EDUCATION“The purpose of education is to replace an empty mind with an

open one.”-Malcolm S. Forbes

CHAPTER 6The Skeletal System

Functions of Bone __________________________________________

It provides a framework for the body and gives it shape.

It supports and protects organs from injury. _______________________________________

It provides a place for muscles, tendons, ligaments and tendons of the body to attach.

It helps make movement possible. ____________________________

It stores minerals (Calcium) _______________________________

It provides a place for hematopoeisis

Bone Structure Two main types of bone:

_________________________ Bone Light and spongy inner layer of bone. Consists of tiny spicules with bone

marrow between.

_________________________ Bone Heavy and dense outer layer of all

bones Composed of haversian systems

(small units of bone tissue)

Bone Structure 3 types of bone cells.

____________________- cells that secrete the matrix of bone

____________________- cells that have been trapped in the matrix they have created

_____________________- cells that remodel bone by eating it away from places it is not needed.

______________________- covering of bone

______________________- membrane that lines the hollow interior surface of bones.

Bone Cells Osteoblasts

Cells that form bone.

Osteocytes Osteoblasts that are no

longer active & trapped inside matrix of osseous material.

Can revert back to osteoblasts

Osteoclasts Eat bone away. Are the remodelers of bone Withdraw calcium when

needed from bone

Haversian Systems Concentric layers of ossified bone matrix

arranged around a central Haversian canal

Blood Supply to Bone Tiny vessels penetrate the periosteum. _________________________- tiny channels

in the bone matrix that vessels pass through. Are at right angles to Haversian canals

_________________________- Where large vessels enter the bone. Carry blood into and out of bone marrow. Can be mistaken for fracture on radiographs.

NUTRIENT FORAMINA

DIAPHYSIS – the shaft of long bonesEPIPHYSIS – the ends of long bones

Bone Formation

Bone is formed in 2 ways: ____________________________ ____________________________

Bone formation and growth is stimulated by ____________________(GH) from the anterior pituitary (adenohypophysis) gland in the brain.

Endochondral Bone FormationEndochondral Bone formation

Cartilage to bone formation How most bones develop Starts in the ______________________ -

________________ in the diaphysis (shaft) of long bones are gradually replaced by bone.There are ________________ that develop in epiphysis (ends) of bones

Growth plates Located between ________________and

___________________ Sites of creation of new bone that allows bone to

lengthen as animal grows. Cartilage is created on epiphyseal side while bone is

created on diaphyseal side. When bone reaches full length, all

cartilage is replaced by bone and plates “close”.

Remodeling may take place but bone will not get any longer.

Young animals may have epiphyseal fractures because this area is weaker than rest of bone.

Intramembranous Bone Formation

Occurs only in _____________________bones Bone forms directly from _____________

with no cartilage intermediary.

Bone Shapes Long Bones Short Bones Flat Bones Irregular

Bones

Long Bones Longer than they are wide. The ends of the bones are

called _________________________ There is both a _________

epiphysis and a _____________ epiphysis

Main part of bone is the shaft or _______________ which is composed of compact bone.

EXAMPLES: _____________________________________________________________

Short Bones Shaped like cubes. Have core of _________________bone

covered by _____________________ bone. EXAMPLES: _____________________________

Flat Bones Thin and flat bones Consists of two layers of ______________

bone separated by _________________bone. EXAMPLES:

____________________________________________________________

Irregular Bones Miscellaneous

bones that do not fit into another category.

May have characteristics of more than one category.

EXAMPLES:________________________________________

_____________ - is largest sesamoid bone in body.

Bone Marrow Fills the spaces within center of bones Has two types:

_______________ bone marrow ________________________- the process of

forming new blood cells. Majority of bone marrow in young animals

but less in older animals __________________ bone marrow

Consists primarily of __________________ connective tissue.

Common type of marrow in adult animals Does not produce blood cells but can revert

to red marrow if needed.

Common Bone Features ___________________________

Joint surfaces where bones come in contact with each other to form joints.

Consists of: Condyles Head Facet

Covered by articular cartilage Composed of what type of cartilage?

Common Bone Features: Condyle Large, round articular surface. Major condyle is located on end of

humerus and femur. Also located in skull.

Common Bone Features: Head

Somewhat spherical articular surface on the proximal end of a long bone.

Found on humerus, femur and rib. Head is usually joined with rest of bone

by a neck.

Femoral Head Ostectomy (FHO)

Head of femur is removed in cases of trauma or severe arthritis.

A “false joint” forms which gives more comfort to the patient.

Femoral Head Ostectomy

Common Bone Features: Facet

A flat articular surface. Found in carpal and tarsal bones as well

as in vertebrae, radius and ulna.

Common Bone Features: Processes All projections of a bone. Heads and condyles are considered to be

processes. Tendons may attach to processes

Common BoneFeatures: Holes and Depressed Areas

__________________: A hole in bone. Usually allow the passage of nerve or blood

vessel. May exist simply to lighten structure

Example: pelvis has the ____________________

______________: A depressed or sunken area on the surface of a bone. Usually occupied by muscles or tendons.

Types of Skeletons Bones of head and trunk are

_______________________________Skeleton

Bones of limbs and appendages are ____________________________ Skeleton.

Some animals may have __________________- bones formed in the viscera or soft organs.

Axial Skeleton: bones of head & trunk Skull Hyoid bone Spinal column Ribs Sternum

Skull Usually consists of 37 or 38 separate bones Most skull bones joined by _________________ Mandible is connected to skull by a

______________(TMJ)

SkullExternal bones: Frontal bones (2) Occipital bones (1) Parietal bones (2) Temporal bones (2) Incisive (2 ) Nasal (2) Maxillary (2) Zygomatic (2) Mandible (2) Palatine (2) Turbinates (2)

Skull Bones Continued Categorized by:

Bones of Cranium Bones of the ear Bones of the face

Bones of the Cranium Cranium-portion of skull that surrounds

the brain. External Bones of Cranium:

Frontal Bones (2) Interparietal Bones (2) Occipital Bone (1) Parietal Bones (2) Temporal Bones (2)

Internal Bones of Cranium: Ethmoid Bone (1) Sphenoid Bone (1)

External Bones of Cranium

Occipital Bone Forms caudoventral portion or base of

skull, most caudal skull bone. Important because:

Where spinal cord exits skull Skull bone that articulates with first cervical

(neck) vertebrae. ______________________is in center of

occipital bone. Occipital Condyles are on either side of

foramen magnum

Interparietal Bones Small bones located on dorsal midline

between occipital and parietal bones Clearly visible in young animals, may

fuse together in older animals.

Parietal Bones Form the lateral walls of the cranium Well developed in dogs, cats and

humans, but relatively small in horses and cattle.

Temporal Bones

Located ventral to the Parietal bones

Form walls of the cranium Contain middle and inner ear

structures Form

________________________(TMJ’s) with the mandible (Lower jaw)