

Ethmoid bone◦ Cribriform plates (part of roof of nasal cavity)◦ Ethmoid sinuses◦ Crista galli (brain membrane attachment point)

Skull sutures◦ Coronal◦ Squamosal◦ lambdoidal

Maxillary Palatine Zygomatic Lacrimal Nasal Vomer Inferior, superior, middle nasal conchae Mandible

Maxillary bones◦ Maxillary sinuses

Palatine bones◦ Located behind maxilla◦ Form posterior portion of hard palate.

Zygomatic bones◦ Have a temporal process that connects with

zygomatic bone (zygomatic arch). Lacrimal bones

◦ Contain channel that carries tears. Mandible

◦ Mandibular condyle (TMJ)◦ Coronoid process◦ Mandibular foramen (blood vessels and nerve

that innervates lower teeth). ◦ Mental foramen (blood vessels and nerve that

supply chin and lower lip).

Frontal bone

Nasal bones

sphenoid

zygomatic

maxilla

mandible

lacrimal

Infraorbital foramen

Mental foramen

parietal

occipital

temporal

Mastoid process

TMJCoronoid process

frontal

sphenoid

Temporal part of zygomatic

maxilla

mandible

Mental foramen

Sagittal suture

Parietal bone

Lambdoidal suture

occiput

Fontanels –membranous areas that later form sutures. ◦ Posterior fontanel closes at 2 months.◦ Sphenoidal fontanel closes at 3 mos. ◦ Mastoidal fontanel closes at 1st yr. ◦ Anterior fontanel closes at middle to end of 2nd yr.

(as baby becomes more mobile)

Vertbra◦ 7 cervical (C1-7)◦ 12 thoracic (T1-12)◦ 5 lumbar (L1-5)◦ Sacrum (S1--)◦ coccyx

Curves◦ Cervical (lordosis)

secondary◦ Thoracic (kyphosis)

primary◦ Lumbar (lordosis)

secondary◦ Pelvic (kyphosis)

primary

cervical

cervical

thoracic

cervical

thoracic

lumbar

cervical

thoracic

lumbar

pelvic

Typical vertebra◦ Body◦ Pedicles◦ Lamina◦ Transverse processes◦ Spinous process◦ Facets

Learn more about the vertebral column at:

http://www.wisc-online.com/objects/index.asp?objID=AP12104

Cervical◦ Atlas (ringlike)◦ Axis (dens)◦ C2-7 has bifid spinous process◦ Transverse foramen (vertebral arteries)

Transverse foramen

Transverse process

Fovea dentis

Superior articular facet

Inferior articular facet

dens

Transverse process

lamina

Inferior articulating facet

Superior articulating facet

Bifid spinous process

Transverse process

Inferior articulating facet

body

Superior articulating facet

Transverse foramen

Spinous process

Spinous process

lamina

Transverse process

facet

pedicle

body

body

pedicle

Transverse process

facet

Vertebral foramen

Transverse

process

lamina

Spinous process

Ilium—ischium—pubis—sacrum Sacrum

◦ Sacroiliac joints (auricular surface + ilium)◦ Sacral promontory (body of first sacral vertebra)◦ Sacral canal –sacral hiatus (hollow section –

rudimentary spinal canal)◦ Sacral foramina (on ventral side)

Passageway for nerves and blood vessels

Coccyx◦ Rudimentary tailbone◦ 4 sacral vertebrae fused by age 25◦ Ligaments fuse to sacral hiatus

Pelvic Girdle◦ Coxae

Ilium—ischium—pubis Ilium

ASIS PSIS Iliac crest Greater sciatic notch

Pelvic Girdle◦ Coxae

Ilium—ischium—pubis Ischium

Ischial tuberosity (sit bones) Ischial spine

Pubis Symphysis pubis Obturator foramen

Iliac crest

Ischial tuberosity

Ischial spine

coccyx

PSIS

sacrum

Obturator foramen

ASIS

Pubic tubercle

Symphysis pubis

Iliac crest

Ischial tuberosity

pubis

Greater pelvis◦ Pelvic brim

From sacral promontory to symphysis pubis◦ Pelvic brim separates greater (false) pelvis from

lesser (true) pelvis. Infant passes through lesser pelvis at childbirth

Iliac bones more flared in female pelvis. Angle of pubic arch greater in female Greater distance between ischial spines and

ischial tuberosities. Sacral curvature shorter and flatter.

Ribs—thoracic vert.—sternum—costal cartilages.

Ribs◦ Typically 12 pair◦ R1-R7 = true ribs

Articulate at thoracic vertebra to sternum via costal cartilage.

◦ R8-R12 = false ribs Do not articulate directly anteriorly with sternum

False ribs◦ Usually R8-R10 articulate anteriorly with

costosternal cartilage of R7.◦ R11-R12 are floating (no anterior articulation)

Sternum = 3 parts◦ Manubrium

Articulates with clavicles◦ Body◦ Xiphoid process

head

neck

tubercle

shaft

body

manubrium

xiphoid

True ribs

Clavicles◦ Articulate with manubrium of sternum

Scapulae◦ Acromion process◦ Coracoid process◦ Glenoid cavity (fossa)◦ Scapular notch◦ Spine of scapula

acromion

coracoid

glenoid

Lateral border

Medial border

acromion

Glenoid fossa

spine

spine

Humerus Radius Ulna Carpals Metacarpals Phalanges

Humerus◦ Head

Articulates with scapula at glenoid fossa◦ Greater tubercle

On lateral side◦ Lesser tubercle

On medial side◦ Intertubercular groove

Tendon of bicepts brachii passes through◦ Deltoid tuberosity

Attachment for deltoid muscle◦ Capitulum (lateral side)

Articulates with radius◦ Trochlea (medial side)

Articulates with ulna

Humerus◦ Coronoid fossa

Receives coronoid process of ulna when elbow bends.

◦ Olecranon fossa Receives olecranon process of ulna when elbow

bends.

head

Lesser tubercle

Medial epicondyle

trochlea

Greater tubercle

Intertubercular groove

Lateral epicondyle

capitulum

head

trochlea

Head◦ Articulates with capitulum of humerus

Radial tuberosity◦ Bicepts brachii muscle attachment

radiusulna

Radial head

Radial tuberosity

Styloid process

Trochlear notch

Coronoid process

Styloid process

Olecranon process of ulna

Radial head

Radial tuberosity

Carpals—metacarpals—phalanges Carpals

◦ Trapezium◦ Trapezoid◦ Capitate◦ Hamate◦ Scaphoid◦ Lunate◦ Triquetrum◦ pisiform

Carpals—metacarpals—phalanges Metacarpals

◦ Number = 5◦ Form the palm of the hand

Phalanges◦ Proximal◦ Middle ◦ distal

phalanges

metacarpals

carpals

hamate

pisiform

triquetrum

lunate

trapezium

trapezoid

capitate

scaphoid

Femur Tibia Fibula Tarsals—metatarsals--phalanges

Femur◦ Longest bone in body◦ Fovea capitus (lig attachment to hip)◦ Greater trochanter◦ Lesser trochanter◦ Linea aspera◦ Medial epicondyle◦ Lateral epicondyle

Tibia◦ Medial and lateral condyles◦ Tibial tuberosity (insertion of patellar tendon)◦ Medial malleolus

Fibula◦ Head◦ Lateral malleolus

headneck

Lesser trochanter

Medial condyle

Greater trochanter

Lateral condyle

Linea aspera

Fibula Tibia

head

Lateral

malleolus

Medial condyle

Tibial tuberosity

Medial malleolus

talus

navicular

Intermediate cunneiformMedial cunneiform

cuboid Lateral cunneiform

calcaneus

See more bones and landmarks at:

http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/learnem/bones/main_bone.htm