Week 3: Osteology and Joints

Question 1

What are the two major parts of the skeletal system and what are their functions?

Answer 1

Axial – supports and proteccs organs of the head, neck and trunk

Appendicular skeleton – bones that anchor the appendages to the axial skeleton

Question 2

What are the main components of the axial skeleton?

Answer 2

The skull, sternum, ribs and vertebral column

Question 3

What are the main components of the appendicular skeleton?

Answer 3

The upper and lower extremeties, the shoulder and pelvic girdle

Question 4

What is bone and what does it consist of?

Answer 4

Organ-calcified, living connective tissue made of:

Intercellular calcified matrix

Collagen fibers

Osteoblasts (build), osteoclasts (crush), osteocytes (mature)

Question 5

What helps remodel bone?

Answer 5

Parathyroid hormone (PTH) (directs osteoclasts to break down bone when not enough Ca2+ is present)

Calcitonin (Ca2+-activated enzyme that “turns on” osteoblast activity)

Estrogen inhibits osteoclasts, which is why post-menopausal women can often get osteoporosis (activated osteoclasts break down bone)

Question 6

What are the two major varieties of bone tissue and what are their relative amounts?

Answer 6

Compact bone – dense, outer shell that makes up 80% of the total bone weight, leads to greater strength and rigidity (but is very heavy) (ex.: humerus)

Spongy bone – less dense, lighter weight bone that makes up remaining 20% of bone, with spicules of bone enclosing cavities containing blood-forming cells (ex.: phalanges)

Question 7

What are the major bones of the skull?

Answer 7

Cranium and mandible

Question 8

What are the major bones of the upper extremity?

Answer 8

The humerus, radius and ulna

Question 9

What are the major bones of the hand?

Answer 9

Carpals (wrist), metacarpals (palm) and phalanges (fingers)

Question 10

What are the major bones of the thorax?

Answer 10

The sternum, ribs, clavicle and scapula

Question 11

What are the major bones of the lower extremity?

Answer 11

The femur, patella, tibia (medial, larger) and fibula (lateral)

Question 12

What are the major bones of the foot?

Answer 12

The tarsals, metatarsals, and phalanges

Question 13

What are the major bones of the pelvis?

Answer 13

The ileum, sacrum, pubis and ischium

Question 14

What are the defining elements of long bone and where are they primarily found? What are some examples?

Answer 14

They are longer than they are wide, with a long shaft and two bulky ends, and are found primarily in the extremities. They are primarily compact bone in the diaphysis, with spongy bone at the epiphyseal ends. Examples include the humerus and femur.

Question 15

What are the defining elements of short bones and where are they primarily found? What are some examples?

Answer 15

Short bone is cuboidal, with a thin outer layer of compact bone and mostly spongy bone in the center. The bones of the wrist and ankle are mostly short bones!

Question 16

What are the defining elements of flat bones and where are they primarily found? What are some examples?

Answer 16

Flat bones are thin, flat sheets of compact bone plates separated by spongy bone. These include the bones of the skull and sternum.

Question 17

What are the defining elements of irregular bones and where are they primarily found? What are some examples?

Answer 17

They are bones that are not either long, short, or flat. They are usually spongy bone covered in a small, compact sheath. These include the bones of the face, vertebral column and pelvis.

Question 18

What are sesamoid bones?

Answer 18

They are round/oval-shaped bones found in an area where a tendon passes over a joint. These areas include the hand, knee, and foot (i.e. the patella). They act to protect the tendon and joint, and to increase their mechanical effect.

Question 19

What is the periosteum?

Answer 19

A membrane that covers the bone and contains blood vessels, lymphatics and pain nerve endings. It is like a “placenta” for the bone that nourishes the bone and keeps it healthy. When you break a bone, nerve stimulation from the periosteum is what causes pain!

Question 20

What is the main function of cartilage?

Answer 20

It supports soft tissues and provides a smooth, gliding surface for bone articulations at joints. It also enables development and growth of long bones.

Question 21

How does the structure of cartilage change based on the amount of stress put on it?

Answer 21

In weightbearing areas, the amount of collagen in cartilage is greatly increased, and the cartilage is less flexible.

In areas of less stress, there are fewer collagen fibers and many more elastic fibers.

Question 22

What is a joint?

Answer 22

A site where two skeletal elements come together (they don’t have to move)–elbows, teeth meeting the mandible, and ankles all represent joints

1) Skeletal elements separated by a cavity (synovial joint) tend to move
2) Skeletal elements held together by connective tissue tend NOT to move

Question 23

What are the shock-absorptive elements of synovial joints?

Answer 23

Hyaline cartilage at the ends of bones acts as a shock absorber

Synovial membranes filled with synovial fluid act like a water balloon separating your fingers if you try to push them through–reduce friction and force on the bones

A fibrous joint capsule holds the synovial membrane and bones in place/together

Question 24

What is the main component of synovial fluid?

Answer 24

Proteoglycans

Question 25

What are the types of joints?

Answer 25

Plane

Hinge

Pivot

Condylar

Saddle

Ball and socket

Question 27

What are the main movements of joints?

Answer 27

Uniaxial

Biaxial

Multi-axial

Question 28

What occurs at a plane joint?

Answer 28

Sliding or gliding when one bone moves over the surface of another–not much movement can occur here

Ex.: tibiofibular, intertarsal, intercarpal, sternoclavicular

Question 29

What occurs at a hinge joint?

Answer 29

Movement around one axis that passes transversely through the joint–permits flexion and extension, for example.

Ex.: Humeroulnar joint (elbow)

Question 30

What occurs at a pivotal joint?

Answer 30

Allows movement around one axis that passes longitudinally along the shaft of the bone. It permits rotation.

Ex.: atlanto-axial joint of the upper cervival region, which allows us to turn our heads

Question 31

What occurs at an ellipsoidal joint?

Answer 31

Allows movement around two axes that are at right angles to one another (like a mortar and pestle), permittingn flexion, extension, abduction, adduction and circumduction

Ex.: wrist, condyloid joint of fingers

Question 32

What occurs at a saddle joint?

Answer 32

Saddle joints allow movement around two axes that are at right angles to each other, somewhat like an ellipsoidal joint. The articular surfaces are saddle-shaped (almost like kidneys), and permit flexion, extension, ab/adduction and circumduction.

Ex.: carpometacarpal joint of thumb, where thumb meets the hand

Question 33

What occurs at a ball and socket joint?

Answer 33

Allows movement around mulitiple axes, permits flexion, extension, ab/adduction, circumduction and rotation. These joints are not well-protected and can be damaged easily.

Ex.: hip and shoulder joints

Question 34

What are solid joints? What are some examples?

Answer 34

Solid joints are connections between skeletal elements where the adjacent surfaces are linked together by either fibrous connective tissue or by cartilage–movement is usually very restricted. These are called synarthroses.

Ex.: tibiofibular joint, radioulnar joint

Question 35

What are sutures and where are they found?

Answer 35

Only found in the skull, involve adjacent bones linked by a thin layer of connective tissue.

Question 36

What are gomphoses and where are they found?

Answer 36

They are the connection points between teeth and adjacent bones, where short collagen tissue fibers run between the rooth of the tooth and the bony socket. This has a “peg and socket” structure.

Question 37

What are syndesmoses and where are they found?

Answer 37

Syndesmoses are where two adjacent bones are linked by a ligament, such as the radius and ulna. The ligamentum flavum connects adjacent vertebral laminae.

Question 38

What are cartilagionous joints? What are the two kinds?

Answer 38

Cartilaginous joints are a kind of solid joint that connect skeletal elements by cartilage. Examples are intervertebral discs and the pubic symphysis.

There are (1) synchondroses, which connect two ossification centers in one developing bone and (2) symphyses which connect two separate, fully ossified centers

Question 39

What occurs at a synchondroses and what are some examples?

Answer 39

Synchondroses are primary carilaginous joints, which connect two ossification centers in the same developing bone.

Ex.: ribs, and the long bones of the humerus and femur

Question 40

What occurs at symphyses and what are some examples?

Answer 40

Symphyses connect two separate but fully ossified bone centers, with cartilage between the two ossifies elements. These usually occur at the midline and include the intervertebral discs.